GB2146939A - Device for fixing heat-exchanger plates to their carrying pipes - Google Patents

Abstract

The device according to the invention fixes heat-exchanger fins (2) onto carrying pipes (1) without using any binding material in such a manner that the material of the flange of the heat-exchanger fin is fixed onto the carrying pipe by applying a proper pressure. The pressure to the flange is applied by means of a slit bush (3), whose external surface is cone-shaped and by means of a surrounding sleeve (4) whose internal surface is cone-shaped. The sleeve (4) is connected to a device for sliding the sleeve axially over the bush (3). Because of the conical shapes, the axial sliding of the sleeve (4) over the brush (3) causes the latter to constrict, thereby pressing the flange of fin (2) against the pipe (1). By applying properly selected compressive forces, the material of the flange is deformed on the carrying pipe (1), thereby establishing a bond between the flange and the pipe similar to a metallic bond. <IMAGE>

Description

SPECIFICATION Device for fixing heat-exchanger plates to their carrying pipes The invention relates to a device for fixing heat-exchanger plates to the carrying pipes.

It is well-known that in industry, agriculture and serving, lamella heat-exchangers have been used, in particular for cooling purposes. Essentially, lamella heat-exchangers consist of the pipes being suitable for delivering the heat carrier medium and the heat-exchanger plates stringed thereon. In order to ensure long-lasting function, a fixed connection is established between the carrying pipes and the heat-exchanged plate. When using steel pipes and heat-exchanger plates made of steel, said requirement is met by using zinc or tin, or by dipping into a tin bath. By using tin, corrosion protection of the structural elements is provided for, simultaneously fixing of the plates is also solved. In the case of thin-walled pipes, connection between the pipe-nest of the plates and the pipe is established by the mechanical expanding of the tube, e.g. by using balls.

In connection with production of heat-exchangers the interest of technicians is more and more directed to aluminium. By virtue of easy processing, good heat-conductivity, resistance to corrosion, etc aluminium is considered as an ideal material or making heat-exchanger plates.

Inspite of the advantageous features aluminium could not be used in a wide circle, as connection was problematic.

It is well known fact that the oxide layer coating the surface of aluminium prevents metallic interconnection with other materials. Removal of the oxide-layer and thus rendering aluminium suitable for metallic bonding is a most complicated and thus most expensive process. As a consequence, application in a wide sphere became impossible.

With other known solutions, bonds between the carrier pipes and the heat-exchanger plates made of aluminium is established with mechanical means. With thin-walled pipes of low strength, pipes are expanded by using the process previously mentioned. However, this process can be applied to a restricted extent only, i.e. in cases in which there is no additional load on the pipes beside the weight of the plates. With thick-walled pipes of highstrength - according to one of the known solutions - heat-exchanger plates are fixed by using distance rings. With this solution a heatexchanger plate is enclosed on both sides by the distance rings. These partly ensure the fixed state of the plates, partly they define mutual distance between the plates. With another solution, pipenests are formed so as to ensure distance-keeping, i.e. fixing of the pipes.This double function is achieved by giving a conical shape to the pipe-nest in such a manner than the pipe-nests of the heatexchanger plates, having been arranged on the carrier pipes, can be mutually interconnected to an extent allowed by the conicity.

The disadvantages of said solutions can be summarized, as follows: - For production the manual labour requirement is high; productional process can be hardly automatized.

- Both the distance rings and specially shaped pipe-nests hinder formation of optimal streaming conditions.

- In case of sub-zero treatments in the parts between the distance rings, as well as connection of the pipe-nests, ice is formed, resulting in detrimental stresses and shortened useful life of the heatexchanger.

- Possible extent of cold deformation of aluminium restricts special shaping of the pipe-nests.

As a consequence of said disadvantages - with a special respect to the quick propagation of the application of the heat-exchanger - there is a demand for a mode of connection which meets all the requirements regarding heat power engineering, useful life, i.e. productivity. The device according to the invention complies with all the three of them.

