Patent GB-878713-A (GB)
Title: Can body and method of forming same
IPC: B21D51/26
Filed: 1960-04-25
Abstract: 878,713. Making cans; bending; welding. CONTINENTAL CAN CO. Inc. April 25, 1960 [March 9, 1960], No. 14448/60. Classes 83 (2) and 83 (4). In a process of producing can bodies, a metal strip of substantially the can circumference in width is formed into a tube with overlapping edges which are heated and pressed together so as to form a welded joint of substantially the same thickness as the strip, the metal in the welding zone is treated with fluid to reduce oxidation and discoloration of the metal and to cool the joint, and a coating is applied to at least a portion of the welded tube which is then cut into can lengths. Strip stock S from a coil 10, Fig. 1, is scored transversely by cutters 13, 14 on rollers 11, 12, passed through a shaping channel 16 where it is formed to tubular shape with the edges separated by a guide roller 18. The edges are then brought into overlapping or abutting relation according to the kind of seam required. As shown in Fig. 1, the edges are heated by electrodes 21 connected to a high frequency generator 19, brought into overlapping relation and welded and forged between an outer roll 25 and an inner roll 24 carried by a horn 22. In the case of a butt weld the rolls 24, 25 would apply only sufficient pressure to prevent formation of a longitudinal ridge. External and internal spray tubes 26, 26<SP>1</SP> cool the welded seam by means of a gas or a liquid. A protective stripe may be sprayed on to the outer or inner sides of the seam by sprays 28, 29. As the tube passes beyond the end of the horn 22 it is first held against vertical movement by rollers 30 and is then forced upwardly by an inclined belt 31 so as to break the tube along the score lines to form can body lengths C joined by a connecting strip 33 formed by the welded seam. The strip 33 is subsequently sheared by a reciprocating knife 34 (not shown). Instead of using a channel 16, the strip may be shaped to tubular form by an endless belt 36, Fig. 3, passing around concave rollers 37, 39 and co-operating with a convex roller 38. In the modification shown in Fig. 4, the strip is bent into square section tube by co-operating pairs of concave and convex rolls 41, 42, 43, four V-rolls 44 and four cylindrical rolls 45. The strip is not scored and can lengths are cut from the welded tube by a circular saw 63 travelling at the speed of the tube. A box 61 may contain interior and exterior spraying or coating devices and printing rolls. In another modification, a strip is scored, bent and welded to form a round tube which is then converted to square section by co-operating sets 82, 83, 84, 85, Fig. 5, each of four rolls. In the apparatus shown in Fig. 6, the work is heated by high frequency coils 92 prior to welding and forging the overlapping edges. The seamed tube passes through a post-decorating device 101 and then through a series of rolls 107 arranged to flatten and twist the tube so as to break it along the score lines 15. The connecting pieces of seam strip between the can lengths C are severed by a rotary cutter 103 comprising a driven shaft 104 carrying a block 105 with flat sides equal to the length of a can and with knives 106 at the intersections of the sides. In the form shown in Fig. 8, radially movable jaws 113 momentarily clamp the tube while the projecting end is struck and broken off at a score line by a lobe 114 on a wheel 115.