GB2074054A

GB2074054A - Manufacturing heat exchangers

Info

Publication number: GB2074054A
Application number: GB8012769A
Authority: GB
Original assignee: Rover Co Ltd
Current assignee: Rover Co Ltd
Priority date: 1980-04-17
Filing date: 1980-04-17
Publication date: 1981-10-28
Also published as: FR2480654A1; GB2074054B; FR2480654B1

Abstract

A heat exchanger such as an automobile radiator, has a header tank formed by a header tank shell (11) attached to a tube plate (13). Flanges (14, 15) on the aforesaid components are clenched at the joint during manufacture to hold the components together while solder is run along the joint by capillary action by virtue of the small gaps between the clenched flanges. The method of manufacture is automated employing a number of stations for performing various tasks such as adding flux and solder, heating and cooling. <IMAGE>

Description

SPECIFICATION Improvements relating to heat exchangers This invention relates to heat exchangers and a method and apparatus for their manufacture.

Heat exchangers are well known which comprise a plurality of tubes in a matrix which communicate with a headertankconsisting of a headertankshell and a tube plate, the tubes being received in apertures in the tube plate and being secured thereto. Automobile radiators are commonly of this construction.

Atypical manufacturing processofsuch heat exchangers involves the following steps. The header tank shell is dipped by hand in a bath of solder to produce a bead of solder around a flange at its edge.

The dipping is a skilled operation and control over the quantity of solder used and its distribution is limited and a function of the operator's experience and ability. The shell is then fluxed by hand either by dipping or painting, and is assembled to a tube plate on a radiator block with the tank shell flange located in a channel-shaped flange on the tube plate. The assembly is then clamped together and heated in a burner to melt the solder so that it repositions itself along the joint between the shell and the tube plate.

The radiator is thereafter cooled to solidify the solder and the clamping force removed. Automation of this process is difficult since it is difficult to reliably achieve a satisfactory bead of solder by automatic dipping of the tank edge whilst at the same time using an economic quantity of solder.

The invention provides a method of manufacturing a heat exchanger having a header tank shell and a tube plate, the joint between said shell and said tube plate including a channel-shaped flange on one said component which receives a flange on the other said component, including the steps of clenching said tank shell and said tube plate together at said flanges, of heating said flanges and of adding solder to said joint.

It will be appreciated that the term solder includes any alloy which can be added to the joint in a molten state and solidifies on cooling to secure the joint, the term is thus not limited to hard and soft solders.

Preferably, the method includes the step of clenching the flanges such as to enable solder to be drawn along the joint by capillary action.

The solder may be added to the joint in the form of slugs which melt during heating and run along the joint, or molten solder may be added to the already heated joint.

Preferably the joint includes portions which are arranged to receive and contain the solder prior to its passing along the joint.

Preferably the method includes the step of dispensing a pre-determined amount of flux to said joint. The flux may be added to the joint at discreet locations and run along the joint.

The invention further extends to apparatus for manufacturing a heat exchanger, comprising means for supporting a heat exchanger assembly, means for clenching together flanges on a header tank shell and a tube plate, and means for heating the joint between said flanges.

The apparatus may include means for dispensing solder to said joint, preferably a pre-determined amount of solder either in the form of slugs or in molten form.

Preferably the means for clenching is arranged to clench the flanges over a substantial distance and such as to form a clenched joint along which solder will run by capillary action.

The apparatus may consist of a number of stations at which different operations are performed, the support means enabling a heat exchanger to be moved between stations. Preferably the support means includes means for propelling the heat exchanger between stations.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a flow diagram of a method in accordance with the invention.

Figure2 is a transverse cross section of a radiator in accordance with the invention.

Figure 3 is a side view of the radiator of Figure 2, and Figures 4 and 5 are enlarged cross sectional views of a joint between the header tank and the tube plate of the radiator of Figures 2 and 3, before and after clenching, respectively.

Figure 1 shows the sequence of operations carried out in a method according to the invention. The operations can be readily carried out automatically by an appratus which supports and transports the radiator components linearly between stations equipped with devices for performing the various steps, such as dispensing a pre-determined amount of flux and so on, as will be described below.

A header tank shell 11 (Figures 2 and 3) and a radiator block 12 including a tube plate 13, soldered to a plurality a tubes which are to communicate with the space within the header tank in the finished radiator, are first assembled. A flange 14 (Figure 4) extending around the lower edge of the header tank is received in a channel-shaped flange 15 extending around the edge of the tube plate. Slugs of solder of pre-determined size are next located at each end of the joint, between the header tank shell and upward extensions 16 of the flange 15.

