Abstract: A steering angle calculation circuit of an ECU includes a neutral point calculation circuit, a correction amount calculation circuit, an adder, and an absolute angle calculation circuit. When started, the neutral point calculation circuit calculates a motor neutral point from a steering angle detected through a steering sensor and a motor rotation angle detected through a relative angle sensor. The correction amount calculation circuit calculates a correction angle that is a difference between a conversion value and an actual value of the motor rotation angle with respect to the steering angle. The conversion value is obtained by converting the steering angle in terms of the motor rotation angle by taking into account a theoretical specific stroke. The adder calculates a final motor neutral point by adding the correction angle calculated by the correction amount calculation circuit to the motor neutral point calculated by the neutral point calculation circuit.

Abstract: A work vehicle is formed from a plurality of ground-contacting motive elements, a chassis, an operator station, a switch, and a hydraulic manifold. The operator station has a joystick having a manually-actuable control element used to actuate the switch. The hydraulic manifold has a pair of primary hydraulic ports, first and second pairs of secondary hydraulic ports, and a control valve. The control valve is actuated by the switch and is adapted to allow pressurized hydraulic fluid to flow through a selected one of the first or second pair of secondary hydraulic ports. Each pair of secondary hydraulic ports fluidly communicates with a hydraulic actuator carried by a work attachment. By actuating the control element on the joystick, the operator can conveniently switch the hydraulic control of the joystick between different hydraulic operations on the attachment without leaving the operator's station.

Abstract: A pressure-balance valve for balancing the pressures of fluids admitted into the pressure-balance valve via respective second ducts. The pressure-balance valve has both a chamber for guiding movement in translation of a piston, and also fluid flow paths, each comprising a said second duct and a first duct for admitting a fluid coming from the same fluid source as the fluid flowing in its second duct. Each of the first ducts is provided with a shutter co-operating with a ramp arranged on the piston. Movement of the piston in translation as a result of a pressure difference between the fluids respectively admitted into the second ducts causes one of the shutters to slide along the corresponding ramp and consequently allows additional fluid to be delivered from a first duct to the second duct of the same fluid flow path.

Abstract: A control valve apparatus includes a second-working-actuator acceleration control valve connected to a first working control valve in parallel. The second-working-actuator acceleration control valve includes pilot chambers receiving a pilot pressure for switching first and second working control valves and a flow channel that guides a pressure fluid of a first pump port to an entrance port side of the second working control valve. The second-working-actuator acceleration control valve is switchable between a first priority position in which a pressure fluid is guided to the first working control valve with a higher priority than the second working control valve and a second priority position in which a pressure fluid is guided to the second working control valve with a higher priority than the first working control valve.

Abstract: An output system (100) for the extraction and/or output of plural masses (220), comprising a cylinder unit (300) made up of at least two double-acting cylinders (301, 304) each having a piston (303), displaceable by means of a piston rod (302, 305), for extraction and/or output of one of the masses (220) in each case, the piston rods (302, 305) being arranged parallel to one another and being connected to one another via at least one connecting element (307) in such a way that the connected piston rods (302, 305) are displaceable as a unit; and comprising a control unit (200) made up of at least two valves (201, 204) for controlling the entry and return of the masses (220) to the cylinders (301, 304).

Abstract: An actuator control system has a dual concentric servo valve having a spool and at least one motor adapted to selectively displace the spool.

Abstract: A joystick controller is provided in a hydraulic circuit having a pair of hydraulic actuators and oriented with respect to the operator so that movement of a control lever of the joystick controller relative to a reference axis oriented perpendicular to the operator results in control signals being generated and delivered to the first and second main control valves so that the respective cylinders are moved in a direction that is intuitive to the operator. For example, forward movement of the control lever results in both hydraulic actuators moving in the same forward or downward direction and movement of the control lever rearwardly results in both actuators moving in the rearward or upward direction. Likewise, movement of the control lever along an axis that is oriented forty five degrees from the reference axis results in control of one of the actuators independent of the other one.

