Apparatus and method for cushioning the action of draw dies operating in

Abstract

A draw die operable within a straightside press includes a lower die shoe with a lower die; pressurized lift cylinders each having an upwardly extending piston rod and an axial resistance to compression; a generally ring-shaped cushion defining a central hole and a plurality of lock beads extending upwardly in spaced-apart relation surrounding the central hole, wherein the cushion surrounds the punch, is sized and configured to support a blank atop the beads and over the punch for draw forming the blank over the punch, and is supported by the lift cylinders; a plurality of cushion units held by the shoe and each having an upwardly extending piston rod and an axial resistance to compression; an upper die defining a second stamping shape which mates with the first stamping shape; a plurality of hydraulic shock absorbers held by the upper die and having an axial resistance to compression and a piston rod that extends downwardly toward the cushion. A ram mechanism moves the upper die downwardly where the shock absorbers engage the cushion and accelerate it downwardly, depressing the lift cylinders somewhat. Upon further downward movement of the upper die and cushion, the cushion cylinders become engaged and offer sufficient resistance as they are depressed to bind a blank between upper die and cushion and to draw form the blank between the two dies. After reaching the bottom of the stroke, the upper die retracts upwardly, along with the cushion lifted by the lift cylinders, but the pistons rods of the self-contained cushion units are delayed in their upward return by an internal valving system.