Abstract: The use of a pair of small variable displacement hydraulic pumps in a hydraulic system offers some advantages. The output of the two pumps of the known systems is normally not combined, but is selectively combined under a majority of the operating conditions. The subject load sensing hydraulic control system has first and second hydraulic circuits with each circuit having a plurality of pilot operated control valves operatively connected to a variable displacement pump. The output flow of both pumps is normally made available to both hydraulic circuits through a combiner valve so that the output capability of both pumps can be used to satisfy the demand for fluid by a single control valve or by one or more of the control valves from each circuit. A valve arrangement connects the highest load pressure of the control system to both pumps when the output flow thereof is being combined.

Abstract: Described herein is a hydraulic pump control circuit for travelling construction machine, the circuit being of the type including various hydraulic actuators divided into two groups to be driven by first and second pumps, respectively, left and right vehicle drive motors provided in the respective groups, and a change-over valve located on the discharge side of the first and second pumps and switchable to a position for supplying the oil pressure from the second pump in parallel to the left and right vehicle drive motors. According to the invention, the control circuit is provided with a pilot proportioning valve located between a discharge flow rate control regulator for the second pump and a pilot pressure source, and means for applying the pilot pressures acting on left and right vehicle drive valves to pilot ports of the pilot proportioning valve, the proportioning valve being operated by the sum of the pilot pressures applied to the pilot ports to produce a control pressure for the second pump regulator.

Abstract: An operation control device is disclosed. According to a drive command value generated depending on the manipulated amount of a plurality of operating means (11, 12, 13, 14, 15, 16), the operation control device controls the drive amount of actuators (BMS, AMS, BKS, LDM, RDM, TNM) associated with the operated actuator. In the drive amount control, the operation control device changes a ratio of the manipulated amount and the drive amount command value by work accuracy flow rate data (41), weights the drive command values based on the same manipulated values of said operating means by priority mode weight data (42), and/or controls the timing of supply of the drive energy from at least two separate energy sources (FFP, RP) as a drive energy source for the respective actuators, and the supply amount of the drive energy, under control of pump utilization data (43) and pump swash plate control data (44).

Abstract: The invention concerns an automatic control system for the transfer of the drive power between a tractor (10) and a trailer (11), which system comprises a closed hydraulic circuit (43) that operates the drive wheels of the tractor (10) and an open hydraulic circuit (25) that operates the drive wheels (17a,17b) of the trailer. In the system, the closed hydraulic circuit (43) of the tractor (10) includes a pump (15) and a hydraulic motor (16) driven by the pump and, in a corresponding way, the open hydraulic circuit (25) of the trailer (11) comprises a motor or motors (21a,21b) driven by a pump (20). The control system comprises a line (42) that transmits a control pressure (P.sub.2) from the closed circuit (43) of the tractor (10) to the open circuit (25) of the trailer (11). When the resistance to traction increases, e.g. when driving up a steep hill, the pressure (P.sub.2) in the transmitting line (42) increases and, because of this pressure (P.sub.

Abstract: A hydraulic actuator control circuit capable of increasing the flow rate of the working fluid supplied to hydraulic actuators when the load on the hydraulic actuators increases beyond predetermined values includes a first valve group having a plurality of pilot controlled selector valves connected, respectively, to hydraulic actuators, a second valve group having a plurality of pilot controlled selector valves connected, respectively, to lines connecting the hydraulic actuators to the pilot controlled selector valves of the first valve group, two hydraulic pumps connected, respectively, to the first and second valve groups, and a tank for containing working fluid.

Abstract: In a summation power output regulating system for first and second hydrostatic machines (3, 4), having a common drive and comprising at least two hydrostatic transmissions (1, 2), each of the machines (3, 4) having a hydraulic control device (7, 8), wherein the second machine (4) is provided with a hydraulic power output regulator (24) which regulates the pressure acting on the control device (8) in dependence on the power output of the second machine at that time and a control pressure, dependant on the working pressure of the first machine, is transmitted by means of a hydraulic actuator to the power output regulator (24), substantially 100% utilization of the power available is attained with a simple construction and function by providing the first machine (3) with a power output measuring valve (34; 63, 64) which determines the power output at the time and regulates the control pressure (P.sub.3) in dependence on the power output of the first machine.

