Abstract: An electrohydraulic servo valve employing a linear force motor having a floating coil and armature driven by a high frequency excitation signal modulated to change its average DC component. A servo loop controller modulates the excitation signal in response to feedback signals from the servo valve or a hydraulic actuator controlled by the servo valve.

Abstract: A pneumatic knocking device comprising an elongate housing (1) in which a spring (9) and a top wall (20) with hole (10) are disposed, further comprising a cover (3) with connecting hole (8), a piston (2) movable towards the cover (3) by means of compressed air against the pressure of the spring (9), and a quick-acting vent valve (3, 8, 11, 15) which is disposed in the region of the cover (3) and which vents the chamber (22) beneath the piston (2) into the spring chamber (13) by means of an air conduit (14) is described and is characterized in that the air conduit (14) is in the form of an air passage which is integrated in the housing, that the top wall (20) is in one piece with the housing (1), the cover (3) forms a valve chamber (15) and is provided with a valve bore (21) in which a control diaphragm (11) is movably disposed in such a way that it can bear against the hole (10) in the top wall (20) and close same, and that the chamber (22) beneath the piston (2) is open outwardly.

Abstract: Described is a pneumatic knocking device for knocking dust off bunker walls, comprising a housing (1) which encloses an elongate spring chamber (13) with spring (9), having a vent bore (7), and which is closed at one end by a top wall (20) with hole (10), a valve wall (3) with connecting hole (8), a piston (2) which is movable towards the top wall (20) by means of compressed air against the pressure of the spring (9), and a quick-acting vent valve (3, 8, 10, 11, 14a, 15) which is disposed in the region of the valve wall (3) and which vents the chamber (22) beneath the piston (2) into the spring chamber (13) by means of an air conduit (14).

Abstract: For detecting the pressures occurring at a control valve pressure pickup cells are provided and for processing the pressure measuring signals evaluating electronics are provided which together with the pressure pickup cells is arranged on an intermediate plate associated with the control valve. With this arrangement signals may be formed which monitor and control the mode of operation of the consumer governed by the control valve. By arranging the components necessary for the control circuit on the intermediate plate a standardized design is made possible in which the constructional expenditure is greatly reduced.

Abstract: A hydraulic drive mechanism for a punching or an embossing tool, with a double-acting drive hydrocylinder with differently large piston areas, the rapid feed operation, the working feed operation, as well as the rapid retraction operation being controllable by the joint or alternative pressurization of these piston areas. For effecting switchover, an area switching valve is provided which switches over, once the driving pressure exceeds, for example, 90% of the maximum initial pressure of the pressure supply unit, from differential operation to unilateral pressurization of the larger drive area. The area switching valve comprises a check valve acted upon, in the opening direction, by the operating pressure in the smaller driving pressure chamber. A locking spring force of the check valve is equivalent to an opening pressure of about 90% of the supply pressure.

Abstract: A power steering system includes a bypass valve for bypassing fluid from a main fluid conduit connected between an engine-driven, power steering pump and an actuatable, open-center, steering control valve which is actuated upon turning of a vehicle steering wheel. When the steering control valve is actuated, the demand for fluid through the steering control valve to a power steering motor increases. The fluid pressure in the main conduit varies as a function of the demand for fluid to the steering control valve. The bypass valve is urged toward an open condition by a fluid pressure signal. The bypass valve is urged toward a closed condition by a spring and by a fluid pressure which varies as a function of the demand for fluid to the steering control valve and as a function of an electrical signal which varies as a function of at least one vehicle operating parameter, such as vehicle speed.

Abstract: A 3/2 proportional control valve is provided with an actuating piston which is subjected to the control pressure set in a pilot valve. The area relationships of the actuating piston are so chosen that at the actuating piston a high pressure gradient obtains and the adjustment dynamics of the regulating piston are increased.

Abstract: In a proportional pressure reducing valve including a spool having a first end connected to a solenoid and a second end exposed to a feedback chamber, and formed with a groove for allowing a supply port to communicate with an output port when the spool is driven by the solenoid in proportional to solenoid current under balanced condition of an axial force of the solenoid and feedback pressure, the pressure reducing valve further comprises a valve for allowing the feedback chamber to communicate with a drain port to control the valve into inbalanced condition to momentarily raise output port pressure up to supply pressure, when the hydraulic output pressure within the feedback chamber rises beyond a predetermined relief pressure.

