Heat exchanger

Abstract

The present invention relates to a tank assembly for a heat exchanger, which comprises: a tank body (14.1) defining a cavity (15) for a fluid, an axial tank opening of the cavity (15.1) being delimited by a peripheral foot portion (12); a header plate (16) closing the tank opening (15.1) and attached by clinching to the tank, wherein the header plate (16) comprises oblong through-holes (16.1) extending transversally, said through-holes (16.1) being adapted for receiving respective end portions of heat exchanger tubes; wherein the header plate (16) comprises longitudinal edges (20) and transverse edges (30), a plurality of clinching members (22, 32) being connected to said edges and clinched onto said tank body (14.1). Remarkably, the clinching members comprise: a plurality of first clinching members (22) distributed along the longitudinal edges (20) and clinched over the foot portion (12); and a plurality of second clinching members (32) distributed along the transverse edges (30) clinched over respective transverse clinching surfaces (52) provided on the tank body (14.1) and located rearwardly from the foot portion (12).

Description

[0001] HEAT EXCHANGER

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to the field of heat exchangers and more specifically to header plates of heat exchangers.

[0004] BACKGROUND OF THE INVENTION

[0005] A heat exchanger such as a radiator, condenser or evaporator, for use in an automotive vehicle, includes usually an inlet tank, an outlet tank and a plurality of flat tubes extending between the tanks. The tubes connect fluidly the two tanks and enable a fluid flow between them. The connection of the tubes to a tank is established by means of a respective header plate comprising oblong apertures in which the tubes are fitted, and which closes the tank cavity. Commonly, a circumferential gasket is arranged between the header plate and tank opening, which is also referred to as peripheral portion or "tank foot". In this arrangement, the seal, which provide a fluid-tight mounting, is compressed between the tank and the header plate. According to prior art, the header plates and tubes are typically assembled into a unitary structure and brazed.

[0006] According to the prior art, in order to fix the header plate to the tank, a plurality of deformable metallic tabs, respectively crimping tabs or clinch tabs, are usually provided at an edge of the header plate. When the header plate is placed on the tank, the tabs are deformed (e.g. by crimping or clinching) in such a way that they grab around a portion of the frame of the tank.

[0007] Commonly known clinching arrangements for heat exchanger have several drawbacks. Due to clinching which may be difficult to apply uniformly around the periphery, the gasket arranged between the header plate and the peripheral border is often submitted to rather high or irregularly distributed compression forces and / or stresses along the gasket body. As a consequence, the gasket is more susceptible to wear and often has a relatively short life cycle.

[0008] Moreover, the clinching process involves transverse forces orthogonal to the axial compression direction from the tank to the header plate. Consequently, these transverse forces applied on the header plate may generate small transverse displacements of the header plate relative to the tank degrading the quality and the sealing performance of the assembly.

[0009] Furthermore, these transverse forces may also generate deformation of the tank, especially for large (i.e. wider than 50 mm) single row heat exchangers, such as bending of the short sides of the tank resulting in a deformation of the tubes, this even when the tank includes a stiffener. As a consequence, the tubes are susceptible to leak which in turn often lead to component failure.

[0010] LU500870 discloses a heat exchanger with a tank and header plate assembly, wherein the header plates comprise a plurality of clinching members with apertures that cooperate with rigid tabs protruding laterally from the tank foot.

[0011] OBJECT OF THE INVENTION

[0012] The object of the present invention is to provide an improved tank and header plate assembly, which avoids the above-mentioned drawbacks.

[0013] This object is achieved by a tank assembly as claimed in claim 1 .

[0014] SUMMARY OF THE INVENTION

[0015] The present invention relates to a tank assembly for a heat exchanger, which comprises: a tank having a tank body defining a cavity for a fluid, an axial tank opening of the cavity being delimited by a peripheral foot portion having longitudinal and transverse sections; a header plate closing the tank opening and attached by clinching to the tank, the header plate having a rear side facing the cavity and an opposite front side wherein the header plate comprises oblong through-holes extending transversally, the through-holes being adapted for receiving respective end portions heat exchanger tubes; wherein the header plate comprises longitudinal and transverse edges, a plurality of clinching members being connected to the edges and clinched onto the tank body. Remarkably, the clinching members comprise: a plurality of first clinching members distributed along the longitudinal edges and clinched over the foot portion; a plurality of second clinching members distributed along the transverse edges, the second clinching members being clinched over respective transverse clinching surfaces provided on the tank body and located rearwardly from the foot portion.

