Abstract: A hydraulic actuator control circuit capable of increasing the flow rate of the working fluid supplied to hydraulic actuators when the load on the hydraulic actuators increases beyond predetermined values includes a first valve group having a plurality of pilot controlled selector valves connected, respectively, to hydraulic actuators, a second valve group having a plurality of pilot controlled selector valves connected, respectively, to lines connecting the hydraulic actuators to the pilot controlled selector valves of the first valve group, two hydraulic pumps connected, respectively, to the first and second valve groups, and a tank for containing working fluid.
Abstract: An article handling apparatus is disclosed which comprises two independently controllable fluid actuated drives. The first fluid actuated drive comprises a cylinder and a differential piston which defines a large chamber and a smaller chamber. Also, a control system is provided which maintains a differential pressure between the large and small chambers in each of several operating positions. The second fluid actuated drive is mounted to the movable member of the first drive, and the second drive is controlled by fluid lines leading respectively to the large and small chambers of the first drive.
Abstract: An operating apparatus for a hydraulic shovel for operating a plurality of control valves which control the operation of work devices includes pilot type control valves, pilot valves, levers for operating pilot valves, and an operating pattern switching valve. The operating pattern switching valve has a rotary spool inserted into a casing. A plurality of input ports are provided in a peripheral surface of the casing with phases deviated from each other axially and peripherally. A plurality of output ports are provided oppositely to the input ports.
Abstract: A source of pressurized hydraulic fluid has a variable fluid output rate and a control system which varies the fluid output rate responsive to a load sense control signal, e.g., a variable displacement pump. The pressurized fluid is made available to a plurality of hydraulic actuators through a corresponding plurality of work control valves. A load sense line is utilized to sense the pressure of the fluid in each hydraulic actuator and to apply a total load sense signal to the control system. A conduit containing a pressure reducing valve provides fluid communication between the output of the source of fluid and the load sense line to pass fluid therethrough to the load sense line only when the pressure in the load sense line is less than a predetermined value. Maintaining at least this minimum pressure in the load sense line minimizes lag in the load sense signal which would otherwise occur as a result of the loss of fluid in the load sense line due to the bleeding of the load sense line.
Abstract: A servomotor is actuated by a pressure medium and has a piston reciprocated in the cylinder, the piston being mounted by a piston rod that extends through a cylinder end wall. The piston has a piston member bearing against the cylinder and is mounted for radial movement relative to the piston rod by a pair of piston guide plates that extend on opposite sides of the piston member. The guide plates are mounted by the piston rod for axial movement therewith.
Abstract: A hydraulic control apparatus, more particularly for operating a motor vehicle clutch release mechanism, comprising a master cylinder, a slave cylinder and a conduit connecting the master cylinder to the slave cylinder. The apparatus is in the form of separate modular units which are separately, but simultaneously, filled with hydraulic fluid after simultaneous evacuation of atmospheric air from the apparatus modular units and test of the integrity of the modular units, and the pre-tested and prefilled modular units are shipped unconnected to a user.
July 11, 1988
Date of Patent:
December 25, 1990
Automotive Products plc
David J. Compton, Richard A. Nix, Keith V. Leigh-Monstevens
Abstract: A hydraulic control mechanism to control operating elements, such as a hydraulic motor, or hydraulic cylinder, employing presetting of a set point, for example via a stepping motor, and mechanical feedback of an actual value. Functional elements are provided in the form of rotary pistons that fit inside one another, rotating relative to one another, and serving for the sensitive regulation of the direction and quantity of a pressure medium stream that is supplied from a pressure medium source to the operting element and flows back therefrom to the tank. One rotary piston is positively connected with the presetting of the set point, and the other rotary piston is positively connected with the operating element for the mechanical actual value feedback. In this way, in contrast to known control mechanisms where a slide or seat valve is actuated by a longitudinal movement, the rotational movement of the set point and actual value are directly compared with one another.
Abstract: A speed control system for a working vehicle comprises a hydrostatic transmission for propelling the vehicle, a hydraulic cylinder and a control valve. The hydraulic cylinder includes a cylinder case operatively connected to a control shaft for varying a swash plate angle of the hydrostatic transmission, and a piston rod fixed to a case containing the hydrostatic transmission. The control valve is fixed to the cylinder case and includes a spool extending parallel to the hydraulic cylinder and operatively connected to a foot pedal for manually controlling the hydrostatic transmission. The cylinder case is shiftable following a shift of the valve spool.
Abstract: A hydraulic switching system has an adjustable delivery volume pump connected to a pump regulating unit that is controlled by a load-sensing regulator. The load-sensing regulator is connected to a control pressure line that carries the maximum hydraulic energy consumer pressure required by at least one hydraulic energy consumer. The hydraulic energy consumer connected to the pump is controlled by a multiway valve having a given adjustment path. In order to increase the fine-controllability of the hydraulic energy consumer when desired, a pressure-compensated flow control valve which is located in the control pressure line is switched in and out of the system.
Abstract: A housing (50, 52) defines a slide chamber (54) in which a slide member (34) reciprocates between three positions. A coil spring (86) holds the slide member (34) into a center position. In this position, slide member (34) blocks fluid flow through a port (28) and positions an electrical conductor (96) away from electrical contacts (110, 112). A push on the slide member (34) moves the electrical conductor (38) into circuit making contact with the contacts (110, 112). A pull on slide member (34) moves an exhaust passageway (36) in the slide member (34) into communication with the fluid port (28). The switch function activates a compressor which pumps air into an inflatable seat actuator. The valve function exhausts air from the inflatable seat actuator.
