Abstract: The invention relates to an industrial truck (2) with a lift mast (4), a hydraulic system (10) as well as a method for operating a hydraulic system (10). The lift mast (4) of the industrial truck (2) is driven by a mast lift cylinder (12) and comprises at least one mast lift stage (42, 42). Furthermore, a free lift stage is present that is driven by a free lift cylinder (8) with which a load receiving means (6) can be displaced along the lift mast (4). The industrial truck (2) comprises a hydraulic system (10) for supplying the at least one mast lift cylinder (12) and the at least one free lift cylinder (8) with a hydraulic fluid (14), wherein the hydraulic system (10) is configured to at least at times simultaneously actuate the at least one mast lift cylinder (12) and the at least one free lift cylinder (8) in load lifting operation and/or in load lowering operation.

Abstract: Systems, apparatus, and methods to control fluid associated with vehicle clutches are disclosed. A disclosed apparatus includes a drive unit assembly for a vehicle. The drive unit assembly includes a housing and a clutch in a cavity of the housing. Rotation of a drum of the clutch expels a fluid from the cavity. The apparatus also includes a vehicle controller configured to disengage the clutch via an actuator. Actuation of the actuator reduces a flow of the fluid into the cavity. The vehicle controller is also configured to maintain engagement of a vehicle transfer device operatively coupled between a vehicle transmission and the drum such that the drum continues to rotate for a time interval during which the clutch is disengaged.

Abstract: A lifting device for an industrial truck comprises a lift frame with a moveably guided load carrier and at least one moveably guided mast stage. A free lift cylinder is configured to actuate the load carrier and at least one mast lift cylinder is configured to actuate the at least one mast stage. A hydraulic assembly supplies the free lift cylinder and the at least one mast lift cylinder with hydraulic fluid and further comprises at least one delivery valve and at least one recirculating valve.

Abstract: An apparatus for actuating a valve includes an actuator with a cap. A plate that engages the inner diameter of the actuator housing is positioned within the actuator housing. A pressure chamber is located within the actuator housing between the plate and cap. A cap seal fluidly seals the pressure chamber between the cap and the actuator housing. The pressure chamber is fluidly sealed at the plate by one of a first plate seal assembly and a second plate seal assembly. The first plate seal assembly is formed by the diaphragm being secured between a seal nut and the plate. The second plate seal assembly is formed by an outer diameter sidewall seal located between the inner diameter of the actuator housing and the outer diameter of the plate and a retainer seal located between an outer diameter of the seal nut and an inner diameter of the plate.

Abstract: An apparatus for use in turning steerable vehicle wheels includes a power steering motor assembly connected with the steerable vehicle wheels. A first pump connected with the power steering motor assembly is continuously driven by an engine of the vehicle to supply fluid under pressure to the power steering motor assembly. A second pump connected with the power steering motor assembly is continuously driven by an engine of the vehicle. A valve connected with the power steering motor assembly and the second pump directs fluid flow from the second pump to at least one of the power steering motor assembly and reservoir during operation of both the first pump and the second pump. A pumping mechanism includes a first pumping area defining the first pump and a second pumping area defining the second pump. The first pumping area is smaller than the second pumping area.

Abstract: The operability when performing a combined arm-crowd and bucket operation can be improved. A hydraulic drive device for a hydraulic excavator includes: a bucket directional control valve and a second arm directional control valve, which are connected in parallel tandem with a first hydraulic pump; a first arm directional control valve that is connected to a second hydraulic pump; and a flow rate restriction device that restricts the flow rate of pressure oil supplied to the second arm directional control valve, during crowd operation of a bucket. This flow rate restriction device includes a variable throttle whose opening is controlled so as to become smaller as a bucket operating device is operated to the crowd side, the variable throttle being provided in a bypass path connecting to the supply port of the second arm directional control valve.

