Patent GB-1399427-A (GB)
Title: Method of forming a can end member
IPC: B21D51/44
Filed: 1973-02-06
Abstract: 1399427 Making can ends; stamping VAN DORN CO 6 Feb 1973 [20 Oct 1972] 5737/73 Headings B3A B3J and B3Q [Also in Division B8] A method of making a can end member having a recessed end panel or wall 9 and a triple fold 84, Fig. 24, comprises drawing a metal blank having an annular frusto-conical band 10 joined to the wall 9 and to a side wall by curved corners 11, 12, Fig. 2, forming a shoulder 22 in the band 10, Fig. 8, successively bulging areas of the band below the shoulder and coining and scoring the band above the shoulder prior to folding the band at the shoulder and lower curved corner to form the triple fold. The initial drawing operation is performed in a blanking press including a punch (1) and die cavity forming members (2), (3), Fig. 3 (not shown). A secondary punch (6) draws down the outer edge of the rim 8 at the end of the drawing operation. The downturned edge of the rim 8 is curled between rolls (13), Fig. 4 (not shown), to form a bead 14, Fig. 13. The blank is next drawn between die members 16-19, Fig. 8, the die members 16, 18 forming the upper part 20 of the band 10 horizontally to shape the shoulder 22. A rivet bubble 25 is drawn in the wall 9 by a punch 27 working in co-operation with a cavity formation 26 in the member 17. The metal in the zone 28 of the bubble is pinched to prevent thinning of the metal in the zone 29 when a rivet head is formed ultimately. The member 17 also contains openings (32), Fig. 9 (not shown), which co-operate with punches (33) to form two bubbles (30) which are subsequently formed into dimples 57, Fig. 13. In the next drawing stage, Fig. 10 (not shown), the height of the band part 21 is reduced by moving the shoulder 22 radially inwardly and decreasing the radius of the lower comer 23, while the rivet bubble 25 and bubbles (30) are shaped into the bubble 53 and dimples 57, Fig. 13. At the same time the band part 20 and the wall 9 around the rivet bubble 53 are coined by punches (35), (37) to reduce the thickness of the metal. The blank is then positioned on die cavity forming members 63, 64, Fig. 16, and is located with respect to scoring punches 60, 62, by a pin 65 which enters the bubble 53. A spring loaded punch member 61 holds the blank while a score blade 66 on the punch 60 forms an annular tear out score line in the coined surface of the band part and a score blade 68 on the punch 62 forms a straight bending score line in the coined portion of the wall 9. The tear out score line is preferably deeper than the bending score line. The radius of the corner 23 is further reduced to lower the height of the band part 21 still further. The scored blank is then placed in a die cavity formed by members (77), (78), (79), Fig. 19 (not shown), and while secured and located therein by punch members (75), (76), the fold 84 is made by a punch (74), which engages the coined area of the band part 20. The punch 74 is so shaped that the fold is thicker through an arc subtending an angle of 50 degrees on either side of the bubble 53, Fig. 20 (not shown). The folded blank is next placed on die cavity members 100, 101, and a lower staking punch 102, Fig. 24. A pull tab 94 is placed over the bubble 53 and is located by the dimples 57. A punch 97 is lowered to clamp the tab to the coined area around the bubble 53 and tab locators 99 are also lowered to provide accurate location of the tab. A punch 98 is driven downwardly to form the bubble 53 into a rivet 110, 111, thereby securing the tab. The final operation comprises stamping indicia on the can end and determining whether the tab 94 is missing or incorrectly positioned. The location of the annular score line inwardly of the outer periphery of the fold results in the fold extending outwardly of the sharp edge formed when the centre of the can end is pulled off.