Title of Invention	A TUBE FITTING FOR A TUBE END AND A METHOD OF ASSEMBLING A TUBE FITTING
Abstract	The present invention relates to a tube fitting 50 for a tube end 13, comprising: a first coupling 56 member; a second coupling member 52 joined with said first coupling member 56; a tube g!ipping device 80 disposed between said first coupling member 56 and said second coupling member 52 such that assembly of said first coupling member 56 with said second coupling member to a pulled-up condition causes said tube gripping device 80 to grip and seal the tube end 13; wherein the first coupling member 56 engages an internal surface 75 of the second coupling member 52 to provide an indication of completed pull-up. The present invention also relates to a method of assembling a tube fitting.

Title of Invention

A TUBE FITTING FOR A TUBE END AND A METHOD OF ASSEMBLING A TUBE FITTING

Abstract

The present invention relates to a tube fitting 50 for a tube end 13, comprising: a first coupling 56 member; a second coupling member 52 joined with said first coupling member 56; a tube g!ipping device 80 disposed between said first coupling member 56 and said second coupling member 52 such that assembly of said first coupling member 56 with said second coupling member to a pulled-up condition causes said tube gripping device 80 to grip and seal the tube end 13; wherein the first coupling member 56 engages an internal surface 75 of the second coupling member 52 to provide an indication of completed pull-up. The present invention also relates to a method of assembling a tube fitting.

