Abstract: A work vehicle including an articulated vehicle chassis having a front frame portion and a rear frame portion pivotally coupled together at a generally vertical pivot axis. The front frame portion carries a front axle and the rear frame portion carries a rear axle. A steering system includes at least one steering cylinder connected between the front frame portion and the rear frame portion. A power plant provides motive power to the work vehicle, and a transmission receives power from the power plant and provides power to the front axle and rear axle. The work vehicle further includes a secondary clutch interconnected between the transmission and the rear axle. The steering system is configured to disengage the secondary clutch to provide reactive steering, whereby the front frame portion tows the rear frame portion. The rear frame portion freely articulates relative to the front frame portion.

Abstract: A surgical instrument for supplying energy to tissue can comprise a jaw member comprising an electrode, wherein the electrode is configured to supply energy from a power source to captured tissue. The surgical instrument comprises a tissue-cutting element to transect the captured tissue. The rate of distal translation of the tissue-cutting element during the operational stroke may be regulated by a damper. The damper may have barrel and a plunger.

Abstract: An improvement to the component based hydraulic systems is an integrated electro-hydraulic actuator (EHA) that contains all components necessary to achieve power up, gravity return actuation of a lift mechanism such as the forks of a pallet truck. Further, improvements to known power-up, gravity-down component-based hydraulic circuits are described herein. The improvements provide for power up, gravity return functionality with fewer components as compared known systems. Finally, a method for controlling the EHA and/or hydraulic circuits described above is detailed herein and provides a user with maximum control of a lift mechanism during lower or “down mode,” but also provides for the least amount of energy consumption by the actuator.

Abstract: A fluid distributor apparatus includes a body having distribution ports; a spool adapted for controlling the distribution ports and mounted slidingly in a first sliding seat obtained in the body and communicating with the distribution ports; a copying-member mounted slidingly and sealed in a second seat obtained in the spool; and a supply system for a controlled supply of the fluid to the second seat, so that the copying-member slides in a controlled way. The supply system includes also a chamber containing the fluid and communicating with said the seat, and a pushing device of the fluid mounted slidingly and sealed in the chamber.

Abstract: A pneumatic control device includes a base comprising a reservoir, a first check valve for only allowing hydraulic fluid to flow into the reservoir, and a second check valve for only allowing the fluid to flow out of the reservoir; a hollow cylinder comprising a spring biased piston; a body mounted to the cylinder thereunder and releasably secured to the base, the body comprising a stepped-diameter passageway with a poppet mounted therein; and a cover releasably secured onto the poppet. In response to feeding pressurized air into the cylinder, the fluid in the reservoir flows out during a first stroke of the piston, and the fluid is sucked back into the reservoir during an opposite second stroke of the piston. In one embodiment, the fluid is for actuating a machine vise.

Abstract: A lifting mechanism has a continuously variable lifting mechanism valve, with a multi-position valve, by way of which a lifting cylinder can be made to communicate with a pump or a tank. In the flow path of the pressure fluid from the multi-position valve to a pressure chamber, effective in the “carrying” direction, of the lifting cylinder, there is a relief pressure limiting valve, by way of which a relief pressure can be proportionally set. During relief pressure regulation, a metering aperture, which is predetermined by the proportionally variable multi-position valve, is opened, so that the volumetric flow of pressure fluid to the tank is minimized via the pressure limiting valve.

Abstract: A hydraulic actuator for a hydraulic servomotor 4 is disclosed. The hydraulic servomotor 4 has a first chamber 5 and a second chamber 6 associated therewith. The hydraulic actuator is connected to a fluid source 2 and a fluid drain 3, and it comprises a valve assembly arranged between the fluid source 2 and the fluid drain 3 to control fluid pressures in the chambers 5, 6. At least one auxiliary valve 11 is fluidly connected between the valve assembly and the fluid drain 3, said auxiliary valve(s) 11 being of a kind which is normally closed in a de-energized state. In the case of a power cut off the auxiliary valve(s) 11 will close, thereby preventing fluid flow from the valve assembly towards the fluid drain 3. This causes a servomotor piston member 12 to be hydraulically locked in its instantaneous position, thereby locking the hydraulic servomotor 4. The valve assembly may be designed without taking the locking function into consideration.

