Abstract: A fluid control system is disclosed that includes a first double-acting actuator and a second double-acting actuator. A first independent metering valve has a first control port connected to the first double-acting actuator, a second control port connected to the second double-acting actuator, first and second independently operable valves disposed between the inlet port and the first and second control ports, and a first check control mechanism having a main check valve between the inlet port and the first and second independently operable valves. The first check control mechanism controls the main check valve to allow the first and second actuators to operate in either an independent function mode or a regenerative function mode.

Abstract: A fluid control system includes a pump, a tank, and an actuating cylinder having a rod end chamber and a head end chamber. The fluid control system also includes an independent metering valve arrangement and a pressure sensor configured to sense a pressure of fluid at the head end chamber. A controller communicates with the valve assembly and the pressure sensor. The controller selectively actuates at least one valve of the independent metering valve arrangement based on the sensed pressure at the head end chamber and a mode of operation of the control system.

Abstract: A method for controlling a hydraulic system may include receiving an input command from an input device, generating a desired working pressure value relating to a working chamber of an actuator based on the input command, and generating a desired pressure value relating to a non-working chamber of the actuator based on the input command. The method may also include operating a valve assembly to control a fluid flow condition of the working chamber and to control fluid flow from the non-working chamber.

Abstract: A fluid circuit is provided to independently control the flow of fluid into and out of each end of an actuator. This is accomplished by having two different independently controlled valves controlling the flow of fluid into and out of one end of the actuator and by having two other independently controlled valves controlling the flow of fluid into and out of the other end of the actuator. Regeneration of the fluid flow from one end of the actuator to the other end of the actuator is provided by blocking the exhaust flow of fluid to the reservoir by one of the independently controlled valves and redirecting the flow across the other of the independently controlled valves to join with the flow of the pump that is being directed to the other end of the actuator. This arrangement permits a portion or all of the fluid from one end of the actuator to be regenerated to the other end of the actuator.

Abstract: Apparatus for surface control of a sub-surface safety valve set within the production tubing of a drilling well, the apparatus comprising a hydraulic actuator for opening the sub-surface safety valve, a control line for supplying hydraulic control fluid to the actuator, a first control valve for controlling the supply of hydraulic fluid to the control line, a non-return valve in the control line path, between the actuator and the control valve, for preventing any contaminants entering the hydraulic fluid at the actuator from reaching the first control valve by migration up the control line, and an exhaust line connected to the actuator and control line and an associated second control valve enabling flushing of fluid from the actuator and control line.

Abstract: In an electrohydraulic lifting control device (S) for stacker trucks, which comprises, for lifting control, an electrically operable three-way flow regulator (R1) in a lifting branch (1) between a pressure source (P) and a hydraulic cylinder (Z) as well as, for lowering control, an electrically operable two-way flow regulator (R2) in a lowering branch (2) which branches off from the lifting branch (1) and leads to the reservoir, a redundancy switching element (A) is provided, which is actively electrically operable between closed and open positions, said redundancy switching element (A) being provided between the control pressure circuit of the two-way flow regulator (R2) and/or the control pressure circuit of the three-way flow regulator (R1) and the reservoir (T).

Abstract: A control valve in fluid communication with an actuator may include a pressurized pilot supply and a fluid reservoir fluidly connected to a passageway defined by a valve body. A pilot operator is selectively moveable within the passageway, and a flow metering operator is moveably disposed within the passageway. A fluid make-up operator, disposed in the passageway and in fluid communication with the fluid reservoir and the actuator, directs pressurized pilot supply fluid in response to a decrease in actuator pressure coinciding with a cavitation condition within the actuator. A control chamber within the valve body contains pressurized fluid from the pilot supply and is in fluid communication with the flow metering operator. The flow metering operator fluidly connects the actuator with the fluid reservoir under the influence of the pressurized fluid within the control chamber through activation by either the pilot operator or the fluid make-up operator.