Full Text	TLW: nTTKNG WITH SEPARABLE TUBE GRIPPING DEVICE Related Applicatioas Thi::. application claims the benefit of United States Provisional pateiit application icii£tl no. 60/26(3,735 filed on February 6, 2001 for TOBE HTTING WI'IH INTEGRAI. NUT A]M> FEilltULK. TOd senal LO. 60/329,943 filed in October 17, 2002 for TUBE fm'rMG, \iic sn :ii'e dis Technical Field Of The Invontioa The subject invention is iienerally directed to the arc of rube fittings. More pd.rL:.cular.y, the invention is tirccted to a flareless tube fitting that uses a tube gripping elcmer.t ihiii is iniiially joined to csie of the coupLng ekineats and s?arates therefrom during assembly onto a tube end. Backarouad of tbelnveutioQ Tube fit;ings ure used to join or coxmect a tube eid to another member, whether that other member be another tube end such as through T-fittings and elbow fittings, for example, or a devitx that nucds to be in fluid communication with the tube end, such as for example, a vjtlve. Ai. used herein tlie terras 'rube' and 'tubing" are inteiided to include but not be limited to pioe as veil. Aziy tube fittbig must accomplish two important functions within the pressure, tem?eran.ie and vibration criteria tliat tl;e tube fitting is designed to meet. Fir^t, the tube fitting mat grip the tube end so as to prevent loss of seal or tube blow out. Secondly, the tube fitting misx maintain u primary seiil against lca!ca[je. The require-meiit that a tube fitting accomplisri th2se two fimction.3 has b A flarelcss tube fitting generally refers to a type of tube fitting in which the tube er:d remains subs.:ancially tubular, in contrast to a flared tube fitting in which the tube end is outwardly flared c^ver a fitting component. Flaied tube end;> ar« commonly encountered in use w.Ui plastic tubing and plastic tube fittings. The present invention is not primarily directed lo piastic tubing or cube fittings because such fittings have significantly difiercnt challenges and; material properlie:> that affect the abilit>' of the fitting to both grip the tube and provide tn adequate sea'. Hov/cvtr. some of the aspects of tivc inveiition may apply to non-met£i tuoe fitt]jij;s, particularly the separable tube gripping element aspect. Tube fittings that arc intended for U£c with staiol^ss j;tcel and otJier luetal tubing, foi c.\aJTiple. are particularly challeaging to desiip; m order to ncliieve the desired tube grip and se:ii rdnctior.s. Tai;: ariies from the natuie of stainless stcol which, ir, toms of t>pical coroTiitrrcially avaii;ibie tubing material, is a vcr/ hard matcri^il, usually on tlie order of up to 200 Vu.ki:T5i. SuduJess stjel ard other metal tubing is alio used for high pressure applications in wliicli \ht tuDing wall thickness is substantid (referred to in the ar?: as "hed\7 walled" tubing). Plcavy wall tubing is difficult to grip because it 15 not only hard but it is also not panicularly ductile. Lo\\ ductility makea it more difficult to deform the tubing plastically so as to achieve a dtt!:iii::d tube jtip. Tube fillings typically include an assembly of; 1) a tube gripping device, often in ♦ the fcrm of a ferrule cr fermles, or a gripping; ri.ng-like stnict\^e, and 2) a pull-up mechanism for causbj! tiie 'rube gripping device to be installed on a tube end $0 as to grip the tube end and provide a seal against leakage. The term "pull-up" simply refers to the operation cf ti£htening xiii ti.be fitting asstimbly so as to complete tx assembly of the fitting onto the t^be end with the dciiinrd tube grip and «ea!. UsuiiUy a tube titling is lirst assembled in a 'finger tight" condition and then a wr3n:h or other suit;;ble tool is used to tigliten or 'pull up" the lilting to its final initial and cccnjilctc asiiembled condition. The pull up mechanism most commonly U5ed is a threaded co--ui;ction cf a fexnaie threaded nut component and a male thr'^aikd body component, with the tube gripping dc\r;ce: being acted upon by ir.ese two components as they are threaded and tignt:;ned to£;ether. The body includes a tube end receiving bore witia ^n angled camming surface at th'ij outer i5onion of that bore. The most commonly used canuning surfaces arc frusto-conical such tliat the- term "camming angle' refers to the cone angle of the camming surface relative to the tube end longitudinal axis or outer surface. The tube end is axially inserted into the body bore ajid extends past the fcusto-conical caitiming surface. Th« gripping device is slipped onto tilt: tube end and tlie nut is partially threaded onto the body to the fmger tight position such that the tabs gripping dei'ice capl"ured axially between the camming surface and the nut. The nut tyi)ic ally in:;ludes :in inward shoulder that diivcs the tube gnpping device into engagement with the .-Lngled :ammin^; surface on the body as the nut and bady components are threadably ti\|!httin.ed together. The angled camming surface imparts a radial compression to the tube giip{:irig de\icc, forcing the tube gripping dwce into a gripping engagement with the tube end. Tl'ie :\i':)e gripping device typically is to fom a seal agaimt tlict outer s;jrface of the tubing and also .igaiast the angled camming surface. The most conunonly used tube gripping devices in stainless steel tube fittings today (the most commonly used are fcnalc-t>pc tube fittings) acliieve tube grip by causing a frcnl: or no.sd portion of the tube giipping device to bite iato the tube end outer surface As used h Over the years thire have been numerou.-^ tube fining designs that do net rely on a 'l:it." xypt actiont but rather me-.-ely radially compress the tube gripping device agaiiisi tliC tubing oL.te: .surface, some with-the effect of indenting into the tubing witliout creaung a bite. These dfsiijns are not suitable for higli prcssiue stainless steel tube fittings. The most common ccniiicrcially available btainlecs; steel tube fittings especially for higji pressure applications have hib-torically been of two radically distinct designs of the rabe gripping device-single ferrule tube ftrtii igs and two ferrule tube fittings. A sii'.gle ferrule tube fitting, as the name iJupUes, uses a single ferrule to accc-niplish both djs tube grip and sea! functions. However, it is becoming increasingly recognized diat thtsc Uvo functions are at odds with each other when designing a tube fitting that c;ai nr^eet a desired nibe grip and seal pcrfcnnance criteria. This is because the design criteria T'leded to {5sure tha the tube fitting achieves an adequate tube grip usually works against the abiltj' of rlie single ferrule to also provide an eCTective seal. Consequently, although prior art single ferrule fitting,? can achieve adequate tube grip ia some casts, this tube grip performance comes at tlie expv.x/er, even in such lower pressure applications single fcrniie seal performance remains less thaj I desired. For single ferrule tube fittir.gs, the biting action is usually associated with the i>nj;le femJe being designed to bow in a L-adially outward direction from the tube wall in the centra., region or mid-portion of tJie single fcnul-s body between rjie front aad back ends thereof. The fi'Ml end of the ff the single ferruli to as to radially compresa tlie back end of the ferrule into a gripping action on tb.e tube end. In some smj'^k fermle designs, the back ead of the ferrule appar^-T.tly is intended to bite Into the tube end. Thti lack end tube grip is sometioies used with the single femile in order to attempt to improve the tubij fitliug's performance under vibration because the back end grip attempts to isolate dovm tube vibratiori from affecting the &ont end tube bite. The US:! of a back end tube grip actually w^orks against the effort to grip the tube em: at the front end of the^cjngle femils. Ideally, the single ferrule sliould be completely in three dimensional comprssiiion between the nut ar;d the canuniDg fturface of the body. Providing a back i:nd grip actually placer, a counter acting tension to the sLngJe fen^ulc that works against the front end compressiou'being used to provide tlie tube grip. Additionally, the outward bowing aci.oi; tends to work against the effort to grip the tube at the firont end of the single ferrule be: aiise, in order to enable the outward bnwir g action, the single fenule requires a lessened mass that ii adjaccm the t)ibe gripping "bite'. The our^^'ard bowing action radially displaces femile mjss CintraJ lo the firrrule body away from the tube end. Consequently, an outwardly bov^ed singk; rerrul In ordtT to achieve an adequate tube grip on stainless steel tubing, single ferrule stainiesis steel tube fitdngs have historically used a rather shallow caiiuning angle of between ten and t^vcnty degrees. This range of angles is refcned lo herdn as '^shallow" only as a term of convtjnicnce in that the angle is rather small, llie shallow camming angle has been used in single ferrule fittin;5S to cbtiun a mechanical advantage because the shallcw angle provides an axially elcn^iated camming surface against which to slide and radially compress the single ferrule front end (0 bite into the tube end outer surface. Hard stainless steel tubing material necessitated this elcn^:ai:ed sliding ca:-nming action in order to be able to get tlie single ferrule to create an adi^qtiate bit: for tube grip. Over the years, the single ferrule ha^ been through hardened or case h£::dened so as to be significantly harder than tcic stainless steel tubing, however, the shallow (famming an?le is stil- used today in such single ferrule fittmgs to obtain a mechanical advantage froni the female slidnj along the camming i-urfacc to produce the "bite" so as to assure an adequ2.te tube gilp. An example of a convnercially available single feirule tube fitting that uses a case: hiLfdened ferrult lijid a shallow camming angle of about twenty degrees is the CPI fitting line available from Pjirker-Hatinifin Corporation. Another exatnple is the EO fitting line avai allc Iron:. Ernitto GmbH that uses a tluough hardened single ferrule and a tuelvs degree rarr^niaj'^angh. In som«: single fertile designs, a non-conical camming surface has b-^en iried wh The sha.llow camming angle and elongated camming surface and axial movement needed 1o achieve an adequate tube grip with a single ferrule fitiing, however, compromises the abi^aty of the single feirule^.Jo achieve the seal function, especially in extreme cnvironnicats and for seiding ^is. This is because the firont end of tlic single fcirule attempts to make the seal againiit the a::iaUy elc^ngated camming surface. The radially outward bowling action causes a lariser portion of the o.itcr surface of the fi^ont end of the single forruJe to come into contact witli the cEiuming surface against which it is being driven, The result necessarily is a l&rger seal suriace area Detween die outer surface of the single ferrule and tlie camming surface. This enhirgcd seal area cauiies an unwanted distribution of the sealing force between the single fenule and tl:.e camming surface, and also creates a larger area for surf2.cc imperfections to allow leaks to cccur. This is particularly a metal to metal seal issue (as contrasted to non-metaJ to non-metal sei/s: for exiraple, in a plastic fitting it is usually desirable to provide an enlarged seal contact arcu because ihemore highly ductile plastic material can better form a. seal between the t>'0 sui:a^:es.) Because historically the single ferrule fitting has used a shallow camming angle to acliie-'e adequate tube grip, the less than optimum seal function is either tolerated as a recognized limitation on the application of the fitting, or additional featuiss have been designed into the sir-;>k ferrule: fitting, most notably attempts to include one or more; elastcmeric seals with ihe sin.jh: ferrule or with which die single ferrule cooperates to provide a better seal with stainless sie.d mbing. See, for example. United States Patent nos. 6,073,976 aind 5,351,993. United States Patent No. 6,073,976 illustrates a t>pical exariple of a single "ferrule" (called a "cutting ring" in thii patent) fitting that attempts to solve the "seal" issue wtJi added elastomeric seal. The 5,.i:l,99£ patent describcr, th= beri'sfits obtained by separating the tube grip and seal f;^ctions m.o two separate components. A commercially available sjid highly succcssfiil two ferrule fitting used for tubing is cDrnmiircially Eivailabic from Swagelok Company, Solon, Ohio and is described in United States Paienx No.^. 6,131,962 iind 3»103,373 both of ^hich arc o^vned in common by tlis a^sigaee oj" iJic piesent iuY^ntion, iht entire disclosures of v/hlth are fully iucorporated herein by veferenctf In this 1:^0 ferrule fitting, the tiibc grip and seal ftmctiona aho are t>cpar?te!y achieved by the i:s2 of tv^o ferrules, The foiv^'ard or &ont fenule piorides an excellent seal even ag^nsc g;:5, and the back or rear ferrule provides in excellent tube grip. The front feuule achieves an excellent seal by camming against a shallow ciimming surface ;mgle s'jch as twenty dcj^rees. Tliis is because the front ferrule doe5 not need to slid'3 exc(;ssively on the canantiug iruirfiice iu order to achieve a lube grip functionv Likewise, the front fcm:l6 is not ca^e hardened because the primary purpose of the front ferrule Is to seal and is not to bit? into \he tub^'Cnd. Thus the relatively "softer" front ferrule achieves an excellent seal, p;;rticulaily again-it gas, even though the body corneal caning surface presents a cammincj ai gtc of i.bout Tiventy degrees. The back ferrule achieves the tube grip fiincidon in the above noted two ferrule aibe fitting. The back femjlc is case hardened to be substan'tially haider than the tube end. The fiDnt end of the back femile cams against a frusto-conical camming surface formed in the back eid of th: front feiiulc. The ostensible angle of this camTning surface is forty-five degrees, but d.ie to the slidini:; mcvernent of the front fermie, the efTectivj camming aiigle is actually a sl^'low jjigle of jibout fifreet. to twenty degrees. Although the effective camming ajigle for the bacx ferrjle is shs-Uow, the bz-ck feirule is not required tc provide a primaiy seal (although it can form secondary cr backup seals). The back femile also docs not exhibit the undcsired bowing a( tion but rather grips the cube end as a fiiuctiou of a raiHaily inward hinging action. As used httein, tl:.e term ^'hinging" refers to a controlled dcforraaticn of the ferrule such that a central region or mid-pordon of the fjmile body undergoes an inwardly radial compression, as distinctly contrasted to a bowing or radially outward displacement. Thus, the effective shallow camming angle not only does not compromise the luting seal capability, it actually substantially enhances tfic overall performance of the tube fitting especially for stainless steel tubing. By using separate ferrules for each to achieve primarily only one of the key rube fitlng fuictions. 'the t^'o ferrule tubs fitting achieves tremendous tube grip and seal functions. Thii prio:: art two ferrule lube fitting thus ha:5 enjoyed tremendou;* commercial success especially ir. tlic art cif stainteiis steel tubing in part due to its performar.c.'; char^cteiisdcs such ai high p/cjiSiire rating on ±t order of 15000 psi, wide temperature rating of cryogenic to 1200 °F and in rr.aiiy applizationii a significant number of renakes (a "remalc;:" r:fers to the loosening and re-Li^X'oing cif a fittiai; after an initial pull-upj. United States Patent No. 3,248,136 iUustratc3 use of a single locking ring a^ copoi'ed to a femj.le, wherein the locking ring acts against a surface having an angle that appears tci be greaUr than rwenty degrees or more, tut the ring doss not appear to plastically deform into the tubing l)ur ratlie: remains elastic so that the ring is designed to retain its original shape after p ilL-up, boil of whi:h are features that are uusuiiable for sta:rJess steel lube fittings of the type coniidered herein. Japanese urtlit>' model pullication 44-29659 illustrates a tightening rin^ tliat cop.jars to be intcnd-rd to have a bowing efl'tct and grip the tube at the front and back ends. The litii'ig does not apptiar to be applicable to stainless steel tubing as th? tube is covered with a resin Attempts have been made to design tube ilttbgs wiih a rjbe gripping element that Si5p;ir:ites during pull-upy to ninclion as a single element tube gripping device. Known designs place the breakaway element on the mule threaded component. Additionally, the known designs eitl-.ei force the tube gjippiag clement &ga:n::t a shallow cainnung surface angle or do not attempt !() create a hibc gripping bite into the tube wall. Thus the prior an designs suffer froni the same limitations as the prior art single ferrule tube fitting designs. M:m;,' applications and uses of the tbcvc-described iwo feirulc SWAGELOK tube f ning do not requi:c such higli pressure, temperature and rcmaki: performance characteristics. 7hc present Lnveati:»n U directed to a new fitting concept that can naeet lower performance cha.-acterisiics without compromising overall fitting intcgritj* and pwfonnance. Summary of the loveptton In accordance with one aspect of ihe invention, a new tube fittmg concept requires usei' assembly of only two components, namely a fitting body and a fitting nut. The nui and body arc adapted to be threadably coupled together by relative rotation therebetween. The nut includes an initially integral Cube gripping clement or fcn-ulc that cooperates with a canwiing surface on tlie body when th? fitting is made-up. The tube gripping clement may be machined with the nut or separately attachird thereto ty any convenient process such as brazing, welding or soldering, fir examph. In the described embodiment tlie tube gripping element is a ring like structure that, after it separates fircm the component to whicli it is attached, operates as a single ferrule. The d(tz:c^ti foitule is radially compressed and plastically deformed against tike tube outer wall to fojT! a seal aiij a tig'at tube grip bite. The detached ferrule also forrn;; a primary seal against the caxr.."niag surf:ice. In one embodment, the fe:niilc includes an outer tapered surface at its front end fomilng a generally narrow Ibe coniact-t}^e sea! against the cacaming surface. Thcs ferrule in cue cnabod.ment i$ designed to have a liingiiig action and to plastic deform during pull-up to cm1:cd tlie nos:e portion into che tubing wall foi: excellent tube grip, and an axially adjacent swage or c:i\'x\ rone that isolates the embedded nose portion from vibration effects. The hinging action . alsc bibs to keep the ferrule outer tapered surface in a generally lin-r contact with tJie camming curiaes. The fitting components, and particularly the separable ferrule, are preferably but not necissianly ci.se hardened. The new fitting is -sspecially useful as a stainless steel and other metai tub? fittings, iUhou}^ the invention is not limited to any particular class of metals. In accordance wi:;) another aspect of the invea-ion, the fitting may include a self-gauging feature to indicate suj;acient pull-up and to prevent excessive tiglUening of the components. In accordance with additional aspects of tlie invention, the camming surface prciile is substantiiilly mc^jfied from prior art single ferrule tube- fitting designs by incorporating a :Ue';rp camimng ajigle in the lange of about thirty-five degrees to about sbcty degrees. The stesp'ir camimng angle produces a better tube grip than prior art single ferrule tube fittings, pajtic'Ularly when ihc ferrule is hardened to be at least about 33 times harder than the tubing maedal Tlie ferrule may also be designed Viith a geometry that facilitates a radially inward hing'ng action during pull-up. This hinging action improves the tube grip and seal as compared to pr.or single ferrule tube fittings. These and other aspects and Stdvantages of the present invention will be apparent to th3s.e skilled in the ait from the following description of the preferred embodiments in view of the accompanying dr^iwings. Brief Description of the Drawings The invention may take physical form in certain parts and arrangements of parts, pref:rred embodiments and a method of which will be describee in detail in this specification and illustrated in the accompanying drawings which form a part hereof, and wherein: FIG, 1 illustrates in half longitudinal cross-section aa exemplary embodiment of a tobe fitting m accordance with the invention in a finger tight position; FIG, 2 illustratef. the embodiment of FIG* 1 in a partially pulled up position; FIG. 3 illustrates the embodiment of FIG. 1 in a completed initial pulled up position; ard FIG* 4 illustrate?} another embodiment of the invention. DETAILED DESCRIPTION Stainlry:- Steel ■SubsaatO; [OOOr llic present invention is applicabb to all types of stsinless steels. As well knc^^'n, stainless steel is a steel which forms a coherent chromium oxide coating when exposed to air. To this er.d, most stainless Steele contain at least about 16 vi.'vi chromium Prefen-id are 3ub Form;3tiim of Metal Oxide Layer [0002; As indicated above, low temperan::re carburization of stainless steel parts, when done usin;; an oxygen containing gas, leaves the cr^rburized s\irface catr>'ing a layer of soot a^ well as a porois., i.e. non-coherer;t, adherent metal oxide layer. Nonnally, this metal oxide layer is compo.sed of chromium oxide, although other metal oxides can be present. In conventional practice, this metal ojtide layer is removed together with or indej^endently of the soot layer which also fcrras. In accordance witlr the present invention, however, this heavy metal oxide layer is left on at least a ponion of the part surfaces, since it has been found that this metal oxide layer sen't^s ai; an ideal anchor for bonding subsequently applied solid lubricants. [0003. The pmicular condition:; under which this metal oxide layer can be fonried are already well kiown in the art, since this formation occurs to a peater or lesser degree during low temperature carburiz£ktion when carbon monoxide or other oxygen containing gas is present in the carbiirizir.g gas. Especially heavy (i.e., thick) metal oxide layers can be obtained by using carbon monoxide as the predominant carton source for carburization. Carburization gases in which c:irbon monoxide accounts for at least about 75%, S5%, 95% or even 100% of the carbon souioe for carburization aie especially interesting. [00041 Othei approaches rhat can be used for fostering tlie formation of this rnetal oxide coating during carburization are small percentages of CO2, H^O, etc. [00051 Normally^ the oxide layer will be about 200 to 400 Angsxroms ttiick, although thinner and thicker layers can also be used so long as they serve to anchor the applied solid lubricant in the manier indicated herein. Ei^jll^;.'r'^ I of So .uLayei [OOOCj RemoA^al ol'tl)? sooi layer which foims during low tenipcramre carbmizauoii can be done in a xnventional manner. For example, washtng the carhurized part aqucou?];/ with ultrasonics will elfectively remove all or substantially all the soot without adversely affecting the metal oxirli layer in any significant way glolid Liibricairs [0007 i In accordance with, the present invention, a solid lubricant is applied to the metal oxide laycj fmned by low temperature carburization. [OOOS i For this puqz'Oise, essenually any solid lubricant can be used. Many such solid lubricants are \^x\l knowTi. Some are particulate in form while other are supplied lai'ger in size. A few exauip^es arc graphite, molybdenum di;;ulfide, tungsten disulfide, UHNIWPE (ultra high mol';ci.hir weight polyetl/v'lene), halogenatod polymers such as PFA, PTFE, PCTFE and the like. Exarapks of comme»'cially available solid lubricants include Dow Corning® 321 Dry Film Lubticmt avdlable from Dow Coming Corporation of Midland, Michigan and Slickote^' Dry Lubt-100 available from Trans Chem Coatings, of Monrovia, California. [0009. These lubricants can be used not combined uith ano':her material, or mixed with another material such as a lesinous carrier or the like. In addition, they can be used in essentially any solid form including powders, gi'anules, pastes and bulk solids. Apolii'a'.ion of Solid Lubricants [OOlO'j The solid lubricants of the present invention can be applied to the metal oxide layer by any standard method such as by hand, sv.ch as by rubbing, by aerosol or air spraying or by autc;n;-.tic eqiipment. Any coating thickness can be used which will provide lubricating prop;riies. Solid hibricant thicio^esses exceeding standard class 2 thread cleaiances are usually not required. [0011] If appropriate, the lubricant can also be heated to enhance its adhesion. For example, some labricarts, especially those supplied ia a resinous binder, can be heated to effect cure of the bindtr. For example, Slickote® Dry Lube 100 can be heated following manufacmier's instrjctions tc> 300"" F for 1 hour, for example. ■ [OOlIIj The present invention can ht \iscd anyv^^here it is dssirabk to enhance the surface slipperiness crf cast* hardened, corrosion resistant stainle::;$ steel parts. Particular examples are nuts, bolts, g [001^ j The present invention finds particular utility in making stainless steel nuts having case harder ed threads lubricated in 'c.ccordance witli the present invention. Because of the lubricant, less pull-up torque h required during tightening as comp£.red to a similar case hardened nut without lubricant. Moreover, this enl)anced lubricating effect is retained longer than a lubricated nut madt in <. conventional manner i.e. by removing the metal oxide layer before applying lubricant because anchors in place even after repeated u5e. thus nuts rr.ade accordance with present invention can wltlistand fitting remakes looscnings and retighfenings of nut without being removed or replaced.> [0014] Although only a few embodiments of the present inv.^,ntion have been described above, it should be appreciated that many modifications can be made wid:out departing from the spirit and scopa of the invention. All such modifications are intended to be mcluded within the scope of the present invention, which is to be limited only by the following claims: DetaileH DgscripUon of the Invention Li accordance then with one aspect of the invention, a tuht; fitting is provided hi!v:.ng a lube gripping device that initia!l> is integral with one of the coupling elements and upon pi..ll'Up scparares i:herefrom to function a, a single ferrule fitting. In the preferred enibodimeat, tbi :ube gTippiii;£ device or feiTule is integrally fomi&i with a female threaded nut and 15 attached th sreto by a frai:.gibk thin web portion that breaks as the femile cnxns initially against a camming surface of tlie r.:ia!.e thccaded component. As a single ftniT.le after separation, the ferrule acts ajjainst tl- e steep canmiing angle surface of a male threaded body- The steep camniJr.g surface ai;gle is particularly advantageou5 when tlie hardness of the tube gripping device has a ratio of at least about 3.3 tinges greater 5Lnd preferably at least 4 times {jrealer to the hardness of the tnbing U3.Uerial. Although a number of aspects of the invention are desciibcd herein as being in':orporalcd into the ^emplary embodiments, such description should not be coashiied in 3 limiting sense. 