Abstract: A hydraulic control system includes a first hydraulic cylinder, a second hydraulic cylinder, a fluid supply apparatus, a first control valve bank, a second control valve bank, a third control valve bank, and a first check valve. The first control valve bank is configured to independently control the first hydraulic cylinder; the second control valve bank is configured to independently control the second hydraulic cylinder; and the third control valve bank is configured to synchronously control the first hydraulic cylinder and the second hydraulic cylinder. Synchronous volume control is implemented through series connection of the hydraulic cylinders, and has quite high synchronization precision, which is measured to be up to two percent.

Abstract: A centre seeking actuator having an outer cylinder, a slave cylinder slidably disposed within the outer cylinder, and a rod assembly having a piston slidably disposed within the slave cylinder and a rod extending from the piston to a point outside the outer cylinder. One or more first dynamic seals are arranged to act on a side wall of the rod to inhibit working fluid leaking from the outer cylinder, and one or more second dynamic seals are arranged to act on a sidewall of the slave cylinder to inhibit working fluid leaking from the outer cylinder.

Abstract: The jack-type lifting system includes a valve for modifying a maximum force value of a lifting jack activated by a protrusion for determining a determined portion such as the beginning of the extension stroke of the lifting jack. Thanks to the modification of the maximum force value, a pressure source thus applies the full force of the lifting jack after a start-up stroke so as to protect a lock of a reverser cowl which has been forgotten during maintenance.

Abstract: A hydraulic control apparatus for construction machinery, includes an accumulator to accumulate a high-pressure hydraulic oil discharged from a boom cylinder for driving a boom of the construction machinery, a hydraulic pump connected to the accumulator and driven by the high-pressure hydraulic oil, a pressure sensor configured to detect a pressure of the accumulator, and a control unit connected to the accumulator and the hydraulic motor and configured to control operations of the accumulator and the hydraulic motor, and having a determiner that receives a pressure value of the accumulator and number of revolution of the hydraulic motor to determine whether or not the hydraulic motor fails when the hydraulic oil accumulated in the accumulator is supplied to the hydraulic motor.

Abstract: The invention relates to a launching cylinder of a catapult and to a catapult. The launching cylinder comprises a frame inside which are a pneumatic pressure space for launching purpose and a hydraulic pressure space for returning purpose. The pressure spaces are separated from each other by means of a piston assembly.

Abstract: An emergency opening system (1) of an aircraft cabin door (3) mounted in an aircraft fuselage structure (4) by means of a hinge arm (2). An actuator (7), designed to assist the opening of the aircraft cabin door (3) against the force of gravity by means of a gas operated actuating rod (8) is mounted with its fix end (9) to said hinge arm (2) and said actuating rod (8) is connected to an actuator joint (10). A fork lever (24) is linked to said actuator joint (10). A bell crank (13) is respectively pivotable mounted to said hinge arm (2) and to said actuator joint (10) for the fork lever (24). At least one coupling lever (12) is pivotable joint to said fork lever (24) at at least one coupling joint (14). Said at least one coupling lever (12) is mounted in at least one hinge (18) of the hinge arm (2) by means of a respective bolt (26), said bolt (26) being drivingly connected to said aircraft cabin door (3) for rotation of said aircraft cabin door (3).

Abstract: The invention belongs to the field of single-effect hydraulic cylinders. It relates to a device that makes it possible to limit the pressure in the pressurization chamber of a single-effect cylinder when the rod thereof is in a particular range of longitudinal positions of safety, while respecting the operating safety of the device, that is, in the case that the power supply of the pilot valves of the distributors and of the hydraulic pump is cut, the rod of the cylinder remains in its position if this position does not lie within the safety position range.

Abstract: A power steering device for a vehicle which is disposed in the transmission path between a steering handle and a steerable vehicle wheel, comprises a servo cylinder having two pressure chambers, which are separated by a working piston and are each connected to a pressure supply unit. A valve plunger, which seals a bypass channel between the pressure chambers, is movably disposed on the working piston. Furthermore, an adjustment bushing comprising an adjustment section is disposed in the servo cylinder, the valve plunger being moved against this section upon approaching an axial limit position, thereby opening the bypass channel. The adjustment bushing is clamped into the servo cylinder, yet held displaceably, wherein, on the adjustment bushing, a sealing section is provided, which is to be moved into a sealing position with the working piston so as to interrupt the flow connection between the pressure chambers.

