IMPROVEMENTS RELATING TO HEAT EXCHANGERS

Abstract: A heat exchanger such as a vehicle radiator comprises a pair of tube plates 11, 12 between which flat tubes 13 extend, interspersed with corrugated fins forming airways 14. Head­ er tanks are formed by attaching shells (not shown) to the tube plates. In production of the radiator, the tubes and airways are assembled, between clamping channels 17, as a separate item. To hold the matrix together, ties 16 hold the clamping channels together. The ties have end portions 17 which are bent laterally with respect to the axes of the ties, and which extend in different, preferably substantially opposite directions. Thus the ties can only be removed from the apertures in the channels by twisting the ties about their axes, and thus cannot jump out as a result of vibration.

Description: IMPROVEMENTS RELATING TO HEAT EXCHANGERS This invention relates to heat exchangers, and especially to vehicle heat exchangers such as vehicle radiators. One way of manufacturing such radiators is to assemble a matrix of tubes and airways between two clamping channels which are then clamped together by means of ties. Tube plates are then fitted onto the ends of the tubes. These tube plates form part of header tanks for the cooling fluid. The ties perform the dual function of holding the matrix together during manufacturing stages and also of resisting expansion of the radiator matrix under varying internal pressures in use of the radiator. Various means have been employed for attaching the ties to the clamping channels. For example, in one arrangement the ties are welded to the channels, but this involves jigging the matrix to ensure the correct spacing of the channels when the welding operation takes place. In another arrangement the tie is a rod with threaded ends which pass through the channels to be retained in place by nuts. This operation is labour intensive however and unduly costly. Again, it has been proposed to bend the ends of the tie through a right angle and insert them through apertures in the channels perpendicularly to the axis of the tie; it has been found however that under some circumstances the tie members can jump out of the apertures. The invention provides a heat exchanger which includes a matrix of tubes and airways located between two clamping members, at least one tie connecting the clamping members, wherein the said tie extends at each end through an aperture in a respective clamping member, and the end portions of the said tie extend laterally with respect to the length of the tie but in different directions such that insertion of the end portions of the tie through the apertures, and hence removal therefrom, requires resilient torsional deformation of the tie. This provides a simple method of holding the clamping members together which avoids the disadvantages mentioned, but one in which the ties cannot pop out. Normally at least two ties will be provided for each face of the matrix, and thus the tubes and airways will be located against movement perpendicular to the plane of the matrix as well as in the plane of the matrix. Advantageously, the end portions are so angled with respect to each other that the tie remains resiliently torsionlly deformed after insertion so that the end portions act as spring-clips holding the tie against the clamping members. Preferably, each end portion has a lead-in portion arranged at an angle to the remainder of the said portion, such that when one end portion has been pushed home during assembly of the heat exchanger, the extreme end of the other lead-in portion can be pushed into the respective aperture without any substantial torsional deformation of the tie. A heat exchanger which is a motor vehicle radiator, constructed in-accordance with the invention, will now be described by way of example with reference to the accompanyin 7 drawings, in which: Figure 1 is a front view of the radiator; Figure 2 is a section taken through the lines A-A in Figure 1; Figure 3 is an enlarged view of a tie looking along its length; and Figure 4 is an enlarged view, on the same scale as Figure 3, of an end of the tie. Referring to the drawings, the radiator is of the packed-construction type having a pair of tube plates 11 and 12 connected by a pluraiity of flat-section tubes 13 which extend through apertures in the tube plates to pass coolant from one header tank (defined by a tube plate and a header tank shell - not shown) to the other. Between the tubes 13 is located finning 14 comprising corrugated strips of metal, as is conventional. A pair of clamping channels 15 clamps the matrix together and the clamping channels are held together by means of a pair of ties on the frontface and another pair on the rear face. The matrix of tubes and airways is built up between the clamping channels during assembly of the radiator before the tubes plates 11 and 12 are fitted in position. The clamping members held by the ties hold the matrix together for subsequent assembly operations. In one of the subsequent operations, the tube plates 11 and 12 are added and in another the assembly is passed through an oven where the air-ways, which are soldercoated, bond to the tubes. The ties 16 also serve a function during subsequent use of the radiator since they resist expansion of the radiator in response to pressure pulses in the coolant. which would otherwise strain the soldered joints. It will be seen from Figure 3 that the end portions 17 of the tie rod are bent laterally with respect to the axis of the rod 20 but extend in different directions, actually more or less in opposite directions. It will thus be apparent from Figure 1 that the tie 16 cannot be simply pulled out of the apertures 18 in the channel 15 by a movement at right angles to the plane cf the matrix. In fact, ir order to withdraw the rod, it is necessary for it to be torsionally deformed or twisted about its axis. Referring to Figure 3, it is necessary for example for the right hand end portion 17 to be raised from a roughly horizontal to a roughly vertical position without moving the left hand end portion (since this will be pressed against the channel), in order for the right hand end poriton 17 to be withdrawn from its aperture. Accordingly, the tie is securely located in position and cannot jump out accidentally. In order to assist in insertion of the ties, each end portion 17 is bent at the elbow 19 to form a lead-in portion between the elbow and the tip of the end portion. The function of the lead-in portion is as follows. When one end of the tie has been passed through the aperture 18 in one channel 15, the portion of the end portion lying between the rod axis and the elbow is pointing upwardly and away from the other aperture. The lead-in portion points downwardly and towards that aperture. The operator thus has to slide the tie rod to align the tip of the lead-in portion with the aperture. For example, in Figure 1, if the left hand end of the tie is already inserted, the operator slides the right hand end upwardly as seen in Figure 1 from below the aperture 18 to insert the tip of the lead-in portion into the aperture. Thereafter, further upwards movement leads the end portion into the aperture, the axis of the rod twisting by virtue of this motion. The other end portion Bs forced hard against the channel. When the tie is fully inserted at both ends, it may be slightly torsionally deformed, i e both end portions resiliently abutting the sides of the channel members with the elbows 19, -or it may be non-deformed. In the former case, the tie tends to twist each channel member itself, but this is resisted by a cancelling force from the corresponding tie on the other face of the radiator. After assembly of the tie rods, the matrix is completed by addition of the tube plates and baked in an oven in the usual way0 Instead of employing two ties extending across each face of the radiator, the upper ties (as seen in Figure 1)- on each face may be replaced by one U-shaped tie which say extends from the left-hand channel (as seen in Figure 1) where it passes into an aperture and has the same shaped end portion as the tie 16, across the face of the matrix, has a U-bend around the right-hand channel, and extends back across the other face of the matrix, where it passes into an aperture in the left hand channel (but on the other side) via its shaped end portion. The end portions will be shaped the same as for the ties shown in the drawings except that both end portions may advantageously be directed in the same direction (when viewed along the axes of the Ushape), rather than in substantially opposite directions as shown in the drawings (Figure 3), in order that torsional deformation is needed to withdraw the end portions. However, it may be found satisfactory for the end portions to point in roughly opposite directions since the U-bend itself resists twisting of the tie.

