Abstract: A swash plate type hydraulic pump or motor comprises first and second swash plates which move reciprocally while opposing first and second pistons, so as to expand and contract a volume chamber according to rotation of a cylinder block. Drive pistons push on the swash plates from behind, causing the first and second swash plates to tilt, respectively. A tilt angle control valve controls the tilt angles of the swash plates by selectively increasing drive pressures that are guided to the drive pistons. A port plate is provided in a sliding portion between the first swash plate and the first piston. The port plate rotates integrally with the cylinder block and guides high and low pressure side hydraulic fluid, which flows through the supply and discharge ports provided in a sliding surface of the first swash plate, to the volume chamber via an inner portion of each first piston.

Abstract: The invention relates to an axial piston drive with a continuously adjustable piston stroke, which comprises a drive shaft (10, 12) on which a swash plate (16) is supported in a crank chamber (14) in such a way as to be tiltable and displaceable in the axial direction, as well as a controller (18, 20) by means of which an tilt angle and an axial position of the swash plate (16) can be adjusted, and at least one piston (26, 28) connected to the swash plate (16) so that it can be actuated to move within a cylinder (22, 24).

Abstract: A hydraulic motor includes a motor cylinder having motor plunger holes, motor plungers disposed in the respective plunger holes, a motor rolling member which is tilted and rolled to change the angle of a swash plate, and a motor servo mechanism for tilting and rolling the motor rolling member. The motor servo mechanism includes a screw shaft with male screw, a ball nut having a ball thread mated to the male screw and connected to an arm portion of the motor rolling member, a swash plate control motor, and a stopper mounted to the end of the screw shaft. The stopper includes a ring portion adjacent to the end of the male screw at a limit position of the ball nut and a flange portion which contacts the side face of the ball nut at the limit position.

Abstract: The speed control apparatus for a hydraulic actuator includes a hydraulic source, an actuator connected with the hydraulic source and driven based on a supply of an operation oil, a direction switching valve which is switchably installed in a flow path between the hydraulic source and the actuator, an inclination piston which is installed between a parallel flow path in parallel connected with a flow path in a supply side of the actuator and the actuator for thereby controlling an inclination angle of an inclination plate of the actuator, a multi-step adjusting inclination piston which is driven when an operation oil is supplied, and adjusts an inclination angle of an inclination plate of the actuator based on multiple steps, and a multi-step adjusting control valve which is switchably installed in a flow path between the parallel flow path and the multi-step adjusting inclination piston, controls an operation oil supplied to the multi-step adjusting inclination piston, and adjusts a speed of the actuator.

Abstract: A pump includes a stationary pump housing having a central longitudinal axis and a housing chamber, a rotating pump shaft extending through the pump housing and into the housing chamber, a rotating barrel fixed to the pump shaft and including a plurality of pump chambers, and a plurality of rotating and reciprocating pump pistons. Each pump piston is at least partially contained within a respective pump chamber. A fluid delivery control assembly is provided to selectively vary the amount of fluid delivered by the pump. At least one pressurized fluid pool is located between a portion of the rotating barrel and a portion of the pump housing. The pressurized fluid pool may be located along an end surface of the rotating barrel and/or along a side of the rotating barrel.

Abstract: The invention relates to an axial piston engine (1) comprising a housing (2) wherein a cylinder drum (17) is arranged. Several axially extending piston bores (21) are embodied in the cylinder drum and arranged in such a way that they are distributed around the longitudinal center axis (7a) of the cylinder drum (17). Pistons (23) are moveably guided in said bores and are supported by sliding shoes (29) on a pivoting mounted on a transversely extending pivoting axis (27). A stop (44b) or a stop (44a, 44b) on both sides of the pivoting axis (27) is/are provided in order to limit the pivoting movements of the pivoting plate (26). In order to stabilize the axial piston engine and provide it with a simple design, the stop (44b) or both stops (44a, 44b) are arranged on a sleeve-like supporting element (45) which is supported by the inner covering surface (3c) of the inside of the housing (4).

Abstract: A hydraulic unit has a drive shaft (52) mounted in a manifold block (54) and coupled to a torque plate (80) on a central axis. A bent axis motive unit (60) has a yoke connected to the manifold block supported for rotation on the yoke. Hollow pistons (100) in cylinders in the cylinder block allow fluid to flow through a torque plate into and form the manifold without the necessity for passing fluid through an articulating member that pivots the cylinder block.

