Caterpillar Tractor Co.

Caterpillar Inc.

Larry W Lorimor

John A Junck

Thomas J Hajek

Eugene E Latimer

Daniel T Mather

Srikrishnan T Tolappa

Michael Anthony A'Hearn

Dwight V Stone

Ronald E Tomevi

A fluid system is provided wherein two different fluid circuits are connected in parallel with a single source of pressurized fluid and the two fluid circuits can function together even when one of the loads is lighter than the other. This is accomplished by having the lightly loaded circuit having a directional control that when operated in one of its operative positions the flow from the rod end of the cylinder is directed through the directional control valve and combined with the supply flow being directed to the head end of the cylinder. With the other heavier loaded circuit also being actuated, the pressure of the fluid from the rod end of the fluid cylinder is equalized with the pressure of the heavier loaded circuit. Consequently, the speed of the heavier loaded circuit does not stall or slow down relative to the lightly loaded circuit. In the case of a machine having a bucket used for backdragging, the circuit needs a diverter system that provides protection from the cylinder rod of the fluid cylinderfrom buckling during backdragging while maintaining the ability for pressure equalization when not performing a backdragging operation.

Hydraulic circuit having pressure equalization during regeneration

Fluid systems for controlling clutch engagement of a vehicle drive train normally have modulating pressure relief valves to aid in smooth clutch engagement. It is desired in such systems to ensure that the system pressure is reduced during a shift so that the load piston of the modulating pressure relief valve is fully reset prior to engagement of the vehicle drive train. In this arrangement, a fluid system is provided which has a plurality of clutches. In order to ensure that the load system is fully reset, a load piston reset control mechanism is provided which establishes a path to vent the pressurized fluid from a load piston pressure chamber of a modulating presure relief valve in response to the pressure of the fluid in one of the clutches being below a predetermined pressure level. The load piston reset control mechanism has a valve mechanism for controllably connecting pressurized fluid from the load piston pressure chamber to the reservoir in response to the pressure of the fluid directed to one of the clutches being below the predetermined value. The valve mechanism has a signal control valve therein to maintain the valve mechanism in the vented position for a predetermined period of time in order to ensure the load piston has moved to its full reset position even if the fill pressure to the clutches is to high. With the load piston in the full reset position, smooth engagement of the clutches is obtained.

Load piston reset control mechanism

A lubricating spline joint for providing a viscous damping function includes a first member defining an internal spline, a second member defining an external spline engaged therewith, a seal ring between the members at one end of the splines, and a radially inwardly facing chamber at the other end which is exposed to lubrication fluid. The improvement features an internal barrier for assuring a fixed internal radius R and thus a preselected centrifugal pressure head of the fluid mass in the chamber and about the splines, and a plurality of venting passages located radially outwardly of the radius R for continually exhausting fluid from the splines as a result of centrifugal force so that fresh and/or less aerated fluid is circulated through the splines.

Lubricated spline joint

Series - parallel selector for steering and implement

This invention pertains to a control valve (14) having a double-acting kick-out member (36) attached to an end of a spool (33) thereof to return the spool (33) to a neutral position after actuation thereof. The invention is particularly useful in a fluid control circuit (10) wherein the control valve (14) is adapted to selectively communicate pressurized fluid to an actuator (13), such as a double-acting hydraulic cylinder.

Resettable valve spool with kick-out member

A first control valve of a fluid circuit connecting a first pump to a fluid motor has a signal port in communication with an inlet port when the first control valve is at a selected position at which substantially the total output of the first pump is directed to the motor. A valve device connects a second pump to the fluid circuit in response to a valve spool of the first control valve being moved to said selected position. The valve device has a valve member movable between a first position at which the second pump is in communication with a tank and a second position at which the output of the second pump is combined with the output of the first pump in the fluid circuit. A device moves the valve member to the second position in response to the valve spool of the first control valve being moved to said selected position. The device includes first and second actuation devices associated with the first and second ends of the valve member. The first actuation device has a first preselected area and a first chamber in communication with the first signal port. The second actuation device has a second preselected area greater than the first preselected area of the first actuation device and a second chamber in communication with the signal port.

Dual pump flow combining system

A valve assembly has a housing, a spool positioned in the housing, and a sleeve positioned about the spool. The housing has an inlet and first and second outlets. The spool is movable between a first position at which communication between the inlet and second outlet is blocked and a second position at which the inlet and second outlet are in communication. The spool is movable to the second position in response to the inlet fluid pressure exceeding a preselected value. The sleeve is movable between a first position at which communication between the first outlet and inlet is blocked and a second position at which the inlet communicates with the first outlet. The sleeve substantially maintains the pressurized fluid in the first outlet while in the first position.

