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(11) | EP 0 153 138 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method of and apparatus for manufacturing heat exchangers and components for heat exchangers |
| (57) A method of manufacturing heat exchangers comprises holding two lengths of header
piping in mutually parallel relationship and advancing the header piping step-by-step
through a series of work stations to enable operations to be performed at the work
stations, locating heat exchange elements relative to the header piping so that an
aperture at each end of each heat exchange element is aligned with an aperture in
each length of header piping, welding the apertured heat exchange elements to the
header piping and subsequently cutting the assembly of header piping and heat exchange
elements to form radiators of predetermined size. The invention also provides apparatus
for carrying out the method and radiators made by the method. The invention further provides a method of closing the open ends of a flat metal tube using a pair of grooved rollers, each of which is alternately pressed down on and moved across the open end of the tube, causing the material of the tube to be pressed inwardly, thereby closing the open end of the tube. |
[0001] The present invention relates to heat exchangers and in particular to heat radiators of the kind in which a plurality of mutually parallel flat heat exchange tubes are connected between a pair of header pipes, and is concerned with a novel and automated method of and apparatus for manufacturing such radiators. The invention is also concerned with a novel method of and apparatus for closing the ends of the flat metal tubes used in the manufacture of such radiators.
[0002] The invention accordingly provides a method of manufacturing heat exchangers, the method comprising the following steps:
holding two lengths of header piping in mutually parallel spaced apart relationship and feeding the header piping in steps through a work station;
locating a heat exchange element in contact with the header piping so that an aperture adjacent each end of the heat exchange element is aligned with an aperture in the contiguous length of header piping;
welding each end of the heat exchange element to the header piping to provide a mechanical joint and seal between the piping and the heat exchange element and so as to enable fluid communication between the interior of the piping and the heat exchange element; and
advancing the piping and connected heat exchange element beyond the connection work station.
[0003] Advantageously, the method includes the steps of pre-forming and pre-cleaning the apertures in the header piping to facilitate resistance welding of the heat exchange elements to each length of header piping.
[0004] In a further step in the method, the header piping, to and between which heat exchange elements have been connected, is cut into predetermined lengths at a subsequent cutting station to form discrete radiator assemblies.
[0005] The header piping which bends at the connection station, during connection of a heat exchange element to and between the header piping, is corrected by deliberately induced contra bending.
[0006] Advantageously, baffles are inserted into the header piping, between selected heat exchange elements, for routing the flow of heat exchange fluid through the heat exchange elements, the baffles being preferably of resiliently deformable non-perishable material such as silicone rubber. Each baffle may have a hole into which is inserted a tool having a length greater than the length of the hole, the tool being used to push the baffle along the pipe to the desired location.
[0007] The invention also provides apparatus for manufacturing heat exchangers, the apparatus comprising;
holding means for holding two lengths of header piping in mutually parallel spaced apart relationship and for feeding the header piping in steps through and beyond a work station;
locating means for positioning a heat exchange element relative to the header piping so that an aperture adjacent each end of the heat exchange element is aligned with an aperture in the contiguous length of header piping; and
welding means at the work station for welding each end of the heat exchange element to the contiguous header piping to provide a mechanical joint and seal between the piping and the heat exchange element and so as to enable fluid communication between the interior of the piping and the heat exchange element.
[0009] The invention also provides a double heat exchanger comprising two heat exchangers each provided with one generally semi-circular section header pipe, the two semi-circular header pipes being joined back-to-back such that the two header pipes have a generally circular composite section, the double heat exchanger being assembled from two heat exchangers made by the method or apparatus of the invention, and being provided with a single circular fluid connection at each end of the joined header pipes, providing fluid access and exits to each half of the joined header pipe.