Abstract: An adjusting device (1) for adjusting the swash plate (12) of an axial piston engine (1) with a swash-plate construction has an actuating piston (18) which acts on the swash plate (12) of the axial piston engine (1); and a control value (19). The control valve (19) is used to regulate the actuating pressure which is present in an actuating volume (45) and which is acting on the actuating piston (18), in accordance with a control force acting on a valve piston (20) of the control valve (19). The actuating piston (18) is structurally separate from the control valve (19) and the actuating piston (18) is connected to the valve piston (20) of the control valve (19) by a readjusting spring (34) that opposes the control force.

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: When the load acting on a fluid motor (25) increases, a changeover valve (61) starts to be changed over toward a low-speed position L, but at this time an additional pilot fluid whose pressure is determined by the amount of fluid flowing into or out of a second passage (68) through first and second notches functions as a pressure regulator for a spool (65), and lowers the pressure within the second passage (68) without lowering the pressure within a high pressure-side main circuit (28), thereby tilting a swash plate (26) from a position of high-speed rotation to a position of low-speed rotation.

Abstract: A variable displacement axial piston pump is typically used to receive fluid from a tank and supply pressurized fluid through a control valve to move an actuator. The present variable displacement axial piston pump has a swashplate arrangement that is capable of being angled in two different directions to control the pressure transitions between the low pressure inlet port passage and the higher pressure outlet port passage as cylinder bores in a barrel of a rotating group rotate through trapped volume regions situated between inlet and outlet port passages of the axial piston pump. Movement of the swashplate arrangement in two different directions provides smooth pressure transitions and increases the operating efficiency of the variable displacement axial piston pump.

Abstract: A control system, method and apparatus are provided in which a wobble plate assembly is adjustably mounted on a piston and cylinder stroke control assembly. The wobble plate assembly is adjustable through various positions relative to the base, thus providing an adjustable tilt angle to the wobble plate assembly and different strokes for the pumping pistons. In another embodiment the wobble plate assembly is affixed to a clearance volume control assembly, thus providing for simultaneous, independent adjustment of piston stroke and clearance volume of the axial device.

Abstract: A hydrostatic variable displacement pump has a swash plate (3), which is used to adjust the stroke of displacement pistons in a cylinder block. The swash plate has its angle position pivoted in relation to the stroke direction of the displacement pistons by means of a servosystem. The servosystem is fitted on the housing (6) of the variable displacement pump. The servosystem (4) has a pressure cylinder (18) and a servopiston (7), which together form a servocylinder pressure chamber (8). The servopiston (7) operates in the pressure cylinder (18), is subjected to compressive loading by means of a spring assembly (9,10) and has a piston with at least two servopiston surfaces (11, 12) subjected to the action of pressure.

Abstract: An apparatus and method for controlling a discharge pressure of a variable displacement hydraulic pump. The apparatus and method includes a swashplate pivotally attached to the pump, a valve plate located on the pump to allow hydraulic fluid to enter the pump through an intake port on the valve plate, and to exit the pump through a discharge port on the valve plate, the hydraulic fluid entering and exiting the pump responsively creating a pressure carry over angle &ggr;, a control servo operable to control an angle of the swashplate relative to the pump, a servo valve having an output port hydraulically connected to the control servo and an input port hydraulically connected to the pump output port, and means for controlling the servo valve as a function of the discharge pressure of the pump and responsively balancing a torque induced by the pressure carry over angle &ggr; with a torque generated by a control pressure Pc at the control servo.

Abstract: A variable swash plate compressor (10), including a housing (12), a top inlet (14A), a bottom inlet (14B), a pumping chamber (16), a compression piston (18), a top outlet (20A), a bottom outlet (20B), a drive shaft (22), a control surface element (24), a pinnacle element (26), a swash plate (28), a bore (30) and a pocket (32) formed in the swash plate (28), a pivot element tip (38) and fulcrum piston assembly (40). Wherein the angle of the swash plate (28) relative to the drive shaft (22) is varied to bring about a larger or smaller travel path of the double-sided compression piston (18) and thereby increasing or decreasing the output capacity of the variable swash plate compressor (10).

