Abstract: A compressible fluid powered device includes a dose chamber. An inlet supplies pressurized fluid to the dose chamber. An outlet for releases pressurized fluid from the dose chamber. A moveable divider divides the dose chamber into a primary space and a secondary space, movement of the divider expanding one space at the expense of the other. At least one flow pathway from one space to the other, which collectively allow gas to flow in both directions past the divider and pressure to equalize across the divider, the flow pathway being much more limited than the outlet.

Abstract: The drive device includes: a contact including a moving contact and a stationary contact; a rod connected to the moving contact; a piston which is connected to the rod and is slidably installed in a cylinder and which opens and closes the contact; a fluid pressure source for pressure-feeding a working fluid; and a control valve for driving the piston. In the drive device, the piston forms a partition between a supply pressure chamber communicated with the fluid pressure source and a small pressure-receiving area chamber which are on the moving contact side of the piston and a cylinder control chamber on the opposite side of the piston, and the control valve controls supplying and discharging the working fluid to and from the cylinder control chamber.

Abstract: The present invention relates to a hydraulic DEVICE having a valve housing (1) with a movable valve body (2) arranged inside the valve housing, a hydraulic cylinder with at least a hydraulic chamber (115), and at least a control mechanism (4) for the control of said movable valve body (2), the valve body (2) is substantially sleeve-shaped and arranged inside an annular space (128) in the valve housing (1), and said valve body (2) is provided with a plurality of apertures (250, 251, 252; 206, 202) to make a flow of hydraulic liquid possible in the radial direction through the valve body (2).

Abstract: A pressure-operated linear actuator in which the working liquid is Electro-Rheological (ER) fluid in which there is a single flow path between an inlet and an outlet of an associated pump in which there are two or more pistons and fluid chambers delineated by these pistons, which fluid chambers are connected in series by stationary ER valves distinct from the pistons such that the pressure as determined by each of the ER valves is applied to one or more of the chamber(s), wherein one or both of the ER valves are divided into two or more sections in order to minimize the length, and maximize the cross-sectional area, of the inactive connecting passages.

Abstract: A hydraulic device for a moving contact piece of a high-voltage power circuit breaker includes a reservoir and a low-pressure tank for hydraulic fluid. A changeover valve has a slide for alternately connecting one of the spaces in the drive-piston/cylinder configuration to the reservoir and to the low-pressure tank. At least one separately controlled and arranged control piston is associated with the slide. A servovalve controls the at least one control piston to drive the slide from a first position to a second position, i.e., from a connected position to a disconnected position of the power circuit breaker.

Abstract: The use of an accumulator attached to a chamber of a cylinder allows for the reduction in pressure spikes in constant force hydraulic control systems. Constant force hydraulic control systems often use a differential pressure valve that may have a reaction time of up to one second. By using the accumulator, pressure spikes which might have occurred in the past can be smoothed out and reduced, thus preventing damage to a workpiece or agricultural product. Additionally, by using two cylinders of different sizes, in which one of the cylinders has a barrel end with the approximately the same area as the rod end of the larger cylinder, coordination of devices attached to the cylinders can be maintained without a mechanical link when the hydraulic control system is in a manual mode.

Abstract: A hydraulic power drive unit (36) including a linear hydraulic piston cylinder unit (64) with a set of longitudinally spaced gear teeth (84) in the form of a rack. A pinion gear (86) is operatively engaged and driven by the rack (84). A differential which may include a carrier (102), planet gears (108, 110) and sun gears (120, 122) may be driven by the pinion gear (86) to selectively transfer drive power to two separate rotary drive outputs (38, 40). A switching valve (160) may be provided which is responsive to a reversal of hydraulic supply pressure. Operation of the switching valve (160) may be limited by mechanical interference between an inhibit dog (181) and a cam surface (196) on the carrier (102). The carrier (102) may also include a separate cam surface (140) positioned for actuation of separate electrical switches (146, 148) in order to monitor position of the drive outputs (38, 40).