Abstract: A joystick controller is provided in a hydraulic circuit having a pair of hydraulic actuators and oriented with respect to the operator so that movement of a control lever of the joystick controller relative to a reference axis oriented perpendicular to the operator results in control signals being generated and delivered to the first and second main control valves so that the respective cylinders are moved in a direction that is intuitive to the operator. For example, forward movement of the control lever results in both hydraulic actuators moving in the same forward or downward direction and movement of the control lever rearwardly results in both actuators moving in the rearward or upward direction. Likewise, movement of the control lever along an axis that is oriented forty five degrees from the reference axis results in control of one of the actuators independent of the other one.

Abstract: The invention relates to a hydraulic multiposition valve, in particular a valve for selecting the steering modes of vehicles with multi-axle steering, having one or more position-seat valves (31, 33, 35, 37, 39, 41, 43), which have at least two switching positions and which communicate via lines for the hydraulic medium with one another and with a number of controlled connections (A, B, C, D; L, R) in such a manner that the desired switching positions of the multiposition valve (13) can be selected by the actuation of the seat valves (31-43); and having an actuating arrangement (29) for actuating the seat valves (31-43); the actuating arrangement (29) can be locked in detent fashion in the switching positions of the multiposition valve (13).

Abstract: An improved spring brake actuator includes an improved valve housing which incorporates pressure test points into the air supply, and further incorporates an anti-compounding valve. By incorporating the anti-compounding valve and test points directly into the valve manifold, the inventive spring brake actuator reduces the number of separate parts. The anti-compounding valve is operable to insure that there will be no compounding of the braking force.

Abstract: A hydraulic control for operating an automatic transmission, especially a continuously variable transmission, has at least one first and one second switching component (1, 2) for forward or reverse drive from a neutral position (N) to a drive (D) or reverse (R) position and vice versa. The switching components (1, 2) can be actuated by pressure via pressure lines (24, 25) by a selector slide (15) and by a switching device (26) between the selector slide (15) and the switching components (1, 2) which has a switching valve (27, 28) and a damper, switching and vent valve (29, 30) for a switching component (1, 2). The switching device (26) has a safety and vent device designed in a manner such that when one of the switching components (1, 2) is actuated, the other switching component(s) is/are automatically disengaged.

Abstract: A hydraulic circuit for controlling a plurality of hydraulic motors of a machine has a reversible pump with its suction/pressure ports connected to the inputs of an OR-valve is connected to the input of at least one 3/2 electro-valve, which has its output connected to the inputs of the AND-valves which are not connected to the pump. The AND-valve outputs and the suction/pressure ports are used individually or in combination to control the hydraulic motors.

Abstract: A hydraulic pilot valve includes a valve body, first, second, third and fourth pressure reduction valves formed in the valve body and respectively having, outlet ports, inlet ports and spools for establishing and blocking communication between the ports, and an operation lever pivotally mounted on the valve body and being movable between a neutral position, a first position and a second position. When the operation lever is in the neutral position, the respective spools of the second and third pressure reduction valves are placed at positions establishing communication between the respective inlet port and outlet port. When the operation lever is in the first position, the respective spools of the first and third pressure reduction valves are placed at positions establishing communication between the respective inlet port and outlet port, and in conjunction therewith, the respective spools of the second and fourth pressure reduction valves block communication between the respective inlet port and outlet port.

Abstract: A control and safety system for coordinating movement of multiple hydraulic cylinders to reciprocally rotate a truck-mounted refuse compacting arm. The system includes a logic board controller in communication with a cam and switch arrangement mechanically linked to the rotating arm. Signals from the switches indicate the position of the arm to the logic board which responds by operating directional control valves to regulate movement of the cylinders. A pressure switch is activated to rotate the arm in the opposite direction if the arm is prevented from reaching a limit switch.

