Abstract: Disclosed is a turntable ladder system mounted on a rescue vehicle. The system includes a turntable ladder mounted on top of a rescue vehicle and comprising an arm that can be bent downwardly to the ground in front of the driver's cabin of the vehicle, and an operator stand located at the ladder for operating the ladder. The operator stand includes a control for controlling movement of the arm. This turntable ladder system also includes a manually operable confirmation button located on the driver's cabin. The confirmation button is operatively connected to the control such that the bending movement of the arm can be controlled by the control only if the confirmation button is operated.

Abstract: Of a plurality of hydraulic signals output from an operating device, a hydraulic signal is input into a control valve serving as a hydraulic control device without conversion, and particular hydraulic signals are converted into electric signals corresponding to their hydraulic pressures by signal converting devices, such as pressure sensors, and are then input into a controller. The controller controls the drive of an electric actuator, such as a rotating electric motor, on the basis of the electric signals. Hydraulic fluid flow paths communicating to the pressure sensors are connected to each other via a throttle, and air in one of the hydraulic fluid flow paths is removed using the other hydraulic fluid flow path.

Abstract: A valve for a fluid circuit is disclosed. The valve has a main valve element with a first end and a second end. The main valve element is movable between a flow-passing and a flow-blocking position in response to fluid pressure exerted on the first and second ends. The valve also has a solenoid mechanism operatively associated with the main valve element to move the main valve element toward one of the flow-passing and the flow-blocking positions. The valve further has a main valve spring configured to bias the main valve element in opposition to movement caused by the solenoid mechanism. The valve additionally has a relief valve element configured to communicate a fluid with the first end of the main valve element in response to a fluid pressure to initiate movement of the main valve element.

Abstract: A valve stack for a work machine is disclosed. The valve stack has first and second valve bodies, each with first and second mounting surfaces and first and second valve members. The valve stack further has a third valve body with a mounting surface configured to engage the second mounting surfaces of the first and second valve bodies, and at least one valve member disposed within the third valve body. The at least one valve member is movable between a first position at which movement of a first operator control device corresponds to movement of the first valve member and movement of a second operator control device corresponds to movement of the second valve member, and a second position at which movement of the first operator control device corresponds to movement of the second valve member and movement of the second operator control device corresponds to movement of the first valve member.

Abstract: A concrete transfer system for a concrete pump car has a pair of concrete input tubes mounted in a hopper, first and second drive cylinders operating with the concrete input tubes for inputting and outputting the concrete by pressure pistons each having a driving rod, an oil pressure pump for supplying oil to the first and second drive cylinders, and a movement sensor for each of the driving rods. A control unit receives a sensing signal from each sensor and there are a plurality of logic valves operated by the control unit that are selectively opened and closed to supply oil to opposite sides of the driving rod of each of the cylinders. A high-low pressure selection valve operates to perform the concrete transfer at either high or low oil pressure.

Abstract: A valve actuator control monitors engine valve trajectory, lift and seating velocity and varies the timing of internal feedback control channels to correct for engine valve positioning errors to achieve precise engine valve lift, closing timing and desired seating velocity.

Abstract: The present invention provides a construction machine with a structure of pilot pipe comprising detection ports for detecting pilot pressure in a body of a switching valve, so that the number of pipe connecting positions and pipe assembly parts such as joints and the like can be decreased and arrangement of the pipe can be simplified.

Abstract: A fluid control system (50) is provided for a work machine (10) having first and second compacting drums (14,16). First and second hydraulic motors (28,32) are connected in series and power first and second vibratory mechanisms (26,30) located within the first and second compacting drums (14,16). A control valve (60) supplies pressurized fluid to the first hydraulic motor (28). The pressurized fluid is transferred through a bypass circuit (74) around the second hydraulic motor (32). A sequencing device (80) closes the bypass circuit (74) transferring the pressurized fluid to the second hydraulic motor (32) after actuation of the first hydraulic motor (28).

