Abstract: What is disclosed is a hydraulic drive mechanism for a blanking or forming machine comprising a working cylinder having several pressure chambers, the piston of which acts directly or indirectly on a workpiece to be processed, wherein at least one pressure chamber of the working cylinder for retracting and extending the piston is adapted to be subjected to a tank pressure or a supply pressure via a continuously adjustable valve, and comprising a valve assembly arranged upstream of the continuously adjustable valve, whereby an inlet port of the continuously adjustable valve may be subjected to a higher or lower supply pressure, wherein the valve assembly comprises a switching valve adapted to be switched over between a basic position and a switching position in dependence on the load pressure at the working cylinder in order to tap the supply pressure from a low-pressure source or from a high-pressure source.

Abstract: An embodiment of the present invention involves a zero turn drive apparatus. The zero turn drive apparatus has a housing, which has a first and a second end. The housing has a first end cap mounted on the first end of the housing, and a second end cap mounted on the second end of the housing. A hydraulic pump is rotatably mounted on each end cap, and each hydraulic pump is driven by a pump input shaft. A gear chamber is interposed between each pump. A power take off mechanism is engaged to the housing, and an output shaft extends from the power take off mechanism. An input shaft, which is engaged to each of the pump input shafts, extends into the power take off mechanism and is selectively engaged to the output shaft.

Abstract: A zero turning radius mower has a dual hydrostatic pump with right and left pump arms. A linkage between the pump arms and a pair of control levers destrokes both sides of the pump simultaneously if engine speed drops below a specified value. The linkage allows each pump arm to have a first stroke range if the engine powering the pump is above the specified value, and a second smaller stroke range if the engine powering the pump is below the specified value.

Abstract: To provide a hydraulic circuit with a compact and simple structure while securing the amount of a hydraulic oil necessary for right and left running motors so as to prevent the limitation of a running speed. A first system has a changing valve for a right side running motor and a changing valve for a first actuator, and a second system has a changing valve for a left side running motor and a changing valve for a second actuator. The changing valves for the right side and the left side running motors and the changing valves for the first and second actuators are tandem-connected, respectively.

Abstract: A dual pump apparatus for use on a vehicle or industrial application having a housing in which a pair of hydraulic pumps are mounted and driven by a prime mover. The prime mover is drivingly coupled to a main input shaft, which drives the hydraulic pumps. An auxiliary pump may be drivingly coupled to the main drive shaft and a power take off unit may also be connected thereto. The power take off unit may be driven by a power take off unit output drive shaft, on which a cooling fan may be attached.

Abstract: There is provided a pump unit including a housing, a first and a second pump shafts, a first and a second hydraulic pump main bodies, a first and a second trunnion type movable swash pates, and a first and a second transmission gears. The housing has an inlet port for introducing oil from the outside into its pump accommodating chamber, an oil passage for communicating between the pump accommodating chamber and its gear accommodating chamber, and a discharge port for taking out oil from the gear accommodating chamber to the outside. The pump accommodating chamber includes a supporting wall that supports each base end of the swash plates so that each operational end of the swash plates is directed to the opposite directions to each other. The inlet port and the oil passage are respectively provided at one side and the other side of the pump accommodating chamber with the supporting wall as a reference.

Abstract: A transaxle comprised of a hydrostatic transmission mounted in a transmission housing and having a pair of hydraulic pumps and hydraulic motors operatively connected together through a center section mounted in the housing. First and second axle housings are mounted on opposite ends of the transmission housing, with output axles mounted in the axle housings and connected to the respective hydraulic motors.

Abstract: A hydraulic system including a first pump, a second pump, an auxiliary passage, and a supplemental apparatus. The first pump is in fluid communication with a first valve, and the second pump is in fluid communication with a second valve. The auxiliary passage is in fluid communication with the first valve and the second valve. The supplemental apparatus is in fluid communication, by way of a supplemental passage, with the second valve and the auxiliary passage.

