Load-hoisting system having two synchronously rotating drums operating in parallel

A load-hoisting system for raising and lowering a load, said system comprising:

• a fixed frame,
• a motor and gear box unit mounted to said fixed frame and including two parallel outlet gears,
• a pair of hoisting devices, each connected to said load by a cable, said pair of hoisting devices each comprising:
• a winch drum selectively coupled respectively to a toothed disk driven by a respective outlet gear via a respective unidirectional friction clutch for raising said load, said cable being wound respectively about said winch drum and coupled to said load, said friction clutch including a fixed ratchet member, and an unidirectional intermediate disk including spring biased catches engagable with said fixed ratchet member for preventing said unidirectional intermediate disk from rotating in a direction corresponding to that of lowering the load,
• a central shaft for each winch drum supported by said fixed frame for rotation about an axis, said central shaft being fixedly connected to a respective drum, said friction clutch being operatively positioned between said toothed disk and said shaft, and said device further comprising means responsive to shaft rotation in a direction of lowering said load for effecting friction clutch engagement of said shaft by said outlet gear in a direction raising said load,
• means for synchronizing rotation of said central shafts comprising coupling plates and a coupling disk provided respectively with one of orthogonal, interengageable tenons and grooves such that shaft rotation of the drums in the direction of lowering of said load automatically effects clutch engagement between the shaft and the drums via said intermediate unidirectional disks, however, the intermediate disks via said catches and said fixed ratchet member are prevented from rotating in the direction corresponding to lowering of said load, thereby eliminating the possibility that the load will drive the motor in the direction of load lowering, and wherein any disruption of electrical feed to the motor prevents the load underfany condition from driving the motor, thereby eliminating the need for brakes within said system.