Abstract: A description is given of an adjustable hydrostatic axial piston machine whose angle can be varied by means of a servo-piston (9) to which actuating pressure can be applied and which is connected to an electrohydraulic control valve. The control valve has a control piston (15) and a control sleeve (22) which can be moved axially relative to one another. The control piston (15) can be axially adjusted with a stepper motor (10), and the control sleeve (22) is coupled mechanically or hydraulically to an adjusting mechanism (9, 7) for the angle for the purpose of feeding back the angle.

Abstract: The invention relates to an axial piston motor constructed as a swivel-slide structure with a channel to feed cleaning fluid to the driving shaft bearings. The axial piston motor (1) comprises a swivelling cylinder drum (8) and a driving shaft (3) supported on driving shaft bearings (4, 5). The driving shaft (3) is connected to a driving shaft flange (6) to which movable pistons (11, 12) are coupled through the cylinder bores (9, 10) of the cylinder drum (8), and on which the cylinder drum (8) is supported by a central journal (16). In addition, the invention provides for a control specular element (18) with reniform control elements and a regulating device (26), by which the cylinder drum (8) together with the control specular element (18) can be swivelled. According to the improvement added by the invention, the cleaning fluid channel is taken through the setting journal (25) and control specular element (18) up to the central journal (16).

Abstract: An apparatus, for controlling a plurality of hydraulic motors and a clutch for driving a drive shaft, can prevent a speed change shock and a load slip of a hydraulic motor as well as making a structure simple. The apparatus includes: a first volume variable hydraulic motor (1), connected to the drive shaft (3) through the clutch (5); a second volume variable hydraulic motor (2), which is always connected to the drive shaft (3); first tilt rotation control means (7, 8), for controlling a tilt rotation amount (a discharge volume cc/rev) of the first hydraulic motor by receiving a drive side pressurized oil (Pac) of the first hydraulic motor; and a zero tilt rotation holding means (10, 10A), for holding the tilt rotation amount of the first hydraulic motor at substantially zero in a state wherein the tilt rotation amount of the first hydraulic motor is controlled to be substantially zero.

Abstract: A variable displacement bent axis hydraulic unit includes a control mechanism having a control housing with a displacement feedback sleeve and spool connected by a spring. A computer controls a proportional solenoid fluid valve that is in operative fluid engagement with the end of the spool opposite its spring connection with the displacement feedback sleeve. The displacement feedback sleeve is urged by the spring into engagement with a cam member on the yoke of the bent axis unit.

Abstract: A special ball joint for servo piston actuation in a bent axis unit includes an elongated actuator rod having a substantially spherical external surface on a first end and a servo piston on a second end. Also included is a single-piece yoke adapted to carry a cylinder block and rotate about an axis of rotation. A socket having a substantially spherical surface is interposed between the yoke and the spherical surface on the rod such that the actuator rod rotates the yoke with forces residing in at least two planes when hydraulic pressure is applied to the servo piston. Two servo pistons and two such ball joints can be applied to the yoke to obtain rotation of the yoke which is up to greater than plus or minus 45° from a neutral position. The external surface on the first end of the actuator rod and the socket must be mating so as to provide freedom of movement. The socket can be incorporated into the yoke itself. The foregoing servo pistons are received in servo bores of a one-piece control housing.

Abstract: An axial piston displacement machine for converting hydraulic work into mechanical work or vice-versa with a plurality of hydraulic cylinders which are rotatably arranged with substantially parallel axes about a joint longitudinal axis, including pistons which are movably arranged in the cylinders and which are in connection with a swivellable plate an adjusting device for setting the swiveling angle of the plate a sleeve which rotates with the cylinders and is arranged outside of the plate, and engagement means for transmitting a torque between the plate and the sleeve on the plate and on the sleeve. An increased efficiency is achieved by including a toothed wheel attached on the outer circumference of the sleeve in order to tap a torque from the sleeve or to introduce a torque to the sleeve.

