Tube end plate for heat exchanger with tubes and water boxes
BACKGROUND OF THE INVENTION 
     The present invention relates to a new type of tube end plates for heat exchanger of the tube and heat dissipator type, such as cooling radiators for vehicle engines. The invention applies more particularly to radiators for heavy duty trucks; due to their large size, the heat expansions reach a particularly great amplitude. However a strong connection is provided between the water boxes and side flanges, in order to form a rigid frame which therefore does not permit heat expansions, such a strong connection being provided for improving the mechanical resistance of such heavy duty heat exchangers subjected in operation to severe conditions and for which there is required a particularly long life time. 
     Within the scope of the invention, there is also proposed to obtain a tube end plate which can be used for providing heat exchangers with several passes, i.e. in which the liquid to be cooled flows in a same direction or on the contrary along one or several hair-pin bends. 
     SUMMARY OF THE INVENTION 
     The tube end plate for heat exchanger according to the invention has on a peripheral groove cooperating with lower portion of the water box forming a hollow beam and to which it is connected by means known in the heat exchanger art and providing a longitudinal rigidity of the tube end plate in a complementary manner to that provided by the hollow beam-shaped water box. A bottom portion of the tube end plate is provided with tube passages having collars to which the tubes are brazed and between which are formed transverse slots extending transversely up to an inner wall defining the peripheral groove and by which the tube end plates can accommodate differential heat expansions generating detrimental stresses which should not appear in the brazed seals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various features of the invention will become more apparent from the following description with reference to the accompanying drawings of an embodiment consisting, in a non limitating manner, of a tube end plate for a heat exchanger crimped onto a water box via a flexible gasket; in the drawings: 
     FIG. 1 is a partial sectional view of a heat exchanger comprising a tube end plate according to the invention; 
     FIG. 2 is a partial perspective view showing the inside of the tube end plate; 
     FIG. 3 is a partial plan view, as seen from above of the tube end plate; 
     FIG. 4 is a superposition of sectional views taken along lines IV, IVa and IVb of FIG. 3; 
     FIG. 5 is a partial perspective view of the tube end plate cut along line IVb of FIG. 3 and provided with a sealing gasket. 
     FIG. 6 is a partial sectional view also seen along line IVb of FIG. 3 and showing aspect of the gasket when a water box is in position on the tube end plate; 
     FIG. 7 is a partial sectional view of the gasket shown in FIG. 6 when the gasket is not compressed. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows in part a heat exchanger comprising circulation tubes 1, a tube end plate 2 and a water box 3 covering the tube end plate 2. The tube end plate 2 is shaped in a known manner for defining at its periphery a groove 4 receiving a deformable gasket 5, for example made of an elastomer. The gasket 5 is squeezed in the bottom of the groove 4 by a lower edge 6 of the water box 3, said edge being formed on its top portion with a heel 7 onto which is folded a clamp 8. 
     The tube end plate 2 is configurated, for example stamped, so as to have collars 9 in one or several rows, the collars each defining a tube passage 10 in which the end of a tube 1 is provided to be engaged. 
     As shown in the drawings, slots 11 are formed transversely in the tube end plate between each collar 9 or row of collars. 
     As shown in the drawings, in the perspective view of FIG. 2 and in that of the sectional views of FIG. 4 which is taken along line IV of FIG. 3, the slots are formed up to the inner wall defining the groove 4 and terminate in a rounded portion 11a. The drawings show also that the slots 11 have their concavity turned toward the inside of the tube end plate, i.e. toward the water box 3. 
     Depth of the slots 11 is chosen to be preferably greater than thickness e of the tube end plate, but less than double of the thickness e. The hereabove slots 11 form so to speak an embossing between each tube 1 or row of tubes, thereby providing the tube end plate with a flexibility making possible a deformation between the tubes 1 or rows of consecutive tubes while providing on the other hand a rigidification of the tube end plate adjacent its portion defining the shaped groove 4. Thus, the portion of the tube end plate 2 defining the collars 9 can be subjected to deformations of small amplitude due to differential heat expansions between the tubes without these deformations being transmitted to the portion defining the groove 4 which, on the contrary, is made rigid by the rounded end of the slots. Thus, the groove 4 is formed in a rigid frame such that the gasket 5 can be kept under a uniform pressure by the clamp 8, whatever are the operating conditions of the heat exchanger. 
     As shown in the drawings, it is advantageous that at least one of the slots, such as that shown at 11 1 , be formed so as to open on a wall portion 4a of the groove 4 which is not provided with the rounded portion 11a but has on the contrary a steeper inclination, for example of 60° with respect to horizontal. The slot 11 1  is provided, in the embodiment shown, for housing a wall gasket 5a (FIGS. 5, 6 and 7) for providing tightness between a wall 12 formed inwardly by the water box 3 and the tube end plate 2 when the heat exchanger is of the several pass type. More generally, the slot 11 cooperates with a wall separating two compartments of the water box. 
     As shown in FIG. 7, it is advantageous that the wall gasket 5a is formed integrally with the gasket 5 and has a swelling portion 5b (FIG. 7) corresponding to the slanting edge 4a which is prolongating the slot 11 1  on each side thereof. 
     The effect of such a configuration is that the underneath portion 6 of the water box strongly deforms the gasket at the swelling portion 5b and thereby applies it very closely against the lower portion of the water box as well as against the bottom of the slot 11 1  and against the slanting wall 4a.