Abstract: An actuating device for a friction clutch arranged in the drive train of a motor vehicle. The actuating device has a positioning servo arrangement with a pressure-medium power cylinder arrangement which acts on a disengagement bearing arrangement. There is provision, for assigning to a pressure-medium subsystem, made up of the pressure-medium power cylinder arrangement and a control valve of the positioning servo arrangement, a pressure compensating orifice which, at least when the positioning servo arrangement is in a holding state, permits a defined pressure-medium pressure compensating flow, in order to influence at least one positioning behavior of the positioning servo arrangement.

Abstract: A valve actuation system with cooperating pneumatic and hydraulic control features. Compressed pneumatic fluid is generated in a pneumatic fluid supply, and flows in response to requirements between a predetermined command signal and an existing position of a working fluid valve. Hydraulic fluid is pressurized by a pump, and stored within the system by an accumulator. A servo valve comprising a pneumatic fluid flow path and a hydraulic fluid flow path is included to facilitate the flow of hydraulic fluid through the servo valve hydraulic fluid path and a downstream actuator for the working fluid valve in proportion to changes in pneumatic fluid flow through the servo valve pneumatic fluid flow path. A saturated fluid feedback circuit is included to shut off the flow of pneumatic and hydraulic fluid during select periods, such periods typically coincident with static conditions within the actuator of the working fluid valve, thereby reducing pump duty cycle.

Abstract: A control apparatus for an industrial vehicle is disclosed. The vehicle has a rear axle that is swingable during straight travel of the vehicle and can be fixed during turning of the vehicle. A damper looks or unlocks the rear axle. A controller has a memory that stores a first value and a second value of an angular velocity rate that represents an angular velocity per unit time. The controller activates or deactivates the damper. The controller activates the damper to lock the rear axle when the angular velocity rate is greater than the first value. The controller deactivates the damper to unlock the rear axle when the angular velocity rate is kept smaller than the second value for a predetermined time period after the angular velocity rate has become smaller than the second value.

Abstract: An operation device for a friction clutch arranged in the drive train of a motor vehicle. The operation device includes a positioning servo arrangement with a pneumatic power cylinder arrangement. The pneumatic power cylinder arrangement acts on a clutch release sleeve arrangement. The positioning servo arrangement can be operated with a control valve that is connected to a pneumatic source depending on a command variable representing a desired position and an actual variable representing the axial position of the clutch release sleeve arrangement. The pneumatic power cylinder arrangement is arranged inside of the bell-shaped housing and the control valve is arranged outside of the bell-shaped housing or the bell-shaped housing is arranged at least partially inside of the bell-shaped housing, but is accessible from the outside and/or can be removed when the bell-shaped housing is attached to the combustion engine.

Abstract: For enabling a boom to be smoothly raised during the triple combined operation of boom-up, arm-crowd and bucket-crowd in a hydraulic circuit system for a hydraulic excavator, in a first valve group of a hydraulic valve apparatus (12), a variable throttle valve (70) is installed in a feeder passage (32) of a bucket directional control valve (21) downstream of a load check valve (32a), and a secondary pressure C as a boom-up operation command is introduced through a line (71) to a pilot control sector (70a) of the variable throttle valve (70) which sector operates in the throttling direction, so that when the secondary pressure C is 0 or small, the variable throttle valve (70) is fully opened and, as the secondary pressure C increases, an opening area of the variable throttle valve (70) is reduced to restrict the flow rate of a hydraulic fluid supplied through the bucket directional control valve (21).