Abstract: A hydraulic circuit for a construction machine which operates an actuator for working machine simultaneously with an actuator for working element without degrading the operation of the actuator for working machine. The hydraulic circuit comprises a first hydraulic pump, a first directional control valve connected to the first hydraulic pump and controlling an operation of the working machine actuator, a third directional control valve controlling an operation of the working element actuator, a second directional control valve connected to a second hydraulic pump, a first pilot operating device for controlling an operation of the first directional control valve and a second pilot operating device for controlling an operation of the third directional control valve.

Abstract: A hydraulic fluid circuit system is provided for use in a vehicle and having a priority and a second fluid circuit therein. A variable displacement pump is the primary fluid source for the priority circuit, and a fixed displacement pump is the primary fluid source for the second fluid circuit. A demand valve responsive to differential fluid pressure between the priority circuit and the output of the variable displacement pump selectively switches increasing amounts of output from the fixed displacement pump into the priority circuit in proportion to the output of the variable displacement pump. The demand valve includes a three positioned spool valve. The priority circuit may include a hydraulic steering system, and the second fluid circuit may include an implement or accessory circuit.

Abstract: A control system is provided for a hydraulic actuating system having a multi-phase stepping motor with a driver therefor which supplies and controls DC current through each of the motor windings such that no current is induced into the control winding from adjacent windings. The stepping motor precisely controls the rotation of an eccentric cam engaging an actuating plunger which actuates a control valve of the hydraulic actuating system. The driver receives control signals from a computer programmed to calculate, from user input command signals indicative of the desired system condition, and generate those control signals which most quickly achieve a rough approximation of the desired system condition. After this rough approximation is attained, the computer generates new control signals for the driver as a function of feedback signals and/or system component characteristics so as to precisely achieve the desired system condition.

Abstract: A material handling vehicle is provided which includes a lower truck chassis and an upper material handling structure pivotally supported by the lower chassis, all functions of which vehicle are driven by a single engine. The material handling vehicle is controllable from a main truck cab on the truck chassis or from an upper operator's cab mounted on the upper structure. The single engine provides highway travel power and power to all excavator functions, while the vehicle, including remote travel and implement manipulation capabilities, may be controlled from the upper operator cab. The main engine, when used for over the highway travel, powers the driven wheels through a power shift transmission in a conventional manner.

Abstract: A control having a primary work system, a secondary work system, a first fluid flow generating system, and a second fluid flow generating system is provided. A control signal delivering device is provided to deliver a control signal having a magnitude responsive to a relative location of a control valve between a first and second position of a control valve. A control signal receiving device receives the control signal and separately controls the flow rate deliverable from the first and second flow generating system in response to the magnitude of the control signal received. The control signal receiving device has a set point value which is representative of a preselected magnitude of the received control signal. The second fluid flow generating system is controlled to deliver fluid only in response to the magnitude of the received control signal having a value greater than preselected deliverable flow rate.

Abstract: An integrated hydraulic system for use in a construction work vehicle has three hydraulic pumps for supplying hydraulic fluid into a steering mechanism and work implement operating actuators. One of the pumps is a steering pump for supplying through a steering circuit hydraulic fluid into the steering mechanism. Another pump is a work implement pump for selectively supplying hydraulic fluid through a work implement circuit by the interposition of a pilot operated directional control valve into the steering circuit and/or the work implement circuit. Still another pump is an auxiliary pump for selectively supplying hydraulic fluid through an auxiliary circuit by the interposition of the directional control valve into the steering circuit and/or the work implement circuit. The directional control valve is controlled by a pressure differential across a restrictor provided in the steering circuit.

