Abstract: A servovalve includes: a fluid transfer valve assembly comprising a supply port and a control port; a moveable valve spool arranged to regulate flow of fluid from the supply port to the control port in response to a control signal; and a jet pipe assembly configured to axially move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow. The spool includes a tubular body defining a path for fluid flow, the tubular body closed at each end by a respective end cap having openings via which, in use, fluid enters the interior of the spool. The end caps extend within the tubular body at least to an extent that they overlap the openings, and wherein the end caps are provided with filter means for filtering the fluid from the openings as it enters the spool.

Abstract: A pivot control apparatus of construction equipment is provided for reaching a desired swing angle by controlling the brake torque of a swing motor during a loading operation using an excavator, along with a control method therefor.

Abstract: A pressure control valve for heavy equipment is disclosed, which can smoothly operate a working device having a high load pressure by limiting a supply of hydraulic fluid to a working device having a low load pressure in the case of simultaneously operating a plurality of working devices in a hydraulic circuit in which a plurality of control valves (e.g., a boom control valve and a bucket control valve) are connected in parallel to a single hydraulic pump. The pressure control device includes a valve body, a spool slidably installed in the valve body and shifted to connect an input port to an output port or to disconnect the input port from the output port, and a signal pressure port for applying a signal pressure to a diaphragm of the spool located in a third back chamber formed in the valve body, disconnecting the input port from the output port, and returning the pressure in the output port to the drain port.

Abstract: An hydraulic unit includes a hydraulic cylinder, and a piston retained in the hydraulic cylinder, wherein the piston can be moved from a first end position located at one end of the hydraulic cylinder to a second end position located at the opposite other end position of the hydraulic cylinder. The hydraulic cylinder is hydraulically connected with a delay unit which is equipped with an auxiliary cylinder containing an auxiliary piston, with which a movement of the piston can be delayed in a middle section located between the first and the second end position. The auxiliary cylinder has a first and a second opening for incoming and outgoing hydraulic oil. In order to precisely set an attenuation point, a throttle valve provided on the auxiliary cylinder or piston be connected in the flow path.

Abstract: A two-stage pressure relief valve for use with hydraulic systems is disclosed. The two-stage pressure relief valve has a first stage that relieves increases in hydraulic system pressure over the normal operating pressure and up to a selected threshold pressure level, and a second stage that brings the hydraulic system pressure down to a selected reduced operating pressure that is below the normal operating pressure in response to increases in the operating pressure over the threshold pressure level.

Abstract: A member that is driven by a hydraulic actuator tends oscillate when fluid flow to the hydraulic actuator is terminated. A pressure relief device reduces that oscillation by connecting first and second first relief valves to the hydraulic actuator. The first relief valve provides a relatively large first relief passage as long as pressure in the hydraulic actuator remains above a threshold. A second relief valve opens a second relief passage at substantially the same threshold pressure and thereafter remains open as long as the pressure remains above another lower threshold. A timer causes the second relief valve to close a given interval of time, if the pressure does not drop below the other lower threshold.

Abstract: A valve device (10) for at least one hydraulic motor suitable for driving a mass of large inertia. The device includes first and second ducts (12, 14) serving to be connected to respective ones of the two main ducts (feed or discharge) of the motor, and an auxiliary duct (15) connected, for example, to a booster duct. The device can have two configurations, depending on which of the main ducts has the higher pressure, in which configurations the main duct at high pressure is isolated, while the main duct at low pressure is connected to the auxiliary duct. The device includes time delay means (36, 46, 38, 48) suitable for limiting the speed of transition between one and the other of the first and second configurations when the difference between the pressures in the first and second main ducts (12, 14) changes sign.

Abstract: The invention provides a system for regulating pressure equalization in hydraulic mechanisms to suppress oscillation in heavy equipment. The system includes a first and second hydraulic lines, a crossover valve in communication with each of the first and second hydraulic lines, a timing system in communication with the crossover valve, and a motion detector in communication with a heavy equipment component. The motion detector senses a linkage motion and operatively opens the crossover valve, which remains open as directed by the timing system.