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 fail-safe second stage valve for controlling actuator movement upon power loss in a multiplexed fluid power control system. The second stage valve is interposed between a corresponding actuator and a fluid multiplexer to operate generally as integrating or amplifying device which regulates flow to the actuator. The second stage valve is provided with a dampening mechanism in the form of a bleed port to reduce fluid flow to the actuator. The bleed port bleeds off accumulated fluid received by the second stage valve over a predetermined range of valve positions. This changes the position of the valve and thereby reduces flow rate to the actuator. The multiplexed fluid power control system using the fail-safe second stage valve controls the flow to the corresponding actuator upon electrical power loss. The actuator may be used to open and close variable stator vanes in an aircraft gas turbine engine.

Abstract: An electro-hydraulic operating system for an extensible boom includes one or more hydraulic cylinders for imparting relative motion between the boom sections to retract the boom according to an electronically stored program of sequences of movement and speeds. A source of pressurized hydraulic fluid is fed through appropriate control valves which include solenoid valves in fluid communication with a source of pressurized hydraulic fluid. The solenoid control valves are supplied with control currents proportional to the desired flow rates of fluid to the hydraulic cylinders in order to achieve speed and position control according to the stored program. A metering valve structure is provided for operation in conjunction with the solenoid control valves.

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 device and method for selecting a control mode in a power construction vehicle is disclosed. The device has a control mode select switch which selects a function for setting new matching relations between the control levers and the proportional control valves. A controller sets the new matching relations and stores the new matching relations, and controls the actuators in accordance with the new matching relations. In the control mode selection method, one operational motion of an actuator is primarily selected and displayed on a display means. Thereafter, a voltage signal indicative of a levering angle of a control lever associated with the selected actuator is output, thus setting a new matching relation between the control lever and an associated proportional control valve. The above process is repeated in order to continuously set and store new matching relations between the control levers and proportional control valves associated with the other actuators.

Abstract: A hydraulic actuator includes three cylinder spaces: a first cylinder space (6) located between a ring piston and a cylinder; a second cylinder space (7) between the ring piston and an auxiliary piston inside a hollow piston rod connected to the ring piston; and the third cylinder space (8) formed between the ring piston, the cylinder and the hollow piston rod.

Abstract: A pilot pressure operated directional control valve is provided in which a housing is formed therein with a spool having a plurality of ports. The spool bore has a spool fittingly inserted therein so as to be slidably displaceable therein and the spool is slidably displaced both by a spring and under a pilot pressure led into a pressure receiving chamber. Also a spring box is attached to an end surface of the housing in a longitudinal direction of the spool. The spring box is provided with a hollow portion which contains the spring while forming a pressure receiving chamber, as well as a pilot pressure fluid inlet that communicates with the hollow portion and is open in the longitudinal direction of the spool.

Abstract: A flow reinforcement directional control valve that is capable of reinforcing a pressure fluid to two actuators, can be formed as compact and yet is capable of flowing a return fluid out of a single actuator into a tank is provided, wherein a valve block 20 has a spool bore 21 in which a first spool (22) and a second spool (23) are slidably inserted; in which the first spool (22) is adapted to be held at a neutral position thereof by a first spring (36) and to be displaced by a pressure fluid in a second pressure receiving chamber (47) to a position thereof for supplying the fluid to an actuator; and in which the above mentioned second spool (23) is adapted to be held at a neutral position thereof by a second spring (41) and to be displaced by a pressure fluid in a first pressure receiving chamber (42) to a position thereof for flowing a return fluid into a tank and to be displaced by a pressure fluid in a third pressure receiving chamber (52) to a position thereof for supplying a pressure fluid to an actuato

Abstract: A control system is provided for use in a hydraulic system to provide a simple arrangement with a limited number of elements that bypasses the system flow in the event of an electrical malfunction in the system and further allows other hydraulic circuits to operate even if one or more of the hydraulic circuits have experienced an electrical malfunction. The subject arrangement uses an electro-hydraulic fluid flow control valve mechanism in conjunction with directional valve mechanisms that have at least three functional positions and are controlled by associated electrically controlled displacement control mechanisms in response to receipt of electrical signals from an electrical controller.

