Caterpillar Tractor Co.

Caterpillar Inc.

Joseph E Dezelan

Cullen P Hart

Carroll R Cole

Gene B Easterling

David S Vinton

John J Campbell

Donald R Mast

Stephen J Tlachac

John A Campbell

Henry J Jessen

Quick drop valves are useful in directing fluid expelled from a contracting chamber of a hydraulic actuator to its expanding chamber under gravity load conditions. The present electro-hydraulic quick drop circuit improves the efficiency of the quick drop valve by energizing a solenoid valve to direct load generated pressure from the rod end chamber of the hydraulic actuators to an end of a quick drop valve for moving the quick drop valve to the quick drop position when a control valve is at or between a preselected intermediate operating position and its fully open position. The quick drop valve is moved to the quick drop position immediately upon the control valve reaching the preselected operating position so that the fluid expelled from the rod end chamber is directed to the head end chamber almost immediately after the blade begins to freefall. Also the quick drop valve totally blocks the rod end chambers from the control valve so that all the fluid expelled from the rod end chambers is directed to the head end chambers at the quick drop position of the quick drop valve.

Electro-hydraulic quick drop circuit

A valve assembly (16) for use in a fluid system (10) includes a flow control valve (82) which controls fluid flow between a fluid inlet port (34) and a fluid supply passage (36) in response to the load requirements. A main control spool (96) is selectively movable between a neutral position and first and second actuated positions. A load sensing passage (78) communicates a load signal from an actuator (26) to the spring chamber (50) of the flow control valve (82). A drain passage (80) communicates the load sensing passage (78) with the reservoir (14) when the main control spool (96) is in the neutral position. A blocking mechanism (138) blocks the load sensing passage (78) when the main control spool (96) is in the neutral position and opens one of the inlet port (34) and the supply passage (36) to the spring chamber (50) so that the flow control spool (82) is held in an open position. Upon moving the main control spool (96) to one of its actuated positions, the drain passage is blocked from the reservoir (14) and a load pressure signal in the load sensing passage (78) moves the blocking mechanism from the blocking position to an open position and simultaneously closes the communication between the spring chamber (50) and one of the inlet port (34) and supply passage (36). This arrangement provides a system in which the actuator (26) responds more rapidly upon the main valve spool being moved to an actuated position since communication between the inlet port and supply passage is initially unrestricted.

Flow control valve assembly wth quick response

Load sensing steering

Selectively actuatable fluid control system for a work element

Variable displacement front wheel drive system

An improved emergency system (10) for a vehicle having a closed center steering valve (12), a pump (14) normally supplying fluid to the valve, and an accumulator (16) for supplying emergency pressurized fluid to the valve when the pump fails. The improvement is a flow directing circuit (18) connecting the accumulator to the valve in parallel relationship to the pump and apparatus for blocking flow from the accumulator to the valve responsive to proper operation of the pump. Adequate emergency steering is provided to a closed center steering valve system by the above arrangement.

Closed center emergency steering with accumulator source

A vehicle drive system including a rotary output, variable displacement, hydraulic motor (22) adapted to drive a wheel or the like, a pump (10) for providing hydraulic fluid under pressure to the motor, a pressure control valve (30) connected to the motor for regulating the displacement thereof to achieve a desired system pressure and having a pressure responsive surface (34) receiving a signal representative of system pressure and a biasing spring (36) acting in opposition thereto. The invention contemplates the improvement wherein a variable, settable, pressure reducing device (60,106) is connected to the pump and to the pressure control valve to apply hydraulic fluid under reduced pressure to the pressure control valve in bucking relation to the system pressure signal.

Torque control of hydraulic motors

A motor displacement control system (10) has a variable displacement drive motor (38), an auxiliary motor (30), a source (12) of fluid under pressure for operating the motors (30, 38), a first valve (50) for controlling the displacement of the drive motor (38) and maintaining at least a first pressure level thereto, and a second valve (98) for controlling the displacement of the drive motor (38) in response to operation of the auxiliary motor (30) at a second pressure level and overriding the first valve (50). The system is particularly useful on a motor grader.

Motor displacement control system

A vehicle drive and work performing system including a rotary output, variable displacement, hydraulic drive motor (22) adapted to drive a vehicle, at least one hydraulic implement motor (14,16 and 18) adapted to power a work performing implement, a hydraulic pump (10) providing hydraulic fluid under pressure to the motors, a flow control valve (12) for controlling the fluid flow from the pump to at least the drive motor, and a pressure control valve (30) for controlling the displacement of the drive motor to achieve a desired fluid pressure level at the drive motor, and including the improvement wherein a load sensor (60,62) is connected to the implement motor for providing a signal representing the load thereon and a piston (54) is responsive to the signal for causing the pressure control valve to change the displacement of the drive motor to thereby change the fluid pressure level thereat to a value different from the desired fluid pressure level.