Abstract: A multi-port, self-regulating, proportional control valve preferably uses a load output feedback system to produce working fluid load output pressures that are proportional to pilot control fluid pressures. In some embodiments, the control valve is programmable and capable of different load output pressures selected either prior to, or during, operation. The control valve apparatus according to the present invention is capable of a center-off or neutral condition that requires substantially no pilot control flow when there in no control valve output flow.

Abstract: In a solenoid-operated pressure control valve having a pressure modulating section and a magnetic section, the pressure modulating section includes a valve sleeve having an application port, an output port, a feedback port having throttle passage, and a drain port, and a spool being movable in the valve sleeve; and the magnetic section includes a coil assembly and a rod. According to the above structure a force developed from the magnetic section, a force developed by a spring and an output pressure feedback force are applied and balanced, so that an application pressure is so modulated that the application pressure is taken out as an output pressure corresponding to input electric level to the magnetic section.

Abstract: A piloted rotary two-way "on-off" valve which will couple hydraulic fluid from the valve input to the valve output in the "on" position and then move to the "off" position where it will maintain the pressure on the down stream side while enabling the pressure on the upstream side to be removed.

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

Abstract: A pressure reducing valve assembly comprising a main valve (11) and a pilot valve (22), wherein a cylindrical chamber (12) of the main valve (11), which has annular grooves (17, 16, 15) provided with an inlet port (A), an outlet port (B), and a return port (T), respectively, accommodates therein a slidable spool (13) so that a pilot chamber (18) opening into the outlet port (B) is formed at one end of the spool (13) and at the other end thereof is formed a control chamber (25). The inlet port (A) of the main valve (11) being connected with that (a) of the pilot valve by way of a passage (51) while the control chamber of the main valve is connected with the outlet port (b) of the pilot valve by way of a passage (52), whereby the fluid pressure at the outlet port of the main valve can be set high with a small operating force of an electromagnetic unit (48) of the pilot valve (22).

Abstract: An electromagnetically operated mechanism produces an unstable first controlled pressure which, under a given condition, is saturated quickly to a degree slightly lower than a target value determined in accordance with an information signal issued from a brake pedal force detecting device. A servo-motor type actuator produces a stable second controlled pressure which, under a given condition, is saturated slowly to the target value. A control mechanism applies only the first controlled pressure to a work chamber of a pneumatic brake booster when the first controlled pressure is higher than the second controlled pressure, and applies only the second controlled pressure to the work chamber after the second controlled pressure becomes higher than the first controlled pressure.

Abstract: A method and device for adjusting pressure fluid cylinders, the fluid being a compressible gas such as air and the cylinder being double-acting and receiving a piston (2). A force transmitting means (12, 20, 24) sensing the load of a cylinder generates a signal corresponding to the size of the load which signal is led to a pressure regulating means (17) adjusting the pressure in the cylinder (1) in dependence of the signal so that this will balance a force acting on the piston rod (3). The load-carrying piston (2) is then positioned in a stationary position relative to the cylinder (1).

Abstract: A power steering system includes a bypass valve assembly which bypasses fluid from a main conduit connected with a power steering pump and motor. The bypass valve assembly is urged toward an open condition, bypassing fluid from the main conduit, with a force which varies as a function of the fluid pressure drop across an orifice in the main conduit. The bypass valve assembly is urged toward a closed condition by a spring. In addition a pressure responsive pilot valve assembly opens to communicate the fluid pressure in the main conduit to the bypass valve to urge the bypass valve assembly toward the closed condition. This decreases the rate at which fluid from the power steering pump is bypassed to thereby increase the amount of fluid available for actuation of the power steering motor.

Abstract: A pressure controller for an air spring having a gas-filled, variable interior space for spring action between relatively-vibrating bodies has interconnected intake and outlet valve stems for opposite valve action and an actuating piston responsive to the gas pressure in the variable interior space and an oppositely-acting compression spring for moving the valve stems. High pressure in the variable interior space opens the outlet valve to vent the variable interior space to the atmosphere and low pressure in the variable interior space opens the inlet valve to supply compressed gas to the variable interior space from a reservoir.

