Leveling boat lift

Abstract

A boat lift has a boat cradle mounted on a top side of a lift. Wheels are attached to the lift frame, and vertically oriented extendable legs are attached to the lift frame and configured such that with each leg retracted to a fully retracted position the lift frame is supported on the wheels. A leg controller is operative, in a leveling mode, to extend or retract each leg independently to position bottom ends of the legs at different vertical positions on an uneven lake floor as required to support the lift frame in a horizontal orientation with the wheels raised above the lake floor, and is operative in a lifting mode to extend or retract all legs simultaneously to move the lift frame up or down while maintaining the lift frame in the horizontal orientation.

1 . A boat lift apparatus comprising:
 a lift frame and a boat cradle mounted on a top side of the lift frame and configured to support a boat;   a plurality of wheels attached to the lift frame;   a plurality of vertically oriented extendable legs attached to the lift frame and configured such that with each leg retracted to a fully retracted position the lift frame is supported on the wheels for movement along the ground by a tow vehicle connected to the lift frame;   a leg controller operative, in a leveling mode, to extend or retract each leg independently to position bottom ends of the legs at different vertical positions on an uneven lake floor as required to support the lift frame in a substantially horizontal orientation with the wheels raised above the lake floor; and   wherein the leg controller is operative in a lifting mode to extend or retract all legs simultaneously to move the lift frame up or down while maintaining the lift frame in the substantially horizontal orientation.   
     
     
         2 . The apparatus of  claim 1  wherein at least one leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward. 
     
     
         3 . The apparatus of  claim 2  further comprising a foot plate on a bottom end of the piston. 
     
     
         4 . The apparatus of  claim 1  wherein each leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward. 
     
     
         5 . The apparatus of  claim 4  wherein, for each hydraulic cylinder, the leg controller is operative to selectively control a flow of hydraulic fluid to the barrel to extend the piston, to retract the piston, and to lock the piston in a fixed position relative to the barrel. 
     
     
         6 . The apparatus of  claim 5  wherein when the leg controller is in the lifting mode, the flow of hydraulic fluid to each hydraulic cylinder is substantially the same. 
     
     
         7 . The apparatus of  claim 6  comprising four legs, each leg attached in proximity to a corner of a substantially rectangular lift frame. 
     
     
         8 . The apparatus of  claim 1  wherein at least one extendable leg comprises an inner tube telescoping inside an outer tube, and an extendable actuator operative to extend the inner tube to a fully extended position with respect to the outer tube, and to retract the inner tube to a fully retracted position with respect to the outer tube; and wherein the extendable actuator is attachable to one of the inner and outer tubes at a plurality of locations such that a length of the at least one extendable leg can be adjusted. 
     
     
         9 . The apparatus of  claim 8  wherein the at least one extendable leg comprises a stop mechanism operative to prevent the inner tube from retracting into the outer tube to prevent the lift frame from moving downward. 
     
     
         10 . The apparatus of  claim 9  wherein the stop mechanism can be adjusted to support the lift frame at a plurality of vertical locations. 
     
     
         11 . A method of raising a boat above a surface of a lake for storage, the method comprising:
 mounting a boat cradle on a top side of a lift frame and configuring the boat cradle to support the boat;   mounting a plurality of wheels to the lift frame;   attaching a plurality of vertically oriented extendable legs to the lift frame and retracting each leg to a fully retracted position such that the lift frame is supported on the wheels, and connecting a tow vehicle to the lift frame;   maneuvering the tow vehicle to place the lift frame in a desired position in the lake with the wheels resting on an uneven lake floor of the lake, and disconnecting the tow vehicle;   with a leg controller in a leveling mode, extending or retracting each leg independently to position bottom ends of the legs at different vertical positions on the uneven lake floor as required to support the lift frame in a substantially horizontal orientation with the wheels raised above the lake floor;   with the leg controller in a lifting mode, extending or retracting all legs simultaneously to move the lift frame up or down as required to position the boat cradle below the surface of the lake while maintaining the lift frame in the substantially horizontal orientation;   maneuvering the boat to float on the surface of the lake above the boat cradle; and with the leg controller in the lifting mode, extending all legs simultaneously to move the lift frame up and raise the boat above the surface of the lake while maintaining the lift frame in the substantially horizontal orientation.   
     
     
         12 . The method of  claim 11  wherein at least one leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward. 
     
     
         13 . The method of  claim 12  further comprising a foot plate on a bottom end of the piston. 
     
     
         14 . The method of  claim 11  comprising front right and left legs and rear right and left legs, and wherein each leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward. 
     
     
         15 . The method of  claim 14  wherein, for each hydraulic cylinder, the leg controller is operative to selectively control a flow of hydraulic fluid to the barrel to extend the piston, to retract the piston, and to lock the piston in a fixed position relative to the barrel. 
     
     
         16 . The method of  claim 15  wherein when the leg controller is in the lifting mode, the flow of hydraulic fluid to each hydraulic cylinder is substantially the same. 
     
     
         17 . The method of  claim 16  wherein the lift frame is substantially rectangular and comprising attaching a leg in proximity to each corner of the lift frame. 
     
     
         18 . The method of  claim 11  wherein at least one extendable leg comprises an inner tube telescoping inside an outer tube, and an extendable actuator operative to extend the inner tube to a fully extended position with respect to the outer tube, and to retract the inner tube to a fully retracted position with respect to the outer tube; and wherein the extendable actuator is attachable to one of the inner and outer tubes at a plurality of locations such that a length of the at least one extendable leg can be adjusted. 
     
     
         19 . The method of  claim 18  wherein the at least one extendable leg comprises a stop mechanism operative to prevent the inner tube from retracting into the outer tube to prevent the lift frame from moving downward. 
     
     
         20 . The method of  claim 19  wherein the stop mechanism can be adjusted to support the lift frame at a plurality of vertical locations.