Abstract: In a method and a configuration for operating a hydraulic drive, a 3/2-port directional seat valve, which is driven by solenoid coils, controls an application of high-pressure fluid through a working piston of a piston/cylinder system. In order to increase the circuit-breaking capacity of the working piston, a hydraulic booster valve which is driven hydraulically by the 3/2-port directional seat valve is used for clearing a direct path from the piston/cylinder system to the low-pressure reservoir during switching-off.

Abstract: A thrust reverser safety system for a turbofan engine is disclosed which is integrated into the hydraulic control system of the thrust reverser door so as to prevent the hydraulic actuator from permitting the thrust reverser door to be forced into its deployed, thrust reversing position. The hydraulic actuator defines a closing chamber which, when acted upon by pressurized hydraulic fluid, urges the thrust reverser door to its closed, forward thrust position. The safety system according to this invention provides a valve associated with the hydraulic control circuit and the closing chamber which prevents the hydraulic fluid from being forced out of the closing chamber. This positively prevents the thrust reverser door from moving to its deployed, thrust reversing position.

Abstract: A fluid operated booster comprising a first valve for controlling the communication between an accumulator and a hydraulic pressure chamber, and a second valve for controlling the communication between the hydraulic pressure chamber and a reservoir, in which, a brake pedal rod is operated to close the second valve and to open the first valve, so that a hydraulic pressure is applied from the accumulator to the hydraulic pressure chamber to act on a power piston, to cause the power piston to provide an operating force, which is transmitted to a master cylinder piston to provide a boosted hydraulic pressure for a brake system; in which, according to the invention, the first valve is a spool valve which is mounted on the brake pedal rod with a predetermined frictional force in such a manner that the spool valve is movable a predetermined distance, and the first valve is closed when the brake system is not in operation, so that no hydraulic pressure from the accumulator is applied to the sliding portion of the bra

Abstract: A hydraulic actuator system, for use in an aircraft, and in which the servo fluid supply to the system is used to provide for the operation and cooling of the system. The system comprises a hydraulically operated piston mechanism including at least one hydraulically operated piston, a servo vluid input to the system, which is connected in a ring main to a first side of the hydraulically operated piston, a servo fluid output from the system, which is connected in a ring main to a second side of the hydraulically operated piston, a variable restrictor arrangement which provides an interface between the servo fluid input ring main and the servo fluid output ring main, and a restrictor arrangement positioned in the servo fluid output side of the system. The position of the piston of the hydraulic piston and the adjustment thereof, are controlled by the restriction applied on the system by the variable restrictor arrangement.

Abstract: A control system for mechanically adjustable motor drives which have a shiftable speed control for controlling the speed of the drive. The system includes a double acting pneumatic cylinder which is remotely controlled to shift the speed control by varying the air pressure in the double acting cylinder, to increase or to decrease the speed of the motor drive. The air pressure can be varied manually or by automatic control means.

Abstract: A percussion drilling apparatus has a control unit in which a displacement reversing unit is arranged axially adjacent to a piston control unit, with the result that the control edges for the apparatus advance and apparatus return can be arranged in separate control sleeves. This control unit makes it possible to achieve better apparatus characteristics and higher overall efficiency of the apparatus.

Abstract: A hydraulically actuated wheel brake with a built-in control device comprising a brake piston including two pressure surfaces each of which defines a different one of two working chambers. The pressure fluid inlet is connected directly to one of the two working chambers and via a valve to the other of the two working chambers, the valve being actuatable upon attainment of a predetermined value of inlet pressure. The brake piston has a step in its outer periphery whose surface provides one of the two pressure surfaces. The piston is guided exclusively at its outer periphery in a cylindrical bore of a housing. Since only two parts are disposed concentrically in each other, there results ease of manufacture and a minor susceptibility to failure.