Abstract: The present invention includes a single joystick for the simultaneous control of three spool valves for use on a construction machine. A first portion of the joystick is moved in a first direction which causes a cam to selectively depress a first pair of plungers to control the first spool valve. Movement of the first portion in the second direction causes the cam to selectively depress a second pair of plungers thereby controlling the movement of the second spool valve. A handle of a second portion of the joystick rotates about an axis causing a plate to rotate in a corresponding manner. The corresponding rotation of the plate causes a link member to rotate about the axis causing a pair of lugs to selectively depress a third pair of plungers to control the third spool valve. The mechanism for depressing the third plungers works independently of the position of the first portion so that the control of the third spool valve is independent of the control of the first and second spool valves.

Abstract: In a servohydraulic actuator comprising a valve housing, a tandem cylinder, first and second servo valves operating synchronously and in axial alignment with one another in the valve housing and hydraulically connected to the tandem cylinder. Each of the first and second servo valves include an outer sleeve provided with inlet and outlet ducts and a control slide wherein one of the first and second servo valves are displaceable and the other servo valve is stationary. The displaceable valve includes a device for applying a resetting force acting against displacement of the valve. An intermediate sleeve separates the first and second servo valves and includes a coupling rod having an enlarged portion with a transverse opening which extends between and connects the control slides of the first and second servo valves. The actuator also includes an adjustment device for applying an externally controlled axial force against the resetting force to displace the outer sleeve of the displaceable servo valve.

Abstract: A method and apparatus for providing control of multiple actuators with a single control lever is provided. The method and apparatus is adapted for use in an electro-hydraulic system having a microprocessor, multiple actuators, respective electro-hydraulic directional control valves for each actuator, and individual control levers operatively associated with the microprocessor for controlling movement of the respective electro-hydraulic directional control valves. The method and apparatus is accomplished by providing a switch on each of the control levers that is operational to condition the microprocessor to direct simultaneous signals to the respective electro-hydraulic directional control valves to control each of the multiple actuators in proportion to the degree of movement of the one actuator when the switch thereon is depressed.

Abstract: An electrohydraulic steering system has a pair of proportional valves for controlling displacement of a steering valve for normal steering functions. The proportional valves are selectively energized by a position sensor in response to rotation of a steering wheel. However, should an electrical malfunction occur, rotation of the steering wheel beyond the normal operating range causes a steering control member to mechanically move an armature of the proportional valves through a spring to provide mechanical/hydraulic steering. Making the armatures of the proportional valves responsive to a mechanical input through the springs provides a simple, cost effective mechanical/hydraulic backup for the primary electrohydraulic steering control.

Abstract: An interlocking change-over valve system for use in a hydraulically controlled mechanism includes a plurality of hydraulic actuators and at least one valve corresponding to each actuator for controlling the hydraulic pressure supplied to each actuator. A hydraulic cylinder communicates with each valve for opening and closing the valve. A control device remotely activates the hydraulic cylinder to selectively supply hydraulic pressure to some of the hydraulic actuators.

Abstract: The invention relates to a low-vulnerability device for the operation of a lifting and propulsing helicopter rotor by means of a cyclic plate mechanism, in which the non-rotating plate (5) is coupled at four points (1, 2, 3, 4) to four hydraulic actioning servocontrols each comprising a power jack (9), an anchoring system (10) and a servocontrol-distributor (41, 42), three servocontrols being used when normally working, the fourth being used in back-up in the event of a failure of one of the other three. Each power jack (9) is supplied by an independent hydraulic circuit which comprises the servocontrol-distributor (41, 42) operated by a mechanical input, connected to the cockpit by linkage (13), and a disengageable anchoring system.