Abstract: A control drive is provided for the drive of a vehicle, whose steering is effected by a differential driving of the drive wheels of the two sides of the vehicle, where the drive wheels of each vehicle side are driven through a hydrostatic drive unit, whose final control element is connected with a servo piston capable of sliding in an operating cylinder and is acted upon from both sides, in which case the servo piston is acted upon from one side for controlling the travel speed and the control pressure determining the travel speed is reduced for effecting a turn on one side of the vehicle for large turning radii, and for smaller turning radii a pressure is additionally built up on the opposite side of the servo piston, the said pressure being derived from the control pressure determining the travel speed on the other side of the vehicle.

Abstract: A hydraulic apparatus for a vehicle having a propulsion engine comprises a control valve, a flow dividing valve, pumps driven by the engine for delivering fluid to the valves, and steering and implement circuit operatively connected to the control and flow dividing valves. The control valve includes plunger provided with orifices having variable degrees of openings and a spool connected to the plunger and the flow dividing valve includes a spool. With the hydraulic apparatus this constructed, fluid having an amount necessary for operating the steering circuit is always fed thereinto by operatively connecting the spools of the control and flow dividing valves and sharing the fluid into the steering and implement circuit by controlling the fluid dividing valve in accordance with pressure difference between the upstream and downstream portions of the orifices in the control valve.

Abstract: A control drive is provided for the drive of a vehicle, whose steering is effected by a differential driving of the drive wheels of the two sides of the vehicle, where the drive wheels of each vehicle side are driven through a hydrostatic drive unit, whose final control element is connected with a servo piston capable of sliding in an operating cylinder and is acted upon from both sides, in which case the servo piston is acted upon from one side for controlling the travel speed and the control pressure determining the travel speed is reduced for effecting a turn on one side of the vehicle for large turning radii, and for smaller turning radii a pressure is additionally built up on the opposite side of the servo piston, the said pressure being derived from the control pressure determining the travel speed on the other side of the vehicle.

Abstract: A control system for a hydraulic circuit including at least first and second variable displacement volume type hydraulic pumps, at least first and second hydraulic actuators driven by the pumps, and valves for controlling hydraulic connections between the pumps and the actuators. The control system includes a device for deciding the order of priority of hydraulic connections between the first actuator and the first and second hydraulic pumps and the order of priority of hydraulic connections between the second pump and the first and second actuators. A first sensor is provided for sensing maximization of the displacement volume of the first pump, sensing that the displacement volume of the second pump has become substantially zero. A device decides target displacement volumes of the first and second pumps based on information supplied at least by the priority order deciding device and first and second sensor.

Abstract: A control system for a hydraulic vehicle having a pair of bidirectional travel motors driven by respective pumps via respective travel valves, and implement actuators, including a swing motor, driven by the pumps via two parallel connections of pilot-operated implement valves. For making possible the straight travel of the vehicle, either forwardly or rearwardly, while any of the implement actuators is being driven by either pump, a straight travel valve is provided for the on-off control of communication between the forward travel ports, and between the rearward travel ports, of the two travel motors. Normally held closed under spring pressure, the straight travel valve is pilot opened by a series connection of two straight travel control valves, which delivers pilot control fluid to the straight travel valve when the travel valves are both hand operated to set the two travel motors into rotation in the same direction.

Abstract: A control system for a hydraulic circuit having at least first and second hydraulic pumps of the variable displacement type, a first hydraulic actuator arranged for hydraulic connection with the first pump through first valve to be driven thereby, and a second hydraulic actuator arranged for selective hydraulic connection with said first and second pumps through second and third valve respectively to be driven thereby.

Abstract: In a hydrostatic auxiliary power steering apparatus, a short-circuit passage of a control valve establishes a restricted flow path from a pump pressure line to a reservoir return line in the neutral position of the control valve wherein all other flow paths are blocked. A fixed flow restrictor in the pump pressure line conducts a continuous flow from one of two pumps connected to the pressure line for regulation of the fluid power steering circuit by the pressure drop across the flow restrictor. If one of the pumps is of the variable volume type, the pressure downstream of the flow restrictor is utilized to regulate pump flow adjustment. If fluid under operating pressure is supplied to both the fluid power steering circuit and another fluid operating circuit, a flow dividing valve controlled by the pressure differential across the flow restrictor distributes pressurized fluid between the two fluid circuits.