[0016] The present invention provides a design where second clinching tabs do not lock onto the tank foot, but onto a surface (or surfaces) that is / are arranged rearwardly of the tank foot, i.e. axially further away from the rear side of the header plate.

[0017] Such surfaces are typically provided by additional reinforcement structures of ribs, thereby enhancing the stiffness of the transverse tank foot region. Furthermore, the second clinching members may typically have a longer axial extent than the first clinching members. As a whole, the inventive design allows reducing mechanical stress on the tank foot during the clinching process, hence reducing risks of deformation of the tank foot and also protecting the tubes proximal to the transverse edges.

[0018] In other words, it will be appreciated that the present design results in less forces being applied to the clinching members during the clinching operation to clinch the tank.

[0019] In embodiments, the header plate comprises respective transverse sidewalls extending along the transverse edges, and the second clinching members extend from an edge of the transverse sidewalls.

[0020] In embodiments, the second clinching members extend from the edge of the transverse sidewalls through a first portion extending over the foot portion up to the respective transverse surface, to a second portion, which is bent over the respective transverse surface. In particular, before assembly of the header plate to the tank, the first portion of the second clinching members comprises a straight base section and an outwardly bent intermediate section connecting the second portion, which is inwardly bent relative to the intermediate section. According to some preferred embodiments, the intermediate sections are outwardly bent with an angle between 15 and 35°, preferably of about 25°before assembly of the tank assembly (i.e. assembly of the tank and header plate), however other embodiments are also possible and still within the scope of the present invention. Accordingly, the intermediate sections may be outwardly bent with an angle between 105 and 125°, preferably of about 115° relative to the header plate plane.

[0021] According to the same or other embodiments, after assembly the intermediate sections are axially aligned. Additionally or alternatively, the second portions are configured to form an angle between 90 and 100° relative to the intermediate sections, preferably about 90°. This is the angle before and after assembly.

[0022] As will be understood, the various angles can be varied. The inclination of the longitudinal sidewalls and of the intermediate portions of the second clinching members are designed to allow passage of the tank foot during assembly.

[0023] In embodiments, the tank comprises a transverse rib parallel to each transverse section of the foot portion, the transverse ribs defining the transverse clinching surfaces. In other words, the tank has an additional transverse rib in the vicinity of the tank foot, which confers more rigidity, while providing a clinching surface for the second clinching members.

[0024] In embodiments, the second clinching members have a greater length than the first clinching members, which a convenient embodiment for engagement with the rearwardly located transverse clinching surfaces. For example, the length of the second clinching members is at least 1 .5 or 2.5 times that of the first clinching members.

[0025] The shape of the second clinching members facilitates insertion of the tank foot and reduces the forces required for their clinching. In particular, the second clinching members are easier to bend due to their increased length, hence resulting in less forces applied to the tank foot and less risks of deformation thereof.

[0026] Advantageously, the first and / or second clinching members may be formed as rectangular tabs. In embodiments, the header plate comprises respective longitudinal sidewalls extending along the longitudinal edges, and the first clinching members extend from an edge of the longitudinal sidewalls.

[0027] Before assembly of the header plate to the tank, the longitudinal sidewalls may preferably be outwardly bent and the first clinching members may preferably be inwardly bent, and clinching may preferably be obtained by inwardly folding the longitudinal sidewalls to bring the first clinching members over the tank foot portion.

[0028] In embodiments, a circumferential sealing element is arranged between the foot portion and header plate, which advantageously provides a fluid-tight mounting of the tank body to the header plate.

[0029] The present inventive tank assembly can be used for any configurations of a heat exchanger, be it for l-flow configuration (inlet and outlet tanks at opposite ends of the tubes) or ll-flow configuration (inlet and outlet tanks on the same side).

[0030] According to another aspect, the present invention also relates to a heat exchanger comprising a tank assembly according to the first aspect and a plurality of heat exchanger tubes having a respective first end engaged in the oblong through holes of the header plate, a respective second end of the heat exchanger tubes being fluidly connected to a second tank assembly.

[0031] The present heat exchanger may generally be used as charge air cooler in automotive vehicles, however other applications are possible.