[0010] The invention also provides a method of closing the ends of "flat" metal tubes. By "flat" tubes is meant tubes which have two flat parallel closely spaced apart side walls. Flat tubes have a large surface to volume ratio and are thus useful in heat exchangers, for example in central heating radiators. In such applications, a heat exchange element is formed by cutting a length of flat tubing, closing and sealing the two ends of the length, and providing a small aperture or apertures adjacent each end of the length as an entry and exit for the heat exchange fluid. When the heat exchange element is intended for a column radiator, the apertures are generally provided on the curved part of the sidewall or on the folded over end of the element. When the heat exchange element is intended for a panel radiator the apertures are generally provided on the flat part of the sidewall.
[0011] The method of closing an open end of a metal tube having two mutually parallel side walls joined by a pair of curved ends, comprises the use of a roller having a shaped circumferential groove to fold inwardly the curved ends and then the side walls of the open end of the tube while the roller is passed across the open end of the tube from one end towards the other and pressed into engagement with the tube so that the tube end is within the groove, two roller passes being made one after the other and in opposite directions, one starting from beyond each corner. The folded in end is preferably sealed by tungsten inert gas welding.
[0012] Advantageously, the first roller pass extends less than half the length of the end of the tube and the second roller pass extends more than half the length and overlaps the first roller pass.
[0013] The roller employed should ideally have a profile such that a clearance is left between the cheek of the roller and the side walls of the tube.
[0014] Advantageously, two pairs of rollers are employed, one at each end of the tube, so that the tube may be sealed in an automatic or semi-automatic fashion, the distance between the pairs of rollers being finely adjustable.
[0015] The invention also provides apparatus for closing an open end of a flat metal tube having two mutually parallel side walls joined by a pair of curved ends, the apparatus comprising a roller having a shaped circumferential groove to fold inwardly the curved ends and then the side walls of the open end of the tube while the roller is passed across the open end of the tube from one end towards the other and pressed into engagement with the tube so that the tube end is within the groove, and means for pressing the roller into engagement with the end of the tube and for driving the roller along the end of the tube.
[0016] The invention further provides a heat exchange element comprising a flat metal tube the ends of which have been closed and/or sealed by the method or by the apparatus referred to above.
[0017] The invention will now he described more particularly, by way of example, with reference to the accompanying drawings, in which:
Figures la, Ib and lc are front elevation, end elevation and plan views respectively of a column radiator;
Figures 2a and 2b, which are to a larger scale, are sectional end and sectional front elevations respectively of the upper left hand corner of the column radiator of Figure 1;
Figures 3a and 3b are schematic plan and side elevation views respectively of apparatus for manufacturing column radiators by the method of the invention;
Figures 4a and 4b are side and end elevations respectively, to an enlarged scale, of a detail of the apparatus shown in Figure 3, namely the welding work station;
Figure 5 illustrates, to an enlarged scale, a detail of the apparatus shown in Figure 3, namely a work station for reverse bending of piping bent in the welding work station, Figure 5a showing side and end elevations of the station and piping before reverse bending and Figure 5b showing similar views during reverse bending, the bending being shown exaggerated for purposes of illustration;
Figures 6a, 6b and 6c are rear, side and front elevations respectively of a baffle;
Figure 7 is a sectional side elevation of the baffle and baffle insertion tool;
Figures 8a to 8e illustrate successive stages in the formation off a double column radiator from two single radiators made by the method of the invention, and each show an end elevation and a plan view of a top corner of the double radiator;
Figures 9a and 9b are sectional plan views, to an enlarged scale, of the top corners of the double column radiator illustrated in Figure 8, showing a socket on the header before and after welding respectively;
Figures 10a to 10d illustrate successive stages in the method of closing and sealing the ends of a flat metal tube, and each show a view of the end of the tube together with a partial view of the side wall, near the end;
Figures lia to lld are sections taken on XI-XI of Figures 10a to 10d respectively;
Figures 12a to 12f are partial sectional elevation views showing the rollers at successive stages of closing over the edges of one end of the tube;
Figures 13a and 13b are side elevations and end elevations respectively of a roller, illustrating the shape and dimensions (in millimetres) thereof;
Figures 14a and 14b illustrate the dimensions (in millimetres) of the end of a flat tube, and are respectively views of the end and of the part of the side wall near the end;
Figures 15a and 15b illustrate rollers closing the ends of a tube, and are respectively a sectional view on a flat side wall of the tube and a view of the end of the tube;
Figures 16a and 16b are plan and sectional side elevations respectively of apparatus for making heat exchange elements, including closing and sealing flat metal tubes by the above method, the heat exchange elements being suitable for column radiators;
Figures 17, 18, 19 and 20 are each end elevation views of work stations in the apparatus of Figures 16a and 16b, namely rolling, punching, welding and cleaning stations;
Figures 21a and 21b are views similar to Figures 16a and 16b respectively of apparatus for making heat exchange elements suitable for panel radiators;
Figure 22 is a view of a flat side wall of one end of a flat metal tube whose side walls have been depressed in the region around the fluid apertures so that the fluid apertures stand proud for resistance welding purposes, while Figures 22a to 22c are sectional views thereof;
Figure 23a is a sectional side elevation, as seen from one end of a flat metal tube, showing the forming tool for depressing the side walls, while Figures 23b and 23c are sectional views thereof.
