Title of Invention	"A PIVOT CONNECTION HAVING A CYLINDRICAL LAYER OF SELF LUBRICATING PLASTIC"
Abstract	The present invention relates to the construction of a self lubricating shaft or pivot pin suitable for operating at high temperatures such as tenter frame apparatus. The pivot connection between a first component having a radially inward facing cylindrical surface and a second component having radially outward facing cylindrical surface in confronting relation comprises a recess formed in one of said cylindrical surfaces. The said recess presenting a roughed up surface and a thin cylindrical layer of self lubricating plastic preferably is polytetreflouraethylene having a melting point greater than 600 degree Fahrenheit, molded in said recess presenting one of said cylindrical surfaces in radially confronting and bearing engagement with the other of said of cylindrical surfaces.

Title of Invention

"A PIVOT CONNECTION HAVING A CYLINDRICAL LAYER OF SELF LUBRICATING PLASTIC"

Abstract

The present invention relates to the construction of a self lubricating shaft or pivot pin suitable for operating at high temperatures such as tenter frame apparatus. The pivot connection between a first component having a radially inward facing cylindrical surface and a second component having radially outward facing cylindrical surface in confronting relation comprises a recess formed in one of said cylindrical surfaces. The said recess presenting a roughed up surface and a thin cylindrical layer of self lubricating plastic preferably is polytetreflouraethylene having a melting point greater than 600 degree Fahrenheit, molded in said recess presenting one of said cylindrical surfaces in radially confronting and bearing engagement with the other of said of cylindrical surfaces.