Abstract: An axial plunger slurry pump comprises a pump body, a sloping cam plate, a swashplate, cylinders, plungers and a pump head. Each of the plungers comprises a plunger body with a rubber piston positioned in its front end and being able to slide over it, and an oil receiving gap communicating with an oil passage disposed between two facing end surfaces of the plunger body and the rubber piston. There are check valves each of which is provided in an oil passage between a ball of each of two-ball links, which ball is coupled with the swashplate, and the swashplate. Each of the cylinder and the plunger body are fitted together by means of a half-and-half locating pad, a cylinder sleeve, a pressing cap, and a locking device. The pump may be used widely in drilling, electric power, mine, building, and metallurgy, etc., for conveying mud, mortar, ore pulp, coal pulp, concrete, etc.

Abstract: An axial piston machine (1) which includes a cylinder block (2) having cylinder bores (3, 4) in which pistons (5, 6) are movably guided, with the pistons (5, 6) being supported on an inclined or wobble plate (25) in order to perform a lifting movement. The axial piston machine (1) further includes a pivot device (31) for varying the inclination of the inclined or wobble plate (25) by pivoting about a pivot axis (27). Provided is a damping element (41) which includes a damping piston (40) which acts on the inclined or wobble plate (25) and is movably disposed in a damping cylinder (42) which is connected to a pressure fluid reservoir (48) via a throttle element (47) and a non-return valve (44) is disposed parallel thereto.

Abstract: A variable displacement hydrostatic pump (11) having its displacement varied by a controller (17) in response to movement of a manual control lever (95) from a neutral position (FIG. 1). The vehicle has at least one other device (125,127) which provides an electrical output signal (133) indicating when operation of the pump (11) is "acceptable", in terms of either vehicle performance or operator safety. Associated with the control lever (95) is an input shaft (103) defining at least one stop surface (121,123). A solenoid assembly (109) has a moveable plunger (111), disposed adjacent the stop surfaces, and moveable between a retracted position (FIG. 4a) and an extended position (FIGS. 2 and 4), engaging one of the stop surfaces, when the output signal (133) indicates that operation of the pump is not acceptable.

Abstract: Pressurized fluid motor comprising a casing, a cylinder block, a cam, an internal fluid distributor and a selector. The bore of the selector has four grooves. Two of them are communication grooves each connected to a main (feed or exhaust) power duct and to a connection duct, the connection ducts being themselves connected to different groups of distribution ducts. The other two grooves of the bore are branch grooves respectively connected to an additional (feed or exhaust) power duct and to a third connection duct. The slide of the selector comprises at least a first selection groove which is adapted to establish communication between the two branch grooves. By modifying only the shape of the slide, and possibly that of the bore of the additional duct, the selector can provide different functions.

Abstract: A hydraulic axial pump/motor comprises a plurality of revolving as well as reciprocating pistons, operatively associated with a stationary port plate. The port plate comprises at least a first, elongated, arcuate suction port and at least a second elongated, arcuate discharge port, divided by a bringing portion extending between the downstream side of the suction port and the upstream side of the discharge port. A tortuous passage of a non-uniform cross-section is formed in the bridging portion, allowing the by-passing of the fluid first in a direction towards the downstream side of the suction port and then towards and into the upstream side of the discharge port.

Abstract: A control system, method and apparatus are provided in which a rotatable wedge portion which is solidly mounted on a rotatable base engages piston and cylinder assemblies as the base rotates. In another embodiment the rotatable base is not affixed to the shaft, but instead is allowed to rotate with respect to the shaft, while the shaft is affixed to the cylinder and piston, which rotate with the shaft. The wedge is rotatable through various positions relative to the base, thus providing an adjustable tilt angle and different strokes for the pistons. In another embodiment, the single wedge is replaced by a double wedge assembly.

Abstract: A hydrostatic axial piston machine with a swash plate achieves a high power with a compact and simple construction. Two cylinder drums are at some axial distance from one another and are in synchronous rotation. Each drum contains a group of concentric cylindrical borings, between which, and at an angle with respect to the axis of rotation of the axial piston machine there is a rotationally locked circular ring-shaped eccentric disc. The pistons are guided against the disc so that they can move longitudinally in the cylinder bores. Each piston consists of two piston segments having the same diameter oriented coaxially to one another and at some distance from one another. The segments are inserted in cylinder bores which are located opposite one another and are connected to one another by a bridge segment. Two support bodies, one on either side of the eccentric disc, are provided for movement on the eccentric disc along a track.