Abstract: A pressurized fluid actuation system as provided for a surgical instrument. The system includes a double-acting fluid pressure actuator with an extension chamber and a retraction chamber separated by a piston for engaging a component of the instrument. An operating lever is pivotally mounted to the piston. The operating lever is also pivotally connected to a servo valve that has a valve spool. The valve is connected to a source of pressurized fluid and has first and second return ports for venting the fluid. The actuator extension and retraction chambers are connected with the valve for each communicating with the pressurized fluid source and with one of the return ports in response to the position of the valve spool. The system includes a feedback line communicating between the extension chamber and the valve to apply a force to the valve spool in one direction when the extension chamber is pressurized.

Abstract: A hydraulic sensor and pressure transducing apparatus is disclosed which is characterized by the use of a biased piston and valve element arrangement to translate the displacement of an actuator to provide a pressure signal proportional to the displacement being sensed. The piston is mounted in a bore provided with inlet and outlet ports. A valve element is positioned in the bore in an opposing resiliently biased relationship to the piston in communication between the inlet and outlet ports. A constant selected hydraulic flow is fed into the bore inlet through the valve element and out of the bore outlet port to develop a pressure on the inlet port side which is proportionally to the displacement of the piston as reflected by the biased force exerted against the valve element. An actuator is linked to the piston by a cam surface in a manner that permits the angular position of the cam operating on the piston to be reflected as a proportional pressure on the inlet side of the valve element.

Abstract: In a servo steering system for motor boats comprising a steering wheel which mechanically acts on the position of a hydraulic control valve, and a rubber cylinder connected to a hydraulic power unit by way of the control valve, the control valve comprises an additional adjustment unit which is connected to an autopilot unit and is controllable by this latter. In this way both normal servo-assisted hand-steering and autopilot steering are made possible in a simple manner.

Abstract: A valve positioning device capable of comparing the travel position of an output shaft of a diaphragm actuator or cylinder with the pressure level of a pneumatic input signal and further being capable of manipulating the pressure of a separate air signal piped to said diaphragm actuator or cylinder in order to correct any imbalance between said stem position and a given pneumatic signal level; wherein said valve positioning device is further capable of varying its dynamic response by built in adjustment means.

Abstract: A towveyor cart for use in hoisting an object and in particular an object having first and second interconnected portions from a first level to a fully raised level. The towveyor cart has control means which include a main control valve for simultaneously raising the jacks to an intermediate position between the lowermost position and the fully raised position and separate jogging valves for controlling each of the jacks separately between the intermediate and raised positions. In this way, both jacks can be simultaneously rapidly raised to the intermediate position and then independently jogged by the jogging valves to the final fully raised position. Horizontal adjusting means are provided so that a combination of horizontal and vertical adjustment for each jack, independent of the other jack, is obtained. Additionally, the towveyor cart is provided with an improved air reservoir which is mounted beneath the work platform of the cart as opposed to the conventional location which is on the platform.

Abstract: There is disclosed a hydraulically operated power steering system which comprises a reciprocating-type hydraulically operated cylinder unit for moving a steering link mechanism and having first and second chambers, a reservoir containing hydraulic fluid therein, a hydraulic pump feeding the hydraulic fluid in the reservoir to the cylinder unit, a control valve unit including a line coupled to communicate the hydraulic pump, a line coupled to communicate the reservoir, a valve cylinder having passages coupled between the first and second chambers to provide fluid communication therebetween, and a valve spool slidably arranged in the valve cylinder and reciprocatingly movable in response to rotation of an input shaft, the cylinder unit including therein right and left reaction chambers to which opposite ends of the valve spool are exposed, the reaction chambers being communicated with the respective first and second hydraulic chambers through orifices, and a valve for dividing the left reaction chamber into a r

Abstract: A fault detector for a triplexed mechanical or hydromechanical system which provides for improvement in cost, reliability and weight over previously known balance beam arrangements for achieving redundant two-channel operation to provide a fail-operating first failure mode for operation of aircraft components which require reliable operation for flight safety. The fault detector for a triplexed mechanical or hydromechanical system has a tripodal summing member which receives three mechanical position signals in three different channels with the tripodal summing member retaining a position perpendicular to the force transmitted by the tripodal summing member in response to the position signals and tipping when one of the input signals deviates significantly from the other two.