Full Text	TECHNICAL FIELD This invention relates to the construction of a self lubricating shaft or pivot pin suitable for operating at high temperatures such as in tenter frame apparatus. BACKGROUND OF THE INVENTION U.S. Patent number 5067214 issued November 26, 1991 to Christopher E. Hosmer and John F. Whaley for a Tenter Framer Apparatus and Method shows a self-lubricating bushing made of a polyamide resin. U.S. Patent number 5797172 issued August 25, 1998 to Christopher Eugene Hosmer for a Tenter Frame and Method discloses tenter frame apparatus of the type in which this invention has particular application. Conventional self lubricating friction or wear devices such as bushings and/or plain bearings are typically composed of a metal housing in which a plain plastic bushing is inserted and secured in a manner preventing rotation of the bushing. Typically a metal shaft is carried in the interior diameter of the bushing. In the case of a tenter frame clip jaw application the currently issued bushings result in the bushing locking down on the metal shaft due to thermal expansion and the bushing wears out prematurely or it locks up preventing the desired function of the jaw. FRIEF SUMMARY OF THE INVENTION Attachment of the self lubricating plastic bushing is achieved by insert injection molding, at high pressure and temperature, a thin, self lubricating plastic sleeve around the metal pin. To enhance adhesion and provide sufficient material for wear, the plastic is molded in a groove or recess of a specific depth which has a roughed up or knurled surface. The self lubricating bearing member is thus on the shaft which rotates in the metal housing. Thermal expansion at elevated temperature results in expansion of the internal diameter of the plastic sleeve; however, the roughed up surface prevents rotation of the plastic sleeve. Expansion of the plastic bearing sleeve is minimized by using a thin layer of plastic which has a low coefficient of thermal expansion. The process by which the hybrid steel and plastic pin is produced is also unique and very cost effective. Although CNC turning of the hybrid pin to the desired outside diameter and dimensional tolerance is possible, a more cost effective and dimensionally and surface finish superior part is produced by centerless grinding the outside diameter. The process of centerless grinding metal and plastic simultaneously is unique and requires a plastic that is dimensionally stable and rigid enough to grind properly and not melt and smear or have metal particles in-bedded. A polytetraflouraethylene is preferred for use in tenter frame jaw pins for its physical, thermal, and tribological properties which are required toe achieve a long wearing, stable product with reliable performance. BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention is illustrated in the drawings in which: Figure 1 is a perspective view of a tenter frame with parts separated and broken away for illustration purposes; Figure 2 is an end view of the tenter frame in an assembled condition; Figure 3 is a side view of a metal pivot shaft initially machined to provide two reduced diameter recesses; Figure 4 is a side view of the shaft after the recessed areas of the shaft have been knurled; Figure 5 is a side view of the shaft after a plastic material has been applied to the recessed areas by injection molding; Figure 6 is a side view of the shaft after it has been machined by centerless grinding; Figure 7 is a section view taken along the line VII-VII in Figure 6; Figure 8 is a side view of a centerless grinding apparatus and Figure 9 is a top view of the apparatus shown in Figure 8. DETAILED DESCRIPTION OF THE INVENTION Referring to Figures 1 and 2, the invention is illustrated in a tenter clip 11 which with other clips, are connected in series by a link chain 12 thus providing a tenter chain 13. Tenter chains are provided in opposing pairs to grip the edge of a continuous web of flat material such as woven cloth and to simultaneously stretch the material in a transverse direction while conveying it through a process oven as a finishing operation to its manufacture. The tenter clip 11 is a clamping device which includes a clip body 14, herein after referred as first component in the claims, which is open on one side with a surface 16 for supporting web material being fed into it. The clip body includes a pair of support arms 17, 18 pivotally supporting a cylindrical pivot pin 21 for a jaw 22. The pivotable jaw 22 is operated by an external mechanism, not shown, to allow entry and exit of the web material. The jaw 22, and the clip 11, are designed to automatically clamp and hold the web material. The jaws movement is limited pivotal movement about the axis 23 of the jaw pivot pin 21 which is nonrotatably secured to the jaw 22 by a transverse pin 24 extending through aligned bores in the pin 21 and the jaw 22. Referring to Figures 3-7, the process for manufacture of the jaw pivot pin 21 is illustrated by showing the steps of manufacture. Figure 3 shows the cylindrical pin 21 after the pin is rough finished to a predetermined oversize diameter and a pair of reduced diameter recesses 31, 32 are formed near its axially opposite ends. The recesses 31, 32 having an axial dimension matching the bearing surfaces of the arms 17,18 of the tenter clip 11. Figure 4 shows the cylindrical pin 21 after sleeves 34, 36 of high temperature resistant plastic, such polytetraflouraethylene has been applied by injection molding to the reduced diameter areas 31, 32 of the pin 21. The oversized pin 21 is next machined by centerless grinding to a desired finished diameter as illustrated in Figures 6 and 7. Figures 8 and 9 illustrate the centerless grinding step. The pin 21 is supported by a work blade 41 and is sandwiched between a grinding wheel 42 and a regulating wheel 43. As shown in Figure 9, the pin 21 is guided by work rest guides 46, 47, 48, 49 during a machining operation. In summary, the invention is an improved pivot connection between a first component in the form of the illustrated clip body 14 and a second component in the form of pivot pin 21. The first and second components have radially confronting cylindrical bearing surfaces. One of the pivot components has a pair of reduced diameter recesses 31, 32 which are roughed up prior to application of a layer of cylindrical surface self lubricating plastic 34. The self lubricating plastic is restrained from rotation by the roughed up surface and is in bearing engagement with the bearing surface of the other component. PRACTICAL APPLICATION OF THE INVENTION This application has particular application in tenter clips which are connected in series by a chain to form a tenter chain. Tenter chains are used in opposing pairs to grip opposite edges of a continuous web of flat material, such as a woven cloth and simultaneously stretch the material in opposite directions while conveying it through a relatively high temperature process oven as a finishing operation in the manufacture of the processed material. Wear on the bearing surfaces has long been a problem in tenter clip design because lubrication of the bearing surfaces is impractical, mainly because the bearing surfaces are above the web material and it is virtually impossible to lubricate the bearing surfaces without lubrication spilling onto the web material. Since these bearing surfaces are typically not lubricated, they are made of metal which resists high temperature and are expected to wear significantly. Frequent repair of the clip is required to keep the clips within operating tolerances. The repair of some clip designs require reboring the pivot pin hole and a new larger diameter pivot pin. The repair of clips using replaceable steel bushing are repaired by replacing the bushing and it is often to replace the pin as well. Various plastic materials with unproved strength and wear characteristics and the ability to withstand high temperature have been developed. They have been tried and tested with limited success. Very close tolerances are necessary for proper operation of a tenter clip. Steel bushings for tenter clips are commonly ground on their outside diameter and honed on their inside diameter to achieve the required tolerances. It is difficult and expensive to obtain these desired tolerances with plastic bushings. Most plastic materials have a much higher coefficient of thermal expansion than metals used in, tenter clip components. This tends to cause the bushings to lose clearance and lock on the Pin preventing rotati nn TnfireasingAa^ald^l^rattGe^seJves4tH»ymhlembut creates manufacturing and functional problems. The normal method of installation of bushings is by interference press fit. Plastic bushings tend to deform when press fit, thereby losing most of the interference press fit holding ability. This allows rotation and or axial movement of the bushing, which is unacceptable. The tenter pin of this invention solves all the beforementioned problems in a cost effective manner. Tolerances are not a problem because the plastic bearing material is molded into a groove or recess in the pin and the pin and the plastic inserts are centerless ground as a unit. By molding the plastic into a recess with a knurled bottom surface the plastic insert is restrained from rotation and axial movement relative to the pin. Thermal expansion of the plastic insert is minimized because the plastic insert is radially thinner than that of a stand alone plastic bushing. By forming the thin plastic bearing in recesses in the phi, the pin and inserts can be centerless ground as a unit to a final diameter. This facilitates manufacture and pin installation, We Claim:- 1. A pivot connection between a first component 14 having a radially inward facing cylindrical surface and a second component 21 having a radially outward facing cylindrical surface in confronting relation to said radially inward facing cylindrical surface, characterized in that; a recess 31 formed in one of said radially outward facing cylindrical surfaces, said recess presenting a roughed up surface and a thin cylindrical layer 34 of self lubricating plastic molded in said recess 31 in radially confronting and bearing engagement with the radially inward facing cylindrical surfaces, said roughed up surface preventing relative movement of said layer of self lubricating plastic 34. 2. The pivot connection as claimed in claim 1, wherein said plastic is polytetraflouraethylene. 3. The pivot connection as claimed in claim 1, wherein said plastic is polytetraflouraethylene having a melting point greater than 600 degree Fahrenheit. 4. The pivot connection as claimed in claim 2, wherein said recess is formed in said radially outward facing cylindrical surface of said second component.