7or any particular application the various aspects of the invention-may be used as iC'^uircd ji differtint combinations and sub-combinations tliereof. Furthermore, although the ptjsent disclosure describes and/or illustrates a number of design choices and alternative embodmunts, such descriptions are not intended to be and should not be constx-ued as an exhaustive list of such choices and alternatives. Those skilled i:a the art will readily appreciate and understand adaitional altemarives and design choices that are within the spirit and scope 01 the inveniion as set forth in the appended dainis. Although the various embodiments are described herein with specific reference to th: fitting; coraporents being made of stainless steel, and in particular 316 stainless steel, such description is inter.dcd to be exemplary in natiu-e and sliould not be construed in a limiting sense. Those sklled in the art will readily appreciate that the invention may be realized using any number of di£ferei:;t types of metal materials fur the fitting components, as well as metal tubing m.Uerials, including but not limited to 31(5, 316L, 304, 304L, any austenitic or ferritic stainless st.i;el, any duplex stainless steel, any nickel alloy such as HASTALLOY, INCONEL or MONEL, any precipiution hardened stainless steel such as I7-4PH for example, brass, copper alloys, any carbon or low alloy steel such a^ 1018 stesl for example, md any leaded, re-phosphorized or re-sulphuriztid steel .such as 12L14 steel fi^r example. An important aspect of the choice of materials is that the tube gripping device preferably should be case or through hardened to a ratio of a: least about 3.3 and preferably 4 or mors times harder than the hardest tubing material that thi: fitting will be used with. Therefore, tlie hibe gripping device need not be made of the same ma:cj-ial as tJie tubing; iuelf. For example, as wi)l be discussed her^inbebw, the tube grippmg di:\ ic5 ;nay te selected from the stainless steel materials noted above, or other suitable materials tbiit can be c ise hai-dencd, such as magnesium, titanium and aluiumun, to nami some additional eximples. Furthennore, the frangible feature of the tube grippirig ring and female threaded n»it mjy iihio be realized in uoc-mctal tube fittings. Witii refeience lo FIG, 1, the present invention contemplates a Uibe fr.tLig 50 in WIMCII iher^ are only two discrete components prior to assembly, n:iniely a female direaded nut 51 ai^d a mule threaded body 54. The nut S2 is uubs;antiaUy different iiom tlie typical nut used in a prir art fsmile iy:,)Q tube nrtlnjjs. The tody 54 may be the similar in general de5ign as a typicil body used in prior fittingJi, however, s^ will be explained further herein, it is preferred but not viecessaiy tiiat the body 54 also be optimized for proper ma Not* that in the drawings the fittings are illustrated in longitudinal cross-section but cnly half of tlie section is illustrated, it being understood tliat the other half is identical and oiuitxd for clarity and ease of illustration. In all of \ho illustrations herein, various gaps and dLntinisions ire somewhat exaggerated for case of illustration. rhc body 54 is a generally cylindrical main body 56 that hai an ii:tcgral extension or c.id 56a The end extension 56a may be a hex body, for example, or piirt of another ccm^jonent such as for example a valve body as noted hereinabove. The main body 56 may be machined fiom the s;ime stock as the end extension 56a or may be otherwise attached such as by w:lcing or other suirable technique. The body 56 includes a first central longitudinal bore 58 tliat is apprjpriaiely sized to closely and slideably receive a ttibe end 13. The first bore 58 is scm'^vhat larger in diameter than a coaxial second bore 59 tb^at exte^ids through the t;nd e> tc nsion 55a of th€^ body 54. Of course, if the fitting 50 is a closed end coiuiection, the inner bore 59 would not be a through bore. The tube end 13 preferably bottoms against a couriterbore 60. Tte body 56 is n.achincd t>r other-j^ise formed with extejnal male threads 62 that threadably mate with conssponding female threads 64 formed or machined in the nut 52. It is contemplated that in oixlcr to avi)id inadvertent nuxing of old and new style body and nut parts with prior art fitting component;, that tlie thread pitch on the nut and body of tlie present inventiorj may be Rub:it2jitiall/ different fi-cm the thread pitch values of prior art fenule-type; tube fitting nuts and bo\3ie::. This will avoid interchange problems arid also 3llo^^s for a course pitch that provides hicjv axial stioke wiili reduced nut rotalion for complete pull-up. For example, a fitting that incoq-.oi-alcs Lhe present invention may ujie course pitch tlu'eads t]iat provide sufficient axial displacement to achieve proper pull-up in a half aim. A ^ypical pnor art fitting by comparison is pu! c(!-up witb 1 1/4 to 1 Vi lums. Nothing hov.^ever prevents t}.ie desiijner ftom making the thread plt:l'i any value suit Tlae central body bore 58 is preferably although not, necessaiily formed with a sli,=ht radially iuwsjd :apcr a relative to the k-ntitudinal axis X (FIG. 1) of the lube end 13 sach th?.u tlie diameter of die bore 58 clecieases radially in tlie axial direction tov/ards"; the ccuutcrbore 60. "vot example, this taper may be about 2" to about 4°, althou^Jh the selected angle is not particularly critical. The bore 58 diameter ai; tlie counterbore shoulder is just slightly less than the oiter dicroeter of thc'^tube end 13. In this marmer, the tube end 13 has a slight radial inliirfsrencc ::it of a few thousandths of an inch for example witli the bore 58. This interference belWLtei the ;)ore 51} and the tube end 13 provides an anli-iotatlon action to help prevent tl\e tube t:\Ci 13 frotr rotating during pull-up. This also reduces residual torsion stress that may be induce! into the tube end due to rotation of the tube gripping element (80) during pull-up. The tu'te end 13 does not necessarily have to bottom completely agndast "ie counterbore shoulder 60, Tills ..s because the interference fit helps prov'.de a good primary seal between Lhe boie 58 and the tu:e ttxi 13, The iutrrference fu also helps -mprovc the tube grip by Unc tube gripping element (8(0 i)y axiaJly holding the tube end stalionaiy during pull-up so that the fiill axial displacement of th.t tube t;rippinfe element (SO) is used for proper deformation x\d tube grip rather than any loijt i:xia{ mction 0: ruovement of the tube end during tightening. The taper of the bore 58 may cxiend gradually along its entire axial length or a shorter axial portion adjacent the counterbore 60 The m:t 52 includes a first central bore 70 having a first diameter Dl relative to thr Icmgitudinal axis of the fitting SO. Tlie nut 52 also includes a second bore 72 having a second dicmjter D2 relative to the cenfal longitudinal axis of tlie fitring 50. In thii embodiment, the Cisjnsrer D2 is less than the diameter Dl. Fuittiermore, the diameter D2 is sized so that the bore 7:: d::f5nes a generally cylindrical wall that receives the tube end 13 (FIG. 2). The first bore 70 lecmiaates a:: a location that is axially spaced from the nui back end 74 to form a trepan 75, such that iie nut 52 include3 a radially inwardly extending collar 76. The collar 76 is generally 1 defineJ by the back end wall 74 of the nut 52, the smaller diameter bore 72 and ihe larger diarae:e;:bore70. In accordance with a significan: a^spect of the inveiiticu, the rut 52 includes a tube grippiiij; device 80 that extends axially mwa;-dly m a somewhat cacitilcvered fashion fiom the cellar Tt"). The tube g-dppmg device iti this e:s ample is in the gftncraJ form of a gripping nng 80 mcl irclude^ lUi inntr horz 82 that defines a subsiiiitially cylinriticul v/all that closely receiver, the tuu': end 13 (FIG. 2). Tac diameter D3 of the bore 82 maybe tfi^ SJuTie a5 or different from the diajnttter of the second nut bcie 72. The cylindrical Vr'all thai defines the gripping ring bore 82 eAlunJs axial y from a tapered front or iiosi portion 84 of the grippin.g ring 80. The nose portion 84 :.nt;ludc3 a..i axially vapered outer surface 8o tJiat increases in the radial dimension tcwzrds the back £;nd of the rini; 80. The tapered outer surface 86 extends from a generally radial front end 85 of die gripping device 80. Tlilii generally radial fiont end 85 joins to tiae inner cylindrical bore 82 ai. a preferably :iharr»^ comer 87. Alternatively, however, there may be provided a cir^UJcriierential recess or step or notch or other geometry (not shown) in the front end of the ring 80 having a iiamctei that is somewhat larger tlian the diameter D3 and axially extending from th€; fei)nt cud 85 iowAids ihe back end 74 of the nut 52. The Tapered surface 86 joins thj front end 85 preferably by a ladius portion 89 and at its a>:ial oiposiie cr.d by a radios 86a to a {generally cylindrical portion 91, which in tuni join^ via a radius 93 to the trepan 75. It is noted at thi;i point that the various geomiie/y chsjracterisdcs of the lube gripp ng devxe 80 (such as, for example, the; various recesses, notches;, tapered portions, radius portions and so on) are selected so as to effect an appropriate radially inward hinging action as will be further explained hereinafter Accordingly^ the geometry of a tube gripping device 80 wiil he deter.'nintMi by the characteristics of the material of the tubing such as hardness and the fittinij conip In accorddiics with another ai.pect of the invenrion, the tube gripping device or ferrule 80 is attached to the female threaded rrat 52 by a thin frangible web portion 95. This web po .tion breaJcs (as illustrated in HG, 2) when the femile 80 ciims initlaUy against a canuning suifacc (88) during pull-up so that the tube gripping device or fcnrule becomes a separate piece and ftinction^ with Uu: nut aiid boJy in effect as a single ferrule fitting. The sef>arated ferrale 80 hy:> a bixck cr.d 150 th:it is axially driven by a radially inwardly e-xlcnding wall 152 of the nui 52 th:i S'^rves zs a drive liurface for driving the feirale 80 forward against the caniming surface for corjpicting aa initial pull-up. Th.c frangible •A'eb portion 95 is preferably designed so that upon 1 S(rpar:itioii of thtf dtvlce SO from the nut 52, the surface 95a that is exposed along the break line docs aot inurfere wich ihe drive &'iriAcc 152 of this nut dujing farther pull-up to complere the asssn'.bly. As used b;reiii, the te:n:is "tube gripping device" and 'fei-rulc" or "single fiin-ule" are us:d :nterchangsabLy when referring to ihedevice 80 after separation from the nut 52. The ferrale 80 is caachiaed with tlie feuigible web 95 portion by forming a radial grcove 154 t.iat is an^jled generally toward ths inside of the female tlireaded nut 52. This groove 154 f jrms the back cud 150 of the ferrule 80 and also the radia] wall 3S2 of die nut that diive the fei'Aiit axially againil tiie camming sui-face after the fenxile 80 separates from the nut 52. Prt;ferably bat not ntcess^ly the wall 152 and the back end 150 ;ire machined at an angle of aboul 75" degrees or so relative to the tube bore axis X, altliough this angle may be different depending on the particular application. The^e surfaces 152 and 150 tnay be contoured lo reduce galliiig and torque if jjo required. With reference to FIGS. 1, 2 and 3, the tapered nose portion 84 initially engages an a:.;iidly tspcrcd ca-truning surlace 88 that forms an opening to the tube bore 58 In the main body 56. Tte taper'3 Upon a completed pull-up, the back end 90 of the body 54 contacts the trepan 75 which serveii as a poyitive stop against over tightening. Should remakes be desired, the back end 90 n .ay be socially spaced from the trepan 75 upon a completed fir;:t pull-up. Proper puU-up in this c;a3c may be verified using a gap gauge or other suitable technique, as is known. The tvibc gripping ferrule 80 is shaped to effect several important functions of the fitting 50. The feirule 80 must, upon proper puU-up, provide a fluid-tight primary seal against th.-5 tipercd canuniag surface 88. This seal may be a primary outer seal for the tube fitting 50, or n:.ly b2 in effect a se:;ondary or back-up seal to any seal formed be^vcen the tube end 13 and the bcdy S4, for example along the l>ore wall 58 and/or tiie counterborc 60. The separated ferrule 80 al:w3 will foim a primary seal at the location where the femilc 80 bites into the outer surface of thci tube end 13 in the area where the cylindrical bore 82 of ibe ferrule 80 engages the vibt end ^ outsr surface, Again, this primary seal may in effect be a back-ap or secondary seal to any seal formd by the tube end 13 agaiiiat the body 5i4. In any event, the ferralc 80 must form primary seals aj;ajnst tlie C2na::ning surface 88 and the outer surface of the rabe end 13, In addition, the fci^-izl: 80 niiist adequately grip the cube end 13 so as to maintain seal integrity under pressure, ten.p'.'tuturc ind vibrii-tion effeclsi, and to prevent the tube end fruui separating from the fitting unilei such c;irc\imstajxeij. In o.rd'i.r to achieve a fluid-tight seal and tube gapping action, the ferrule 80 is dewgied to oe pla;iti::ally deforcied and sws.ged into the tube end upon completed pul!-up, a^ ill.itiaved in FIG^ 3. This result is acldeved by designing the ferrule 80 to have a hingiug action wherirby the tapered nose portion 84 is not only driven axialiy forwiird as the nut 52 is threaded onto iha body 54, tut also is radially displaced or driven into engagement widi tl-ic outer suiface of this tube t:nd 13 wall. iThe forward end 92 of the nose portloQ 84 is thus compressed and embedded into the tubing wall with a rcsultajit stress riser or bite in the region designated 94 in FlO- 3. The front'end bite 94 produces a generally radially extending wall or shoulder 99 form-i'd out of the plastically defonned tube end material lb; shoulder 99 engages the enjbedded &Dnt end 91 of the gripping ring HO to thus form an exceptionally strong mechanical re'^istiTice to lube bb^v' out at higher pressures. The embedded ftont jnd 92 thus provides botli an • e-xce'lent seal and t. sxong grip on the tube er^d 13. The ling SO [^ fiither designed to exhibit the af:ire .mentioned radially inward liinging action so as to swage or collet thj cylindrical wall 82 ag;iiri3t the tube end at a location axialiy adjacent or spaced from the stress riser bite 94 and gdierally daiignated with the numeral 96. This swaginjj and collet -effect substantially enhances thf tube gripping function and serves to isobte the rinbcdded nose portion and bite 94 from the cf["cc:s of down tube vibration and also temperature changes. Although tlie present invention is described herein in the various embodiments as effscing an embedded nose portion and attendant swaging ac-tion, tliose skilled in tlie art will appn:ciat« that in KOrie applications such rigorous design criteria may not always be required, paj-titularly for fitiiags that will be exposed to moderate temperature, vibration and pressure eftec\5. ThfiTefore, the additional design aspects of the nut, body and gripping m\g set forth hfii-ciii as preferred embodiments should therefore not be construed in a limiting sense but rather as selectable eriiajicdtncnts of the basic concepts of the invention to be used as required for palicular application?!. In o.:dar to achieve the desired swaging action aj^d tube grip» the ferrule 80 is designed to C'Xhibit thi hinging action that allows the Upered nose portion 84 and the central or mi'1-portion (as at th-; region of the cylindj-ical bote 82 or th.e region designated 94) of the gi-jpug rinf; 80 to be radially inwardly compressed ar, it engages with the tapered camming moutli 88 o;the body 56. This hinging action is also U£ed to provide a significant radial di:-,pl.ic2ment and conrpression of t)io cylindrical, wall 82 to swage a central or mid-portion of the feraiic 80 body onto tte tube end 13 axially fidjaceut to the stress ristr 94. In the embodiment of F1G!:<. tie hinj5il.g action is faclliuted by providing a prefeired althougli not required radial iicer circumferential notch that axially positioned between the cylindrical portions and nou:h i:i suitably shaped to penni femile plastically dcfonii collapse in controlled manner fio as radially compress wall agalost die tube end with lh disired collet ejyect. pardcular geometry of gripping ring will thus be designed so thit i.s m:t further threaded tightened onto body after ferrule separates ihs f hinges deforms grip seal botti against cni iind tapered camming mouth standard design procedures such finite element aralysis may uned optimize based on vaiiable factors tht t.ibing material tubing hardness thickness reijuircd pressure temperature viftntion peiformanc characteriiitics.> Proper deformation of the feiiule 80 may ftiitinjr be controlled by selecting an apjTTupriate <:ontour for the tapered surface this enga.ges nose of feiru.c aid theixfore wll in part determine timing and mcmner how feirule hictgus. com plastically deform. to properly embed portion bite into tubing zlso provide desired collet o: swaging acticu. furthermore contour cajniaing sa may be de achieve seal between ferrule portiijn tlie is important overall performance fitting as he provided tube end> The nat 52 widi its integral tube gripping ferrule 80 may be manufactured by stindai-d ma:hining cperaiions, and will t)pically include a trepan operation to form the outer contour of tie ring 80. The otiier features of the nut 52 can be realized as well with known mi.clining operation:;, Preferably but not necjssarily the nut 32 includes wrench flats 102 to pti.-mit tl:e iser to tii^hten tiie nut 52 onto the body 54, Thoye sldlled m the art will readily apprxiate tfiat use of the fitting 50 only requires relative rotauon between the nut 52 and the boJy 54. such that cither compDnen: or bcth may be rotated as required duiing a pull-up opcrauon. V/e have found that it is highly ilesirable for the canuning sunacc 88 to form a cirrjiiin^ angle G of ahout 35^-60' relative to the longitudinal ^%U X of tlie fitting 50 and tube end 1.5. Mote pref In the excrnplary cmbodimen!:s herein, tiie nose portion 84 includes the radius pojtion 89 thai transitions to the outer tapered surface 86. This outer surface 86 tapers generally at vji angle tliat is not as steep as the angle of tlxe canuning surface 8U. The tapered outer surface 86 prcferablv' Upere axially with an increasing radial dlinensioa towards the back end of the gnpp: ng ring 80. Thi.'i tapered outer portion 86 contacts the camming surface 88 with, in effect, a generally najTOW zone or line contact upon jmll-up that has high stress and material coining to allow the froi:t end of the gripping ring 80 tc coin into the camming surface 88. Therefore, the tern 'generally naircw line contact" is not intended to preclude an area of contact between the ou'er u.pere coalai..t of metal buriiii:bed on metal to effect c. gas tight primar>' seol between tiic tapered surface 86 ^ind the canming surface 88. It is important to note that the use of a paiticular caijuning angle is not dependent nccissadly on the contour of the surface 88. In other words, thr aii?;le of interest is the angle at wbicli the fr)ni end of the gripping ring SO contacts the camming sxirface R8 to fom\ a seal thc'.'f^'it. Thu>, t^ie ciiJiming surface 88 may indeed be made with a ncn-frtisto-conical contour, bir: tiic seal is still forncdby the Eroiit end of the ferrule 80 contactirg a steep angled f.urface 88. Adiirional .ompouac angles or contours of the cdnvming surface 88 may be unrd to better fac: U:ate the iiinginis; tction and tube bite achieved by the ferrule 80- Wbeth.;;r th-5 caninaiiig surface 8!? is formed &s a coj:tpoiind ai:iglcd surface with adoit .cnal angled pon:.ons that arc steeper or shallower to faciiit2iie the hinging acion and bite of th The steeper carnming surface «mgle has llic addiiitvoal benefit that the note or front po 'ion of the lube gripping device 80 may b: formed witli subs:ancially more nia^s as compared to if :he firort portion had to engugs a shallower camming surface angle as in the prior art single ferva.e and gripping ring desigr^. Tnis added mass, along with the hinging action, tends to pcjjii.on a sibstan::al!y greater mass of material at or near t?ie location of the tube bitt; 94. This sij^nfftcantly strengthens the tube gripping device in resisting pressure and also strengthens the cc'vle: effect that isolates the bite fiom vibration and temperature effects, as contrasted to jjrior arc sii.-gl2 fsrrultj or gripping ring designs. The hinging action also results in the back end of the tube giipfing de\ice (i.e. the end opposite the noiie erjd 84) from contacting the tube end, so that the entin: tube gripping' dsvice is in iaial and radial compression. In general, for a tube grippmg device suclri as a ferrule to embed into, bkt s^nd grip th tht pr'or art allows a fi:trule to cmbsd into a a.be even when the ferrule It only moderately harJer thaji (.!<: tube under these circum3t if the gripping device were only rr l than tlie end. would bs unable to adsqu giip t for a steep angle canuiiing siuface btc of substantially shorter axial movement rube ducin. pull-up caused by steeper cairuning imgle. kcwever in accordance with present invcn:ion b niakiag rubs jrripping significantly hinder otbby ane.le cainnr.ng surface may be used or.d is effective cau-: ihc adf qiai-ely bite into envl grip tubs.> The steeper camming angle 0 of the present invention also results m a much sh:rt!:r di3taj\ce of u;t.ial displacement of the ferrule 80 during pull-up. Consequently, the nose poiticiji 84 ^^ill need to be radially deformed and compressed into tne tube end 13 -with a much shfirt::r axial displacement or sliding movem;ut. In order to acJiievc the proper tube grip thcHj th)! ft;rTule 8(1 is prefeiably-case hardened to 2 hardness of at least about 3.3 times harder than the tubin.j material For »::xample, if the tubing material is stainless sieel» it may exhibit a hardness of up tc about 200 VLcVers. Therefore, in accordance with this aapect of the invention, when the fittini; 50 is used with such hard aiaterials, the tube gripping device should be hardened to a rstio of at lea^t about 3.3 times harder ihan the tubing. More preferred, the tube gripping device should be hixdened to a ratio of at lease 4 tiines harder than the tubing. Still further, the entire Eiipiar.g ring SO ^ecd not be cass hardened, but rather only tlie nose porti(ui 84 may be selectively case hardened. In a:coriince with this a-speci 0: the Lnventiori^ all or pniz of the nut 53 and body 54 u.ay be ihrougli hanlencd or case hardened to Increase the tube grip of the fitting 50 when U!i;d witli lumler tubing materials such as siaia!e':s s:ee!. Suitable case hardening processes are fuly descrii)ed m United States Patent Nos. 6.165,597 and 6\093,3C3 and copending patent a[)phcaticn serial \:o. 09/494.093 filed on January 28» 2000 for MOD.tFII:D LOW Ti'MPEBA^:iJRE CASE HARDEMWG PROCESS, issued to tlie assignee of the present ir//e.iiti,on, tlie entire disclosures of which are fally incorporated herein by reference. These processes produce a hardness of the tube gripping device of iibout 800 to 1000 Vickers or higher without coniprcmidng the corrosi-:)n resistance of the fitting. Other case hardening techniques h':w:;ver may be used as required. Case hardening of the tube gjippjng ring 80 allow^ the ring 80 to a:iequate.y grip ii.nd seal against tubing materials such as stainless steei including duplex sudnlesws sttel Thcj above rcfsrenced case hardening patents have an additionaJ benefit of prcvR.ing suifaccs on the ring 83 that reduce or prevent galling bctv/ccii the ring 80 (which rot3tc:i with die nut 52) and the tubing. Vario'xs lubricarus may al^ be used v/iih txie nibc giipping rin£ 80 to reduce gallin.j and residual touion such as, for cx^mpk, PTFE gf^asc'S, and grease; containing rnc yldenum disulprude or tungsttm disulphidt;. Case h:;irdening tecl:niques typically will resul: 'v^ tlni cnliiQ nut 52 and integral tub) f^ippin^ ring {10 to be case hardened. Wien the c?^e h:irdenir.g is performed on stainlesr, steel, for exi:mple. as in tiie abo'/t; reference.! patctus cr patent application, an adherent oxide skill i^ formed. In aa<:ither embodiment of the invention a solid lubricant m.iy be applied to tlie llirtiac>s of the stainle;>s; stael nuts 52 to reduce firiction and tlie hence puU-up torque during tigfiltning. .\ny sclic lubricant can be used for this purpose and msiny such solid lubricants are weU iaiown. A fiw examples are graphit, molybdenum disulfide, tungsten disulfide and UK\:UTE (ultra bigli niolecular sveight polj'etiiylene). The:ie lubricanfi can be used neat, i.e. not combined with another maur.al, or mixed \vith another material such as a resinous carrier or the lilie. In zidition, they can be used in es&c:ntiaUy any solid fomi including powders, granules ana pistes. Solid lubricants of this type ;arc "well knov^n .comn:.ercial products. Examples inclU'.le Dow Corniiig'& 321 Dr) Film Lubricant available from Dow Comins Corporation of MiilsJid, Miclugit;. and SIickotcS Dry Lube 100 available' from Tnms Chem Coatings, of Mctniovia, California Thc5e lubricants can he applied by any standard meLhcd such as by hand, by aeros:)! or ail sprayin}! or by automatic cquipmcut. Ajiy ccaririg cliicijiess can be usc In a pg^rticular embodiment of the invention, a dry lubricant as described above is usod on stair less st^el nuts 52 which have been subjected to low ten-.perature carburization \ising caibcti moncxide as i:he carbon £.ourcG. Stainless steel is stainless because of the thin, coherent cbj'OiMium o):ide film which inherently fomis when the steel i3 exposed to air. Low temperature cajbirizatior. of stainlcb'S fiteel parts, such as (hose made from AISI 316 and 316L stainless steely usually leav^ss the pa.rt surfaces coated with a layer of soot. Before use this sooc is usually rcaio\'cd by v/ushing. WTiea carbon monoxide is used as tlie ca;:bon source in low terr.psrature cart'Urizatiort, not only does soot, ibrm but in addition a heavy oxide tum also form3. This heavy oxnle f.lm ii consildttrably different frooi tlie coherent chrorriurn oxide fiirn which makes sia:nl<:s:> steel stainlesii in that it is. thicker and not coherent. Th£;refore, this P.Im is also removed belbrr use to uncover the part's csTburi^ed surface. In accordance with this particular embodiment, tl\\;5 heavy oxide film is not rcr.:o',ed before apf'lication of tlic solid lubrictint. Rather, il is left on the carburized part sur ace:;, or et least tha portions of the carbuiized surfaces to be lubricated. In accordance tliis paj'-icular erobodimeni, it has been found that the naturally porous stiucture of this heavy oxide skiji iicts 05 sn anchor for binding the lubrica:it to tlie part surfaces. As a result, Ihti lubricant is more adherent than would otJiei-wIsc be the ca^e, and hence is able to v/ithsrand repeated fitting renialnes (i.e., loosening and re-tightening of the nut) without bcir^g removed, FIG. 4 iltvitrales another embodiment of the invention in which all elei7ienl5 are ge-erilly the same as the prior embodiment vitli one variation. In the frangible web portion 95, a srcis concentrating notch 300 is formed therein. In this embodiment the stress concentrating noicti JOO is formed as a generally tight radius thai creates a thinner web of material 302 Co prcmote a rapid clear, break of tt.c ferrule 80 from the nut 52. The break thus occurs as a resuh of a minimal span of rotation of the nut 52 shcnly past finger tight posi^lon. The shape of the br:al: is alsr- less rai':ged. Other shapes of the notch 300 may be \ised as required includiiig cllrptical, tri^tngular aiid so on for example. Tlie ir^vemicn ha.-; been described widi rci'crencc to the preferred embodiment. Cliraily, mociificattons and alterations will occa to others upon a rcadijig and xinders;anding of this specification. U is intended to include a]l such modifications ar:d alteiaticns insofar as they ccmc within the scope of the appended clairnr. or the equivalents tliereof. A stainless steel part substantially as herein described with reference to the accompanying drawings. A process for enhancing the slipperiness of the carburized surface of a stainless steel part substantially as herein described with reference to the accompanying drawings.

