Abstract: A hydraulic cylinder has a piston in it with a rod projecting out of the cylinder and connectable with a tool which is operable by movement of the piston rod. A high pressure space is defined in the cylinder at one side of the piston and a low pressure space is defined at the other side of the piston. A partition defines the other end of the low pressure space. A diaphragm on the other side of the partition defines an equalizing space between the diaphragm and the partition. A low pressure line is in communication with the low pressure space and with the equalizing space. A change over valve in the lines to both the high pressure space and the low pressure space enables connection of high pressure from a pump either to one space or to the other space in the cylinder while always permitting communication from the low pressure line to the equalizing space, the connection to the equalizing space is in the low pressure line between the change over valve and a non-return valve at the pump.

Abstract: An electrohydraulic control arrangement for controlling a hydraulic cylinder having a double-acting working piston. At least one control valve having a control slide unit that is spring-loaded at one end and can be shifted by a servomotor against the spring force is provided. A valve housing having at least one section is provided with at least one control valve for alliance with each of the pressure chambers of the hydraulic cylinder, with the control slide units of the control valves being spaced from one another and being coaxially disposed in a mirror symmetrical manner relative to one another. A common control element of the servomotor is disposed between the inner ends of the control slide units for moving the same in the same direction.

Abstract: An electronically controllable pneumatically powered valve actuating mechanism for use in an internal combustion engine is disclosed. The engine is of the type having engine intake and exhaust valves with elongated valve stems. The actuator has a power piston reciprocable along an axis and adapted to be coupled to an engine valve and a pneumatic arrangement for moving the piston, thereby causing an engine valve to move in the direction of stem elongation between valve-open and valve-closed positions. The pneumatic arrangement includes a pair of control valves which are movable relative to the piston for selectively supplying high pressure air to the piston. Each control valve includes a thin walled portion having an inner cylindrical surface which slidingly engaging a portion of one of the enlarged diameter cylindrical portions of the piston.

Abstract: A modular handling system is assembled from a plurality of linear drive, rotary drive, or tool modules. The linear drive used as a cylinder block with a cylindrical bore therein and cylinder heads sealing off the cylindrical bore. A pneumatically actuated piston travels within the cylindrical bore. A carriage runs on the cylinder block and is connected with the piston by means of a flexible belt attached to both the piston and the carriage and deflected by deflection rollers mounted on the cylinder heads. Cartridge-type valves are integrated into both cylinder heads for controlling displacement of the piston. One of the cartridge valves is made as a pressure-servo-valve allowing linear control of valve output pressure vs. valve operating current. The cartridge valve integrated into the opposite cylinder head may be either another pressure-servo-valve or a displacement-servo-valve allowing linear control of valve spool displacement vs. valve operating current.

Abstract: A pneumatically powered valve actuator is disclosed including a valve actuator housing, a main piston reciprocable within the housing along an axis and a pair of auxiliary pistons fixed to and movable with the main piston. The main piston has a pair of oppositely facing primary working surfaces. A pair of air control valves reciprocable along said axis relative to both the housing and the main piston between open and closed positions control air flow from a pressurized source causing the main piston and the pair of auxiliary pistons to move. Each auxiliary piston forms, in conjunction with a surface of the corresponding air control valve, a variable volume annular chamber. The variable volume chamber function during the early portion of piston movement to apply a reclosing force to the air control valve and during a latter portion of the piston movement to vent air compressed by the piston during damping. This venting of the residual air is in an axial rather than a radial direction.

Abstract: A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism actuator in an internal combustion engine is disclosed. The transducer has a piston which is coupled to an engine valve, for example. The pistion is powered by a pneumatic source and is held in each of its extreme positions by pneumatic pressure under the control of control valves which are in turn held in their closed positions by pressurized air and/or permanent magnet latching arrangements and are released therefrom to supply air to the piston to be pneumatically driven to the other extreme position by an electromagnetic neutralization of the permanent magnet field. A pair of auxiliary pistons movable with the piston compress air to a pressure above the pressure of the pneumatic source for aiding reclosure of the control valves as well as aiding maintenance of those control valves in their closed positions thereby reducing the size and cost of the latching permanent magnets.