Abstract: In a hydraulic excavator, a hydraulic cylinder drives a boom via a hydraulic fluid discharged from a first hydraulic pump. A first hydraulic circuit connects the first hydraulic pump and the hydraulic cylinder and forms a closed circuit therebetween. A hydraulic motor rotates a revolving upper unit with hydraulic fluid discharged from a second hydraulic pump. A second hydraulic circuit independent from the first hydraulic circuit connects the second hydraulic pump and the hydraulic motor. A motor hydraulic pressure reduction unit reduces the driving hydraulic pressure of the hydraulic motor when a predetermined condition is satisfied. The predetermined condition is a condition in which an operation of the boom operating member to raise the boom and an operation of the rotation operating member to rotate the revolving upper unit are conducted together and an operation amount of the boom operating member is equal to or greater than a predetermined threshold.

Abstract: The invention provides a method of operating an energy extraction device such as a wind turbine comprising a hydraulic pump driven by and applying torque to a rotating shaft, a hydraulic motor driving a load, a high pressure manifold in fluid communication with an outlet of the hydraulic pump and an inlet of the hydraulic motor and being selectively placed in fluid communication with a fluid accumulator, at least one low pressure manifold in fluid communication with an outlet of the hydraulic motor and an inlet of the hydraulic pump, at least one of the hydraulic pump or hydraulic motor is a digital hydraulic machine, characterised by interrupting fluid communication between the fluid accumulator and the high pressure manifold responsive to detection of a fault event.

Abstract: A valve device for a hydraulic circuit (10) divides the incoming volume flow into at least two pre-determined partial flows for supplying hydraulic consumers (V1, V2) of the circuit (10) and has at least one pressure balance (16) and at least one orifice. Since the orifice is embodied as a variable orifice (32) controllable by a proportional magnet (34), the opening area of the orifice varies. A flow regulator is then realized and can switch the regulated volume flow and/or proportionally adjust the regulated volume flow in a defined manner.

Abstract: According to the present disclosure, a hydraulic control apparatus for construction machinery comprises: hydraulic pumps; first and second control valve units which control the flow directions of working oil discharged from the hydraulic pumps to supply the working oil to first and second work machines, respectively, and which control the degree of opening of flow channels which interconnect the first and second work machines and the hydraulic pumps, respectively; and a control unit which controls the first and second control valve units in accordance with operating signals inputted from first and second operating units.

Abstract: Hydraulic valve circuits capable of variably limiting respective maximum hydraulic pressures at which an assembly of bidirectional hydraulic power devices can move respective clamping members, such as forks or clamp arms, selectively in a closing movement toward each other, in an opening movement away from each other, or in a side-shifting movement in unison with each other, so as to provide damage-control capabilities for the control of the clamping members. The circuits preferably include one or more pressure-regulating valves interconnected with the assembly of power devices, and capable of variably limiting a maximum side-shifting pressure, at which said assembly can cause said side-shifting movement, in response to a maximum pressure selection. The circuits preferably include at least one override assembly, capable of overriding the maximum pressure selection to thereby lower the maximum side-shifting pressure automatically irrespective of the maximum pressure selection.

Abstract: A pneumatic drive system (1) in which the movement of an output drive unit (7) of a pneumatic drive (2) is controlled by control valve means (25 and 26) which are connected with the working chambers (12 and 13) of the pneumatic drive (2). The control valve means (25 and 26) comprise at least one air economy setting (30) setting a choke cross section and a high power setting (29) defining a flow cross section larger than it. Actuating means (12 and 13) serve to ensure that the control valve means (25) are switched over, in a fashion dependent on the air pressure obtaining in the at least one working chamber (12 and 13) from the normally assumed air economy setting (30) into the high power setting (29), when the output drive unit (7) meets with an increased resistance to motion.

Abstract: What is disclosed is a hydraulic controller arrangement for the pressure medium supply of a hydraulic consumer, e.g., of the rotating gear of a mobile work machine. At low pressure medium flow rates, the pressure medium flow rate draining from the consumer is backed up by means of a drain backup valve having the form of a pressure limiting valve and throttled accordingly, so that a back pressure is generated which is capable of preventing an advance of the mass actuated by the hydraulic consumer.