Abstract: A multiplexing valve is provided having a spool axially movable within a valve casing under the control fluid pressure introduced into variable volume chambers. The spool has passages formed therein such that, with appropriate positioning of the spool, fluid flow communication can be selectively established or inhibited between fluid sources and/or sinks and a given port.

Abstract: A hydraulic control system for a jet aircraft engine has an electronic control that commands a pair of torque motors to ultimately control the position of each one of a plurality of two-position, "latching" hydraulic actuator valves. A first torque motor is operable with a three-position, on/off hydraulic valve. The second torque motor operates in conjunction with a second valve to control the linear position of the spool of a multiplexer selector valve. The multiplexer selector valve has a plurality of positions that the spool can be linear translatable to. At each position is located a pair of control ports to which are ultimately connected one side of each of a pair of corresponding hydraulic actuator valves. The actuator valves may comprise fuel or air valves.

Abstract: Fluidic control of a number of remote functions is achieved by a single servo controlled linearly actuated distribution valve (29) in conjunction with a like number of bistable hydraulically actuable holding relays (17,19,21) the individual states of which are controlled by the distribution valve. Each holding relay supplies one of two pneumatic signals to an associated remote device (11,13,15). Holding relay or distribution valve motion is only required when a change in a remote function is required. The distribution valve is also adapted to provide a fail-safe signal (79) to all remote devices simultaneously to set the individual remote functions to a desired safe condition.

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: When an operator makes the reversing-lever operation by operating a control lever 4A in a direction x.sub.2 in the event a solenoid proportional valve 91A of a directional control valve 8A is failed to be left open, an operation position sensor 30A.sub.2 outputs a low-level signal and operation position sensors 30A.sub.1, 30B.sub.1, 30B.sub.2 output high-level signals. Therefore, an AND circuit 6b.sub.2 outputs a low-level signal and an AND circuit 6b.sub.1 outputs a high-level signal, whereupon a switch signal is output from an amplifier 6h to a solenoid switching valve 121 for shifting it to a right-hand position shown in FIG. 1 so that a pilot line 51 is kept communicated with a reservoir 97. No switch signal is output from the amplifier 6h to a solenoid switching valve 122 for holding it in a left-hand position shown in FIG. 1 so that the pilot line 52 is kept communicated with a pilot pump 96.

Abstract: In a pneumatic control circuit, five three-port, two-position, directional control valves, three of which have manual controls, and two shuttle valves are arranged for controlling a first pneumatic device and a second pneumatic device in an operating mode wherein the second pneumatic device cannot be readily enabled before the first pneumatic device is enabled. A first control valve having a manual control is arranged to control the first pneumatic device. A second control valve having a pilot valve is arranged to control the second pneumatic device. A pilot control valve having a manual control is arranged to connect the first control valve to the pilot valve of the second control valve via a shuttle valve. A holding control valve has a cam control, which is operated by the second pneumatic device, and has an outlet connected to the pilot valve of the second control valve.

Abstract: In a controller (229) of a hydraulic control system for construction machines, a valve control signal calculating function (301) works such that when an operation pattern signal (A-I) for actuators (201, 202 . . . ) is outputted, it selects corresponding one of plural output patterns for an auxiliary valve control pressure stored, as a function of a differential pressure signal between a pump delivery pressure and a maximum load pressure, in relation to the operation pattern signals, followed by calculating an auxiliary valve control pressure (Pc) dependent upon the differential pressure signal based on the selected output pattern, and also selects corresponding one of plural sets of rates of change (K . . . , K . . . ) for the auxiliary valve control pressure stored in relation to the operation pattern signals, followed by combining the calculated auxiliary valve control amount with the selected set of speed changes to calculate each of valve control signals (S21-S26).