Abstract: An end cap adaptable for use with either a dual hydraulic pump unit having two pumps in a side-by-side arrangement or a pair of separate hydraulic pumps having separate housings. The internal structure of the end cap is arranged in such a manner to permit the separation of the single end cap into two separate end caps. An adapter plate may also be used to attach separate end caps to a single pump housing for use as a dual pump unit.

Abstract: A dual pump apparatus having first and second pump housings is disclosed. A first end cap is mounted to the first housing to form a first sump and a first pump cylinder block is located therein. A second end cap is mounted to the second housing to form a second sump and a second pump cylinder block is located therein. A charge pump is sandwiched between the end caps to provide charged hydraulic fluid to one or both cylinder blocks. An input shaft having a first end external to the hydraulic pump apparatus extends into both housings to simultaneously drive the first pump cylinder block, the second pump cylinder block and the charge pump.

Abstract: A hydraulic control device for a working machine includes control valves; hydraulic actuators controlled by corresponding control valves and divided into groups; unified bleed-off valves disposed on discharge lines of first and second hydraulic pumps; central bypass paths provided in the control valves, the central bypass paths of each group being connected in tandem so as to form a central bypass line; and bypass-cutting valves disposed on the central bypass lines, the bypass-cutting valves being automatically switched so as to open the central bypass lines when the unified bleed-off valves are not operated.

Abstract: The present invention provides a tandem pump unit that includes: a first hydraulic pump and a second hydraulic pump respectively having a first pump shaft and a second pump shaft respectively having adjacent ends connected together so that the first and second pump shafts are coaxially aligned and non-rotatably connected in tandem; a common housing for accommodating the first hydraulic pump and the second hydraulic pump; and a first center section and a second center section that respectively support the first and second hydraulic pumps.

Abstract: A hydraulic control system of the present invention comprising control valves for controlling the direction and flow rate of pressure oil discharged from a hydraulic pump, hydraulic actuators which the pressure oil is fed to and controlled by the control valves, the hydraulic actuators including hydraulic cylinders and a hydraulic motor, and a first return passage provided as a passage for returning return oil present at the head side of one of the hydraulic cylinders to the tank, the first return passage being in communication with the tank, and a second return passage for returning return oil from each of the other hydraulic actuators including the hydraulic motor except for the hydraulic cylinders to the tank, the second return passage having a back pressure check valve and a replenishing passage, the replenishing passage being configured so as to provide a back pressure developed by the back pressure check valve to the low pressure side of each of the other hydraulic actuators to prevent cavitations.

Abstract: Multiple hydraulic machines are located in a common housing. The swashplates are located in longitudinal bores and the barrels in transverse bores. Valve housings are located on either side to accommodate control valves and circuitry. The barrels are mechanically coupled by a gear train for conjoint rotation.

Abstract: A tandem pump assembly of the type including a housing (H), disposed in which is a first pump (11), driven by an input shaft (19), and a second pump (33), also driven by the input shaft (19). The assembly is characterized by the tandem pump assembly including pressure override valve means (71,73) associated with only the first pump (11), and operable, in response to a fluid pressure at a fluid outlet port (35) in excess of a pressure override setting (79), to communicate pressurized fluid to a first fluid pressure responsive means (31), in a manner tending to decrease the displacement of the first pump (11) without effecting the displacement of the second pump (33), until said fluid pressure is substantially equal to the pressure override selling (79), even if it is necessary for the first pump (11) to go over-center from its initial displacement.

Abstract: A dual pump apparatus for use on a vehicle or industrial application having a housing in which a pair of hydraulic pumps are mounted and driven by a prime mover. The prime mover is drivingly coupled to a main input shaft, which drives the hydraulic pumps. An auxiliary pump may be drivingly coupled to the main drive shaft and a power take off unit may also be connected thereto. The power take off unit may be driven by a power take off unit output drive shaft, on which a cooling fan may be attached.