Abstract: A fluid actuator with fluid limit valves (550, 551) and adjustable mechanical limits enables the construction of fluid linkages which are able to completely replace mechanical linkages. In a fluid circuit comprising of two or more fluid actuators, the pistons (102) of the fluid actuators can become uncorrelated when fluid leakage occurs. At the piston (102) extension and retraction limits, fluid limit valves (550, 551) open. The open fluid limit valves (550, 551) allow fluid to bypass pistons (102) and/or allow fluid from an external source to compensate the fluid leakage. The fluid bypassing pistons (102) at their extension or retraction limit and/or externally supplied fluid forces the uncorrelated pistons (102) to reach their extension or retraction limit as well. The fluid actuator with adjustable mechanical limits have one or more additional pistons (686, 688), which have an adjustable separation from the main piston (102) or end of cylinder.

Abstract: An method for estimating actuator position includes the steps of receiving fluid pressure data signals from a plurality of fluid pressure sensors (31), receiving spool position signals from at least one spool position sensor (33), and receiving actuator position data signals from at least one actuator position sensor (35). Corrected flow rates to and from an actuator (21) are determined with each corrected flow rate being based on fluid pressure data signals, the spool position signals, and an error-correction factor, wherein the error-correction factor is a function of the fluid pressure data signals and the spool position signals. An estimated actuator position is determined wherein the estimated position includes a kinematic component and a dynamic component. Adaptive gain factors are applied to calibrate the estimated actuator position to the actuator position data signals from the actuator position sensor.

Abstract: An actuator includes a hollow cylinder which has a first portion and a second portion. The inner diameter of the first portion is larger than that of the second portion. A piston is inserted in the cylinder. The actuator has a gas generator which supplies a gas into the cylinder to move the piston toward the first portion. The seal member keeps airtightness between the piston and the cylinder when the piston stays in the second portion and flows the gas when the piston stays in the first portion. A hollow stopper is arranged in the first portion and stops the piston. The stopper has a vent groove which is provided on the inner surface and connects the interior of the cylinder to the open end. A piston rod is jointed to the piston and housed in the cylinder. The piston rod moves along the axis with the piston.

Abstract: A hydraulic drive (1) has a position selection device (2) in communication with a control valve (3) which, as a function of the actuation of the position selection device (2), controls the connection of an actuating cylinder (8) with a hydraulic fluid source (5) and a reservoir (6). A correction device provides a synchronization between the position of the position selection device (2) and the position of the actuating cylinder (8). The correction device has a sliding valve means (15) which detects a reference range of the actuating cylinder (8) and an on-off valve means (16) effectively connected mechanically with the position selection device (2). The on-off valve means (16) is open when the position selection device (2) is in the reference range and is closed when the position selection device (2) is not in the reference range.

Abstract: An emergency opening cylinder of a passenger door of an airplane is provided. An existing emergency opening cylinder is adapted at the lowest expenditures and with an insignificant increase in weight with respect to its operating characteristic to the load situation of an emergency opening of the door against the force of gravity. A ventilation bore of the emergency opening cylinder leads into a collecting chamber which has an outlet valve controllable by a control.

Abstract: A hydraulic fluid diverting arrangement for a utility vehicle provides additional pressurized hydraulic fluid supply to an installed backhoe attachment by diverting hydraulic fluid from the unused rockshaft or three-point hitch of the utility vehicle. A solenoid operated valve manifold is switch actuated by contact from the backhoe during installation of the backhoe to the utility vehicle and diverts hydraulic fluid flow from rockshaft hydraulic cylinders to backhoe hydraulic cylinders. The system increases the available horsepower to the backhoe by using hydraulic fluid otherwise dedicated to the idle rockshaft.

Abstract: An output shaft is connected to a piston rod of a fluid pressure-driven linear cylinder through a converting mechanism for converting linear thrust of the piston rod into rotational torque and converting operation of the converting mechanism is controlled by operation setting means having a cam groove and a cam follower to thereby causing the output shaft to carry out linear motion and swinging rotation. A driving speed of the piston can be changed by adjusting fluid pressure acting on the piston in a linear motion area and a swinging area of the output shaft respectively.

