Abstract: A hydraulic system for a working machine includes hydraulic actuators actuated with hydraulic fluid delivered from a hydraulic pump, control valves each of which is shiftable among shift positions to control a flowrate of hydraulic fluid flowing to the corresponding hydraulic actuator, a detection fluid passage, an interlocking control valve, and a pressure detection unit. Each control valve includes an input port, an output port, and a flowrate reduction section. One of the control valves includes a flowrate increase section. The interlocking control valve is configured to be shifted in accordance with a shift of the one of the control valves among the shift positions and to be shifted to a blocking position to block a pilot fluid introduced into the interlocking control valve from the detection fluid passage when the one of the control valves is shifted to the increase position.

Abstract: A system for controlling pump operation within a work vehicle includes a pump configured to discharge hydraulic fluid into a fluid supply conduit for delivery to first and second hydraulic loads of an associated agricultural implement. Furthermore, the agricultural vehicle includes a pump compensator assembly configured to control the operation of the pump. The pump compensator assembly, in turn, includes a pump regulation actuator and a flow compensator valve. Moreover, the pump compensator assembly includes an electronically controlled pressure compensator valve configured to at least partially control the flow of the hydraulic fluid to the pump regulation actuator for use in controlling the operation of the pump.

Abstract: When a fluid control valve is opened and closed, the port pressure of fluid control valve is guided to a main relief valve through a first passage, and its maximum pressure is controlled by the main relief valve. At the same time, the port pressure of fluid control valve is guided to pressure compensation valves of the respective fluid control valves. As a result, even when functions having different load pressures are simultaneously operated in the fluid control valves, constant operability can be always secured without depending on the load pressures. In addition, when the fluid control valve, which drives a tilt cylinder for a function of tilting a fork, is opened and closed, the port pressure of the fluid control valve is guided to a secondary relief valve through a second passage, and is also guided to the main relief valve and the pressure compensation valves of the respective fluid control valves through the first passage.

Abstract: A controller calculates the ratio between the sum of estimated demanded powers of a plurality of first actuators and the sum of estimated demanded powers of a plurality of second actuators, and calculates, on the basis of the ratio, first and second command values for adjusting allocation between a first allowable torque of a first pump and a second allowable torque of a second pump, and first and second regulators adjust the first and second allowable torques, on the basis of first and second output pressures of first and second torque control valves, such that the first and second allowable torques become values to which a predetermined allowable torque is allocated according to the ratio described above, and control the delivery flow rates of the first and second pumps such that the respective consumed torques of the first and second pumps do not become larger than the first and second allowable torques.

Abstract: In a hydraulic system for a working machine, a controller is configured or programmed to increase an output-port pressure of one activation valve for one hydraulic device and an output-port pressure of another activation valve for another hydraulic device to a normal pressure higher than a preloading pressure from a state where the output-port pressure of the one activation valve is equal to the preloading pressure and the output-port pressure of the other activation valve is lower than the preloading pressure, by causing the output-port pressure of the one activation valve to be lower than the preloading pressure and increasing the output-port pressure of the other activation valve to the normal pressure.

Abstract: A pump jack controller is provided that can harness the potential energy generated during the operation of one pump jack amongst a plurality of pump jacks located at a well site and convert that potential energy into electrical energy that can be used to provide electrical power generated by the pump jack to power the other pump jacks located at the well site.

Abstract: Valve arrangement for influencing a fluid flow for a fluid consumer, having a first valve group with which a first actuator is associated, having a second valve group with which a second actuator is associated, the first valve group and second valve group being associated in a first functional position as a parallel circuit with a first fluid line in a first functional position and are associated with a second fluid line in a second functional position as a series circuit, the first valve group or second valve group being designed for actuating the respective other actuator in the first functional position and being designed for switching off the respective other actuator in the second functional position.

Abstract: A control valve assembly for indirect pneumatic control and method for controlling a working fluid pressure, which enable precise, sensitive and speed-variable controlling. The assembly includes two valve units, a working fluid inlet, and a control fluid inlet. A working fluid channel connects the working fluid inlet through the two valve units to an outlet. A valve piston arranged within a valve cylinder of the valve units is movable between open and closed positions. A spring element biases the valve piston toward the closed position, and a control pressure chamber applies a control pressure counteracting the spring element's bias. When a control pressure is applied in the first chamber, the first valve piston is moved to the open position.