Abstract: A system and method for controlling an electro-hydraulic valve arrangement to provide make-up fluid to a hydraulic actuator are disclosed. The system includes an electro-hydraulic valve arrangement actuated by a control lever and disposed between a pump having a stand-by pressure and a hydraulic actuator. A pressure, representative of the fluid in the hydraulic actuator, is sensed and compared to the stand-by pressure of the pump. The control of the control lever over the electro-hydraulic valve arrangement is overridden when the difference between the pump stand-by pressure and the pressure of the fluid in the hydraulic actuator is greater than a predetermined pressure limit.

Abstract: A pressure regulating valve (20) for adjusting a pressure of a supply/discharge passage (10) to a pressure balanced against a weight of a body to be carried (1) is provided. The supply/discharge passage (10) is connected to a working chamber (8) of a cylinder (2) for raising and lowering the body to be carried (1). A control valve (38) for increasing and decreasing a pressure in a control passage (28) in accordance with a balance between the weight of the body to be carried (1) and a working force in a reaction force chamber (42) to which a pilot pressure is introduced from the control passage (28) is also provided.

Abstract: A fluid control system includes a pump, a tank, and an actuating cylinder having a rod end chamber and a head end chamber. The fluid control system also includes an independent metering valve arrangement and a pressure sensor configured to sense a pressure of fluid at the head end chamber. A controller communicates with the valve assembly and the pressure sensor. The controller selectively actuates at least one valve of the independent metering valve arrangement based on the sensed pressure at the head end chamber and a mode of operation of the control system.

Abstract: The cylinder-piston unit comprises a headpiece, within the body (25) of which there are provided: a pressurized fluid inlet (23) to be connected to the feed; a fluid outlet (24); at least one conduit (21) communicating with the first operating chamber; between the inlet (23) and the conduit (21), a first passage (A) having in a lateral face of the body (25) two spaced-apart ports (31a, 32a), one communicating with the inlet (23) and the other with the conduit (21); and finally, between the outlet (24) and the conduit (21), a second passage (B) having in a lateral face of the body (25) two spaced-apart ports (31b, 32b), one communicating with the outlet (24) and the other with the conduit (21).

Abstract: A drive device comprising a closed hydraulic circuit which has a hydraulic drive adapted to be actuated by hydraulic medium and has a hydraulic pump responsible for the supply and removal of the hydraulic medium to and from the hydraulic drive. For the operation of the hydraulic pump an electric motor is provided. The activation of the hydraulic drive is controlled by the operational state of the hydraulic pump.

Abstract: A device for hydraulic adjustment of rollers of strand guiding segments of a strand casting device has hydraulic cylinders which are separated by a piston with piston rod into a cylinder chamber and an annular cylinder chamber, respectively. The cylinder chambers can be connected by control members alternatingly and in opposite directions as well as simultaneously with a pressure source and a pressure sink, wherein on-off valves are provided as control members.

Abstract: In one aspect of the invention, the hydraulic system provided with the hydraulic pressure source and at least one meter-in spool valve. Each Spool valve has an inlet and an outlet. A hydraulic actuator is fluidly coupled with the spool valve outlet. A load hold check valve fluidly interconnects the pressure source with at least one spool valve inlet. The load hold check valve has a pressure control chamber. A three way valve has a first port in fluid communication with the pressure control chamber, a second port in fluid communication with at least one spool valve inlet, and a third port in fluid communication with the pressure source. Proved pressure and flow control to an actuator are provided, and make-up and line relief are provided without the use of an additional spool valve.

Abstract: A hydraulic system controls the flow of fluid to and from several functions on a machine. Each function has a valve assembly through which fluid is supplied under pressure from a source to an actuator and through which fluid returns from the actuator to a shared return line connected by a return line metering valve to the system tank. There are several regeneration modes of operation in which fluid exhausted from one port is supplied into the other port of the same actuator, which eliminates or reduces the amount of hydraulic fluid that must be supplied from the source. In some regeneration modes, input fluid for an actuator is obtained from another hydraulic function via the shared return line. In these regeneration modes an electronic controller operates the return line metering valve to restrict fluid from flowing into the tank from the shared return line, so that the fluid will be available to be supplied into an actuator port.