Abstract: This invention relates to a fail-safe or auto-return actuator cylinder employing the air spring effect provided by compressed air trapped in an air-spring compartment; which air spring effect replaces the conventional mechanical coil spring employed in conventional fail safe or auto-return air cylinders. The air spring chamber integrally built into the cylinder body is connected to the compressed air supply tube through a check valve that provides the self-charging and self-recharging feature for the air-spring chamber and, consequently, the air-spring chamber remains fully charged with compressed air even when there is a compressed air leak from the air-spring chamber. The air-spring compartment stays charged or becomes automatically recharged even when there is a leak from the air-spring compartment as long as there is compressed air to actuate the cylinder.

Abstract: The hydraulic actuator (35) utilizes the centrifugal head developed in its pressure chambers (52,54) when the housing (44) rotates as a source of pressure. As actuator (35) rotates fluid exits outlet port (56) and passs through a servovalve (64) into chamber (54) to move vane (49) relative to the actuator (35). To move vane (49) in the other direction, fluid exits outlet port (58) and passes through the valve into chamber (52). This self-powered actuator has utility in systems requiring relative angular positioning between a pair of rotating elements such as a pair of voltage regulator rotors in a dual permanent magnet generator.

Abstract: Conventional piston-cylinder hydraulic actuators require external pressure sources. The hydraulic actuator disclosed utilizes the centrifugal head developed in its chambers. The piston (36) is attached to shaft extension (24) which is splined to the actuator cylinder (20). The cylinder (20) rotates with the shaft (16) to develop a centrifugal fluid head which is selectively directed from the outlet port (40a, 40b) of a contracting chamber through a servo valve (46) to the return passageway (46b, 46a) of an expanding chamber to axially displace piston (36) and shaft (16). An accumulator in the fluid circuit retains fluid displaced from the cylinder (20).

Abstract: A liquid pressure booster as may be used in a brake booster or clutch booster produces an oil pressure of a level which corresponds to the magnitude of an input applied to an input shaft. The oil pressure acts upon a power piston, which then produces an amplified output in response to a small input. The oil pressure is also returned to act upon the input shaft so as to provide a reaction to the input. The invention provides a step in at least one of the input shaft and the power piston so that the combination of the step and the housing defines a pressure chamber having a pressure responsive surface at the step. A flow path switching valve selectively establishes a communication of the pressure chamber with either the power chamber or a reservoir. When the switching valve is operated, the pressure responsive area of the input shaft which is acted upon by the oil pressure can be changed, thereby changing the magnitude of the reaction transmitted to a driver.

Abstract: The pressure-medium-actuated valve has a pressure medium inlet, a pressure medium outlet and a cylinder. A piston which is connected to a lid is movable in the cylinder and subdivides the cylinder into a first piston chamber and a second piston chamber. Two relief lines, each comprising a control valve are connected to the piston chambers and extend to a pressure medium sink. A first connecting line comprising a control valve extends from the inlet to the first piston chamber and a second connecting line comprising a control valve extends from the inlet to the second piston chamber. A third connecting line is disposed in the wall of the valve body and extends at one end into the first connecting line. The other end of the third connecting line is connected to the cylinder at a place which, with the piston in the operative position, extends into the second piston chamber and, with the piston in the safety position, extends into the first piston chamber.

Abstract: A brake system for an off-highway vehicle which includes a fluid pressure actuated multi-disc brake and a fluid pressure control system. Engagement of the multi-disc brake is effected by a fluid operated piston having multiple effective pressure areas. Fluid pressure applied to a certain of the effective pressure areas urges the piston in a brake applying direction; fluid pressure applied to the other of the pressure areas urges the piston in a brake releasing direction. The fluid pressure control system controls the communication of pressurized fluid to the effective pressure areas to provide both the brake applying and brake releasing functions. Redundant fluid pressure circuits supply pressurized fluid to the brake applying effective pressure areas. In the event of failure, the control system is operative to interrupt fluid flow to the failed circuit.

