Title of Invention

A COMBINED CORE AND HEADER ASSEMBLY FOR A WELDED HEAT EXCHANGER WITH GROMMET CONSTRUCTION AND A METHOD OF MAKING SAID WELDED HEAT EXCHANGER

Abstract

A method of manufacturing a heat exchanger comprising a core assembly having a plurality of tubes connected by an array of fins, with ends of the tubes extending from the fin array on at least one side of the core assembly and resilient, polymeric grommets disposed around the tube ends. The heat exchanger includes a tank portion I for receiving fluid entering or leaving the core assembly and a header portion having ~ openings to receive the tube ends and grommets to create a sealed, fluid-tight tube-to header joint. There is provided a reinforcing member across the opening of the tube ends extending from the tube end opening to the portion of the tube end around which the grommet is disposed without substantially extending into the fin array portion of the core assembly. The header portion comprises a substantially planar base having openings therein with &ide and end walls extending out of the plane of the base and connected by one or more fluid-tight welds to the tank portion. The side and end walls extend a distance sufficient to dissipate heat generated in making the welds and keep the heat generated from adversely affecting sealing ability of the grommets when the welds are made between the tank and header portion with the tube ends and grommets received in the header portion openings.

Full Text

Technical Field This invention relates to a combined core and header assembly for a welded heat exchanger with grommet construction and a method of making said welded heat exchanger and, more particularly, to motor vehicle heat exchangers utilizing grommets in the tube-to-header joints and tanks welded to the header. Backwound Art Heat exchangers, particularly those utilized in motor vehicles; may be liquid-to-air heat exchangers, (e.g., radiators for engine coolant, air conditioning condensers and evaporators, and oil coolers) or may be air-to-air heat exchangers (e.g. charge air coolers). Liquid-to-air and air-to-air heat exchangers are typically composed of an inlet tank or manifold, an outlet tank or manifold, and a large number of tubes extending between the tanks or manifolds which carry the fluid to be cooled. Headers are normally provided on the tubes for mechanical attachment and fluid connection to the tanks. Fins attached to the tubes transfer heat between the liquid or gas inside the tubes and the ambient atmosphere outside. A mechanical framework or structure is usually included to provide structural strength to the assembly and to provide means for mounting the unit to the vehicle or other machinery on which it is used. The tubes utilized may be either round or oval, or may be oval with circular ends. Prior art methods of welding tube-to-header joints are disclosed, for example, in U.S. Pat. No. 5,407,004, the disclosure of which is hereby incorporated by reference. In use, heat from the hot liquid or air within generally causes the tubes to expand and grow in length due to thermal expansion. Since the tanks or manifolds are fixed with respect to each other by the unit framework or structure, the growth in length of tubes places high mechanical stresses on the tanks and the associated headers, particularly in the area of the joints between the tubes and headers. In addition, the pressure of the hot liquid or hot air within the heat exchanger tends to distort the tanks or manifolds and headers, creating further stresses on the tube-to-header joints. The combination of stress resulting from thermal expansion and internal pressure can result in early failure of heat exchangers. Cracks in the joints between the tubes and the headers or in the tubes immediately adjacent to these joints are the most common mode of failure. Many approaches have been taken to avoid heat exchanger failures due to thermal expansion and internal pressure. Most approaches fall into one of two categories: 1) those which improve the strength of the areas prone to failure and 2) those which provide resilience in the areas prone to failure. Approaches which provide resilience have appealed to designers because they provide a solution to the stresses of thermal expansion and internal pressure with a greater economy than any approach which must provide more material to achieve an improvement in strength. Engine cooling radiators for vehicles have sometimes been designed with resilient tube-to-header joints. Locomotive radiators have been manufactured by the assignee of the present invention for over thirty (30) years using headers of special resilient design. In this design, metallic headers have oversized holes or openings in them to receive oval brass tubes extending from the radiator core. Within the openings in the header there are placed oval brass ferrules. These ferrules are bonded to the header by molded silicone rubber. The ferrules are then soldered to the core tubes extending therethrough to form a leak-free, resilient joint between the tubes and the headers. Fins of the flat plate-type design have collars fitted around the tubes. The headers are mechanically attached to tanks, such as by bolting. While this has been an extremely effective design under typical operating conditions for locomotives, it is expensive to produce. In the 1970"s, radiators for automobiles were produced which utilized round aluminum tubes, aluminum plate fins, aluminum headers and plastic tanks. A sheet of molded rubber provided resilient grommets at each tube hole in the header, and also provided a gasket for sealing the headers to the plastic tanks, which were attached to