Importance

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Abstract

In a hydraulic winch having a clutch assembly for freeing a drum of the winch for free falling rotation, a control system is provided for controlling operation of the clutch assembly. The supply system includes a directional control valve shiftable between a first position in which fluid is supplied to the clutch assembly at a first pressure which maintains the clutch in the disengaged position to allow free fall of the drum, and a second position in which fluid is supplied to the clutch assembly at a second pressure which allows the clutch to return to the engaged position, braking free fall of the drum. A timing element shifts the directional control valve to the second position after fluid has been supplied to the clutch assembly at the first pressure for a predetermined length of time. The timing element is a kick-down sequence valve that is connected directly between the clutch assembly and the directional control valve and that is movable from a flow-preventing position to a flow-permitting position once the fluid supplied to the kick-down sequence valve reaches a predetermined pressure. The kick-down sequence valve in the flow-permitting position supplies pressure to the directional control valve to shift the directional control valve to the second position so that fluid is supplied to the clutch at the second pressure.

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First Claim