Abstract: A control system for controlling the movement of the slide of a hydraulic press of the type having a main cylinder containing a piston mounting the slide. The control system comprises an electronic processor, a pressure transducer to measure the pressure of hydraulic fluid applied to the piston to move the slide downwardly, a position encoder coupled to the slide to determine the vertical position of the slide, and a hydraulic circuit to supply hydraulic fluid under pressure to the cylinder to move the piston and slide upwardly and downwardly. The hydraulic circuit comprises a plurality of cartridge valves having controls actuable by outputs from the processor.

Abstract: A tool, in particular a lapping wheel, is to be positioned by a hydraulic drive cylinder and subsequently pressed against a workpiece. For this purpose a position control and a pressure or force control is provided. The weight change of the lapping disk subjected to wear is automatically detected by measuring the pressure value which is necessary to keep the weight in a state of suspension without support. The pressure value is stored and in the subsequent pressure regulating operation fed as compensating parameter to the pressure control circuit.

Abstract: A fluid cylinder control method for monitoring the position or controlling the movements of a piston which is slidably guided in a cylinder tube and is acted upon on at least one side by a pressure medium, in particular, maintaining the piston in a predetermined position against the action of eventual disturbance forces. This is attained in that the force which is transmitted between the piston and the cylinder by way of the parts which are slidingly guided on each other, and in particular the friction force acting by way of the seal gaskets of the piston and/or of the rod, is measured and the loading of the piston by a pressure medium is varied in the sense of reducing the measured force.

Abstract: A control system for operating positive displacement hydraulic motors to minimize pressure peaks and stresses associated therewith upon starting the motor at full fluid flow includes a self-closing pilot operated valve which, upon initiation of fluid flow to the motor bypasses a majority of the flow to a return line circuit and progressively closes to force pressure fluid to accelerate the motor to a preselected operating speed. The self-closing valve includes a spool type closure member which is pilot actuated through a timing orifice to commence closing upon initiation of fluid flow therethrough from the pump discharge or supply line. The closure member is spring biased in the open position and automatically resets itself to the open position upon shutdown of the motor operating valve.

Abstract: A piston for a striker is displaceable in a cylinder and forms compartments on opposite sides which can selectively be connected by hydraulically controlled valve elements to a pump and to an accumulator. A hydraulic controller for the valve elements initially connects a compartment on one side of the piston to contribute the pressure from a respective compartment to the accumulator during a lifting operation, cuts off the valve element affording this pressure accumulation to brake the piston, and other such valve elements enable the accumulator to be charged with the piston in its raised position so that, upon triggering by the controller of the valve elements, the pressure which drives the ram is equal to the total pressure delivered by the accumulator and the pump to the piston.

Abstract: An axial bore which extends through the spool and receives a control rod. Channels formed in the control rod cooperate with radial passageways in the valve spool. A pair of torsion rods extend axially from the control rod. One is coupled to a stepping or torque motor, the other is coupled to a rotatable drive member. An assembly for converting axial motion to rotary motion couples the valve spool to the drive member. In the preferred embodiment, this assembly takes the form of a rotatable threaded member secured to the end of the torsion rod and receiving a complementarily threaded end portion of the valve spool. One alternate embodiment comprises a pair of threaded rods extending from the spool, which drives a centrally disposed gear through a pair of complementarily threaded pinion gears. In another alternate embodiment a pressure control valve is achieved. Output fluid from the spool valve is applied to opposite sides of a threaded piston, which is spring biased by opposed compression springs.

Abstract: A hydrostatic drive with a pump is provided having a delivery line coming from the latter, to which at least one consumer is connected through a branch line, and an adjustable restrictor in the branch line, where the adjusting element of the restrictor is loaded on one side by an arbitrarily regulatable pressure, the improvement comprising means whereby the adjusting element of the restrictor is loaded on the other side by the pressure in the branch line between the restrictor and the consumer.

Abstract: A pressure regulating spool valve 10 having a body 25 within which a spool 20 is moved in a dither motion by a proportional solenoid 15 has a spool land 40 separating high and low pressure fluids and spanning and cooperating with a regulated port recess 51 in body 25 for variably opening high and low pressure windows 54 and 55. With opposite edges 52 and 53 of recess 51 spaced apart by a distance X, the opposite edges 42 and 43 of spool land 40 spaced apart by a distance Y, and the dither motion imposed on spool 20 by solenoid 15 having an axial excursion A, the relationship X.ltoreq.Y.ltoreq.(X+A) applies. This makes the alternating overlap of spool land 40 with recess edges 52 and 53 equal to or less than the dither excursion so that high and low pressure windows 54 and 55 of the regulated port 50 are opened for a predetermined portion of each half cycle of the dither motion.