[0018] Referring again to Figures la, lb, lc, 2a and 2b of the drawings, there is shown in those figures a column radiator comprising headers 1 connected by a series of heat exchange elements 2, which are made from "flat" metal tubes closed and sealed at each end. Corresponding water entry and exit apertures 3 (see Figures 2a and 2b) are provided on the headers 1 and on the curved part of the side walls of the heat exchange element 2.
[0019] A method of and apparatus for manufacturing the heat exchangers, including assembling the heat exchange elements 2 to the headers 1, will now be described. During the description, it will be assumed that the heat exchange elements 2 have already been prepared from flat metal tubes. The preparation of the heat exchange elements will be described later.
[0020] Figures 3a and 3b illustrate the method and apparatus. Two long lengths of piping 10 are fed to the apparatus in mutually parallel spaced apart relationship. The spacing between the lengths 10 is set to accommodate a given length of heat exchange element 2. One side of the apparatus is movable so that the spacing can be adjusted, to enable batches of heat exchange elements 2 of different lengths to be assembled to headers 1 to give assemblies of different width between headers. One of the heat exchange elements 2 from the batch can be used as a direct measure for setting the width of the apparatus.
[0021] The lengths of piping 10 are then advanced automatically through the apparatus, step-by-step, one heat exchange element pitch at a time. This step-by-step advance is achieved by means of a feed system using fixed clamps 16, 17 and 18 to hold the piping between steps and moving clamps 19 and 20 to effect the steps.
[0022] Between steps, when the lengths of piping 10 are stationary, a number of operations are carried out in a sequence of workstations.
[0023] In the first pair of workstations 21, apertures 3 for the entry and exit of fluid are drilled in the piping 10. These apertures 3 should be at least 5 mm in diameter. In the next pair of workstations 22, the region of the piping 10 in which the fluid apertures 3 have been formed, is cleaned in preparation for subsequent resistance welding. Cleaning is effected by means of rotating wire brushes 22a which descend on the surface of the piping 10.
[0024] In the next pair of workstations 23, a heat exchange element 2 is brought into contact with the lengths of piping 10, with the apertures 3 on the heat exchange element 2 in alignment with the apertures 3 in the lengths of piping 10, between the throats of two resistance welding presses 24, one at each end of the heat exchange element 2. The heat exchange element 2 may be manually loaded into the apparatus or may be fed automatically from the apparatus which prepares it, and which is described in more detail below.
[0025] In the case of manual loading, the heat exchange element 2 is loaded into position in workstation 23 as indicated by arrows 25 in Figures 3a and 3b. The heat exchange element is held with its flat faces vertical by means of the fixed entry guide ramps 26 and the vertical guide pins 27. The pins 27 are extended, as shown in Figure 3h, during loading and positioning of the heat exchange element 2 but are retracted after the heat exchange element 2 is welded to the piping 10 to allow the assembly move forward in the apparatus.
