Deere + Company

Eaton Corporation

Douglas M Gage

Stuart Lee Neagle

Warren L Thompson

Donald M Haarstad

The invention is directed to a hydraulic control mechanism for a work vehicle. The work vehicle is provided with a work implement that is operated by a hydraulic actuator. The positioning of the work actuator is controlled by a pilot control system that supplies a pilot control signal to the end caps of a main hydraulic control valve. The mechanism comprises two pressure sensing valves which control the flow of hydraulic fluid from a fixed displacement pump to move the hydraulic actuator, and the flow of hydraulic fluid from a variable displacement pump to hold the hydraulic actuator. The first pressure sensing valve is used to direct fluid from the variable displacement pump to the hydraulic actuator; whereas the second pressure sensing valve is used to decouple one of the end caps of the main hydraulic control valve from the pilot sensing line so that the main hydraulic control valve is shifted to neutral, and blocking the flow of hydraulic fluid from the fixed displacement pump to the hydraulic control actuator.

Hydraulic control mechanism for a hydraulic actuator

A check valve assembly having first and second check valves and an unseating spool is positioned between a control valve and a rotary motor. The unseating spool is elongated so that it continually contacts the valve elements of the check valves. The check valve hydraulically coupled to the higher pressure supply/return line drives the unseating spool against the valve element of the other check valve opening it and connecting the associated supply/return line having lower hydraulic pressure to reservoir through the direction control valve.

Automatic pressure relief system for a hydraulic motor

The present invention is directed to a mechanical hydraulic pressure dampening devices for use in a steering system of an articulated self-propelled work vehicle. The dampening devices are hydraulically positioned between the steering cylinders of the work vehicle and absorb hydraulic pressure spikes in the steering system. In the preferred embodiment, the pressure dampener comprises a pressure accumulator that is fluidly coupled to the steering cylinder by a shuttle check valve. The shuttle check valve shifts in response to a pressure spike so that it can be absorbed by the pressure accumulator. In a second embodiment, the pressure dampener comprises a cylinder having two pistons that are biased into a normal position by a spring extending between the pistons. Spaces are formed on either side of the pistons and are hydraulically coupled to the steering cylinders. A central space formed between the two pistons is hydraulically coupled to a sump return line. Both of the pistons are also provided with restricted orifice having check valves which permit hydraulic fluid to flow out of the central space and into the adjoining outer spaces. A third embodiment of the pressure dampener comprises a cylinder having a single piston which is biased into a normal position by two springs located on either side of the piston. Each of the spaces formed on either side of the piston are hydraulically coupled to one of the steering cylinders.

Hydraulic steering systems dampening devices

The present invention is directed to a hybrid hydraulic system for a work vehicle having both an open center hydraulic circuit and a close center hydraulic circuit. An internal combustion engine drives a fixed displacement pump and a variable displacement pump. The fixed displacement pump provides hydraulic fluid to the open center circuit which directs hydraulic fluid to a steering circuit and the working circuit through a priority valve. The variable displacement pump provides hydraulic fluid to the close center circuit which directs hydraulic fluid to a braking circuit and a pressure reduction circuit. The pressure reduction circuit directs hydraulic fluid to a pilot control system, a clutch cutoff and a differential lock out. Both pumps receive hydraulic fluid from a common sump and a common suction line. The braking circuit comprises two independent braking circuits. Each of the braking circuits include a manually shiftable regulating valve which is hydraulically balanced between its output and the output of the other regulating valve. In this way, the regulating valves are hydraulically interconnected for piloting each other. The pressure reduction system is provided with a first two position solenoid valve which is fluidically positioned between the variable displacement pump and a pressure reducing valve which directs hydraulic fluid to the pilot control system. A working actuator provides an alternate source of hydraulic fluid which is fluidically coupled to the pilot control system when the first solenoid valve is energized. The pressure reduction system houses the first solenoid valve, the pressure reduction valve, and second and third solenoid valves for directing hydraulic fluid to the differential lock out and clutch cutoff, respectively.