Full Text

TECHNICAL FIELD
This invention relates to the construction of a self lubricating shaft or pivot pin suitable for operating at high temperatures such as in tenter frame apparatus.
BACKGROUND OF THE INVENTION
U.S. Patent number 5067214 issued November 26, 1991 to Christopher E. Hosmer and John F. Whaley for a Tenter Framer Apparatus and Method shows a self-lubricating bushing made of a polyamide resin.
U.S. Patent number 5797172 issued August 25, 1998 to Christopher Eugene Hosmer for a Tenter Frame and Method discloses tenter frame apparatus of the type in which this invention has particular application.
Conventional self lubricating friction or wear devices such as bushings and/or plain bearings are typically composed of a metal housing in which a plain plastic bushing is inserted and secured in a manner preventing rotation of the bushing. Typically a metal shaft is carried in the interior diameter of the bushing. In the case of a tenter frame clip jaw application the currently issued bushings result in the bushing locking down on the metal shaft due to thermal expansion and the bushing wears out prematurely or it locks up preventing the desired function of the jaw.
FRIEF SUMMARY OF THE INVENTION
Attachment of the self lubricating plastic bushing is achieved by insert injection molding, at high pressure and temperature, a thin, self lubricating plastic sleeve around the metal pin. To enhance adhesion and provide sufficient material for wear, the plastic is molded in a groove or recess of a specific depth which has a roughed up or knurled surface. The self lubricating bearing member is thus on the shaft which rotates in the metal housing. Thermal expansion at elevated temperature results in expansion of the internal diameter of the plastic sleeve; however, the roughed up surface prevents rotation of the plastic sleeve. Expansion of the plastic bearing sleeve is minimized by using a thin layer of plastic which has a low coefficient of thermal expansion.
The process by which the hybrid steel and plastic pin is produced is also unique and very cost effective. Although CNC turning of the hybrid pin to the desired outside diameter and dimensional tolerance is possible, a more cost effective and dimensionally and surface finish superior part is produced by centerless grinding the outside diameter. The process of centerless grinding metal and plastic simultaneously is unique and

requires a plastic that is dimensionally stable and rigid enough to grind properly and not melt and smear or have metal particles in-bedded.
A polytetraflouraethylene is preferred for use in tenter frame jaw pins for its physical, thermal, and tribological properties which are required toe achieve a long wearing, stable product with reliable performance.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention is illustrated in the drawings in which:
Figure 1 is a perspective view of a tenter frame with parts separated and broken away
for illustration purposes;
Figure 2 is an end view of the tenter frame in an assembled condition;
Figure 3 is a side view of a metal pivot shaft initially machined to provide two reduced diameter recesses;
Figure 4 is a side view of the shaft after the recessed areas of the shaft have been knurled;
Figure 5 is a side view of the shaft after a plastic material has been applied to the recessed areas by injection molding;
Figure 6 is a side view of the shaft after it has been machined by centerless grinding;
Figure 7 is a section view taken along the line VII-VII in Figure 6;
Figure 8 is a side view of a centerless grinding apparatus and
Figure 9 is a top view of the apparatus shown in Figure 8.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1 and 2, the invention is illustrated in a tenter clip 11 which with other clips, are connected in series by a link chain 12 thus providing a tenter chain 13. Tenter chains are provided in opposing pairs to grip the edge of a continuous web of flat material such as woven cloth and to simultaneously stretch the material in a transverse direction while conveying it through a process oven as a finishing operation to its manufacture.
The tenter clip 11 is a clamping device which includes a clip body 14, herein after referred as first component in the claims, which is open on one side with a surface 16 for supporting web material being fed into it. The clip body includes a pair of support arms 17, 18 pivotally supporting a cylindrical pivot pin 21 for a jaw 22. The pivotable jaw 22 is operated by an external mechanism, not shown, to allow entry and exit of the web material. The jaw 22, and the clip 11, are designed to automatically clamp and hold the web material. The jaws movement is limited pivotal