Abstract: A hydraulic booster for a master cylinder in which an inlet valve is interposed between an output pressure chamber at the back of the booster piston and an input pressure chamber connected to a pressure source. Advance of the valve piston opens the inlet valve. An outlet valve between the output chamber and an outlet chamber connected to an oil tank closes at advance of the valve piston relative to the booster piston. The booster chamber is exposed to a rear of a master cylinder operation piston. The valve piston oil feed passage connects input pressure chamber with booster chamber at opening of the outlet valve. The reaction chamber at the front surface of the booster piston is reduced in volume with the advancing movement and is connected to an accumulator making it possible to smooth initial operation of the master cylinder and reduce booster system size.
Abstract: A pilot control circuit including a pilot pressure pump and a float center connected directional control pilot valve is provided with a warm up circuit for warming up the hydraulic fluid in the pilot circuit. The warm up circuit includes a pair of branch conduits commonly connected to the high pressure side of the pilot pressure pump and respectively connected via flow restriction to the pilots of a primary directional control valve. Fluid can flow from the branch conduits through the pilots and then through the centered pilot valve to the low pressure side of the pilot pump, allowing a warm up circulation of fluid through the entire pilot circuit while its control valve remains centered.
Abstract: A hydraulic safety brake valve arrangement for a motor controlled by a directional control valve. The safety brake valve arrangement has a main valve closing the load lowering conduit in a rest position. Pump pressure opens the main valve to throttle exhausted fluid and at the same time throttle fluid through the supply conduit to the opposed motor chamber. A compensating valve is placed in series with the main valve throttle for the loaded side of the motor. Motor speed is thereby controlled independent of the external loading on the motor.
Abstract: An improved fluid supplying and exhausting arrangement for fluid-powered rotary motion actuating devices of the dual piston rack-and-pinion type. A first conduit arrangement includes a central opening through an axial end wall of the actuator housing and a fluid transfer tube fitted in such opening and extending axially through the adjacent piston into the intermediate fluid chamber between the two pistons for delivering fluid and exhausting fluid from the intermediate chamber, with the adjacent piston being slidable on the transfer tube in sealing contact therewith. A second conduit arrangement includes another axial opening in the end wall into the adjacent outward chamber of the housing and another transfer tube fixed to and extending axially through one piston and extending axially through the other piston to open at the opposite ends of the tube into the two outward fluid chambers of the device, with the other piston being in axially slidably sealing contact with the second tube.
Abstract: A disengageable connection between an internal combustion engine and a propeller which serves for the drive of a gyroplane. The disengageable connection is a fluid coupling which includes a controllable oil circulatory system. The fluid coupling is supplied with oil by way of the oil circulatory system during the operation of the internal combustion engine. By contrast, the oil escapes out of the fluid coupling when the propeller operates under auto-rotation.
Abstract: A system for converting the output of a constant speed motor to variable fluidic flow at the ends of a linear actuator comprising a drive gear coupled with an electric motor for concurrent rotation at a fixed rotational speed; a driven gear operatively coupled to the drive gear; a drive train operable in response to rotation of the drive gear to rotate the driven gear, the gear train including adjustment mechanisms for selectively varying the rotational orientation between the drive and driven gears; a pump having a pair of spaced cylinders in axial alignment with pistons coupled through a reciprocal connecting shaft and with a connector rod pinned at its midpoint to the connecting shaft for oscillation; rigid links coupling the ends of the connector rod with the drive and driven gears so that rotation of the drive and driven gears will oscillate the connecting rod and reciprocate the connecting shaft at a speed correlated to the orientation of the adjustment mechanisms of the gear train; and fluidic lines co
Abstract: A hydraulic continuously variable speed transmission includes means for detecting a speed reduction ratio of said continuously variable speed transmission, means for detecting an accelerator opening, and means for detecting vehicle speed. During running, when the means for detecting the accelerator opening detects that the accelerator opening has been fully closed, the means for detecting speed the reduction ratio detects the speed reduction ratio at the moment, and then an operation initiating vehicle speed of said clutch valve is determined based on the detected speed reduction ratio, and when the vehicle speed detected by the means for detecting vehicle speed is reduced to the operation initiating vehicle speed, the clutch valve starts to open.
Abstract: A high-pressure source of hydraulic fluid and a sump are connected to a cyclically operating user of hydraulic fluid having a hydraulic accumulator by a high-pressure feed line having one end connected to the source and an opposite end connected to the accumulator and user. A pressure-limiting valve has an input side connected to the high-pressure line between the ends thereof and an opposite output side connected to the sump. This valve opens only when pressure in the line exceeds a preset maximum to allow flow between its sides. A detector is connected to the output side of the valve for measuring the peak pressure thereof over several operating cycles of the user and a controller is connected to the detector for operating when the peak pressure detected over several operating cycles exceeds a predetermined threshold.
Abstract: A load-independent control device for hydraulic users has an initial position in which a control line transmitting a load pressure is connected with a tank. The control device has a control valve for the user and a switching valve, which can be controlled independently of the control valve, and has a cutoff position as well as a through position, in which it connects with the control line transmitting the load pressure to the tank.
Abstract: Control system for a load-sensing hydraulic drive circuit comprising; at least one hydraulic pump; hydraulic actuators driven by the hydraulic pump; and a pressure compensated flow control valve between the pump and each of the actuators, for controlling a flow rate of fluid to each actuator in response to a control signal. The control system has first detection means for detecting a differential pressure between the pump delivery pressure and the maximum load pressure; second detection means for detecting the pump delivery pressure; first means for calculating a differential pressure target pump delivery amount Q.DELTA.p to hold the differential pressure constant; second means for calculating an input limiting target pump delivery amount QT based on at least a pressure signal from the second detection means and an input limiting pump function; third means for selecting one of the differential pressure target delivery amount Q.DELTA.
January 26, 1989
Date of Patent:
November 6, 1990
Hitachi Construction Machinery Co., Ltd.