Abstract: The known swash plate type oil hydraulic piston pump is improved in that three delivery slots each extending over an angular distance of about 60.degree. are formed in a valve plate along one circumference concentric with a rotary cylinder block at an angular interval of 60.degree. and the number of piston-cylinder units provided in the cylinder block is chosen to be a multiple of 6. Pressurized oil delivered through a center delivery slot is fed to one hydraulic actuator, and pressurized oil delivered through the delivery slots on the opposite sides of the center delivery slot is jointly fed to the other hydraulic actuator, whereby variations of flow rates of the pressurized oil fed to the respective hydraulic actuators can be minimized.

Abstract: An electrohydraulic control system which includes first and second electrically controlled fully variable hydraulic pumps adapted to be driven by the vehicle engine. In the specific embodiment of the invention herein disclosed, the first pump is coupled to the steering and braking control valves, and the second pump is coupled to the bucket and hoist control valves. An electrically controlled poppet valve selectively interconnects the respective pump outputs. Operator-responsive controllers, namely a bucket/hoist joy-stick controller, a vehicle propulsion controller and a steering controller, provide associated electrical signals as respective functions of operator demand. Electrically operated valves control application of hydraulic fluid to the bucket and hoist drive mechanisms, and pressure and position sensors are connected to such valves and actuating mechanisms.

Abstract: There is disclosed a hydraulic circuit system for use in a swivel type excavator. The circuit system having a plurality of variable displacement pumps for supplying pressurized fluid for manipulations of work implements and swivel means of the excavator, and control means operative to automatically adjust pump displacement to the output hosepower of a prime mover driving the pumps. The control means includes hydraulic pressure detector means, servo-control means respectively provided in the pumps, negative control valves for respectively controlling the servo-control means by the action of the pressure detector means, cut off valves respectively connected in series with the negative control valves, and summing valves respectively connected in series with some of the cut off valves so as to control pressurized fluid to be supplied into the servo-control means by the action of the fluid pressure delivered from the pumps.

Abstract: A control system for controlling the movement of the slide of a hydraulic press of the type having a main cylinder containing a piston mounting the slide. The control system comprises an electronic processor, a pressure transducer to measure the pressure of hydraulic fluid applied to the piston to move the slide downwardly, a position encoder coupled to the slide to determine the vertical position of the slide, and a hydraulic circuit to supply hydraulic fluid under pressure to the cylinder to move the piston and slide upwardly and downwardly. The hydraulic circuit comprises a plurality of cartridge valves having controls actuable by outputs from the processor.

Abstract: A control system has two fixed-displacement pumps for supplying pressurized fluid to a pair of steering cylinders via a steering valve and to a pair of implement cylinders via an implement valve. Connected next to the pumps is a demand valve which is pilot operated to deliver to the steering cylinder pair the pressurized fluid from only one pump upon slight displacement of the steering valve and the pressurized fluid from both pumps upon greater displacement of the steering valve. The demand valve is further pilot operated to deliver to the implement cylinder pair the pressurized fluid from only one pump when the implement valve is actuated in a direction to lower the implement assembly, and the pressurized fluid from both pumps when the implement valve is actuated in a direction to raise the implement assembly.

Abstract: A quick changeover hydraulic circuit for use in an auger drive mode or percussion hammer mode, controllable in each mode by the same flow regulator. The circuit comprises a first branch circuit which powers a first auxiliary hydraulic powered device and a hydraulic motor for drill steel rotation. A second branch circuit powers a hydraulic percussion motor for a drill steel hammer or a rotary hydraulic motor for an auger, only one of which is in the circuit at one time. An interbranch circuit comprises a priority flow divider which distributes flow. In a first mode with the percussion motor for the drill steel hammer connected into the second branch the flow is delivered to the steel rotation motor and the first auxiliary device. In a second mode with the auger motor connected into the second branch, combined flow from both branches is delivered to the auger motor.

