Patent GB-754494-A (GB)
Title: Improvements in or relating to the manufacture of cans
IPC: B21D51/18
Filed: 1954-06-25
Abstract: 754,494. Making cans. S.A.S. GESTIONE GUINZIO ROSSI & CO. June 25, 1954 [Nov. 26, 1953], No. 18757/54. Classes 83 (2) and 83 (4). Cupping.-A process for manufacturing aluminium alloy cans comprises submitting an aluminium alloy disc plated with pure aluminium to a number of deep drawing, upsetting and drawing steps to form a one-piece aluminium alloy can having an aluminiumplated inner surface. The can comprises a cylindrical body portion 1 and a convex bottom 2 merging into the wall of the body by means of an enlarged ring portion 3. Handles 5 are secured to a thickened portion 4 of the body wall above which the wall tapers into a neck portion 7 provided with a beaded top edge 7a. In the initial deep drawing operation the plated disc 9 is placed in a press provided with three rings 11, 12 and 13. A die ring 14 is arranged between the rings 11 and 13 and has a curved surface 15 which supports the disc 9. The ring 13 has a recess 16 for accommodating the disc and the ring 11 houses a spring-loaded split ring 17. Under the action of a punch 18 the disc is drawn to the shape 19 shown in Fig. 5. The drawn blank 19 is hot pressed at 480‹ C. to reduce the thickness of the bottom and form an annular thickened portion 23 (Fig. 6) after which a second pressing forms the bottom into the shape shown in Fig. 7. The formed blank 24 is drawn in a press comprising upper and lower drawing rings 31 and 33 respectively, spaced apart by a cylindrical member 32, a centring ring 30, a spring-loaded split-ring 34 and a punch 35. This operation lengthens and reduces the wall thickness of the blank and shapes the bottom of the blank on a former 36. The resulting blank is annealed for two hours and a half at 300-400‹ C. and the upper edge of the blank is trimmed. In the next drawing operation the blank is passed through a die ring 44 beneath which is disposed a spring-loaded split-ring 45 by means of a punch 47 formed with an annular groove 48. In this operation the wall of the blank 40 is lengthened and reduced in thickness and an inward enlargement or band 49 (Fig. 12) is formed in the wall by the groove 48. On upward movement of the punch, the drawn blank 50 is retained by the split-ring 45 and the punch displaces the band 49 outwardly to form a blank as shown in Fig. 15. The blank is next successively submitted to a number of shaping operations to form the can neck. In the first of these operations a punch is employed comprising a top-plate 57 (Fig. 16) carrying two coaxial annular members 60, 61 with a gap 62 therebetween. In the subsequent operations the profiles of the annular members are varied to gradually shape the neck towards its final shape. The last punch is shown in Fig. 18. Alternatively, the neck may be shaped in one operation using a die heated to 450‹ C. The top edge of the can is trimmed and beaded as shown in Fig. 20 and the handles welded to the thickened portion 49. Finally, the can is heated for an hour at 540‹ C. and then hardened by quenching in water whereafter it is aged for eight hours at 160‹ C., pickled and the plated inner wall polished by rotating the can filled with steel balls. The finished can is closed by a polyethylene disc 64. Specification 621,629 is referred to.