Abstract: A method of providing variable pumping rate from a piston type pump at a constant drive speed, comprising providing a connecting rod connected to the throw of a crankshaft on one end and to a connecting pin on the other end, constraining said connecting pin to move reciprocally generally in a first direction when said crankshaft rotates, a piston connected to said connecting pin which is mounted in a head and moves reciprocally in a second direction, and varying the angle between said first direction and said second direction to vary the volume being pumped by said pump.

Abstract: A variable capacity rotary compressor, which precisely controls variation of a compression capability into a desired discharge pressure, and which minimizes a resistance to rotation of a rotating shaft, and thus improves the capacity of the rotary compressor.

Abstract: The invention provides a volume control apparatus of a radial pump or motor which downsizes a hydraulic pump or motor, reduces a weight thereof and improves a freedom in arrangement, and a positioning apparatus. Accordingly, a servo piston (8) is operated following to a control valve (9), presses a cam ring (2) so as to position the cam ring at a position in correspondence to a volume control pressure, and regulates a volume.

Abstract: A metering valve arrangement comprises a metering valve member which is angularly adjustable within a metering valve bore provided in a metering valve housing and an adjustment arrangement for adjusting the axial position of the metering valve member within the metering valve bore. The metering valve arrangement includes a first opening provided in the metering valve member which is registerable with a first outlet provided in the metering valve housing to control a first rate of flow of fluid through the first outlet depending on the angular position of the metering valve member within the bore, and a second opening provided in the metering valve member which is registerable with a second outlet provided in the metering valve housing to control a second rate of flow of fluid through the second outlet.

Abstract: A method for controlling a hybrid compressor system is disclosed. The hybrid compressor system includes a variable displacement hybrid compressor that is selectively driven by one of an engine and an electric motor to cool a passenger compartment of a vehicle. The method includes the steps of transmitting a demand signal to activate an electric motor drive mode of the hybrid compressor system, whereby the electric motor drives the hybrid compressor, transmitting a compressor displacement signal to the hybrid compressor to set a displacement of the compressor to a minimum level, waiting a predefined time period, activating the electric motor to drive the compressor, determining a suction pressure of a suction chamber of the hybrid compressor, determining whether the displacement of the hybrid compressor is sufficient based on the suction pressure determination, and changing the displacement of the compressor if the displacement is insufficient.

Abstract: A variable displacement hydraulic power unit has a housing and a rotating piston block with a rotatable axis and a servo piston bore having a reciprocal piston therein with the bore extending in a direction parallel to the rotatable axis of the rotating piston block. The housing and servo piston each have adjacent open ends. A single integral cover is attached to the housing to cover close and close the open ends of both the housing and the piston bore.

Abstract: A device for supplying liquids, particularly fuel, has a first drive shaft (32) and a supply pump (30) having at least one supply member (40) coupled to a second drive shaft (36), whereby the first drive shaft (32) drives the second drive shaft (36) via a drive unit (60). The drive unit (60) is preferably a tapered ring drive, which has a first frictional bevel gear (62) connected to the first drive shaft (32) and a second frictional bevel gear (64) connected to the second drive shaft (36), whereby the first and second friction bevel gears (62, 64) roll off one another by a tapered ring (66) disposed between the two bevel gears. The tapered ring (66) is movable for changing the gear ratio of the gear unit (60) as a function of the supply pressure produced by the supply pump (30). In this manner, with a lower supply pressure, a large gear ratio of the gear unit (60) is determined, and with an increased supply pressure, a smaller gear ratio of the gear unit (60) is determined.

Abstract: A hydrostatic axial piston machine employs a swash plate construction in which the diagonal position of the swash plate can be controlled by at least one positioning piston pressurized with a control pressure. A control valve is in a line which leads to at least one positioning piston. A simple electrical-hydraulic control of the swash plate can be accomplished by the electrical actuation of the control valve. The control valve may be in the form of a rotary disk valve which can be actuated by a stepper motor.