Abstract: A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism actuator in an internal combustion engine is disclosed. The transducer has a piston which is coupled to an engine valve, for example. The piston is powered by a pneumatic source and is held in each of its extreme positions, and air control valves are held in their closed positions by pressurized air and/or permanent magnet latching arrangements and the control valves are released therefrom to supply air to the piston, and the piston is released therefrom to be pneumatically driven to the other extreme position by an electromagnetic neutralization of the permanent magnet field. The piston forms a part of the magnetic latching circuit and that magnetic circuit also includes a radially slotted ferromagnetic member to both complete the magnetic circuit and provide a good air communication path from a high pressure air inlet to the control valve.

Abstract: A pneumatically powered valve actuator is disclosed and includes a valve actuator housing, a working cylinder within the housing having a pair of opposed contoured end faces, and a main piston reciprocable within the cylinder along an axis. The main piston has a pair of oppositely facing primary working surfaces contoured substantially the same as the opposed end faces of the working cylinder to mate therewith providing a small minimum volume and, therefor, a high compression ratio. A pair of air control valves are reciprocable along the axis relative to both the housing and the main piston between open and closed positions for selectively supplying high pressure air to the piston primary working surfaces. The contoured end faces each include a central opening, an outer annular flat surface, and an intermediate frustoconical surface connecting the central opening and the flat surface.

Abstract: A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism actuator in an internal combustion engine is disclosed. The transducer has an armature including a piston which is coupled to an engine valve, for example. The piston is powered by a pneumatic source and includes pneumatic and hydraulic damping as it nears its destination postion. The armature is held in each of its extreme positions by pneumatic pressure under the control of control valves which are in turn held in their closed postions by permanent magnet latching arrangements and are released therefrom to supply air to the piston to be pneumatically driven to the other extreme position by an electromagnetic arrangement which temporarily neutralizes the permanent magnetic field of the latching arrangement.

Abstract: A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism in an internal combustion engine is disclosed. The transducer armature, an engine valve, for example, is powered by a pneumatic source and includes pneumatic damping and energy recovery as it nears its destination position. The armature is held in each of its extreme positions by a permanent magnet latching arrangement and is released therefrom to be pneumatically driven to the other extreme position by an electromagnetic arrangement which temporarily neutralizes the permanent magnetic field of the latching arrangement. A multiplicity of engine operating modes are also disclosed including operation of an engine in a six stroke cycle mode, and a unique intake valve timing scheme where the intake valve closure is delayed beyond bottom dead center of its associated cylinder with the delay being greater at lower engine speeds and less at higher engine speeds.

Abstract: A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism actuator in an internal combustion engine is disclosed. The transducer has an armature including a piston which is coupled to an engine valve, for example. The piston is powered by a pneumatic source and includes asymmetric pneumatic damping. Air damping may be differentially controlled to provide dissimilar damping at the two extremes of piston motion. The armature is held in each of its extreme positions by pneumatic pressure under the control of control valves which are in turn held in their closed positions by pressurized air latching arrangements and are released therefrom to supply air to the piston to be pneumatically driven to the other extreme position by an electromagnetic solenoid or by an electromagnetic repulsion arrangement. The control valves may be spring loaded toward their open positions.

Abstract: A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism actuator in an internal combustion engine is disclosed. The transducer has an armature including a piston which is coupled to an engine valve, for example. The piston is powered by a pneumatic source and includes pneumatic damping with a one-way return of air compressed beyond source pressure back to the air source as it nears its destination position. Air supplied to power the piston may be differentially controlled to compensate for asymmetric resistance to movement and the air damping may be differentially controlled to provide dissimilar damping at the two extremes of piston motion.