Abstract: A remote demolition robot (10) comprising a controller (17), drive means (14), an arm member (11) movably arranged on a tower (10a) rotatably arranged on a body (11b) of the remote demolition robot (10) and a remote control (22) for providing commands, that are interpreted by the controller (17) causing the controller (17) to control the operation of the remote demolition robot (10), wherein the remote control (22) comprises a first joystick (24a) and a second joystick (24b), wherein the remote control (22) is characterized in that each joystick (24) is provided with a thumb control switch (26).

Abstract: A valve arrangement has an adjustable control valve (10) including a control slide (12) for actuating at least one consumer connection (A, B) and an LS control line. The differential pressure of two actuating pressures (xa, xb) serves for the actuation of the control slide (12). Since the actuating pressures (xa, xb) also actuate a logic valve, which in turn influences an additional valve, and/or actuates a pressure compensator connected upstream to the control valve (10), the difference of the two actuating pressures (xa, xb) initially displaces the control slide of the control valve. The higher or the lower of the two actuating pressures (xa, xb) either actuate the further valve in the form of the additional valve, and/or influences the pressure compensator.

Abstract: A hydraulic assembly for driving and controlling small hydraulic units, such as hydraulic cylinders of a brake and/or clutch of a forestry winch, is disclosed. The hydraulic assembly includes a means for establishing and also maintaining a pre-determined pressure of a hydraulic media. The hydraulic assembly is characterized by as low as possible hydraulic loss. Also, a quantity of hydraulic media required for a regular operation and maintaining the pressure within the hydraulic assembly is as low as possible.

Abstract: A hydraulic motor having pistons, some of which are in a working phase and some are in a non-working phase, whereby the pistons are adapted to rotate the piston hydraulic motor's shaft or casing. To the piston hydraulic motor there are at least two working pressure medium channels, whereby the piston hydraulic motor can be connected for full volume or partial volume. In full volume, all the pistons in the working phase can be brought into the working phase in the motor by a pump's working pressure, whereas in the case of partial volume flow only some pistons can be brought into the working phase by the working pressure. The piston hydraulic motor comprises an actuator, which can close one of the piston hydraulic motor's pressurized inlet channels when the pressure in the other pressure medium channel falls below a certain critical value.

Abstract: An LIFD valve assembly has a pressure balance device a pressure balance slide of which is urged in the opening direction by a pressure downstream of a metering aperture and in the closing direction by a control pressure preferably corresponding to the highest load pressure of a plurality of consumers, and a load pressure downstream of the metering aperture is reportable to a line via the pressure balance device, and a load-maintaining device that can be put in a closing position, in which position a pressure medium flow path from a consumer to the metering aperture is blocked. The pressure balance slide is embodied in divided fashion, with an upper part and a lower part, wherein the latter is guided on the upper part, and determines the pressure balance device throttle cross section with a pressure balance control edge and embodies a closing body of the load-maintaining device.

Abstract: Faster shifting operation and reduced shift shock in response to a braking operation during a lift-foot-up shifting may be achieved when an automatic transmission is controlled by a method for compensating a hydraulic pressure that includes: determining whether a lift-foot-up shifting of the automatic transmission is under control; calculating a vehicle speed of a vehicle; calculating a deceleration rate of the vehicle; calculating a compensation hydraulic pressure to be applied to a friction member of the transmission, based on the deceleration rate; calculating a on-coming pressure based on the calculated compensation hydraulic pressure; and applying the calculated on-coming pressure to the friction member.

Abstract: A vehicular hydraulic system having a hydraulic pump and first and second hydraulic applications arranged in series. A dual relief valve defines first and second flow channels, a passageway and a bypass port. The first flow channel is disposed between the hydraulic pump and the first hydraulic application and the second flow channel is disposed between the first hydraulic application and the second hydraulic application. A first valve member controls fluid flow through the passageway and allows fluid flow from the first to the second flow channel through the passageway when fluid pressure within the first flow channel exceeds a first threshold pressure. A second valve member controls fluid flow through the bypass port and allows fluid flow from the second flow channel to a return line through the bypass port when fluid pressure within the second flow channel exceeds a second threshold pressure.

