Heat exchanger comprising a core of tubes engaged inside end plates mechanically connected with header boxes

The heat exchanger comprises a core of tubes engaged into tubes plates defining a peripheral groove bounded outwardly by a raised edge with a sealing gasket being placed in the bottom of the groove in order to be clamped by under side of an edge of a header box maintained by gripping means. The header box is thin walled and the edge of said header box has a top portion with a small bar interposed between said top portion and said gripping means.

BACKGROUND OF THE INVENTION 
The present invention relates to heat exchangers comprising a core of tubes 
engaged inside end plates which are adapted for being covered by header 
boxes assembled so as to be dismountable, viz. fixed on the periphery of 
each tube plate with interposition of a deformable joint. 
DISCLOSURE OF THE PRIOR ART 
Hitherto, in this type of heat exchangers, the header boxes are made in a 
moldered synthetic material so that they present, on their lower portion, 
a heel or edge which is thick and protruding, and on which are crimped 
lugs or protrusions formed either by the tube plate itself or by an added 
clip. 
However, it was not possible to use the same technique with metallic header 
boxes since such boxes have necessarily thin walls and, consequently, it 
is not possible to economically form a thick heel permitting an efficient 
crimping operation. 
In an attempt to solve this problem, British Pat. No. 699,032 has disclosed 
embodiments in which the peripheral edge of the header box is crimped on a 
flexible gasket by forming a hollow rib which is adapted for increasing 
the rigidity of the crimped edge. This apparently satisfactory disposition 
needs the use of a complex tooling in order to form the hollow rib inside 
which is placed the flexible gasket. 
Applicant has already described in French Pat. No. 74-16284 an embodiment 
in which the peripheral edge of the header box has a rounded form for 
increasing its rigidity and, in this case, the edge of the end plate is 
crimped on the raised end of the peripheral edge of the header box. 
Difficulties have become apparent in practice since the crimping devices 
used for the lugs of the tube plate inside the curved portion of the 
peripheral edge of the header box often cause a deformation of the 
peripheral edge, and, consequently, warp the portion of the peripheral 
edge which normally bears on the flexible gasket. 
SUMMARY OF THE INVENTION 
According to the invention, the heat exchanger comprising a core of tubes 
engaged into tube plates defining a peripheral groove bounded outwardly by 
a raised edge with a sealing gasket being placed in bottom of the groove 
in order to be clamped by under side of an edge of a header maintained by 
gripping means taken among crimping portions extending the raised edge of 
the tube plates and an added clip, is characterized in that the header box 
is thin walled and in that the edge of such header box has a top portion 
with a small bar interposed between said top portion and said gripping 
means. 
Various other features of the invention will become more apparent from the 
detailed following description.