Full Text

TLW: nTTKNG WITH SEPARABLE TUBE GRIPPING DEVICE
Related Applicatioas
Thi::. application claims the benefit of United States Provisional pateiit application icii£tl no. 60/26(3,735 filed on February 6, 2001 for TOBE HTTING WI'IH INTEGRAI. NUT A]M> FEilltULK. TOd senal LO. 60/329,943 filed in October 17, 2002 for TUBE fm'rMG, \iic sn :ii'e dis Technical Field Of The Invontioa
The subject invention is iienerally directed to the arc of rube fittings. More pd.rL:.cular.y, the invention is tirccted to a flareless tube fitting that uses a tube gripping elcmer.t ihiii is iniiially joined to csie of the coupLng ekineats and s?arates therefrom during assembly onto a tube end.
Backarouad of tbelnveutioQ
Tube fit;ings ure used to join or coxmect a tube eid to another member, whether that other member be another tube end such as through T-fittings and elbow fittings, for example, or a devitx that nucds to be in fluid communication with the tube end, such as for example, a vjtlve. Ai. used herein tlie terras *'rube*' and 'tubing" are inteiided to include but not be limited to pioe as veil. Aziy tube fittbig must accomplish two important functions within the pressure, tem?eran.ie and vibration criteria tliat tl;e tube fitting is designed to meet. Fir^t, the tube fitting mat grip the tube end so as to prevent loss of seal or tube blow out. Secondly, the tube fitting misx maintain u primary seiil against lca!ca[je. The require-meiit that a tube fitting accomplisri th2se two fimction.3 has b A flarelcss tube fitting generally refers to a type of tube fitting in which the tube er:d remains subs.:ancially tubular, in contrast to a flared tube fitting in which the tube end is outwardly flared c^ver a fitting component. Flaied tube end;> ar« commonly encountered in use w.Ui plastic tubing and plastic tube fittings. The present invention is not primarily directed lo piastic tubing or cube fittings because such fittings have significantly difiercnt challenges and; material properlie:> that affect the abilit>' of the fitting to both grip the tube and provide tn