movement about the axis 23 of the jaw pivot pin 21 which is nonrotatably secured to the jaw 22 by a transverse pin 24 extending through aligned bores in the pin 21 and the jaw 22.
Referring to Figures 3-7, the process for manufacture of the jaw pivot pin 21 is illustrated by showing the steps of manufacture.
Figure 3 shows the cylindrical pin 21 after the pin is rough finished to a predetermined oversize diameter and a pair of reduced diameter recesses 31, 32 are formed near its axially opposite ends. The recesses 31, 32 having an axial dimension matching the bearing surfaces of the arms 17,18 of the tenter clip 11.
Figure 4 shows the cylindrical pin 21 after sleeves 34, 36 of high temperature resistant plastic, such polytetraflouraethylene has been applied by injection molding to the reduced diameter areas 31, 32 of the pin 21. The oversized pin 21 is next machined by centerless grinding to a desired finished diameter as illustrated in Figures 6 and 7.
Figures 8 and 9 illustrate the centerless grinding step. The pin 21 is supported by a work blade 41 and is sandwiched between a grinding wheel 42 and a regulating wheel 43. As shown in Figure 9, the pin 21 is guided by work rest guides 46, 47, 48, 49 during a machining operation.
In summary, the invention is an improved pivot connection between a first component in the form of the illustrated clip body 14 and a second component in the form of pivot pin 21. The first and second components have radially confronting cylindrical bearing surfaces. One of the pivot components has a pair of reduced diameter recesses 31, 32 which are roughed up prior to application of a layer of cylindrical surface self lubricating plastic 34. The self lubricating plastic is restrained from rotation by the roughed up surface and is in bearing engagement with the bearing surface of the other component.
PRACTICAL APPLICATION OF THE INVENTION
This application has particular application in tenter clips which are connected in series by a chain to form a tenter chain. Tenter chains are used in opposing pairs to grip opposite edges of a continuous web of flat material, such as a woven cloth and simultaneously stretch the material in opposite directions while conveying it through a relatively high temperature process oven as a finishing operation in the manufacture of the processed material.
Wear on the bearing surfaces has long been a problem in tenter clip design because lubrication of the bearing surfaces is impractical, mainly because the bearing surfaces are above the web material and it is virtually impossible to lubricate the bearing surfaces without lubrication spilling onto the web material. Since these bearing surfaces are typically not lubricated, they are made of metal which resists high temperature and are expected to wear significantly. Frequent repair of the clip is required to keep the clips within operating tolerances. The repair of some clip designs require reboring the pivot pin hole and a new larger diameter pivot pin. The repair of clips using replaceable

steel bushing are repaired by replacing the bushing and it is often to replace the pin as
well.
Various plastic materials with unproved strength and wear characteristics and
the ability to withstand high temperature have been developed. They have been tried
and tested with limited success. Very close tolerances are necessary for proper
operation of a tenter clip. Steel bushings for tenter clips are commonly ground on their
outside diameter and honed on their inside diameter to achieve the required tolerances.
It is difficult and expensive to obtain these desired tolerances with plastic bushings.
Most plastic materials have a much higher coefficient of thermal expansion than metals
used in, tenter clip components. This tends to cause the bushings to lose clearance and
lock on the Pin preventing rotati nn TnfireasingAa^ald^l^rattGe^seJves4tH»ymhlembut
creates manufacturing and functional problems.
The normal method of installation of bushings is by interference press fit.
Plastic bushings tend to deform when press fit, thereby losing most of the interference
press fit holding ability. This allows rotation and or axial movement of the bushing,
which is unacceptable.
The tenter pin of this invention solves all the beforementioned problems in a cost
effective manner. Tolerances are not a problem because the plastic bearing material is
molded into a groove or recess in the pin and the pin and the plastic inserts are
centerless ground as a unit. By molding the plastic into a recess with a knurled bottom
surface the plastic insert is restrained from rotation and axial movement relative to the
pin. Thermal expansion of the plastic insert is minimized because the plastic insert is
radially thinner than that of a stand alone plastic bushing. By forming the thin plastic
bearing in recesses in the phi, the pin and inserts can be centerless ground as a unit to a
final diameter. This facilitates manufacture and pin installation,

