Marine lift docks

Claim 1

A DRY DOCK HAVING AN OPEN END THROUGH WHICH MARINE VESSELS MAY ENTER COMPRISING: ELONGATED SIDE MEMBERS FORMING A FIXED FRAME ADAPTED TO BE SECURED IN FIXED POSITIONS; PAIRS OF OPPOSITELY DISPOSED GUIDE PULLEYS MOUNTED AT SPACED INTERVALS ON SAID MEMBERS ALONG THE ENTIRE LENGTH THEREOF; A SHIP CRADLE WITHIN THE CONFINES OF SAID MEMBERS, AND INSTRUMENTALITIES FOR RAISING AND LOWERING SAID CRADLE, SAID SAID INSTRUMENTALITIES INCLUDING (A) PAIRS OF LIFTING CABLES, (B) A PLURALITY OF ALIGNED WINDING DRUMS, AND (C) POWER MEANS CONNECTED TO SAID DRUMS FOR DRIVING THEM SIMULTANEOUSLY AT THE SAME ANGULAR VELOCITY, THE SAID DRUMS BEING AT THE REAR OF AND BETWEEN SAID SIDE MEMBERS AND MOUNTED FOR ROTATION ABOUT A COMMON AXIS EXTENDING LONGITUDINALLY OF SAID MEMBERS, ONE OF THE CABLES IN EACH PAIR OF CABLES BEING ATTACHED TO ONE SIDE OF SAID CRADLE AND THE OTHER CABLE IN SUCH PAIR BEING ATTACHED TO THE OPPOSITE SIDE OF THE CRADLE, EACH PAIR OF CABLES BEING ATTACHED TO ONE OF SAID DRUMS AND EXTENDING TRANSVERSELY AT RIGHT ANGLES THERETO OVER SELECTED PAIRS OF OPPOSITELY DISPOSED PULLEYS ON SAID SIDE MEMBERS, SAID CABLES FURTHER EXTENDING FROM SAID PREVIOUSLY MENTIONED PULLEYS ALONG SAID SIDE MEMBERS OVER SELECTED PAIRS OF OPPOSITELY DISPOSED PULLEYS AND DOWNWARDLY TO POINTS OF ATTACHMENT TO SAID CRADLE, THE ARRANGEMENT BEING SUCH THAT THE TOP OF THE DOCK IS LEFT OPEN AND UNOBSTRUCTED AND ALSO SUCH THAT THE DRUMS ARE ROTATED AT THE SAME SPEED AND THE CABLES CONSTITUTING EACH PAIR OF CABLES ARE WOUND ON THE DRUMS IN THE SAME DIRECTION AND EXTEND FROM THE DRUMS IN OPPOSITE DIRECTIONS TO THEREBY ELEVATE THE CRADLE WHILE MAINTAINING THE CRADLE IN A SUBSTANTIALLY HORIZONTAL PLANE AT ALL TIMES.