Patent ID: 6068245
Filing Date: 2000-05-30
Classification: B21D

Abstract:
A delayed return cushion unit, comprising:an outer tube having an inner diameter and a top and a bottom;a base plate disposed at the bottom of said tube;an annular-shaped head plate disposed at the top of said tube and having an inner cylindrically-shaped wall;an inner tube having in outer diameter and in inner diameter and mounted to extend between said head plate and said base plate within said outer tube;an annular-shaped outer piston mounted between said inner and outer pistons to reciprocate between said head plate and said base plate;an inner piston/rod mounted in said inner tube to reciprocate vertically therein between a retracted, compressed position and an extended, rest position, the rest position including said piston/rod extending through the inner cylindrically-shaped wall of said head plate and upwardly of said head plate;wherein said outer tube, base plate, head plate, inner tube, outer piston and inner piston/rod define:a gas chamber bounded by said outer tube, inner tube, head plate and outer piston,an outer hydraulic chamber bounded by said outer tube, inner tube, base plate and outer piston, andan inner hydraulic chamber bounded by said inner tube, base plate and inner piston/rod;seal means for preventing leakage of gas from said gas chamber and hydraulic fluid from said hydraulic chambers;passageway means providing communication between the outer hydraulic chamber and the inner hydraulic chamber and including a check valve permitting substantially unrestricted fluid flow from the inner hydraulic chamber to the outer hydraulic chamber, but severely restricting fluid flow from the outer hydraulic chamber to the inner hydraulic chamber;gas in the gas chamber having a pressure greater than ambient pressure;hydraulic fluid disposed in said inner and outer hydraulic chambers; and,means for retaining said head plate, base plate, inner tube, outer piston and inner piston/rod contained substantially entirely within said outer tube.