Abstract: Pressure fluid operated servo system method and apparatus including a servo valve operable by an input signal to effect a system output movement; and which servo valve is responsive to the time rate of input signal receipt to vary a gain ratio of system output magnitude compared to input signal value; and method of making such a servo valve.

Abstract: A proportional solenoid operated pressure regulating valve is disclosed. First and second metering spools are respectively mounted for movement inside first and second control spools. Each metering spool responds to a fluid pressure being controlled at a respective operating port.

Abstract: An electro/pneumatic proportional valve having a housing defining an upper and lower chamber separated by an annular web. An inlet port and exhaust port concentric with the annular web are provided in said lower chamber while an outlet port is provided in the upper chamber. An exhaust cylinder is resiliently disposed through the exhaust port and has a radial flange engaging said annular web to occlude the annular web's central opening. The exhaust cylinder also has an axial bore passing therethrough and exiting through the exhaust port. A piston disposed in the upper chamber has a pintle which is operative to engage the exhaust cylinder with the displacement of the piston and occlude the exhaust cylinder's axial bore. Pilot valves are provided to pressurize the upper chamber in response to a pulse train signal displacing the piston towards the web. The displacement of the piston causes the pintle to engage the exhaust cylinder and unseat it from the annular web.

Abstract: A speed limiting hydraulic slide valve. The slide valve is provided with control pressure chambers at each end thereof. The slide is provided with a longitudinal passage at each end and this passage opens into the adjacent control pressure chamber. Each passage is normally closed by a check valve. Each longitudinal passage communicates with a peripheral passage on the valve of the slide by means of a radial passage. If the hydraulic actuator, such as a cylinder, begins to move too rapidly, the pressure in the radial passage will drop, and the pressure in the appropriate control pressure chamber will thereupon overcome the check valve in the passage which opens into such chamber, and this will cause the valve slide to move in a direction which will decelerate the action of the cylinder.

Abstract: A pressure controller for an air spring having a gas-filled, variable interior space for spring action between relatively-vibrating bodies has intake and outlet valve stems for opposite valve action and an first actuating piston responsive to the gas pressure in the variable interior space for moving at least one of the valve stems. High pressure in the variable interior space opens the outlet valve to vent the variable interior space to the atmosphere and low pressure in the variable interior space opens the inlet valve to supply compressed gas to the variable interior space from a reservoir.

Abstract: Electrohydraulic regulating device, particularly for aircraft controls, iuding a regulating cylinder having a regulating piston therein capable of being loaded at either end thereof for the positioning of which necessary volumes of operating fluid can be supplied separately to either end space of the cylinder by means of magnetically-operable valves; a computer by which switch pulses of variable duration to be fed to the magnetically-operable valves are determined in dependence on the specified adjustment distance of the regulating piston; restrictors which determine the throughput of operating fluid through the magnetically-operable valves and sensors which after the switching of a respective magnetically-operable valve generate electrical signals which are fed back to the computer purely as a confirmation of operation. The restrictors are so arranged in an operating fluid circuit that, on movement of the piston, operating fluid flows through only one of the restrictors.

Abstract: The hydraulic circuit of the present invention allows flotation of the header without extensive use of accumulators and is readily adaptable to present open center hydraulic systems. The present invention is also adaptable to closed center hydraulic systems with or without flow compensation. The hydraulic system has a pump selectively connected with the header cylinder. Pressure within the header cylinders is automatically maintained at a constant level by fluid addition to the cylinder or by extracting fluid from the cylinders.