Abstract: An apparatus for locking an wheeled table into a fixed location is disclosed. The base of the table is provided with both an electric motor coupled to a hydraulic pump and a manually operated hydraulic pump either of which may provide a source of pressurized hydraulic fluid. Extendable and retractable legs are provided on the base of the surgical table. Hydraulic cylinders disposed adjacent to each of the legs are provided with upper link members pivotally attached to the table's base and lower link members which are pivotally attached to the deployable legs. When pressurized hydraulic fluid is provided by the electrically driven or manually powered hydraulic pumps, the hydraulic cylinders disposed adjacent to the deployable legs are extended. Such extension is translated by means of the respective upper and lower link members into a vertical movement which lowers the supporting legs to fix the table in a specified location.

Abstract: A control force input system for a balance beam or pivot arm pneumatic positioner which does not allow the controlled apparatus to make a full travel motion when the overall control signal is removed. The control force is transmitted to the balance beam by the coupling of the magnetic fields produced by a fixed magnet located on the balance beam and a variable magnet located away from the balance beam. When the motive control signal is removed from the variable magnet, the balance beam returns to an equilibrium or zero position due to the action of a pair of zero springs, stopping the controlled apparatus at its position when the control signal is removed.

Abstract: An actuator has a pilot valve incorporated in a piston thereof which is slidably disposed in a cylinder tube, the piston having first and second piston lands slidably disposed in first and second coaxial cylinder chambers. A spool valve body has first and second spool lands slidably disposed in an inner hole in the piston. When the spool valve body is moved in one direction, a first axial passage in the piston communicates with a pressure sink through a first return port which is opened by the first spool land, and a second axial passage in the piston communicates with a portion of the inner hole in front of the second spool land through a second supply port which is opened by the second spool land.

Abstract: A control force input system for a balance beam pneumatic valve positioner which does not allow the controlled apparatus to make a full travel motion when the overall control signal is removed. The control force is transmitted to the balance beam or other force summing bar using a motor coupled to a drive unit which compresses or extends a control spring coupled to the balance beam. When the motive power control signal is removed from the motor, the balance beam establishes an equilibrium position based on the existing position of the motor.

Abstract: In a rotary fluid cylinder for operating a chuck of the type comprising a piston rod, guide rods disposed in parallel with the piston rod, spring biased check valve mechanism and pilot valve mechanism operating the check valve mechanism both contained in each guide rods, there are provided a pair of diametrically opposed annular pistons concentric with the piston rod, guide rods being received in the annular pistons for guiding longitudinal movements thereof, a cylinder head rotatably mounted on the piston rod, a rotary valve connected to the cylinder head for defining cylinders for accommodating the pair of annular pistons, a sleeve rotatably mounted on the rotary valve, and valve means for alternately admitting operating fluid in the opposite sides of each annular piston.

Abstract: A pneumatic servo valve comprising a piston in a cylinder. Both controlling surfaces of the piston are exposed to controlling air. The piston is provided with an axial drilling extending through it, which communicates via a radial groove with an inlet of controlling air. Both openings of the drilling are normally closed by spring actuated mushroom valves. Controlling chambers in the cylinder communicate through calibrated conduits in the piston with the radial groove, and can be put into communication with the surrounding atmosphere via outlets. The outlets are controlled by electromagnet valves. A microcomputer receives signals from correct and actual value indicators respectively, and administers opening and closing of the valves. When one of these is opened the connected controlling chamber is decompressed and the piston moves in the direction of the empty chamber. One of the mushroom valves follows the movement of the piston, while the other mushroom valve is prevented from moving by a valve seat.

Abstract: A valve includes a valve housing having a valve bore with a first valve member movable therein to control fluid communication between a pump, a reservoir and a hydraulic function. The first valve member includes annular grooves which receive pressure controlled seals. A second valve member is movable in the valve bore and is connected to an actuator. The first and second valve members cooperate to form a pre-control valve which controls pressurization of the pressure controlled seals. The second valve member also connects the actuator with the first valve member so that the seals are relieved of pressure before the first valve member is moved.

Abstract: A pneumatic control assembly for a pneumatic cylinder having cylinder ports at the opposite ends thereof wherein the control assembly includes a valve body clamped directly to the pneumatic cylinder by a stud extending completely through the valve body and threadedly engaging the bore in the cylinder to provide the only means for maintaining the valve body attached to the pneumatic cylinder. An identical stud extends through an adapter to engage the other port in the cylinder and a pilot body is connected to the valve body by screws and includes electrically actuated solenoids for conducting pilot pressure to the valve body for allowing the full pressure to enter and exhaust from the respective ports in the cylinder to move the piston therein back and forth.