Abstract: The control valving for a dual pump hydraulic system has two regulator valves which control the distribution of pressurized fluid, on a priority basis, to a high pressure system, a low pressure system and a lube system. One regulator valve controls flow from both pumps to the high and low pressure systems. The other regulator valve controls flow from one pump to the lube system and bypasses excess flow from the other pump to the system reservoir. The first regulator valve satisfies the high pressure system requirements before any fluid is directed to the low pressure system. The other regulator valve receives fluid downstream of the first regulator valve and satisfies the low pressure system before any fluid is directed to the lube system or to the fluid return passage to the reservoir.

Abstract: A jacking mechanism for jacking a well casing or other well pipe vertically, and including a hydraulic control system in which a reversible variable displacement pump acts in one condition to deliver pressure fluid in parallel with another pump to the lower end of a jacking cylinder to actuate the piston thereof upwardly, with fluid discharging from the upper end of the cylinder to the variable displacement pump and being metered therethrough to regulate the rate of upward movement of the piston. In a second condition of the apparatus, flow through the variable displacement pump is reversed to lower the piston, and a variable restriction valve regulates discharge of fluid from the lower end of the cylinder to act with the variable displacement pump in regulating downward movement of the piston and supported pipe.

Abstract: All but the circle drive motor of the implement actuators of a motor grader are divided into two groups each consisting of those which need not be operated simultaneously. The power system has three fixed displacement pumps for driving the circle drive motor via a circle control valve and the two implement actuator groups via respective implement control valve arrangements of carry-over parallel configurations. One of the pumps is connected to the two implement control valve arrangements via a restriction and a flow divider. A first demand valve controls communication between the other two pumps and the implement control valve arrangements in response to the pressure differential across the restriction, maintaining constant fluid flow to the valve arrangements regardless of engine speed or the loads on the implement actuators.

Abstract: A hydrostatic drive system consisting of at least two component systems is provided, each component consisting of an adjustable pump, where the loading of the pump adjusting cylinder is regulated by a hydraulically controlled servo control valve, one side of which is acted upon by the delivery pressure of the associated pump and the other side is acted upon through a control pressure line by pressure beyond the metering restrictor, the improvement comprising a coupling valve to which all delivery lines and all the control pressure lines are connected, each through a branch connection line wherein the said valve in the closed position shuts off all the branch connection lines and in the open position connects all the delivery lines together and all the control pressure lines together and is hydraulically controlled, a first pressure chamber on one side of said valve to which each delivery line is connected, a valve element in said pressure chamber being loaded with a pretensioned spring on said first chamber,

Abstract: A control is provided for the drive of a motor vehicle with differential-speed steering and with a hydrostatic power transmission unit on each side of the vehicle, where the adjusting element of each of the two power transmission units is provided with a spring-loaded adjusting piston that can be acted upon by control pressure, in which case two pairs of control pressure pick-offs are provided, of which two are assigned to forward and backward movement and the other two are assigned to cornering, where a pressure-dependent switchable pilot valve is installed in the connecting line between a control pressure pick-off assigned to a cornering direction and the adjusting element of the assigned power transmission unit, the pilot valve connects this control pressure pick-off assigned to the cornering direction with a specific pressure chamber of the adjusting element of the power transmission unit on the side of the vehicle on the inside of the curve, so that through actuation of the control pressure pick-off dete

Abstract: A fluid control system (10) has a first fluid pump (12) for supplying pressurized fluid in interrupted series to first and second work elements (14,16). The first work element (14) in the series has priority which prevents simultaneous full power operation of the first and second work elements (14,16). A second fluid pump (24) is capable of supplying pressurized fluid to the second work element (16) only upon receiving a signal indicating that pressurized fluid from the first pump (12) is being directed to the first work element (14). The subject fluid control system (10) is especially useful with a tree harvesting machine where it is beneficial to propel the machine and at the same time rotate the upper structure.