Abstract: The hydraulic system for actuation of the mud valve of a measurement-while-drilling tool is characterized by a hydraulic actuator having a piston operatively connected to the mud valve of a measurement-while-drilling tool, which hydraulic actuator incorporates an internal by-pass which, cooperatively with movement of the piston, opens to unload hydraulic pressure from the system at either end of stroke of the piston. Return from the by-pass to the pump may be restricted so as to maintain some hydraulic pressure on the piston at end of stoke so as to prevent movement therefrom by external forces. The hydraulic system may include high pressure means, strainer means and means to equalize pressure between hydraulic system pressure and pressure external of the system.

Abstract: The downhole pump has a barrel with a reciprocating plunger therein. The barrel has a first one-way valve, while the plunger has a second one-way valve. A barrel chamber is formed between the two one-way valves. The barrel chamber expands when the reciprocal movement between the plunger and the barrel is an upstroke movement and then contracts when the reciprocal movement is a downstroke movement. A bypass channel is provided between the barrel and the plunger so as to provide communication around the plunger and its one-way valve. The bypass channel is open when the reciprocal movement is near an end of the upstroke movement. When open, pressure across the plunger can equalize and gas inside the barrel chamber can vent around the plunger and/or pressure can equalize across the plunger one-way valve so as to prevent gas lock and minimize stress on the sucker rods.

Abstract: A valve system for use with a tube jetting apparatus used for cleaning the interior surfaces of tubes such as those in heat exchangers. The apparatus includes a piston housing having a piston assembly slidably disposed therein. The pressure relief assembly also includes a differential pressure relief valve which is connected to the piston housing to relieve pressure therein as the piston moves within the housing.

Abstract: Vehicle suspension apparatus operating between the sprung and unsprung masses of a vehicle includes a pendular anti-roll bar connected to the vehicle, and a pair of links which connect the bar to the wheels. One and the other link, respectively, is extensible and inextensible, with the extensible link comprising a selectively controllable hydraulic piston-cylinder assembly having first and second flow paths, and valve means which upon command automatically locks the piston at a midstroke position, depending on the flow of fluid in the passages. The flow paths allow the user to select either of two roll stiffness levels (i.e., high and low) and provide automatic convergence of the piston to its locked midstroke position (high roll stiffness hard ride) upon command.

Abstract: A hydraulic platform lift for use on trucks and truck trailers has two hydraulic cylinders, one on each side of a door. The cylinders are phasing cylinders in that one cylinder is larger than the other cylinder by a specific ratio. The cross-sectional area of the fluid in the rod end of the larger cylinder minus the area of the rod is equal to the cross-sectional area of the smaller cylinder. A connecting line interconnects the rod end of the large cylinder with the cap end of the small cylinder. Hydraulic fluid can be directed by a controller into the cap end of the large cylinder or the rod end of the small cylinder. For upward movement, hydraulic fluid is forced into the rod end of the small cylinder. This in turn forces hydraulic fluid through the connecting line into the rod end of the large cylinder, thereby raising both pistons.

Abstract: Hydraulic fluid is replenished in a pulsator chamber of a fluid driven pulsator pump by having the power plunger in an upstanding bore with spaced seals. The power plunger is withdrawn upon each stroke vertically upward. As it is withdrawn past seals, any gas within the pulsator chamber may be purged or bled into an annular space and there out into a reservoir and scrubbing chamber. Additional hydraulic fluid will flow into the pulsator chamber. Upon the down stroke of the plunger an exact amount of volume will be displaced within the pulsator chamber. Adjustment of the product pumped on each stroke is by sacrificing a measured amount of the pulsator liquid into a sacrifice chamber. The amount of liquid which flows into the sacrifice chamber upon each down stroke and out of the chamber on each upstroke is adjusted by adjusting the movement of a floating piston by a micrometer rod.

Abstract: The hydraulic power steering apparatus of the present invention has plungers being installed movably at part of a casing of a hydraulic control valve and a reaction chamber being formed at one side of the plungers, and varies hydraulic pressure to be supplied to a hydraulic pressure reacting portion for generating restriction force corresponding to supplied hydraulic pressure according to vehicle speed and quantity of relative movement between a valve body and a casing of hydraulic control valve, thereby the supplied hydraulic pressure being increased as the vehicle speed becomes higher and steering angle becomes larger.

