Abstract: In a fluid circuit for an air cylinder connected to a switching valve provided with exhaust ports, a head-side pressure chamber is connected to the switching valve by a first pipe, and a rod-side pressure chamber is connected to the switching valve by a second pipe. A first restrictor is disposed at a connection point between the first pipe and the switching valve or in the vicinity of a first output port of the switching valve, and a second restrictor is disposed at a connection point between the second pipe and the switching valve or in the vicinity of a second output port of the switching valve.

Abstract: A pressure booster constituting a cylinder apparatus is provided with a first piston and a second piston that are coupled to each other by a rod. A connection member provided to the second piston is configured so as to be displaceable from a connection position to a blocking position as a result of the connection member making contact with a cylinder body when the second piston is displaced in a direction where a boosting chamber contracts, and so as to be displaceable from the blocking position to the connection position as a result of the connection member making contact with the cylinder body when the second piston is displaced in a direction where the boosting chamber expands.

Abstract: A driving tool includes a striking mechanism configured to be actuated by a combustion pressure of a mixed gas of compressed air and fuel, a combustion chamber in which the mixed gas of compressed air and fuel is to be combusted, a valve member configured to open and close communication between the striking mechanism and the combustion chamber, and a valve support member configured to support the valve member. The valve member has a seal part provided on an outer peripheral surface along a moving direction of the valve member.

Abstract: A driving tool includes a first cylinder that generates compressed air by reciprocating movement of a first piston slidably disposed therein. A longitudinal direction of the first cylinder intersects a longitudinal direction of a second cylinder and extends alongside a magazine that feeds fasteners onto an axis of movement of a driving part of a second piston. The first piston reciprocally slides in a direction that extends alongside the magazine. A tool handle is disposed on the side of the first cylinder that is opposite from the magazine in the direction of the axis of movement.

Abstract: A braking actuator uses a single cylinder without using a spring to achieve a 3-position operation. A partition plate and an intermediate check plate are affixed within a cylinder at suitable intervals in the axial direction. Inserted movably in the axial direction of the cylinder are a first piston disposed between a pressing lid and the intermediate check plate, a second piston disposed between the intermediate check plate and the partition plate, and a third piston disposed between the partition plate and a pressing lid. A rod which is axially movable within the cylinder has a base end attached to the third piston and a tip end which extends outside from the cylinder through the partition plate, the second piston, the intermediate check plate, the first piston, and the pressing lid. A stopper affixed to a middle portion of the rod moves the first piston or the second piston.

Abstract: Disclosed is a hybrid excavator which reduces the impact generated at the start of the operation of the boom cylinder, or the like, of a hybrid excavator. The hybrid excavator according to the present invention comprises: a hydraulic pump motor connected to an electric motor and operated in the forward or reverse direction; a hydraulic cylinder connected to the hydraulic pump motor and operated in an expanding manner; a first and second hydraulic valve installed in a first and second passage, respectively, between the hydraulic pump motor and the hydraulic cylinder, for blocking the first and second passages when switched by an external control signal; a third hydraulic valve installed in the connecting path connected to first and second dividing passages.

Abstract: A system and method for controlling the movement of an implement of an earthmoving machine. The system includes a hydraulic actuator adapted to move the implement. A variable displacement pump is coupled to the actuator for delivering a pressurized fluid to and receiving pressurized fluid from chambers within the actuator. A sensor generates an output based on the position of the actuator's piston or piston rod, and a controller controls the displacement of the variable displacement pump in response to the output of the sensor by executing an algorithm to reduce the flow rate of the fluid to and from the actuator's chambers and thereby reduce the velocity of the piston as it approaches an end of a piston stroke thereof and prevent the piston from impacting the actuator at the end of the piston stroke.

Abstract: The present invention provides a three position hydraulic piston assembly for a gear ratio change mechanism for a transmission exhibiting reduced gear shift noise. The three position hydraulic piston assembly includes a master piston and motion retarding assemblies that act near both travel limits of the master piston. The master piston includes symmetrical passageways that provide hydraulic fluid flow to small chambers at each end of the piston that are closed off as the piston approaches its travel limits. Hydraulic fluid trapped in the chambers decelerates the piston and is bled off through an orifice allowing the piston to reach its travel limit and quickly and quietly engage a gear ratio.