Abstract: A steering apparatus is disclosed having a direction control valve for directing pressurized fluid to a hydraulic, power steering motor in a steerable vehicle. A piston in the hydraulic motor is mechanically connected to an operator steering wheel and to the vehicle wheels. Manual turning of the steering wheel effects initial piston movement and steering of the vehicle wheels. Upon initiation of a steering maneuver by manual operation of the steering wheel of the vehicle, piston movement causes the hydraulic motor to produce a pressure differential signal. The direction control valve responds to the pressure signal from the hydraulic motor and directs pressurized fluid from the power steering pump to the side of the hydraulic motor that is lower in fluid pressure.

Abstract: A 4/3-directional control valve with a tubularly shaped valve housing that includes along its longitudinal dimension a central return connection to a reservoir tank for hydraulic liquid, to the left and right of the return connection a working connection to the front and backside of a hydraulic piston disposed symmetrically thereto as well as a pump connection to a pump supplying a constant pressure; these hydraulic connections are adapted to be controlled by two oppositely operating control pistons having a coil spring disposed therebetween, whose end faces are adapted to be acted upon with pump pressure by electromagnetically actuated pilot valves; the volume of the hydraulic liquid which is displaced at one piston side during the left respective right movement of the hydraulic piston, reaches the other piston side by way of the two working connections.

Abstract: A cylinder driving apparatus, wherein a head chamber and a rod chamber of a cylinder for driving a load upwardly and downwardly are communicated with a pressure accumulation tank by way of a balance pipeway equipped with an electromagnetic proportional flow control valve and a recycling pipeway equipped with a pressure control valve mechanism, respectively, and the load is driven by feeding air at reduced pressure to the rod chamber or discharging it to the external atmosphere by way of the pressure control valve mechanism while applying air pressure into the head chamber of the cylinder against the load by way of the electromagnetic proportional flow control valve for adjusting the driving speed.

Abstract: A diaphragm type vacuum actuator movably providing in a case a rod having piston plates, the piston plates being connected to an inner peripheral surface of the case by means of two diaphragms so as to divide a case inside into a first chamber and a second chamber and form an intermediate chamber in between the both diaphragms, and the rod being made movable by subjecting one of said first and second chambers to vacuum and by opening the other thereof to atmospheric pressure; characterized by that air passages are formed in the piston plates, one ends of the air passages are interconnected to the intermediate chamber, and the other ends thereof are interconnected to chambers under atmospheric pressure.

Abstract: A booster steering valve control of the kind that comprises a pair of valve pistons reciprocal in a rotative valve body are driven by a fork shaped member at the end of a steering spindle. The fork shaped member comprises a pair of spaced actuator pins which engage in openings of the respective valve pistons. Thus, the valve body and the fork shaped member have a common axis about which the actuator pins rotate. A particular construction of the invention resides in the displacement of the actuator pins such that their axes are not in a common plane with the steering spindle axis but offset so that the surfaces of engagement between the actuator pins with the respective valve pistons and the spindle axis are coplanar. Engagement is maintained by spring bias acting on the valve pistons.

Abstract: The invention relates to a pneumatic setting device having oppositely operable magnetic valves for alternately pressurizing and exhausting expansible chambers formed by one or more diaphragms to which a reciprocatable setting element is attached. In this construction a return spring may be omitted.

Abstract: A pneumatic door control equipped with a door control valve for operating a door drive to an open or a closed position. The door control valve has an opening and a closing solenoid-operated pilot valve and an opening and closing spool valve, each operable to a passage or a vent position. A shuttle valve is part of the control valve and works in conjunction with an operator-controlled emergency valve to vent both spool valves simultaneously. A differential pressure switch is connected to the door drive to sense abnormal pressure expended in a door-opening or closing movement. Such an occurrence will output a signal to an electronic switching device which also monitors, via limit switches, whether a door is fully opened or fully closed. If excess pressure occurs during a door-closing movement, the switching device will trigger the control valve to reverse to the opening position.