Abstract: There is provided a pump unit including: a pump shaft operatively connected to a driving source; a cylinder block rotatably driven by the pump shaft; a piston unit accommodated in the cylinder block in a slidable manner in an axial direction; a movable swash plate oscillatable on an operational axis perpendicular to the pump shaft, the movable swash plate defining a slide range of the piston unit in abutment against the piston unit; a transmission gear supported by the pump shaft in a relatively non-rotatable manner, the transmission gear being disposed in such a manner as to face to the movable swash plate; a driven member operatively driven by the transmission gear; and a pump case supporting the pump shaft and accommodating therein the cylinder block, the piston unit, the movable swash plate, the transmission gear and the driven member.

Abstract: A dual pump apparatus for use on a vehicle or industrial application having a housing in which a plurality of hydraulic pumps are mounted and driven by a prime mover. The prime mover is drivingly coupled to a main input shaft, which drives the hydraulic pumps. An auxiliary pump may be drivingly coupled to the main drive shaft and a power take off unit may also be connected thereto. The power take off unit may be driven by a hydraulic motor.

Abstract: An embodiment of the present invention involves a zero turn drive apparatus. The zero turn drive apparatus has a housing, which has a first and a second end. The housing has a first end cap mounted on the first end of the housing, and a second end cap mounted on the second end of the housing. A hydraulic pump is rotatably mounted on each end cap, and each hydraulic pump is driven by a pump input shaft. A gear chamber is interposed between each pump. A power take off mechanism is engaged to the housing, and an output shaft extends from the power take off mechanism. An input shaft, which is engaged to each of the pump input shafts, extends into the power take off mechanism and is selectively engaged to the output shaft.

Abstract: The present invention provides a pump unit including at least one hydraulic pump with inlet and outlet ports, a pump case for accommodating the hydraulic pump having an opening through which the hydraulic pump is insertable, and a lid, called a center section, closing the pump case. The center section forms a pair of inlet/outlet passages communicating an end with the inlet and outlet ports of the hydraulic pump and an end opening through a pump case abutting surface of the center section, and a first charging passage by which hydraulic fluid is fed through the pump case abutting surface of the center section. At least one of the pump case and the center section communicates the first charging passage with the pair of inlet/outlet passages via a first hydraulic fluid feeding valve preventing the reverse flow into said first charging passage.

Abstract: A joining directional control valve 13 is disposed to supply, to an arm cylinder 4, not only a hydraulic fluid delivered from a first hydraulic pump 1, but also a hydraulic fluid delivered from a second hydraulic pump 2 when an arm directional control valve 14 is driven. Respective delivery pressures of the hydraulic pumps 1, 2 are detected by pressure sensors 101, 102, and the opening area of a recovery control valve 6 is controlled depending on a lower one of the detected pressures from the pressure sensors 101, 102 such that, even in the combined operation of the arm cylinder 4 and another actuator 3, 4, the hydraulic fluid can be recovered for return to the arm cylinder 4 when the load pressure of the arm cylinder 4 is low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.

Abstract: The present invention provides a pump unit including at least one hydraulic pump with inlet and outlet ports, a pump case for accommodating the hydraulic pump having an opening through which the hydraulic pump is insertable, and a lid, called a center section, closing the pump case. The center section forms a pair of inlet/outlet passages communicating an end with the inlet and outlet ports of the hydraulic pump and an end opening through a pump case abutting surface of the center section, and a first charging passage by which hydraulic fluid is fed through the pump case abutting surface of the center section. At least one of the pump case and the center section communicates the first charging passage with the pair of inlet/outlet passages via a first hydraulic fluid feeding valve preventing the reverse flow into said first charging passage.

Abstract: Disclosed is a vehicle. The vehicle comprises a first hydraulic pump, a first hydraulic motor, a first axle shaft, a second hydraulic pump, a second hydraulic motor, a second axle shaft, a first bypass, a first linkage, a second bypass and a second linkage. The first hydraulic motor is connected to the first hydraulic pump by a first hydraulic porting. The first axle shaft is driven by the first hydraulic motor. The second hydraulic motor is connected to the second hydraulic pump by a second hydraulic porting. The second axle shaft is driven by the second hydraulic motor. The first bypass is associated with the first hydraulic porting. The first linkage is connected to the first bypass. The second bypass is associated with the second hydraulic porting. The second linkage is connected to the second bypass. The first bypass and the second bypass are actuated substantially simultaneously by a single actuating mechanism.