Abstract: A fuel pump comprises a pumping plunger reciprocable within a plunger bore under the action of a cam drive arrangement. The cam drive arrangement comprises first and second surfaces defining therebetween a chamber, the volume of which can be controlled to control the spacing of the first and second surfaces so as to permit control of the axial length of the cam drive arrangement. The first surface may be defined by a tappet member which acts to transmit a force from the cam drive arrangement to the pumping plunger, the second surface being defined by a piston member which is slidable within a tappet bore formed in the tappet member. The invention also relates to an arrangement for use in a fuel pump comprising a pumping plunger which is reciprocable within a plunger bore under the action of a drive arrangement and a tappet member which is slidable within a further bore provided in a housing for transmitting a force from the drive arrangement to the pumping plunger.

Abstract: A piston pump with a piston in a pump chamber has, for controlling an inlet and an outlet of the pump chamber, in a partial region of its peripheral surface, a recess that can be aligned, by a rotational movement about its longitudinal axis, with the inlet or the outlet. By means of a stroke cam gear, the piston can be caused to carry out a lifting motion within the pump chamber. The stroke cam gear is formed by a peripheral guiding path of an adjusting element, which can be swiveled about a stationary axis of rotation, and a radial projection at the piston, which engages this guiding path.

Abstract: A hydraulic brake system for preventing wheel lock. The hydraulic brake system includes a variable displacement rotary pump that is activated by the rotation of an axle of a vehicle. A hydraulic control cylinder of the variable displacement rotary pump is operationally coupled to a master cylinder and a displacement piston of the hydraulic control cylinder is operationally coupled to a swash plate of the variable displacement rotary pump for manipulating an amount of brake fluid flowing from the variable displacement rotary pump to a wheel brake cylinder. An outlet port of the variable displacement rotary pump is operationally coupled to the wheel brake cylinder by a section of brake line and to a fluid reservoir through a throttle valve. An inlet port of the variable displacement rotary pump is operationally coupled to a reservoir outlet port by a section of brake line. The wheel brake cylinder is coupled to the wheel of the vehicle to slow down the vehicle when the wheel brake cylinder is activated.

Abstract: A fluid dispense system having a computer control system that operatively controls a stepper motor driving a nutating pump. The stepper motor actuates the nutating pump piston through partial revolutions. The computer control system determines the number of stepper motor steps required to pump a desired amount of fluid by the nutating pump by rotating the piston through segments which are less than a full revolution.

Abstract: A apparatus for gearless shifting, includes at least one crank, and an arm assembly, coupled to the at least one crank, for telescoping to adjust a length of the at least one crank, to selectively and controllably adjust a stroke length of the at least one crank. A pump also is provided including a variable-stroke length apparatus.

Abstract: A pump enable system includes a variable-displacement piston pump having a displacement control device. The displacement control device controls displacement of pistons in the pump based on a position thereof, and a position control system in the pump controls a position of the displacement control device based on a load on the pump. An over-ride system selectively over-rides the position control system such that the displacement control device assumes a position which reduces displacement of the pistons in the pump.

Abstract: A gear pump for metering resins is provided having the surfaces of interacting internal metal parts coated with a metal-based material to prevent seizing of the interacting moving parts as a result of resin curing therebetween. Parts made from such materials as heat treated carbon steel and stainless steel are preferably coated with a nitride, carbide or oxide of such metals as tungsten, titanium, aluminum and chromium at a thickness of between about 2-5 microns. The coating is applied to the surface of any part that comes in heated contact with the surface of another relatively moving part. The resulting gear pump exhibits high wear resistance, longevity, and low maintenance requirements.

Abstract: A device for varying the displacement of a variable displacement bent axis unit includes a one-piece yoke having a bucket portion adapted to carry a cylinder block kit of the bent axis unit, a trunnion bearing portion for swing control on one side of the bucket portion, and a trunnion portion for fluid porting on the other side of the bucket portion. The bucket portion has a bottom wall, a continuous side wall, and an open top. Inside the yoke is a pair of fluid passages intersecting the interior of the bucket portion and extending separately and entirely within the bottom wall and the side wall before opening onto the trunnion portion for fluid porting.

