Metal working – Method of mechanical manufacture – Heat exchanger or boiler making
Reexamination Certificate
1997-03-27
2001-07-24
Leo, Leonard (Department: 3743)
Metal working
Method of mechanical manufacture
Heat exchanger or boiler making
C029S890054, C165S173000, C165S178000, C285S222000
Reexamination Certificate
active
06263570
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a heat exchanger, in particular a water or air radiator for a vehicle, and the like. More particularly, the invention also relates to a method of producing the same.
PRIOR ART
A common area of application for heat exchangers is cooling of circulating liquids in motor vehicles and machine tools, e.g. the liquid which cools the engine block. Heat exchangers are also used, for example, for cooling the intake air which is to be combusted in the engine of the vehicle.
A vehicle radiator is known through Swedish patent 9202819. The radiator is made of aluminum and has a heat-exchanger assembly which consists of surface-enlarging means and two rows of flat liquid-conveying tubes which are arranged flat side to flat side in the respective row. The surface-enlarging means are arranged between each pair of tubes in the respective row and are intended to guide an air flow through the heat-exchanger assembly in the transverse direction of the tube rows. The radiator also has an inlet tank, which is connected to a first end of the heat-exchanger assembly, and an outlet tank which is connected to the second end of the heat-exchanger assembly. The inlet tank and the outlet tank have a connection plate which is provided with a number of holes and which has, at each hole, a connecting sleeve element projecting from the tank. Each tube end has a widened portion which is accommodated on a connecting sleeve element and the inside of which is applied against the outside of the connecting sleeve element. When the tubes are mounted on the respective connection plate, the widened tube portions are thus guided over the connecting sleeve elements of the plate. The tubes are then connected to the connection plate by brazing. For brazing, external fixtures are required, for reasons which are explained below.
The production takes place by the parts, which have an external solder layer, being assembled, fixed to one another and subsequently placed in a furnace with a protective gas atmosphere or in a vacuum furnace. The soldering takes place by the external material layer on each component melting and forming solder material. This brazing is preferably carried out in one stage, that is to say the heat exchanger is assembled and soldered together subsequently in the furnace.
The soldering process requires the parts to be applied properly against one another and to be fixed in position. Since the parts of the heat exchanger are loose in relation to one another before the soldering process, use is today made of external fixtures. These are expensive, however, and moreover conduct heat away from those parts which are to be soldered together. Furthermore, it is a time-consuming process to fix the parts of the heat exchanger with great accuracy using external fixtures, which makes the production more expensive.
In the production of radiators of the above type, it has emerged that, in spite of the use of external fixtures, a large number of radiators leak, after brazing, at the joints between the tubes and the connecting sleeve elements, as a result of which up to approximately 20% of radiators have had to be rejected, since the leakage detected cannot be repaired manually after brazing.
Furthermore, the connecting sleeve elements can cause turbulence and retard liquid flow through the tubes.
The prior art also includes EP-B-0 457 978 which discloses a heat exchanger with connection plates and flat liquid-conveying tubes.
OBJECTS OF THE INVENTION
A general object of the present invention is to completely or at least essentially overcome the problems of the prior art described above. More specifically, one object of the invention is to produce a heat exchanger with a low rejection rate in production.
One particular object of the invention is to produce a heat exchanger which can be soldered together without the need for external fixtures.
Another object is to produce a heat exchanger which can be assembled for soldering in one stage in a rapid, simple, very accurate manner with low requirements on the tolerances of the individual parts.
A further object of the invention is to produce a heat exchanger which allows manual repair of leaking joints after it has been soldered together.
It is likewise an object to produce a heat exchanger having reduced risk of generating turbulence in the transition between tube and tank.
It is also an object of the invention to indicate a production method which solves the abovementioned problems.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a heat exchanger for vehicles, comprising a heat-exchanger assembly, which includes at least one row of spaced-apart flat liquid-conveying tubes as well as surface-enlarging means arranged between the tubes in the respective rows. An inlet tank is connected to a first end of the heat-exchanger assembly, and an outlet tank connected to a second end of the heat-exchanger assembly. The inlet and the outlet tanks have having a connection plate, which is formed with a number of connection holes for the tubes and which, at each hole, is provided with a connecting sleeve element projecting from the tank. Each tube has at its ends, a widened main portion accommodated on the connecting sleeve element. A rounded transitional area is provided between the connection plate and the respective connecting sleeve elements. The main portion is inserted in the connecting sleeve element with its outside, circumferentially applied against the inside of the element. Each tube at its ends has an end portion which is widened in relation to the main portion and which merges with the main portion and is applied against the transitional area.
According to a further aspect of the invention there is provided a method of connecting flat liquid-conveying tubes to a connection plate in the production of a heat exchanger. A plurality of holes are formed in the connection plate and are deformed in such a manner that tube-accommodating connecting sleeve elements are formed on the one flat side of the plate. One end area of each tube is, in a first step of deformation, deformed in such a manner as to obtain a shape corresponding to that of the connecting sleeve element, thereby increasing the cross-sectional area of the end area. The end area is, in the first step of deformation, given smaller dimensions than the connecting sleeve element. The widened end areas of the tubes are, from the one flat side, inserted in the connecting sleeve elements until the end surfaces of the tubes are located essentially on a level with the holes of the plate. The widened end areas of the tubes are, in a second step of deformation, further widened from the other flat side of the plate in such a manner that the respective tube ends are applied against a transitional area located between the plate and the respective connecting sleeve elements.
The method according to the invention reduces the risk of leakage in the heat exchanger produced, as a solder layer is applied to a solder layer in the joints between the connecting sleeve elements and the tubes. As a result, the quantity of solder material which is available during brazing is increased.
Moreover, during assembly of the heat exchanger, relatively large tolerances of the individual parts, such as the tubes and the connection plates, are allowed as the concluding, second deformation step evens out mutual size variations.
Mounting of a tube on the connection plate is facilitated also by the widened main portion of the tube being inserted into the connecting sleeve element and thus being guided against the inside thereof.
The parts included in the heat-exchanger assembly are interconnected due to the concluding, second deformation step, and external fixtures can therefore be dispensed with.
The joints between the tubes and the connection plate are accessible from the flat side of the plate facing away from the tubes. In the event that, after brazing, it emerges that one or more joints are not sufficiently tight, these can consequently be repaired by manual
Leo Leonard
Morgan & Finnegan , LLP
Valeo Engine Cooling Aktiebolag
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