Hydraulic system for a work vehicle

The secondary steering system comprises a structure to prevent the reverse flow of fluid in the fluid bypass path around the fluid meter and provide a supply line from the reservoir to the pressurized fluid line. The supply line supplies hydraulic fluid to the fluid meter of the controller when hydraulic pressure has been lost. The fluid meter can then be manually driven by the operator to supply pressurized hydraulic fluid to the steering cylinders.

Secondary hydraulic steering system

The present invention is directed to a hybrid hydraulic system for a work vehicle having both an open center hydraulic circuit and a close center hydraulic circuit. An internal combustion engine drives a fixed displacement pump and a variable displacement pump. The fixed displacement pump provides hydraulic fluid to the open center circuit which directs hydraulic fluid to a steering circuit and the working circuit through a priority valve. The variable displacement pump provides hydraulic fluid to the close center circuit which directs hydraulic fluid to a braking circuit and a pressure reduction circuit. The pressure reduction circuit directs hydraulic fluid to a pilot control system, a clutch cutoff and a differential lock out. Both pumps receive hydraulic fluid from a common sump and a common suction line. The braking circuit comprises two independent braking circuits. Each of the braking circuits include a manually shiftable regulating valve which is hydraulically balanced between its output and the output of the other regulating valve. In this way, the regulating valves are hydraulically interconnected for piloting each other. The pressure reduction system is provided with a first two position solenoid valve which is fluidically positioned between the variable displacement pump and a pressure reducing valve which directs hydraulic fluid to the pilot control system. A working actuator provides an alternate source of hydraulic fluid which is fluidically coupled to the pilot control system when the first solenoid valve is energized. The pressure reduction system houses the first solenoid valve, the pressure reduction valve, and second and third solenoid valves for directing hydraulic fluid to be differential lock out and clutch cutoff, respectively.

A fluid controller (17) is disclosed for controlling the flow of fluid to a steering cylinder (19). The controller includes a fluid meter (51) and a valving arrangement (49) including a valve spool (65) and a sleeve (67). The valving (49) defines a main fluid path including a main variable flow control orifice (121), a variable flow control orifice (123), the fluid meter (51), the steering cylinder (19), and a variable flow control orifice (125). In accordance with the invention, the valving (49) defines a dampening fluid path including a variable dampening orifice (133), the dampening fluid path being in parallel with the main fluid path to dampen pressure spikes in the main fluid path. The size of the variable dampening orifice (133), and the flow therethrough, is a function of the relative displacement between the spool (65) and sleeve (67), whereby the timing and amount of the dampening flow and the relationship thereof to the gain curve of the main fluid path can be selected as desired.

Fluid controller and dampening fluid path

A hydraulic circuit includes as its major constituents a pump supplying hydraulic fluid to a main steering valve and to an auxiliary function valve through a priority valve. The priority valve allows the main steering valve to preempt the auxiliary function valve on demand. A secondary valve is provided to allow an accumulator to discharge hydraulic fluid to the main steering valve should the hydraulic circuit experience a loss of pressure and flow. Electrical circuit means are provided to warn the operator that the hydraulic circuit has lost pressure and flow.

Vehicle steering and auxiliary function hydraulic circuit

A hydraulic fluid power system includes an accumulator which stores a reserve of pressure fluid at pump standby pressure. The charging and discharging of the accumulator is controlled by an emergency steering valve which is operable in response to a predetermined minimum fluid pressure outputted by the steering pump to discharge the stored fluid for emergency steering. The emergency steering valve also has components which serve as a pressure switch which is actuated to complete a circuit through an indicator light whenever the emergency steering valve moves to effect the discharge of the accumulator. The steering valve components are arranged so that premature actuation of the indicator light during pressure drops of short duration are avoided.

Steering system including accumulator for supplying emergency reserve of

A hydraulic fluid power steering system includes an accumulator which stores a reserve of pressure fluid at pump standby pressure. The charging and discharging of the accumulator is controlled by an emergency steering valve which is operable in response to a predetermined minimum fluid pressure outputted by the steering pump to discharge the stored fluid for emergency steering. The emergency steering valve also has components which serve as a pressure switch which is actuated to complete a circuit through an indicator light whenever the emergency steering valve moves to effect the discharge of the accumulator.

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Dubuque, IA, United States of America

Douglas M Gage