Abstract: A pressure-compensating directional control valve, for actuating hydraulic actuators, comprising at least one modular valve body, with one through receptacle for a slidable shuttle, a driving fluid delivery port connected to a pump, a discharge fluid port, a first output opening and a second output opening, connected to the first and second chamber, of a hydraulic actuator, at least one bridge for selective communication, by way of the shuttle, of the delivery port with the first or second chambers of the actuator, for actuation thereof, a unidirectional hydrostat connected to the bridge to draw selectively a pressure signal of the load of the actuator, the signal for adjusting selectively the delivery pressure of the pump so as to keep substantially constant the pressure drop between the delivery port and the actuator in any load condition.

Abstract: A pressure-compensating directional control valve, for actuating hydraulic actuators, comprising at least one modular valve body, with one through receptacle for a slidable shuttle, a driving fluid delivery port connected to a pump, a discharge fluid port, a first output opening and a second output opening, connected to the first and second chamber, of a hydraulic actuator, at least one bridge for selective communication, by way of the shuttle, of the delivery port with the first or second chambers of the actuator, for actuation thereof, a unidirectional hydrostat connected to the bridge to draw selectively a pressure signal of the load of the actuator, the signal for adjusting selectively the delivery pressure of the pump so as to keep substantially constant the pressure drop between the delivery port and the actuator in any load condition.

Abstract: The invention refers to the field of hydraulic control devices and refers to a saturation-proof hydraulic control device with two or more elements; each element is composed of a six-way, two-position spool (4) of the proportional type, a pressure compensator (3), also of the proportional type, notches on the spool for a correct operation and pressure selector members (MS) equipped with spring (M7) that connect the various elements so that the work function at higher pressure sends the pressure to the spring side of its own pressure compensator (3), making it operate as check valve, and sending the pressure existing between spool (4) and pressure compensator (3) to the spring side of the compensators (3) of the other elements and to the pump (P). The spring (M7) must generate a minimum load that is slightly greater than the pressure drop of the maximum flow-rate through the local pressure compensator (3).

Abstract: A hydraulic system comprises a variable displacement pump. The hydraulic system includes a first device capable of being hydraulically powered by the pump and a reversing device adapted to cause the first device to autoreverse. The hydraulic system also includes an isolation device adapted to prevent pressure surges resulting from a source other than the first device from actuating the reversing device, thereby preventing undesirable autoreversing of the first device.

Abstract: A hydraulic distributor that has a regulating balance including a housing hollowed in the distributor body and containing coaxially a fixed central core. A tubular plunger is interposed sliding freely, coaxially, between the core and the housing and co-operates with a lateral orifice connected to a working orifice. The core and the plunger define between them an annular chamber. The plunger has a first radial annular surface subjected to the highest charge pressure (LS) and a second annular surface subjected to the pressure of the intake fluid. A central passage in the core constitutes a first orifice emerging at one end of the housing exposed to the highest charge pressure (LS). A second orifice emerges in the annular chamber and a third orifice is located opposite the other end of the housing and remains closed by the plunger as long as the charge pressure of the distributor is below the highest charge pressure (LS).

Abstract: A hydraulic directional control valve with a regulating balance comprising a plunger which can be displaced in a housing (13) under the action of a differential pressure (&Dgr;p) between the intake pressure (P) and the highest load pressure (LS), and which is designed to open, in proportion to this differential (&Dgr;p), a lateral orifice of the housing linked to a working orifice (A, B) of the directional control valve; the wall of the housing and/or the plunger is provided with a calibrated passage linking the intake of fluid at pressure (P) and the lateral orifice when the plunger is pushed back into an end position by the pressure (LS) exceeding the intake pressure (P); consequently, in spite of the excess value of the pressure (LS) intended to inhibit operation of the directional control valve, hydraulic fluid is delivered to the lateral orifice at a low rate and allows the hydraulic receiver controlled by the hydraulic directional control valve to be displaced at a low rate.