Claims: CLAIMS 1. A heat exchanger which includes a matrix of tubes and airways located between two clamping members, at least one tie connecting the clamping members, wherein the said tie extends at each end through an aperture in a respective clamping member, and the end portions of the said tie extend laterally with respect to the length of the tie but in different directions such that insertion of the end portions of the tie through the apertures, and hence removal therefrom, requires resilient torsional deformation of the tie. 2. A heat exchanger as claimed in claim 1, wherein the end portions are so angled with respect to each other that the tie remains resiliently torsionally deformed arter insertion so that the end portions act as spring clips holding the tie against the clamping members. 3. A heat exchanger as claimed in claim 1 or claim 2, wherein each end portion has a lead-in portion arranged at an angle to the remainder of the said portion, such that when one end portion has been pushed home during assembly of the heat exchanger, the extreme end of the other lead-in portion can be pushed into the respective aperture without any substantial torsional deformation of the tie. 4. A heat exchanger as claimed in claim 3, wherein the lead-in portions are so angled that once one end has been inserted in an aperture, upon insertion of the extreme end of the respective lead-in portion into the other aperture, a torque is generated to deform the tie in torsion as a result of applying a linear force to the respective end portion of the tie. 5. A heat exchanger as claimed in any one of claims I to 4 wherein the entire length of the tie is formed from a single length of rod appropriately bent. 6. A heat exchanger substantially as hereinbefore described with reference to, and as shown in, the. accompanying drawings. 7. L method of producing a heat exchaa having a matrix of tubes and airways located between two clamping members, including the step of connecting the clamping members together by means of a tie, the tie being inserted at each end into an aperture in a respective clamping member, the end portions the the tie extending laterally with respect to the length of the tie but in different directions so that insertion of the tie requires resilient torsional deformation of the tie.

Inventors: LARDNER, GRAHAM GERALD
Applicants: SU BUTEC LTD
Application year: 1983
Main classification: F28F9
IPC codes: F28D1, F28F9