adequate sea'. Hov/cvtr. some of the aspects of tivc inveiition may apply to non-met£i tuoe fitt]jij;s, particularly the separable tube gripping element aspect.
Tube fittings that arc intended for U£c with staiol^ss j;tcel and otJier luetal tubing, foi c.\aJTiple. are particularly challeaging to desiip; m order to ncliieve the desired tube grip and se:ii rdnctior.s. Tai;: ariies from the natuie of stainless stcol which, ir, toms of t>pical coroTiitrrcially avaii;ibie tubing material, is a vcr/ hard matcri^il, usually on tlie order of up to 200 Vu.ki:T5i. SuduJess stjel ard other metal tubing is alio used for high pressure applications in wliicli \ht tuDing wall thickness is substantid (referred to in the ar?: as "hed\7 walled" tubing). Plcavy wall tubing is difficult to grip because it 15 not only hard but it is also not panicularly ductile. Lo\\ ductility makea it more difficult to deform the tubing plastically so as to achieve a dtt!:iii::d tube jtip.
Tube fillings typically include an assembly of; 1) a tube gripping device, often in
♦
the fcrm of a ferrule cr fermles, or a gripping; ri.ng-like stnict\^e, and 2) a pull-up mechanism for causbj! tiie 'rube gripping device to be installed on a tube end $0 as to grip the tube end and provide a seal against leakage. The term "pull-up" simply refers to the operation cf ti£htening xiii ti.be fitting asstimbly so as to complete tx assembly of the fitting onto the t^be end with the dciiinrd tube grip and «ea!.
UsuiiUy a tube titling is lirst assembled in a *'finger tight" condition and then a wr3n:h or other suit;;ble tool is used to tigliten or 'pull up" the lilting to its final initial and cccnjilctc asiiembled condition. The pull up mechanism most commonly U5ed is a threaded co--ui;ction cf a fexnaie threaded nut component and a male thr'^aikd body component, with the tube gripping dc\r;ce: being acted upon by ir.ese two components as they are threaded and tignt:;ned to£;ether. The body includes a tube end receiving bore witia ^n angled camming surface at th'ij outer i5onion of that bore. The most commonly used canuning surfaces arc frusto-conical such tliat the- term "camming angle'* refers to the cone angle of the camming surface relative to the tube end longitudinal axis or outer surface. The tube end is axially inserted into the body bore ajid extends past the fcusto-conical caitiming surface. Th« gripping device is slipped onto tilt: tube end and tlie nut is partially threaded onto the body to the fmger tight position such that the tabs gripping dei'ice capl"ured axially between the camming surface and the nut. The nut tyi)ic ally in:;ludes :in inward shoulder that diivcs the tube gnpping device into engagement with the .-Lngled :ammin^; surface on the body as the nut and bady components are threadably ti|!httin.ed together. The angled camming surface imparts a radial compression to the tube giip{:irig de\icc, forcing the tube gripping dwce into a gripping engagement with the tube end.

Tl'ie :\i':)e gripping device typically is to fom a seal agaimt tlict outer s;jrface of the tubing and also .igaiast the angled camming surface.
The most conunonly used tube gripping devices in stainless steel tube fittings today (the most commonly used are fcn*alc-t>pc tube fittings) acliieve tube grip by causing a frcnl: or no.sd portion of the tube giipping device to bite iato the tube end outer surface As used h Over the years thire have been numerou.-^ tube fining designs that do net rely on a *'l:it*." xypt actiont but rather me-.-ely radially compress the tube gripping device agaiiisi tliC tubing oL.te: .surface, some with-the effect of indenting into the tubing witliout creaung a bite. These dfsiijns are not suitable for higli prcssiue stainless steel tube fittings. The most common ccniiicrcially available btainlecs; steel tube fittings especially for higji pressure applications have hib-torically been of two radically distinct designs of the rabe gripping device-single ferrule tube ftrtii igs and two ferrule tube fittings.
A sii'.gle ferrule tube fitting, as the name iJupUes, uses a single ferrule to accc-niplish both djs tube grip and sea! functions. However, it is becoming increasingly recognized diat thtsc Uvo functions are at odds with each other when designing a tube fitting that c;ai nr^eet a desired nibe grip and seal pcrfcnnance criteria. This is because the design criteria T'leded to {5sure tha the tube fitting achieves an adequate tube grip usually works against the abiltj' of rlie single ferrule to also provide an eCTective seal. Consequently, although prior art single ferrule fitting,? can achieve adequate tube grip ia some casts, this tube grip performance comes at tlie expv.x/er, even in such lower pressure applications single fcrniie seal performance remains less thaj I desired.
For single ferrule tube fittir.gs, the biting action is usually associated with the i>nj;le femJe being designed to bow in a L-adially outward direction from the tube wall in the

centra., region or mid-portion of tJie single fcnul-s body between rjie front aad back ends thereof. The fi'Ml end of the ff the single ferruli to as to radially compresa tlie back end of the ferrule into a gripping action on tb.e tube end. In some smj'^k fermle designs, the back ead of the ferrule appar^-T.tly is intended to bite Into the tube end. Thti lack end tube grip is sometioies used with the single femile in order to attempt to improve the tubij fitliug's performance under vibration because the back end grip attempts to isolate dovm tube vibratiori from affecting the &ont end tube bite.
The US:! of a back end tube grip actually w^orks against the effort to grip the tube em: at the front end of the^cjngle femils. Ideally, the single ferrule sliould be completely in three dimensional comprssiiion between the nut ar;d the canuniDg fturface of the body. Providing a back i:nd grip actually placer, a counter acting tension to the sLngJe fen^ulc that works against the front end compressiou'being used to provide tlie tube grip. Additionally, the outward bowing aci.oi; tends to work against the effort to grip the tube at the firont end of the single ferrule be: aiise, in order to enable the outward bnwir g action, the single fenule requires a lessened mass that ii adjaccm the t)ibe gripping "bite'*. The our^^'ard bowing action radially displaces femile mjss CintraJ lo the firrrule body away from the tube end. Consequently, an outwardly bov^ed singk; rerrul In ordtT to achieve an adequate tube grip on stainless steel tubing, single ferrule stainiesis steel tube fitdngs have historically used a rather shallow caiiuning angle of between ten and t^vcnty degrees. This range of angles is refcned lo herdn as '^shallow" only as a term of convtjnicnce in that the angle is rather small, llie shallow camming angle has been used in single ferrule fittin;5S to cbtiun a mechanical advantage because the shallcw angle provides an axially elcn^iated camming surface against which to slide and radially compress the single ferrule front end (0 bite into the tube end outer surface. Hard stainless steel tubing material necessitated this elcn^:ai:ed sliding ca:-nming action in order to be able to get tlie single ferrule to create an adi^qtiate bit*: for tube grip. Over the years, the single ferrule ha^ been through hardened or case h£::dened so as to be significantly harder than tcic stainless steel tubing, however, the shallow (famming an?le is stil- used today in such single ferrule fittmgs to obtain a mechanical advantage

froni the female slidnj along the camming i-urfacc to produce the "bite" so as to assure an adequ2.te tube gilp. An example of a convnercially available single feirule tube fitting that uses a case: hiLfdened ferrult lijid a shallow camming angle of about twenty degrees is the CPI fitting line available from Pjirker-Hatinifin Corporation. Another exatnple is the EO fitting line avai allc Iron:. Ernitto GmbH that uses a tluough hardened single ferrule and a tuelvs degree rarr^niaj'^angh.
In som«: single fertile designs, a non-conical camming surface has b-^en iried wh The sha.llow camming angle and elongated camming surface and axial movement needed 1o achieve an adequate tube grip with a single ferrule fitiing, however, compromises the abi^aty of the single feirule^.Jo achieve the seal function, especially in extreme cnvironnicats and for seiding ^is. This is because the firont end of tlic single fcirule attempts to make the seal againiit the a::iaUy elc^ngated camming surface. The radially outward bowling action causes a lariser portion of the o.itcr surface of the fi^ont end of the single forruJe to come into contact witli the cEiuming surface against which it is being driven, The result necessarily is a l&rger seal suriace area Detween die outer surface of the single ferrule and tlie camming surface. This enhirgcd seal area cauiies an unwanted distribution of the sealing force between the single fenule and tl:.e camming surface, and also creates a larger area for surf2.cc imperfections to allow leaks to cccur. This is particularly a metal to metal seal issue (as contrasted to non-metaJ to non-metal sei/s: for exiraple, in a plastic fitting it is usually desirable to provide an enlarged seal contact arcu because ihemore highly ductile plastic material can better form a. seal between the t>'0 sui:a^:es.)
Because historically the single ferrule fitting has used a shallow camming angle to acliie-'e adequate tube grip, the less than optimum seal function is either tolerated as a recognized limitation on the application of the fitting, or additional featuiss have been designed into the sir-;>k ferrule: fitting, most notably attempts to include one or more; elastcmeric seals with ihe sin.jh: ferrule or with which die single ferrule cooperates to provide a better seal with stainless sie.d mbing. See, for example. United States Patent nos. 6,073,976 aind 5,351,993. United States Patent No. 6,073,976 illustrates a t>pical exariple of a single "ferrule" (called a "cutting ring" in thii patent) fitting that attempts to solve the "seal" issue wtJi added elastomeric seal. The

5,.i:l,99£ patent describcr, th= beri'sfits obtained by separating the tube grip and seal f;^ctions m.o two separate components.
A commercially available sjid highly succcssfiil two ferrule fitting used for tubing is cDrnmiircially Eivailabic from Swagelok Company, Solon, Ohio and is described in United States Paienx No.^. 6,131,962 iind 3»103,373 both of ^hich arc o^vned in common by tlis a^sigaee oj" iJic piesent iuY^ntion, iht entire disclosures of v/hlth are fully iucorporated herein by veferenctf In this 1:^0 ferrule fitting, the tiibc grip and seal ftmctiona aho are t>cpar?te!y achieved by the i:s2 of tv^o ferrules, The foiv^'ard or &ont fenule piorides an excellent seal even ag^nsc g;:5, and the back or rear ferrule provides *in excellent tube grip.
The front feuule achieves an excellent seal by camming against a shallow ciimming surface ;mgle s'jch as twenty dcj^rees. Tliis is because the front ferrule doe5 not need to slid'3 exc(;ssively on the canantiug iruirfiice iu order to achieve a lube grip functionv Likewise, the front fcm:l6 is not ca^e hardened because the primary purpose of the front ferrule Is to seal and is not to bit? into \he tub^'Cnd. Thus the relatively "softer" front ferrule achieves an excellent seal, p;;rticulaily again-it gas, even though the body corneal caning surface presents a cammincj ai gtc of i.bout Tiventy degrees.
The back ferrule achieves the tube grip fiincidon in the above noted two ferrule aibe fitting. The back femjlc is case hardened to be substan'tially haider than the tube end. The fiDnt end of the back femile cams against a frusto-conical camming surface formed in the back eid of th: front feiiulc. The ostensible angle of this camTning surface is forty-five degrees, but d.ie to the slidini:; mcvernent of the front fermie, the efTectivj camming aiigle is actually a sl^'low jjigle of jibout fifreet. to twenty degrees. Although the effective camming ajigle for the bacx ferrjle is shs-Uow, the bz-ck feirule is not required tc provide a primaiy seal (although it can form secondary cr backup seals). The back femile also docs not exhibit the undcsired bowing a( tion but rather grips the cube end as a fiiuctiou of a raiHaily inward hinging action. As used httein, tl:.e term ^'hinging" refers to a controlled dcforraaticn of the ferrule such that a central region or mid-pordon of the fjmile body undergoes an inwardly radial compression, as distinctly contrasted to a bowing or radially outward displacement. Thus, the effective shallow camming angle not only does not compromise the luting seal capability, it actually substantially enhances tfic overall performance of the tube fitting especially for stainless steel tubing.
By using separate ferrules for each to achieve primarily only one of the key rube fitlng fuictions. 'the t^'o ferrule tubs fitting achieves tremendous tube grip and seal functions. Thii prio:: art two ferrule lube fitting thus ha:5 enjoyed tremendou;* commercial success especially