Abstract: A hydraulic control system in which a pump for pressurized hydraulic fluid connects with a valve assembly having a valve element displaceable in a chamber to selectively direct fluid to a load driven by the hydraulic system. Surfaces on the end faces of the valve element are exposed to hydraulic pressure from a controller via electro-hydraulic solenoid valves. The surfaces of the valve element adjacent the end faces are undercut to establish a leakage flow path and the solenoid valves are selectively actuated to pressurize the end faces to a level below normal actuation of the valve element but high enough to cause fluid to return to a drain and thus increase the temperature of the hydraulic fluid in the system.

Abstract: Disclosed are a control arrangement and a method for the pressure medium supply of at least two hydraulic consumers that are supplied with pressure medium through the intermediary of a variable displacement pump. In the pressure medium flow path between the consumers and the variable displacement pump a respective meter-in orifice is provided. An adjustment of the variable displacement pump and of the meter-in orifices takes place electronically through the intermediary of a control means in dependence on the target values input by an operator. In accordance with the invention, the meter-in orifice associated with the consumer having the highest load pressure is controlled to open completely, so that the pressure loss across this meter-in orifice is minimum.

Abstract: To permit using hold-side pressure oil in a first hydraulic cylinder for the acceleration of a second hydraulic cylinder upon performing a combined operation of the first and second hydraulic cylinders, a hydraulic drive system is provided with a main hydraulic pump 21, a boom cylinder 6 and an arm cylinder 7, a directional control valve 23 for a boom and a directional control valve 24 for an arm, and a boom control device 25 and an arm control device 26. The hydraulic drive system is also provided with a pressure oil feed means for feeding pressure oil in a rod chamber 6b of the boom cylinder 6 to an upstream side of the directional control valve 24 for the arm when a bottom pressure of the arm cylinder 7 has increased to a high pressure equal to or higher than a predetermined pressure. This pressure oil feed means includes a flow combiner valve 44 arranged in a reservoir line 42 which can communicate to the rod chamber 6b of the boom cylinder 6.

Abstract: Apparatus for providing actuation power to an aircraft flight control surface. The apparatus includes a first actuator and a second actuator, where the second actuator has a bypass mode and an assist mode. The mode of the second actuator is determined by an internal differential pressure across the first actuator. The apparatus further includes a mode select valve for selecting between the bypass mode and the assist mode for the second actuator, and a solenoid valve that when energized causes the mode select valve to select the other mode for the second actuator. When the second actuator is in the bypass mode, the first actuator provides the actuation power for the aircraft flight control surface. But, when the second actuator is in the assist mode, both the first and second actuators provide the actuation power for the aircraft flight control surface. Accordingly, the apparatus allows the flight control surface to be operated in a more efficient manner with less hydraulic flow being required.

Abstract: A hydraulic circuit comprises first and second cylinders, and a piston disposed in each of the cylinders. A pump communicates with one side of one of the pistons, and a pressure relief valve has a position wherein the pump communicates with another side of the one piston and with the other piston.

Abstract: A preventative stop valve system for a wheeled trailer carrying hydraulic equipment is disclosed comprising a stop valve fitted for insertion in-line into the hydraulic line servicing the trailer equipment; the stop valve comprising a reciprocating piston moveable between open and closed positions. The stop valve is connected to the pressurized air line extending to the air brakes of the trailer. Actuation of the stop valve is controlled pneumatically by the setting and release of the air brakes of the trailer by the operator, utilizing conventional controls for the air brakes. A manual override mechanism is further provided for opening the stop valve manually in the event that the hydraulic equipment carried by the trailer must be utilized when pressurized air line to the trailers is disconnected.

Abstract: An ejector truck requires an ejector mechanism to remove hauled material from the ejector truck body. Often, these ejector mechanisms are costly and require precise manufacturing and maintenance because they include a telescoping linear actuator. The present invention provides a method and apparatus of a multi-actuator ejection mechanism. The multi-actuator ejection mechanism includes an anchor member, an ejection carriage, an ejector blade, a first linear actuator, and a second linear actuator. The ejector blade is located a predetermined distance from the anchor member and is adapted to move longitudinally with respect to the anchor member. The first linear actuator has a first end secured to the anchor member and a second end secured to the ejection carriage, and is adapted to move the ejection carriage longitudinally with respect to the anchor member.