Abstract: An advance arrangement is described including an advance piston slidable within a bore and defining, with the bore, a control chamber. A restricted passage permits fluid to escape from the control chamber at a controlled rate. A pump supplies fluid to the control chamber, the rate at which fluid is supplied to the control chamber relative to that at which the fluid can escape controlling the position of the advance piston. The pump is independent of a feed pump used to supply fuel to the high pressure pump with which the advance arrangement is used.

Abstract: A multi-pump controlling means and method controls and drives two or more reciprocating pumps creating proportioned flows of fluids. The multi-pump controlling means in use is situated between a driving means, such as a double acting ram, and the pumps. The multi-pump controlling means includes two or more cams that each interact with a cam follower attached to the pumps. The cams may be set or adjusted to different gradients, meaning the cam followers following those gradients when the multi-pump controlling means is reciprocated by the driving means, will have different path lengths. The path lengths of the cam followers control the stroke lengths of the respective pumps and thus the volume of fluid pumped by each of the respective pumps.

Abstract: A preferred constant horsepower, variable volume hydraulic pump (10) includes a wobble plate (22) coupled with interior end of the pump drive shaft (18) configured for sequentially stroking a plurality of pistons (28,30) received in respective cylinders (42,44) included as part of a nonrotatable barrel (24). A shifting mechanism (74) axially shifts the barrel (24) in accordance with the output pressure in order to change the stroke length of the pistons (28,30) in the cylinders (42,44) and thereby change the flow rate through the pump (10). The shifting mechanism (74) is configured to lower the flow rate as the output pressure increases in order to maintain a constant horsepower demand for maximizing the flow volume for a given horsepower.

Abstract: A hydrostatic axial piston machine employs a swash plate construction in which the diagonal position of the swash plate can be controlled by at least one positioning piston pressurized with a control pressure. A control valve is in a line which leads to at least one positioning piston. A simple electrical-hydraulic control of the swash plate can be accomplished by the electrical actuation of the control valve. The control valve may be in the form of a rotary disk valve which can be actuated by a stepper motor.

Abstract: Apparatus for sequentially dispensing flowable materials including a positive displacement metering-pump operated by an actuator capable of reciprocating pivotal movement within a range having an angular extent less than 180.degree.. A link member connects the pivotal actuator to the plunger of the positive displacement pump for causing the pump to dispense liquid when the pump actuator is operated. The pump stroke adjuster can selectively vary the distance between the link member and the pivot axis of the pump actuator for, in turn, controlling the stroke of the pump.

Abstract: A system is provided for closed-loop control of a plurality of metering pumps driven by a single source of pressurized fluid. Feedback signals are generated that are proportional to output flow rate from each metering pump, such as velocity of a movable element of the pump with respect to a stationary element. Flow control valves are coupled between the source of pressurized fluid and the metering pumps. A controller receives the feedback signals and regulates flow from the flow control valves to each metering pump to maintain a desired level of output flow. The source of pressurized fluid may include a pressure compensated positive displacement pump having a maximum output flow rate at least equal to the anticipated combined flow rate of drive sections of the metering pumps.

Abstract: A fluid power pumping apparatus having a control system for limiting the power loading thereon to the power available from a motor (172) driving the apparatus, includes a variable displacement rotating piston pump (170). A compensating valve assembly (174) of a type known in the prior art is mounting on the pump. The compensating valve controls flow volume through the pump in response to pressure at an outlet (176) of the compensating valve. The outlet is connected to a variable load limiting control (180). The load limiting control includes a low flow adjustment which varies according to the position of a cam (186) which is connected to the swash plate of the pump, and a high-flow cut-off. The load limiting control reaches higher operating pressures while operating within the power delivery capabilities of the motor. Both the low flow adjustment and high-flow cut-off are manually adjustable to tailor the pump to the operating characteristics of the motor.