The invention is based on the recognition, in so far as by applying proper mechanical pressure on to the pipe-nests - by the suitable selection of parameters - a bond can be established, the quality of which is similar to that of a bond having been achieved by using a solder.

The pre-requisite for forming this bond lies in that strength properties of the pipe should considerably surpass the strength properties of the heatexchanger plates. In practice, parameters of these elements are to be chosen so that at the pressure at which the material of the pipe-nest suffers a permanent deformation - i.e. it yields - the pipe itself should remain within the limits of elastic deformation. If additionally it can be ensured that process of mechanical pressing could be inserted into the automatized manufacturing process of the heat-exchangers, all the three aims are fulfilled.

A special difficulty in solving the task in practice lies in that mechanical pressure is to be applied onto the pipe-nest in the shape of a ring, at the same time the used heat-exchanger comprise 4, 8, 16, etc. pipes. The pipes are arranged close to each other in several rows.

The aim set is achieved in accordance with the invention in such a manner that the pipe-nest of the heat-exchanger plate is surrounded by a split externally conical bush. When axial pressure is exerted onto the split externally conical bush by means of the sleeve with an internal cone, and simultaneously axial displacement is hindered, the segments of the split bush are radially displaced and exert a force effect onto the pipe-nest.

By proper dimensioning of the bush, the sleeve and push-force yield of the pipe-nest - due to the force exerted - can be achieved, and a mechanical bond with the carrying pipe can be produced. In case, if the equipment is coupled to a automatic machine producing a heat-exchanger, and the movements needed for exerting the ironing force performed by the segments of the split bush with the external cone, production can be fully automatized.

The invention will be described in details by means of a preferred embodiment serving as an example, by the aid of the drawing enclosed, wherein Figure 1 is showing a possible embodiment of the invention, Figure 2 is showing the most important elements in an enlarged scale, With the embodiment serving here as an example, the device is coupled to the stringing head of the automatic machine producing cooling blocks (described in the HU-PS 158,058) by means of the threaded pin 8. The device operates, as follows: Heat-exchanger plate 2 is strung onto the pipes 1 in the usual manner.

Prior to reaching place of fixation of the plate, hydraulic cylinder 14 is activated, the piston rod of which is pushing the press-plate 9 forward. The hydraulic cylinder is fixed by means of the carrier plate 16 to the pins 8. Oil-supply to the hydraulic cylinder is ensured by the duct 15.

Push-force is transmitted via the press-plate to the sleeve 4 with the internal cone, the number of which corresponds to the number of the carrying pipes.

The sleeve 4 with the internal cone, while moving as led by the bush 6, compresses the segments of the slit bush 3 with the external cone and being fixed to the stringing head 7 by means of the locking pins 5 in a radial direction. The compressed segments iron (press) and fix the cylindrical pipenest of the heat-exchanger plate onto the outer mantle of the pipe 1. Ironing process can be performed both while moving and in a stationary state. When the piston rod is returning to its starting position, the press-plate carries the sleeve 4 with the internal cone through the axle nut 12, as a consequence, the slit bush 3 with the external cone is relieved from pressure and regains its original shape. When the stringing head is starting back to perform the next stringing procedure, it carries the plate-fixing device with it.

In case of a heat-exchanger consisting of several carrying pipes, due to the difference in size (within the field of tolerance) of the pipes having theoreti cally identical diameters, forces of different extents would be exerted onto the single pipe-nests, as compression of segments would be controlled by the largest diameter. In such a manner it could happen that due to the considerable differences between the pipe diameters the pipe-nest of the plate of the pipe with the smallest diameter would not be compressed to the desired extent. To avoid this, it has to be ensured that in dependence of the pipe diameter the sleeves with the internal cone could cover different distances. The elastic ring 11 arranged before the press-plate 9 is serving just for this purpose.

