Abstract: An improved electrohydraulic servovalve has first and second valve spools mounted for independent sliding movement relative to a body in response to a common command signal. The valve has a first drive mechanism operatively arranged to cause a desired motion of one valve spool in response to the command signal, and has a second drive mechanism operatively arranged to cause a desired simultaneous similar motion of the other valve spool in response to the command signal. The improvement comprises a differential position sensing mechanism arranged to sense the relative positions of the two valve spools and operative to produce an output related to the difference therebetween, and an indicating device supplied with such output and operative to indicate substantially dissimilar relative positions of the spools.

Abstract: An actuator system is disclosed which modulates a linear output shaft associated with a working control valve or the like in response to a control signal input. The system includes a feedback control link, a pneumatic positioner, a pneumatically controlled hydraulic valving system and a hydraulic cylinder and piston assembly controlled by the hydraulic valving system. The hydraulic valving system includes a three-position, four-way valve actuated by pneumatic binary output signals from a signal conditioner which is in turn controlled by the positioner. Hydraulic flow to the three-position, four-way valve may also be controlled from the signal conditioner in response to positioner output for most effective actuation of the hydraulic cylinder and piston assembly. Failure modes are also disclosed with the present system. The resulting system exhibits extremely rapid response times and high accuracy with dynamic stability.

Abstract: A hydraulically actuable piston and cylinder unit comprising a hollow piston rod, slidably housing, at least partially, an elongate extension piece having a circular outer periphery, means to connect mechanically, the extension piece to the piston rod at the outer end of the latter remote from the piston head, at least one fluid passageway communicating between the annulus side of the piston head and the hollow interior of the piston rod, and a fluid seal carried by the extension piece and sealing against the internal periphery of the hollow piston rod, the arrangement being such that the seal always lies between the passageway and the outer end of the hollow piston rod.

Abstract: A bidirectional, multiple speed hydraulic actuator, including a differential piston (10, 24, 26). First and second ports (28, 30) are respectively in fluid communication with opposite sides of the piston and there is provided a pressure fluid supply line (40) along with a pressure fluid drain line (44). A control valve (14) is disposed between the ports and the lines and is movable step-wise through five positions providing for nulling of piston movement, and slow and rapid piston movement in either of two directions. A shifting device (60) is provided for the valve.

Abstract: A pressure-compensated directional control valve assembly suitable for use in hydraulic power steering systems of off-highway working vehicles. The valve assembly integrally comprises a control valve for controlling communication between two engine-driven pumps and a steering cylinder, and a pressure compensator valve for controlling the fluid pressure delivered from the pumps to the control valve. Constantly comparing its outgoing fluid pressure with the fluid pressure at control ports of the control valve, the pressure compensator valve delivers to the control valve the pressurized fluid from one or both of the pumps. Any excess of the pressurized fluid is directed from the pressure compensator valve to, for example, an implement hoist cylinder of the work vehicle.

Abstract: A hydraulic booster including a housing provided with an inlet hydraulically connected to a pump, a drain port hydraulically connected to a reservoir and a cylindrical bore, a power piston sealingly and slidably disposed within the bore and dividing the cylindrical bore into a working chamber and a drain chamber which is in normal communication with the drain port, an input member sealingly and slidably passed through a first end wall of the bore, the input member having an inner end sealingly and slidably interposed within the power piston and a valve seat formed on the inner end fact thereof, an output member sealingly and slidably passed through a second end wall of the bore and connected to the power piston at an inner end of the power piston the output member provided therein with a passage communicating with the inlet, a poppet valve member sealingly and slidably disposed within the power piston and cooperable with the valve seat for controlling hydraulic communication between the working chamber and th

Abstract: Precise control over outlet pressure as a function of valve position is obtained for operation of a servomotor by a rotary plug valve journaled at opposite ends in a control bushing having conduit channels in fluid communication with passage grooves in the plug valve to form a plurality of parallel flow paths between a pressure inlet and two directional outlets to the servomotor. The edge formed on the plug valve by a passage groove in only one of the parallel flow paths to each of the outlets is beveled to improve valve control precision.

Abstract: A pneumatic-hydraulic proportional valve actuator system is provided having a relatively simple and adjustable means of achieving two stroking speeds by the hydraulic actuator, high speed in normal operation and low speed for small position adjustments and for the final part of any large position adjustments. This prevents overshoot and instability of the actuator.

Abstract: The air intake of an internal-combustion engine passes through a throttle whose upstream and downstream sides are shunted by an idle-speed circuit. A vacuum-actuated auxiliary device has a vacuum line connected to the downstream side of the throttle. An injector-type jet pump connected in the idle circuit has an outlet connected to the downstream side of the throttle, a high-pressure inlet connected to the upstream side of the throttle, and a low-pressure input connected to the vacuum line. This jet pump serves as a vacuum amplifier during low-speed engine operation to ensure sufficient vacuum to drive the auxiliary load.