[0026] In the case of automatic loading, the heat exchange element 2 is automatically transferred from the apparatus for preparing the heat exchange elements to the work station 23 by means of either a robot or by a special purpose conveying device which discharges the heat exchange element 2 onto the fixed guide ramps 26 and allows the heat exchange element 2 to fall into the correct position.
[0027] Figure 3b shows a heat exchange element which has just entered work station 23. The welding press has both its upper electrode 30 and its lower electrode 31 withdrawn. Figures 4a and 4b show the same heat exchange element 2, hut with the electrodes 30 and 31 closed. The lower electrode 31 ascends to meet the piping 10, the upper electrode 30 descends onto the heat exchange element 2, the side plate 32 of the upper electrode 30 closes inwards to precisely locate and to make hetter electrical contact with the heat exchange element 2, and the resistance weld is then effected.
[0028] As the resistance weld cools, it causes the piping 10 to bend concavely in the region of the heat exchanqe ejement 2, as depicted in Figure 5a. This distortion can he removed by bending the piping 10 in the opposite direction, also as part of the step-by-step process. This reverse or corrective bending can be very conveniently carried out in the welding press using the fixed clamps 17 and 18 to hold the piping 10 and using the bottom electrode 31 to push the piping 10 upwards thereby bending it in the opposite direction, as shown in Figure 5b. When released, the piping 10 springs back to its original straight condition.
[0029] Thus there emerges from the machine, step-by-step, an assembly comprising two long lengths of piping 10 connected by a series of heat exchange elements 2.
[0030] The emerging assembly is cut into suitable lengths for heat exchangers, such as central heating radiators, by a pair of rotating saw blades 33.
[0031] Referring now to Figures 6 and 7, the next stage before closing the open ends of the headers 1 is to insert baffles, if required, into the headers 1 to route the hot water through the heat exchange elements 2. The above-described drilling and resistance welding of the piping 10 may preclude subsequent insertion of conventional metal baffles into the resulting headers 1. (In known manual production methods the metal baffles are inserted before the drilling and resistance welding). Baffles 40 made of silicone rubber are used instead. Silicone rubber is flexible and water resistant. Because of its flexibility, the baffle 40 may be pushed past obstacles inside the header to reach the desired location. The baffle 40 comprises a cylindrical piece of rubber provided with an axial blind hole 40a. The baffle 40 is pushed along the header 1 by means of a spigot 41 inserted in the blind hole 40a. The spigot 41 is used to push the baffle 40 along the inside of the header 1. If the baffle 40 encounters an obstacle, the spigot 41 causes the baffle 40 to stretch axially and thereby contract radially thus easing passage past the obstacle. The spigot 41 is made longer than the blind hole 40a and is provided with a shoulder 41a to prevent it inadvertently breaking through the baffle 40.
[0032] Finally, the cut ends of the radiator headers 1 are closed. Where the headers are round in section, they are plugged with turned steel plugs (not shown) which are tapered and are a "drive" fit in the ends of the headers 1. The plugs are driven into position by means of a hand held powered impact hammer. The plugs are then sealed in position hy, for example, TIG welding. The plugs may incorporate entry, exit or air vent tappings.
[0033] Referring now to Figures 8 and 9, double column radiators may be made by the above method. The method is carried out as described above, but using piping which is semi-circular in section. Figure 8a shows two single column radiators which are to be joined and interconnected to form a double radiator. Semi-circular section headers 1 are used at both the top and bottom of the radiators. The radiators are arranged with the semi-circular headers back to back as shown in Figure 8b. The seam 50 between the ends of the headers 1 is then sealed as shown in Figure 8c. Sealing is effected by welding. The weld is continued a short distance along the length of the headers 1. A steel plug or socket 51 is then positioned at the end of the headers 1. As shown in Figure 8d, the plug 51 comprises a shallow cylindrical bore which locates over the end of the headers 1. The plug 51 is then welded circumferentially to the headers, as shown in Figure 8e. Care is taken to ensure that the circumferential weld meets the lengthwise continuation of the weld between headers. The above described combination of welds and plug ensure a fluid tight radiator end, and a balanced entry and exit of fluid to both sections of the double radiator.