Abstract: The present invention provides a hydraulic controller comprising: a plurality of switching spools; a plurality of cylinder ports of a switching valve; a compressed oil passage common to the switching valves having an intermediate chambers, at least a check valve in correspondence with at least a part of said switching spools, and said check valve being positioned between said intermediate chambers and said cylinder ports, so that said switching spools being positioned in a neutral position to close said passage and also being movable to adjust opening degree of said passage, wherein auxiliary ports are provided between the cylinder ports and a tank line; flow rate adjusters are also provided between the auxiliary ports and the tank line for adjusting an opening degree of the passage; pressure detectors are provided in the switching valves for detecting pressures of oils in the intermediate chambers; a maximum pressure selector operatively linked to said pressure detectors for selecting a maximum pressure from

Abstract: A valve assembly for pressure adapted and volumetric flow adapted supply of at least one user may be supplied with hydraulic fluid or connected to a tank via two work ports of a continuously adjustable directional control valve. To the two work ports of the valve assembly a common pressure compensator is associated, the piston of which is guided in axial translation in an axial bore of the directional control valve spool, so that one of the two work ports may optionally be connected to the pump port upon suitable actuation of the directional control valve. At both end surfaces of the directional control valve spool and at the spring side of the pressure compensator piston, there acts a respective control pressure which, for example, corresponds to the highest system load pressure, the individual load pressure, or a pressure derived therefrom.

Abstract: The present invention is directed to a hydraulic pressure control device which can overcome problems, such as a shock to an actuator or a pressure boost phenomenon involving a rapid increase in pump delivery pressure, conventionally encountered when a directional control valve is switched. The hydraulic pressure control device is constructed such that first and second connecting ports are connected to a tank when a directional control valve is in its neutral position, one of the first and second connecting ports is cut off from the tank and connected to an actuator and the other is cut off from the tank and closed when the directional control valve has been switched, in accordance with a position to which the directional control valve has been switched, and a maximum pilot pressure selectively taken from between a pressure compensating valve and a pair of check valves is introduced into a pilot line.

Abstract: A hydraulic control circuit for, for example, working members of earth-moving machines such as backhoe loaders. A first and a second control section (9,10) are coupled to first and second linear hydraulic actuators (1,2; 3-8) through respective first a second hydraulic spool valves (21,22; 23-28), and supply (11) of a hydraulic fluid under pressure is connected in parallel with the two control sections (9,10) via a feed line (13). A load sensing circuit (16) is associated with the first and second spool valves. The control circuit includes a series-parallel connection circuit (36) of the load sensing circuit (16), and additional optional devices ensuring a higher operative functionality of the working members of the machine.

Abstract: A pair of directional control valves 8 and a pair of hold check valves 9 are disposed respectively between a pair of metering notches 6, which are formed in a land 4-1 of a spool 2 and have functions of both flow rate control and direction control, and a pair of actuator ports A, B. Each hold check valve comprises a valve body 90 in the form of a hollow spool having a seat portion 12 formed on an outer periphery and being subject to a pressure developed in an outlet passage 10 communicating with one of the actuator ports to act in the valve-closing direction. Each flow distribution valve comprises a valve body 80 being slidably fitted in the valve body 90 and having a front surface positioned to face an inlet passage 7 communicating with the metering notch and a rear surface positioned to face an control pressure chamber 30 communicating with a signal detecting hydraulic line.

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid from a variable displacement pump to multiple hydraulic actuators. A separate valve section controls the fluid flow between the pump and a different actuator. Each valve section has a pressure compensating valve with a valve member and poppet within a bore and biased apart by a spring. The poppet acts as a check valve which prevents fluid flow from the actuator through the valve section to the pump when the back pressure from the load exceeds the pump supply pressure. A pressure differential between the load-dependent pressure and the actuator pressure determines a position of the valve member which controls the pressure applied to the pump pressure control input.

Abstract: In a hydraulic operating mechanism for a convertible top, a pressure sensor (12) is incorporated into a common pressure circuit (P) of the hydraulic cylinders (1 through 4) and connected with a control unit which is connected to the switching elements (V1 through V4) of the hydraulic cylinders (1 through 4), and its output signal in relation to time, together with the preset switching sequences of the individual switching elements (V1 through V4), serves to control the end positions of the individual hydraulic cylinders (1 through 4). The control can thus be incorporated in the operating mechanism without expensive separate end position switches at each hydraulic cylinder (1 through 4) or appurtenant actuation element, simplifying the overall design.