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: Pressurization of closing and opening chambers of a door operator is controlled by first and second magnet valves coupled to the source of air. These valves are alternately energized by a switching network, e.g., a flip-flop, when sequentially actuated to close and open the door. The second magnet valve is biased to its vent position but the first valve is operated to its vent position by air through a double check valve when the second magnet valve is energized. Emergency and choke valves are inserted in series in the air supply to the magnet valves and normally pass air without restriction. Operation of the emergency valve, e.g., door blocked, shuts off air from the magnet valves and diverts that air to inhibit all output from the switching network and, through the check valve in opposite position, to operate the first magnet valve to vent position. Door operation is halted in position.

Abstract: An electro-hydraulic proportional actuator in which the actuator piston position is hydraulically controlled by fluid flow through solenoid valves operable by an electronic control system. An operator control provides an input voltage representing a desired piston position and a transducer generates a voltage representing the actual piston position. The difference between the input and output voltages generates a difference or error signal that is fed into a feedback system including a sample-and-hold circuit. A clock logic system is provided for transmitting the signal from the feedback system to the solenoid valves at predetermined intervals to activate either valve to move the actuator piston in either direction or to activate both valves to hold the piston at a desired position.

Abstract: In a hydraulic piston actuator the supply of working fluid is governed by at least one servo valve of the three-gate type, the spring-loaded valve body of which is activated by a thermowire adapted normally to hold the valve body in a position to close-off the supply of fluid. One end of the thermowire is connected to a compensating device, goverened by the movement of the actuator piston in such a manner that thermal movements are partly counteracted. The servo valve may actuate a maximum switch, and a time relay will, after a predetermined period of time put the fluid pump out of action, and connect both sides of a double acting actuator with a return flow tank.

Abstract: An auxiliary fluid power steering device having a servomotor (8) and a control valve (13) in a common steering gear housing (1). In order to relieve the control valve of axial pressure forces, the valve body (14) of the control valve has four surfaces (24, 25, 26, 27) of equal area respectively exposed exclusively to fluid in the inlet port (22), in the outlet port (23), in one of the servomotor pressure chambers (9) adjacent the control valve and in the other pressure chamber (10) of the servomotor.

Abstract: A manually operable hydraulic selector valve includes a plurality of two-way spool valves which are normally closed and are selectively shiftable individually or in pairs by a joy stick operator to open positions whereby motive fluid can be delivered to a given instrumentality such as the jack cylinder of a construction crane outrigger arm. The joy stick carries a conical disc which cammingly engages drive pin extensions of the individual spool valves. A positive stop for the conical disc is afforded by contact of the disc with the mounting plate of the selector valve. The selector valve is employed with an associated two-way directional control valve.

Abstract: Pump pressure in a fluid power assisted steering device is regulated through the suction side of the pump to supply pressurized fluid to a servomotor through a fluid pressure actuated steering control valve. A pre-control valve controls pressure in an actuating chamber of the steering control valve in response to displacement of the hand steering wheel to obtain a variation in servomotor pressure that is a linear function of the force applied to the steering wheel up to a cut-out point, above which the servomotor pressure rises sharply to a maximum value.

Abstract: A dial operated air pressure regulator produces forward, hold and reverse signals in an air operated control circuit which creates corresponding conditions in a hydraulic circuit. The regulator has a pair of spring loaded valves which slide axially in a pair of valve cylinders which in turn control the air flow in the circuit. The valves are depressed by face cams moulded into the dial; rotation of the dial in one direction causes one cam to operate one valve and produces a forward signal; rotation in the opposite direction causes the other cam to operate the associated valve to create the reverse signal; when neither valve operates, the hold signal results.