Abstract: To reduce the projection of a swash plate servo mechanism in the radial direction, and to make a hydraulic continuously variable transmission compact, a swash plate plunger pump includes a pump casing provided with an input driven gear. A pump cylinder and a motor cylinder are connected to a transmission output shaft, and a motor pivot member provided with a motor swash plate member is supported to be pivotally movable. A motor servo mechanism includes a ball screw shaft, a ball nut to which an end portion of the motor pivot member is connected, and a swash plate control motor to rotate the screw shaft. A swash plate control motor, located on the side of a hydraulic pump relative to the input driven gear, is mounted to the outside surface of a transmission housing close to the center axis side of a transmission output shaft.

Abstract: In a multistage oil pumping system for an oil supply system of a motor vehicle comprising at least two oil pumps arrange axially in side-by-side relationship, each of the oil pumps is connected to a separate drive so that the oil pumps can be operated independently of one another.

Abstract: The present invention provides a pump unit including at least one hydraulic pump with inlet and outlet ports, a pump case for accommodating the hydraulic pump having an opening through which the hydraulic pump is insertable, and a lid, called a center section, closing the pump case. The center section forms a pair of inlet/outlet passages communicating an end with the inlet and outlet ports of the hydraulic pump and an end opening through a pump case abutting surface of the center section, and a first charging passage by which hydraulic fluid is fed through the pump case abutting surface of the center section. At least one of the pump case and the center section communicates the first charging passage with the pair of inlet/outlet passages via a first hydraulic fluid feeding valve preventing the reverse flow into said first charging passage.

Abstract: One preferred embodiment of the present invention, provides an auxiliary hydraulic drive system having a total hydraulic flow. The system includes a primary hydraulic pump operable to provide hydraulic flow for an implement, and a flow control valve in communication with the hydraulic flow. The flow control valve operates to allow an optimum flow rate and diverts the excess flow amount when the total hydraulic flow exceeds the optimum flow rate. A secondary hydraulic pump is selectively operable to provide additional hydraulic flow. A control system is operable to engage the secondary pump when the total hydraulic flow drops below a minimum flow level; and the control system operates to disengage the secondary pump when the total hydraulic flow exceeds a maximum flow level. In a further embodiment, the invention provides a control unit for a hydraulic system. The control unit includes a sensor to measure total hydraulic fluid flow in a system; and a controller coupled to the sensor.

Abstract: A cryogenic stream is pumped by a cryopump and then vaporized in a vaporizer to produce the pressurized vapor stream. The cryopump is driven by a transmission that is in turn driven by a hydraulic fluid. The hydraulic fluid flows within a hydraulic fluid circuit having first and second hydraulic fluid flow paths. The first of the flow paths is used to drive the hydraulic transmission. The second of the flow paths is dedicated to raising heat. Hydraulic fluid is circulated within the flow path by hydraulic fluid pumps and the amount of heat generated is controlled by adjustable back pressure valves. The adjustable back pressure valves in both fluid flow paths can be adjusted to control the degree to which heat is added to the vaporizer and therefore the pressurized vapor stream. The hydraulic fluid pumps can be driven by diesel engines. Heat may also be recovered from the diesel engines and gear oil used in pumps and the cryopump to also help vaporize the pressurized liquid stream.

Abstract: A drive apparatus for a zero turn vehicle or similar application comprising a pair of pumps mounted in a common housing and having coaxial input shafts and an input shaft mounted in the common housing perpendicular to the two pump shafts. A pair of center sections or end caps including hydraulic porting are mounted to opposite ends of the common housing, and each center section has a hydraulic motor mounted thereon external to the common housing.