Load signal control of hydraulic motor displacement

A vehicle drive system including a wheel adapted to at least partially propel a vehicle over underlying terrain and a hydraulic motor coupled to the wheel to drive the same. A flow and pressure compensated pump has an output for providing hydraulic fluid under pressure to the motor and includes a control system having an input for receiving a hydraulic signal and for controlling pressure and flow output characteristics of the pump. A manually settable, pressure reducing valve interconnects the pump output and the control system input to provide a substantially constant, but adjustable, pressure signal to the control system so that output pressure from the pump to the motor may be controlled independently of loading on the motor to set the maximum torque delivery of the motor at a desired value.

Torque limiting control for front wheel drive

A locking mechanism is provided for an apparatus having a first member movable relative to a second member providing a plurality of spaced holes therein including: a housing secured to the first member; a lock pin extendably retractably mounted in the housing for insertion into the holes in the second member; and a powered control circuit having an actuated member movably mounted within the housing and connected to the lock pin, the actuator member providing differential force applying surfaces selectively exerting a predetermined locking force to hold the lock pin in the holes and a lower indexing force permitting substantially unrestricted relative movement between the first and second members and automatic insertion of the pin into one of the aligned holes.

Locking mechanism for movable vehicle members

A multi-range pressure compensated fluid delivery system gives output flow over at least two pressure ranges. The system comprises a prime mover driven variable displacement pump having an inlet from a source of hydraulic fluid and a delivery outlet. A delivery circuit from the output has at least two work circuits selectively connected thereto. A first of the circuits is operable up to a first pressure and a second of the circuits is operable only up to a second lower pressure. An actuator system controls pump displacement responsive to a pressure applied thereto. A system selectively applies a first signal determined by the first pressure to the actuator system to adjust the operating pressure of the pump. A device reduces the first pressure to the second pressure responsive to connection of the second circuit to the delivery circuit to thereby decrease the maximum compensated pressure setting of the pump.

Pump upgrading system

A pilot-operated, spring-centered, directional control valve includes a valve body having a bore, chambers at opposite ends of the bore, a valve spool slidably disposed within the bore, a hollow piston slidably disposed within each of the chambers and biased by springs inwardly toward the spool, and a secondary piston slidably disposed within one of the primary pistons so that pilot pressure directed into the outward ends of the chambers acts on the end of the spool or the end of the secondary piston to selectively operate the valve. The various components of the valve have differing effective cross-sectional areas upon which pilot pressure acts. The control valve is advantageously employed in a hydraulic system controlling front wheel drive in a vehicle.

Responsive pilot-operated control valve for front wheel drive

A motor grader including a main frame mounted on steerable wheels, a drawbar frame mounted on the main frame, a working implement carried by a circle gear rotatably mounted on the drawbar frame and a hydraulic control circuit is described. An improvement in the control of the working implement is disclosed in which continuous downward force is exerted on the circle gear at all times during operation by hydraulic rams. Preferred embodiments of the invention are described wherein the force is exerted by hydraulic means including wear surfaces in contact with the circle gear and wherein the hydraulic control circuit is adapted to provide automatic operation.

Motor grader or the like with hydraulic control system for circle gear

The invention is concerned with an improvement in a hydrostatic auxiliary front wheel drive system for a vehicle which comprises a hydraulic implement pump, a hydraulic implement powered by the pump and motors drivingly connected to a front wheel shaft rotatable in a forward or a reverse direction, the motors being powered via motor conduits by the pump. The improvement of the invention comprises an electrical switch operating responsive to hydraulic pressure developed by the implement pump, the electrical switch a including biasing spring preventing switching thereof into a closed circuit position until the hydraulic pressure reaches a predetermined value and forcing the switch into an unswitched open circuit position when the hydraulic pressure drops below the predetermined value. Also part of the improvement is a valve in the motor conduits providing a pump hydraulic pressure shut-off mode, a forward direction mode leading to forward motion of the vehicle, and a reverse direction mode leading to reverse motion of the vehicle, the valve being constrained in the shut-off mode until the electrical switch switches into said closed circuit position. The improvement yet further comprises directional selection valves for selecting a respective one of the forward direction mode and the reverse direction mode when the switch is switched into the closed circuit position.

Growing community of inventors

Western Springs, IL, United States of America

Joseph E Dezelan