Abstract: A control device is herein disclosed which comprises a drive piston 12p for changing the position of a slanting plate in a variable capacity pump 11, an electromagnetic proportional valve 13 for driving the drive piston, and a position detector 14 for detecting a position of the slanting plate. The control device performs a flow rate control of operating oil by controlling the electromagnetic proportional valve in accordance with a difference between a flow rate instruction value Fr for the operating oil and a position detection value from the position detector so as to change the position of the slanting plate. The control device further includes a pressure detector 18 for detecting a pressure of the operating oil supplied to an injection cylinder 10, and correcting means for correcting the flow rate instruction value on the basis of a pressure detection value from the pressure detector to output a corrected flow rate instruction value.

Abstract: A controller, for a variable capacity pump, prevents engine stalls due to rapid changes in operating load by increasing the pump absorption torque when the engine speed is high so as to increase the work amount and by reducing the pump absorption torque when the engine speed is low. The controller receives a signal from an engine speed sensor for detecting engine speed. A pump absorption torque curve is pre-set so as to be consecutively stepped with respect to engine speed so as to intersect at an engine rated point. The pump absorption torque is then calculated in accordance with increases or decreases in engine speed. The pump absorption torque is then set to prescribe values based on the results of these calculations and an instruction is outputted to a control valve in such a manner as to regulate a regulator of the variable capacity pump.

Abstract: A method and apparatus for reducing the loading impact between a sealing element in a suction valve of a piston compressor with a valve stop, wherein the sealing element is forcibly opened using a control device shortly before attaining pressure balance between cylinder and suction chambers of the compressor.

Abstract: A control device for variable hydraulic machines, and specifically for variable axial piston machines equipped with a servo system that is connected to a swash plate so that the discharge/displacement volume is infinitely variable. The hydraulic machine is equipped with a sensor that detects the piston displacement and is connected with an electronical control unit that controls the swash angle position of the swash plate and is pressure controlling the servo system by an electrohydraulic converter. A method for the infinite controlling of the volume flow of hydraulic machines, by which the servo system is connected to the swash plate of the hydraulic machine, and by which a conduction of a signal from a sensor to the control unit, a pressure controlling of the servo system by an electrohydraulic converter as well as the controlling of the swash angle position of the swash plate by the electronical control unit is realized.

Abstract: A rotary reciprocating pumping apparatus is provided with a positive two position adjustment feature which allows the piston stroke to be increased to a maximum and repeatably, automatically, returned to a second calibrated dispensing position. Such rotary reciprocating pump is further provided with an adjustable liquid displacement velocity profile to maintain sufficient velocity of liquid flow at the end of the pump discharge cycle to enable injection of small volumes of liquid through a pump exhaust port, thereby eliminating the inaccurate and time consuming operation of touching off a small volume of liquid as a drop characterizing known rotary reciprocating pumping systems.

Abstract: A system for controlling a discharge flow rate of a variable displacement pump within an oil hydraulic circuit is disclosed. A bypass with a flow restricting valve couples the pressure control chamber of the discharge flow rate controller to the tank line to thereby allow a part of the oil in the pressure control chamber to escape through the bypass to the tank line. This escape occurs when a highly pressured oil is rapidly injected into the pressure control chamber of the discharge flow rate controller as a result of switching operations of both the pressure compensated valve and the load sensing valve.