Abstract: A device for controlling hydraulic motors as in an aircraft "fly-by-wire" system wherein redundant hydraulic motors and controls are required to protect against failure of portions of the system or device. The device includes two master valves for controlling flow of fluid to and from the motors, one controlled by electrical signals from a command station and the other controlled mechanically through manual or automatic operation. There is a transfer valve for selecting which of the master valves is to be operable and to provide for smooth transition of control from the electrically controlled valve to the mechanically controlled valve.

Abstract: Each directional control valve of a load responsive hydraulic system supplies a flow of signal fluid to a work port channel thereof and pressurizes this flow of signal fluid to a predetermined pressure magnitude above the load actuating pressure in the work port channel to provide a synthetic signal pressure. Fluid logic is provided for the selection of the highest synthetic signal pressure from any of the directional control valves and for application of this highest synthetic signal pressure to an effective output operator for the control of the pressure and effective output of the pump.

Abstract: A hydraulic brake booster of the type utilizing pressurized fluid supplied to a hydraulically operated device comprises a flow regulating valve adapted to rapidly increase the pressure in a power chamber of the booster in response to actuation of a control piston and another flow regulating valve adapted to ensure supply of the pressurized fluid to the hydraulically operated device. In the brake booster, the first-named valve includes an annular recess formed on the control piston for permitting the flow of fluid supplied to the power chamber when the control piston is in an original position and blocking the flow of fluid to the power chamber when the control piston is moved, and an orifice for throttling the flow of fluid supplied to the power chamber in response to movement of the control piston.

Abstract: A drum brake assembly provides a pair of brake shoes which are movable by a hydraulic actuator to a braking position. The hydraulic actuator is carried by a backing plate and the pair of brake shoes is movable relative to the backing plate. A piston is slidably mounted within a bore on the hydraulic actuator and pressurized fluid communicated to the bore acts against the piston to move the piston and pair of brake shoes. A partition is also disposed within the bore to substantially define a secondary chamber which receives pressurized fluid from the bore. The partition is movably disposed within the bore and resiliently engaged with the piston so that increased pressure within the bore is transmitted to the piston via the partition and the resilient engagement. Moreover, the partition controls venting of the secondary chamber so that upon contact of the pair of brake shoes with a drum, backlash or retraction of the pair of brake shoes is limited.

Abstract: An anti-skid brake control device includes a servo mechanism for controlling pressure reducing operation of the device. The servo mechanism includes a constant pressure chamber connected to an engine intake manifold, a variable pressure chamber alternately connected to atmospheric pressure and vacuum in the engine intake manifold, and a vacuum pressure responsive valve including a flow restriction passage wherein, when the engine vacuum rises above a predetermined level due to engine brake operation, the restriction passage is actuated to restrict the vacuum flow to the variable pressure chamber to gradually carry out the pressure recovering operation of the anti-skid brake applied with the engine brake operation.

Abstract: A shock absorber of the kind having an infinitely adjustable damping characteristic comprises a main cylinder containing a piston fixed to a piston rod which extends from the main cylinder and liquid within the cylinder acting on the piston. The main cylinder has openings for the flow from it of the liquid upon movement of the piston in the cylinder and an adjustment device is provided for restricting these openings to provide the adjustment of the damping characteristic. The openings are situated in the peripheral wall of the main cylinder and are axially spaced apart from each other in positions in which they are successively passed over and closed by the piston as the piston approaches the end of its stroke at one end of the main cylinder in a damping movement. Thus the flow of liquid from the main cylinder is progressively further throttled by closure of the openings as the piston approaches the end of its movement.

Abstract: This invention is directed to fluid actuated apparatus for automatically restricting the flow of fluid in conduits leading to and/or from fluid actuated cylinder means for causing pivotal movement of a member, such as the turret carrying the boom and bucket of a backhoe, so that the speed of pivotal movement of the member is rapid during one portion of its pivotal movement but is automatically reduced during a predetermined portion of its subsequent pivotal movement, thereby minimizing failures of the components of the member and the fluid system and improving the braking action for reducing the speed of pivotal movement of the member. In one embodiment, both the flow of fluid to the operative fluid actuated cylinder and the flow of fluid from the inoperative fluid actuated cylinder are restricted substantially simultaneously by fluid restricting means so that the linear velocities of the rods of both cylinders are reduced substantially simultaneously by the fluid restricting means.