Abstract: A hydraulic interlock system is disclosed wherein several pumps may be used to activate a plurality of hydraulic circuits while preventing activation of a single hydraulic circuit by more than one pump simultaneously.

Abstract: A hydraulic fluid drive for a land motor vehicle having front and rear drive wheels. An internal combustion engine drives a pair of positive displacement pumps. A first pump is connected to hydraulic motors that drive the front wheels of the vehicle. A second pump is connected to a hydraulic motor that drives a rear steerable wheel of the vehicle. A manually operated control is used to adjust the speed and torque of the motors for the front wheels. A front and rear wheel drive equalizing control operates in response to differences in hydraulic fluid pressure supplied to the front and rear hydraulic motors to equalize the fluid pressure pumped to the front and rear hydraulic motors so as to maintain the torque and speed of the front and rear wheels substantially constant. A foot operated lever is used to operate the control for the first pump for changing the supply of fluid pressure to the front wheel motors.

Abstract: A drive system for construction machinery in which hydraulic circuit is provided with a plurality of variable-displacement hydraulic pumps and a plurality of hydraulic actuators, each pump being connected in closed circuit to one or a plurality of the actuators via a solenoid-operated valve or valves to drive a movable member or members connected to the actuator or respective actuators when pressurized fluid is supplied to the actuator or actuators from the pump. At least one of the selected hydraulic actuators is further connected in closed circuit through a solenoid-operated valve to at least one of the hydraulic pumps other than the hydraulic pump which is connected in closed circuit to the hydraulic actuator. The hydraulic circuit means is controlled such that timing for switching the solenoid-operated valves is controlled in conjunction with the operation of the pump so as to absorb the shock which would otherwise be produced when each actuator is rendered operative and inoperative.

Abstract: A fluid motor control system (11) assures that automatic changes of motor displacement, which are initiated by occurrence of a predetermined operational condition in the system (11), result in a change of motor speed of the desired magnitude. Flow adjustment elements (76) respond to a displacement increase by reducing the flow of working fluid available to the motor or motors (12, 13) and respond to a motor displacement reduction by increasing the available flow. In one specific form, the system (11) controls a pair of right and left side vehicle drive motors (12, 13) and automatically increases motor displacements while reducing the fluid flow supplied to the motors (12, 13) to reduce travel speed during a turn of travel direction.

Abstract: Conditional exchanging of working fluid between plural fluid circuits (13A, 13B) having separate supply pumps (18A, 18B) is provided for without continuously bleeding fluid from the pump control pressure lines (21A, 21B). Each circuit (13A, 13B) has a pump control (19A, 19B) responsive to a control pressure, a plurality of fluid motors (14A, 15A, 16A, 14B, 15B, 16B), and a group of resolver valves (38A, 38B) which compare motor pressures and intercommunicate the pump control (19A, 19B) with the most highly pressurized motor (14A, 15A, 16A, 14B, 15B, 16B). At times when fluid from one circuit (13A, 13B) is being delivered to a motor (16A, 16B) of another circuit (13A, 13B), the pressure comparing function of the resolver group (38A, 38B) of the one circuit (13A, 13 B) is extended to include the motor (16A, 16B) of the other circuit (13A, 13B). Among other uses, the system (11) may be used on excavator vehicles having plural fluid motors performing a variety of different functions.

Abstract: A system is disclosed for controlling the flow of fluid from a pair of pumps (15,15') to a steering system (11) and a pair of auxiliary load circuits (13,13'). The steering system includes valving (43) defining a variable flow control orifice (45), and the steering system normally operates with a pressure differential X across the variable orifice, and provides load pressure signals (47,49,49',53,53') representative of demand for fluid by the steering system. Fluid flow from the pumps is controlled by a pair of priority flow control valves (21,21') including a pair of valve members (27,27') each of which is biased by a spring (29,29') toward a position permitting flow to the steering system. The spring (29) exerts a biasing force equivalent to the pressure differential X while the spring (29') exerts a biasing force equivalent to a pressure differential Y, which is less than X.