Abstract: A control change system for a backhoe in a construction vehicle, comprising a plurality of pilot valves for generating a pilot pressure corresponding to operations of a first and a second control levers, respectively, and a hydraulic switching unit for relaying the pilot pressure from the pilot valves and supplying the pilot pressure to a plurality of control valves. This switching unit includes a plurality of slidable spools for supplying the pilot pressure from the pilot valves selectively to the control valves. The control system further includes a first and a second switching members for selectively sliding the plurality of slidable spools. The first switching member is operable to select the swing cylinder or the hydraulic motor to be controlled by a shift in one direction of the first control lever. The second switching member is operable to switch interlocks between the first and second control levers and a boom cylinder and an arm cylinder.

Abstract: Hydraulic control of reversible hydraulic motors typically requires several different valves to provide for the various operating parameters. The subject hydraulic control circuit has only a pair of electrohydraulic control valves to provide all the typical operating parameters. Operation of the control valves is controlled by a microprocessor in response to receiving command signals from a manually controlled command signal outputting device which establishes a desired fluid flow rate and direction of flow through the control valves.

Abstract: An automatic pressure control device built in a hydraulic actuator driving circuit for driving a plurality of actuators of a construction machine or the like by a single hydraulic pump through respective pilot changeover valves is provided for automatically shuttling the changeover valve of each actuator to reduce its demanded flow rate and uniformly control the operation speeds of all actuators. To this end, the device is arranged to drain an excessive flow rate of the hydraulic pump through a series connection of a flow rate control valve controlled by the highest load pressure of the actuators and a resistance passage including a shuttle and to control the pilot pressure of each pilot changeover valve in response to a pressure at the junction of the series connection.

Abstract: A multiplexed hydraulic control system which avoids the use of a rotary multiplexer and thereby allows for random selection of the multiplexed outlet ports and variable dwell times for the respective ports. A single hydraulic input is multiplexed among a plurality of hydraulic outputs. A control system provides two types of signals: (1) modulation signals selected from a plurality of multiplexed input signals for producing a modulating hydraulic flow, and (2) selector signals for operating on the multiplexer means to route the modulated signal to the appropriately selected channel.

Abstract: A multiplexed hydraulic control system having a plurality of hydraulic channels for individually controlling the positions of a plurality of actuators in the respective channels in accordance with a corresponding plurality of electrical control signals. The system includes a relatively small multiplexing valve or valve array which has a common input and a plurality of individually selected outputs. The multiplexing valve has a control input which is responsive to a source of binary selector signals, such selector signals being used to directly address any particular channel connected to the multiplexer. The system also includes means for modulating a hydraulic signal in accordance with selected ones of the plurality of electrical control signals, and applying the modulated hydraulic signal to the multiplexer common input.

Abstract: A hydraulic circuit for a piece of construction equipment such as a hydraulic shovel. The operation of the hydraulic shovel is controlled by a number of hydraulic actuators which are provided with a high pressure oil through selector valves. A main relief valve prevents an excessive pressure from developing in the vicinity of a main pump, and port relief valves associated with the individual actuators prevent excessive pressures from reaching each actuator. Pilot lines carry a biasing oil pressure from a pilot pump to the main relief valve and to at least one of the port relief valves to boost the relief pressures in the circuit in response to a signal from an operator controlled switch. Simultaneously with effecting a boosting of relief pressure in the relief valves, the operator controlled switch renders one of the actuators inoperative using a shut-off valve so that it may not be operated while the relief pressures are boosted.

Abstract: An electro-hydraulic control system for a mineral mining installation has a series of valve blocks, each contain a number of valves which are operated in dependence on electrical signals to cause hydraulic appliances of roof supports to operate. To allow emergency operation, when there is a power failure or when the control system fails or is otherwise inoperative, further manually operable valves are connected by a flexible, multi-core connecting cable to the valve block of the associated support. The emergency control valves can operate hydraulically controllable direction control valves of the control system and by-pass the electrical controls. The support can then be controlled purely hydraulically, at least in its main functions, using the emergency device.