Abstract: An arrangement for controlling a hydraulic motor having a movable member with opposite faces to be impinged by pressure fluid, in which first valve means serve to direct pressure fluid against a respective one of the opposite faces to thus control the direction of movement of the movable member, and in which second valve means connected in a hydraulic circuit with the first valve means serve to control the speed of the motor in connection with control means actuated by the movable member for controlling the change of the speed dependent on the position of this member.

Abstract: A novel electropneumatic servoactuator utilizing a fluid pressure control signal chamber and a duty-cycle control valve alternating between a fluid supply pressure port means and port means venting the chamber to the atmosphere and controlling fluid pressure in the chamber. The control valve is driven by electromagnetic means comprising a coil responsive to an electrical input signal. Pressure responsive actuator means moves in response to the chamber pressure level for providing a mechanical position output. Feedback means senses movement of the actuator means and throttles the fluid flow in one of said port means. In another aspect of the invention, an auxiliary dump release valve armature means is also driven by the coil in preferably magnetic series circuit arrangement with the control valve and coil for rapidly porting the control chamber to the atmosphere for emergency release.

Abstract: A dashpot wherein a fitting including a calibrated bleed orifice formed therein is detachably retained in a valve body which houses a check valve and forms a part of a diaphragm chamber.

Abstract: The invention is concerned with an improvement in a load lifting apparatus which comprises a primary load member pivotally mounted about a generally horizontal axis on a frame, a tilt cylinder and a tilt piston movable relative to one another pivotally connected to the frame and the primary load member to provide impetus for pivotal movement therebetween, a secondary load member movable relative to the primary load member, a lift cylinder and a lift piston movable relative to one another connected to the primary load member and the secondary load member to provide impetus for linear relative movement therebetween, tilt cylinder valve means for controlling flow of pressurized fluid from pump means to the tilt cylinder and lift cylinder valve means for controlling flow of pressurized fluid from the pump means to the lift cylinder. The improvement of the invention provides protection which prevents the apparatus from overbalancing. The improvement operates by sensing a moment created by a load on the apparatus.

Abstract: A hydraulic brake booster of the type utilizing pressurized fluid supplied to a hydraulic power steering device, wherein a flow regulating valve is adapted to rapidly increase the pressure in a power chamber of the booster in response to actuation of the booster and another flow regulating valve is adapted to ensure supply of the pressurized fluid to the power steering device, and wherein an accumulator is adapted to surely operate the booster even when pressure supply to the power chamber from the fluid pressure source is accidentally blocked or stopped.

Abstract: A hydraulic system for use in extremely cold environments has a pump for passing hydraulic fluid from a reservoir to a hydraulic cylinder of a work element via a control valve that is positioned a relatively great distance from the hydraulic cylinder. Fluid pathways are provided for substantially continuously moving hydraulic fluid between the control valve and hydraulic cylinder during operation of the pump.

Abstract: A fail-safe fluid control valve including a first sleeve accommodated in and fixed to a valve housing, a second valve also accommodated in and fixed to the valve housing in parallel relation with the first sleeve, a first valve spool slidably accommodated in the first sleeve, and a second valve spool slidably accommodated in the second sleeve. The first and second sleeves are properly formed with grooves and ports while the first and second valve spools are properly formed with large diameter portions spaced. When there occurs such an abnormal condition that the first valve spool and the first sleeve are jammed or stuck to each other, the second valve spool is adapted to be moved for actuating the fail-safe control valve under entirely the same condition as a normal condition.

Abstract: A shock absorber of the kind having an infinitely adjustable damping characteristic comprises a cylinder containing a piston fixed to a piston rod which extends from the cylinder and liquid within the cylinder acting on the piston. The cylinder has openings for the flow from it of the liquid upon movement of the piston in the cylinder and means are provided for restricting these openings to provide the adjustment of the damping characteristic. The openings are situated in the peripheral wall of the cylinder and are axially spaced apart from each other in positions in which they are successively passed over and closed by the piston as the piston approaches the end of its stroke at one end of the cylinder in a damping movement. Thus the flow of liquid from the cylinder is progressively further throttled by closure of the openings as the piston approaches the end of its movement.

Abstract: An acceleration/deceleration device which, in order to achieve shockless acceleration/deceleration control in starting or stopping of the load by means of a hydraulic actuating circuit of the open circuit type, uses an amplification valve of a type such that the main flow rate may be amplified in proportion to the area ratio between a detection orifice installed in a pilot flow passage and a main orifice installed in the main flow passage and is constructed by combining the said amplification valve with a flow rate control valve for controlling the pilot flow and a control circuit for gradually changing the area of the opening of the main orifice.