Abstract: An end cap adaptable for use with either a dual hydraulic pump unit having two pumps in a side-by-side arrangement or a pair of separate hydraulic pumps having separate housings. The internal structure of the end cap is arranged in such a manner to permit the separation of the single end cap into two separate end caps. An adapter plate may also be used to attach separate end caps to a single pump housing for use as a dual pump unit.

Abstract: A hybrid machine with a hydraulic drive device having hydraulic actuators allowed to operate against and by external loads is provided. To this end, the hybrid machine comprises hydraulic cylinders (7), first hydraulic pumps (P1) connected, with closed circuits, to head side pressure receiving chambers (7S) and bottom side pressure receiving chambers (7L) of the hydraulic cylinders (7), and second hydraulic pumps (P2) connected, with open circuits, to the bottom side pressure receiving chambers (7L) and an external oil chamber (10), wherein the first and second hydraulic pumps (P1, P2) are connected to electric motors (M) so as to be driven.

Abstract: A dual pump apparatus having two pumps mounted in a housing, where the housing comprises two elements mounted on opposite sides of a hydraulic mounting member or center section. The pumps are mounted on one side of the hydraulic mounting member in a pump cavity, and the center section and second housing element form a gear cavity in which gears to connect the two pump input shafts are located. Various charge pumps or auxiliary pump configurations are disclosed, including one embodiment where the input shaft gears themselves may act as a charge pump for the pump assembly.

Abstract: A bent axis hydrostatic module, comprising: a frame, a pair of parallel laterally spaced shafts rotatably supported by the frame and directed outwardly from the frame in the same direction. Two yokes are pivotally mounted about parallel axes on the frame. A hydrostatic power unit is swingably carried by each yoke, and each hydrostatic power unit being operatively connected to one of the shafts to rotate the same. A pair of system pressure conduits in the frame with each of the pressure conduits are fluidly connected to each of the cylinder blocks. A control system is provided for pivoting the yokes including means for independently pivoting the yokes about parallel axes.

Abstract: A hydraulic circuit comprises a first and a second merging line capable of supplying pressure oil from a third pump for a third circuit to directional control valves in a first and a second circuit, respectively, and a merging valve for selectively communicating or cutting off the first and the second merging line with or from the third pump. The merging valve has a first shift position at which the third pump is connected to the second merging line, and a second shift position at which the third pump is connected to the first and the second merging line. The merging valve is shifted continuously between the shift positions. The hydraulic circuit can efficiently distribute pressure oil supplied from the third pump to the first and/or second circuit as well, and can prevent lowering of the operability of each of actuators connected to the first or second circuit.

Abstract: The present invention provides a pump unit including at least one hydraulic pump with inlet and outlet ports, a pump case for accommodating the hydraulic pump having an opening through which the hydraulic pump is insertable, and a lid, called a center section, closing the pump case. The center section forms a pair of inlet/outlet passages communicating an end with the inlet and outlet ports of the hydraulic pump and an end opening through a pump case abutting surface of the center section, and a first charging passage by which hydraulic fluid is fed through the pump case abutting surface of the center section. At least one of the pump case and the center section communicates the first charging passage with the pair of inlet/outlet passages via a first hydraulic fluid feeding valve preventing the reverse flow into said first charging passage.

Abstract: A drive device includes ceramic pumps which alternately pressurize and depressurize fluid within a fluid chamber on opposite sides of a movable body, to thereby move the movable body within the flow chamber. The flow chamber is connected via micro flow passages to an internal-pressure buffering chamber, which accommodates a compressible gas. When the pressure of the fluid is increased and decreased at high speed by the ceramic pumps, the micro flow passages exhibit a high passage resistance, so that the pressure within the channel does not escape to the internal-pressure buffering chamber, and the movable body moves freely. When the pressure of the fluid increases slowly due to the expansion of the fluid, the micro flow passages exhibit a low passage resistance, so that the fluid is led to the internal-pressure buffering chamber, and the pressure increase of the fluid is suppressed.