Abstract: The displacement controllers of a first variable displacement pump supplying fluid for hoe and travel functions of an excavator and a second pump supplying fluid for the excavator house swing function are connected to shuttle valves which operate to couple to the controllers the lesser of the power beyond fluid pressures emanating from travel function and swing function control valves. A bypass circuit is arranged to couple power beyond flow from the swing function control valve to join the flow being outputed from the first pump when the pressure of the last-named power beyond flow exceeds the lesser of that emanating from the travel control functions. Lead compensators are provided to make the controllers more responsive to circuit demands and a power limiting valve is provided for automatically connecting pressure for destroking the pumps to relieve engine load when the engine speed falls to a predetermined minimum.

Abstract: A vehicle vacuum power system which insures sufficient vacuum power to operate a vacuum brake booster and a vacuum operated road speed control system. Because of the low vacuum, high flow rate needs of a cruise control system, the cruise control is connected directly to the engine manifold through a check valve. A small orifice from the vacuum pump in parallel with engine manifold vacuum provides sufficient vacuum for the cruise control when the manifold vacuum is not sufficient. The vacuum pump is in series with manifold vacuum and is operated in response to a pressure switch which allows the pump to run only when brake booster vacuum is low. Manifold vacuum is sufficient most of the time, but the orifice to the cruise control tends to cause a fast loss of brake booster vacuum, causing the vacuum pump to run when it is not actually needed. The vacuum regulator shuts off the flow through the orifice when it is not needed, considerably reducing the pump operational time.

Abstract: A power drive unit for operation of structure in opposite directions, such as aircraft structure and, particularly, thrust reverser structure of an aircraft engine operable between stow and deploy positions, including, a bi-directional hydraulic motor having a variably positionable wobbler for controlling displacement of the motor. Control structure includes a valve for causing fluid flow through the motor in either of two directions, a control cylinder and piston connected to the wobbler for setting the motor at either minimum or maximum displacement conditions or at any condition therebetween, a servo valve operable for setting the position of the piston in the control cylinder, and a differential area piston operatively connected to the servo valve for positioning thereof and responsive to the pressure drop across the motor in either direction of operation thereof to set the motor displacement at the least value possible for the load condition on the motor.

Abstract: A control and actuator system for a press brake having a frame, a bed, a ram, and a pair of hydraulic cylinders for reciprocating the ram, utilizes a jackscrew arrangement in conjunction with positive mechanical stops on the ram pistons to support the ram beneath the cylinders to enable the bottom travel limit of the ram to be preset. The top travel limit of the ram is preset by means of vertically adjustable actuator rods on the ram, which engage actuator stems on valves associated with each cylinder to stop upward travel and hold the ram in position. Tilt compensation is provided at the top and bottom ram limits by independent adjustment of the jackscrews and actuator rods, obviating the need for a complex tape and pulley driven differential valve arrangement. The novel hydraulic circuit provided for powering the cylinders utilizes pilot-driven control valves, and provides for direct venting of the system high-volume hydraulic pump when not in use to maximize system efficiency.

Abstract: A hydraulic follow-up for use with a hydraulic system placed between a rotating input member and a rotating output member. The hydraulic system is a hydrostatic transmission for driving a tractor, and comprises a hydrostatic pump and a hydrostatic motor driven by the pump. When the hydrostatic pump is angularly shifted with respect to the input member, the shifting is controlled by the hydraulic follow-up, which also shifts the motor in relation to the output member.

Abstract: A two-axle, four-wheel-drive vehicle has separate hydraulic drive systems to drive the front and rear pairs of traction wheels. Each drive system includes a hydraulic motor that is powered by its own variable displacement pump. The torque developed by the motors, and the hydrostatic drive pressure, depend on the volume of fluid flow from the pumps. Under certain conditions, the hydrostatic drive pressure to the two motors becomes unbalanced. A torque equalizer valve is interconnected between the two hydraulic drive systems. When the equalizer valve senses a hydrostatic drive pressure difference between the two drive systems, it readjusts the displacement of the pump having the higher pressure by lowering the hydrostatic pilot pressure to restore the balance of hydrostatic drive pressures.