the headers by means of crimped tabs on the headers. The insertion of the tubes into the rubber grommets in the header holes compressed the rubber of the grommets providing a resilient sealing attachment of the tubes to the headers. However, considerable force was required to insert all the core tubes into the header holes simultaneously. This design was limited to relatively small units because of the problems of core and header distortion during assembly and ^ because of the close tolerances which were required to accomplish the mating of the core tubes to the header with the desired amount of grommet compression. Other radiators have also utilized rubber grommets in their tube-to-header joints. These radiators have been designed around individual finned tubes having round ends and oval cross-sections which are finned along most of their length. As in the previous design, sealing of the tubes to the header was accomplished by compression of the grommets between the tubes and the header. However, in this alternative design, the tubes were assembled to the headers individually thereby avoiding high assembly forces. This allowed the construction of very large radiators for heavy construction equipment. However, it has been found that the use of tubes with round ends limits this design to cores having rather wide tube spacing, which results in relatively poor thermal performance compared to most radiator core designs. U.S. Patent Nos. 4,756,361 and 5,205,354 describe a radiator which utilizes circular tubes and tube ends which extend through silicone rubber grommets f which are disposed in openings within a header plate. U.S. Patent Nos. 5,052,475 and 5,226,235 disclose use of circular grommets to seal circular tubes into soldered tanks and welded tanks, respectively. British Patent No. 29,777 discloses the use of round tubes and grommets with a tube plate cast integrally with the header. Currently, air-to-air heat exchangers using brazed aluminum cores having oval tubes are being produced commercially. Aluminum headers having oversized oval openings are welded to cast aluminum manifolds. Oval silicone rubber grommets, otherwise similar to those described in the aforementioned "361 patent, are inserted into the openings in the headers of the welded tanks. In the aforementioned "361 patent, the headers are intended to be f connected to inlet and outlet tanks by means of bolting with a sealing gasket, or other similar means. U.S. Patent 5,226,235 describes a radiator made up of a unitary core consisting of tubes and fins, connected to tank assemblies which consist of welded tank and header assemblies into which resilient grommets have been inserted after welding. This "235 patent provides advantages over the "361 patent in that the welded tank and header assembly is more compact than one assembled by bolting with a sealing gasket. In addition, a welded tank design is quite flexible and can be quickly made up to suit any application. However, a difficulty with the "235 patent is that it requires that all welding of the tank/header assembly is to be completed before assembly of the resilient grommets to that assembly. This is stated to be necessary to prevent heat damage to the resilient grommets. However, it makes assembly of the unitary core assembly to the tank/header assemblies particularly difficult, since one can only see one side of the grommets and access to the other side of the grommets to aid in assembly is denied. For instance, it would aid insertion of the core tubes into the grommets if the tube ends were fitted with removable bullet noses. However, in the one-piece tank/header design, retrieval of the bullets after insertion is practically impossible. Additionally, access to the side of the grommets remote from the tube insertion side can be helpful to tube insertion in other ways. For example, supporting or backing-up the remote side of the grommet during tube insertion makes tube insertion easier and prevents pushing out of the grommets. This is, of course, impossible with the one piece tankweader assembly described in the "235 patent. It would be advantageous to have the critical tube-to-header joints made and inspected with full access to both the airside and fluid side of the joints. The core assembly can be separately tested and corrections can be made to the tube-to-header joints, if necessary, before the tanks are attached. Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved heat exchanger and method of making such heat exchanger which utilizes grommets in tube-to-header joints, which header may be welded to the tank after insertion of the grommets. It is a further object of the present invention to provide an improved method of assembly of a heat exchanger in which the core assembly can be separately tested and corrections can be made to the tube-to-header joints, if necessary, before the tanks are attached. Disclosure of Invention The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a heat exchanger comprising a core assembly having a plurality of tubes connected by an array of fins, with ends of the tubes extending from the fin array on at least one side of the core assembly, and resilient, polymeric grommets disposed around the tube ends. Preferably, the grommets of the heat exchanger are made of a heat-resistant silicone rubber. The heat exchanger includes a tank portion for receiving fluid entering or leaving the core assembly and a header portion having openings receiving the tube ends and grommets to create a sealed, fluid-tight tube-to-header joint. The header portion comprises a base having openings therein and side walls extending out of a plane of the base and connected by