Abstract: An electromotor M of a electrohydraulic motor pump aggregate G drives at least one pump stage P, P1, P3. An attached element C is inserted between at least one pressure side port of the pump stage, a return line 13, and at least one consumer port A, B, 5, 6. A multiways control valve 3 is installed between the consumer port and the pressure side port. A pressure limiting valve R1, R2 constructed as a seated valve is installed between the consumer port A, B, 5, 6 and the return line 13. The motor pump aggregate G has an automatic hydraulic pressure relieving device D for relieving the system pressure whenever the electromotor M is switched off.

Abstract: The present invention provides a tandem pump unit that includes: a first hydraulic pump and a second hydraulic pump respectively having a first pump shaft and a second pump shaft respectively having adjacent ends connected together so that the first and second pump shafts are coaxially aligned and non-rotatably connected in tandem; a common housing for accommodating the first hydraulic pump and the second hydraulic pump; and a first center section and a second center section that respectively support the first and second hydraulic pumps.

Abstract: A hydraulic jack with dual pump system includes two fluid reservoirs, two pumps for pumping the hydraulic fluid from the fluid reservoirs to an inner fluid chamber of a hydraulic cylinder respectively, and two sequence valves each opening at a predetermined control pressure to enable the hydraulic fluid flowing from the inner fluid chamber back to the respective fluid reservoir, wherein the control pressure preset at the first sequence valve is smaller than that preset at the second sequence valve. Therefore, at a no load condition, the pumps are pumping the hydraulic fluid to the inner fluid chamber to speed up the lifting up of the lifting arm, and at a load condition, the first sequence valve is opened by means of a loading pressure while the second pumping means keeps pumping the hydraulic fluid to the inner fluid chamber to substantially lift up the lifting arm.

Abstract: A compact construction vehicle includes a pump drive system including an engine having a flywheel. A first pump assembly is coupled directly to the flywheel such that a rotation rate of the first pump assembly is the same as a rotation rate of the flywheel. A power transfer system is coupled directly to the flywheel and provides a rotation rate which is different than the rotation rate of the flywheel. A second pump assembly is coupled to the power transfer system such that a rotation rate of the second pump assembly is the same as the rotation rate of the power transfer system. One of the first and second pump assemblies provides power for travel of the compact construction vehicle, while the other of the first and second pump assemblies provides power for a work group of the compact construction vehicle.

Abstract: A dual pump apparatus for use on a vehicle or industrial application having a housing in which a pair of hydraulic pumps are mounted, having by at least one charge pump mounted on an end cap, and the trunnion arms for controlling the hydraulic pumps extending out of opposite sides of the housing. A cooling fan may be mounted on the primary or secondary input shaft on the opposite side of the pulley used to engage the prime mover. An auxiliary pump may also be mounted on the primary input shaft and may be located either at the input end thereof adjacent to the pulley, or on the opposite side of the housing.

Abstract: The invention relates to a hydrostatic traveling mechanism (1) which comprises a hydraulic pump (4), a first hydraulic engine (8) that is linked with the hydraulic pump (4) via a hydraulic work circuit (2) and that drives a first drive train (17). The traveling mechanism further comprises a second hydraulic engine (10) that is linked with the hydraulic pump (4) via a hydraulic work circuit (2) and that drives a second drive train (19). The inventive traveling mechanism is also provided with a third hydraulic engine (23) that is coupled with the first drive train (17) and a fourth hydraulic engine (24) that is coupled with the second drive train (19). The third hydraulic engine (23) and the fourth hydraulic engine (24) are linked with each other via a hydraulic secondary circuit (3) that is independent of the work circuit (2).

Abstract: A hydraulically operated drive system for mini-loaders and like machines is disclosed. The system incorporates hydraulically operated wheels or sprocket/track arrangements as well as auxiliary functional mechanisms. Tandem hydraulic pumps are used, each one thereof being connected to a multiple spool series valve, providing two separated hydraulic circuits, each of which has a separate relief valve. Each multiple spool series valve controls a wheel motor and a loader/lift or like function. Each multiple spool series valve includes a single-acting spool connected to a common spool valve to provide auxiliary power control.