Abstract: A high-pressure primary fluid control valve and a multi-pressure selector fluid control valve are disclosed for operating a fluid-actuated device. Preferably a spherical ball-poppet and frusto-conical valve seat adapted for substantially line-contact therebetween are provided with an upstream flow area adjacent the line-contact in order to substantially minimize sonic flow damage to the actual sealing surface of the valve seat by shifting it away from such line-contact seating. Preferably, the ball-poppet is movable within a poppet guide that is allowed to float radially in order to allow the ball-poppet to be substantially self-centering with respect to the valve seat. In addition, cross-over leakage is preferably negated by closing an exhaust ball-poppet just prior to opening a supply ball-poppet. These principles and features are equally applicable to either or both of the primary or the multi-pressure selector fluid control valves.

Abstract: A high-pressure fluid control valve is disclosed for operating a fluid-actuated device. Preferably a ball-poppet and frusto-conical valve seat adapted for substantially line-type contact therebetween are provided with an upstream restricted flow area in order to substantially minimize sonic flow damage to the actual sealing surface of the valve seat. Preferably, the ball-poppet is movable within a poppet guide that is allowed to float radially in order to allow the ball-poppet to be substantially self-centering with respect to the valve seat. In addition, cross-over leakage is preferably negated by closing an exhaust ball-poppet just prior to opening a supply ball-poppet.

Abstract: A fluid control module that can control the flow of fluid between a rail line, a drain line, a first cylinder line and a second cylinder line. The control module includes a plurality of fluid-driven valves that can couple the cylinder lines to the rail and drain lines. Each fluid-driven valve is controlled by a control valve. The module may be actuated into one of a plurality of different states.

Abstract: In a machine tool by pulse drive of a hydraulic system, a piston of a hydraulic cylinder is connected with a table, and an outflow valve and an inflow valve, which form a pair, are respectively connected with a right and a left hydraulic chamber. When the feed table is moved to the right, for example, control is conducted so that the valve-opening period of one valve can be a portion in the middle of the valve-opening period of the other valve. Since a portion of pressure in the hydraulic chamber is canceled, an effective pressure, the pulse width of which is narrow, remains. Accordingly, even in the case where a common inexpensive electromagnetic valve is used, it is possible to accomplish a smooth feed motion.

Abstract: Electro-pneumatic positioner with a pneumatically driven dual-chamber actuator having a pneumatic main air intake valve and a pneumatic main air discharge valve attached to a pressure pipe of the actuator. The positioner may also include a further main air intake valve and a further main air discharge valve attached to a further pressure pipe of the actuator. Each main valve has an actuating element, with the actuating element for the one and the further main air intake valves each being formed by a corresponding main valve. To manufacture an electro-pneumatic positioner of this type comparatively economically, the actuating element of the one main air discharge valve is formed by a feed pipe which connects the pressurized side of the one main air discharge valve to the interior of the reversing valve of the further main air intake valve.

Abstract: A band controlled valve apparatus for controlling fluid flow from a source to a sink, including a base (12) having an upper surface and an aperture (16) extending from the upper surface through the base (12) allowing the flow of fluid from the source through the base (12) to the sink when the aperture (16) is not covered, an elongate flexible band (8) with a first portion (8a) in contact with the upper surface of the base (12) and a second portion (8b) extending forwardly of the first portion (8a) then upwardly and rearwardly above at least a part of the first portion (8a), the second portion (8b) being actuated to selectively move the second portion (8b) of the band (8) forwardly or rearwardly to cover or uncover, respectively, the aperture (16) with the first portion (8a) of the band (8) to thereby prevent or allow, respectively, fluid flow through the aperture (16).

Abstract: A hydraulic drive system for a supersized hydraulic working machine such as a hydraulic excavator includes hydraulic pumps connected to main lines through a delivery line and a supply line. Branch portions from the main line include flow control valves for allowing a hydraulic fluid to flow from the hydraulic pumps toward hydraulic cylinders. A hydraulic reservoir is connected to the main lines through a reservoir line and a drain line. Other branch portions for the drain line include flow control valves for allowing a hydraulic fluid to flow from the hydraulic cylinders toward the hydraulic reservoir. A line branched for the delivery line includes a bypass valve for supplying the hydraulic fluid delivered from the hydraulic pumps to the supply line at a desired flow rate and returning the remaining hydraulic fluid to the hydraulic reservoir.