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

Abstract: A pilot operated relief valve has a main relief valve (10) and a pilot relief valve (31) connected between a control chamber (23) and drain. A restriction (16) connects the control chamber (23) to the inlet chamber (22) which is separated from the control chamber by a piston (24) integral with the main relief valve closure member (12). Thus opening of the pilot relief valve against the adjustable force of a spring (14) determines the maximum pressure in the inlet chamber (22). The control chamber (23) can also be connected to drain (70) by a pilot valve (19) which is operated by a force motor (52) against pressure in a feedback chamber (56) connected to the inlet passage (22). The energization of the force motor (52) can be adjusted to adjust the relief pressure to a value below that at which the pilot relief valve (31) opens. Alternatively the pressure in the feedback chamber (56) can depend on the pressure at at least one side of a load fed via a directional valve from the inlet passage (22).

Abstract: An electrohydraulic control system comprising a spool valve including a body having a bore. A spool is positioned in the bore for reciprocating movement within the bore. The valve body has an inlet, an outlet and an exhaust port. An electrohydraulic three-way normally closed pulse width modulated valve has an inlet communicating with the inlet to the valve body and an outlet communicating with one end of the spool. An electrohydraulic three-way normally closed ON/OFF valve has an inlet communicating with the outlet of the body and an outlet communicating with the other end of the spool. A spring yieldingly urges the spool toward the pulse width modulated valve. The spool is positioned so that it normally obstructs a path from the inlet to the outlet.

Abstract: A hydraulic system for operating a pressurizable load off a pressure source having a high-pressure side and a low-pressure side has a main valve having a load side connected to the load and a source side connected to both sides of the source and displaceable between one position permitting flow from the source to the load and another position for opposite flow. Respective fluid-operated actuators displace the valve into its positions. A controller has an input side connected to the high-pressure sides of the source at the source side of the valve and an output side connected to the load at the load-side of the valve and with the sump at the source side of the valve. This controller also is connected to the actuators for pressurizing same alternately and thereby moving the valve between its positions.

Abstract: A hydraulic system in which a pilot operated hydraulic four-way main valve (11) controls the direction and rate of fluid flow to a hydraulic load (13), includes a flow sensor (15) which is capable of operating bidirectionally and may therefore be located in one of the service lines (25, 26) from the main valve (11) to the load (13). The main components of the flow sensor are a variable or fixed aperture flow sensing orifice (52, 53), and a pressure transducer (18) to which the pressure differential developed across the orifice is applied and which converts the pressure differential into an electric negative feedback signal. This electric feedback signal is compared in an electronic circuit (17) with a demand signal, and a corresponding command signal sets the pilot valve (12) which controls the main valve (11).

Abstract: The invention refers to a pressure reducing valve including a pilot valve. The main piston of the pressure reducing valve allows to selectively connect a load port to either a port connected to a pressure source or to a port connected to the reservoir. The pilot valve is connected to a control pressure line and to the reservoir. The main piston controlled connection to the reservoir opens within the valve housing into a port connecting the pilot valve to the reservoir. This provides for a substantially simplified construction of the valve since there are only two operating ports and a reservoir port. Furthermore, the main piston is engaged by a spring which is capable of becoming activated such that dynamic stresses resulting from a change from high to low pressure values are avoided which vibrations are detrimental in generating pressure peaks as well as pressure breaks.

Abstract: A control valve assembly is disclosed for control of a fluid pressure between a variable fluid pressure source and a fluid operable device. This assembly provides a valve means to open or close flow from the fluid pressure source in response to a change in a significantly lower fluid pressure in a pilot chamber, which fluid pressure is controlled by a proportional solenoid operator requiring small current flow. This small current flow to the solenoid operator is due to the low pressure in the pilot chamber, which when relieved or increased effects a change in the valve meaans to open or close fluid flow to or from the fluid pressure source.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, and pilot operated meter-out valve associated with at least one opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve means is sensed and caused to produce a force opposing the movement of the meter-in valve means by the pilot pressure and also applied to a device for controlling an overhauling load resulting in a smooth and accurate control of the movement of the actuator.

Abstract: An equalizer is arranged to continuously sense the control pressures of two valves. In the event of a differential between the control pressures, the equalizer operates to selectively adjust one valve so that the control pressures of both valves will thereafter be substantially equal.

Abstract: The present invention is directed to a two stage hydraulic servo amplifier wherein the boost stage valve comprises two separate valve members, each individually controlling one of a pair of controlled outputs and wherein the position of each valve member is modulated by inputs from a pilot stage acting against separate biasing forces for each valve member.

