Freefall winch system and method of operation
AssigneeFMC Corporation
InventorsSteven C. Crawford, Thomas J. Feltman, Roger A. Steuck
Life of this patent
Estimating the term…
Abstract
One or more freefall systems for a crane or the like is disclosed, which system includes a protective circuit that includes three separate switches that must be closed before the winch can be placed in its freefall mode. A mode switch in the cab must first be closed, a brake pedal must be depressed to close a second switch, and a third switch must be held closed by the operator during freefall.
Claims15
In a freefall system for a crane or the like, said system including a frame, a drum shaft journaled on said frame, a drum journaled on said shaft and having a cable trained therearound for selectively raising and lowering a load, clutch means for selectively interconnecting the drum and the drum shaft, a clutch releasing circuit having switch means therein, brake means for selectively resisting and allowing rotation of said drum relative to said frame, means for selectively driving said drum shaft in load raising and load lowering directions:
- the improvement which comprises first control means for releasing said brake means;
- depressible manually operated brake actuating means for overriding said first control means for applying a drum braking force;
- and second control means including said switch means in said clutch releasing circuit for releasing said clutch, said second control means being effective to release said clutch means when said manual brake actuating means is partially depressed and when said switch means in said clutch releasing circuit is manually held closed.
A method of controlling a freefall winch system that includes a drum shaft journaled on a frame and a drum journaled on the shaft and having a flexible load carrying means trained therearound, a normally engaged clutch disposed between the shaft and the drum, a brake disposed between the drum and the frame and partially controlled by a brake pedal, and a protective freefall circuit for controlling the load during freefall:
- said method comprising the steps of hydraulically releasing the brake, rotating the shaft and said drum to raise the load, manually depressing the brake pedal for overriding the hydraulically released brake and for partially closing the freefall circuit by closing a portion of the circuit, manually holding another portion of said circuit closed against an opposing resilient force for releasing the clutch, maintaining control over the rotating drum and stopping the load prior to reaching the ground during freefall by manually applying adequate braking forces to the drum by pressure on the pedal, releasing manual pressure on the second portion of the circuit to deactivate the circuit and engage the clutch, and releasing the brake pedal.
Dependencies are inferred from the claim text.