Abstract: A three-way valve for controlling the application of air to a pneumatically controllable device has a pressure chamber for pressurizing a work chamber to which the device is connectable and an exhaust chamber for expelling air from the work chamber. Unidirectional flow means prevents air in the work chamber from entering the space behind a valve member controlling the flow of air from the pressure chamber to the work chamber for avoiding valve lockup.

Abstract: This disclosure is directed to novel systems and methods for producing motion in response to a drive signal where the motion has a smooth translational reversal. The system accepts a command position signal and compares the command position signal to the actual position of a linear actuator to develop a position error that is then conditioned to produce a pair of valve drive signals that command series connected proportional valves that supply the linear actuator from a common connection of the valves with fluid flow and pressure to adjust the position of the linear actuator so as to reduce the position error by imparting motion to the linear actuator, thus imparting motion to a load. The conditioning of the valve drive signals includes the processing of the position error and the application of a quiescent drive signal to develop or nearly develop a quiescent fluid flow through the series connected valves. The quiescent drive signal can be automatically or manually developed.

Abstract: A control system for a hydraulic circuit having a tank, a pump, a supply conduit connected to the pump, a reversible hydraulic motor, an input conduit connected to the motor and an output conduit connected to the motor is disclosed which comprises a first, second, third, and fourth independently operable electrohydraulic metering valve, the second and third valves being disposed between the supply conduit, the first and second valves being disposed between the input conduit, and the third and fourth valves being disposed between the output conduit, a first pressure sensor connected to the supply conduit for sensing a pressure within the supply conduit, a second pressure sensor connected to the input conduit for sensing a pressure within the input conduit, a third pressure sensor connected to the output conduit for sensing a pressure within the output conduit, a speed and directional sensor connected to the motor for sensing the speed and direction of the motor, and a controller connected to the pump, the valv

Abstract: A valve arrangement including a micro-valve at an intake opening and a fuer valve at an output opening of a chamber connecting to a pressure-variable switching member, the valves being structured to maintain a closed state by an applied pressure difference. At least the micro-valve is provided with a closure member which can be energized to affect a change-over from one state to another. No energy is required to maintain the changed-over state.

Abstract: A pilot operated control valve has a main poppet which selectively engages a valve seat to control flow of fluid between an inlet and an outlet. The flow of fluid through a pilot passage in the main poppet is controlled by a pilot poppet that has a pressure balancing stem extending into the pilot passage. The control valve incorporates a compression check valve and/or a reverse flow check valve, in addition to a transducer for sensing the pressure at the outlet.

Abstract: A three-way or multi-way valve is provided, which is built up of a plurality of two-way valves, each of which has a high pressure connection and a low pressure connection which are separated from each other by means of a valve seat with which a closure element co-operates, the two-way valves being arranged to be operated in pairs or in groups by means of a control pressure fluid by way of a control pressure line opening into a pressure chamber, and one of the two-way valves of each group being arranged in a connection between a pressure source and a load, and another two-way valve of the same groups being arranged in a connection between the load and a pressure sink. With a valve of this type, it is desired to obtain improved closing behavior with simple construction. For this purpose, at least one of the connections, especially the high pressure connection, of at least one valve of each group communicates with the control pressure line by way of a throttle channel.

Abstract: A hydraulic elevator includes a car engaged with a first hydraulic ram, a counterweight engaged with a second hydraulic ram, and a pump to transfer hydraulic fluid between the hydraulic rams. The counterweight hydraulically balances the car without the requirement of a roped connection between the car and counterweight. A fluid flow system controls the transfer of hydraulic fluid between the hydraulic rams. As a result, there is no tank or reservoir for hydraulic fluid.

Abstract: A system and method for controlling an independent metering valve operating in a hydraulic circuit determines a displacement command for one or more metering valves to provide desired flows through the metering valves and desired pressure drops across the metering valves. The system determines the displacement command based on a mode of operation of the hydraulic circuit and a velocity for a hydraulic device controlled by the hydraulic circuit. The system determines the displacement command further based on an amount of flow available to the hydraulic circuit. The system allows the hydraulic circuit to be electronically controlled thereby providing flexibility not found in conventional hydraulic control systems.