Abstract: There is provided a displacement control system for a variable displacement hydraulic pump which has a displacement control piston assembly (6) having a large diameter chamber (7) for operating a displacement control member (5) of the variable displacement hydraulic pump selectively in a direction of smaller displacement and in a direction of larger displacement, first control valve (8) and second control valve (9) for selectively communicating the large diameter chamber of the displacement control piston assembly with a pump discharge line and a tank, the first control valve being placed at a supply position by the pump discharge pressure, and at a drain position by a spring associated with the displacement control piston assembly via a feedback lever, and the second control valve being placed at a first position by the pump discharge pressure for communicating the pump port and the large diameter chamber and at a second position by a load pressure for communicating the pump port and the large diameter chamb

Abstract: An adjustable flow pump, particularly an air pump, utilizing reciprocal movement of a diaphragm movement bar to achieve pumping. The stroke of the reciprocating diaphragm movement bar can be adjusted without stopping operation of the pump. The diaphragm movement bar is mounted on a pump main body and a swing member is operably coupled to a rotary output shaft of a motor. The rotary output shaft is connected to a cam which imparts motion to the swing member. The movement of the swing member is transmitted, by a linking member, to the reciprocating diaphragm movement bar which then moves along a linear guide. The stroke of the diaphragm movement bar is adjusted by a linear motion mechanism which is operable to change the position of the swing member relative to the diaphragm movement bar.

Abstract: A pressure governor for a pump (11) employed as a variable displacement pump for supplying pressurized fluid to a hydraulic power consumer (54) is disclosed. The governor includes a differential pressure regulator (13) connected to the pump for establishing the output flow of the pump. The state of the regulator is controlled by a pressure-regulated valve (21). Valve (21) is, in its initial state, set so as to allow a high volumetric flow out of the pump. A portion of the flow out of the pump returned to the pressure regulated valve to force the valve into a second state. The movement of the valve into the second state resets the valve so that a portion of the output of the pump is applied to the pressure regulator. This flow, in turn, causes the regulator to reduce the output flow from the pump. Thus, the initial output flow of the pump is reduced so as to minimize the possibility that large sustained output flows will damage the components of the hydraulic power consumer to which the flow is applied.

Abstract: A piston machine has two pistons which reciprocate in two cylinders. The cylinders define working chambers in which a working medium can either be compressed by the pistons or can exert pressure on the pistons. The pistons are connected to a crankshaft via two connecting rods which are pivotally connected to the same crank pin. The interior of the crankcase forms a third working chamber. The crankshaft is formed as a rotary slide valve which, in operation, connects the first working chamber to the third working chamber and the second working chamber to a working medium supply or discharge opening. The piston machine can be used either as an engine (such as an expansion motor driven by compressed gas) or as a working machine (such as a machine which produces compressed gas). In another embodiment, the rotary slide valve has a rotor which is formed by the crankcase and a stator which is a ring housing.

Abstract: A hydrostatic drive system including an adjustable pump and a hydraulic fluid delivery line connecting the outlet of the pump to the inlet of a hydraulic energy consuming device. An adjustable throttle is located in the hydraulic fluid delivery line between the outlet of the pump and the inlet of the hydraulic energy consuming device. A load-sensing controller is connected to the hydraulic fluid delivery line on opposite sides of the throttle and is operatively connected to the pump to determine the displacement of the pump and to reproduce the pressure drop at the throttle. The load-sensing controller coordinates the pressure difference, .DELTA.p, and the size of the opening of the throttle in accordance with the set speed of movement of the hydraulic energy consuming device.

Abstract: A rod pumping unit used in the oil field, which has high efficiency and saves power, characterized in that: for the connection of the 2.omega. crank and the main crank in the 2.omega. crank balance device there is provided a differential phase adjusting mechanism, for the walking beam balance there is provided beam balance mass lowering device having positioning mechanism or self positioning mechansim, these devices can be adjusted manually in non-stopped status or by computer. The advantages of the pumping unit of the present invention are that the torque fluctuation of the speed reducer is small, the negative work of the power machine is eliminated and the power consumption and the total weight of the machine are decreased greatly. The present invention may save power and material to 50% as compared with the conventional beam pumping unit.

Abstract: Large work vehicles include hydraulic implement control systems having an hydraulic pump being driven by an internal combustion engine. The subject invention provides a method and apparatus for controlling such an hydraulic system to limit engine lug. The invention includes a sensor for producing a parameter signal indicating the load on the engine and a pump control for varying the displacement of the variable displacement pump in response to engine load increasing above a predefined level. The response of the pump control is restricted to allow the engine to reach a predefined operating state.