one or more fluid-tight welds to the tank portion. The side walls extend a distance sufficient to dissipate heat generated in making the welds and keep the heat generated from adversely affecting the sealing ability of the grommets when the welds are made between the tank and the header portion with the tube ends and grommets received in the header portion openings. The header portion of the heat exchanger may be comprised of a unitary sheet of metal having folded or drawn side walls extending from the base. The side and end walls of the header portion may be joined at corners thereof to create an open box structure. Preferably, the header base is substantially planar while the side and end walls are substantially perpendicular to the plane of the base. In the preferred embodiment, the structure also includes a reinforcing member across the opening of the tube ends extending from the tube end opening to the portion of the tube end around which the grommet is disposed without substantially extending into the fin array portion of the core assembly. In another aspect, the present invention relates to a heat exchanger comprising a core assembly having a plurality of tubes connected by an array of fins, with ends of the tubes extending from the fin array on at least one side of the core assembly and resilient, polymeric grommets are disposed around the tube ends. The heat exchanger includes a tank portion for receiving fluid entering or leaving the core assembly and a header portion having openings to receive the tube ends and grommets to create a sealed, fluid-tight tube-to-header joint. The header portion comprises a substantially planar base having openings therein with side and end walls extending out of the plane of the base and connected by one or more fluid-tight welds to the tank portion. The side and end walls extend a distance sufficient to dissipate heat generated in making the welds and keep the heat generated from adversely affecting sealing ability of the grommets when the welds are made between the tank and header portion with the tube ends and grommets received in the header portion openings. In yet another aspect, the present invention provides a method of making a heat exchanger. The method comprises initially providing a core assembly having a plurality of tubes connected by an array of fins with the ends of the tubes extending from the fin array on at least one side of the core assembly and resilient, polymeric grommets disposed around the tube ends. The grommets provided may be comprised of a heat-resistant silicone rubber. Also provided are a tank, having an open end portion for receiving fluid entering or leaving the core assembly, and a header portion with a base having openings for receiving the tube ends and side walls extending out of a plane of the base. In the preferred embodiment, the side walls are extended a distance sufficient to dissipate heat generated in welding the tank to the header portion and keep the heat from adversely affecting the sealing ability of the grommets when the welding is performed with the tube ends and grommets received in the header portion openings. The method also includes attaching the header portion to the core assembly by receiving the tube ends and grommets in the header portion openings to create a sealed, fluid-tight tube-to-header joint. The header portion is then welded to the tank open end portion to create one or more fluid-tight welds. In the preferred embodiment, the welding takes place with the tube ends and grommets received in the header portion openings without adversely affecting the sealing ability of the grommets in the tube-to-header joint. The method may further include the step of either folding edge portions or drawing portions of the unitary sheet of metal comprising the header portion to create the side walls extending from the base, and may also include joining the side walls and end walls at corners thereof to create an open box structure. The side and end walls may be folded to positions substantially perpendicular to the plane of the substantially planar base. In the preferred embodiment, the tube ends include a reinforcing member inserted across the opening of the tube extending from the tube end opening to the portion of the tube end around which the grommet is disposed without substantially extending into the fin array portion of the core assembly. A further aspect of the invention relates to a heat exchanger comprising a core assembly having a plurality of tubes connected by an array of fins, with ends of the tubes extending from the fin array on at least one side of said core assembly and resilient, polymeric grommets disposed around the tube ends. A reinforcing member is disposed across the opening of at least a portion of the tube ends and extends from the tube end opening to the portion of the tube end around which the grommet is disposed without substantially extending into the fin array portion of the core assembly. The heat exchanger includes a tank for receiving fluid entering or leaving the core assembly and a header portion having openings receiving the tube ends and grommets to create a sealed, fluid-tight tube-to-header joint. The header portion of this embodiment comprises a base having openings therein and side walls extending out of a plane of the base and connected by one or more fluid-tight welds to the tank. The side walls extend a distance sufficient to dissipate heat generated in making the welds, and keep the heat from adversely affecting sealing ability of the grommets when the welds are made between the tank and header portion with the tube ends and grommets received in the header portion