Abstract: A hydraulic door opening or closing device comprises a hydraulic fluid pump motor having two ports connected to each end of integral dual manifold and operating cylinder apparatus by way of two branch fluid lines. One branch line is fluidly connected to a particular end of the operating cylinder by way of a directional flow valve. The other branch line to the same end of the cylinder is fluidly connected to the cylinder by way of an associated manifold. Fluid communication with the cylinder through the manifold is accomplished by providing a plurality of valved openings linearly disposed along the end of the cylinder between the manifold and the cylinder. As a piston of the operating cylinder passes these openings, a door coupled to the piston is automatically slowed as fluid on the drive side of the piston is returned through the openings to the hydraulic fluid pump.

Abstract: Miniature engine operated by an expanding gaseous fluid, which comprises a cylinder (18), piston (20) and inlet valve (29), the upper part of the piston (20) cooperating with a radially expansible resilient diaphragm (28), which is secured to the piston (20) and performs momentarily a pneumatic seal-engagement function along the periphery of said cylinder (18) during the gaseous expansion phase.

Abstract: Small-sized engine operated by an expanding gaseous fluid, which comprises a cylinder (18), a piston (20) and an inlet valve (38), the upper parts of the cylinder (18) and the piston (20) cooperating momentarily with a perforated (29) resilient membrane (28) circumferentially secured to the cylinder (18) and performing the functions of a pneumatic seal temporarily.

Abstract: A bleed circuit for a backhoe boom cylinder which minimizes cylinder pressure during over-center movement of the boom while permitting the maintenance of sufficient cylinder pressure during other boom operations. The boom cylinder is provided with a retract port, a head end port, and a small bleed port with a bleed line connecting the bleed and head end ports. As the boom cylinder crosses over-center, the fluid pressure in the retract side of the boom cylinder may be transmitted from the rod end to the head end of the cylinder thereby reducing cylinder pressure and improving the over-center controlability of the boom.

Abstract: The cylinder for a two cycle engine includes at least a port opened and closed by a piston in the cylinder the port being divided into a plurality of port portions by a rib extending longitudinally of the cylinder. The inner surface of the cylinder is formed with elongated concave recesses at the respective ends of the rib extending in the direction of extension thereof for regulating the pressing force per unit area of honing process. Each of the concave recesses has preferably substantially the same width as the width of the rib and the sum of the lengths of the concave recesses is preferably substantially the same as the length of the port.

Abstract: An improved mechanism is provided for controlling the relative pivoting movement of two members about a main pivot axis as effected by two hydraulic motors. Each hydraulic motor is a double-acting piston-cylinder type that is fully extended when its respective line of action intersects the main pivot axis. Each hydraulic motor has an end port at each end. Two spaced-apart intermediate ports are provided within the piston stroke length of each motor. Pilot-actuated top dead center-selector valves are provided for reversing the flow to one of the hydraulic motors in response to a pressure differential between an end port and an intermediate port of the other of the hydraulic motors. Decelerator selector valves are provided to normally direct the return flow from the hydraulic motors so as to bypass a hydraulic cushioning circuit.

Abstract: In order to accomplish the separation and further conveyance of the uppert sheet of a stack of sheets by the simplest possible means, an elastic friction finger resting with slight pressure on the uppermost sheet of the stack is provided, which is set into reciprocating motion in a direction (A-B) that is inclined by a certain angle (.alpha.) relative to the surface of the stack, the movement having a low amplitude and a relatively high frequency. The stack itself is inclined backward relative to the horizontal by a certain angle (.beta.). The drive of the friction finger may be effected by means of a bellows connected to a valveless pump, by a pneumatic cylinder, or by a crank drive. It is also possible to connect a pneumatic cylinder, provided with vent bores controlled by the piston, to a supply line that is at constant negative pressure or overpressure.

Abstract: A poppet valve movable to discrete opened positions by metering fluid through axially spaced orifices in a cylinder by a piston directly connected to the poppet. The flow of fluid through the orifice is interrupted to cause the piston to translate to the next adjacent orifice.

Abstract: A system for resiliently supporting a load at a reference height includes a hydraulic cylinder for resiliently supporting a load about a reference height and an accumulator which cooperates with the cylinder for flowing hydraulic fluid therebetween in response to varying loads imposed on the cylinder. A valve is provided for dampening the rate of fluid flowing between the cylinder and the accumulator and a metering valve coacts with the cylinder for adjusting the reference height about which the load is supported.