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

Abstract: The invention relates to a pneumatically driven control valve for the reversible operation of a pneumatic unit. In an addition to an air distribution system for regulating the speed of the pneumatic unit, the control valve incorporates an air volume control system which is fully integrated into the air distribution system. The key component is a rotary slide valve, the rotation of which distributes the compressed air while its axial displacement throttles the air stream flowing through the valve, the degree of throttling depending upon the pressure level of the compressed air delivered to the pneumatic unit. In this way, the control valve is kept simple in construction with very few moving parts and high functional accuracy.

Abstract: A pressure reducing valve comprises a valve housing having an axial bore coupled to a fluid operated load device, and first and second transversely extending control bores coupled to a supply tank and a fluid pressure source, respectively. A control slide is axially shiftable in the axial bore and has first and second pistons controlling fluid flow through the control bores. The fluid pressure supplied to the load device acts on a first end of the control slide. A proportional electromagnet has a plunger which contacts and applies force to the opposite end of the control slide. A first restrictor provides fluid communication between the control slide ends, while a second restrictor provides fluid communication between the control slide opposite end and the supply tank.

Abstract: A pressure control valve construction comprising a valve body having an inlet port adapted for connection to a pressure source, a pair of working ports adapted for connection to respective loads, and a pair of outlet ports connected to a reservoir. A control spool is movably mounted in a bore in the body and includes lands for respectively controlling communication between the inlet port and respective ones of the working ports and between the working ports and the outlet ports. The control spool has opposite ends with blind bores respectively provided therein, and sensing spools are respectively mounted for sliding movement in the blind bores to define spaces between the bottoms of the blind bores and the sensing spools. The spaces communicate with the working port via respective openings in the control spool. In the case of a double acting valve, an actuator is provided at each end for acting on a respective sensing spool whereas for a single acting control valve only one actuator is provided.

Abstract: An electro-pneumatic door control apparatus for use on public vehicles and including reversing mechanism for changing the direction of door movement, either automatically or operator-initiated, in the event of an obstruction in the door. The control apparatus further includes a flip-flop for recording the position (either open or closed) of the door at all times, a monitoring logic device for recognizing the position of the flip-flop and what type of monitoring function is permitted, a control logic device for picking up the door command and the signal from the monitoring logic device combing them and transmitting them to a valve solenoid control device for energizing respective solenoids of several valve devices by which the appropriate movement of the doors is effected.

Abstract: In an apparatus for forming leak-proof joints between tubes and a tube sheet by the internal application of hydraulic swaging pressure, the flow of relatively low pressure fluid from a pressure source to an intensifier is permitted or interrupted by a control valve. During a prefill period, a prefill valve causes the low pressure fluid to bypass the low pressure input side of the intensifier and flow directly to the high pressure side and then to a mandrel. Thereafter, the low pressure fluid is caused to enter the low pressure side of the intensifier to increase the pressure in the mandrel during a swaging period. A pressurization sensor, which is connected to the input and output sides of the prefill valve, contains a piston which is movable in response to the difference in the pressures at these two points to produce a termination signal which, after a delay, actuates the control signal at the end of the swaging period.

Abstract: A hydraulic control device for the pressurization of a clutch or the like for a transmission operable under load comprises a spool-type valve displaceable in one direction to pressurize the clutch and in the opposite direction to vent the same. The valve spool operates with a damping piston which receives the clutch pressure buildup and acts against a control piston which, in turn, is displaced by an operative valve. According to the invention, the pressure head is maintained substantially constant by providing a sleeve or bushing within the damping piston chamber which bears against the spool by a spring and which can be biased by a spring between the damping piston and the sleeve.

Abstract: An improved hydraulic control valve is disclosed for providing the metering of fluid to a steering arrangement such as that normally employed on a motorized vehicle. The steering arrangement includes a piston-cylinder assembly, a main pump for supplying pressurized fluid from a fluid reservoir to the control valve and a control pump connected to the control valve which is actuated by a manually operated steering mechanism. The improved control valve includes a housing having an elongated bore formed therein. Movably positioned within the bore is a valve spool which has at least three annular grooves formed thereon separated by a pair of lands. The valve spool also contains a longitudinal bore formed therein which intersects a transverse bore which opens into the centrally positioned annular groove. The valve spool cooperates with the elongated bore to form control pressure chambers at each end thereof.