Synchronous cable transmission system for boat lifts

A four piling boatlift, comprising:

• a pair of upstanding inboard pilings disposed in longitudinally spaced apart relation to one another;
• a pair of upstanding outboard pilings disposed in transversely spaced apart relation to said inboard pilings and in longitudinally spaced apart relation to one another;
• a first beam having an inboard end disposed in closely spaced relation to a first inboard piling of said pair of inboard pilings and an outboard end disposed in closely spaced relation to a first outboard piling of said pair of outboard pilings;
• a second beam having an inboard end disposed in closely spaced relation to a second inboard piling of said pair of inboard pilings and an outboard end disposed in closely spaced relation to a second outboard piling of said pair of outboard pilings;
• a first cable drum assembly mounted to said first inboard piling near an upper end thereof;
• said first cable drum assembly including a longitudinally disposed master cable drum and a slave cable drum disposed in transversely spaced apart, parallel relation to said master cable drum, said master cable drum and said slave cable drum being disposed in a common horizontal plane;
• a first motor means for rotating said master cable drum;
• a first interconnecting means for translating rotation of said master cable drum into simultaneous and corresponding rotation of said slave drum;
• a first master cable following a path of travel that includes a downward path from a first end of said master cable drum to an inboard end of said first beam, a substantially level path through a hollow interior of said first beam, exiting said first beam at an outboard end thereof, an upward path extending to a first outboard pulley mounted near a top of said first outboard piling, and a downward path to a first anchoring means secured to said first outboard piling so that reeling of said first master cable relative to said first cable drum lifts said first beam and so that unreeling lowers said first beam;
• a second cable drum assembly mounted to said second inboard piling near an upper end thereof;
• said second cable drum assembly including a longitudinally disposed second master cable drum and a second slave cable drum disposed in transversely spaced apart, parallel relation to said second master cable drum, said second master cable drum and said second slave cable drum being disposed in a common horizontal plane;
• a second motor means for rotating said second master cable drum;
• a second interconnecting means for translating rotation of said second master cable drum into simultaneous and corresponding rotation of said second slave drum;
• a second master cable following a path of travel that includes a downward path from said second master cable drum to an inboard end of said second beam, a substantially level path through a hollow interior of said second beam, exiting said second beam at an outboard end thereof, an upward path extending to a second outboard pulley mounted near a top of said second outboard piling, and a downward path to a second anchoring means secured to said second outboard piling so that reeling of said second master cable relative to said second cable drum lifts said second beam and so that unreeling lowers said second beam;
• a first slave cable having a first end secured to said first slave cable drum and a second end secured to an inboard end of said first beam;
• a second slave cable having a first end secured to said second slave cable drum and a second end secured to an inboard end of said second beam;
• whereby the weight of a boat lifted and lowered by said boat lift is distributed substantially equally between said first and second master cables and said first and second slave cables;
• and
• whereby all of said cables are in synchronization with one another so that the boatlift is lifted and lowered in a level plane.