Patent ID: 6804983
Filing Date: 2004-10-19
Classification: B21D

Abstract:
A die cushion apparatus that can hold a blank during the process of passing the blank with a die, the apparatus comprising:a support member that can hold the blank; a gas pressure cylinder that pushes the support member upwards; a hydraulic cylinder having an upper rod connected to the support member; a first pneumo-hydraulic converter for secondary lifting, the first converter comprising a first cylinder and a secondary lifting piston, wherein the lifting piston partitions an interior of the first cylinder into a first oil chamber and a first gas chamber, the first oil chamber communicating with a second oil chamber at an upper rod side of the hydraulic cylinder; a check valve that allows oil to flow from a third oil chamber of the hydraulic cylinder at a side opposite the rod to the second oil chamber of the hydraulic cylinder; a drain port that communicates with the second oil chamber on the side of the upper rod of the hydraulic cylinder, whereby when the die passes a bottom dead center point, the drain port is closed, and while the die is traveling from the bottom dead center point to a top dead center point, pressure in the first gas chamber of the first pneumo-hydraulic converter for secondary lifting is reduced, thus moving the secondary lifting piston to a side of the first gas chamber; and a second pneumo-hydraulic converter for locking with a locking piston that partitions an interior of the second converter into a fourth oil chamber and a second gas chamber, the fourth oil chamber communicating with the second oil chamber on the side of the upper rod of the hydraulic cylinder, whereby when the die passes the bottom dead center point, an output is sent from a cushion stroke sensor causing pressure in the second gas chamber of the second pneumo-hydraulic converter for locking to be increased, thus the locking piston is moved to a side of the fourth oil chamber of the second pneumo-hydraulic converter for locking.