Patent ID: 6941789

Claim:
A cushioning device for use in a press, which comprises: a die cushion pad; a cylinder; a piston arranged in the cylinder; a rod connecting the die cushion pad and piston and sliding within the cylinder; first and second chambers arranged within said cylinder and separated by said piston sliding within said cylinder, said second chamber containing a compressible fluid; and control means for controlling inflow and outflow of a fluid between said first and second chambers in association with a stroke of said piston, said control means including a communication hole arranged in the piston and a valve arranged within said communication hole, said valve being separate from said rod, said valve including upper and lower portions with a first larger thickness that prohibit passage of fluid between the upper and lower chambers, said valve further including a middle portion with a second smaller thickness that permits passage of fluid between the upper and lower chambers, said middle portion being arranged between said upper and lower portions; wherein; said communication hole and said valve work together so that during a downward motion of the piston from an upper location of the piston; a first cushioning force is firstly provided, a second cushioning force is secondly provided that is smaller than the first cushioning force, and a third cushioning force is thirdly provided that is larger than the second cushioning force.