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: The elevation of a tool carried by an implement towed by a tractor is determined by a hydraulic motor mounted on the implement adjusting the wheel height. A servo valve mounted on the tractor responsive to line pressure controls the hydraulic motor. An operator actuated vent valve mounted on the tractor vents line pressure to control the servo valve. A tool elevation responsive feedback vent valve mounted on the implement increasingly vents line pressure as the hydraulic motor changes tool elevation, to negate the effect of venting by the operator actuated vent valve. When hydraulic motor movement equals movement of the operator actuated vent valve, the feedback venting equals that of the operator actuated bent valve. A second negative feedback on the servo motor pistons then returns the servo valve to neutral closed position and change in tool elevation stops.

Abstract: A device for controlling an adjustable arm 1 has an operating circuit 10 including a movable valve 3 with two control mechanisms 11, 12 bidirectionally actuated by pressure. A control circuit to activate the movable valve is connected to a pressure source 19, to the two control mechanism 11, 12, and to an adjustable throttle 22 attached to one of the two control mechanism 12. The control circuit also includes an adjustable throttle 24, series connected adjustable throttles 27, 28 attached to the other control mechanism 11 and a fifth adjustable throttle 57. The fifth throttle is used to create an additional actual value input. An adjustable control valve 53 employs the desired and actual value inputs supplied by the adjustable throttles in various ways by interconnecting the throttles with the control devices and a pressure ratio valve 45 so that the system responds to applied force, position or both.

Abstract: An apparatus for controlling the movement of a movable element as a working circuit (10) with a directional control valve (3) equipped to control devices (11, 12) which can be pressure activated in two directions. A control circuit (29) which can be connected to a fluid source (19) is used to activate the directional control valve for which the control circuit is connected to the two control devices and has an adjustable first choke (24) connected to one of the two control devices (12), a second choke (22) which is similarly adjustable and connectable to the same control device, and third and fourth adjustable chokes (27, 28) which are connectable to the other of the two control devices (11). The first and third chokes are connectable further to a storage tank (7) and the second and fourth chokes are further connectable to a pressure source. A proportioning pressure valve (45) can be connected to the other of the two control devices (11). The first and third chokes are connected to a pilot valve (38).

Abstract: An apparatus for positioning an adjustable member as a function of a command signal and a control condition, especially for the positioning of a hoisting mechanism on a tractor or the like, comprises an operating circuit and a control circuit. The operating circuit has a bidirectional positionable valve with a valve side and first and second control devices for regulating flow of pressure medium from a supply tank to the adjustable member. The control circuit connects a control pressure medium source to the control devices at first and second junctions and includes adjustable throttles and a flow-regulating valve. A first adjustable throttle is connected between the supply tank and the first junction. The second adjustable throttle is connected between the control pressure medium source and the first junction and in series with the first adjustable throttle.

Abstract: A control-circuit throttle valve assembly coupled to and regulating a hoisting unit correcting element or final control element of a tractor via a mechanical coupling including a throttle housing, a flow restrictor throttling body shiftably mounted in the throttle housing, the throttling body having a guiding edge portion, a control conduit with a circular cross-section communicating with the throttle housing, the control conduit including a pass-through area, and a run-off conduit communicating with the throttle housing, the guiding edge portion at least partially closing off communication between the control circuit and the throttle housing through the pass-through area upon shifting of the throttling body within the throttle housing such that the pass-through area is throttled as a linear function during operation of the hoisting unit.

Abstract: A control system for a valve actuator which is subject to oppositely directed displacement due to thermal expansion and spring forces has sensor switches which detect successively greater amounts of compression of a spring which compresses to accommodate thermal expansion of the valve, its stem and seat when the valve is seated in closed position. A position servomechanism which is responsive to the position of the stem and a control signal operates a motor for advancing and retracting the stem.