Abstract: A control (27)is disclosed which may be used as an automotive drive control for a variable displacement hydrostatic pump (11). The pump displacement is controlled by servos (37, 39) by control pressure from a charge pump (21). As a pedal (P) of a vehicle engine (E) is depressed, an increasing pressure differential across a fixed orifice (79) moves a control spool (73) to port control fluid to a first servo port (A). If engine speed becomes excessive, or in response to an external pressure signal (121) representing another vehicle condition, the control spool (73) is moved to a position (FIG. 5 )in which control pressure is ported to a second servo port (B), thus positively reducing the displacement of the pump (11).

Abstract: A torque limiter control sets the limit of power which may be absorbed by a pump. A feedback system adjusts the displacement of the pump in responses to changes in the pressure of working fluid at the pump outlet to maintain a set power.

Abstract: Large work vehicles include hydraulic implement control systems having an hydraulic pump being driven by an internal combustion engine. The subject invention provides a method and apparatus for controlling such an hydraulic system to control engine lug while the hydraulic system is operating. The apparatus includes one or more sensors for producing parameter signals in response to the level of one or more hydraulic system operating parameters. A control receives the parameter signals and responsively produces a supplemental control signal which is used to control engine lug.

Abstract: An overload protection device for a drive motor of a pressure generator is provided including an auxiliary pump, flow resistance devices, and a pressure-controlled valve. The drive motor drives the main pump of the pressure generator, whose output flow rate is stabilized by a hydraulic regulating valve, which senses the pressure of the output flow of the main pump. The auxiliary pump is also driven by the drive motor and generates an output flow rate proportional to the rotational speed of the drive motor. An auxiliary hydraulic circuit, including the first and second flow resistance devices connected in series, connects the auxiliary pump to the tank of the hydraulic pressure generator. The pressure-controlled valve includes a control chamber connected with a tapping point in the auxiliary hydraulic circuit for sensing the output flow of the auxiliary pump.

Abstract: A swash-plate, plunger-type hydraulic pressure apparatus, which may operate as a hydraulic pump or motor, includes a cylinder block, an annular array of plungers slidably held in the cylinder block, a swash plate, a plurality of shoes angularly movably coupled respectively to the ends of the plungers, and a retainer plate mounted adjacent the swash plate and holding the shoes in slidable contact with the sliding surface. The shoes have respective annular grooves defined in the outer cylindrical surfaces thereof. The retainer plate has a plurality of shoe holding holes defined therein and a like plurality of cutout openings extending from the holes. The shoe holding holes communicate with one of outer and inner circumferential edges of the retainer plate through the cutout openings, respectively. The cutout openings have a width slightly larger than the outside diameter of the annular grooves, whereby the annular grooves can be inserted into the shoe holding holes, respectively, through the cutout openings.

Abstract: A displacement control device of a variable-displacement hydraulic pump which increases the response speed when the pump discharge pressure is low and suppresses increase of the response speed when the pump discharge pressure is high. The displacement control device has a variable-displacement piston 3 which activates a displacement control member 2 of the variable displacement hydraulic pump 1, a circuit 10 which provides a communication between a large-diameter pressure chamber 6 on the variable-displacement piston 3 and an output port 9 of the control valve 7, and a variable restriction valve 11 which is provided in the circuit 10. The restriction valve 11 increases and decreases its opening area when the pump discharge pressure is low and high, respectively.

Abstract: Closed loop control circuit for a variable hydraulic pump the output flow of the pump being variable by control means and the pump including at least two closed loop controllers actuating the control means, wherein at least one hydraulic switching element is provided which automatically connects to the control means the closed loop controller providing the highest or the lowest pressure.