[0032] According to another aspect, the invention relates to a method of assembling a header plate and tank to form the assembly according to the present disclosure. The method is recited in appended claim 16. Embodiments of the method are recited in claims 17 to 23.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig.1 shows (A) an exploded view of an embodiment of heat exchanger comprising the present tank assembly and (B) a perspective view of the same;

[0035] Fig. 2 illustrates several views of the header plate in a configuration ‘ready for assembly’, where A) is a perspective view; B) is a side view along the longitudinal side and C) is a side view of a transverse side.

[0036] Fig. 3 is a detail perspective view of Fig.1 showing the tank assembly;

[0037] Fig. 4 are detail views of the header plate and tank, illustrating the tabs (A) before and (B) after clinching.

[0038] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] An embodiment of heat exchanger including the inventive tank assembly is disclosed in the following. For ease of explanations, the drawings include an orthogonal coordinate system (X, Y, Z). In automotive applications, axis Y often corresponds to a direction along a width of a vehicle.

[0040] In reference to Fig.lA and Fig.l B, an embodiment of the present fluid-air heat exchanger 10 is shown in exploded and assembled configurations. The heat exchanger 10 conventionally has a plurality of tubes 11 for conveying the fluid between two tanks 14 that are fluidly connected at both ends with respective tanks. Each tank 14 has a tank body 14.1 which extends along direction Z and has an inner cavity 15. The tank body further has an opening 15.1 along axis Y, allowing access to the inner cavity 15. The cavity 15 is configured to distribute / collect the fluid when the heat exchanger is in operation. The tank comprises longitudinal and transverse walls that define the cavity, the opening 15.1 being delimited by a peripheral border of the tank body, referred to as tank foot 12. The tank foot 12 forms a peripheral edge outwardly protruding in ZX plane, surrounding the opening 15.1. The tank body 14.1 is typically manufactured by plastic injection molding and comprises on its outer side series of parallel reinforcing ribs 40. A straight bar, referred to as stiffener (not shown), extends centrally in the cavity opening, bridging the transverse walls.

[0041] A header plate 16 is used to close the tank opening, the header plate having a plurality of through-holes 16.1 for receiving end portions of the tubes 11. The plurality of tubes 11 extends between the opposite tanks 14. The tubes 11 are substantially straight and comprise at least one inner channel, wherein a fluid is flowing. In addition, the tubes may also be provided with fins (not shown) on the outer surface of said tubes. The fins improve the thermal transfer. Generally, the tubes may be flat and may have a substantially rounded-off rectangular cross section. It should however be noted that tubes may also present cross-sections of different forms. The tubes may be arranged in a parallel and aligned manner in order to form a single row. However, other configurations are likewise possible. The flat tubes extend along direction Y.

[0042] Fig.1 B shows the assembled configuration of the heat exchanger 10. The tubes 11 and header plates 16 are typically made from metal, i.e. aluminum alloy, and can thus be fixedly and sealably assembled by brazing, before assembly of the tanks. Since the tanks are made of plastic, a seal member, e.g. a rectangular gasket 42, is conventionally arranged between the header plate 16 and tank opening 15.1 .

[0043] Fig.2 shows different views of the header plate 16, which closes the tank opening 15.1 and hence forms an interface wall connecting the tubes. The header plate 16 is a plate-like element of substantially rectangular shape, which is attached to the tank 14 by clinching. The header plate may generally be made from sheet metal (e.g. aluminum alloy) by using a deformation process, such as stamping, punching or other metal-working processes.

[0044] The header plate 16 comprises a rear side 16.2 which faces the cavity 15 and the tank foot as well as a front side 16.3 opposite of the rear side. The series of through holes 16.1 for the tubes have an oblong cross-section and extend transversally (along X), i.e. generally perpendicularly to the tank length (along Z). It is understood that the through holes as well as the flat tubes may also have a different form in other embodiments. Any appropriate flat tube design may be used; however, the through-holes 16.1 are configured for receiving the end portions of the tubes 11. The trough-holes 16.1 are typically surrounded by a collar in contact with the tube ends (not shown), whereby the tube ends are fixed in a sealed manner to the header plate upon brazing of the tube / header assembly.