openings. Accordingly the present invention provides a combined core and header assembly for a welded heat exchanger with grommet construction comprising: a core assembly having a plurality of tubes connected by a fin array, said tubes having ends and openings in the ends, the tube ends extending from the fin array on at least one side of said core assembly; resilient, polymeric grommets disposed around the tube ends; and a header portion having openings receiving said tube ends and said grommets to create a sealed, fluid-tight tube-to-header joint, said header portion comprising a base having said opening therein and side walls on all sides of the base extending out of a plane of said base and connectable by one or more fluid-tight welds to a tank portion, said header portion being free of a tank such that the tube-to-header joint is accessible on both sides of said joint for inspection and testing before attachment to a tank portion, all of said side walls having free edges extending a distance out of the plane of said base sufficient to dissipate heat generated in welding said free edges to a tank portion from adversely affecting the sealing ability of said grommets when said welds are made between said tank portion and said header portion while said tube ends and grommets are received in the header portion openings. Accordingly the present invention provides a method of making a welded heat exchanger with grommet construction comprising: providing a tank having an open end portion for receiving fluid entering or leaving a core assembly, the tank being free of a header; providing a combined core assembly and header, i) the core assembly having a plurality of tubes connected by an array of fins, with ends of said tubes extending from the fin array on at least one side of said core assembly, and ii) the header having openings with resilient, polymeric grommets disposed therein for receiving said tube ends, the header comprising a base having said openings therein and side walls extending out of a plane of said base, said side walls extending a distance sufficient to dissipate heat generated in welding said tank to said header and prevent the welding heat from adversely affecting sealing ability of said grommets when said welding is performed while said tube ends and grommets are received in the header portion openings; said header being attached to said core assembly by tube ends received in said resilient, polymeric grommets which are in rum received in the header openings to creaie a scaled, fluid-tight tube-to-header joint; and thereafter welding said header to said lank open end portion to create one or more fluid-tight welds, the welding occurring while said tube ends and grommets are received in the header openings, without adversely affecting sealing ability of said grommets in said tube-to-header joint. The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which: Fig. 1 is a perspective view of the preferred unitary brazed core block employed in the present invention. Fig. 2 is a perspective view of the preferred box header employed in the present invention. Fig. 3 is a perspective view of the preferred stamped blank of the box header of Fig. 2. Fig. 4 is a perspective view of the preferred molded grommets employed in the present invention. Fig. 5 is side elevational view of one step in assembling the tubes of the core assembly into the openings of the header plate to make the heat exchanger of the present invention. Fig. 6 is side elevational view of an assembly step subsequent to that of Fig.5. Fig. 7 is side elevational view of an assembly step subsequent to that of Fig. 6. Fig. 8 is a perspective view of the box header of Fig. 2 assembled onto the unitary brazed core block of Fig. 1. Fig. 9 is a top plan view of the tubes fitted into the box header of Fig. 8. Fig. 10 is an end elevational view of a tube fitted into the box header along line 10-10 of Fig. 9. Fig. 11 is a side elevational view of a tube fitted into the box header along line 11-11 of Fig. 9. Fig. 12 is an exploded view of a preferred tank to be welded onto the box header of Fig. 2. Fig. 13 is a perspective view of the tanks assembled onto the box headers and unitary brazed core block assembly of Fig. 8. Mode(s) for Carrying Out the Invention In describing the preferred embodiment of the present invention, reference will be made herein to Figs. 1-13 of the drawings in which like numerals refer to like features of the invention. Features of the invention are not necessarily shown to scale in the drawings. This invention is directed primarily to air cooled radiators which utilize a liquid coolant for automotive applications. However, it may also be utilized for any other type of heat exchanger, for example, those discussed in the background of the invention such as oil coolers, charge air coolers and the like. The present invention provides a structural assembly and method which permits the header to be welded to the tank after insertion of the grommets into the header openings, without heat damage to the grommet material. Preferably oval tubes are utilized in the heat exchanger for close tube spacing for optimum heat transfer performance of f the core, although other tube shapes and cross-sections may be utilized. As shown in Fig. 1, the heat exchanger of the present invention preferably utilizes a core block or assembly 20 which comprises an array of parallel tubes 22, preferably oval tubes, between which are interposed an array of heat transfer fins 24. These fins may be of the flat type or serpentine type as shown in the core i depicted in Fig. 1. Any of these fin styles may include louvers to enhance heat transfer. The tubes and fins are