The flanges 14 and 15 are then clenched to reduce the space between them and to provide that flange 15 grips flange 14 to retain the tank shell on the tube plate, as shown in Figure 5.

Thereafter a pre-determined amount of liquid flux is dispensed from nozzles (not shown) into the end portions of the joint deepened by the extensions 16, wherein the solder slugs are located. The flux then runs the length of the joint in the channel-shaped flange 15.

The radiator assembly with solder and flux added is transported to a burner station including a plurality of burning gas jets directed at the joint, in a similar arrangement to known burners. The solder is melted and in its molten state flows along the joint, at least partly drawn by capillary action, the capillary forces being significant by virtue of the small gap between the clenched flanges. Heating is continued for a pre-determined time to ensure that the solder is able to flow around the entire joint to effect an air and watertight seal between the tank shell and the block.

The radiator is then transported to a cooling station and finally unloaded, as in conventional methods of manufacture.

Thus compared to a typical manufacturing process hitherto, there is no requirement to exert a clamping force between the tank shell and the block to correctly position on them initially and subsequently to prevent their disassembly until the solder solidifies, firstly because the fit of the flanges is unimpaired by the presence of a variable thickness bead of solder, and secondly because clenching the joint automatically prevents disassembly. Thus the damage to tube-to-tube-plate joints in the block sometimes caused by clamping is also avoided. Moreover, the need to dip the tank shell to collect solder for the joint is avoided, while the solder applied is of a pre-determined and relatively small quantity since the gaps between the flanges are smaller than in prior art joints.

Moreover, because solder is applied after assembly of the tank shell and block the flange 14 always seats correctly in flange 15, while in the final joint strength is enhanced both by the mechanical grip of one clenched flange on the other and by the smaller volume of solder between the flanges. The use of pre-determined quantities of flux and solder enable minimum wastage and hence a cost advantage, whilst the standardization of the manufacturing process means that that average quality of the products can be higher than hitherto. The standardization also enables the use of less heat, which further reduces the risk danger to the tube-to-tubeplate joints.

Alternative arrangements may readily be envisaged, such as use of a two stage burner which first heats the solder slugs and then both the near-molten slugs and the entire joint to ensure the solder runs.

Moreover the solder may be added in molten form through a nozzle while the joint is heated. Again, whilst heating by gas burners has been referred to, other heating means may be used instead, such as infra-red high frequency heaters.

Whilst it is considered convenient in the present circumstances to move the radiator between stations to perform the different operations since this enables each piece of apparatus to be kept in constant use, it would, of course, be possible to perform a method in accordance with the invention at a single location.

Claims

1. A method of manufacturing a heat exchanger having a header tank shell and a tube plate, the joint between said shell and said plate including a channel shaped flange on one said component which receives a flange on the other said component, including the steps of clenching said tank shell and said tube plate together at said flanges, of heating said flange and of adding solder to said joint.

2. A method as claimed in claim 1, wherein said channel-shaped flange is on said tube plate.

3. A method as claimed in claim 1 or 2, wherein said flanges are clenched such as to enable solder to be drawn along the joint by capillary action.

4. A method as claimed in claim 1, 2 or 3, wherein solder is added to the joint in the form of slugs which melt into the joint.

5. A method as claimed in claim 1, 2 or 3, wherein molten solder is added to the joint.

6. A method as claimed in any preceding claim, wherein a pre-determined quantity of solder is added to the joint.

7. A method as claimed in any preceding claim, wherein the solder is added to portions of the joint which are adapted to receive and contain the solder prior to its passing along the joint.

8. A method as claimed in claim 7, wherein said adapted portions have a flange of extended height.

9. A method as claimed in claim 8, including the step of adding a pre-determined quantity of liquid flux to said joint.

10. A method of manufacturing a heat exchanger substantially as hereinbefore described with reference to the accompanying drawings.

11. A heat exchanger manufactured according to the method of any one of claims 1 to 10.

12. Apparatus for manufacturing a heat exchanger, comprising means for supporting a heat exchanger assembly, means for clenching together flanges on a header tank shell and a tube plate of the heat exchanger, and means for heating the joint between said tank shell and said tube plate.

13. Apparatus as claimed in claim 12, including means for dispensing solder to the joint between the header tank shell and the tube plate.

14. Apparatus as claimed in claim 13, including means for dispensing molten solder to said joint.

15. Apparatus as claimed in claim 12, 13 or 14, wherein said clenching means is arranged to clench said flanges over the substantial portion of the said joint.

16. Apparatus as claimed in any one of claims 12 to 15, including a plurality of stations at which different tasks are performed, said support means enabling a heat exchanger to be moved between stations.

17. Apparatus as claimed in claim 16, wherein the support means includes means for propelling the heat exchanger between stations.