[0045] Referring to the orientation of the Figs, the header plate 16 may generally extend along a main extension plane ZX, i.e. where the header length is along axis Z and the header width along axis X. The tubes extend along axis Y, which is also the tubes’ insertion direction. Direction Y further corresponds to the assembly / mounting direction of the header plate 16 to the tank 14, as well as to the opening direction of the cavity 15.1. Direction Y is thus herein also referred to as axial direction. The header plate 16 globally extends perpendicularly to the axial direction Y in plane ZX. Upon assembly with the tank 14, the frame 16.4 of the header plate 16, i.e. the rectangular, peripheral edge / border of the header plate 14 in plane ZX is in contact with the gasket 42 and compresses the latter against the tank foot 12.

[0046] A plurality of clinching members is provided along the longitudinal and transverse edges of the header plate. In this embodiment, the clinching members take the form of clinching tabs that are connected to the longitudinal and transverse edges via respective sidewalls.

[0047] As can be seen from the drawings, a first plurality of clinching members 22, hereinafter the first tabs, are distributed along the longitudinal edges 20 and clinched over the foot portion 12 of the header tank 14. That is, the first tabs 22 extend from the edge of the longitudinal side walls 24 and are bent over the foot portion 12, such that a terminal portion 26 of the tab faces a clinching surface of the foot portion, extending transversally to axis Y.

[0048] A second plurality of clinching members 32, also referred to as second tabs, are distributed along the transverse edges 30. By design, the second tabs 32 have a length that is greater than that of the first tabs 22, because they are not clinched over the foot portion 12 but they lock on respective clinching surfaces 52 that are defined by transverse ribs 50 located on the tank rearwardly from the tank foot 12 (i.e. further away from the header plate in direction Y), referred to as additional clinching rib 50. The second tabs 32 extend from the transverse sidewalls 34 over the foot portion 12 and are bent over the transverse ribs 50.

[0049] It may be noted that each additional clinching rib 50 may be formed continuously over a respective outer transverse side of the tank body 14.1 with a length along the X axis substantially identical to the width of the header tank body, i.e. it can extend on a transverse side from one edge of the tank body toward a second edge. However, other designs are possible and the transverse rib may be formed by sections over the respective outer transverse side of the tank body and / or the transverse rib may have a length shorter than the width of the tank body, while being sufficient for enabling a connection by clinching of the header plate.

[0050] Axial reinforcement ribs 54 (see Fig.3) may be provided on the outer surface of the header tank body 14.1 , extending axially (along Y) from the transverse rib 50 to the foot portion 12 of the header tank 14. Reinforcement ribs 54 are designed so as not to hinder clinching of the second plurality of clinching members 32 over the transverse ribs 50. In particular, the additional reinforcement ribs 54 may extend between adjacent transverse clinching members 32.

[0051] As illustrated, both the transverse 32 and longitudinal clinching members 22 may be formed as rectangular tabs; however, any appropriate design may be used, and the first and second tabs 22, 32 may be of similar or different dimensions along their respective edge of the header plate.

[0052] The transverse and longitudinal sidewalls 24, 34 have a same axial width W1 (along axis Y), but the second tabs 32 have a greater length than the first tabs 22. The length is here understood as the length of the unfolded, straight tab, measured from the edge of sidewall to the free edge of the tab.

[0053] In order to facilitate the clinching process, the tabs 22, 32 are pre-bent, as well as their supporting sidewalls 24, 34.

[0054] More specifically, before assembly of the header plate to the tank, the longitudinal sidewalls 24 are outwardly bent and the first (longitudinal) clinching members 22 are inwardly bent. In the present text, outwardly refers to a direction away from the inside of the header tank body 14.1 , i.e. away from the header tank cavity 15.1. On the contrary, inwardly refers to a direction toward the inside of the header tank body 14.1 , i.e. toward the header tank cavity 15.1 . When referring to the header plate 16 in an unassembled state (i.e. before assembly of the header plate to the tank) outwardly means the formation of an obtuse angle 01 between a longitudinal sidewall 24 and a transverse edge 30 of the header plate 16. On the contrary, inwardly means the formation of a sharp angle 02 between a longitudinal clinching member 22 and a transverse edge 30 of the header plate.

[0055] The obtuse angle Oi between the longitudinal side walls 24 and the header plate 16 may be between 92 and 125°, i.e. 2 to 35° relative to axis Y.