Abstract: A vehicle door control valve device having a pair of two-way, electro-magnetically operated, pneumatic valve members arranged so that one valve member is operated to a first position, in which compressed air is supplied to one side of a pneumatic actuator that operates the door, while concurrently, a second identical valve member is operated to an opposite position, in which compressed air is exhausted from the other side of the pneumatic door actuator. The relative positions of the respective valve members may be alternately switched to effect door opening and closing. Operation of the valve members is electro-magnetically controlled by primary and secondary coils arranged to cooperate with a permanent magnet, so that only momentary energization of the coils is necessary to effect switching of the valve members. The arrangement is such that in the case of an emergency, opposite sides of the pneumatic door actuator are both de-pressurized to permit manual door operation.

Abstract: A pneumatic circuit includes a source of fluid pressure 11, a selector valve 12, a control valve 14, and a power cylinder 15. The control valve 14 includes main valves 35 and 45 and a pilot interlock valve 27. The main valves 35 and 45 include a main inlet port 36, a main exhaust port 38, and cylinder ports 37 and 47. The pilot interlock valve 27 includes a pilot inlet port 28, an interlock port 30, and a signal port 29 which communicates with signal chambers 39 and 49. The control valve 14 is mounted on a motor vehicle transmission, and a mechanical actuator 16 moves between an extended position when the transmission is out of the neutral position and a retracted position when the transmission is in the neutral position. When the actuator 16 is in the extended position, the pilot interlock valve 27 is retained in an interlocked position to maintain the pressure condition existing in the signal chambers 39 and 49.

Abstract: A hydraulic pilot valve having an improved detent mechanism. The pilot valve includes a pair of lever operated plunger members which operate sliding valve members to control the opening and closing of a pair of work ports. Biasing members urge the plunger members to an extended position so as to maintain contact with the lever, and a pair of detent mechanisms act to hold the respective plunger members in the extended position. Movement of the lever to depress either of the plunger members and thus operate the respective valve members to open either of the work ports allows the respective biasing member to move the other plunger member to its extended position where it is held in place by its respective detent mechanism, thus holding the lever in its cocked position.

Abstract: A pair of inlet valves held closed in the neutral position of a valve actuator are opened under control of a valve operating force transmitted through a regulating spring in response to displacement of the valve actuator from the neutral position. The valve operating force applied is opposed by the pressure in a servomotor chamber to regulate the chamber pressure within a predetermined range above a limiting value of the valve operating force applied. Outlet valves are opened under a servomotor operating pressure higher than the pressure regulated by the inlet valves to control exhaust of fluid from the operating chambers.

Abstract: A manually operable hydraulic selector valve includes a plurality of two-way spool valves which are normally closed and are selectively shiftable individually or in pairs by a joy stick operator to open positions whereby motive fluid can be delivered to a given instrumentality such as the jack cylinder of a construction crane outrigger arm. The joy stick carries a conical disc which cammingly engages drive pin extensions of the individual spool valves. A positive stop for the conical disc is afforded by contact of the disc with the mounting plate of the selector valve. The selector valve is employed with an associated two-way directional control valve.

Abstract: A delaying device for a fluid system for operating a hydraulic motor (10) wherein electrically operated pilot valves (39,40) are actuated by limit switches (13,13') in the motor to control flow through pilot lines (37,38) into a control block (20) and then to and from the motor, said delaying device comprising a dashpot cylinder (46) connected to said pilot lines for momentarily continuing to supply fluid to said control block (20) after pilot valve (39 or 40) is shut off.

Abstract: A method of operating an hydraulic power system having a piston with opposing piston heads reciprocally mounted in opposing piston chambers, the piston being directionally responsive to a pair of control valves adapted to be sequentially opened and closed to actuate the piston for movement in opposite directions. The control valves each having a series of sequentially acting valve elements which control fluid flow to and from the piston, a condition being established in which the piston is at one end of its stroke and a first of the piston heads is under relatively high pressure and the other under relatively nominal pressure, the piston being driven to the opposite end of its stroke by first relieving the high pressure on the first of the piston heads to a nominal level and thereafter rapidly increasing the fluid pressure on the other of the piston heads, the piston and control valves working at all times against solid columns of fluid under controlled positive pressures.

