Method and drawing device for deep drawing of naphthenic sheet metal workpieces

摘要

1345227 Cupping CROWN CORK & SEAL CO Inc 2 June 1971 [11 Aug 1970] 18643/71 Heading B3Q A method of ironing and sizing the side walls of a shallow sheet metal cup to form a seamless container includes ironing the side walls of the cup to reduce the thickness of and substantially increase the length of the cup side walls, sizing the side walls without substantial decrease of thickness or increase in length and subsequently ironing the walls further. The cup is made from a steel blank, in a punch and die assembly 100, 102, Fig. 2. The assembly 100 includes a member 104, which rests on the blank, and a punch 106 provided with coolant passages, the coolant serving as a lubricant if required. The assembly 102 includes a drawing die 110 and an ironing die 112, the latter having a smaller clearance with respect to the punch 106 than the die 110. The die 112 reduces or eliminates the increase in thickness of the walls towards the top of the cup produced in the initial drawing stage. Lubricant is supplied through a plurality of recesses 132, 134 in the direction of the arrows FP, the recesses 132 being flared, Fig. 2b (not shown). The cup 10 is placed on a punch 26, Fig. 3, which comprises an ironing surface 30 and an ejecting member 31 and which may be provided with coolant passages. The first die 46 is a presizing ring which slightly reduces the wall thickness and is followed by a first ironing die 48. A sizing die 50 is located close to the die 48 to ensure accurate alignment of the cup during ironing, as any misalignment would result in pieces of the cup walls being pinched off and scoring of subsequent cups. A second ironing die 52 is located at a sufficient distance from the die 48 to ensure that the cup is only engaged by one ironing die at a time so as to decrease the risk of the cup walls fracturing or the bottom separating from the side walls. A second sizing die 54 is located close to the die 52. Finally the bottom of the cup is domed by a die 38 forcing the bottom of the cup against a concave surface 36 of the punch 26 to complete the seamless container.