Abstract: A system and method for controlling an independent metering valve operating in a hydraulic circuit determines a displacement command for one or more metering valves to provide desired flows through the metering valves and desired pressure drops across the metering valves. The system determines the displacement command based on a mode of operation of the hydraulic circuit and a velocity for a hydraulic device controlled by the hydraulic circuit. The system determines the displacement command further based on an amount of flow available to the hydraulic circuit. The system allows the hydraulic circuit to be electronically controlled thereby providing flexibility not found in conventional hydraulic control systems.

Abstract: A pneumatic fluid control valve includes a valve body having a fluid inlet connectable to an external source of pressurized pneumatic working fluid, one or more load outlets, one or more corresponding exhaust ports, and a movable valve mechanism. The movable valve mechanism includes at least a pair of movable valve element and preferably resilient deformable connectors in a generally abutting relationship between adjacent movable valve elements for deformably transmitting coordinated motion therebetween. The deformable connector resiliently allows one of the movable elements to move and compress the connector before such coordinated motion is transmitted to the other movable element in order to minimize internal leakage.

Abstract: A riding lawn mower is provided that has an engine, a device that requires control and a vacuum actuated control mechanism for controlling the device. The vacuum actuated control mechanism includes a vacuum actuator having first and second chambers separated by a movable membrane, first connecting means for operatively connecting the vacuum actuator to the device, vacuum means for providing a vacuum to the vacuum actuator, activating means for selectively activating the vacuum actuator and securing means for securing the vacuum actuator in place. The securing means also secures the device in place.

Abstract: An electrohydraulic displacement controlled valve module is disposed in a bore of a valve body for controlling fluid flow between first and second ports. A main valve element slideably disposed in the bore is biased to a closed position blocking communications between an annular groove of the valve element and the second port. An actuating chamber defined at one end of the valve element receives pressurized pilot fluid for urging the main valve element toward an open position communicating the first and second ports through the annular groove. A passage communicates the actuating chamber with a control chamber disposed at the other end of the valve element through an orifice. A poppet is disposed within the control chamber and is biased into sealing engagement with an annular valve seat of an outlet port by a feedback spring disposed between the valve element and the poppet.

Abstract: A pneumatic control system for selectively controlling a pneumatically-operated device for controlling movement of a variable load, such as a material handling device or lifting and lowering device, is capable of automatically sensing the load exerted on the pneumatically-operated device and automatically self-compensating for varying loads in order to selectively maintain the load in a static condition. The system further allows for ease of manual manipulation of the load to a new static condition and automatically self-compensates in order to maintain the load at such new static condition. The system preferably accomplishes this by automatically detecting the outlet pneumatic pressure necessary to maintain the load in a first static condition and for automatically self-adjusting the outlet pneumatic pressure to maintain the load in a second static condition.

Abstract: A control scheme is provided that controls the maximum pressure level in desired locations of a hydraulic system. This control scheme eliminates the need of separate line relief valves that many times create pressure spikes in the hydraulic system. In one example, the control scheme functions to sense the operating pressure at the desired location and compares it to a differential pressure and a desired input command during one step or loop to establish a predicted pressure level. The predicted pressure level is compared to the pressure necessary to initiate movement of the valving element in an electrically actuated control valve mechanism. The result is used to move the valving element to a predetermined position if the predicted pressure level is less than cracking pressure level and the differential pressure is greater than zero.

Abstract: It is possible for the present invention to operate with the optimal control to prevent a ram from overshooting in a case that a load acting on the ram is decreasing rapidly, like a stamping machining process. Linking a hydraulic circuit which consists of a hydraulic pump 3 and a hydraulic cylinder 2 to make the ram 1 for the hydraulic press equipment move upward and downward and a full-bridge hydraulic circuit with four proportional sheet valves V1 through V4, the working timings of the proportional sheet valves V1 through V4 are controlled by a NC controller 9. In the normal operation, operating the proportional sheet valves V2 and V3 with the turn-on-off control system and with the meter out control system, oil pressure PU acting on the upper chamber 2U of the hydraulic cylinder 2, driving the ram 1 by the piston 10 moving downward, a work is stamped out. The NC controller 9 detects the running by inertia of the ram 1 in the instance of having stamped out a work in the stamping out machining process.