[0034] Alternatively, a double column radiator may be made by connecting heat exchange elements 2 to both sides of the two lengths of piping 10 as they advance through the apparatus
[0035] The method of preparing the heat exchange elements will now he described in more detail. Referring to Figure 10 of the drawings; Figure 10a shows the open end of the flat metal tube before the commencement of the method; Figure 10b shows the end of the tube after the first roller pass; Figure 10c shows the end of the tube after the second roller pass, and shows the seam 100; and Figure 10d shows the end of the tube after the seam 100 has been sealed by TIG welding. Figures lla to lid are sections on Figures 10a to 10d respectively.
[0036] Referring to Figure 12, which shows one end of the tube only, the method is carried out in automated fashion by four rollers, two at each end of the tube. The first roller 101 at each end is moved across the end, thereby making a pass (Figure 12b) and is then withdrawn (Figure 12c), and the second roller 102 at each end is moved across the end, thereby making a pass (Figure 12e), and is then withdrawn (Figure 12f).
[0037] The seam 100 may be sealed in any one of a number of ways, for example, by welding, brazing, soldering, or sealing with an adhesive or sealing compound. The preferred method is TIG welding which gives a very neat finish.
[0038] As will be noted from Figure 10c, the seam 100 lies in a single straight line in one plane, and thus lends itself to being sealed in a simple and automated fashion.
[0039] It has been found that each roller has a tendency to form a bulge in the tube material as the roller operates to close the end of a tube. It is desirable to prevent a noticeable bulge or blemish on the finished tube where the two roller passes meet. It has been found advantageous, when using the roller profile and dimensions shown in Figure 13 and the tube dimensions shown in Figure 14, that the first roller pass should extend less than halfway and preferably about one third of the way along the length of the end of the tube, and that the second roller pass should then extend about three quarters of the way along the length of the end of the tube in the opposite direction. Thus any bulge created by the first roller pass is pushed towards one end of the tube end by the second roller pass. The bulge of the second pass meets the bulge of the first pass not at the centre of the end of the tube where collapse or distortion of the side walls might take place hut, instead, sufficiently close to the end to take advantage of the relatively high strength of the formed end.
[0040] The rollers have a profile very similar to that desired on the finished closed tube end, but a tapered clearance is desirable between the tubes and the side cheeks of the roller to prevent rubbing between them, and to allow easy access of the roller onto the tube end.
[0041] The diameter of the roller is also important in producing a good finish. Too large a diameter will produce too much downward pressure under the roller relative to the necessary forward pressure and may cause collapse of the tube side walls. The roller diameter shown in Figure 13 has been found suitable for the mild steel tube profile shown in Figure 14.
[0042] The pressure exerted by the rollers on the ends of the tubes is also important in giving a neat finish. Too high a pressure may cause the walls of the tube to collapse, but too low a pressure may not fully close over the edges of the tube. Too low a pressure, in some instances, may be sufficient to close over the edges of the tube but not sufficient to prevent the excess metal on the inwardly rolled corners from distorting backward in a direction opposite to that of the roller pass, causing the end of the rolled tube to be wider than its original dimension.
[0043] Because the roller is free to rotate on its axis, the pressure exerted by the roller on the tube will mainly be determined by the distance from the path of the roller pass to the end of the tube which will lie parallel to it. The pressure can thus be finely adjusted by altering this distance. In the example of the mild steel tube and roller depicted in Figures 14 and 13, a suitable distance between roller paths, when both ends are rolled simultaneously, has been found to exist where the unrolled tube length (L) is reduced by 5mm in length during rolling, as depicted in Figure 15. It has also been found that the lengths of batches of tubes to be rolled shculd be controlled within a tolerance of ± 0.1mm to ensure a good finish when rolled.
[0044] The method has been found successful for steel tubes of the dimensions shown in Figure 14. Tests have indicated that the method may also be used on tubes of various dimensions but that the ratio of the material thickness to the overall thickness of the flat tube should lie between about 0.1 to 0.2 (e.g. the tube shown in Figure 14 has a ratio of 1.5 : 11.0 = 0.136).