Abstract: In the operation of a work machine attachment of the type utilizing fluid cylinders, it is desirable provide a way to conveniently operate each of the fluid cylinders while locating any hydraulic conduits required to operate the fluid cylinders away from the operator cab. The present invention provides for a hydraulic positioning system for use with a work machine attachment of the type having a frame, a tool, and a plurality of fluid cylinders coupling the tool with the frame. A fluid deflection device is coupled to at least one fluid cylinder and is in fluid communication with an auxiliary hydraulic circuit having a fluid source. A primary hydraulic circuit is in fluid communication with the fluid deflection device and operable to selectively deflect the fluid source of the auxiliary hydraulic circuit to at least one of the fluid cylinders.

Abstract: A first object of the present invention is to make do with a simple hydraulic circuit, which does not utilize a pressure compensation valve, and to enable the use of an inexpensive, low-precision pressure detector, to enable the maintenance of continuous control at all times using simple controls, and to get by without shocking the operator or the mechanical parts, and to cancel the load dependency of a hydraulic actuator flow during combined operation without limiting the control system of the hydraulic pump. In a device according to the present invention, a correction factor for correcting a control input of a operating member corresponding to a pertinent operating valve is calculated for each operating member on the basis of a ratio between a detected differential pressure across an operating valve, and a minimum differential pressure selected from among detected differential pressures across a plurality of operating valves.

Abstract: The invention relates to a control device for hydraulic power cylinders, in particular power cylinders of a road truck tailgate, comprising a hydraulic pump (1) driven by a motor (M). Said pump can be connected to a supply of medium and, via pump branch pipes, to a chamber of the operating cylinder (14) by means of allocated control valves (12,13). An adjustable electrical pressure gauge and switch unit (15-18) is connected to the chamber or corresponding pump branch pipe of the power cylinder. Said unit is fitted with a computer (15) for entering maximum pressure limits and used to stop the pump motor drive (2, 19) and activate a signal transmitter (20) when a preset maximum pressure is exceeded. In addition, a safety valve (22) set at a cut-in pressure lower than the preset maximum pressure is connected to the chamber or corresponding branch pipe (8″,A,B) via an electromagnetic valve (23) which opens when the device is not operating.

Abstract: A first object of the present invention is to make do with a simple hydraulic circuit, which does not utilize a pressure compensation valve, and to enable the use of an inexpensive, low-precision pressure detector, to enable the maintenance of continuous control at all times using simple controls, and to get by without shocking the operator or the mechanical parts, and to cancel the load dependency of a hydraulic actuator flow during combined operation without limiting the control system of the hydraulic pump. In a device according to the present invention, a correction factor for correcting an control input of a operating member corresponding to a pertinent operating valve is calculated for each operating member on the basis of a ratio between a detected differential pressure across an operating valve, and a minimum differential pressure selected from among detected differential pressures across a plurality of operating valves.

Abstract: A hydraulic device comprises a variable displacement pump, a plurality of hydraulic actuators, a plurality of directional valves capable of controlling the delivery oil flowing into each of the actuators, a plurality of pressure compensation valves which compensate the pressures of respective directional valves, and a delivery oil flow rate varying means capable of controlling the pump delivery. At least one of the pressure compensation valves decreases its output flow to a particular actuator according to an increase in the loaded pressure of the particular actuator. With this arrangement, if the loaded pressure of the particular actuator suddenly changes, the loaded pressure attenuates to ensure stable operation of the hydraulic device. Further, the stable operation is fee of hunting for both low-load actuators and high load actuators, regardless of an independent operation or a compound operation.

Abstract: The present invention relates to a hydraulic circuit for a hydraulically driven working vehicle which allows the vehicle to travel at an almost constant speed during high-speed traveling, provides a great digging force during working, does not need a charging pressure for preventing cavitation, loses a small amount of energy, and has a simple structure. To this end, the hydraulic circuit has a hydraulic travel pump (2) and a working machine hydraulic pump (4) which are driven by the power of an engine (1) for discharging pressurized oil to a HST travel circuit and a working machine-driving hydraulic circuit, respectively, wherein pressurized oil from the working machine hydraulic pump (4) joins pressurized oil from the hydraulic travel pump (2) to effect high-speed traveling, while pressurized oil from the hydraulic travel pump (2) joins pressurized oil in the working machine hydraulic pump (4) to generate a large digging force to effect digging.

