Patent ID: 8261655

Claim:
A locking piston assembly ( 100 ) including a piston chamber ( 107 ), a piston rod ( 106 ) configured to be substantially extended from and substantially retracted into the piston chamber ( 107 ), and a piston head ( 108 ) coupled to the piston rod ( 106 ) and configured to move reciprocally in the piston chamber ( 107 ), with the locking piston assembly ( 100 ) being characterized by: at least one lock ( 120 ) configure to mechanically lock the piston head ( 108 ) and the piston rod ( 106 ) in at least a substantially filly extended position and configured to unlock the piston head ( 108 ) and the piston rod ( 106 ) in a presence of a pressurized fluid provided to retract the piston rod ( 106 ), with the at least one lock ( 120 ) comprising: a biasing member ( 122 ); a locking member ( 124 ); a locking member upper seal ( 125 ) configured to continuously seal the locking member ( 124 ) to a lock bore ( 128 ) configured to receive the locking member ( 124 ); and a locking member lower seal ( 126 ) configured to block and unblock a piston chamber port ( 153 ) extending between the lock bore ( 128 ) and piston chamber ( 107 ) with an upper cross-sectional area being greater than a lower seal cross-sectional area, wherein the lower seal cross-sectional area requires a first pressure to move the locking member ( 124 ) to an open position and the upper seal cross-sectional area requires a second pressure to keep the locking member ( 124 ) at the open position , and wherein the first pressure is greater than the second pressure; wherein the locking member ( 124 ) and the locking member ( 126 ) block the piston chamber port ( 153 ) when in a lock position and unblock the piston chamber port ( 153 ) when in an unlock position and wherein the pressurized fluid is introduced into the piston chamber ( 107 ) and the piston rod ( 106 ) is retracted only after the at least one lock ( 120 ) is unlocked.