typically formed of aluminum, brass, copper or other thermally conductive metal or alloy. Serpentine fins 24 may extend in a serpentine pattern wherein the strips are configured with a plurality of alternating bends between adjacent tubes 22. The root of the bend is generally secured by brazing or soldering to the tube. Alternatively, the fins may be made of sheet metal which has a collar formed about a hole. The tubes may be inserted through the collar opening and a plurality of fins may be stacked in order to make up the fin array within the core. The ends 23 of tubes 22 extend beyond the fin array of core 20 to connect to the headers and tanks utilized in the heat exchanger. The preferred header employed in the present invention is depicted in Fig. 2. Header 30 comprises a generally rectangular body having a substantially ffat or planar base portion 38 of length L and width W within which are formed header openings 36 which conform generally to the configuration of tube ends 23. The header portion openings 36 are preferably oval and arranged in a single row as shown, although multiple rows of tubes may be employed. As used herein, the term "oval" refers to any non-circular shaped axial cross-section (i.e. perpendicular to the axis of the tube) having a generally smoothly curving periphery such as an ellipse or a rectangle with rounded corners, or other obround or egg shape. Being of oval cross-sectional shape, such tubes and openings will have a diameter in one direction greater than the diameter in another (usually perpendicular) direction, which are referred to herein as the "major diameter" and "minor diameter" respectively. While oval shaped tubes and, consequently, oval shaped header openings and grommets are preferred, other tube opening and grommet configurations can be used, such as circular or rectangular. For reasons discussed further below, in order to accommodate the grommets, the header openings 36 are larger than the tube ends 23. The width W of header plate portion 38 is only slightly greater than the major diameter of header openings 36 to minimize header flexing and achieve maximum header portion strength. Forming a box-type configuration to the header 30 are upstanding vertical side walls 32 and end walls 34 which extend upward from the plane of base 38. Side walls 32 face each other along opposite edges along the long sides of plate portion 38, corresponding to length L, while vertical upstanding end walls 34 face each other along the shorter ends of plate portion 38, corresponding to width W. Side walls 32 have free edges 32b at the upper portions thereof while end walls 34 have free edges 34b along the upper portions thereof. Edges 32b and 34b of header 30 are connected by welding to the tank portions of the heat exchanger as will be discussed further below. In order to permit proper heat dissipation and to prevent excessive heat buildup in the vicinity of header openings 36, it is preferred that the height H of side walls 32 and end walls 34b are carefully controlled. For an example of a header utilized in motor vehicles, it is preferred that the height of the side and end walls be at least about one-half VA) inch (1.25mm), more preferably at least about one (1) inch (2.5mm). The header side and end wall height is also preferred to be less than about two (2) inches (5.0mm), more preferably less than about one and one-half (Vh) inches (3.75mm). The header side and end wall height should be high enough to avoid excessive temperatures to develop in the grommets as a result of welding at edges 32b, 34b to the tank, but not so high as to require excessive material. The header may be formed by any conventional manufacturing process, such as casting, stamping or drawing. The preferred stamped blank of header 30 is depicted in Fig. 3. The header plate portion 38, side walls 32 and end walls 34 are preferably formed from a solid unitary sheet of metal, for example copper, brass or aluminum. Vertical side walls 32 are formed by bending or folding along the line indicated by 33 while vertical end walls 34 are formed by bending or folding along the lines indicated by 35. Side wall 32 end portions 32a then contact end wall 34 side portions 34a along a vertical seam which may be joined and sealed by welding to form corners. Such welding is preferably performed prior to insertion of the grommets since the corners formed by end portions 32a, 34a are relatively close to the header openings 36. For drawn headers, the side walls 32 and end walls 34 (Fig. 2) are drawn from a unitary sheet of metal and extend upwards from the base or plate portion 38. Grommets are the preferred sealing means between the tubes and the header portion openings. The preferred grommet of the preferred invention is depicted in Fig. 4. Grommet 40 is preferably made of a heat-resistant silicone // rubber or other resilient, flexible or compliant polymer or other material which provides good sealing against the other components of the heat exchanger, and which has suitable heat resistance to avoid affecting the grommet"s sealing ability when the header is welded to the tank while the grommets are in the header openings. The preferred grommet is made from silicone rubber, such as compound ST 125785-V-RED, which may be obtained from Dow Corning Corporation. The silicone rubber is a high-temperature silicone rubber which includes a vulcanizing agent and meets ASTM D2000. The other pertinent properties of the preferred grommet material were as shown in Table 1 below. In laboratory tests with headers of the invention, it was determined that the grommets were able to withstand temperatures up to 500°F-600°F (260°C-315°Q. Grommets 40 