Abstract: A fluid control system for a mobile aerial tower which includes a plurality of positioning elements such as first and second interconnected booms and a turntable for rotating the booms about a vertical axis. The control system comprises first and second variable speed pumps and a bank of three double acting valves operatively connected between the pumps and the positioning elements so as to control the direction of fluid flow thereto, and a pneumatically linked remote control system for selectively controlling the speeds at which the pumps operate and for selectively operating the valves to direct fluid between either of the pumps and any one of the positioning elements, or alternatively between both of the pumps respectively and any two of the positioning elements, or alternatively between the pumps collectively and any one of the positioning elements.

Abstract: A control system for plural circuits having motor-driven hydraulic pumps. As disclosed, a pair of pumps is connected in a hydraulic actuating circuit individual to that pair and the circuit includes an hydraulically operated actuator to be advanced and retracted by fluid under pressure delivered from the pair of pumps of that circuit. A single prime mover drives the pair of pumps and pumps in other circuits, and each circuit has a pressure-responsive control valve which provides for unloading a pump of the first circuit in response to increases in pressure in the various other circuits to a predetermined value at which, in the absence of such unloading, the input horsepower requirement has risen toward a value which would stall the prime mover.Pumps in several of the circuits may be sequentially and selectively unloaded.

Abstract: A dual pump hydraulic control system with a predetermined flow crossover provision is disclosed including a first hydraulic control circuit having a first source of fluid pressure, a first motor, a first distributor valve in communication with the first source and moveable into an actuating condition for directing fluid to the first motor, a second motor, a second distributor valve in interrupted series communication with the first distributor valve and moveable into an actuating condition for directing fluid to the second motor; a second hydraulic control circuit having a second source of fluid pressure, a third motor, a third distributor valve in communication with the second source for directing fluid to the third motor; and a crossover valve and resolver network responsive to the actuating condition of the first distributor valve and to the actuating condition of the second distributor valve for communicating fluid from the second source to the second motor to supplement fluid from the first source to the

Abstract: A fluid system has a plurality of pumps, left and right track motors and a plurality of work elements. First elements are provided for controllably delivering fluid from a first plurality of pumps to the left track motor and for controllably bypassing the left track motor and delivering fluid from at least one of the first plurality of pumps to a separate respective work element. Second elements are provided for controllably delivering fluid from a different plurality of said pumps to the right track motor and for controllably bypassing the right track motor and delivering fluid from at least one of the second plurality of pumps to a separate respective work element.

Abstract: A system for providing pressurized fluid to a primary load circuit and an auxiliary load circuit, the primary load circuit being of the type which provides a load pressure signal representative of the demand for fluid in the primary load circuit. The system includes first and second fluid pumps feeding first and second priority flow control valves, respectively, each of which has a primary outlet port connected to the primary load circuit and an auxiliary outlet port connected to the auxiliary load circuit. When the flow demand of the primary load circuit can be satisfied by the first pump, any excess flow available is fed by the first flow control valve to the auxiliary load circuit, and all of the flow from the second pump goes to the auxiliary circuit.

Abstract: A hydraulic circuit for a tree harvesting implement having a cutter mounted on a movable frame with a hydraulic ram moving the frame and a hydraulic motor driving the cutter is disclosed herein. The hydraulic circuit includes two separate pressurized fluid sources with one source connected to one end of the fluid ram and the second source connected to the hydraulic motor as well as the opposite end of the fluid ram with both conduit means having pressure relief valves that are settable so that the frame is moved as a function of the resistance encountered by the cutter and/or the movable frame.

Abstract: A hydraulic circuit is provided for powering and controlling an excavator or the like, with a plurality of pumps supplying pressurized fluid for the circuit. The circuit is arranged so that fluid is provided in a manner to permit positive independent control of the various implement motors of the machine, with means provided so that fluid may also be combined to operate selected implement motors for faster operation and maximum efficiency of the machine.