Abstract: A combined brake cylinder/air reservoir device in which a relatively small, tubular-shaped piston in a positioning chamber is connected to a larger power piston having an application chamber on one side and a release chamber on the other side in which air is stored in place of separate reservoirs. A replaceable cylinder liner is provided to receive different-sized power pistons. During a brake application, the power piston enters the cylinder liner and is displaced from the liner during brake release to provide free air flow between the application and release chambers and thereby facilitate piston return movement by means of a return spring. A dynamic pressure seal between the application chamber and positioning chamber engages the outer periphery of the tubular-shaped small piston, while a smaller diameter dynamic pressure seal between the release chamber and atmosphere engages the inner periphery of the tubular-shaped small piston.

Abstract: The pressure medium actuated valve has a pressure medium inlet port, an outlet port and a cylinder in which a piston connected to a closure member can slide. The piston sub-divides the cylinder into a first cylinder space and a second cylinder space. Two relief conduits, each containing a control valve are connected to the cylinder spaces and extend to a pressure medium sink. A first connecting conduit containing a control valve extends from the inlet port to the first cylinder space and a second connecting conduit containing a control valve extends from the inlet port to the second cylinder space. The second connecting conduit has a non-return valve through which pressure medium flows in the direction of the second cylinder space, a third connecting conduit being provided between the first and second connecting conduits.

Abstract: An improved power steering control apparatus includes a power steering motor having a piston rod which extends through one end of the motor cylinder. This results in the rod end of the piston having a smaller working area than the head end of the piston. In order to equalize the fluid pressure forces on opposite sides of the piston when the motor is in an inactive condition, a power steering control valve vents both sides of the piston to atmospheric pressure when the control valve is in a neutral or unactuated condition.

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 cyclic or periodic event timing system for use in conjunction with a pressure fluid control circuit includes a cylinder and piston type actuator comprising a differential area piston which is exposed to fluid pressure from a flow conduit on opposite sides of a flow restricting orifice in the conduit or a branch portion thereof. The actuator piston includes a rod portion which is extended in one direction in response to an unbalanced pressure force on the piston. On the extension stroke, the actuator opens a valve to effect flow in the conduit resulting in a reduction in pressure which is sensed in the cylinder chamber exposed to the larger piston fluid area. The actuator piston then returns to an initial retracted position in response to an unbalanced pressure force.

Abstract: An energy conserving air motor with rotary actuation includes a pair of cooperating different diameter pistons coaxially arranged and connected rigidly to one another by a central connecting member provided with spur gear section adaptable of receiving a meshing pinion assembled inside an elongated housing provided with a diffential diameter bore passing therethrough and adaptable of receiving inside a larger diameter section which is blind a larger piston while smaller diameter section which is provided with fluid supply and exhaust port means receives smaller diameter piston while said pinion entering said housing perpendicularly substantially central to the housing ends so as to rotate therein when pistons move linearly inside bore between a first normally atmospheric and a second energized positions in response to the working fluid pressure supplied via fluid supply and exhaust port means by way of a 3-way solenoid or pilot operated directional valve so as to allow energization of the small diameter pisto

Abstract: In an hydraulic power booster a boost piston working in a bore in a housing is of stepped outline having at least three axially spaced portions of at least two different diameters. The two end portions carry seals having slidable sealing engagements with complementary portions of the bore, and a stationary seal is fixed in the housing. An intermediate portion of the piston disposed between the end portions and of smallest diameter has a slidable engagement in the stationary seal.

Abstract: A fluid actuated positioner for producing a mechanical output signal proportional to a fluid input signal. Input signal acts on input rod of input cylinder to control a main valve which controls flow between chambers of a hydraulic power cylinder. Power cylinder has output piston rod connected to device to be controlled, and fluid forces on output rod are determined by pressure differences across faces of output piston, which differences are determined by amount of metering of main valve. Valve can be simple clearance passage maintained open to permit steady flow therethrough in non-changing signal, or can be spool valve which stops flow during non-changing. Both devices do not require exceptionally close tolerance manufacture, and creep problems are reduced.