Abstract: A system comprising a secondary mover such as an hydraulic pump driven by a prime mover such as a motor powered, in use, by an alternating current (AC) electrical supply, whereby the operation of the secondary mover is affected by any frequency variation in a substantially constant voltage AC supply. The system further comprises adjustment means in use powered by the same AC supply as the prime mover, having inherently substantially the same operating characteristics as the prime mover, being coupled to the secondary mover and operable to adjust the operating range thereof in accordance with variations in the frequency of the AC supply.

Abstract: A control system for a hydraulic pump of the variable displacement type using a pair of coaxially arranged pressure responding pistons. The control system comprises a servo valve for controlling a conduit of pump delivery pressure which is to be applied to a larger chamber of a servo cylinder in response to the pump delivery pressure and external pilot pressure. The servo valve includes a servo spool for controlling the conduit in order to control the pump delivery pressure, a servo sleeve for movably receiving the servo spool, a pump delivery pressure responding piston for biasing the servo spool in response to the pump delivery pressure, an external pilot pressure responding piston adapted for biasing the servo spool in response to the external pilot pressure and being coaxially arranged with the pump delivery pressure responding piston. The lever assembly causes the servo sleeve to move in accordance with the movement of the servo piston.

Abstract: A control system for a variable displacement hydraulic pump with a two-lever type of feedback lever mechanism. The control system comprises a pressure responding ram for causing, upon receiving pump output pressure or outside pilot pressure, a servo spool of a servo valve to be displaced, the servo valve for causing a larger chamber of a servo cylinder to be selectively supplied with the pump output pressure, the servo cylinder for controlling angle of inclination of a swash plate of the pump in order to control the pump output flow rate, a two-lever type of feedback lever mechanism for linking the pressure responding ram, the servo spool of the servo valve and the servo piston of the servo cylinder to each other.

Abstract: A pilot-operated pressure relief valve is provided for a hydrostatic transmission. The override valve is in the closed circuit loop, which includes a pair of multi-function valves and a displacement control valve. The pressure override valve includes a spool slideably mounted within a body so as to be responsive to a pressure differential created by pilot flow through the override valve. The spool is biased to a normal position which provides fluid communication between a pressure charge source and the displacement control valve. As the pressure differential in the override valve increases, the spool shifts so as to close such communication from the charge source to the control valve, thereby defeating the pressure signal from the control valve to the servos of the hydrostatic transmission pump.

Abstract: A displacement controlling circuit system for a variable displacement pump, which system permits, following high or low rates of revolution of an engine for driving the pump, the displacement of the pump to be larger or smaller than a displacement determined on the basis of a difference between the pump delivery pressure and a load pressure. The displacement controlling circuit system comprises a revolution sensor (12) for detecting rates of revolution of the engine (9), and means (10, 11) for switching a load sensing valve (5) in such a manner that: when the detected rate of revolution of the engine is high, a displacement control member (2) of the variable displacement pump (1) is actuated in a displacement increasing direction; and, when the detected rate of revolution of the engine is low, the displacement control member (2) is actuated in a displacement decreasing direction.

Abstract: A valve apparatus has a flow control valve having a supply passage communicating with a hydraulic fluid supply source, a load passage communicating with an actuator, and a first meter-in variable restrictor disposed between the supply passage and the load passage and opened dependent on an operation amount there; a first signal passage located downstream of the first variable restrictor and having a passage section for detecting load pressure of the actuator; a tank passage communicating with a reservoir tank; a discharge passage for communicating the first signal passage with the tank passage; and a second variable restrictor provided in the discharge passage and having its opening variable dependent on the operation amount of the flow control valve to produce in the first signal passage a control pressure different from the load pressure, the control pressure in the first signal passage being led to the hydraulic fluid supply source though a second signal passage.

Abstract: A variable displacement hydraulic piston pump and servo displacement control which combines a rotary vane type actuator and a port plate to obtain both servo and actuation functions for a hydraulic piston pump. The control includes a construction which provides feel to the operator for how much work is being performed. The control also incorporates a failsafe mechanism so that the control is capable of transmitting torque to manually stroke the pump if charge pressure is lost.