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 control valve includes a first valve having a cylinder and a piston arranged in the cylinder. The piston defines in the cylinder a pressure receiving chamber and first and second output pressure chambers, and is moved by pilot pressure applied to the pressure receiving chamber to change volumes of the first and second output pressure chambers. The output pressure chambers are connected to each other through a throttle control valve which generates pressure difference corresponding to a rate of change in volumes of the output pressure chambers, between the output pressure chambers. A main valve is connected to the throttle control valve and includes an inlet port, output ports, and a valve member located between the input and output ports. The valve member is moved in accordance with the pressure difference between the first and second output pressure chambers to control hydraulic pressure output from the output ports.

Abstract: A multiplexed hydraulic control system in which high force margins for the multiplexer are achieved by employing hydraulic oscillators as the multiplexer driving means. The multiplexer is typically in the form of a hydraulic cylinder having an input port and a plurality of output ports, with an operator in the cylinder for individually connecting the input port to the output ports. The hydraulic oscillator is mechanically coupled to the multiplexer operator, and oscillation of the former causes oscillation of the latter to sequentially connect the input to each of the outputs. Various means are taught for initiating reversal of the oscillator and controlling the oscillation speed.

Abstract: Fluid systems having fluid motors which control aiding type loads many times have problems with cavitation in one end of the fluid type motor during lowering thereof. It is desirable to eliminate all cavitation in the fluid motor during operation. In order to eliminate cavitation during lowering of an aiding type load and to provide a positive pressure therein, the subject arrangement provides an exhaust pressurizing control for use in a fluid system. The exhaust pressurizing control includes an exhaust manifold means having selector means to provide a positive pressure in the exhaust manifold means during lowering of an aiding type load. The selector means includes pressure limiting and unloading means operative to provide a positive pressure in the exhaust manifold means during lowering of the aiding type load and to unload the pressurized fluid in the exhaust manifold means during raising of a resisting type load.

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: 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.

Abstract: A time multiplexed hydraulic control system in which a multiple section dog valve is multiplexed among a plurality of channels. An electrical actuator on the dog valve controls pilot means. The pilot means is associated with a plurality of followers, one for each channel, and each follower controls the flow rate through an associated output port. Multiplexing means in the dog valve sequentially supplies fluid to the pilot means for sequentially positioning then locking the respective followers. Thus, each channel has continuous hydraulic flow based on the position of its dedicated follower, with the followers being repositioned on a multiplexed basis in associated time slots.

Abstract: A fluid pressure control system comprising a first selector valve for controlling the action of a first actuator, a second selector valve for controlling the action of a second actuator, a first flow control valve for controlling a fluid to be supplied to the first actuator, and a second flow control valve for controlling a fluid to be supplied to the second actuator. A pressure reducing valve is provided for reducing the pressure of the fluid supplied to the second actuator. The pressure on the outlet side of the pressure reducing valve is controlled by the proportional pressure relief valve which is controlled by an external pilot pressure. This system is applicable, for example, to a hydraulic excavator.

Abstract: A hydraulic circuit for a construction machine which operates an actuator for working machine simultaneously with an actuator for working element without degrading the operation of the actuator for working machine. The hydraulic circuit comprises a first hydraulic pump, a first directional control valve connected to the first hydraulic pump and controlling an operation of the working machine actuator, a third directional control valve controlling an operation of the working element actuator, a second directional control valve connected to a second hydraulic pump, a first pilot operating device for controlling an operation of the first directional control valve and a second pilot operating device for controlling an operation of the third directional control valve.

Abstract: An hydraulic system for operating double acting piston/cylinder assemblies and for effecting automatic transition from a regenerative mode of operation of a double acting piston/cylinder assembly to a non-regenerative mode of operation thereof. Pressure responsive valve means automatically converts the hydraulic system from one initially being a high-speed/low force operation to a high force/low speed operation.

Abstract: Fluid control circuits commonly control actuation of a pair of cylinders for positioning an earthmoving blade. The known circuits for providing the three operating modes of the cylinders utilize a separate control valve for each cylinder thereby making precise positioning of the blade difficult since such positioning requires coordinated control of both valves. The subject fluid control circuit includes a selector valve for determining the direction of fluid flow to and from the head end and rod ends of the tilt cylinders and a single control valve for modulating and controlling the fluid flow from the pump to the cylinders. With this circuit, the selector valve can be prepositioned in the desired position prior to actuating the control valve so that dual cylinder tip, dual cylinder tilt, and single cylinder tilt of the blade is readily controlled by manipulation of only the single control valve.