Abstract: A multiple mode hydraulic piston assembly employing a regenerative hydraulic circuit which when incorporated in the piston of a hydraulic cylinder and assembled with a pressureized hydraulic source through appropriate piping and valving, will sequentially permit, restrict, and block liquid flow through the piston and will thus extend its piston rod in multiple force modes, namely a low force rapid extension mode, a moderate force rapid extension mode, and a high force extension mode. In response to fluid pressures within the cylinder chamber the multiple mode piston assembly automatically changes operational modes. First bi-directional flow is provided between opposing chambers, then uni-directional flow is provided from the rod end to the back end chamber, and finally flow between the chambers is blocked. A modified embodiment provides a free motion mode wherein a modest external force can displace the piston in either direction.

Abstract: A percussive device for creating impact impulses, which device comprises a housing accommodating a striker. The striker has a tail portion located in a power cylinder which is joined to the housing and is filled with a fluid medium under pressure, said fluid medium operating the striker. Provision is made of an arresting mechanism which is kinematically connected to a drive designed to engage the striker for effecting its backward stroke in the process of which the fluid medium under pressure is compressed, storing potential energy. According to the invention, the striker backward stroke drive is constructed in the form of several hydraulic cylinders equidistantly spaced round the periphery of the housing. The rod of each of the hydraulic cylinders is connected to the striker arresting mechanism.

Abstract: A flapper valve having a negative rate characteristic is variably opened by an external force and controls fluid pressure to a piston which moves, in response to this pressure, in order to return the valve to a null position. A positive rate flapper valve applies force to the negative rate flapper valve and balances the fluid pressure in the negative rate flapper valve, thus providing high sensitivity negative flapper valve operation in the null position region and a negative rate in the region to overcome piston friction, without instability.

Abstract: A movable member, including a first piston in a hydraulic cylinder, is biased toward a first position by a reset spring and toward a second position by a trip spring which is compressed between the first piston and a second piston in the same cylinder. The second piston is disposed for limited floating movement relative to said movable member. Hydraulic fluid under pressure is admitted into a first chamber between the first piston and the adjacent end of the cylinder, and a constricted fluid passage in the movable member enables the hydraulic fluid to flow between the first chamber and a second chamber defined by the second, floating piston and the other end of the cylinder. With equal, relatively high fluid pressure in both chambers, the trip spring is charged and the movable member is held by the reset spring in its first position.

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

Abstract: Liquid fluid pressure applied to a piston causes advancement thereof at a rapid rate until an external resisting load applied to the piston rod exceeds a predetermined value producing a corresponding increase in the pressure within the opposing pressure chambers to which the piston is exposed. Bi-directional flow, conducted between the opposing chambers during rapid piston movement, is automatically blocked by a differential circuit pressure operated piston valve to cause a rapid increase in the differential pressures acting on the piston, and an increase in the value of the external piston rod load with a corresponding decrease in its rate of movement in the same direction. A modified embodiment permits the piston rod to act under pressure and with a force in both the extending and retracting phases of the stroke with the same rapid extending rate until the external resisting force is encountered.

Abstract: A vacuum type brake booster device including an input rod with an adjustable stop mechanism for enabling the input rod to have such a normal, full-retracted position as to hold the booster control valve in a neutral position to keep the second working chamber of the booster out of communication with the first working chamber thereof as well as with the atmosphere while holding the booster output rod in direct abutting engagement with the brake master cylinder piston. There is no delay in operation of the brake master cylinder when the brake pedal is depressed.

Abstract: A self-propelled pneumatically operated percussion boring apparatus for boring holes in the ground of the kind which includes a percussion piston which is reciprocated pneumatically in a tubular housing is provided with a control device for causing the apparatus to make either a forward movement or a return movement. The control device comprises a control sleeve which has air ports through its wall and over which a skirt of the piston passes as, in operation, the piston reciprocates. The skirt has ports which come into register with ports in the sleeve and the sleeve is fixed in position in the housing and has a control tube rotatably mounted within it. The control tube has one or more ports through its wall and compressd air for operating the apparatus is supplied through the control tube.

