Patent ID: 8061932
Filing Date: 2011-11-22
Classification: B63B

Abstract:
1. A boat lift comprising: a boat cradle; a support frame adapted for affixing to a vessel; at least one lift mechanism operatively connecting the cradle and the support frame for raising the boat cradle to an uppermost position and for lowering the cradle; the lift mechanism including: a hydraulic lift first cylinder having a lift piston sealingly disposed therein for reciprocating motion by hydraulic fluid force of a hydraulic fluid circuit; a first piston rod extending from a first end of the lift piston and passing sealingly through an end wall of the first cylinder to raise and lower the cradle; a second piston rod extending from a second end of the lift piston and lying completely within the first cylinder; the first and second piston rods lying along a common axis with a long axis of the lift cylinder; a lock cylinder disposed adjacent to the lift cylinder; a lock piston sealingly disposed within the lock cylinder for reciprocating motion therein under hydraulic fluid force to a retracted position and spring bias to an extended position; a first lock piston rod extending from a first end of the lock piston and having a rod engagement member connected to a free end thereof; the rod engagement member constructed to be received in a recess in the second piston rod when the first piston rod is in a most retracted position to thereby prevent motion of the lift piston when the first lock piston rod is in a most extended position; and the hydraulic fluid circuit so constructed that fluid for operating the lift piston is only free to flow through the lift cylinder when the lock piston rod is retracted.