Abstract: A load responsive control system using on a selective basis the energy derived from a negative type load for operation of system controllers, which may be of various types, including electro-hydraulic multi-stage controls, for use in positioning of the main control spools and in control of other system components.

Abstract: Hydraulic control circuit for working members of earth-moving machines including linear and rotary hydraulic actuators associated with respective hydraulic distributors for the operation of respective working members. The rotary hydraulic actuators with their distributors are grouped in a circuit separate from the linear hydraulic actuators and are provided with braking valve means constituted by a single counterbalance valve connected in a common discharge line, the opening of which is controlled by a pilot pressure signal corresponding to the lowest supply pressure for the rotary actuators.

Abstract: The invention relates to a method for the simultaneous actuation of a plurality of hydraulic consumers by means of intrinsically-safe electro-hydraulic valves. The consumers are connected by hydraulic directional control valves to a pressure line and/or a return line. These hydraulic directional control valves can be connected in a predetermined manner, via pre-control valves to a control line. The pre-control valves are pressureless, and possess electro-magnets with a current consumption of less than 50 milliamps. By connection of a series-connected electro-hydraulic directional control valve means, the pre-control valves are connected to the control line, and at the same time are hydraulically locked.

Abstract: An electro-hydraulic control system includes a plurality of two-position control valves, each controlling fluid flow into and out of a corresponding one of a plurality of hydraulic functions. First and second pressure responsive servo actuators associated with each control valve operate to move each control valve to first and second positions, respectively. A two-position, solenoid-operated, pilot valve controls fluid flow into and out of a pilot circuit. The pilot circuit communicates fluid to and from the second servo actuator of each control valve and to and from a plurality of two-position, soleniod-operated, pilot valves. Each pilot valve controls fluid flow into and out of the first servo actuator of a corresponding one of the control valves. A detent mechanism holds each control valve in either its first or its second position in the absence of fluid pressure in the servo actuators.

Abstract: A hydraulic control device is incorporated in a hydraulic control system for a mine roof support assembly. The hydraulic control system includes a plurality of hydraulic control valves which are controlled by the hydraulic control device. The hydraulic control device is constituted by a longitudinal slide valve having a slide member longitudinally reciprocable in a slide valve housing. A rotary drive is provided for moving the slide member within the slide valve housing. The slide member is provided with two axial bores each of which opens into a respective pair of axially-spaced radial bores which terminate at the peripheral surface of the slide member. A first radial bore of each axial bore opens into a respective annular groove formed in the slide valve housing. The second radial bore of each axial bore is connected to a respective group of control ports provided on the slide valve housing.

Abstract: An improved flow control valve apparatus for pneumatically powered tools that include a motor and feed and retract apparatus driven by the motor. The control valve apparatus includes a main flow valve and a retract control valve each of which is controlled by the control valve to provide air to the motor, to automatically stop the feed and retract motion of the tool, and to stop the tool completely when desired.

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: An arrangement for supplying pilot oil to a servo-valve arranged to activate a main valve of a hydraulic system. The hydraulic system also includes a hydraulic oil pump, a valve located between the pump and the main valve, a pressure reducing valve located between the pump and the servo-valve, and at least one auxiliary assembly is arranged to deliver an electric signal to electromagnetic means arranged to activate the servo-valve. In accordance with the invention, the valve located between the pump and the main valve is arranged to be substantially or fully closed when standing at a given, pre-determined pressure corresponding to the servo pressure required by the servo-valve in order to carry out its intended function, and is arranged to be open when the pressure slightly exceeds the aforementioned pre-determined pressure. An electromagnetically operable shunt valve is located between the pump and pressure reducing valve and, when open, to pass oil direct from the pump to a tank.