Abstract: At the beginning of a working stroke of a compressed air loaded working piston disposed reciprocally in a pneumatic operated ramming tool said piston is initially set in motion under the action of minor amounts of compressed air until its top becomes immersed into stored compressed air and the working piston is then exposed to the full force of said stored compressed air to perform its working stroke. This working process permits to use a substantially simpler ramming apparatus.

Abstract: A fluid pressure actuated drive for providing for the closing unit of an injection moulding machine a to and fro traversing motion of a movable part of the unit with little force and a clamping of the closed unit with a greater force. The device has at least two double acting piston and cylinder devices which act in parallel and the pistons of which each have at each side a piston rod which passes through a seal in the responsive adjacent cylinder end. The piston rod on one side of at least one piston is thicker than that on its other side and the piston rod on one side, which corresponds to the same working side as one side of the one piston, of the or each other piston is thinner than that on its other side. Traverse in one direction is provided by applying fluid pressure to both sides of the one piston, and in the other direction by providing fluid pressure to both sides of the other piston. Clamping pressure is provided by applying fluid pressure to one side only of each of the pistons.

Abstract: In a high-energy rate forging machine the piston, to which a ram is attached, is driven towards a workpiece by a high pressure gas supplied to the space above the piston within a cylinder. The space above the cylinder and the space below the cylinder are joined by holes in the cylinder and grooves in the cylinder walls. The grooves are only effective when the piston is at about the middle to lower part of its stroke. They are blocked when the piston is at or near the top part of its stroke. High speed stamping is provided without double or triple stamping and with a smooth return stroke of the piston.

Abstract: A column including a cylinder, a piston axially slidable in the cylinder cavity, a piston rod axially projecting from the cylinder, and a valve permitting selective communication between the two compartments of the cylinder cavity separated by the piston for flow of fluid between the compartments is additionally provided with a helical compression spring coiled about the piston rod and impeding axial movement of the piston on the piston rod in one direction, movement in the other direction being limited by a radial abutment flange on the piston rod. The spring favorably affects the comfort of a chair whose seat is mounted on the column.

Abstract: An apparatus for causing a low force input movement from a control rod to cause a corresponding movement in an output member by force amplification through hydraulic pressure. A piston is provided that has a greater pressure area on one side than on its other side. Orifice means are provided between a pressure chamber and a control chamber and between the control chamber and the reservoir such that as said second orifice means is varied, the piston will move until a null position is reached.

Abstract: A carburetor has an operator operable butterfly valve and an auxiliary throttle located upstream of the butterfly valve. The auxiliary throttle is urged toward closure by temperature sensitive thermostatic means and is urged toward opening by the airflow drawn by the engine. A pneumatic element subjected to the pressure downstream of the butterfly valve opens the auxiliary throttle to a predetermined extent immediately after cranking. A pneumatic device responsive to the depression downstream of the butterfly valve urges the auxiliary throttle toward closure when the butterfly valve is abruptly opened while the engine is cold. The action of that pneumatic device is of short duration, and consequently the auxiliary throttle returns to its partially open position as acceleration proceeds.

Abstract: A springless impact device including a piston-cylinder mechanism having at least one preselected coacting port and passageway operatively connected to a valve pressurized fluid control apparatus which selectively feeds and exhausts pressurized fluid to and from the device in a predetermined manner. There is an area differential between the top and bottom ends of the piston head. The device includes an inverted "U"-shaped seal ring on the piston head which functions as a one-way check valve to effect piston reciprocation in coaction with the area differential on the piston head.