[0056] During assembly of the header plate 16 to the tank 14, the latter are first brought in contact with one another, with the gasket in place, to close the cavity. Then clinching (see Fig.4) is obtained by inwardly (i.e. toward the header tank body 14.1 ) folding the longitudinal sidewalls 24 to bring the first tabs 22 over the tank foot portion 12.

[0057] The second tabs 32 extend from the edge of the respective transverse sidewall 34 through a first portion 36 extending over the foot portion 12 of the header tank up to a second portion 38, which is bent over the respective transverse rib 50 and extends up to a free edge. Hence, the second portion 38 faces a locking surface 52 of the additional transverse rib 50.

[0058] It may be noted that whereas the clinching operation is described as folding the first and then the second clinching members, the inverse is also possible, or they may be folded concomitantly.

[0059] The configuration of the second tabs 32 before assembly is as follows. The second tabs comprise a first portion 36 with a straight base section 36.1 (in straight continuity of the sidewall 34) and an outwardly bent intermediate section 36.2 connecting the second portion 38, which is inwardly bent relative to the intermediate section 36.2. Preferably, the intermediate sections 36.2 are outwardly bent with an angle between 15° and 35°, preferably an angle of about 25°, so that an angle 03 between 105° and 125°, preferably of about 115° is formed between the intermediate section 36.2 and a longitudinal edge 20 of the header plate 16. Additionally or alternatively, the second portions 38 form an angle 04 about 90° relative to the respective intermediate sections 36.2. After assembly the intermediate sections 36.2 are aligned with the Y axis.

[0060] As will be understood, the various angles can be varied. The inclination of the longitudinal sidewalls 24 and of the intermediate portions 36.2 of the second tabs 32 are designed to allow passage of the tank foot 12 during assembly. It may be noted that transverse sidewalls 34 preferably extend parallel to axis X, i.e. 90° relative to the header plate plane.

[0061] It will be appreciated that the present design results in less forces being applied to the tabs 22, 32 during the clinching operation to clinch the tank 14. The tank has an additional transverse rib 50 in the vicinity of the tank foot, which confers more rigidity. The shape of the second tabs 32 facilitates insertion of the tank foot and reduces the forces required for their clinching. In particular, the second tabs 32 are easier to bend due to their increased length, hence resulting in less forces applied to the tank foot and less risks of deformation thereof or of the first tabs.

[0062] Another benefit of the design is that the transverse sidewalls 34, from which the second tabs 32 extend, is not bent during clinching. They thus make a proper support for the heat exchanger reinforcement member, which can be brazed to the transverse sidewall 34.

Claims

CLAIMS1 . A tank assembly for a heat exchanger (10) comprising a tank (14) having a tank body (14.1 ) defining a cavity (15) for a fluid, an axial tank opening of the cavity (15.1 ) being delimited by a peripheral foot portion (12) having longitudinal and transverse sections; a header plate (16) closing the tank opening (15.1 ) and attached by clinching to the tank, the header plate (16) having a rear side facing the cavity (15.1 ) and an opposite front side, wherein the header plate (16) comprises oblong through-holes (16.1 ) extending transversally, said through-holes (16.1 ) being adapted for receiving respective end portions of heat exchanger tubes; wherein the header plate (16) comprises longitudinal edges (20) and transverse edges (30), a plurality of clinching members (22, 32) being connected to said edges and clinched onto said tank body (14.1 ); wherein the clinching members comprise: a plurality of first clinching members (22) distributed along the longitudinal edges (20) and clinched over the foot portion (12); a plurality of second clinching members (32) distributed along the transverse edges (30), characterized in that the second clinching members (32) are clinched over respective transverse clinching surfaces (52) provided on the tank body (14.1 ) and located rearwardly from the foot portion (12).

2. The tank assembly according to claim 1 , wherein the header plate (16) comprises respective transverse sidewalls (34) extending along the transverse edges (30), and the second clinching members (32) extend from an edge of the transverse sidewalls (34).

3. The tank assembly according to claim 2, wherein the second clinching members (32) extend from the edge of the transverse sidewalls (34) through a first portion (36) extending over the foot portion (12) up to the respectivetransverse surface (52), to a second portion (38), which is bent over the respective transverse surface (52).