Abstract: An input apparatus capable of concurrently accommodating itself to any external signal from a different hydraulic control system or the like. The apparatus includes electrical load sensors each arranged on a push rod or block for detecting the amount of operation of a control lever to generate an electrical signal corresponding to the amount of operation of the control lever. Also, an input apparatus which is capable of concurrently responding to both a signal generated by itself and an external signal fed thereto is provided. The apparatus includes a pilot section for exerting force which permits a shuttle to be moved against coiled compression springs. The pilot section is fed with a signal from an external hydraulic control system.

Abstract: An apparatus for controlling the distribution of drive power in a motor vehicle includes a pair of pressure regulating valves, a pair of regulated pressure passages interconnecting the pressure regulating valves, respectively, and torque transmission clutches which transmit drive power to a pair of drive wheels, and a shut-off valve mechanism disposed between the regulated pressure passages for selectively bringing the regulated pressure passages into and out of each other.

Abstract: A multiplexed hydraulic control system having a plurality of channels and a common source of modulated hydraulic fluid. The common source is shared among the plurality of channels by providing a plurality of selector valves, one for each channel, with electrical solenoids for the selector valves being individually controlled by a control means. In a normal operating mode, the selector valves are operated individually and the modulating means is controlled to direct fluid to the selected channel in accordance with the demands placed on movement of the actuator in that channel. In a second slewing mode, multiple selector valves are energized at the same time and the modulator is controlled to produce sufficient fluid flow to slew all of the actuators in the selected channels at a desired rate.

Abstract: A vacuum brake power booster for a slip-controlled hydraulic brake unit in which a major reduction of the costs of manufacture and of mounting and simultaneously an increase of its reliability in operation is provided. A first movable wall (7) within the booster housing is movable independently of the brake pedal input member (11) and a second movable wall (15) is provided at the first control housing part (52).

Abstract: A dual hydraulic motor system where motor wobblers are mechanically linked and the motor outputs are torque summed, is controlled by a three position dual valve assembly. Each valve assembly is controlled by pilot pistons that are mechanically linked to provide three functions, one being normal operation, a second where one motor must be shut-off and its load on the system is minimized and the third where both motors are shut-off and significant drag is then provided. These functions are implemented by a separate spool in each valve which has three independent stable positions.

Abstract: A slurry pump has slurry hopper and dual pumping cylinders. The slurry pumping members are driven by opposite-phase actuators. Each actuator has a rigid-hollow-stem partition dividing the space between the actuator plunger and the cylinder into two drive chambers of different areas selectively supplied with pressurized fluid to drive the plunger with a selected force and speed. An associated valve shuts off flow to one of the drive chambers and is controlled at any given time to occupy the same position as a corresponding valve of the other actuator. The valves coordinate supply of fluid to corresponding drive chambers on alternate strokes of two actuators.

Abstract: A pump supplies via in each case a directional valve a plurality of consumers with fluid, a pressure balance for load-independent division of the pump displacement being provided between each branch line branching off the pump delivery line and the directional valve. In a pressure regulating valve common to all pressure balances a control pressure is generated from the pressure difference between the pump pressure and the respective highest consumer pressure and is applied to all the pressure balances so that when the pump power is inadequate a proportional quantity reduction at all consumers is achieved.

Abstract: A hydraulic drive system for a counterweight dolly in a counterbalance type crane having a crane body provided with a lower travelling structure an upper swivelling structure and the counterweight dolly connected to the rear portion of the upper swivelling structure through a connecting member, characterized by including a swivelling hydraulic motor for swivelling the upper swivelling structure of the crane body; a swivelling control valve for controlling the pressure of hydraulic oil to be fed to the swivelling hydraulic motor; a hydraulic circuit for swivelling operation which controls the amount of operation of the swivelling control valve; a hydraulic motor for the counterweight dolly which drives each wheel of the dolly; a dolly control valve for controlling the pressure of hydraulic oil to be fed to the hydraulic motor for the counterweight dolly; and a control circuit for actuating the dolly control valve in accordance with an operational pressure of the hydraulic circuit for swivelling operation and t

Abstract: A servoactuator unit to operate flight-control mechanisms, in particular for control of the position of the oscillating plate which adjusts the cyclic pitch and collective pitch of helicopter rotors, in which two pairs of hydraulic actuators are used, connected together in parallel, arranged with their axes parallel and close together like the diagonals of a quadrilateral, their rods connected together at their end and acting on the said oscillating plate and the cylinders also being connected together at the back. Each pair of actuators is powered, through a servovalve, by an independent hydraulic circuit so as to enable operation even in the event of one of the pairs breaking down, with symmetrical stress being placed on the pair of actuators during operation.