Abstract: A hydraulic emergency control system for a continuous looped gear type continuously variable transmission (10) includes first and second hydraulic beveled conical pulley axial actuators controlling a gear ratio. A pump supplies a first piston chamber (13) of said first axial actuator via a sensor valve (20), wherein the sensor valve (20) is controlled by a flow control valve (73) connected downstream of the pump (80). The pump (80) supplies a second piston chamber (17) of the second axial actuator, with a pressure relief valve (40) limiting fluid pressure in said second piston chamber. Fluid in the second piston chamber (17) is controlled as a function of the fluid pressure in the first piston chamber (13) via a control line (52, 113).

Abstract: A lift having a freight-receiving table which is rotatably supported by one or more each of hydraulic lift and tilt cylinders for respectively lifting and tilting the table is controlled such that an overloaded condition of the table is detected by measuring the internal pressure of the tilt cylinder or both the tilt and lift cylinders. If the measured pressure exceeds a pre-determined critical value, the operation of the lift is automatically and immediately stopped.

Abstract: An aerial lift unit is truck mounted. The lift includes a lower boom pivoted to the truck and an upper boom pivotally connected to the outer end of the first boom. A lower boom cylinder unit is connected to pivot and thereby raise and lower the lower boom. A second tandem cylinder unit consists of first and second cylinders with the head end interconnected and having cylinder rods extending coaxially outwardly from the opposite rod ends. The one cylinder rod is connected to the lower boom and the second piston rod is connected to the base of a V-shaped coupling member having one arm pivotally connected to the lower boom and a second arm is pivotally connected to the upper boom. The second cylinder positions the upper boom in a preset orientation with respect to the lower boom. The first cylinder is connected in a hydraulic supply circuit with the lower boom cylinder and with the hydraulic fluid flow serially through the lift cylinder and second cylinder.

Abstract: A hydraulic control apparatus having two groups and formed by combination of actuator circuits on large flow rate side (a boom cylinder circuit and an arm cylinder circuit) and actuator circuits on small flow rate side (a bucket cylinder circuit and a rotating motor circuit), for independent supply of hydraulic fluid. In these groups, a bucket preferential valve and a rotating preferential valve form bucket cylinder preferential and rotating motor preferential circuit constitutions.

Abstract: A pressurized fluid feed system including a pressure compensating valve and directional control valve disposed between a hydraulic pump and a boom cylinder, and a pressure compensating valve and a directional control valve disposed between the hydraulic pump and a turning motor. Each pressure compensating valve comprise a check valve section and a pressure reduction valve section. The check valve section has an inlet port connected to the said hydraulic pump, an outlet port connected to the directional control valve, a spool for establishing and blocking communication between the inlet and outlet ports and a pressure chamber for applying pressure to the spool. The pressure reduction valve section has a first port connected to the said hydraulic pump, a second port connected to a reservoir, and a spool for establishing and blocking communication between the first and second ports.

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: 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 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 system is provided for a hydraulic circuit having first and second hydraulic valves, a valve spool position sensor, and first and second input devices for producing first and second operation signals. A controller receives a signal from the valve spool position sensor and the second operation signal and responsively modifies the value of the second operation signal in response to the valve spool position signal.

Abstract: A control arrangement for at least one hydraulic consumer in which the consumer can be controlled with respect to direction and speed via a directional control valve device, in which two consumer lines lead from the directional control valve device to the consumer, each of which consumer lines can be connected to a pump and a tank respectively via a directional control valve piston and a metering restrictor and in which a throttle valve having a servo-piston is associated with each consumer line. The consumer is to be held free of leakage oil in a given position.