Abstract: A control unit for controlling the supply of fluid to a hydraulic jack, the control device including a main valve having a valve member normally held closed by pressure in a pressure chamber, the pressure chamber being fed with fluid through a bore in a valve member of the main valve. In one embodiment, a valve spindle slides in the bore to stop it being blocked. In another embodiment, designed to control a double-acting jack, the main valve is associated with a second similar main valve the pressure chamber of which is fed from the first main valve instead of through a bore in its valve member.

Abstract: A pressure medium control means for hydraulic servo-steering devices with a pressure source and preferably a hydraulic pressure accumulator in which means there is provided a control valve having a four-way control and one or preferably two control pistons for selectively connecting the working spaces of a servo motor with a pressure source or return pipe to a reservoir, in which the servo motor is operably related to a power outlet member affecting the steerable wheels, with the power outlet member per se being connected with a power inlet member via a resilient, preferably pre-stressed coupling means, and in which the control piston or pistons is or are provided with reaction areas stressed by the pressures from the working spaces of the servo motor, or are in operative relation with respective reaction members and are actuable via actuating elements by virtue of relative movements between the power inlet member and the power outlet member.

Abstract: A power steering mechanism comprises distributing means for communicating fluid pressure to the compartments of a fluid motor associated with the steering linkage of the vehicle. Each distributing means comprises a ball valve member disposed in a chamber of a housing. The valve member is urged towards a first valve seat defined in a low pressure supply passage, by means of spring means, and towards a second valve seat defined in a high pressure supply passage by means of an extension of an actuating piston, said extension extending through the low pressure passage. The piston is moved by way of a sleeve disposed intermediate between the input and output members and connected thereto by means of a spline and screw arrangement. In response to a torque applied to the input member, the sleeve is allowed to move axially for displacing the piston and modifying the position of the valve member, thereby changing the value of the pressure transmitted to the associated compartment.

Abstract: A pair of fluid valves are formed in a common valve body. Movable pistons in the respective valves are normally biased by the fluid pressure input to closed positions whereby button-like or rod-like extensions of the pistons protrude through a top wall of the valve body to urge a pivotal valve operator to a neutral centered position. By manually pivoting the operator against one or the other of the extensions the respective pistons may be moved to open the respective valves.

Abstract: A system for precisely positioning a linearly movable output member incorporates an improved nonexpansion, bi-directional vane motor whose internal gas carrying chamber is configured to prevent radial vane reciprocation while the vanes of the motor are under pressure-generated side load. Position of the output member is electrically sensed and in response to the sensed position, pressurized gas flow to the vane motor is adjusted to precisely position the output member.

Abstract: A valve system for controlling the direction of flow of pressurized fluid. The valve system includes a valve housing, with an inlet port for receiving pressurized fluid therein, a first cylinder port and a second cylinder port. The housing is further constructed with first and second exhaust ports. Passageways connect the inlet port to the first cylinder port and to the second cylinder port. Passageways also extend from the first cylinder port to the first exhaust port and from the second cylinder port to the second exhaust port. A pair of pistons and corresponding poppet valves are slidable within the housing to control flow of fluid through the passageways. In one embodiment, the pistons and poppet valves are moved by communicating fluid pressure from the inlet port either above or below the pistons. In an alternative embodiment, the pistons and popper valves are mechanically actuated.

Abstract: A hydraulic system with a valve for controlling fluid flow to the two reversible hydraulic wheel motors in a hydrostatic drive vehicle includes a pair of valve spools axially slidable in bores in a valve body. Each spool has a pair of opposed notches. In one position of the spool, the notches provide separate paths for dual input flows to each of two passages to the wheel motors which differentially lock the wheel motors. In a second position, the notches act to exhaust the return flows in two passages to a single exhaust.

Abstract: A hydraulic pressure-regulating system for a dual-functioning servo motor having a control valve device that permits direct manual operation of the servo motor output function up to a predetermined force whereupon servo assistance arises when the fingers of the input member take up a set lost motion and directly contact and mechanically operate the control pistons. A prestressed spring holds the pistons in a neutral position to maintain a desired initial pressure in the system.