Abstract: A device for the positioning of an adjustment element dependent upon a desired level and the actual level, particularly for the adjustment of a hoist gear train of a tractor, a combine or the like, has an operating circuit 10, which has a multi-way valve 3 pressure-operated in two directions, and a control circuit 29 for the operation of the multi-way valve, connected to a pressure source 19, which is connected to two control devices 11, 12 of the multi-way valve. Circuit 29 has two adjustable series-connected throttles 22, 24, connected to one of the two control devices. The first throttle 24 is also connected to a tank 7 and the second throttle 22 is also connected to pressure source 19. Both throttles have the same maximum flow-through cross section, and are adjustable in the same manner. Third and fourth throttles 27, 28 are provided, one being between the pressure source and control device 11, and the other between the control device and tank 7.

Abstract: A master/slave fluid-pressure apparatus having a first valve respective to angular movement of a master arm for producing fluid pressure which is applied as a pilot pressure to shift a closed-center three-position directional valve in one direction, which then allows a fluid-pressure actuator to be operated to cause a slave arm to follow the master arm in angular motion. The angular movement of the slave arm actuates a second valve coacting therewith to develop a fluid pressure which is applied as another pilot pressure to the directional valve. When the fluid pressure from the second valve reaches a predetermined point, the directional valve is shifted in the opposite direction to stop operation of the fluid-pressure actuator. The first and second valves may either be pressure reducing valves or relief valves.

Abstract: A hydraulic brake booster includes a booster piston axially slidable in a bore of a housing and delimiting therein a boosting compartment, and a brake pedal responsive operating element which partially extends into the boosting compartment to act as a plunger therein. A control valve has a valve body which is stationary relative to the housing and a valve member which is slidably received in the valve body and controls communication of a pressure chamber with sources of control fluid at reference pressure and at control pressure, the pressure in the boosting compartment being proportionate to the pressure in the pressure chamber.

Abstract: A multi-way valve for precisely controlling supplying pressure to a load device, comprising a housing and a control slide slidably mounted in the housing. The housing has annular, internal passages axially spaced along the length of the housing, with first and fifth passages located on opposite sides of second, third and fourth passages in fluid communication with a supply tank, the load device and a fluid pressure source, respectively. The control slide is slidably mounted in the passages and has parts axially spaced along the slide and axially separated by annular grooves, and an internal, longitudinal passages. First and second springs are coupled to opposite ends of the slide and bias the slide to a middle, rest position. First and second control chambers are located in the housing adjacent the slide opposite ends for applying varying pressures to the slide opposite ends.

Abstract: An arrangement for controlling the lifting mechanism of a tractor or a harvester or a harvester combine comprising a hydraulic actuator (17) connected to the lifting mechanism and controlled by a control valve (19) leaving a hydraulically controlled spool arranged in the bridge diagonal (27-19-27') of a hydraulic bridge circuit (23, 24, 25, 26), in the bridge branches of which two actual force value transducers (41, 42) for generating hydraulic signals proportional to the position of the lifting mechanism and desired force value setting means (32, 52) are respectively located for controlling the hydraulically controlled valve (19). An additional control valve (33) or throttle unit (53a) is provided for selecting one or both of the actual force transducers and if desired for controllably mixing the actual force signals.

Abstract: A control circuit throttling valve provided as a controlled dimension receiver in a hydraulic circuit for the control of a final control element, particularly for the control of a lifting unit of a tractor. The valve performs a receiver function under control of a mechanical coupling coupled to a moving part of the final control element which changes the valve throttling section and is adjustable and includes a casing having a control connection and a discharge connection and a movable throttling body provided in the casing in relation to the control connection and the discharge connection such that upon linear or rotational movement of the body it is possible to independently derive an adjusting function and a receiving function.