Abstract: The actuator for a position-adjusting device, wherein the position-adjusting device has a stationary part, a movable part, and at least one coupling element and wherein the at least one coupling element is hydraulically movable by the actuator for coupling and decoupling the stationary part and the movable part relative to one another, has a housing and at least one valve piston arranged within the housing so as to be movable between two end positions defining an open position and a closed position of the actuator. The housing has a work connector, a pressure-relieved tank connector, and a pressure-loaded tank connector. The pressure-loaded tank connector includes a pressure-limiting valve. The pressure-relieved pressure connector during displacement of the valve piston between the two end positions communicates with the work connector until a respective one of the two end positions is almost reached. In the closed position of the actuator the work connector is connected to the pressure-loaded tank connector.

Abstract: A flow control valve has a gate connected between an operating fluid inlet and outlet. An actuator permits manual adjustment of the gate area to allow fluid to pass from the inlet to the outlet at a threshold rate of flow for a threshold pressure at the first inlet. A biasing mechanism cooperable with the gate and linearly responsive to variations in a control pressure applied to a control inlet of the valve constantly automatically readjusts the area of the gate in proportion to the control pressure. In a constant speed pneumatic motor application of the valve, the motor inlet pressure is applied to the control inlet of the valve and the motor outlet pressure is applied to the operating fluid inlet of the valve. A regulator connected to the motor inlet senses the pressure at the motor outlet. In operation, at idle, the threshold flow rate through the valve is selected by manual adjustment of the valve actuator or stem. The load is added and the motor outlet pressure decreases.

Abstract: A three position four way directional control valve having a single spool is typically used for controlling fluid flow from a pump to a cylinder and from the motor to a tank. The present invention includes a pair of electrohydraulic control valves with one of the control valves controlling pump-to-cylinder communication between a pump and the rod end and head end chambers of a hydraulic cylinder while the other control valve controls cylinder-to-tank communication between the rod end and head end chambers and the tank. Each of the control valves includes a displacement controlled proportional valve for controlling the position of a pilot operated valve member. Actuation of the hydraulic cylinder requires moving the valve member of one control valve to control pump-to-cylinder communication to one of the chambers while simultaneously moving the valve member of the other control valve for establishing cylinder-to-tank communication between the other chamber and the tank.

Abstract: A control valve device for a hydraulic elevator including a main check valve connected between a hydraulic cylinder adapted to ascend and descend a car of the hydraulic elevator and a hydraulic pump adapted to pump a pressurized oil, a cylinder-side pressure detector disposed between the hydraulic cylinder and the main check valve and adapted to detect a pressure in side of the hydraulic cylinder, a pump-side pressure detector disposed between the main check valve and the hydraulic pump and adapted to detect a pressure in side of the hydraulic pump, an opening solenoid valve connected between the main check valve and the hydraulic pump and adapted to receive a pilot pressure generated only from a pressure generated by the hydraulic pump and open the main check valve in response to the pilot pressure, and a closing solenoid valve connected to the main check valve and adapted to close the main check valve opened by the opening solenoid valve.

Abstract: An application and release magnet valve including an electropneumatic pilot valve portion for controlling a main air valve portion for supplying, maintaining, and releasing air pressure in the brake cylinders on a railway vehicle. The electropneumatic pilot valve portion includes an application solenoid which opens a first diaphragm actuated ball check valve in the main air valve portion to supply air from a supply port to a delivery port and includes a release solenoid which opens a second diaphragm actuated ball check valve to vent air from the delivery port to an exhaust port.