DESCRIPTION OF THE INVENTION 
In the drawings, reference numeral 1 designates the circulation tubes of a 
heat exchanger, particularly a cooling exchanger of the type of those used 
in motor vehicles. The tubes 1 are connected together in the usual manner 
by secondary heat exchange elements 2, made for instance of corrugated 
bands or fins. 
The ends of the tubes 1 are engaged in tube plates 3 which are formed, on 
their periphery, with a groove 4 and an outer raised edge 5. The tube 
plates 3 of the heat exchanger are made of a metal or an alloy compatible 
with the metal or alloy of the tubes 1 and of the elements 2, and these 
parts are assembled into a unit by brazing of by any other suitable 
method. 
According to the invention, there is used for covering the tube plates 3 a 
thin walled header box 6, advantageously made of metal, and typically by 
stamping a sheet of metal. Although not shown, the header box comprises in 
a known manner pipes, bases and other ducts which are usual in the art. 
In FIG. 1, the header box is formed at its base with a peripheral edge 7 
the width of which corresponds to that of the groove 4 of the tube plate 
3, and the edge 7 is extended by a raised edge 8, particularly for 
rigidifying said raised edge 8. 
For positioning the header box 6 and providing tightness with the tube 
plate, there is proceeded as follows: 
First of all, a deformable sealing gasket 9 is placed in the bottom of the 
groove 4, then the header box 6 is placed on said gasket. A following 
operation consists in positioning, between the raised edge 8 and the 
peripheral wall of the header box 6, a small bar 10 which may be made of 
various materials but which must be, preferably, rigid and not or little 
deformable, taking in account the efforts it has to withstand. Synthetic 
resins of the polyamide type may be used for making the small bar which 
could, also, be made of metal. 
It is advantageous, as shown in the drawings, that the small bar 10 forms a 
shoulder 11 covering the top portion of the raised edge 8 of the box. 
The following operation consists in positioning gripping means constituting 
a clip 12, well known as such, encasing the bottom of the portion of the 
tube plate which forms the groove 4 and which extends along the raised 
edge 5, and the lugs 13 of which are crimped on the top of the small bar 
10. 
It is advantageous that the small bar extends on the four sides of the tube 
plate. Moreover, the top 10a of the small bar is preferably situated above 
the edge of the tube plate so that the fold 13a of the lugs does not 
generate a fatigue line. 
Since the tube plates are most usually of a uniform width, it is 
advantageous, as shown in FIG. 3, to make the small bars 10 by a molding 
technique; the bars having the shape of a rectangular frame the dimensions 
of which correspond to those of the largest tube plate able to be used, 
and said small bars in the shape of a rectangular frame are then cut to 
lengths, as shown for example by the cutting lines 14 in FIG. 3. Of course 
it is possible, in case of need, to form small bars in the shape of 
rectangular frames for each type of heat exchanger, and it would not be 
departed from the scope of the invention by manufacturing half-frames the 
sides of which would then be cut to lengths, or by using lengths of small 
bars which would be placed in the four sides of the groove of each tube 
plate. 
FIG. 2 illustrates a slight alternative embodiment according which the clip 
12 is not used. In this case, it is the raised edge 5 of the tube plate 
which is provided with lugs 13, crimped on the top of the small bar 10 to 
constitute a gripping means. In this embodiment, the edge 10b at least of 
the small bar is rounded so that the fold of the lugs 13 is made in good 
conditions. 
FIG. 4 illustrates a simplified embodiment according which the header box 6 
has no raised edge 8, as in the previous embodiments, but is only 
surrounded by a plane edge 7a. In this case, there is, as previously, 
positioned on the top portion of the edge a small bar 10a the width of 
which corresponds to that of the edge 7a, and the lugs 13a of the tube 
plate 3 are crimped as shown in FIG. 2 on the top portion of the small bar 
to act as a gripping means. 
In this embodiment, the clip 12 of FIG. 1 could be used in the same way. 
FIGS. 5 and 6 show a development of the invention which is practiced in the 
embodiment hereabove described with reference to FIG. 2 but which, 
obviously, is applicable to the other embodiments. According to this 
development, curved-bottom notches, for example notches of a concave 
shape, are formed in the small bars and the lugs 13 are folded over in the 
notches and deformed so as to mate the shape of the bottom of said 
notches, which increases considerably the stiffness of the lugs. 
In all cases, the small bar which is made of a hard material withstands the 
efforts due to the crimping operation and distributes the efforts on the 
edge 7 or 7a of the header box, said edge being thus applied under a 
uniform pressure on the sealing gasket 9. 
The invention is not restricted to the embodiments shown and described in 
detail, and various modifications may be carried out without departing 
from the scope of the invention as shown by the appending claims. 
Particularly, the header boxes can be made of a synthetic material while 
having a thin wall normally deformable under the influence of the force 
usually applied by the lugs 13 if the small bars 10 were not used. It is 
thus possible to manufacture header boxes at costs lower than those 
entailed by boxes made of a molded synthetic material the thickness of 
which has to prevent any deformation of the part which is applied on the 
gasket 9 by the lugs 13.