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: The invention relates to an axial piston pump with at least one pump element, which includes a piston disposed in a housing, with a drive shaft upon which a swash plate for driving the piston is disposed. The swash plate is non-rotatably fixed, but can pivot around a swash plate pivot axis which extends perpendicular to the longitudinal drive shaft axis (A), and with a device for adjusting a pivot angle between the drive shaft and the swash plate. In order to be able to adjust the oblique position of the swash plate in a simple manner, even during pump operation, it is provided that the device for adjusting the pivot angle of the swash plate has a displacing device disposed in a stationary manner on the housing.

Abstract: In a piston pump/motor of swash plate type which comprises: a cylinder block disposed in a casing to be rotatable jointly with a shaft therein; a plurality of pistons slidably inserted in the cylinder block parallel to the shaft; and a swash plate swingably attached to the casing for guiding the plurality of pistons on a front surface thereof and changing a displacement of each of the pistons by changing an inclination thereof, there is provided a swash plate angle changing apparatus in which the swash plate has a rear surface formed with a first contact surface and a second contact surface which make an angle between them. The casing has a swash plate support surface which is perpendicular to the shaft and with which the first contact surface and the second contact surface are each adapted to contact.

Abstract: A method and apparatus for braking a rotating element including a reversible eccentric ring or axial piston pump which may be selectably operatively connected to a rotating element. When either pump is configured to compress ambient fluid into a reservoir, the compressive resistance is transmitted to the rotating element, braking it. When either pump is configured to expand fluid from the reservoir, the resultant torque generated is transmitted to the rotating element, driving it. The invention provides mechanisms for rapidly configuring either pump to compress or expand fluid, and for adjusting pump displacement, respecting a user's demand.

Abstract: An axial piston pump assembly includes a housing having an outer wall defining a generally cylindrical interior and an end wall. A drive shaft extends through the end wall is rotatably mounted in the housing for rotation on the axis of the cylindrical interior, and the rotor is attached to the drive shaft for rotation therewith. A plurality of circumferentially spaced, axially disposed cylinders is positioned in the rotor, and a series of axially reciprocable pistons is disposed in the cylinders. A swashplate surrounds the drive shaft and is mounted in the housing for tilting movement on a tilt axis transverse to the drive shaft axis. A planar reaction surface on the swashplate is engaged by the outer ends of the pistons. A biasing arrangement is provided for urging the piston ends into engagement with the reaction surface, and a control arrangement is supplied for tilting the swashplate on its axis to maintain the reaction surface angularly disposed with respect to the axis of the drive shaft.

Abstract: A continuously variable hydrostatic transmission includes an input shaft connected to drive a hydraulic pump unit, a grounded hydraulic motor unit, and an output shaft. A wedge-shaped swashplate is pivotally mounted to the output shaft in driving connection to receive output torque resulting from the exchange of pressurized hydraulic fluid between the pump and motor units through ports in the swashplate. A hydraulically actuated ratio controller is pivotally linked to the swashplate to selectively adjust the swashplate angle relative to the output shaft axis and thereby change transmission ratio.

Abstract: A swash plate actuating device for an axial piston unit has a swash plate tiltably mounted within the housing. A pair of axially aligned actuating chambers defined in the housing slidably receive the opposite ends of an elongate actuator and are disposed on opposite sides of a distal end portion formed on an actuator lever connected to the swash plate. A connector has a mounting portion spanning a transverse slot in the actuator and seated on a planar surface of the actuator. A guide portion of the connector is disposed within the transverse slot and has a bearing slot slidably receiving the distal end portion of the actuator lever.

Abstract: A swash plate type hydraulic motor switchable between high speed and low speed, comprises a main case, a cylinder block supported in the main case to be rotatable about a rotational axis, the cylinder block including a plurality of plungers having longitudinal axes extending parallel to the rotational axis, a swash plate supported in the main case for contacting forward ends of the plungers and pivotable about a pivotal axis between a high speed position and a low speed position, the pivotal axis extending parallel to a plane perpendicular to the rotational axis, and two trunnions projecting on the pivotal axis from opposite peripheral positions of the swash plate.

