Method and apparatus for making a water-tight radiator element
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to heating appliances, especially radiators, and more particularly to a method and apparatus for making a water-tight radiator element of the type produced from a flat tube having open ends which are closed and welded. 
     2. Description of the Related Art 
     In prior art methods of making such radiator elements, the open ends of the flat tube are closed by means of sealing covers which are inserted in the respective tube ends and welded to the sidewalls of the tube. In other such elements, a filler part is inserted in the flat tube near each open end and likewise welded or soldered to the sidewalls. 
     A radiator having flat elements disposed parallel to one another is described in U.K. Patent Application No. 2,094,966 A. Support parts forming the closure walls of the flat elements are inserted in the open ends of the latter and welded to the sidewalls. 
     None of these prior art methods yields a clean and symmetrically shaped radiator element. Moreover, the welding seams must be ground smooth when a sealing cover is inserted as well as when a filler or support part is introduced into the flat tube. 
     French Pat. No. 2,475,708 describes a radiator having flat elements disposed parallel to one another, the ends of which are sealed by bending the edge portions of the opposing wide side surfaces of the flat tube toward the middle of the ends and then welding them to one another. Sealing is not accomplished by means of rollers, however. Here, too, the surface of the bent edge portions with the welding seam is not cleanly formed. 
     In another prior art radiator element of this type, the open ends of the flat tube are closed by means of rollers and a support mandrel, whereupon the closed element is welded. One drawback of this method is that because of the opening for the mandrel, the element is not completely closed and is therefore not suitable for further processing by means of pressing and welding. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an improved method and apparatus whereby a water-tight radiator element having a clean and symmetrically shaped surface may be produced. 
     A further object of this invention is to provide such a method and apparatus whereby production costs are kept low. 
     To this end, in the method according to the present invention, the sealing of each end of the flat tube takes place by rolling edge portions of the wide, opposing sidewalls of the flat tube together by means of at least one flanging roll guided successively from the two sides over the edge portions toward the middle of the ends, after which the edge portions rolled closed are welded to one another in a semi- or fully-automatic tungsten inert gas process. 
     The flanging roll preferably makes two passes, one longer than the other, the two passes partially overlapping. 
     The apparatus according to the invention, for carrying out the above method, accommodates in a single unit a device for rolling the edge portions closed and a device connected thereto for welding the rolled-closed edge portions of the wide, opposing sidewalls of the flat tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a top of a flat tube with open ends, used for making a radiator element, 
     FIG. 2 is a diagrammatic top plan view of one of the open ends of the flat tube of FIG. 1 together with two flanging rolls which are guided over the edge portions of the wide, opposing sidewalls of the flat tube, 
     FIG. 3 is a diagrammatic side elevation of the aforementioned open tube end with edge portions rolled closed by one of the flanging rolls, 
     FIG. 4 is a partial side elevation of the finished radiator element, and 
     FIG. 5 is a diagrammatic top plan view of apparatus having various devices for producing the finished radiator element. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A flat tube 1 having open ends 2, 3 as shown in FIG. 1 is used for making a water-tight radiator element. The walls of such a tube 1 are about 1.25 to 2 mm thick. Tube 1 has wide, opposing sidewalls 1a, 1b (FIG. 3) and is first cut to the desired length. 
     As may be seen from FIGS. 2 to 4, tube 1 is closed at its ends 2, 3 and welded. Closing of each flat-tube end 2, 3 takes place by rolling edge portions of sidewalls 1a, 1b together by means of two flanging rolls 4, 5. These rolls are successively guided in opposite directions over the edge portions of sidewalls 1a, 1b, each from one side of tube 1 toward the middle of each end 2, 3. The first flanging roll 4 travels over a longer path x when making its pass than does roll 5. In order to obtain a clean, symmetrically shaped element, tube 1 must be overlappingly deformed by rolling from both sides at ends 2, 3, i.e., the rolling distances x, y of first and second flanging rolls 4, 5 must partially overlap. 
     After the edge portions of sidewalls 1a, 1b have been rolled together, these closed edge portions are welded to one another in a semi-automatic or fully-automatic tungsten inert gas (TIG) process. The element closed by rolling is well suited for this pressure-welding process, both steps being carried out in the apparatus to be described below. After welding by means of the semi- or fully-automatic TIG process, there is no need for any subsequent smoothing. The finished radiator element is cleanly shaped and water-tight. 
     FIG. 5 illustrates apparatus in which the above-mentioned method steps are carried out in one continuous operating cycle. Accommodated in a single unit are a device 6 for rolling together the edge portions of the wide, opposing sidewalls 1a, 1b of flat tube 1 by means of two flanging rolls 4, 5, and a device 7 connected thereto for welding the roll-closed edge portions in a semi- or fully-automatic TIG process. In addition, the apparatus comprises a flat-tube magazine 8, a hole-puncher 9, brushes 10, a transverse conveyor 11, and a magazine 12 for finished radiator elements. 
     The finished radiator elements are then conveyed from magazine 12 to a further apparatus (not shown) where they are welded to a collecting pipe for supplying hot water and a collecting pipe for carrying off cooled water. 
     No additional components such as sealing covers, filler parts, or support parts are necessary for producing the radiator element. With simple means, a cleanly and symmetrically formed element is obtained, any subsequent grinding or smoothing being superfluous.