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid to one or more hydraulic actuators. A remotely located, variable displacement pump provides an output pressure equal to input pressure plus a constant margin. A pressure compensation systems requires that a load-dependent pressure be provided to the pump input through a load sense circuit. A reciprocally spooled, multi-ported isolator transmits the load-dependent pressure to the pump input but prevents fluid in the load sense circuit from leaving the load sense circuit and flowing through a relatively long conduit leading to the remotely located pump. In a multi-valve array, at least one valve section has a backflow-preventing shuttle valve which prevents backflow through the pressure compensation system if a main relief valve is operative.

Abstract: A hydraulic motor system minimizes wasted power by using a plurality of fixed displacement hydraulic motors to drive a drive shaft in a cooperative manner. The motors are selectively switched into operation in response to variations in fluid pressure. As a consequence the hydraulic fluid acts upon a motor system having an effective combined displacement for producing a predetermined shaft rotation rate at the volumetric flow rate which caused the pressure condition. The invention is disclosed as having particular utility for driving a cooling fan for an automotive engine.

Abstract: A direction control valve is formed by providing a main spool for establishing and blocking communication between an inlet port, first and second actuator ports and first and second tank ports. A pressure compensation valve comprising a check valve portion and pressure reduction portion is provided for compensating the pressurized fluid with a load pressure and supplying it to the inlet port. A plurality of valve blocks are connected to each other with respective first and second tank ports and respective pump ports in fluid communication. A pump port of one of the valve blocks is connected to a main inlet port, and a tank port of one of the valve blocks is connected to a main tank port. Thus, a hydraulic circuit for distributing a pressurized fluid from a single hydraulic pump to a plurality of actuators is provided.

Abstract: A one-piece terminal block (73) is provided as a hydraulic linking element as well as a mechanical carrier for control valves (68 to 72) of a boom control unit, for an operating mode selector valve (74), and for switching elements of a pressure supply device (77). A pressure line (119), return line (132), control line (166), and a further return line (167,168) are designed as bores extending in an axial direction of the terminal block, from which connection channels originate which terminate within terminal arrays (163, 163.sup.I to 163.sup.IV) in a bore layout for the valves. Sections (102') of a load feedback line (102), which are serially connectable to each other by comparative valves (114) are formed by individual longitudinal bores (188,188.sup.I to 188.sup.

Abstract: A hydraulic control system for excavators includes a variable displacement pump for producing a variable volume of pressurized working fluid, a hydraulic swing motor rotatably driven by the working fluid and a flow control valve operable to control flow of the working fluid with respect to the swing motor. The first flow control valve comprises a valve body and a valve spool slidably fitted into the valve body for selective shifting movement between a first operative position, a second operative position and a neutral position.

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid to one or more hydraulic actuators. A remotely located, variable displacement pump provides an output pressure equal to input pressure plus a constant margin. A pressure compensation systems requires that a load-dependent pressure be provided to the pump input through a load sense circuit. A reciprocally spooled, multiported isolator transmits the load-dependent pressure to the pump input but prevents fluid in the load sense circuit from leaving the load sense circuit and flowing through a relatively long conduit leading to the remotely located pump. In a multi-valve array, at least one valve section has a backflow-preventing shuttle valve which prevents backflow through the pressure compensation system if a main relief valve is operative.

Abstract: A hydraulic motor system minimizes wasted power by using a plurality of fixed displacement hydraulic motors to drive a drive shaft in a cooperative manner. The motors are selectively switched into operation in response to variations in fluid pressure. As a consequence the hydraulic fluid acts upon a motor system having an effective combined displacement for producing a predetermined shaft rotation rate at the volumetric flow rate which caused the pressure condition. The invention is disclosed as having particular utility for driving a cooling fan for an automotive engine.

Abstract: A control device provides a reliable way of pressure controlling a hydraulic distributor and an associated first hydraulic circuit when pressurized hydraulic fluid is simultaneously supplied to at least one other hydraulic circuit. Pilot pressure oil enters and exits the distributor through inlet and outlet passages in the pilot line. An apparatus for regulating pilot oil flow rate is interposed between the pilot line inlet passage and the hydraulic fluid line. The device includes a pressure head detection apparatus having inlet ends connected to the pilot line inlet passage and to the hydraulic circuit and an outlet end connected to the hydraulic fluid source for controlling the flow rate of the hydraulic fluid based on the highest pressure requirement.

