Boat Lift

Abstract

A boat lift for raising boats out of the water to facilitate maintenance and to reduce corrosion and contamination. The boat lift includes two or more boat lift assemblies positioned and spaced apart so that each boat lift assembly lifts approximately the same fraction of the overall weight of the boat. Each boat lift assembly has a lifting structure with bunk cushions mounted on pivoting bunk bases to prevent damage to the boat hull when lifting. Hydraulic lift mechanisms are enclosed within each boat lift assembly providing a cleaner appearance as well as protection against corrosion and fouling. A dual-pulley mechanism enables lifting distances substantially larger than the length of the lift mechanism. A hydraulic control system ensures that all the boat lift assemblies move up and down simultaneously and at the same rate, thereby maintaining the boat horizontal at all lifting positions.

1 . A boat lift, comprising multiple boat lift assemblies, at least one boat lift assembly including:
 a lift beam;   a lifting structure configured to move along the lift beam; and   a lifting actuator assembly, located inside the lift beam and configured to move the lifting structure.   
     
     
         2 . The boat lift of  claim 1 , wherein the lifting structure extends cantilevered from the lift beam. 
     
     
         3 . The boat lift of  claim 1 , wherein the boat lift assembly further comprises:
 a top beam for resting on a pier surface; and   a pier counterweight;   
       wherein a first end of the top beam is attached to an upper end of the lift beam, and wherein a second end of the top beam is attached to the pier counterweight. 
     
     
         4 . The boat lift of  claim 3  further comprising a pier deck grating over the top beam. 
     
     
         5 . The boat lift of  claim 1 , wherein in the boat lift assembly, the lifting structure further comprises:
 a carriage channel; and   a bunk base;   
       wherein the bunk base is attached to the carriage channel, and wherein the bunk pivot is pivotally attached to the bunk base. 
     
     
         6 . The boat lift of  claim 5  in which the lifting structure further comprises an outer beam extension extending from the carriage channel to the lift beam. 
     
     
         7 . The boat lift of  claim 6  further comprising at least one roller connected between the outer beam extension and the lift beam. 
     
     
         8 . The boat lift of  claim 7  further comprising at least a second roller connected between the carriage channel and the lift beam. 
     
     
         9 . The boat lift of  claim 1 , wherein in the boat lift assembly, the lifting structure further comprises a bunk pivot; and a bunk cushion attached to the bunk pivot. 
     
     
         10 . The boat lift of  claim 1 , wherein in the boat lift assembly, the lifting structure further comprises a guide post. 
     
     
         11 . The boat lift of  claim 1 , wherein in the boat lift assembly, a lower end of the lift beam is configured to be mounted on a wall of a pier. 
     
     
         12 . The boat lift of  claim 1 , wherein the boat lift assembly further comprises a submerged footing, and wherein a lower end of the lift beam is configured to be mounted on the submerged footing. 
     
     
         13 . The boat lift of  claim 1 , further comprising an actual within the lift beam and at least one cable connected to the actuator for raising and lowering the lifting structure. 
     
     
         14 . The boat lift of  claim 13 , in which the at least one cable comprises two cables. 
     
     
         15 . The boat lift of  claim 13 , in which the at least one cable is connected to the lifting structure through a damper to attenuate motion due to waves or wind. 
     
     
         16 . The boat lift of  claim 1 , wherein in the boat lift assembly, the lifting actuator assembly further comprises:
 an actuator rod;   a linear actuator, having a first end attached at an end of the lift beam, and wherein the linear actuator is configured to move the actuator rod linearly along a long axis of the lift beam;   a fixed pulley, attached at the first end of the linear actuator;   a moving pulley attached to an end of the actuator rod; and   a cable routed between the fixed pulley and the moving pulley;   
       wherein an end of the cable protrudes from the lifting actuator assembly, and wherein motion of the moving pulley away from the fixed pulley causes the protruding end of the cable to be retracted into the lifting actuator assembly. 
     
     
         17 . The boat lift of  claim 16 , wherein the linear actuator comprises a hydraulic cylinder. 
     
     
         18 . The boat lift of  claim 16 , wherein the linear actuator comprises a motorized lead-screw actuator, a motorized rack-and-pinion geared actuator, or a motorized worm-gear actuator. 
     
     
         19 . The boat lift of  claim 16 , wherein in the boat lift assembly, the retraction of the cable into the lifting actuator assembly raises the lifting structure. 
     
     
         20 . The boat lift of  claim 16 , further comprising:
 a control computer;   a hydraulic control system, configured with a hydraulic line to at least one boat lift assembly;   a connection between the control computer and the hydraulic control system, the connection being configured to send commands from the control computer to the hydraulic control system;   a non-volatile computer-readable storage medium, configured to store instructions to be executed by the control computer; and   a connection between the control computer and the non-volatile computer-readable storage medium, the connection being configured to relay computer instructions to the control computer.   
     
     
         21 . The boat lift assembly of  claim 1  in which the lift beam is sealed to prevent water from contacting the lifting actuator assembly. 
     
     
         22 - 36 . (canceled)