comprise a body portion having an opening therein to receive the tube from a heat exchanger core. A radially outward extending lip or flange is disposed at a first upper end of the body portion and a radially inwardly extending lip or flange is disposed at a second, lower end of the grommet. It should be understood that relative directional terms are used herein for reference only in connection with the drawings and the grommet and other components may be utilized in any position, including those other than that shown. Grommet 40 has a configuration which conforms to the shape of the oval openings 36 in header portion 38 which are sized to receive tube ends 23 from the header core (Fig. 1). The assembly of the tube ends of the header core 20 into the header openings 36 utilizing the grommets is depicted in Figures 5, 6 and 7. In Fig. 5, aoth the tube 22 and grommet 40 are initially aligned along the direction of the length of the tube. As shown in Fig. 6, the grommet 40 is inserted into opening 36 3f the header, and the tube end 23 is brought into contact with the grommet. Then, as shown in Fig. 7, tube end 23 is forced through the resilient inner opening Df grommet 40 so that the tube 22 is fully received by the grommet within header opening 36. Referring back to Fig. 4, the grommets are preferably molded in groups of more than one, for example a group of three (3), so that they may be nserted three at a time into the header openings. Once all the grommets are nserted into the header openings, all of the tube ends 23 from the core assembly 20 are inserted at the same time through the grommet openings. Preferably the inner diameter of the inward lip of the grommet is less than he outer diameter of the tube end, so that after full insertion of the tube, the outer wall, the lower end of grommet 40 is forced radially outward. Because of the esilience of the grommet material the tube stretches the grommet in the lower egion and flexes its walls to provide good sealing contact between the inward lip and the outside surface of the tube end 23 to form a tight seal around the tube. \dditionally, the expansion of the inward lip bulges or forces outward grommet auter wall portion which locks against and forms a seal with the edge of the header Dortion opening to prevent the grommet from slipping back out of the header portion opening. Sealing of the grommet to the tube and the header portion is urther enhanced by the action of internal pressure inside the tank/header assembly 30 which serves to force the lip radially inward into tighter contact with both the ube and header portion in the manner of an o-fing seal. The inside surface of the jpper end of the grommet may also be forced inward to contact the tube outer iurface to seal against leakage. Additionally, the lower outside edge of outward lip 13. The method as claimed in claim 12, wherein the header base is substantially planar and said side and end walls are folded to positions substantially perpendicular to the plane of said base. 14. The method as claimed in claim 10, wherein said header comprises a unitary sheet of metal having drawn portions of said sheet creating said side-walls extending from said base. 15. The method as claimed in claim 14, wherein the header base is substantially planar and said side walls are substantially perpendicular to the plane of said base. 16. The method as claimed in any of claims 10 to 15, wherein said grommets comprise a heat-resistant silicone rubber. 17. The method as claimed in any one of claims 10 to 16, comprising, in at least a portion of said tube ends, a reinforcing member across openings of said end, said reinforcing member extending from said tube end opening to the portion of said tube end around which the grommet is disposed without substantially extending into said fin array portion of said core assembly. 18. The method as claimed in any one of claims 10 to 17, comprising providing a pair of said tanks and said headers, and providing a core assembly having tube ends extending from the fin array on two sides of said core assembly with the headers being attached on both sides of said core assembly by tube ends received in the resilient, polymeric grommets which are in turn received in the header openings to create a pair of sealed, fluid-tight tube-to-header joints, and comprising thereafter welding said headers to the tank open end portions to create fluid-tight welds, the welding occurring while said tube ends and grommets are received in the header openings, without adversely affecting sealing ability of said grommets in the tube-to-header joints. 19. A combined core and header assembly for a welded heat exchanger with grommet construction, substantially as hereinabove described and illustrated with reference to the accompanying drawings. 20. A method of making a welded heal exchanger with grommet construction, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

in-pct-2001-1207-che abstract-duplicate.pdf

in-pct-2001-1207-che abstract.pdf

in-pct-2001-1207-che claims-duplicate.pdf

in-pct-2001-1207-che claims.pdf

in-pct-2001-1207-che correspondence-others.pdf

in-pct-2001-1207-che correspondence-po.pdf

in-pct-2001-1207-che description(complete)-duplicate.pdf

in-pct-2001-1207-che description(complete).pdf

in-pct-2001-1207-che drawigns.pdf

in-pct-2001-1207-che drawings-duplicate.pdf

in-pct-2001-1207-che form-1.pdf

in-pct-2001-1207-che form-13.pdf

in-pct-2001-1207-che form-19.pdf

in-pct-2001-1207-che form-26.pdf

in-pct-2001-1207-che form-3.pdf

in-pct-2001-1207-che form-5.pdf

in-pct-2001-1207-che form-6.pdf

in-pct-2001-1207-che others.pdf

in-pct-2001-1207-che pct.pdf

in-pct-2001-1207-che petition.pdf