Hydraulic apparatus for controlling movement of a member under loading

Claim 1

Apparatus including a supporting frame, a member mounted on said frame for biased movement in one direction, a hydraulic cylinder-piston assembly connected between said frame and said member and including a piston and a cylinder which houses said piston and includes opposed ends, a first fluid line extending from the one of said cylinder ends toward which said piston moves incident to movement of said member in said one direction, a second fluid line extending from the other of said cylinder ends, a source of pressure fluid, a control valve operatively connected to said source of pressure fluid and to said first and second fluid lines and including selectively operable means for supplying fluid to said one cylinder end and draining fluid from said other cylinder end and for supplying fluid to said other cylinder end and draining fluid from said one cylinder end, a first safety valve in said first fluid line responsive to pressure less than atomspheric and comprising a first body including therein a first main bore, and a cross bore extending transversely of and communicating with said first main bore, a first valve member movable in said cross bore between a position blocking said first main bore and a position permitting flow through said first main bore, said valve member including a face against which pressure can be applied to displace said valve member relative to said positions, means biasing said first valve member toward said flow permitting position, and first hydraulic means operatively connected to said first valve member for displacing said first valve member from said flow permitting position against the action of said means biasing said first valve member and including a first conduit communicating with said valve member face and with said other cylinder end for transmitting said pressure less than atmospheric, and a second safety valve responsive to pressure greater than atmospheric in said first fluid line and comprising a second body including therein a second main bore having therein a restriction, a duct in said second body communicating with said second main bore in by-passing relation to said restriction and including therein a valve seat, a second valve member movable relative to a position in engagement with said valve seat so as to close said duct, said second valve member including a face against which pressure can be applied to displace said second valve member relative to said duct closing position, means biasing said second valve member toward said duct closing position, and second hydraulic means operatively connected to said second valve member for displacing said second valve member from said duct closing position against the action of said means biasing said second valve member and including a second conduit communicating said second valve member face with said other cylinder end.