Between the elastic ring and the sleeve with the internal cone there is the underplate 10 to be found.

In case, if due to the larger pipe diameter ironing is finished on some of the pipes, i.e. the sleeve 4 with the internal cone is unable to move forward, push-force is taken up by the deformation of the elastic ring 11. In such a manner the hydraulic cylinder will be able to push forward the press-plate, as a result ironing procedure can take place on the other pipes too.

After having finished ironing procedure, a displacement-free bond will be available.

Due to differences in pipe diameter, i.e. unevenness of the pipes it may happen that press-plates 9 is leaving the theoretical plane. Detrimental force effects arising in this case may be eliminated by bedding the guide axis in a ball-seat 13.

Advantages of the device according to the invention can be summarized, as follows: - By using mechanical means a bond can be formed which meets all requirements relating to strength and heat power engineering.

- Neither heat-exchanger plates with specially shaped pipe-nests nor auxiliary means (distance rings) are required, which are leading to problems in respect to production, heat stream and durability.

- The fixing procedure according to the invention can be easily incorporated into the automatized manufacturing process, accordingly, switch-over to aluminium does not decrease productivity.

The device according to the invention is not at all restricted to the use of heat-exchanger plates made of aluminium, it is well suitable for ironing plates made of any other metal.

So e.g. it can be suitably used in production of heat-exchanger-plates made of copper, presently with these plates fixation to the pipes is performed by expanding the pipes.

It goes without saying that the device according to the invention can be applied in several ways not only in connection with the automatic machine for producing cooling blocks. Since by its use perfect bond can be established even if the diameter of the pipe-nest surpasses to such an extent the diameter of the carrying pipes that easy manual stringing becomes possible, the device can be well used on basis of manual stringing.

This type of application is sensible only with special heat-exchangers or when producing small series.

Claims (12)

1. Device for fixing heat-exchanger plates to the carrying pipes, characterised in that it consists of slit bushes with external cone, the number of which corresponds to the pipe-nests of the heatexchanger plates, of the forming sleeves with the internal cone connected to said bushes, of the press-plate and the force-transmitting means.

2. Device as claimed in claim 1, characterised in that between the press-plate and the sleeve with the internal cone an elastic element is arranged.

3. Device is claimed in claim 1 or 2, characterised in that the press-plate is embedded in a ballseat.

4. A device for securing fins onto a pipe in the manufacture of heat exchangers, which fins have an aperture through which the pipes extend and a flange around the aperture for engaging the pipe, which device comprises a split bush, the inner surface of which is capable of engaging the flange around a fin aperture, a sleeve having an inner surface mating with the external surface of the bush and being axially movable with respect to the bush, wherein at least one of the mating surfaces of the bush and sleeve is frusto-conical in shape, the device also including means for sliding the sleeve with respect to the bush to urge the bush radially against a flange and weld the latter onto a pipe.

5. A device as claimed in claim 4, wherein the means for sliding the sleeve bears on the sleeve by way of a resilient element.

6. A device as claimed in claim 4 or claim 5, which includes a plurality of split bushes and corresponding sleeves, and a single means for sliding the sleeves relative to their respective bushes.

7. A device as claimed in any one of claims 4 to 6, wherein the means for sliding the or each sleeve relative to its respective bush comprises a plate.

8. A device as claimed in claim 7, wherein the plate is articulately mounted on a moving device.

9. A device as claimed in claim 8, wherein the articulate coupling between the plate and the moving device is a ball-and-socket joint.

10. A method of securing a fin onto a pipe in the manufacture of heat exchangers, which fin has an aperture through which the pipe passes and a flange around the aperture for engaging the pipe to secure the fin in place, which method comprises so constricting the flange around a substantial part of its circumference that the flange is urged against the pipe and welded thereto, the pipe having a sufficient wall thickness to withstand the constriction forces.

11. A device for securing fins onto a pipe, substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

12. A method substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.