[0045] The method has also been found successful for tubes where the corners have been other than the simple semi-circle shown in Figure 14.
[0046] Where TIG welding is used to seal the element ends it may usefully be applied in either of the following ways:-
(a) Orienting the flat tube such that the seams to be welded are vertical, and then carrying the TIG weld from the top of the seam downwards to the bottom by vertical descent of the welding torch.
(b) Orienting the flat tube such that the seams to he welded are horizontal, and moving the torch horizontally from one end of the seam to the other.
[0047] The horizontal welding method has the advantage that the seam weld is less likely to be affected by gravity and will thus be neater and more even, whereas the vertical welding method may exhibit a slight bulging at the lower end of the weld. The horizontal welding method is particularly suitable for elements used in panel radiators, where the elements lie one against the other, and a small uneveness would be noticeable. Horizontal orientation of the flat tubes also facilitates provision of waterway apertures in the tubes in a production line or apparatus in which tube orientation is maintained, as these apertures will normally be punched or drilled on the flat faces of the flat tubes.
[0048] The vertical welding method may be found more convenient for column radiators, where the slight uneveness will be less noticeable and where the waterway apertures are provided on the curved part of the sidewalls of the tube.
[0049] Apparatus for preparing heat exchange elements suitable for a column radiator will now be described with reference to Figures 17 to 20.
[0050] Flat metal tubing is cut into lengths, in batches with a length tolerance of - O.lmm. One side of the apparatus shown in Figure 16a is movable to enable batches ot elements of different lengths to be made.
[0051] One of the tube lengths from the batch may be used as a direct measure for setting the width of the apparatus.
[0052] The cut tube lengths are introduced to the apparatus either by individual loading or by automatic feeding from a manually loaded stack of cut tubes. The tubes are automatically moved through the work stations of the apparatus, all of the tubes in the apparatus being advanced simultaneously one step at a time. This may be achieved by various known methods of multiple component transfer such as a conveying surface or by means of loading the tubes into holders mounted on a pair of parallel endless chains which run between the two halves of the apparatus.
[0053] The first work station 104 is an end rolling station, where the ends of the tube are closed over by rolling as described above. The tube is positioned and held by a fixed rest 105 underneath and a powered movable forked clamp 105a which descends on the tube from above. Both the upper and lower rollers, which are free to rotate, are mounted in a single carriage 103 which can slide in a vertical direction only and is powered down and up by means of either a hydraulic cylinder or a mechanical screw (not shown).
[0054] The second work station 106 is an aperture punching station. When preparing heat exchange elements for a column radiator, a single aperture is required, for fluid entry and exit, at each end of the curved part of the side wall of the tube. These apertures should be at least 5 mm in diameter. The tube is clamped similarly to the first work station 104. A bottom punch die is not used. An angled punch 107 is used to reduce the punching force. The slug is not fully punched from the tube hut is retained by a small tag and bent through ninety degrees into the tube, to prevent problems of loose slugs rattling in the heat exchange element at a later stage.
[0055] The flat tube is then carried to the third work station 108. In this work station the closed tube ends are sealed by TIG welding. Linear movement devices 109 automatically cause the TIG welding torches 110 to traverse the seams at the closed over ends of the tubes, thereby sealing the tubes. The tubes are clamped similarly to the first station 104. The time required to TIG weld one element end is many times greater than any of the other operations carried out in the apparatus being described. Thus where production capacity is important it will be found advantageous to equip the apparatus with more than one pair of TIG welders. The apparatus shown in the drawings has three pairs of TIG welders and these are all moved by single linear movement devices on each side of the apparatus. Welding occupies three workstation positions on the apparatus, and the automatic apparatus feeding cycle is arranged such that the welding process is carried out only on every third cycle of the apparatus, whereas the other processes are carried out on every cycle of the apparatus.
