Abstract:
Tube ends are engaged in passage openings of tube plates and protrude above collars surrounding said passage openings. The larger sides of the tube ends are folded back and rolled about said collars. Part of the tube walls under said passage openings is enlarged.

Description:
This is a continuation of application Ser. No. 354,468, filed Apr. 25, 1973. 
    
    
     BACKGROUND OF THE INVENTION 
     Upon manufacturing heat exchangers having tubes engaged into tube-plates, it is of usual practice to proceed to an expanding operation of the ends of the tubes consisting in engaging a punch into the duct delimited by each tube to press the outer wall of said tubes against collars which usually flange passages for the tubes in each tube plate. 
     Said operation results in opening the mouth of the tubes to facilitate welding or brazing of the tubes with the collars of the tubes plates, but it does not ensure a strong mechanical connection between the tubes and the tube plates as long as the heat exchanger is not yet welded or brazed. It then occurs frequently during the handling operations of the heat exchanger that the tubes plates are moved from the ideal position they are supposed finally to occupy in the finished heat exchanger. Moreover, when the apparatus is completed, i.e. after welding or brazing is completed all the mechanical stresses applied between the tubes and the tube plates are supported only by the welds. 
     SUMMARY OF THE INVENTION 
     The present invention ensures a mechanical setting of the various tubes in the two tube plates so that the distance between the tube plates remains constant during all the handling operations taking place before the welding step and thus avoiding any risk of a displacement of the tube plates. Besides, when welding of the tube plates on the tubes is performed, said welding is made in far better conditions and the connection is far stronger than in previous methods. 
     The invention particularly relates to a tube and tube-plate assembly comprising a tube plate provided with protruding rims having a substantially rectangular configuration and defining tube passages, tubes respectively having one end inserted through each of said passages and protruding beyond said rim, said tubes having long and short sides defining substantially a rectangle of the same configuration as said rims to bear against the inner walls thereof, and said long sides of said tube ends being folded and rounded in a substantially semi-circular portion toward said tube plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a top view of a heat exchanger tube plate and tube assembly according to the invention; 
     FIG. 2 is a cross sectional view taken along line II--II of FIG. 1; 
     FIG. 3 is a transverse cross-sectional view taken along line III--III of FIG. 1, and 
     FIG. 4 is a cross-sectional view similar to that of FIG. 3 and illustrating a modification of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawing, a tube plate 1 of a heat exchanger, for example a cooling radiator is shaped to delimit tube passages flanged with collars 2. The ends of tubes 3 are engaged into the space delimited by the collars 2, said tubes having, as shown in the drawing, substantially a rectangular cross-section to closely correspond to the shape of the inner walls of collars 2. When the tubes are thus engaged, the portions 3a thereof protruding from the collars is expanded by a tool driven into each tube end. The long sides of each tube are outwardly folded over, then rolled around corresponding portions of the collars 2 to form curled flanges 3b. A tool 4 for performing said operation can be constituted as represented diagrammatically in phantom lines under the form of a V-shaped body extended by rounded wings in FIG. 3. 
     Because of the Y-shaped form of its body, the tool 4, when causing the above described expansion and rolling, necessarily applies a pressure on part of the tube causing its expansion beneath the tube plate 1, to form a bulge 3c. Consequently, the collar 2 flanging the passage of each tube 3 is thus clamped between the rolled edges 3b of the large sides of the tubes and bulges 3c, thus ensuring a strong mechanical connection between the tubes and the tube plates facilitating thereby handling of the tube and tube-plate assembly. 
     When, afterwards, the heat exchanger is welded or brazed, the joining alloy, when melting, tends to be attracted through capillary action into the housings delimited between the walls of the respective collars and tubes and the melting alloy is particularly retained by the rolled portions 3b. The finished connection between the tubes and the tube plates is thus particularly satisfactory. 
     As shown in FIG. 3, upon rolling the portions 3b, it frequently occurs that the mouth of the tubes is slightly narrowed as shown in 3d. Rolling the portions 3b causes a stress in the metal of the tube thus tending to bring nearer the walls of its large sides. 
     FIG. 4 shows a development in which said disadvantage can be avoided. For that purpose a tool 5 can, for example, be provided with an angle portion 5a on its two sides. When the tool enters the tube end, the portions 3e of its longer sides are thus cambered to form at the level of the top of the collars 2 a fold with a sharp angle 3f. Then the tool 5 continuing its downward move causes, as previously, the rolling of the tube ends, said second operation being performed from the angle 3f which, of course, increases the inertia moment of the tube and consequently prevents formation of the narrowing 3d  FIG. 3. The rim 3c is also formed as represented, thus the mechanical connection of the tubes with the tube plates is still improved by comparison with the embodiment as shown in FIG. 3 which is not provided with the angled part 3f. The measure of which the rolling of the portions 3b is made can be provided to let - on a short distance - the rolled portion 3b to come in contact with the top of the tube plate as represented in 3b 1  in FIG. 2. 
     The present invention is not restricted to the embodiment shown and described in detail, for various modifications thereof can moreover be applied to it without departing from its scope as defined by the appended claims.