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 pressurized fluid supply system, in which a plurality of pressure compensation valves are connected to a pump discharge line of a hydraulic pump in parallel, and direction control valves are provided at the outlet side of each pressure compensation valve to supply a discharged pressurized fluid from the hydraulic pump to a plurality of actuators. The pressure compensation valves include a check valve portion establishing and blocking communication between the pump discharge line and the inlet port of the direction control valve, and a pressure reduction valve portion for supplying a reduced pressure from the pump discharge line. The check valve portion shifts in a valve opening direction in response to an inlet pressure and shifts in a valve closing direction in response to an outlet pressure. The pressure reduction valve portion has a first and a second pressure chamber.

Abstract: A load sensed variable output gear pump system including a pump within a housing, an inlet passage extending to a pump inlet and an outlet passage extending from a pump outlet. A secondary outlet passage is located in the housing and a bypass outlet passage is located in the housing and is connected to a reservoir. A load sensed passage is located in the housing and is connected to load pressure. First and second independent control devices are provided for controlling flow through the secondary outlet passage from the outlet passage.

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: In a hydraulic circuit system, when pressurized oil discharged from a single hydraulic pump is supplied to a plurality of actuators: the pressurized oil is supplied to heavily-loaded ones of the actuators at gradually reducing flow rates to reduce a shock, while supplied to lightly-loaded ones of the actuators at gradually increasing flow rates to increase working speeds of these lightly-loaded actuators. The hydraulic circuit system comprises a plurality of directional control valves (2) one of which is provided with pressure-compensated flow control valves (18) each of which is provided with a load lead-in passage having a restriction means (R). In addition, further comprised in the system are: relief valves (22, 22) for relieving the pressurized oil under the influence of load pressure of the actuators (3) operated by the directional control valves (2); a restriction orifice (24) provided in a drain side of each of the relief valves so as to produce pressure therein.

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: 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: A hydraulic drive system for hydraulic working machines has a variable displacement hydraulic pump, at least one actuator driven by the hydraulic fluid, a directional control valve of center bypass type for controlling the flow of the hydraulic fluid, a center bypass line for connecting the center bypass passage of the control valve to a reservoir and a fixed restrictor disposed in the center bypass line. A first control signal that determines a first target displacement of the hydraulic pump is determined by using the pressure generated by the fixed restrictor. A second control signal is generated for determining a second target displacement of a hydraulic pump. A third control signal, which is the larger one of the first and second control signals, provides a target displacement that is applied to a pump regulator that controls the displacement of the hydraulic pump.

Abstract: Hydraulic actuators are fed by a single flow-rate generator, each being connected to it through a proportional directional valve, the unit including a device for detecting the highest of the pressures prevailing upstream of the throttle provided by a controlled spool in the respective proportional directional valves, and, in each of these an actuation device to cause the compensating spool to respond to the highest of the upstream pressures thus detected.

Abstract: A fluid pressure driving system for a vehicle includes a reservoir tank in which an amount of fluid is stored, a variable capacity oil pump sucking the fluid from the reservoir tank and discharging the resultant fluid, a control device for adjusting a quantity of the fluid discharged from the variable oil pump, and a distributor valve having an inlet port for receiving the fluid from the variable capacity oil pump. The distributor valve discharges a fixed amount of the fluid and the remaining amount of the fluid from a first outlet port thereof and a second outlet port thereof, respectively. A first passage connects the first outlet port of the distributor valve and the reservoir tank. A second passage connects the second outlet port of the distributor valve and the reservoir tank. A power steering device is associated with a steering wheel and disposed in the first passage. A hydraulic motor is disposed in the second passage, and a cooling fan is mounted rotatably on the hydraulic motor.

Abstract: An unloading valve is connected to a hydraulic pump, the unloading valve being opened when a differential pressure between a delivery pressure of the hydraulic pump and a maximum load pressure exceeds a predetermined value, for discharging a part of a flow rate of a hydraulic fluid delivered from the hydraulic pump to a reservoir. A fixed restriction for generating a control pressure corresponding to the flow rate of the hydraulic fluid discharged through the unloading valve is connected downstream of the unloading valve. A control device for the hydraulic pump is constructed to reduce the delivery rate of the hydraulic pump as the control pressure generated by the fixed restriction is raised, and increase the pump delivery rate as the control pressure is lowered.