Abstract: An operating valve assembly incorporates a pressure compensation valve and is capable of contributing down-sizing of a hydraulic circuit. The valve assembly includes an operating valve, compensation valves and a load pressure detecting portion. A valve body of the operating valve defines a spool bore extending laterally through the valve body at a vertically intermediate portion of the valve body, a load pressure detecting port at a laterally intermediate portion of the spool bore, and a respective pump port, actuator port and tank port at each side of the load pressure detecting port. The operating valve also includes a spool within the spool bore. The pressure compensation valves are arranged at left and right sides of an upper portion of the valve body and the load pressure detecting portion for supplying load pressure to the load pressure detecting port is formed in the spool.

Abstract: A hydraulic drive system for actuating a reciprocating member such as a polished rod in a pump jack device, and for acting as a counterbalance and/or for energy conservation. The system has two hydraulic circuits and a prime mover. A first circuit includes a cylinder for driving an output member which may be connected to the polished rod, a first pump of the variable displacement, reversible flow type, together with a pair of fluid lines forming with the cylinder a closed-loop circuit. A controller is programmed to control the setting of the first pump so as to establish the velocity profile of the output member. A second hydraulic circuit is also in the form of a closed-loop containing first and second pumps, at least one of which is of the variable displacement type and is also controlled by the controller.

Abstract: Simultaneous operation efficiency in a case where a plurality of actuators are operated by one or a plurality of hydraulic pumps is improved. A delivery pressure passage (1a) of one hydraulic pump (1) and that (1a) of the other hydraulic pump (1) communicate with each other through a first short-circuit passage (39) via a pair of check valves (38, 38), and an unload valve (40) is provided in this first short-circuit passage (39). The load pressure introduction passages (6, 6) on the left and right hydraulic pumps (1, 1) communicate with each other through a second short-circuit passage (36) via a pair of check valves (35, 35), and a relief valve (37) is provided in this short-circuit passage (36).

Abstract: A hydraulic control system is designed to permit the use of a plurality of small substantially identical existing valve assemblies in place of a lesser number of larger valve assemblies. In one embodiment, a first pair of variable displacement load sensing hydraulic pumps communicate with a manifold connected to a first valve assembly and another pair of variable displacement load sensing hydraulic pump communicate with a second manifold connected to second and third valve assemblies. A crossover conduit interconnects the manifolds so that fluid from all four pumps can be used by any one of the valve assemblies or shared by two or all three of the valve assemblies. In another embodiment, a third pair of variable displacement load sensing hydraulic pumps communicate with the first manifold 12 which also has another valve assembly connected thereto.

Abstract: A flow control system is arranged in a hydraulic circuit provided with a variable displacement hydraulic pump, plural actuators and a pump controller. The pump controller controls the displacement of the pump so that a delivery pressure becomes higher by a predetermined value than a maximum load pressure of the plural actuators, whereby the flow rate of pressure oil to the actuators is controlled. The system includes plural valve units connected between the pump and the actuators. Each valve unit has an operating and correcting variable restrictors. The system also includes pressure compensation valves, which are each arranged on an upstream side of a restrictor group consisting of the operating and correcting variable restrictors.

Abstract: Material such as trash or refuse is packed in a container by opposed hydraulic packing and ejecting cylinders. Each cylinder is controlled by a hydraulic control valve with the control valve controlling the ejecting cylinder being, in effect, operated by the control valve for the packing cylinder. This is accomplished by sensing the pressure applied to the packing cylinder and when the pressure reaches a predetermined level, a pilot dump valve, in the ejecting cylinder is opened to allow the piston in the ejecting cylinder to retreat. When the pilot pressure drops below the predetermined level, the pilot dump valve closes, allowing the packing cylinder to exert additional packing force. In this way the piston in the ejecting cylinder inches back and the material is intermittently packed. An anti-cavitation check is provided so as to fill the chamber of the ejecting cylinder as the piston retracts.

Abstract: A hydraulic recovery device in a hydraulic system having a pump (1) driving a plurality of actuators through a plurality of control valves (2, 3), the hydraulic recovery device comprising a variable resistance valve (6, 60) in a first line being controlled by a control signal (Px), a third line, a check valve (7) disposed in the third line for allowing the hydraulic fluid to flow only in a direction from the first line toward the second line.