Abstract: A power assisted steering system and a steering assembly for such a system. The steering assembly has a steering output comprising an arm 6 displaceable through a toothed sector 7 by a racked piston nut 3 drivingly engaging a worm shaft 7 rotatable by a steering input shaft 12. The piston 3 and its cylinder 2 provides a first servomotor for power assisting the steering output. The first servomotor is powered by a first hydraulic system 16 comprising a rotary valve 10 which is responsive to the steering input to control fluid pressure to the first servomotor. The steering system also includes a second hydraulic system 25 comprising an axially responsive spool valve 21 which controls fluid pressure to operate a second servomotor 28 coupled to the steering output arm 6. The rotary and axially responsive valves 10 and 21 are axially coupled together by the shaft 7 which is axially displaceable to control operation of the valve 21.

Abstract: A fluid control system (10) for selectively controlling two independent actuators or clutches (12, 14) has a pair of normally opened solenoid valves (62, 64) for controlling fluid pressure in a pair of actuating chambers (40, 42). This controls actuation of a pair of directional spools (36, 38) which in turn controls engagement and disengagement of the clutches (12, 14) such that failure of one of the solenoid valves to close properly would not allow engagement of the clutches. A common actuating chamber (44) is provided between the directional spools (36, 38) and in fluid communication with the first and second actuating chambers (40, 42) through orifices (58). The abutment of the first and second directional spools prevents simultaneous engagement of both clutches.

Abstract: A hydraulic drive system for civil engineering and construction machinery in which at least first and second hydraulic circuits having at least first and second hydraulic pumps, respectively, are provided for driving a plurality of actuators such as left and right travelling actuators, a boom actuator and an arm actuator. The first circuit includes a first travelling directional control valve for one of the left and right travelling actuators located downstream of a first boom directional control valve for the boom actuator and a first arm directional control valve for the arm actuator that the latter to receive a hydraulic fluid supply from the first pump by taking priority over the first travelling valve.

Abstract: Pipe thrust-jacking apparatus includes a pressure ring 5 which is advanceable by a plurality of hydraulic rams 3. The rams are controlled by hydraulic control means having a plurality of hydraulic control valves 19. Each control valve is associated with a respective hydraulic ram, and is connected to a first input line and to a second input line. Each of the first input lines is connected to a respective hydraulic fluid feed line 9, and each of the second input lines 17 is connected to a common hydraulic fluid supply line 11 and to an auxiliary pump P2. The common supply line is connected to all of the feed lines. Means 12,15 are provided for selectively connecting each of the hydraulic control valves to its first input line and/or its second input line.

Abstract: A hydraulic fluid circuit of a hydraulic shovel including a first directional control valve group connected to a first hydraulic pump and including a first directional control valve and a second directional control valve respectively connected to a first hydraulic cylinder and a second hydraulic cylinder. A second directional control valve group, connected to a second hydraulic pump, includes a third directional control valve having a first working port connected to one cylinder chamber of the first hydraulic cylinder and a second working port connected to one cylinder chamber of the second hydraulic cylinder.

Abstract: The present invention relates to a device for controlling two fluid-controlled drive members, one of which is double-acting, wherein a communication conduit connects the supply conduits of said double-acting drive member, a non-return valve being disposed in said communication conduit and allowing the passage of the fluid solely from the small chamber towards the large chamber of said double-acting drive member, while another conduit is adapted to connect the large chamber of the double-acting drive member to the chamber of the second drive member. The result of the invention is the elimination of lift of a hydraulic loading shovel when digging.