Abstract: In a control system of the type having a hydraulic cylinder, a piston slidable in the cylinder and dividing the interior thereof into a first and a second pressure chamber, a pressure fluid reservoir, a pump, conduits having a valve interposed therein which is electronically controlled and connects the second chamber with the reservoir or pump, respectively, or block the second chamber, and an auxiliary device for operating the system in the event the electronic control for the valve malfunctions, the invention provides a movable member extending into the second chamber; subdividing means located in the second chamber intermediate the movable member and the piston and subdividing the second chamber into a first and a second compartment, the movable member being operable to shift the subdividing means in the second chamber; and valve means controlling communication between the compartments and of the same with the first chamber, the valve means forming with the piston and with the movable member a follow-up co

Abstract: A mold closing unit for an injection molding machine having a double acting mold closing piston, a closable valve interconnecting both sides of the piston, an auxiliary piston, and a piston rod for each piston, each connecting one side of the pistons to the movable mold part wherein the cylinder spaces on mold closing side of the two pistons are permanently communicated whereby the change in volume of the combined working space is proportional to the areas of the piston rods. The cylinder for the auxiliary piston is placed laterally of the main cylinder so that the overall length of the machine is held to a minimum. An additional return piston is also provided.

Abstract: A steam engine is provided including a piston having an upper end portion movable upwardly and downwardly within an internal cylindrical surface of a cylinder, toward and away from a top wall to define a first variable volume space while moving away from and toward annular means in sealing engagement with a lower reduced diameter portion of the piston to define a second variable volume space. A connecting rod has an upper end pivotally connected to the piston and a lower end pivotally connected to a crankshaft. A valve assembly is provided for flow of high pressure steam to the second space and for flow from the first space to an outlet during upward movement of the piston and for flow of steam from the second space to the first space during downward movement of the piston. Preferably, the piston has a lower end portion sealingly engaged with a second internal cylindrical surface of the cylinder to define a third space which is connected through breather passages to the exhaust outlet.

Abstract: A differential piston is reciprocable in a cylinder and subdivides the latter into a first and a second chamber. The piston has a piston rod which extends through the second chamber outside the cylinder and is adapted to open and close the mold of a molding machine. An admitting conduit admits pressure fluid into the first chamber, and a connecting conduit connects the two chambers and has a valve interposed in it so that the two chambers communicate with one another only while the first chamber is pressurized, not while the second chamber is pressurized in the absence of pressure in the first chamber. A sealing arrangement between the piston and an inner circumferential surface of the cylinder is effective for preventing the flow of pressure fluid from the second to the first chamber when the latter is at a lower pressure than the former.

Abstract: A fluid actuating device for an electric switching apparatus such as a high-voltage power circuit breaker or the like includes an actuator for actuating the switching apparatus. The actuator in turn is made up of a cylinder and an actuator differential piston movable in the cylinder between positions corresponding to the open and closed positions of the switching apparatus. A fluid supply provides fluid under high-pressure to the end-faces of the actuator differential piston. A main-valve arrangement includes a main-valve differential piston movable for alternately interrupting and connecting fluid from the fluid supply to one of the end-faces of the actuator differential piston whereby the actuator differential piston is caused to move between its end positions. The main-valve differential piston also has end-faces fluidly connected to the fluid supply.

Abstract: A fluid servo network having a servo fluid pressure responsive movable output member controlled by a variable area orifice the effective area of which is established by a movable servo valve which is actuated by lever means in response to a variable force input applied thereto. The lever means includes a main input lever responsive to the variable force input and an opposing variable feedback force which varies in response to the reaction of the output member to establish a force balance on the main input lever. The main input lever is attached to a roller loaded by a constant reference force and movable along a secondary lever mounted for pivotal movement about a fixed axis to vary the effective lever arm of the secondary lever which is attached to the servo valve. The input torque tending to close the servo valve is opposed by the torque derived from a characteristic orifice force unbalance acting through the secondary lever.

Abstract: A hydraulic drive for the die closing unit of an injection molding machine in which at least one power cylinder and power piston with a coaxially attached auxiliary cylinder opens and closes the molding die by executing the opening and closing travel with a differential piston action in the power cylinder and/or with the auxiliary cylinder, while valve-closable bypass channels in the power piston are kept open. The closing of these channels switches the drive from an accelerated travel mode to a high-pressure die clamping mode.An annular valve plunger cooperates with a valve seat on the power piston to open and close the bypass channels, several alternatives of guiding and hydraulically moving the valve plunger being contemplated.