Abstract: The invention relates to a method for, in a hydrostatic transmission having a preferably variable displacement hydraulic pump (P) feeding a number of hydraulic motors (M1, M2, M3, M4) provided in association with respective drive wheels, drive tracks or corresponding drive apparatus, mutually balancing the flow of hydraulic fluid through the different hydraulic motors (M1-M4) by individually controlling of the flow from and/or to the same, whereby the individual flows of hydraulic fluid through the respective hydraulic motors (M1-M4) are detected and compared across respective restrictions (14, 15) being variable dependent on the total flow but being of mutually equal size and whereby, for optimum control or balancing, the detected differences in flow through the different hydraulic motors are in themselves used directly for the balancing.

Abstract: Hydraulic actuators are fed by a single flow-rate generator, each being connected to it through a proportional directional valve, the unit including at least one auxiliary valve fed by the flow-rate generator and producing a pressure which is normally equal to a regulation pressure increased by a constant, and in each proportional directional valve an actuating device causes the compensating spool to respond to the pressure produced by the auxiliary valve.

Abstract: In a driving mechanism of a circuit breaker having first and second hydraulic operation apparatuses respectively driving a main contact and a resistor contact, a sequential control valve is provided between the first and second hydraulic operation apparatuses. The sequential control valve detects the operation of a differential piston for opening the main contact and switching the differential piston for sequentially opening the resistor contact after the opening of the main contact.

Abstract: A hydraulic circuit for controlling the speed of multiple hydraulic fluid power devices when the flow demand of the devices exceeds the flow capacity of a pressure source supplying hydraulic fluid under pressure to the devices has multiple pressure controlled proportional flow supply valves for controlling the supply of hydraulic fluid to the power devices. Load sense pressures which indicate the pressure delivered by the valves to the corresponding devices are compared to determine the highest load sense pressure, which is compared to the supply pressure by a proportional speed sensing valve to regulate the pilot pressure. In the preferred embodiment, the pilot pressure is regulated by the proportional speed sensing valve to be equal to the differential between the supply pressure and the highest load sense pressure, and a limit control is provided in one form of the proportional speed sensing valve.

Abstract: The flow rate of oil under pressure for operating an attachment for a hydraulic excavator or the like according to the type of attachment is controlled by a simple hydraulic circuit, capable of easily switching the flow rate and also capable of finely adjusting the flow rate. The circuit has directional control valves (2-4, 6-8), pressure compensating valves (17, 18) disposed at outlet ports of each of the directional control valves, load sensing valves (23, 24) for controlling discharges from the variable capacity type main hydraulic pumps (1, 5), and circuits (21, 22) for feeding back the maximum valve of load pressure between each actuator and the associated direction control valve to the pressure compensating valves and the load sensing valves via a shuttle valve (20). A directional control valve (4), which controls the attachment, has a restricting element for restricting an opening area of a spool of the directional control valve.

Abstract: The invention is an improvement in a control system having first, second and third sources of fluid at differing pressures. The improvement comprises a tripath pressure selector network connected to the first and second sources. A pressure-sensing device connects the network and the third source when the third source is at a predetermined minimum pressure. The invention has particular utility in mobile construction machinery having, e.g., steering, implement and brake hydraulic circuits, at differing pressures. In one embodiment, the third source is a brake hydraulic circuit. The improvement helps assure that adequate pilot pressure is available for a "downstream" pilot control valve.

Abstract: A control device for hydraulic operating cylinders of a tailgate of a vehicle to determine maximum pressures arising in the operation and, particularly, overloading of the tailgate, resulting in excessive pressures. A power-driven hydraulic pump (1) is connected to a reservoir (4) and, via branch lines (8', 8"), with associated gate control valves (10, 13) which include a closing cylinder (14) for the tailgate. A pressure intensifier piston-cylinder unit (15) is connected parallel to the branch pipes. An electric pressure-sensitive switch (16), which is also connected to a counter (17) and to an interrupter switch (18) for the electric pump motor, switches off the pump motor (2) when the predetermined pressure is exceeded. This switch is connected to the closing cylinder (14) for the tailgate.