Abstract: An improved rephasing master cylinder in which the cylinder wall approximate the end of the cylinder has a longitudinal bleed passage in the cylinder wall at one end connected to a lateral passage opening into the forward cylinder chamber while the opposite end of the longitudinal passage connects with the rearward chamber of the cylinder when the cylinder piston is located therebetween. This longitudinal bleed passage permits the restricted flow past the master cylinder piston when the piston is nearing and at the end of its stroke, thereby causing both master and slave pistons to complete their respective strokes.

Abstract: In a diaphragm type pump, a minute amount of the operating fluid is supplied instantaneously from an oil reservoir to an operating chamber at the final stage of the suction stroke in a main cylinder, and an excessive amount of the operating fluid and/or bubbles are discharged into the oil reservoir in the delivery stroke in the main cylinder. The minute amount of the operating fluid is within the range of 0.1 to 2% of the whole volume of displacement of diaphragm.

Abstract: A pneumatic valve system for sealing off the flow of a liquid at the intersection of two pipes, one of the pipes being vertically disposed with respect to the other pipe. A sensing probe senses liquid at a pre-established height in the vertically disposed height which signals a control system to activate the pneumatic valve system. An expandable, inflatable bladder is positioned from the vertically disposed pipe into the second pipe and is inflated, thereby sealing off the flow of liquid past the bladder. When normal fluid flow is to return, the bladder is deflated and positioned back into its original position within the vertically disposed pipe.

Abstract: A method for adjustment and/or indication of a liquid or gaseous pressure, and advice for utilization of the method, including the use of a piston member (7, 7'), movably arranged in a surrounding housing (1), said member having two towards each other acting piston areas with different area, said piston areas being made subject to a pressure from the liquid or gaseous medium, a mechanical load also being supplied to the smaller piston area, whereby the piston surfaces only perform a common movement when the media pressure exceeds a predetermined limiting value, which limiting value comprises of resulting force for the force developed by the smaller piston area under influence of supplied media pressure and added mechanical force, said movement, when predetermined limiting value is exceeded, being arranged to influence a flow restricting valve member and/or indicate the pressure of supplied media.

Abstract: A device for tensioning reinforcing strands in concrete structures comprises a cylinder and a cooperating piston and is provided with means for supplying a pressure gas obtained by the combustion of powder or some similar compound. The device may be arranged so either the piston or the cylinder is movable, and by selecting the size and the composition of the powder charge it will be possible to use the device for an initial tensioning, usually performed in a number of steps, as well as for a final jerk. The device may be provided with an accumulator, at which the combustion occurs, the device being provided with means for permitting, at will, the gas from the accumulator to act upon the piston.

Abstract: Disclosed is a liquid inertia tool in which the kinetic energy of flowing liquid is converted to useful work by decelerating the liquid flow and directing the inertia force in the water against a movable element in the liquid flow-containing structure which in turn moves against a work piece. Flow deceleration is achieved by an orifice-effect valve. The valve is reset for flow resumption or acceleration by automatically or selectively applying hydraulic pressure to a reset mechanism. Use of the inertia tool in pile driving and punch press applications is disclosed.

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 servo cylinder having a piston of the kind having spaced sections which move into an enlarged diameter low pressure bore portion of the cylinder is provided with a gasket assembly for each piston section in the form of an elastic sealing gasket having a resiliently flexible radial flange extending from an integral collar and supported by a rigid ring having a certain circumferential clearance from the collar to permit radial movement for misalignment compensation. The gasket may be formed in the cross-sectional shape of an L or of a T. Where an L-shape is used, a single support ring is provided and where a T-shape is used a support ring on each side of the radially extending flange which forms the leg of the T oriented 90.degree. would be used. The ring or rings are protective of the radial flange in either direction of movement of the respective piston.

Abstract: An internal combustion engine, a fluid motor or a pump includes a cylinder block enclosing an elongated cylindrical bore. A double headed piston is slidably mounted within the bore. The piston and cylinder block are rotatable relative to each other about the longitudinal axis of the bore. Rotation is imparted by a sinusoidal cam and a cam follower. Reciprocation of the piston within the bore is accomplished along with corresponding rotational movement of the cylinder block. Opposed ends of the cylinder block include openings which are aligned with and periodically communicate with exhaust and intake chambers. Porting collars are slidably mounted to the cylinder block and are stationary relative to the cylinder.

Abstract: A pneumatic driving system for causing a nail or the like to run out of the barrel of a nailing tool to where its point may be seen by the user for lining up with a hole on the work and subsequently driving the nail into the workpiece.