We Claim:-

1. A pivot connection between a first component 14 having a radially inward facing
cylindrical surface and a second component 21 having a radially outward facing
cylindrical surface in confronting relation to said radially inward facing cylindrical
surface, characterized in that;
a recess 31 formed in one of said radially outward facing cylindrical surfaces, said recess presenting a roughed up surface and a thin cylindrical layer 34 of self lubricating plastic molded in said recess 31 in radially confronting and bearing engagement with the radially inward facing cylindrical surfaces, said roughed up surface preventing relative movement of said layer of self lubricating plastic 34.
2. The pivot connection as claimed in claim 1, wherein said plastic is polytetraflouraethylene.
3. The pivot connection as claimed in claim 1, wherein said plastic is polytetraflouraethylene having a melting point greater than 600 degree Fahrenheit.
4. The pivot connection as claimed in claim 2, wherein said recess is formed in said radially outward facing cylindrical surface of said second component.

Documents:

3789-DELNP-2005-Abstract(24-12-2007).pdf

3789-DELNP-2005-Abstract-(18-08-2008).pdf

3789-delnp-2005-abstract.pdf

3789-delnp-2005-assignments.pdf

3789-DELNP-2005-Claims(24-12-2007).pdf

3789-DELNP-2005-Claims-(01-09-2008).pdf

3789-DELNP-2005-Claims-(18-08-2008).pdf

3789-DELNP-2005-Claims-(29-08-2008).pdf

3789-delnp-2005-claims.pdf

3789-DELNP-2005-Correpondence-Others(24-12-2007).pdf

3789-DELNP-2005-Correspondence-Others-(01-09-2008).pdf

3789-DELNP-2005-Correspondence-Others-(18-08-2008).pdf

3789-DELNP-2005-Correspondence-Others-(29-08-2008).pdf

3789-delnp-2005-correspondence-others.pdf

3789-delnp-2005-description (complete)-01-09-2008.pdf

3789-delnp-2005-description (complete)-18-08-2008.pdf

3789-delnp-2005-description (complete)-29-08-2008.pdf

3789-delnp-2005-description (complete).pdf

3789-DELNP-2005-Drawings-(18-08-2008).pdf

3789-DELNP-2005-Drawings-(29-08-2008).pdf

3789-delnp-2005-drawings.pdf

3789-DELNP-2005-Form-1(24-12-2007).pdf

3789-DELNP-2005-Form-1-(18-08-2008).pdf

3789-delnp-2005-form-1.pdf

3789-delnp-2005-form-13-(29-08-2008).pdf

3789-delnp-2005-form-13.pdf

3789-delnp-2005-form-18.pdf

3789-DELNP-2005-Form-2(24-12-2007).pdf

3789-DELNP-2005-Form-2-(18-08-2008).pdf

3789-delnp-2005-form-2.pdf

3789-DELNP-2005-Form-3(24-12-2007).pdf

3789-DELNP-2005-Form-3-(18-08-2008).pdf

3789-delnp-2005-form-3.pdf

3789-DELNP-2005-Form-5(24-12-2007).pdf

3789-delnp-2005-form-5.pdf

3789-delnp-2005-pct-101.pdf

3789-delnp-2005-pct-210.pdf

3789-delnp-2005-pct-237.pdf

3789-delnp-2005-pct-304.pdf

3789-delnp-2005-pct-373.pdf

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Patent Number

223101

Indian Patent Application Number

3789/DELNP/2005

PG Journal Number

44/2008

Publication Date

31-Oct-2008

Grant Date

04-Sep-2008

Date of Filing

25-Aug-2005

Name of Patentee

TRI-MACK PLASTICS MANUFACTURING CORP.

Applicant Address

66, TUPELO STREET, BRISTOL, RHODE ISLAND 02809, U.S.A.

Inventors:

#	Inventor's Name	Inventor's Address
1	CHRISTOPHER EUGENE HOSMER	202 TICONDEROGA DRIVE, GREER, SOUTH CAROLINA 29650, USA.
2	EDWARD J. MACK, II	11 HOPE STREET, BRISTOL, RHODE ISLAND 02809, USA.
3	ANTHONY C. MEDEIROS	621 SWEET JULIET WAY, GREER, SOUTH CAROLINA 29650, USA.

PCT International Classification Number

B29C

PCT International Application Number

PCT/US2004/002066

PCT International Filing date

2004-01-27

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10/352,194	2003-01-27	U.S.A.