Abstract: The invention relates to a pressure regulation device for a hydraulic system comprising at least one generator (30) of fluid under pressure, a hydraulic actuator (28) and a reservoir (32) of fluid under low pressure, and including an electrovalve controlled by a computer and comprising in a casing (9) an electrical coil (10) and a sliding magnetic core (12) controlling a slide valve (16) sliding in a bore provided in a body (18), the slide valve (16) determining two chambers (22, 36) arranged on either side of the slide valve (16) in the bore, the slide valve comprising a hydraulic chamber (40) communicating with the hydraulic actuator (28) and determining a reaction force adding itself to the force produced by the coil (10), against a prestressed resilient means (20). The hydraulic chamber (40) is delimited by a bore (41) made in the slide valve (16), an end part (43a) of a sleeve (43), a rod (42) and a cup (60) for leaktightness between the rod (42) and the bore (41) of the slide valve (16).

Abstract: A hydraulic pressure control apparatus comprising: an introducing valve provided on a supply duct connecting to each other a hydraulic source and a control chamber for controlling a fluid-operated equipment or increasing or decreasing the hydraulic pressure of the fluid-operated equipment; and a discharge valve provided on a discharge duct discharging hydraulic fluid from the fluid-operated equipment or the control chamber. The introducing valve and/or the discharge valve are disposed in series on the supply duct or the discharge duct; at least one of a plurality of the introducing valves and/or the discharge valves consists of a flow rate-variable valve capable of changing the flow rate of the hydraulic fluid continuously according to the intensity of electric current; and the other introducing valves and/or discharge valves consist of electromagnetic change-over valves fully opened or fully closed.

Abstract: A control valve assembly for an hydraulically operated elevator includes separate control valve units for controlling upwards and downwards movements of the elevator. The up valve unit is connected to a pump output and controls connection of the pump output to the elevator cylinder via a check valve. The up valve unit includes an orifice for connecting the pump output to a reservoir, and a valve member for varying the size of the orifice to control the amount of fluid passed to the reservoir, and thus the amount of fluid supplied to the elevator cylinder. The down valve unit has an inlet for connection to the elevator cylinder, a variable orifice connected to a reservoir, and a valve member for controllably varying the size of the orifice to control the rate of descent of the elevator.

Abstract: A hydraulic valve assembly comprises a valve body defining first and second valve receptacle bores, a fluid pump, a first fluid passage communicated with the fluid pump, a second fluid passage communicated with a hydraulic load, and a third fluid passage communicated with a fluid reservoir. A first valve sub-assembly including a sleeve enclosing a first valve mechanism therein is disposed within the first valve receptacle body for selectively permitting and blocking introduction of the pressurized working fluid. Also, a second valve sub-assembly including a sleeve enclosing a second valve mechanism therein is disposed within the second valve receptacle bore for selectively establishing and blocking fluid communication between the second and third fluid passage means.

Abstract: A hydraulic system for controlling the contract force of a hydraulic device. A proportional pressure relief valve acts as pilot valve for a main valve that controls the lowering process. The proportional pressure relief valve is provided with a solenoid whose voltage can be varied. A pressure sensing line is also applied to the same side of the valve as the solenoid for biassing the valve against a spring.

Abstract: A fluid unit, for example a piston/cylinder unit, is supplied with fluid via a cyclically opened or closed on/off valve. The vacuum peaks occurring on the outlet side of the on/off valve when it is closed and the inertia forces of the flowing fluid are used to supply additional fluid to the fluid unit via a non-return valve leading from a low-pressure connection or reservoir to the fluid unit.

Abstract: A hydraulic elevator pressure relief valve is activated if a pilot valve disposed therein senses an excessive pressure build up within a hydraulic elevator system. The pilot valve opens once excess fluid pressure force is detected. A main piston then facilitates communication between a solenoid valve disposed within the valving system and the drain pressure thereby closing a check valve and thus stopping an elevator car from further movement. The main piston further ports the excess fluid pressure force from the system to drain pressure, thus stabilizing the fluid pressure force therein.

Abstract: A proportional valve comprises two electrically actuated proportional throttle valves, each having an outlet connected to a non-return valve, to each of which a seat valve is connected, each seat valve being pilot-controlled by one of the proportional throttle valves; the electric actuation of the proportional throttle valves proportionally controls and regulates the functions of a hydraulic cylinder. The two throttle valves and the two seat valves are mounted on a housing block which has a planar face at which are connections to a pressure line, a tank line and working lines.