ir. tlic art cif stainteiis steel tubing in part due to its performar.c.'; char^cteiisdcs such ai high p/cjiSiire rating on ±t order of 15000 psi, wide temperature rating of cryogenic to 1200 °F and in rr.aiiy applizationii a significant number of renakes (a "remalc;:" r:fers to the loosening and re-Li^X'oing cif a fittiai; after an initial pull-upj.
United States Patent No. 3,248,136 iUustratc3 use of a single locking ring a^ copoi'ed to a femj.le, wherein the locking ring acts against a surface having an angle that appears tci be greaUr than rwenty degrees or more, tut the ring doss not appear to plastically deform into the tubing l)ur ratlie: remains elastic so that the ring is designed to retain its original shape after p ilL-up, boil of whi:h are features that are uusuiiable for sta:rJess steel lube fittings of the type coniidered herein. Japanese urtlit>' model pullication 44-29659 illustrates a tightening rin^ tliat cop.jars to be intcnd-rd to have a bowing efl'tct and grip the tube at the front and back ends. The litii'ig does not apptiar to be applicable to stainless steel tubing as th? tube is covered with a resin
Attempts have been made to design tube ilttbgs wiih a rjbe gripping element that Si5p;ir:ites during pull-upy to ninclion as a single element tube gripping device. Known designs place the breakaway element on the mule threaded component. Additionally, the known designs eitl-.ei force the tube gjippiag clement &ga:n::t a shallow cainnung surface angle or do not attempt !() create a hibc gripping bite into the tube wall. Thus the prior an designs suffer froni the same limitations as the prior art single ferrule tube fitting designs.
M:m;,' applications and uses of the tbcvc-described iwo feirulc SWAGELOK tube f ning do not requi:c such higli pressure, temperature and rcmaki: performance characteristics. 7hc present Lnveati:»n U directed to a new fitting concept that can naeet lower performance cha.-acterisiics without compromising overall fitting intcgritj* and pwfonnance.
Summary of the loveptton
In accordance with one aspect of ihe invention, a new tube fittmg concept requires usei' assembly of only two components, namely a fitting body and a fitting nut. The nui and body arc adapted to be threadably coupled together by relative rotation therebetween. The nut includes an initially integral Cube gripping clement or fcn-ulc that cooperates with a canwiing surface on tlie body when th? fitting is made-up. The tube gripping clement may be machined with the nut or separately attachird thereto ty any convenient process such as brazing, welding or soldering, fir examph. In the described embodiment tlie tube gripping element is a ring like structure that, after it separates fircm the component to whicli it is attached, operates as a single ferrule. The d(tz:c^ti foitule is radially compressed and plastically deformed against tike tube outer wall to

fojT! a seal aiij a tig'at tube grip bite. The detached ferrule also forrn;; a primary seal against the caxr.."niag surf:ice. In one embodment, the fe:niilc includes an outer tapered surface at its front end fomilng a generally narrow Ibe coniact-t}^e sea! against the cacaming surface. Thcs ferrule in cue cnabod.ment i$ designed to have a liingiiig action and to plastic deform during pull-up to cm1:cd tlie nos:e portion into che tubing wall foi: excellent tube grip, and an axially adjacent swage or c:i\'x\ rone that isolates the embedded nose portion from vibration effects. The hinging action . alsc bibs to keep the ferrule outer tapered surface in a generally lin-r contact with tJie camming curiaes. The fitting components, and particularly the separable ferrule, are preferably but not necissianly ci.se hardened. The new fitting is -sspecially useful as a stainless steel and other metai tub? fittings, iUhou}^ the invention is not limited to any particular class of metals. In accordance wi*:;) another aspect of the invea-ion, the fitting may include a self-gauging feature to indicate suj;acient pull-up and to prevent excessive tiglUening of the components.
In accordance with additional aspects of tlie invention, the camming surface prciile is substantiiilly mc^jfied from prior art single ferrule tube- fitting designs by incorporating a :Ue';rp camimng ajigle in the lange of about thirty-five degrees to about sbcty degrees. The stesp'ir camimng angle produces a better tube grip than prior art single ferrule tube fittings, pajtic'Ularly when ihc ferrule is hardened to be at least about 33 times harder than the tubing maedal Tlie ferrule may also be designed Viith a geometry that facilitates a radially inward hing'ng action during pull-up. This hinging action improves the tube grip and seal as compared to pr.or single ferrule tube fittings.
These and other aspects and Stdvantages of the present invention will be apparent to th3s.e skilled in the ait from the following description of the preferred embodiments in view of the accompanying dr^iwings.
Brief Description of the Drawings
The invention may take physical form in certain parts and arrangements of parts, pref*:rred embodiments and a method of which will be describee in detail in this specification and illustrated in the accompanying drawings which form a part hereof, and wherein:
FIG, 1 illustrates in half longitudinal cross-section aa exemplary embodiment of a tobe fitting m accordance with the invention in a finger tight position;
FIG, 2 illustratef. the embodiment of FIG* 1 in a partially pulled up position;
FIG. 3 illustrates the embodiment of FIG. 1 in a completed initial pulled up position; ard
FIG* 4 illustrate?} another embodiment of the invention.

DETAILED DESCRIPTION
Stainlry:- Steel ■SubsaatO;
[OOOr llic present invention is applicabb to all types of stsinless steels. As well knc^^'n, stainless steel is a steel which forms a coherent chromium oxide coating when exposed to air. To this er.d, most stainless Steele contain at least about 16 vi.'vi chromium Prefen-id are 3ub Form;3tiim of Metal Oxide Layer
[0002; As indicated above, low temperan::re carburization of stainless steel parts, when done usin;; an oxygen containing gas, leaves the cr^rburized s\irface catr>'ing a layer of soot a^ well as a porois., i.e. non-coherer;t, adherent metal oxide layer. Nonnally, this metal oxide layer is compo.sed of chromium oxide, although other metal oxides can be present. In conventional practice, this metal ojtide layer is removed together with or indej^endently of the soot layer which also fcrras. In accordance witlr the present invention, however, this heavy metal oxide layer is left on at least a ponion of the part surfaces, since it has been found that this metal oxide layer sen't^s ai; an ideal anchor for bonding subsequently applied solid lubricants.
[0003. The pmicular condition:; under which this metal oxide layer can be fonried are already well kiown in the art, since this formation occurs to a peater or lesser degree during low temperature carburiz£ktion when carbon monoxide or other oxygen containing gas is present in the carbiirizir.g gas. Especially heavy (i.e., thick) metal oxide layers can be obtained by using carbon monoxide as the predominant carton source for carburization. Carburization gases in which c:irbon monoxide accounts for at least about 75%, S5%, 95% or even 100% of the carbon souioe for carburization aie especially interesting.
[00041 Othei approaches rhat can be used for fostering tlie formation of this rnetal oxide coating during carburization are small percentages of CO2, H^O, etc.
[00051 Normally^ the oxide layer will be about 200 to 400 Angsxroms ttiick, although thinner and thicker layers can also be used so long as they serve to anchor the applied solid lubricant in the manier indicated herein.

Ei^jll^;*.'r'^ I of So .uLayei
[OOOCj RemoA^al ol'tl)? sooi layer which foims during low tenipcramre carbmizauoii can be done in a xnventional manner. For example, washtng the carhurized part aqucou?];/ with ultrasonics will elfectively remove all or substantially all the soot without adversely affecting the metal oxirli layer in any significant way
glolid Liibricairs
[0007 i In accordance with, the present invention, a solid lubricant is applied to the metal oxide laycj fmned by low temperature carburization.
[OOOS i For this puqz'Oise, essenually any solid lubricant can be used. Many such solid lubricants are \^x\l knowTi. Some are particulate in form while other are supplied lai'ger in size. A few exauip^es arc graphite, molybdenum di;;ulfide, tungsten disulfide, UHNIWPE (ultra high mol';ci.hir weight polyetl/v'lene), halogenatod polymers such as PFA, PTFE, PCTFE and the like. Exarapks of comme»'cially available solid lubricants include Dow Corning® 321 Dry Film Lubticmt avdlable from Dow Coming Corporation of Midland, Michigan and Slickote^' Dry Lubt-100 available from Trans Chem Coatings, of Monrovia, California.
[0009. These lubricants* can be used not combined uith ano':her material, or mixed with another material such as a lesinous carrier or the like. In addition, they can be used in essentially any solid form including powders, gi'anules, pastes and bulk solids.
Apolii'a'.ion of Solid Lubricants
[OOlO'j The solid lubricants of the present invention can be applied to the metal oxide layer by any standard method such as by hand, sv.ch as by rubbing, by aerosol or air spraying or by autc;n;-.tic eqiipment. Any coating thickness can be used which will provide lubricating prop;riies. Solid hibricant thicio^esses exceeding standard class 2 thread cleaiances are usually not required.
[0011] If appropriate, the lubricant can also be heated to enhance its adhesion. For example, some labricarts, especially those supplied ia a resinous binder, can be heated to effect cure of the bindtr. For example, Slickote® Dry Lube 100 can be heated following manufacmier's instrjctions tc> 300"" F for 1 hour, for example.

■
[OOlIIj The present invention can ht \iscd anyv^^here it is dssirabk to enhance the surface slipperiness crf cast* hardened, corrosion resistant stainle::;$ steel parts. Particular examples are nuts, bolts, g [001^ j The present invention finds particular utility in making stainless steel nuts having case harder ed threads lubricated in 'c.ccordance witli the present invention. Because of the lubricant, less pull-up torque h required during tightening as comp£.red to a similar case hardened nut without lubricant. Moreover, this enl)anced lubricating effect is retained longer than a lubricated nut madt in <. conventional manner i.e. by removing the metal oxide layer before applying lubricant because anchors in place even after repeated u5e. thus nuts rr.ade accordance with present invention can wltlistand fitting remakes looscnings and retighfenings of nut without being removed or replaced.> [0014] Although only a few embodiments of the present inv.^,ntion have been described above, it should be appreciated that many modifications can be made wid:out departing from the spirit and scopa of the invention. All such modifications are intended to be mcluded within the scope of the present invention, which is to be limited only by the following claims:

DetaileH DgscripUon of the Invention
Li accordance then with one aspect of the invention, a tuht; fitting is provided hi!v:.ng a lube gripping device that initia!l> is integral with one of the coupling elements and upon pi..ll'Up scparares i:herefrom to function a*, a single ferrule fitting. In the preferred enibodimeat, tbi :ube gTippiii;£ device or feiTule is integrally fomi&i with a female threaded nut and 15 attached th sreto by a frai:.gibk thin web portion that breaks as the femile cnxns initially against a camming surface of tlie r.:ia!.e thccaded component. As a single ftniT.le after separation, the ferrule acts ajjainst tl- e steep canmiing angle surface of a male threaded body- The steep camniJr.g surface ai;gle is particularly advantageou5 when tlie hardness of the tube gripping device has a ratio of at least about 3.3 tinges greater 5Lnd preferably at least 4 times {jrealer to the hardness of the tnbing U3.Uerial.
Although a number of aspects of the invention are desciibcd herein as being in':orporalcd into the ^emplary embodiments, such description should not be coashiied in 3 limiting sense. 7or any particular application the various aspects of the invention-may be used as iC'^uircd ji differtint combinations and sub-combinations tliereof. Furthermore, although the ptjsent disclosure describes and/or illustrates a number of design choices and alternative embodmunts, such descriptions are not intended to be and should not be constx-ued as an exhaustive list of such choices and alternatives. Those skilled i:a the art will readily appreciate and understand adaitional altemarives and design choices that are within the spirit and scope 01 the inveniion as set forth in the appended dainis.
Although the various embodiments are described herein with specific reference to th: fitting; coraporents being made of stainless steel, and in particular 316 stainless steel, such description is inter.dcd to be exemplary in natiu-e and sliould not be construed in a limiting sense. Those sklled in the art will readily appreciate that the invention may be realized using any number of di£ferei:;t types of metal materials fur the fitting components, as well as metal tubing m.Uerials, including but not limited to 31(5, 316L, 304, 304L, any austenitic or ferritic stainless st.i;el, any duplex stainless steel, any nickel alloy such as HASTALLOY, INCONEL or MONEL, any precipiution hardened stainless steel such as I7-4PH for example, brass, copper alloys, any carbon or low alloy steel such a^ 1018 stesl for example, md any leaded, re-phosphorized or re-sulphuriztid steel .such as 12L14 steel fi^r example. An important aspect of the choice of materials is that the tube gripping device preferably should be case or through hardened to a ratio of a: least about 3.3 and preferably 4 or mors times harder than the hardest tubing material that thi: fitting will be used with. Therefore, tlie hibe gripping device need not be made of the same

