Hydraulic control system for two-speed winch

Claim 2

A hydraulic control system for a two-speed winch including a winch drum driven by a pair of hydraulic motors drivingly connected to a common power transmission, said control system comprising: a source of hydraulic pressure fluid, a hydraulic fluid circuit interconnecting said source and said hydraulic motors, directional control valve means in said circuit (a) operable in a first neutral position to interrupt flow of pressure fluid from said source to said motors, (b) operable in a second hoist position to direct fluid under operating pressure to said motors in a direction for winding cable on said drum and (c) operable in a third lowering position to direct fluid under operating pressure to said motors in a direction for unwinding cable from said drum, speed control valve means in said circuit between said directional control valve means and said motors operable in a first low-speed position to connect siad motors hydraulically in parallel with said source and operable in a second highspeed position to connect said motors hydraulically in series with said source when said directional control valve is in either its hoist or lowering said positions, said speed control valve means being normally biased to said low-speed position and being selectively positionable in said high-speed position, with said directional control valve means in said hoist position, only when the maximum inlet pressure at said motors is below a predetermined pressure level.

Claim 3

A control system according to claim 1 wherein said speed control valve means is selectively operable by a fluid pressure tending to move said valve means to said high-speed position and is sensitive to said motor inlet pressure in a manner opposing movement of said valve means to said high-speed position when said directional control valve is in said hoist position.

Claim 4

A control system according to claim 1 wherein said speed control valve means comprises a spool valve having a valve spool and means biasing said spool to the low-speed position of said valve, fluid pressure valve-operating means selectively operable to act against said spool in a direction tending to shift said spool to said high-speed position, and speed-limiting means including pilot passage means in said circuit extending, with said circuit in a hoist mode, between an inlet side of one of said motors and said valve means in a manner such that motor inlet pressure acts on said spool in a direction opposing said fluid pressure valve-operating means.

Claim 5

A control system according to claim 3 wherein motor inlet pressure above a predetermined pressure level indicative of a winch load beyond the high-speed mode capacity of said motors is operable acting throUgh said pilot passage means to shift said spool to said low-speed position.

Claim 6

A control system according to claim 1 wherein said speed control valve means when in said high-speed position completes a recirculation subcircuit operable in the hoist and lowering modes of said circuit to recirculate pressure fluid from the outlet side of at least one of said motors to the inlet side of at least one of said motors to inhibit cavitation at said motors.

Claim 7

A hydraulic control system for a two-speed winch including a winch drum driven by a pair of hydraulic motors drivingly connected to a common power transmission, said control system comprising: a source of hydraulic pressure fluid, a hydraulic fluid circuit interconnecting said source and said hydraulic motors, directional control valve means in said circuit (a) operable in a first neutral position to interrupt flow of pressure fluid from said source to said motors, (b) operable in a second hoist position to direct fluid under operating pressure to said motors in a direction for winding cable on said drum and (c) operable in a third lowering position to direct fluid under operating pressure to said motors in a direction for unwinding cable from said drum, speed control valve means in said circuit between said directional control valve means and said motors operable in a first low-speed position to connect said motors hydraulically in parallel with said source and operable in a second high-speed position to connect said motors hydraulically in series with said source when said directional control valve is in either its hoist or lowering said positions, said speed control valve means when in said high-speed position being operable to complete a recirculation subcircuit operable in the hoist and lowering modes of said circuit to recirculate pressure fluid from the outlet side of at least one said motor to the inlet side of at least one said motor and thereby inhibit cavitation at said motors.

Claim 8

A hydraulic control system for a two-speed winch including a winch drum driven by a pair of hydraulic motors drivingly connected to a common power transmission, said control system comprising: a source of hydraulic pressure fluid, a hydraulic fluid circuit interconnecting said source and said hydraulic motors, directional control valve means in said circuit (a) operable in a first neutral position to interrupt flow of pressure fluid from said source to said motors, (b) operable in a second hoist position to direct fluid under operating pressure to said motors in a direction for winding cable on said drum and (c) operable in a third lowering position to direct fluid under operating pressure to said motors in a direction for unwinding cable from said drum, speed control valve means in said circuit between said directional control valve means and said motors operable in a first low-speed position to connect said motors hydraulically in parallel with said source and operable in a second high-speed position to connect said motors hydraulically in series with said source when said directional control valve is in either its hoist or lowering said positions, said speed control valve means when in said high-speed position being operable to complete a recirculation subcircuit operable in the hoist and lowering modes of said circuit to recirculate pressure fluid from the outlet side of at least one said motor to the inlet side of at least one said motor and thereby inhibit cavitation at said motors.

Claim 9

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, said speed control valve means being biased to a low-speed position, but selectively movable to a high-speed position, and speed-limiting means operable to maintain said speed control valve means in said low-speed position when the maxi-mum inlet pressure at said motors exceeds a predetermined limit pressure level.

Claim 10

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, said speed control valve means being biased to a low-speed position, but selectively movable to a high-speed position, and speed-limiting means operable to maintain said speed control valve means in said low-speed position when the maxi-mum inlet pressure at said motors exceeds a predetermined limit pressure level.

Claim 11

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, speed-limiting means operable to maintain said speed control valve means in a low-speed position when the maximum inlet pressure at said motors exceeds a predetermined limit pressure level, and selectively operable speed control valve-actuating means for shifting said speed valve means between high-speed and low-speed positions, said speed-limiting means being operable to override said valve-actuating means and maintain said speed valve means in, or shift said speed valve means to, said low-speed position when said limit pressure is exceeded.

Claim 12

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, speed-limiting means operable to maintain said speed control valve means in a low-speed position when the maximum inlet pressure at said motors exceeds a predetermined limit pressure level, and selectively operable speed control valve-actuating means for shifting said speed valve means between high-speed and low-speed positions, said speed-limiting means being operable to override said valve-actuating means and maintain said speed valve means in, or shift said speed valve means to, said low-speed position when said limit pressure is exceeded.

Claim 13

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, speed-limiting means operable to maintain said speed control valve means in a low-speed position when the maximum inlet pressure at said mOtors exceeds a predetermined limit pres-sure level, and anticavitation means operable at a high speed position of said speed valve means to protect said motors from cavitation.

Claim 14

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, speed-limiting means operable to maintain said speed control valve means in a low-speed position when the maximum inlet pressure at said mOtors exceeds a predetermined limit pres-sure level, and anticavitation means operable at a high speed position of said speed valve means to protect said motors from cavitation.

Claim 15

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, and anticavitation means operable in a high-speed position of said speed valve means to provide a regenerative motor subcircuit of said hydraulic circuit and thereby ensure adequate flow to both said motors.

Claim 16

A hydraulic control system for a two-speed winch driven by a pair of hydraulic motors drivingly connected to a common drive transmission, said system comprising: a hydraulic fluid circuit interconnecting a pump means and said motors and including selectively operable directional control valve means and speed control valve means, and anticavitation means operable in a high-speed position of said speed valve means to provide a regenerative motor subcircuit of said hydraulic circuit and thereby ensure adequate flow to both said motors.