4. The tank assembly according to claim 3, wherein, the first portion (36) of the second clinching members (32) comprises a straight base section (36.1 ) and an intermediate section (36.2) connecting the second portion (38), which is inwardly bent relative to the intermediate section (36.2).

5. The tank assembly according to claim 4, wherein in the assembled configuration the intermediate sections (36.2) are axially aligned with the base sections.

6. The tank assembly according to any one of claims 3 to 5, wherein in the assembled configuration the second portions (38) form an angle (04) between 90 and 100° relative to the intermediate sections (36.2), preferably about 90°.

7. The tank assembly according to any of the preceding claims, wherein the tank (14) comprises a transverse rib (50) parallel to each transverse section of the foot portion (12), the transverse ribs (50) defining the transverse clinching surfaces (52).

8. The tank assembly according to any of the preceding claims, wherein the second clinching members (32) have a greater length than the first clinching members (22).

9. The tank assembly according to claim 8, wherein the length of the second clinching members (32) is at least 1.5 or 2.5 times that of the first clinching members (22).

10. The tank assembly according to any of the preceding claims, wherein the first (22) and / or second clinching members (32) are formed as rectangular tabs.11 . The tank assembly according to any of the preceding claims, wherein the header plate (16) comprises respective longitudinal sidewalls (24) extending along the longitudinal edges (20), and the first clinching members (22) extend from an edge of the longitudinal sidewalls (24).

12. The tank assembly according to any of the preceding claims, wherein a circumferential sealing element (42) is arranged between the foot portion (12) and the header plate (16).

13. A heat exchanger (10) comprising a tank assembly according to any of the preceding claims and a plurality of heat exchanger tubes (11 ) having a respective first end engaged in the oblong through holes (16.1 ) of the header plate (16), a respective second end of the heat exchanger tubes being fluidly connected to a second tank assembly.

14. A method of assembling a header plate and tank, comprising providing a tank having a tank body (14.1 ) defining a cavity (15) for a fluid, an axial tank opening of the cavity (15.1 ) being delimited by a peripheral foot portion (12) having longitudinal and transverse sections; providing a header plate (16) having a rear side facing the cavity (15.1 ) and an opposite front side, wherein the header plate (16) comprises oblong through-holes (16.1 ) extending transversally, end portions of heat exchanger tubes being received in said through-holes (16.1 ); wherein the header plate (16) comprises longitudinal edges (20) and transverse edges (30), a plurality of first clinching members (22) distributed along the longitudinal edges, a plurality of second clinching members (32) distributed along the transverse edges (30); positioning the header plate on the tank so as to close the tank opening; clinching the header plate to the tank, said clinching comprising: clinching the first clinching members (22) over the foot portion; and characterized by clinching the second clinching members (32) over respective transverse clinching surfaces (52) provided on the tank body (14.1 ) and located rearwardly from the foot portion (12).

15. The method to claim 14, wherein before assembly of the header plate to the tank, the first portion (36) of the second clinching members (32) comprises a straight base section (36.1 ) and an outwardly bent intermediate section (36.2)connecting the second portion (38), which is inwardly bent relative to the intermediate section (36.2).

16. The method according to claim 15, wherein before assembly the intermediate sections (36.2) are outwardly bent with an angle between 15 and 35°, preferably of about 25°.

17. The method according to claim 15 or 16, wherein the second portions (38) form an angle between 90 and 100° relative to the intermediate sections (36.2), preferably about 90°.

18. The method according to any one of claims 14 to 17, wherein the tank (14) comprises a transverse rib (50) parallel to each transverse section of the foot portion (12), the transverse ribs (50) defining the transverse clinching surfaces (52).

19. The method according to any one of the claims 14 to 18, wherein the second clinching members (32) have a greater length than the first clinching members (22).

20. The method according to any of the claims 14 to 19, wherein the header plate (16) comprises respective longitudinal sidewalls (24) extending along the longitudinal edges (20), and the first clinching members (22) extend from an edge of the longitudinal sidewalls (24).

21. The method according to claim 20, wherein before assembly of the header plate to the tank, the longitudinal sidewalls (24) are outwardly bent and the first clinching members (22) are inwardly bent, and whereby clinching is performed by inwardly folding the longitudinal sidewalls (24) to bring the first clinching members (22) over the tank foot portion (12).

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