Pressure relief and load check valve assembly

A pilot operated valve comprised of a cylindrical grooved spool having axially aligned throttling slots which require alignment with certain ports in an encompassing housing is prevented from rotation in the housing during reciprocation therein by a noncircular tang extending outwardly of the housing and fitted in a specially configured pilot chamber formed in an attached cover.

Valve spool positioner

A control valve arrangement is disclosed for regulating fluid communication between a source of fluid under pressure and a double-acting hydraulic motor, including a housing defining a bore, an inlet chamber in communication with the bore and the pressure source, a pair of service chambers in communication with the bore and the hydraulic motor for actuation thereof, and a plurality of drain passages in communication with the bore, a pressure transmitting circuit defined in the housing and in communication with the bore, a relief valve which is in responsive communication with the pressure transmitting circuit for variably controlling the pressure in the inlet chamber, and a spool reciprocably disposed in the bore of the housing and having a plurality of lands for blocking communication between the inlet chamber and the service chambers in a neutral position, with the spool having metering slots for communicating fluid from the inlet chamber radially outwardly to a selected one of the service chambers and to the motor for operation thereof and for communicating return fluid from the other service chamber radially inwardly to a drain passage in a working position, and with the spool having openings for communicating the pressure transmitting circuit with a drain passage and unloading the relief valve in the neutral position and also for communicating the selected one of the service chambers to the circuit for loading the relief valve in the working position.

Control valve arrangement with a preconditioned relief valve and a flow

In a fluid system having a main control valve and bypass control valve both responsive to pilot pressure for actuation thereof for supplying fluid to a pair of hydraulic actuators and a pair of bypass valves, the pump's flow is supplied to the first actuator and the exhaust therefrom to the second via a third control valve, the exhaust from the second actuator returns via the third control valve and the main control valve to sump, the pump's flow being subjected through the bypass control valve to the first of the bypass valves whereby once a first predetermined pressure has been reached, the pump's flow passes via the bypass valve through the second end of the first actuator and is combined with the exhaust of the first actuator for driving the second actuator.

Tilt tip circuit with bypass valve

A filter assembly comprises a housing having a tubular filter and a bypass valve mounted therein. The valve comprises a spool having pressure modulating means thereon in the form of a tubular extension having a plurality of metering orifices formed therethrough. In normal operation, fluid is communicated from an inlet of the housing, through the filter and to an outlet. When the inlet pressure of the fluid exceeds a predetermined level due to clogging of the filter, for example, the fluid is communicated from the inlet to the outlet directly, through the metering orifices of the valve. The spool has a cylindrical portion which forms a sliding seal with a cylindrical bore defined in the housing to prevent premature opening of the bypass valve.

Filter assembly with modulating bypass valve

A hydraulic control system is disclosed for selectively directing fluid to a pair of reciprocable jacks connectably disposed intermediate a frame and an implement such as a bulldozer blade for tilting and tipping the blade relative to the frame. The control system includes a fluid supply source, a flow divider valve which is in fluid communication with the supply source for providing equal flow to a pair of outlet paths, a first control valve arrangement for selectively communicating fluid from one of the outlet paths to either end of one of the jacks, and a second control valve arrangement for selectively communicating fluid from the other one of the outlet paths to either end of the other one of the jacks.

Implement positioning hydraulic control system

A fluid control circuit for regulating flow from a source of fluid under pressure to a hydraulic motor, including a control valve having a movable spool for communicating fluid entering an inlet chamber from the source with service chambers in communication with the motor, an inlet relief valve selectively pressurizing the inlet chamber in response to spring means and signal fluid received from the service chambers through signal passages. The control valve and its spool are configured to insure that the signal passages are always in positive communication either with one of the service chambers or a drain in order to facilitate manipulation of the spool. The control valve is also adapted to communicate signal fluid to the relief valve prior to communication of either service chamber with the inlet chamber in order to precondition the relief valve and improve response of the motor to manipulation of the control valve.

Proportional control valve with preconditioned inlet modulating relief

A hydraulic circuit comprises a first tank elevated above a second tank and openly communicating therewith by a conduit adapted to continuously maintain the second tank at full capacity with a hydraulic fluid. The hydraulic fluid is pumped out of the second tank and to a work system wherefrom it is recircuited back through a filtering system, retained in the first tank. Upon malfunctioning of the filtering system to prevent the egress of hydraulic fluid therethrough, the increased pressure level of the recircuited hydraulic fluid will function to open a directional control check valve in the second tank to by-pass the conduit normally communicating hydraulic fluid from the first tank to the second tank.

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Joliet, IL, United States of America

Larry W Lorimor