Abstract: An improvement in apparatus for lifting an agricultural implement carried by a tractor provides for automatic rapid level adjustment of the implement relative to the terrain under control of a valve system which comprises a regulator valve controlling inlet flow to the pump responsive to a comparator valve carried by the implement. A continuous throtted flow from the regulating valve to the comparator valve is maintained at constant pressure tending to open a valve in the comparator while a sensor or feeler contacting the ground serves to effect a greater or lesser opposing force. A servo valve is provided which effects a back pressure acting together with feeler actuation. An equilibrium position of the valve determines the level to which the implement is changed, holding it constant on level ground until the feeler is actuated by encountering a rise or fall in the terrain. The construction provides for varying the elevation of an implement by either raising it or lowering it to meet rise or fall of terrain.

Abstract: An apparatus for restricting the velocity of movement of the piston of a servo-controlled operating hydraulic unit, when the piston approaches at least its one end position in the cylinder, by means of a hydraulic sensor fixedly mounted on one of the machine parts which is shifted with respect to each other by means of the operating hydraulic unit, and is coupled by the intermediary of a non-return valve to the servo-circuit. When the piston of the operating hydraulic unit approaches its end position in the cylinder, the hydraulic sensor is actuated by the second of the above-mentioned machine parts, whereby a pressure is established in the cylinder of the hydraulic sensor which exceeds the servo-pressure. A valve senses the pressure difference between the servo-pressure and the pressure established by means of the hydraulic sensor and throttles the servo-flow to the main valve of the operating hydraulic unit the main valve thereby throttling the pressure medium supply to the operating hydraulic unit.

Abstract: A fluidic Repeater, includes a rotary transmitter, a responder, and a rotary feedback.Various constructional features useful in conjunction with the system are disclosed.

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 valving system for regulating the pressure of the fluid within a hydraulic actuator of the type having a hydraulic cylinder and movable piston therein that separates the cylinder into a first and second chamber comprises sensing apparatus in fluid communication with the first chamber of the hydraulic actuator cylinder. The sensing apparatus senses the differences in pressure between the fluid within the first chamber and the fluid in the second chamber. The valving system further includes a pressure regulator for regulating the pressure within the first chamber in response to the sensed pressure difference. Apparatus is also included for communicating the magnitude of the sensed pressure difference to the pressure regulator.

Abstract: Two fluid passages are connected through flow restrictors to a fluid supply. Downstream of the restrictors the fluid supply has a drooping pressure-load characteristic. Venting means for the fluid passages comprises vent openings therein downstream of the restrictors and variable position obstructor means cooperating with vent openings to vary venting and thereby vary fluid pressures in the fluid passages.Fluid conduits connect these pressure outputs to a double acting piston moving in a cylinder whose opposite ends are connected to the fluid conduits. The piston and cylinder form the responder of the system.A receiver is formed by a piston and cylinder or other fluidic motor remotely fluidically connected to the responder, the motor driving a load.A feedback means controlled by the position of the responder piston and/or the load varies pressure in the fluid conduits by variably venting same.

Abstract: A force balance instrument providing precision control of pneumatic actuators in response to command pressure signals independent of external forces on the actuator shaft. The instrument includes a high gain signal detection circuit in combination with one or two pilot operated output valves. In the case of two output valves inverse "push-pull" control of a double acting pneumatic actuator is provided. Full supply pressure differential can be developed across the piston of the actuator, permitting to minimize the size of the actuator for any specified output force.The positioner proper controls the position of valve actuator system through a stem connector arm and a feed-back spring. A force balance condition is initially established between the feedback spring and the force of a rolling diaphragm controlled piston assembly for the range of signal pressure P.sub.1 to be used. Any change in this force balance condition because of a change in signal pressure P.sub.

Abstract: A fluidic system for stabilizing movement of a body subject to oscillation at its natural frequency, such as a tank-mounted gun, with appropriate circuitry and controls for notch filtering control output signals at the natural frequency.

Abstract: A fluidic repeater comprising: transmitter means, a responder, a single line for transmitting pressure signals between said transmitter means and responder, and means including a source of pressure fluid for causing a pressure fluid to flow through said line.

