GB1408679A - Apparatus for making a drawn article - Google Patents

Abstract

1408679 Cupping REYNOLDS METALS CO 18 April 1973 18775/73 Heading B3Q Cup-shaped starting blanks are formed on apparatus having a hold-down 40, Fig. 6, and a drawing ram 44 both of which have coaxial piston extensions 42, 47 in a common chamber 49 so that movement of the hold-down 40 in one direction causes movement of the ram 44 in the opposite direction, restricting and separating means 66, 67 being provided on at least one of the pistons so as to divide the chamber into interconnected parts with restricted fluid flow therebetween during at least part of a drawing operation whereby a back pressure is created which increases the hold-down force. Four dies 12, Fig. 1, which also blank workpieces from strip 13, are mounted on a holder 17 movable by a ram 18 for co-operation with stationary cutting rings 59. Strip from a roll 14 is fed by rollers 15 and lubricated by rolls 16, An ejector 28 surrounds the die 12 and each die is associated with a separate ram 44. The chamber 49 is supplied with a constant volume of an incompressive fluid, e.g. oil, through a check valve (51), Fig. 2 (not shown), by a reservoir (50), a relief valve (54) being in a return line. A ring 67 onthe piston 41 surrounding a hub 66 on the piston 47 divides the chamber 49, leaving an annular throttle gap between the two through which movement of the hold-down pumps fluid with a resulting back pressure. The back pressure is reduced by at least one groove 77 in the hub 66 as the stroke progresses. Alternatively, conical zones may be provided on the hub, Fig. 8 (not shown). The normal hydraulic relationship between the pistons 41, 47 is one or two to one.