Abstract: A pneumatic sequential control valve for successive aeration and deaeration of two consumers, wherein for purposes of aeration compressed air is initially applied to the first consumer and only subsequently to the second consumer, and for deaeration the compressed air is initially let off from the second consumer and only subsequently from the first consumer, comprises a valve body with connections for a compressed air line and a first consumer and second consumer, wherein a cavity is provided in the valve body, bore holes extend from the connections for the consumers and for the compressed air line to this cavity.

Abstract: A hydraulic pump assembly (10) for powering a hydraulic torque wrench (24) is air-powered and has hydro-pneumatic control circuitry (39) which continues operation of an air motor (18) which drives the hydraulic pump (16) for a post-advance period after an advance actuator (55) is deactuated. Operation of the pump (16) is continued for a period sufficient to retract a double-acting torque wrench (24), to permit subsequent advances of the wrench (24) within the post-advance period without restarting the pump (16) or to permit a single acting wrench to be moved from one fastener to the next within the post-advance period without restarting the pump (16). Operation of the pump (16) is terminated when the post-advance period expires if the advance actuator (55) is not reactuated, so as to conserve energy and avoid unnecessary heating of the hydraulic fluid.

Abstract: A flow control valve is disposed in a bleed-off line which is for returning to a tank a portion of an oil flow advancing toward a hydraulic motor from a hydraulic pump. Upon operation of a control valve in an accelerating direction, the flow control valve is operated in a closing direction with a certain time lag, while upon operation of the control valve in a decelerating direction, the flow control valve is operated in an opening direction without a time lag. By so doing, an accelerating operation can be done smoothly while maintaining a required torque.

Abstract: A hydraulic pump assembly for powering a hydraulic torque wrench is air-powered and has hydro-pneumatic control circuitry which continues operation of an air motor which drives the hydraulic pump for a post-advance period after an advance actuator is deactuated. Operation of the pump is continued for a period sufficient to retract a double-acting torque wrench, to permit subsequent advances of the wrench within the post-advance period without restarting the pump or to permit a single acting wrench to be moved from one fastener to the next within the post-advance period without restarting the pump. Operation of the pump is terminated when the post-advance period expires if the advance actuator is not reactuated, so as to conserve energy and avoid unnecessary heating of the hydraulic fluid.

Abstract: A hydraulic device for a moving contact piece of a high-voltage power circuit breaker includes a reservoir and a low-pressure tank for hydraulic fluid. A changeover valve has a slide for alternately connecting one of the spaces in the drive-piston/cylinder configuration to the reservoir and to the low-pressure tank. At least one separately controlled and arranged control piston is associated with the slide. A servovalve controls the at least one control piston to drive the slide from a first position to a second position, i.e., from a connected position to a disconnected position of the power circuit breaker.

Abstract: A hydraulic time delay valve includes a hydraulic timer valve having a valve pressure port, a valve return port, a valve cylinder port and a porting device for porting hydraulic fluid from the valve pressure port to the valve cylinder port. A cylinder is coupled to the timer valve and has a cylinder return port and an opening port at the bottom. A piston in the cylinder is axially movable from a depressed position in which the piston blocks the opening of the cylinder to an extended position in which the piston frees the opening. A control applies hydraulic fluid under pressure to the opening. The control includes a fluid restricting device for restricting fluid flowing to the opening. Thus, hydraulic fluid applied under pressure to the valve pressure port depresses the piston to its depressed position and hydraulic fluid applied under pressure via the control is restricted by the fluid restricting device for a period of time determined by a desired time delay.

Abstract: A hydraulic device for a hydraulic drive for a high-voltage circuit-breaker includes a drive piston for a movable contact piece having two piston sides being in connection with a high-pressure reservoir in a closed condition and being acted upon by high-pressure fluid on both sides. For circuit-breaking, a switch-over valve releases a path to a low-pressure space for the fluid in the space with the larger piston area. At least one circuit-closing pilot valve and circuit-breaking pilot valve activate the switch-over valve. A settable delay volume for the fluid is connected in parallel with at least the at least one circuit-breaking pilot valve.