[0056] The heat exchanqe elements are then carried to the fourth workstation 111 where the area adjacent the fluid apertures is cleaned in preparation for subsequent resistance welding. Cleaning is carried out by means of a rotating wire brush 112 which descends onto the curved part of the sidewall of the element when the element is positioned in the work station.
[0058] Apparatus for preparing heat exchange elements suitable for a panel radiator will now be described with reference to Figures 21a and 21b.
[0059] The preparation of cut tube lengths and the setting of the distance between the two halves of the apparatus are similar to that described for the apparatus shown in Figures 16 to 20.
[0060] The cut tube lengths are fed from a manually loaded magazine 113 into the apparatus. The tubes are automatically moved through the workstations of the apparatus, one step at a time, and carried by some suitable means such as a conveying surface, or by an endless chain and supporting horizontal tracks for the tubes.
[0061] The first workstation 114 is an aperture punching station. In the case of a panel radiator, two apertures are provided on the flat faces at each end of the tube. These apertures should be at least 5mm in diameter. When punching is used, it is necessary to insert a bottom die into the tube to support it. This die is not shown in the drawings. The die is inserted and retracted automatically from the tube by the apparatus. Alternatively, the apertures can be drilled.
[0062] The second work station 115 is used only when the heat exchange element is to be subsequently resistance welded, in which case it is advantageous that the tube parts which support the fluid apertures, should project above the level of the tube material surrounding those tube parts.
[0064] Figures 23a,23b and 23c illustrate a forming tool set to carry out the operation. The Figures show an upper forming tool 116, a lower forming tool 117, a tube support block 118 and the tube end 119. The tube end 119 is supported underneath by support block 118. The lower forming tool 117 is inserted into the tube end 119, and has raised projections'underneath where the raised portions of the tube are desired. The upper forming tool 116, having complementary depressions corresponding to the raised projections of the lower forming tool 117, descends on the tube, with sufficient force to form projections on it by permanently deforming downwards the surrounding metal of the tube.
[0065] The projection forming work process may be carried out before or after formation of the fluid apertures, or, with special tooling may be carried out simultaneously. It may also be performed as a separate operation, distinct from the element making machine.
[0066] The third work station 120 is a tube end rolling station and is similar to that previously described with reference to Figures 16 to 20. However, because the tube is moved in the apparatus with its flat face horizontal, it cannot enter the throat of the rolling device as simply as in the previously described apparatus. Instead the tube is moved into the throat by an elevating device 121, which lowers the tube to its former position when rolling is completed.
[0067] The fourth work station 122 is the TIG weld end sealing station and is similar to that previously described with reference to Figures 16 to 20 except that the welding carriage moves horizontally instead of vertically along the tube seams.
[0068] At the final workstation 123 the area of tube adjacent the fluid apertures is cleaned by wire brushes. This station 123 is similar to that previously described with reference to Figures 16 to 20 except that the apertures lie on a different part of the tube.
[0069] Work stations 123 are only provided when the heat exchange element is to be subsequently resistance welded to headers.
[0070] Two pairs of wire brushing stations are provided in the apparatus illustrated in Figures 21a and 21b because each tube end has two fluid apertures.
[0072] Heat exchangers may sometimes include one or more dummy elements, that is elements through which no water flows and which are provided for purely aesthetic reasons. In making these dummy elements, the punching operation may be omitted from the method by rendering the punching station of the apparatus inoperative.
1. A method of manufacturing heat exchangers, the method comprising the following
steps:
holding two lengths of header piping in mutually parallel spaced apart relationship and feeding the header piping in steps through a work station;
locating a heat exchange element in contact with the header piping so that an aperture adjacent each end of the heat exchange element is aligned with an aperture in the contiguous length of header piping;
welding each end of the heat exchange element to the header piping to provide a mechanical joint and seal between the piping and the heat exchange element and so as to enable fluid communication between the interior of the piping and the heat exchange element; and
advancing the piping and connected heat exchange element beyond the connection work station.
2. A method according to Claim 1, in which the apertures in the header piping are
pre-formed and pre-cleaned to facilitate resistance welding of the heat exchange element
to each length of header piping.