Abstract: A variable displacement mechanism for a swash plate hydraulic pump or motor, in which a swash plate, a swash plate guiding wall, a tilting control piston, and a swash plate tilting guiding and swash plate rotation preventing pin are included for varying the requiring flow rate (volumetric displacement) per revolution without the rotation of the swash plate even during the tilting of the swash plate angle and during the rotation of the hydraulic pump or motor. The periphery of the swash plate is spherical for smoothing the tilting of the swash plate, and a securing pin accommodating slot is formed on the lower portion of the swash plate. Further, there are provided a securing pin for preventing rotation of the swash plate, and a bore formed on the bottom of a front cover for installing the securing pin.

Abstract: A transmission with a static, hydraulic continuously-variable-speed transmission mechanism comprising a hydraulic circuit having a closed circuit, a hydraulic pump connected on the crankshaft of an engine, and a hydraulic motor having a motor output shaft coaxial with the axis of rotation of the hydraulic pump, and contained in a casing with its axis extended in parallel to that of the crankshaft. The static, hydraulic continuously-variable-speed transmission mechanism has a small construction and has an increased degree of freedom of selection of speed change ratio. An output shaft, i.e., the final output shaft of a transmission is supported for rotation on a casing with its axis extended in parallel to that of a static, hydraulic continuously-variable-speed transmission mechanism. A motor output shaft and the output shaft can be interlocked by a reduction mechanism.

Abstract: A hydraulic machine is disclosed in several embodiments as a pump, as a motor, and as a combination pump/motor. The machine's fixed cylinders are positioned circumferentially to a drive shaft, the pistons being driven by, or acting against, a split swash-plate which is supported primarily by the same main bearing in which the drive shaft rotates. The inclination of the split swash-plate is adjusted by an axially-movable servo mechanism which is also arranged circumferentially to the drive shaft. Preferred embodiments include, among other features, (i) various gimballed-yoke supports for the non-rotating portion of the swash-plate, (ii) various designs for a rotating valve-plate, and (iii) a radial valve system. The unique arrangement of elements provides a machine that is remarkably compact and lightweight, being (a) significantly smaller than commercially-available machines having similar horsepower ratings and (b) operable hydrodynamically (i.e., at constant horsepower) at reduced speeds.

Abstract: A compact and light flow dividing pump is disclosed. The pump includes a housing having an end plate attached to one end thereof. The end plate has a fluid suction port and a pair of fluid discharge ports. A pump mechanism is provided in the housing for receiving fluid through the suction port and discharging the received fluid through the discharge ports. A plurality of discharge passages are formed in the end plate between the pump mechanism and the discharge ports. A control valve is also provided in the end plate to control the flow rate of fluid in the discharge passages.

Abstract: A hydraulic driving system uses a variable capacity type swash plate piston pump that discharges a fixed quantity of operation oil. The piston pump is provided with a swash plate and a swash-plate tilt angle control mechanism. The pump is operated by the engine to drawing discharge oil whose quantity corresponds to the tilt angle of the swash plate. An oil passage provided with a restriction, is connected to the discharge side of the piston pump. A control valve functions in accordance with the pressure difference between the input and output sides of that restriction to feed operation oil to the tilt angle control mechanism via the oil passage. A tilt angle generating mechanism in the tilt angle control mechanism, causes the oil controlled by the control valve to act on the swash plate in order to increase its tilt angle. A tilt angle return mechanism in the tilt angle control mechanism urges the swash plate to decrease the tilt angle.

Abstract: Variable displacement axial piston pumps are useful in outputting pressurized fluid to operate fluid actuators. The currently available center pivoted variable displacement axial piston pumps waste energy by compressing trapped volumes of oil during operation. The present variable displacement axial piston pump has first and second opposite sides of a swash plate pivotally connected to a pump housing by a pair of off-center pivots with the angle of the swash plate being controlled by first and second actuators connected to the opposite sides of the swash plate. Each of the off-center pivots includes a pair of pivot pins connected to the housing and releasably pivotally seated in a pair of semi-cylindrical pockets formed in the opposite sides of the swash plate. The first actuator at the first side of the swash plate holds the semi-cylindrical pocket seated against the pivot pin while the second actuator controls pivotal movement of the swash plate about the first off-center pivot.

