This invention relates to controls for hydraulically operated winches or the like.
Prior art of possible relevance includes U.S. Pat. No. 3,519,247 to Christison.
Winches are used in a large variety of operations and, as a consequence, there are winch constructions available with widely varying degrees of sophisticated control and drive equipment. Some of the more sophisticated winch constructions are hydraulically operated and include a hydraulic motor for driving a winch drum. Typically, there is provided a hydraulically disengaged brake which brakes the drum to prevent unduly rapid lowering of a load to be hoisted by the winch, and also multiple-speed, hydraulically controlled transmissions interconnect the drum and the drive motor therefor.
In such constructions, it is highly desirable to provide a means for regulating the amount of control fluid applied to the hydraulically disengaged brake to control the degree of disengagement of such brake and thereby control the rate of descent of an elevated load. It is also desirable that means be provided whereby a load hoisted by the winch can be lowered even when the prime mover for the hydraulic pump providing fluid under pressure for the winch system is inoperative.
Moreover, it is desirable that any such means employed to enable lowering of the load when the prime mover is inoperative can be selectively disabled to prevent inadvertent or intentional lowering of the load when the winch operator is away from the operating station.
Finally, it is desirable that manual controls for the system be made as simple and as foolproof as possible.