Abstract: A detector for sensing the compressor inlet temperature of a gas turbine engine and for producing an output pressure signal which is used by the fuel control of the engine. The magnitude of the output signal is determined by the position of a valve which changes positions in response to changes in temperature. The response time of the detector is made faster by causing a feedback pressure which acts on the valve to initially change at a slower rate than the output pressure (i.e., to lag the output pressure) when the output pressure changes as a result of temperature variations. The invention can be incorporated either in a self-contained sensor or in an add-on unit which can be retrofitted to existing sensors having relatively slow response characteristics.

Abstract: A fluid repeater system may be balanced so that displacement of the load has a desired correspondence to displacement of the transmitter. This may be done by making the fluid resistance offerd to fluid flowing along a path from the source to the reservoir and through the feedback controlled directly by the load, exclusive of the resistance offered by such load feedback, approximately equal to that offered to fluid flowing along a path from the source to the reservoir and through the transmitter, exclusive of the resistance offered by such transmitter.

Abstract: A valve actuator is disclosed having a servo-motor which regulates the position of a main valve that controls steam supply to a turbine. A hydraulic input signal acts on a pilot valve within the valve actuator body to move a valve spool in response to the input signal. Movement of the valve spool permits oil to flow into a cylinder in which the servo-motor is located. The flow of oil into the cylinder causes a piston which is a part of the servo-motor to move upwardly. Movement of the servo-motor is regulated by a cam and follower arrangement which transfers the motion of the servo-motor to a valve sleeve. The valve sleeve, which has a differential piston area, shuts-off the supply of oil to the servo-motor. The cam and follower arrangement provides for a linear correlation between the hydraulic input signal and the operation of the servo-motor. Increased closing forces provided by the differential piston reduce vibration of the valve sleeve and the servo-motor.

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 dynamic performance of hydraulic apparatus including a fluid-operated actuator controlled by a servo-controller, is improved by providing phase lead compensation to the controller in response to movement of the movable element of the actuator so that the low frequency response of the apparatus is raised.

Abstract: Disclosed is a hydraulic servomechanism wherein the motion of a driven element is synchronized with the motion of a command element by detecting any phase difference between the movement of the driven element and that of the command element, controlling the flow rate of a hydraulic fluid being fed to the driven element with a directional and flow control valve in proportion to the detected amount of phase difference and also controlling the flow rate of the hydraulic fluid being fed to the hydraulic servomechanism with a pressure compensation valve in proportion to the variation in the load exerted on the driven element.

Abstract: Two fluid passages are connected through flow restrictors to a fluid supply. Downstream of the restrictors the fluid supply has a drooping pressure-load characteristic. Venting means for the fluid passages comprises vent openings therein downstream of the restrictors and variable position obstructor means cooperating with vent openings to vary venting and thereby vary fluid pressures in the fluid passages.Fluid conduits connect these pressure outputs to a fluid to mechanical translator comprising a double acting piston moving in a cylinder whose opposite ends are connected to the fluid conduits. The piston and cylinder form the responder of the system, which may be adjacent the mechanical to fluidic translator and form part of the transmitter.A feed back means controlled by the position of the responder piston and/or the load varies pressure in the fluid conduits by variably venting same.

Abstract: Two fluid passages are connected through flow restrictors to a fluid supply. Downstream of the restrictors the fluid supply has a drooping pressure-load characteristic. Venting means for the fluid passages comprises vent openings therein downstream of the restrictors and variable position obstructor means cooperating with vent openings to vary the venting and thereby vary fluid pressures in the fluid passages.Fluid conduits connect these pressure outputs to a piston moving in a cylinder whose opposite ends are connected to the fluid conduits. The piston and cylinder form the responder of the system. A feed back means controlled by the position of the responder piston and/or the load varies pressure in the fluid conduits by variably venting same.The feedback means includes variable cross-section surface pasages, e.g. sloping grooves, in the responder piston or fluidic load piston or both. Alternatively or additionally a separate feedback piston may be connected to the receiver or load piston.

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.