Abstract: The invention concerns axial piston machines for installation in gearboxes and for detachable attachment thereto, having an machine housing open on one side, a connection block which closes this housing and has a pressure duct and an suction duct for the pressure medium, and a driving shaft rotatably mounted in the machine housing and the connection block, which drive shaft projects from the axial piston machine for the purpose of connection to a gear unit, the gearbox being capable of being closed by means of a gearbox cover, and having through apertures for the supply and discharge of the pressure medium to the pressure duct and suction duct.

Abstract: A variable displacement axial piston pump (11) is disclosed of the type including a displaceable cam member (39) to vary the pump displacement in response to operation of a fluid pressure actuated servo assembly (15). The servo assembly includes a servo piston (47), the position of which is controlled in response to control fluid in a pair of servo chambers (53,55). The flow of control fluid pressure from a charge pump (27) to the servo chambers is controlled by a manual controller (17), which includes a main control orifice (105). The nominal gain rate of the pump and servo assembly is determined largely by the main control orifice (105). The servo piston (47) defines a servo orifice (113) communicating between the servo chambers.

Abstract: An infinitely variable differential hydrostatic transmission utilizing a fixed displacement pump/motor and a variable displacement pump/motor interconnected with appropriate valving, to provide a mechanical/hydraulic differential drive which is capable of achieving an overall efficiency in the 98.degree.-99.degree. range. In the preferred embodiment, which utilizes axial piston type pump motors, pistons in multiples of four are utilized in order that each piston will have a piston located 90.degree. from it to serve as its control valve. The fixed and variable displacement motor/pump are provided as an integral unit containing bearing mountings, cylinder barrels, valve ports, piston seal mountings, hydraulic flow passages, pressure reservoirs and manifolding by forming a series of individual segments and sealing them together into a single structural unit. A unique mounting arrangement is utilized to positively attach the pistons to an anti-friction swashplate which eliminates all side loads on the piston.

Abstract: The present invention has for its object to provide a swash plate type piston pump/motor which is simple in construction and small in size and which enables a swash plate to be tilted surely. The swash type piston pump/motor is arranged such that a swash plate receiving surface (1) formed in a housing (1) is inclined by a predetermined angle relative to the axis (2) of a rotating shaft (2) so that even when the angle of tilting of the swash plate is increased the distance from the axis of the rotation shaft to the center (12) of a ball (12) which serves as the center of swing of the swash plate can be reduced.

Abstract: A feedback apparatus according to the present invention elastically interconnects the swashplate of a variable displacement hydraulic unit with the valve spool of a hydraulic unit displacement control, and is constructed such that a predetermined spring preload force is developed. A feedback spring extends along the valve spool and is surrounded by an elongated housing coupled with the swashplate. Axially movable spring guides are interposed between opposite ends of the spring and a flange formed at each end of the housing. A suitable spacer is positioned between the spring and at least one of the spring guides to compress the spring to a length representative of the desired preload.

Abstract: A variable displacement hydrostatic unit (11) includes a swashplate (23), the position of which is controlled by a servo piston (73). A multiple mode control (33) is disclosed, including a main valve member (63) and a secondary valve member (65), both of which are attached to a linkage member (61) by which movement of a manual control handle (47) actuates the main and secondary valve members. The flow of control pressure from a charge pump (21) ot the servo piston (73) is controlled by a pair of solenoid valves (83,85) having two control conditions. In one, control pressure flows through the main valve member (63) to give a normal operating mode (FIG. 6), while in the other control condition, control pressure flows through the secondary valve member (65) to provide a secondary operating mode (FIG. 7).

Abstract: An operating speed change-over device is equipped with an automatic speed change-over valve which opens and closes a pilot fluid line that connects a pilot port of a capacity change-over valve of a capacity-variable hydraulic motor to a pilot pump. The automatic speed change-over valve has one pilot port that is connected to a pressurized fluid feed line leading to the hydraulic motor and has another pilot port connected to the return fluid line of the hydraulic motor. The automatic speed change-over valve is changed over by an effective differential pressure between the two fluid lines.

Abstract: A manual servo control valve for variable displacement axial piston pump incorporating a blocking mechanism which serves to block the inlet and outlet ports of the valve when the valve is not operating to change the displacement of the pump.