Abstract: A hydraulic actuator that is capable of substantial actuation but does not require a conventional pump, uses only deflectable membranes and passive valves, or, at most, a minimum of active valves, and, under certain circumstances, may be free to move when the actuator is de-energized, is provided. The actuator utilizes the deflectable membranes to move fluid throughout the actuator. The movement of the fluid actuates a shaft or other suitable device, as required.

Abstract: A hydraulic rescue system comprises a fluid reservoir, a pump assembly having a plurality of pump modules, and a manifold assembly having a corresponding number of manifold modules. Each pump module includes an input port for drawing hydraulic fluid from the fluid reservoir and an output port for supplying hydraulic fluid under pressure to a hydraulic rescue tool. Each manifold module includes a fluid circuit that is adapted to fluidly connect the output port of one of the pump modules with a hydraulic rescue tool. A PTO adapter is connected to the pump assembly and is operably connectable to a PTO shaft of a vehicle transmission for operating the pump modules. In this manner, a number of different hydraulic rescue tools can be operated simultaneously with full pressure from the pump assembly.

Abstract: An hydraulic power system having a reversible motor operating a pump to deliver liquid under pressure to operate an actuator mechanism, where the motor is submerged within the liquid inside a reservoir. Flow direction of the liquid is controlled by alternating the direction of rotation of the motor and pump.

Abstract: A hydraulic oil flow controller for a construction machine comprises an operating valve 6 for supplying hydraulic oil discharged from hydraulic pimps 1 and 2 to an attachment, an attachment operating unit 11 for transmitting a pilot signal corresponding to the manipulated variable of the operating valve 6 and a solenoid control valve 12 for changing the flow characteristics of the pilot signal in accordance with a command from a controller 19. An increase and/or decrease signal is sent to the solenoid control valve 12 through the controller 19 from a monitor device 18 so that the flow of the hydraulic oil supplied to the actuator of the attachment is increased and/or decreased. Accordingly, a coefficient of fluctuation of the flow relative to a coefficient of fluctuation of the manipulated variable can be decreased in the work of the attachment of a hydraulic shovel and the operation efficiency upon operation of the attachment can be improved.

Abstract: In a rotary servo valve (1) provided with at least two kinds of pump port (33, 39) for high and low pressures, a spool (11) that is free to rotate and free to reciprocate linearly is installed into a spool guide hole (7) of the valve main body (9), a servo motor (15) that rotates and drives the spool and a linear type actuator (13) that reciprocatedly travels are disposed, and the pump ports are selectively changed over by the reciprocation of the spool, and cylinder ports are selectively changed over by the rotation and at the same time the flow rate is controlled.

Abstract: A transmission mechanism and a pressure oil supply system therefor are provided for use in work vehicles provided with a work device externally of the body of the vehicle at longitudinal one side thereof, the transmission mechanism being simple in construction and serving to shorten the overall length of the vehicle while holding a transmission shaft interconnecting a PTO shaft and an input shaft for the work device close to a horizontal. A work vehicle provided with a work device in front of the vehicle body comprises a transmission 30 disposed between a differential gear unit 10 and an HST 20 and providing a travel cooperative mechanism, a PTO shaft projecting from the housing of the HST 20, and a PTO cooperative mechanism disposed in the housing for dividedly deriving power for the PTO shaft from the travel cooperative mechanism for the transmission of the power.

Abstract: A hybrid machine with a hydraulic drive device having hydraulic actuators allowed to operate against and by external loads is provided. To this end, the hybrid machine comprises hydraulic cylinders (7), first hydraulic pumps (P1) connected, with closed circuits, to head side pressure receiving chambers (7S) and bottom side pressure receiving chambers (7L) of the hydraulic cylinders (7), and second hydraulic pumps (P2) connected, with open circuits, to the bottom side pressure receiving chambers (7L) and an external oil chamber (10), wherein the first and second hydraulic pumps (P1, P2) are connected to electric motors (M) so as to be driven.