Abstract: A hydraulic volumetric proportioning valve which may be installed in pre-existing hydraulic systems such as aircraft landing gear extension and retraction systems to independently regulate and vary the rate of hydraulic system operation at desired stages of system operation in response to the volume of fluid flow through the system during each stage of system operation.

Abstract: An electropneumatic door valve for use with pneumatic door operations as are used on mass transit vehicles. The single valve housing arrangement provides either a through passageway or a throttled passageway for pressurizing the opening or closing chamber of a pneumatic door drive unit. Provisions are also made to allow automatic reversal should the door become wedged, and to allow manual override should that operation be desired. Electrical pulses initiated by the vehicle operator trigger one of two solenoid valves which direct one of two operating pistons into a position to dictate which passageway will be established. Three vent passageways are provided to exhaust compressed air from any of the chambers which had been charged during a previous door operation.

Abstract: This disclosure relates to a rotation control device for an air-drive and air-journal type dental handpiece, wherein rotation control is made by applying a braking force to an air journaled turbine for a certain time by the use of compressed air operated air timer and a closing valve. When the braking force is applied to cut off drive air to the turbine, there is produced negative pressure in the bearing mechanism by the inertial rotation of the turbine, whereupon negative pressure causes the turbine to suck dirt thereinto. There is also a danger of the operator being hurt by idle rotation of the cutting tool which is rotated together with the turbine. The device of the invention prevents effectively this kind of sucking up dirt and injury to operators.

Abstract: A pneumatic pump includes a pneumatic cycling mechanism that permits the commencement of each successive pumping interval only upon the appearance of a pilot signal. The pilot signal is generated by a pneumatically operated pump timer that determines the pumping interval. The pilot signal is terminated during the pumping interval after a signal timer has timed out. The pump, timers and other pneumatic circuit elements are driven by the same source that powers the pump, and no reference to an externally generated timing signal is required.

Abstract: The valve includes an input port and two output ports and an arrangement to cause fluid pulses to appear at the output ports as a result of the appearance of fluid pulses alternately at the inlet port. The fluid pulses fed to the inlet port directly appears at the outlet ports and directly causes the valve to pass at least through three successive positions for every two successive pulses at the inlet port. This valve controls the operation of a pneumatic control circuit of a wire cutting, skinning and wrapping tool which is mounted in the handgrip of the tool.

Abstract: Hydraulic door closer apparatus has associated with it means for counter-balancing the bias of a return spring, to assist in opening the door by reducing the force needed to open it, or to open the door by over-balancing the bias of the return spring. Remotely manually operable means may initiate opening of the door.

Abstract: Pneumatic Actuator and timing means to provide a selectively timed control signal including a base means to receive a supply of pressurized fluid in chamber means to direct flow of fluid through the base means to signal output port to provide a selectively timed output signal.

Abstract: A control valve has a first position in which it directs air under pressure to a wiper motor through a "run" line to actuate the motor to oscillate the wiper. The control valve has a second position in which it directs air through a park line to a valve complex which routes air unidirectionally to the motor to cause the wiper to assume a "park" or rest position. An overriding valve is interposed in the "park" line and is connected to the air pressure source. This valve is of the solenoid type and is intermittently operated by a timer upon its actuation to dispose the overriding valve in a first position in which the flow of "park" air through the override valve is interrupted for a brief period, to allow "run" air pressure to actuate the wiper in normal fashion, and then dispose the valve in a second position in which the "park" air is routed to the motor to temporarily halt the operation of the wiper. This sequence continues so long as the timer remains actuated.

Abstract: A control circuit comprises pressurized fluid source (11), a two-position directional control valve (14) and an actuator (13), such as the pump of a hydrostatic transmission, connected to the fluid source and the control valve to be selectively actuated thereby.