ma:cj-ial as tJie tubing; iuelf. For example, as wi)l be discussed her^inbebw, the tube grippmg di:\ ic5 ;nay te selected from the stainless steel materials noted above, or other suitable materials tbiit can be c ise hai-dencd, such as magnesium, titanium and aluiumun, to nam*i some additional eximples. Furthennore, the frangible feature of the tube grippirig ring and female threaded n»it mjy iihio be realized in uoc-mctal tube fittings.
Witii refeience lo FIG, 1, the present invention contemplates a Uibe fr.tLig 50 in WIMCII iher^ are only two discrete components prior to assembly, n:iniely a female direaded nut 51 ai^d a mule threaded body 54. The nut S2 is uubs;antiaUy different iiom tlie typical nut used in a prir art fsmile iy:,)Q tube nrtlnjjs. The tody 54 may be the similar in general de5ign as a typicil body used in prior fittingJi, however, s^ will be explained further herein, it is preferred but not viecessaiy tiiat the body 54 also be optimized for proper ma Not* that in the drawings the fittings are illustrated in longitudinal cross-section but cnly half of tlie section is illustrated, it being understood tliat the other half is identical and oiuitxd for clarity and ease of illustration. In all of \ho illustrations herein, various gaps and dLntinisions ire somewhat exaggerated for case of illustration.
*rhc body 54 is a generally cylindrical main body 56 that hai an ii:tcgral extension or c.id 56a The end extension 56a may be a hex body, for example, or piirt of another ccm^jonent such as for example a valve body as noted hereinabove. The main body 56 may be machined fiom the s;ime stock as the end extension 56a or may be otherwise attached such as by w:lcing or other suirable technique. The body 56 includes a first central longitudinal bore 58 tliat is apprjpriaiely sized to closely and slideably receive a ttibe end 13. The first bore 58 is scm'^vhat larger in diameter than a coaxial second bore 59 tb^at exte^ids through the t;nd e> tc nsion 55a of th€^ body 54. Of course, if the fitting 50 is a closed end coiuiection, the inner bore 59 would not be a through bore.
The tube end 13 preferably bottoms against a couriterbore 60. Tte body 56 is n.achincd t>r other-j^ise formed with extejnal male threads 62 that threadably mate with conssponding female threads 64 formed or machined in the nut 52. It is contemplated that in oixlcr to avi)id inadvertent nuxing of old and new style body and nut parts with prior art fitting component;, that tlie thread pitch on the nut and body of tlie present inventiorj may be Rub:it2jitiall/ different fi-cm the thread pitch values of prior art fenule-type; tube fitting nuts and

bo\3ie::. This will avoid interchange problems arid also 3llo^^s for a course pitch that provides hicjv axial stioke wiili reduced nut rotalion for complete pull-up. For example, a fitting that incoq-.oi-alcs Lhe present invention may ujie course pitch tlu'eads t]iat provide sufficient axial displacement to achieve proper pull-up in a half aim. A ^ypical pnor art fitting by comparison is pu! c(!-up witb 1 1/4 to 1 Vi lums. Nothing hov.^ever prevents t}.ie desiijner ftom making the thread plt:l'i any value suit Tlae central body bore 58 is preferably although not, necessaiily formed with a sli,=ht radially iuwsjd :apcr a relative to the k-ntitudinal axis X (FIG. 1) of the lube end 13 sach th?.u tlie diameter of die bore 58 clecieases radially in tlie axial direction tov/ards"; the ccuutcrbore 60. "vot example, this taper may be about 2" to about 4°, althou^Jh the selected angle is not particularly critical. The bore 58 diameter ai; tlie counterbore shoulder is just slightly less than the oiter dicroeter of thc'^tube end 13. In this marmer, the tube end 13 has a slight radial inliirfsrencc ::it of a few thousandths of an inch for example witli the bore 58. This interference belWLtei the ;)ore 51} and the tube end 13 provides an anli-iotatlon action to help prevent tl\e tube t:\Ci 13 frotr rotating during pull-up. This also reduces residual torsion stress that may be induce*! into the tube end due to rotation of the tube gripping element (80) during pull-up. The tu'te end 13 does not necessarily have to bottom completely agndast "ie counterbore shoulder 60, Tills ..s because the interference fit helps prov'.de a good primary seal between Lhe boie 58 and the tu:e ttxi 13, The iutrrference fu also helps -mprovc the tube grip by Unc tube gripping element (8(0 i)y axiaJly holding the tube end stalionaiy during pull-up so that the fiill axial displacement of th.t tube t;rippinfe element (SO) is used for proper deformation x\d tube grip rather than any loijt i:xia{ mction 0: ruovement of the tube end during tightening. The taper of the bore 58 may cxiend gradually along its entire axial length or a shorter axial portion adjacent the counterbore 60
The m:t 52 includes a first central bore 70 having a first diameter Dl relative to thr Icmgitudinal axis of the fitting SO. Tlie nut 52 also includes a second bore 72 having a second dicmjter D2 relative to the cenfal longitudinal axis of tlie fitring 50. In thii embodiment, the Cisjnsrer D2 is less than the diameter Dl. Fuittiermore, the diameter D2 is sized so that the bore 7:: d::f5nes a generally cylindrical wall that receives the tube end 13 (FIG. 2). The first bore 70 lecmiaates a:: a location that is axially spaced from the nui back end 74 to form a trepan 75, such that iie nut 52 include3 a radially inwardly extending collar 76. The collar 76 is generally

1
defineJ by the back end wall 74 of the nut 52, the smaller diameter bore 72 and ihe larger
diarae:e;:bore70.
In accordance with a significan: a^spect of the inveiiticu, the rut 52 includes a tube grippiiij; device 80 that extends axially mwa;-dly m a somewhat cacitilcvered fashion fiom the cellar Tt"). The tube g-dppmg device iti this e:s ample is in the gftncraJ form of a gripping nng 80 mcl irclude^ lUi inntr horz 82 that defines a subsiiiitially cylinriticul v/all that closely receiver, the tuu': end 13 (FIG. 2). Tac diameter D3 of the bore 82 maybe tfi^ SJuTie a5 or different from the diajnttter of the second nut bcie 72. The cylindrical Vr'all thai defines the gripping ring bore 82 eAlunJs axial y from a tapered front or iiosi portion 84 of the grippin.g ring 80. The nose portion
84 :.nt;ludc3 a..i axially vapered outer surface 8o tJiat increases in the radial dimension tcwzrds the back £;nd of the rini; 80. The tapered outer surface 86 extends from a generally radial front end
85 of die gripping device 80. Tlilii generally radial fiont end 85 joins to tiae inner cylindrical bore 82 ai. a preferably :iharr»^ comer 87. Alternatively, however, there may be provided a cir^UJcriierential recess or step or notch or other geometry (not shown) in the front end of the ring 80 having a *iiamctei that is somewhat larger tlian the diameter D3 and axially extending from th€; fei)nt cud 85 iowAids ihe back end 74 of the nut 52.
The Tapered surface 86 joins thj front end 85 preferably by a ladius portion 89 and at its a>:ial oiposiie cr.d by a radios 86a to a {generally cylindrical portion 91, which in tuni join^ via a radius 93 to the trepan 75.
It is noted at thi;i point that the various geomiie/y chsjracterisdcs of the lube gripp ng devxe 80 (such as, for example, the; various recesses, notches;, tapered portions, radius portions and so on) are selected so as to effect an appropriate radially inward hinging action as will be further explained hereinafter Accordingly^ the geometry of a tube gripping device 80 wiil he deter.'nintMi by the characteristics of the material of the tubing such as hardness and the fittinij conip In accorddiics with another ai.pect of the invenrion, the tube gripping device or ferrule 80 is attached to the female threaded rrat 52 by a thin frangible web portion 95. This web po .tion breaJcs (as illustrated in HG, 2) when the femile 80 ciims initlaUy against a canuning suifacc (88) during pull-up so that the tube gripping device or fcnrule becomes a separate piece

and ftinction^ with Uu: nut aiid boJy in effect as a single ferrule fitting. The sef>arated ferrale 80 hy:> a bixck cr.d 150 th:it is axially driven by a radially inwardly e-xlcnding wall 152 of the nui 52 th:i S'^rves zs a drive liurface for driving the feirale 80 forward against the caniming surface for corjpicting aa initial pull-up. Th.c frangible •A'eb portion 95 is preferably designed so that upon 1 S(rpar:itioii of thtf dtvlce SO from the nut 52, the surface 95a that is exposed along the break line docs aot inurfere wich ihe drive &'iriAcc 152 of this nut dujing farther pull-up to complere the asssn'.bly. As used b;reiii, the te:n:is "tube gripping device" and '*fei-rulc" or "single fiin-ule" are us:d :nterchangsabLy when referring to ihedevice 80 after separation from the nut 52.
The ferrale 80 is caachiaed with tlie feuigible web 95 portion by forming a radial grcove 154 t.iat is an^jled generally toward ths inside of the female tlireaded nut 52. This groove 154 f jrms the back cud 150 of the ferrule 80 and also the radia] wall 3S2 of die nut that diive the fei'Aiit axially againil tiie camming sui-face after the fenxile 80 separates from the nut 52. Prt;ferably bat not ntcess^ly the wall 152 and the back end 150 ;ire machined at an angle of aboul 75" degrees or so relative to the tube bore axis X, altliough this angle may be different depending on the particular application. The^e surfaces 152 and 150 tnay be contoured lo reduce galliiig and torque if jjo required.
With reference to FIGS. 1, 2 and 3, the tapered nose portion 84 initially engages an a:.;iidly tspcrcd ca-truning surlace 88 that forms an opening to the tube bore 58 In the main body 56. Tte taper'3 Upon a completed pull-up, the back end 90 of the body 54 contacts the trepan 75 which serveii as a poyitive stop against over tightening. Should remakes be desired, the back end 90 n .ay be socially spaced from the trepan 75 upon a completed fir;:t pull-up. Proper puU-up in this c;a3c may be verified using a gap gauge or other suitable technique, as is known.
The tvibc gripping ferrule 80 is shaped to effect several important functions of the fitting 50. The feirule 80 must, upon proper puU-up, provide a fluid-tight primary seal against th.-5 tipercd canuniag surface 88. This seal may be a primary outer seal for the tube fitting 50, or n:.ly b2 in effect a se:;ondary or back-up seal to any seal formed be^vcen the tube end 13 and the bcdy S4, for example along the l>ore wall 58 and/or tiie counterborc 60. The separated ferrule 80 al:w3 will foim a primary seal at the location where the femilc 80 bites into the outer surface of

thci tube end 13 in the area where the cylindrical bore 82 of ibe ferrule 80 engages the vibt end ^ outsr surface, Again, this primary seal may in effect be a back-ap or secondary seal to any seal formd by the tube end 13 agaiiiat the body 5i4. In any event, the ferralc 80 must form primary seals aj;ajnst tlie C2na::ning surface 88 and the outer surface of the rabe end 13, In addition, the fci^-izl: 80 niiist adequately grip the cube end 13 so as to maintain seal integrity under pressure, ten.p'.'tuturc ind vibrii-tion effeclsi, and to prevent the tube end fruui separating from the fitting
unilei such c;irc\imstajxeij.
In o.rd'i.r to achieve a fluid-tight seal and tube gapping action, the ferrule 80 is dewgied to oe pla;iti::ally deforcied and sws.ged into the tube end upon completed pul!-up, a^ ill.itiaved in FIG^ 3. This result is acldeved by designing the ferrule 80 to have a hingiug action wherirby the tapered nose portion 84 is not only driven axialiy forwiird as the nut 52 is threaded onto iha body 54, tut also is radially displaced or driven into engagement widi tl-ic outer suiface of this tube t:nd 13 wall. iThe forward end 92 of the nose portloQ 84 is thus compressed and embedded into the tubing wall with a rcsultajit stress riser or bite in the region designated 94 in FlO- 3. The front'end bite 94 produces a generally radially extending wall or shoulder 99 form-i'd out of the plastically defonned tube end material lb; shoulder 99 engages the enjbedded &Dnt end 91 of the gripping ring HO to thus form an exceptionally strong mechanical re'^istiTice to lube bb^v' out at higher pressures. The embedded ftont jnd 92 thus provides botli an • e-xce'lent seal and t. sxong grip on the tube er^d 13. The ling SO [^ fiither designed to exhibit the af:ire .mentioned radially inward liinging action so as to swage or collet th*j cylindrical wall 82 ag;iiri3t the tube end at a location axialiy adjacent or spaced from the stress riser bite 94 and gdierally daiignated with the numeral 96. This swaginjj and collet -effect substantially enhances thf tube gripping function and serves to isobte the rinbcdded nose portion and bite 94 from the cf["cc*:s of down tube vibration and also temperature changes.
Although tlie present invention is described herein in the various embodiments as effscing an embedded nose portion and attendant swaging ac-tion, tliose skilled in tlie art will appn:ciat« that in KOrie applications such rigorous design criteria may not always be required, paj-titularly for fitiiags that will be exposed to moderate temperature, vibration and pressure eftec\5. ThfiTefore, the additional design aspects of the nut, body and gripping m\g set forth hfii-ciii as preferred embodiments should therefore not be construed in a limiting sense but rather as selectable eriiajicdtncnts of the basic concepts of the invention to be used as required for palicular application?!.