Abstract: A warning system for pneumatic fastener driving tools that acceptable bumper deterioration has been exceeded thereby to warn against further use of a tool prior to replacement of the bumper. A piston carrying a driver blade moves from an upper position of rest to lower fastener driven positions. The piston sealingly engages the cylinder wall via a sealing ring. As the bumper deteriorates, the piston moves to lower and lower fastener driven positions. When the piston reaches a predetermined lower position, the effectiveness of the sealing ring is impaired, as by engagement with a notch or edge which tends to destroy or dislodge the sealing ring. This allows high pressure air to escape past the sealing ring to signal that the bumper should be replaced, as by seriously reducing the effectiveness or operability of the tool or as by producing an audible signal by the escaping high pressure air, or both.

Abstract: A vapor engine including a cylinder in which a piston reciprocates and having an inlet valve in the cylinder head which is driven from its seat by the piston as it approaches the cylinder head. The time at which the valve is driven from its seat does not change relative to the top dead center position of the piston. The travel of the valve body is ballistic and the valve remains open for a time determined by a combination of the piston velocity at the initial contact, the distance the valve travels before hitting a stop from which it rebounds elastically toward its seat, the pressure drop across the valve and the mass of the valve. The exhaust valve of the engine may be either internal and actuated by mechanical forces or external, in which case it is actuated by pressure forces. In one embodiment of the invention the stop from which the valve rebounds may be adjustably positioned manually or automatically to control the period of time during which the intake valve is open.

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: A large bore, long stroke, low friction, hydraulic actuator having dual hydrostatic bearings permitting elastic deformation of the piston rod while inhibiting metal to metal contact between either the piston head or the deformed piston rod and the walls of the hydraulic cylinder. The actuator employs a safe and highly reliable metering orifice cushion decelerating means. Piston displacement is constantly monitored by a completely internal, magnetostrictive, sonic delay line displacement measuring means.

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 hydraulic pile driver of the kind having at least one hydraulic cylinder for raising a tup. An arrangement is proposed for allowing the use of oil as the hydraulic fluid. The cylinder has a closed chamber around it, to which oil under pressure is supplied. An apertured cuff around or within the cylinder is moved to bring its apertures periodically into and out of registry with apertures in the cylinder wall to connect the cylinder space alternately with said chamber for supply of fluid to the cylinder and to a discharge line for the discharge of fluid from the cylinder. The volume of the chamber is considerably greater than the volume of the cylinder space. The apertures in the cuff and the cylinder wall that register for discharge of the oil from the cylinder have a total cross-sectional area at least equal to that of the cylinder space to make for fast discharge of the oil, thereby ensuring free fall of the tup.

Abstract: A hydraulic jack is disclosed, of the type comprising a ram having a head portion reciprocable in a cylinder between two cylinder ends, and sealing means carried on the ram head portion to provide a substantially fluid-tight seal between the ram and the cylinder interior surface. In this jack, an open sided pressure relief trough is formed in the interior surface of the cylinder adjacent one end to permit the flow of fluid past the sealing means when the head portion is located substantially adjacent the cylinder end and relief trough. Fluid bleeding action past the relief trough thus prevents forcing the ram head and sealing means against the cylinder end. When the jack is so constructed, the sealing means can include an elastomeric seal cup member which will not be damaged by its travel past the trough.

Abstract: An expanding chamber hydraulic motor venting through a working member reduces the motor/stroke-limiting venting valve assembly to three simple components: a cup-shaped cylinder, an annular gasket at the open end of the cylinder, and undersize piston sufficiently loose in the cylinder to provide free-flow of hydraulic fluid therebetween but protruding through the gasket in a sealing fit; in operation, fluid pressure introduced by conventional means between the piston and cylinder can force the piston to extend from the cylinder only within a maximum stroke length limited by an annular groove around the piston which when it reaches the gasket vents the pressure past the gasket.

Abstract: The lower draft link of a tractor three-point hitch includes a sensor to sense draft loads imposed on the draft link by an earth-working implement. Variations in the draft load cause variations in the pressure of the fluid in the sensor from a preselected pressure. A pilot-operated, load control valve is connected to the sensor and is shiftable in response to pressure above and below the preselected pressure to actuate a control mechanism. The control mechanism actuates a direction control valve for directing fluid to and from a hydraulic lift cylinder for respectively raising and lowering the draft link to adjust the implement so as to maintain the preselected pressure and thus maintain the desired draft load.