Patent ID: 6349582
Filing Date: 2002-02-26
Classification: B21J

Abstract:
A die system for full enclosed die forging in which an enclosed cavity is formed between an upper die attached to the side of a slide and a lower die mounted to the side of a bolster, and a workpiece stock disposed in the cavity is pressurized to be diverted with an upper counter-punch in the upper die and a lower counter-punch in the lower die and is thereby forged within the confines of the cavity, the system comprising:a pressure means disposed in at least one of a first region above said upper die and a second region below said lower die for applying pressure to at least one of said upper and lower dies from at least one of their upper and lower sides to act to enclose said cavity at least unilaterally; said pressure means comprises a first pressure means disposed from above said upper die applying pressure to said upper die from its upper side and a second pressure means diposed below said lower die for applying pressure to said lower die from its lower side, and first and second pressure means acting to enclose said cavity bilaterally; a back pressure imparting means comprising a cylinder actuator disposed in at least one of a third region above said upper counter-punch and a fourth region below said lower counter-punch for applying back pressure to at least one of said upper and lower counter-punches to force said workpiece stock being formed to be diverted at least unilaterally in said cavity; said back imparting pressure means comprises a first back pressure imparting means disposed above said upper counter-punch for applying back pressure to said upper counter-punch from its upper side and a second back pressure imparting means disposed below said lower counter-punch for applying back pressure to said lower counter-punch from its lower side, said first and second back pressure imparting means forcing said workpiece stock being formed to be diverted bilaterally in said cavity; and a back pressure removal means comprising an electromagnetic valve via which a fluid pressure chamber of said cylinder actuator is connected to a fluid reservoir, for removing said back pressure immediately before an internal pressure of said cavity rises upon said workpiece stock filling said cavity, by opening said electromagnetic valve to permit a pressure fluid in said pressure chamber to drain into said reservoir, said back pressure removal means is adapted to act on said first and second back pressure imparting means for removing each said back pressuring upon said workpiece stock filing said cavity.