Abstract: A co-axial, dual trigger valve mechanism for use in a nut runner, said valve mechanism being of such a construction as to permit low air flow initially so as to deliver only minimum acceptable torque to the nut with the result that the tool is caused to stall out at this low flow in cases where the nut has been properly pre-crimped and then upon further depression of the trigger full air flow will result causing the nut to be fully and properly installed. Conversely, if the nut has not been properly pre-crimped, the initial depression at the low pressure will cause the nut to be fully run all the way down thus indicating to the operator that the nut is improper and must be removed and replaced.

Abstract: A hydraulic brake booster includes a housing having a bore therein, a stepped power piston slidably disposed within the bore and forming at one side thereof a fluid chamber, a first passage communicating with a fluid pressure source, a second passage communicating with the fluid chamber, a third passage communicating with a reservoir, a first valve normally interrupting the communication between the first passage and the fluid chamber, and a second valve for controlling the communication between the fluid chamber and the third passage.The first passage is provided within the small diameter portion of the stepped power piston for reducing the sliding resistance force exerted upon the stepped power piston during the sliding movement thereof.

Abstract: A hydraulic system for a working machine of the vehicle type having a power steering mechanism and a hydraulically powered working implement, such as a back-hoe implement. A hydraulic valve is inclined in the power steering mechanism, and another hydraulic valve operates the powered implement. A flow control valve divides flow between the aforementioned two valves, and a pump supplies the flow in the system. Pressure relief valves are included in the system, such that one relief valve senses pressure in the power steering branch of the system, and that relief valve responds to the lowest hydraulic pressure, and a relief valve for the powered implement responds to a higher hydraulic pressure. Only a single hydraulic pump is required for the power steering and the powered implement.

Abstract: An accumulator structure for use in a hydraulic control system for controlling an hydraulic motor utilized to engage a friction device in a transmission including an accumulator piston mounted in a housing, a source of fluid pressure, a valve connected between the source and the motor. A first conduit connects the valve and motor, the first conduit including a fluid restriction, and a second conduit connects the valve and the accumulator. A third conduit is provided between the accumulator and the first conduit. The accumulator includes a counter-bored portion defining together with a reduced land portion on said piston, a passage which connects the second conduit to the third conduit when the piston is in the inactive position to provide a rapid fluid fill of the motor initially.

Abstract: A flow control apparatus for use in a servomotor to control the rate of the flow of air through a hub to a control valve. A push rod has a first section connected to the control valve and a second section through which an operator supplies an operational input signal. A truncated resilient disc holds the first and second sections of the push rod away from each other. A filter surrounds the second section and extends radially to fill the interior of the hub. A series of projections extend rearwardly from the truncated resilient disc along the exterior of the filter. When the operator desires to begin a braking sequence, an input force is applied from the operator through the second section into the truncated resilient disc to the first section to actuate the control valve. With the control valve actuated, air will flow from the atmosphere through the filter into the servomotor.

Abstract: A fluid motor for a backhoe or the like. A hollow motor cylinder is provided with upper and lower end plates to define a motor chamber through which a generally vertical shaft extends. The shaft is journalled for relative rotation and a first vane is located within the motor chamber and is secured to the shaft and sealingly engages the cylinder and the end plates. A second vane is located within the motor chamber and is secured to the cylinder and sealingly engages the shaft. Ports of a first set are interconnected for continual fluid flow between each other and open into the chamber adjacent one side of the second vane and include at least one port in each of the end plates. Ports of a second set are interconnected to each other and open into the chamber adjacent the other side of the second vane and include at least one port in each of the end plates.

Abstract: A positioning apparatus includes a master hydraulic positioning cylinder having a relatively long stroke capability and a train of additively connected, short-stroke pneumatic control cylinders for controlling the length of stroke of the master cylinder and thus the positioning of a variable-position tool such as a band saw. One end of the cylinder train is connected by a feedback rod to an extensible portion of the master cylinder. A connecting rod connects the opposite end of the train directly to the spool of a three-position servo valve which controls the flow of hydraulic fluid to and from opposite sides of the master cylinder. When air pressure is admitted to a selected side of a selected control cylinder, at least a portion of the train shifts initially in a direction to move the servo valve to an operating position to begin stroking the master cylinder in a desired direction.

Abstract: An automatic sliding door operator for a door mounted upon a door frame for sliding movement in a vertical plane between opened and closed positions includes a drive cylinder to open and close the door by means of a drive piston slideably movable within the drive cylinder between fluid inlets located at each end of the cylinder. Control means are provided to couple a first fluid inlet of the drive cylinder through a controlled source of fluid pressure and to exhaust the opposite fluid inlet continuously throughout an opening stroke of the door and for connecting the second fluid inlet to the source of fluid pressure and exhausting the first fluid inlet continuously throughout a closing stroke of the door. The closing and opening rates of the door is controlled by suitable exhaust metering means continuously metering the exhaust flow of fluid.