In o.:dar to achieve the desired swaging action aj^d tube grip» the ferrule 80 is designed to C'Xhibit thi hinging action that allows the Upered nose portion 84 and the central or mi'1-portion (as at th-; region of the cylindj-ical bote 82 or th.e region designated 94) of the gi-jpug rinf; 80 to be radially inwardly compressed ar, it engages with the tapered camming moutli 88 o;*the body 56. This hinging action is also U£ed to provide a significant radial di:-,pl.ic2ment and conrpression of t)io cylindrical, wall 82 to swage a central or mid-portion of the feraiic 80 body onto tte tube end 13 axially fidjaceut to the stress ristr 94. In the embodiment of F1G!:<. tie hinj5il.g action is faclliuted by providing a prefeired althougli not required radial iicer circumferential notch that axially positioned between the cylindrical portions and nou:h i:i suitably shaped to penni femile plastically dcfonii collapse in controlled manner fio as radially compress wall agalost die tube end with lh disired collet ejyect. pardcular geometry of gripping ring will thus be designed so thit i.s m:t further threaded tightened onto body after ferrule separates ihs f hinges deforms grip seal botti against cni iind tapered camming mouth standard design procedures such finite element aralysis may uned optimize based on vaiiable factors tht t.ibing material tubing hardness thickness reijuircd pressure temperature viftntion peiformanc characteriiitics.> Proper deformation of the feiiule 80 may ftiitinjr be controlled by selecting an apjTTupriate <:ontour for the tapered surface this enga.ges nose of feiru.c aid theixfore wll in part determine timing and mcmner how feirule hictgus. com plastically deform. to properly embed portion bite into tubing zlso provide desired collet o: swaging acticu. furthermore contour cajniaing sa may be de achieve seal between ferrule portiijn tlie is important overall performance fitting as he provided tube end> The nat 52 widi its integral tube gripping ferrule 80 may be manufactured by stindai-d ma:hining cperaiions, and will t)pically include a trepan operation to form the outer contour of tie ring 80. The otiier features of the nut 52 can be realized as well with known mi.clining operation:;, Preferably but not nec*jssarily the nut 32 includes wrench flats 102 to pti.-mit tl:e iser to tii^hten tiie nut 52 onto the body 54, Thoye sldlled m the art will readily apprxiate tfiat use of the fitting 50 only requires relative rotauon between the nut 52 and the

boJy 54. such that cither compDnen: or bcth may be rotated as required duiing a pull-up opcrauon.
V/e have found that it is highly ilesirable for the canuning sunacc 88 to form a cirrjiiin^ angle G of ahout 35^-60*' relative to the longitudinal ^%U X of tlie fitting 50 and tube end 1.5. Mote pref In the excrnplary cmbodimen!:s herein, tiie nose portion 84 includes the radius pojtion 89 thai transitions to the outer tapered surface 86. This outer surface 86 tapers generally at vji angle tliat is not as steep as the angle of tlxe canuning surface 8U. The tapered outer surface 86 prcferablv' Upere axially with an increasing radial dlinensioa towards the back end of the gnpp: ng ring 80. Thi.'i tapered outer portion 86 contacts the camming surface 88 with, in effect, a generally najTOW zone or line contact upon jmll-up that has high stress and material coining to allow the froi:t end of the gripping ring 80 tc coin into the camming surface 88. Therefore, the tern 'generally naircw line contact" is not intended to preclude an area of contact between the ou'er u.pere
coalai..t of metal buriiii:bed on metal to effect c. gas tight primar>' seol between tiic tapered surface 86 ^ind the canming surface 88.
It is important to note that the use of a paiticular caijuning angle is not dependent nccissadly on the contour of the surface 88. In other words, thr aii?;le of interest is the angle at wbicli the fr*)ni end of the gripping ring SO contacts the camming sxirface R8 to fom\ a seal thc'.'f^'it. Thu>, t^ie ciiJiming surface 88 may indeed be made with a ncn-frtisto-conical contour, bir: tiic seal is still forncdby the Eroiit end of the ferrule 80 contactirg a steep angled f.urface 88. Adiirional .ompouac angles or contours of the cdnvming surface 88 may be unrd to better fac: U:ate the iiinginis; tction and tube bite achieved by the ferrule 80-
Wbeth.;;r th-5 caninaiiig surface 8!? is formed &s a coj:tpoiind ai:iglcd surface with adoit .cnal angled pon:.ons that arc steeper or shallower to faciiit2iie the hinging acion and bite of th The steeper carnming surface «mgle has llic addiiitvoal benefit that the note or front po 'ion of the lube gripping device 80 may b*: formed witli subs:ancially more nia^s as compared to if :he firort portion had to engugs a shallower camming surface angle as in the prior art single ferva.e and gripping ring desigr^. Tnis added mass, along with the hinging action, tends to pcjjii.on a sibstan::al!y greater mass of material at or near t?ie location of the tube bitt; 94. This sij^nfftcantly strengthens the tube gripping device in resisting pressure and also strengthens the cc'vle: effect that isolates the bite fiom vibration and temperature effects, as contrasted to jjrior arc sii.-gl2 fsrrultj or gripping ring designs. The hinging action also results in the back end of the tube giipfing de\ice (i.e. the end opposite the noiie erjd 84) from contacting the tube end, so that the entin: tube gripping' dsvice is in iaial and radial compression.
In general, for a tube grippmg device suclri as a ferrule to embed into, bkt s^nd grip th
tht pr'or art allows a fi:trule to cmbsd into a a.be even when the ferrule It only moderately harJer thaji (.!<: tube under these circum3t if the gripping device were only rr l than tlie end. would bs unable to adsqu giip t for a steep angle canuiiing siuface btc of substantially shorter axial movement rube ducin. pull-up caused by steeper cairuning imgle. kcwever in accordance with present invcn:ion b niakiag rubs jrripping significantly hinder otbby ane.le cainnr.ng surface may be used or.d is effective cau-: ihc adf qiai-ely bite into envl grip tubs.> The steeper camming angle 0 of the present invention also results m a much sh:rt!:r di3taj\ce of u;t.ial displacement of the ferrule 80 during pull-up. Consequently, the nose poiticiji 84 ^^ill need to be radially deformed and compressed into tne tube end 13 -with a much shfirt::r axial displacement or sliding movem;ut. In order to acJiievc the proper tube grip thcHj th)! ft;rTule 8(1 is prefeiably-case hardened to 2 hardness of at least about 3.3 times harder than the tubin.j material For »::xample, if the tubing material is stainless sieel» it may exhibit a hardness of up tc about 200 VLcVers. Therefore, in accordance with this aapect of the invention, when the fittini; 50 is used with such hard aiaterials, the tube gripping device should be hardened to a rstio of at lea^t about 3.3 times harder ihan the tubing. More preferred, the tube gripping device should be hixdened to a ratio of at lease 4 tiines harder than the tubing. Still further, the entire Eiipiar.g ring SO ^ecd not be cass hardened, but rather only tlie nose porti(ui 84 may be selectively case hardened.
In a:coriince with this a-speci 0: the Lnventiori^ all or pniz of the nut 53 and body 54 u.ay be ihrougli hanlencd or case hardened to Increase the tube grip of the fitting 50 when U!i;d witli lumler tubing materials such as siaia!e':s s:ee!. Suitable case hardening processes are fuly descrii)ed m United States Patent Nos. 6.165,597 and 6\093,3C3 and copending patent a[)phcaticn serial \:o. 09/494.093 filed on January 28» 2000 for MOD.tFII:D LOW Ti'MPEBA^:iJRE CASE HARDEMWG PROCESS, issued to tlie assignee of the present ir//e.iiti,on, tlie entire disclosures of which are fally incorporated herein by reference. These processes produce a hardness of the tube gripping device of iibout 800 to 1000 Vickers or higher without coniprcmidng the corrosi-:)n resistance of the fitting. Other case hardening techniques h':w:;ver may be used as required. Case hardening of the tube gjippjng ring 80 allow^ the ring 80 to a:iequate.y grip ii.nd seal against tubing materials such as stainless steei including duplex sudnlesws sttel Thcj above rcfsrenced case hardening patents have an additionaJ benefit of

prcvR.ing suifaccs on the ring 83 that reduce or prevent galling bctv/ccii the ring 80 (which rot3tc:i with die nut 52) and the tubing.
Vario'xs lubricarus may al^ be used v/iih txie nibc giipping rin£ 80 to reduce gallin.j and residual touion such as, for cx^mpk, PTFE gf^asc'S, and grease*; containing rnc yldenum disulprude or tungsttm disulphidt;.
Case h:;irdening tecl:niques typically will resul: 'v^ tlni cnliiQ nut 52 and integral tub) f^ippin^ ring {10 to be case hardened. Wien the c?^e h:irdenir.g is performed on stainlesr, steel, for exi:mple. as in tiie abo'/t; reference.! patctus cr patent application, an adherent oxide skill i^ formed. In aa<:ither embodiment of the invention a solid lubricant m.iy be applied to tlie llirtiac>s of the stainle;>s; stael nuts 52 to reduce firiction and tlie hence puU-up torque during tigfiltning. .\ny sclic lubricant can be used for this purpose and msiny such solid lubricants are weU iaiown. A fiw examples are graphit*, molybdenum disulfide, tungsten disulfide and UK\:UTE (ultra bigli niolecular sveight polj'etiiylene). The:ie lubricanfi can be used neat, i.e. not combined with another maur.al, or mixed \vith another material such as a resinous carrier or the lilie. In zidition, they can be used in es&c:ntiaUy any solid fomi including powders, granules ana pistes.
Solid lubricants of this type ;arc "well knov^n .comn:.ercial products. Examples inclU'.le Dow Corniiig'& 321 Dr)* Film Lubricant available from Dow Comins Corporation of MiilsJid, Miclugit;. and SIickotc*S Dry Lube 100 available' from Tnms Chem Coatings, of Mctniovia, California
Thc5e lubricants can he applied by any standard meLhcd such as by hand, by aeros:)! or ail sprayin}! or by automatic cquipmcut. Ajiy ccaririg cliicijiess can be usc In a pg^rticular embodiment of the invention, a dry lubricant as described above is usod on stair less st^el nuts 52 which have been subjected to low ten-.perature carburization \ising caibcti moncxide as i:he carbon £.ourcG. Stainless steel is stainless because of the thin, coherent cbj'OiMium o):ide film which inherently fomis when the steel i3 exposed to air. Low temperature cajbirizatior. of stainlcb'S fiteel parts, such as (hose made from AISI 316 and 316L stainless steely usually leav^ss the pa.rt surfaces coated with a layer of soot. Before use this sooc is usually

rcaio\'cd by v/ushing. WTiea carbon monoxide is used as tlie ca;:bon source in low terr.psrature cart'Urizatiort, not only does soot, ibrm but in addition a heavy oxide tum also form3. This heavy oxnle f.lm ii consildttrably different frooi tlie coherent chrorriurn oxide fiirn which makes sia:nl<:s:> steel stainlesii in that it is. thicker and not coherent. Th£;refore, this P.Im is also removed belbrr use to uncover the part's csTburi^ed surface.
In accordance with this particular embodiment, tl\\;5 heavy oxide film is not rcr.:o',ed before apf'lication of tlic solid lubrictint. Rather, il is left on the carburized part sur ace:;, or et least tha portions of the carbuiized surfaces to be lubricated. In accordance tliis paj'-icular erobodimeni, it has been found that the naturally porous stiucture of this heavy oxide skiji iicts 05 sn anchor for binding the lubrica:it to tlie part surfaces. As a result, Ihti lubricant is more adherent than would otJiei-wIsc be the ca^e, and hence is able to v/ithsrand repeated fitting renialnes (i.e., loosening and re-tightening of the nut) without bcir^g removed,
FIG. 4 iltvitrales another embodiment of the invention in which all elei7ienl5 are ge-erilly the same as the prior embodiment vitli one variation. In the frangible web portion 95, a srcis concentrating notch 300 is formed therein. In this embodiment the stress concentrating noicti JOO is formed as a generally tight radius thai creates a thinner web of material 302 Co prcmote a rapid clear, break of tt.c ferrule 80 from the nut 52. The break thus occurs as a resuh of a minimal span of rotation of the nut 52 shcnly past finger tight posi^lon. The shape of the br:al: is alsr- less rai':ged. Other shapes of the notch 300 may be \ised as required includiiig cllrptical, tri^tngular aiid so on for example.
Tlie ir^vemicn ha.-; been described widi rci'crencc to the preferred embodiment. Cliraily, mociificattons and alterations will occa* to others upon a rcadijig and xinders;anding of this specification. U is intended to include a]l such modifications ar:d alteiaticns insofar as they ccmc within the scope of the appended clairnr. or the equivalents tliereof.

A stainless steel part substantially as herein described with reference to the accompanying drawings.
A process for enhancing the slipperiness of the carburized surface of a stainless steel part substantially as herein described with reference to the accompanying drawings.

Documents:

1214-chenp-2003 abstract granted.pdf

1214-chenp-2003 claims granted.pdf

1214-chenp-2003 description (complete) granted.pdf

1214-chenp-2003 drawings granted.pdf

1214-chenp-2003-claims.pdf

1214-chenp-2003-correspondnece-others.pdf

1214-chenp-2003-correspondnece-po.pdf

1214-chenp-2003-description(complete).pdf

1214-chenp-2003-drawings.pdf

1214-chenp-2003-form 1.pdf

1214-chenp-2003-form 18.pdf

1214-chenp-2003-pct.pdf

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Patent Number

228577

Indian Patent Application Number

1214/CHENP/2003

PG Journal Number

12/2009

Publication Date

20-Mar-2009

Grant Date

05-Feb-2009

Date of Filing

06-Aug-2003

Name of Patentee

SWAGELOK COMPANY

Applicant Address

29500 SOLON ROAD, SOLON, OHIO 44139,

Inventors:

#	Inventor's Name	Inventor's Address
1	BENNETT, MARK, A	18436 SNYDER ROAD, BAINBRIDGE TWP, OH 44023,
2	WILLIAMS, PETER, C	3495 EDISON ROAD, CLEVELAND HEIGHTS, OH 44121,

PCT International Classification Number

F16L19/14

PCT International Application Number

PCT/US02/03431

PCT International Filing date

2002-02-06

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/266,735	2001-02-06	U.S.A.
2	60/329,943	2001-10-17	U.S.A.