Abstract: A control system for a plurality of hydraulic actuators which requires smaller number of control valves than that of actuators. In one embodiment, three control valves are arranged in parallel for controlling four hydraulic cylinders. The control valves are preferably solenoid-operated and one of control valves are used for supplying a pilot fluid pressure into a plurality of pilot-operated check valves disposed between the control valves and the hydraulic cylinders.

Abstract: An electro-mechanical direct drive valve servo system for an aircraft including a drive mechanism that couples the rotary output motion of a rotary force motor to linear motion at a sliding-type valve. The drive mechanism includes a pair of axially spaced rotary members connected to the force motor and a wobble member journaled between and canted by the rotary members with axial thrust bearings interposed between axially aligned opposed planar faces of the rotary and wobble members. A radial output arm on the wobble member is connected to the valve and is constrained for arcuate nutating movement whereby controlled rotation of the rotary member effects nutating movement of the wobble member and output arm which movement effects controlled linear movement of the valve. Additional control inputs such as braking and recentering function inputs are accommodated by the drive mechanism at its input end to take advantage of the mechanism's inherent gearing force ratio.

Abstract: A power steering gear assembly having a single control valve suitable for use in a single circuit type of power steering system, may be simply converted to use in a two-circuit type of power steering system by replacement of the steering spindle and the addition of a housing extension enclosing a second control valve formed on the replaced steering spindle. Both control valves include portions of the common steering spindle and control sleeves rotatable thereon, with one of the control sleeves being formed in one piece with the worm shaft of the steering gear assembly.

Abstract: A load check valve is normally employed in association with a double-acting hydraulic cylinder, such as the type used to raise and lower the boom of a construction vehicle. Conventional check valves of the poppet type are difficult to modulate whereas check valves of the spool type generally do not insure leakage control at an acceptable rate during normal operation. The spool-type load check valve (20) of this invention, used in conjunction with additional check valves (60,61), overcomes the latter problem by providing a series of interconnecting passages and chambers (36) for communicating equalized fluid pressure from a cylinder (11) to either end of the spool (27) thereof to provide for minimal leakage.

Abstract: The steerable wheels of a hydraulically driven vehicle are provided with fixed displacement type auxiliary motors which are connected in parallel both with each other and with the motor which powers the main drive wheels. A selector valve permits the motors for the steerable wheels to be optionally connected and disconnected from the reversible, variable displacement main pump. Flow dividers in the hydraulic lines limit the maximum flow of fluid to any one auxiliary drive motor. To prevent large power losses when the steerable wheel assist mode is not being utilized, the selector valves are placed in close proximity to each fixed displacement motor. This allows the motors to circulate large quantities of fluid around a closed loop at minimum pressure drop.

Abstract: A fluid power device such, for example, as one for opening and closing clam shell gates is operated by a ram under fluid pressure. A tank is provided for storing fluid under pressure and by a system of valving extension of the ram, as for a gate opening operation, is inhibited until enough fluid under pressure is stored in the tank to assure completion of reverse operation of the ram to close the gates.

Abstract: A multiple servo system including two or more servo mechanisms, each having a pressure feed back including two pistons exposed in respective chambers interconnected by a low-pass hydraulic filter, in which the area of the two feedback piston faces differ by up to 25%. This reduces the tendency of the respective actuators to act in opposition and thus increases the service life of the system.

Abstract: A fluid system has at least first and second circuits, each connected to a pressurized fluid source. Each circuit has at least one preselected work element connected to the fluid source through a respective preselected controlling valve. A blocker valve is connected to one of the circuits and has an actuating assembly and is of a construction sufficient for controllably passing fluid from a preselected location on one of the circuits to a preselected location on the other circuit.