3. A method according to any one of Claims 1 or 2, in which the header piping, to
which heat exchange elements have been connected, is cut into predetermined lengths
at a subsequent cutting station to form discrete radiator assemblies.
4. A method according to any one of the preceding claims, in which the header piping
which bends at the connection work station, during connection of a heat exchange element
to and between the header piping, is corrected, at the same or subsequent work station,
by deliberately induced contra bending.
5. A method according to any one of the preceding claims, in which baffles are inserted
into the header piping, between selected heat exchange elements, for routing the flow
of heat exchange fluid through the heat exchange elements, the baffles being preferably
of resiliently deformable non-perishable material such as silicone rubber, and each
baffle having a hole into which is inserted a tool having a length greater than the
length of the hole, the tool being used to push the baffle along the pipe to the desired
location.
6. Apparatus for manufacturing heat exchangers, the apparatus comprising
holding means for holding two lengths of header piping in mutually parallel spaced apart relationship and for feeding the header piping in steps through a work station;
locating means for positioning a heat exchange element relative to the header piping so that an aperture adjacent each end of the heat exchange element is aligned with an aperture in the contiguous length of header piping; and
welding means at the work station for welding each end of the heat exchange element to the continuous header piping to provide a mechanical joint and seal between the piping and the heat exchange element and so as to enable fluid communication between the interior of the lengths of piping through the heat.exchange element.
7. Heat exchangers made by a method or apparatus as claimed in any one of the preceding
claims.
8. A double heat exchanger comprising two heat exchangers each provided with a generally
semi-circular section header pipe, the two semi-circular header pipes being joined
back-to-back such that the two header pipes have a generally circular composite section,
the double heat exchanger being assembled from two heat exchangers as claimed in Claim
7 and being provided with a single circular fluid connection at each end of the joined
header pipes, providing fluid access and exits to each half of the joined header pipe.
9. A method of closing an open end of a flat metal tube having two mutually parallel
side walls joined by a pair of curved ends, the method comprising the use of a roller
having a shaped circumferential groove to fold inwardly the curved ends and then the
side walls of the open end of the tube while the roller is passed across the open
end of the tube from one end towards the other and pressed into engagement with the
tube so that the tube end is within the groove, two roller passes being made one after
the other and in opposite directions, one starting from beyond each corner.
10. A method according to Claim 9, in which the folded in end of the tube is sealed
by tungsten inert gas welding.
11. A method according to Claim 9 or Claim 10, in which the first roller pass extends
less than half the length of the end of the tube and the second roller pass extends
more than half the length and overlaps the first roller pass.
12. A method according to any one of Claims 9 to 11, in which the roller employed
has a profile such that a clearance is left between the cheek of the roller and the
side walls of the tube.
13. A method according to any one of Claims 9 to 12 in which a pair of rollers are
employed at the end of the tube, one to make each pass.
14. A method according to Claim 13, in which two pairs of rollers are employed, one
at each end of the tube, so that the tube may be sealed in an automatic or semi-automatic
fashion, the distance between the pairs of rollers being finely adjustable.
15. Apparatus for closing an open end of a flat metal tube having two mutually parallel
side walls joined by a pair of curved ends, the apparatus comprising a roller having
a shaped circumferential groove to fold inwardly the curved ends and then the side
walls of the open end of the tube while the roller is passed across the open end of
the tube from one end towards the other and pressed into engagement with the tube
so that the tube end is within the groove, and means for pressing the roller into
engagement with the end of the tube and for driving the roller along the end of the
tube.
16. A heat exchange element comprising a flat metal tube the ends of which have been
closed and/or sealed by the method according to Claim 10 or by the apparatus according
to Claim 15.
17. A method of forming apertures in the side wall at the end of a flat metal tube
comprising depressing the material of the tuhe surrounding that part of the tube in
which the apertures are to be formed, forming the apertures in the material surrounded
by the depressed material so that the part of the material remaining after the aperture
forming is raised relative to the surrounding material.