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: An air compression apparatus has a frame, a tank, and a motor. A drive mechanism is operably connected to the motor and at least one piston assembly is operably connected to the drive mechanism and configured to move within a respective cylinder mounted to the frame. The piston assembly includes: (1) a piston body; (2) a piston rod having a hollow bore connected at one end to the drive mechanism and at an opposite end to the piston body; and (3) a piston valve installed on the piston body. In use, upward travel of the piston body as caused by the drive mechanism acting through the piston rod opens the piston valve and allows ambient air to be drawn through the hollow bore into the cylinder, and downward travel of the piston body closes the piston valve so as to compress the air within the cylinder.

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 bushing for conducting air in a nail gun is arranged between an air chamber and a cylinder received in a housing of the nail gun. The bushing is adjacent to a bottom of a main valve for driving hitting motion of the nail gun. A number of main valve holes that are adjacent to the main valve are formed in a sidewall of the cylinder. At least one air inlet is formed in a bottom of a sidewall of the cylinder. An air flow passage is defined in the housing and is in communication with the main valve and the air hole. A valve plug which is configured for opening or closing the air flow passage is received in the air flow passage. The valve plug divides the air flow passage into an upper portion and a lower portion. The lower portion is formed in the housing. An annular end surface is formed on a top of the bushing. The annular end surface defines a main air inlet for the main valve. An end portion extends from the bushing and having the upper portion of the air flow passage formed therein.

Abstract: A semi-levered landing gear for an aircraft comprises a main shock absorber strut (1) connected to the airframe; a bogie beam (4) extending fore and aft of the airframe with forward and aft wheels (J, T) and a main pivot connection (5) to the strut (1) between the forward and aft wheels (7, T) and an auxiliary actuator (49) connected between the strut (1) and the front of the bogie beam (4) at an auxiliary pivot (14). The auxiliary actuator (49) comprises a two stage telescopic hydraulic unit comprising a first stage piston and cylinder actuator (59, 63) and a second stage piston and cylinder actuator (56, 50) operating coaxially within an outer casing (50). A respective piston rod (65, 60) each extends from each end of the casing (50) and is connected to a respective one of said (strut 1) and bogie beam (4). The first stage actuator (59, 63) is operable to an extended position, and the second stage actuator (56, 60) is operable between a retracted position (FIG. 11) and an extended position (FIG.

Abstract: Disclosed is an apparatus for protecting impact to a rack bar of a power steering gearbox comprising an oil pressure cylinder, to which oil which has passed through an oil pressure pump and a rotary valve is supplied through a left port or right port, a rack bar disposed in the oil pressure cylinder and horizontally reciprocating, a piston fixed at the middle of the rack bar, a first lack bush and a second lack bush disposed at both ends of the cylinder, in which the piston moves, to close the cylinder, and bypass holes with a downward convex shape disposed at both ends of the cylinder adjacent to the first and second rack bushes, in which a part of oil pressure is released immediately before a piston of the rack bar moving by the power of oil pressure reaches a rack bush, whereby impact to the cylinder or noise is not generated.

Abstract: A fastener driving device comprises a housing having a chamber constructed and arranged to contain compressed air, a cylinder disposed within the housing, a piston disposed within the cylinder and movable between upper and lower positions within the cylinder, a fastener striker connected with the piston, a main valve and trigger valve. The main valve is formed from a resilient material having a first portion thereof sealingly engaged with a first portion of the cylinder. The main valve has a second portion thereof movable between a sealing position with a second portion of the cylinder and an unsealed position as a result of flexing of the resilient material. The unsealed position permitting the compressed air to force the piston to move from the upper position to the lower position to enable the fastener striker to move through a fastener driving stroke. The trigger valve is carried by the housing.

Abstract: Disclosed is a piston positioning system for positioning a piston within a cylinder of a pneumatic circuit. The system comprises a piston position indicator for sensing an actual piston position, a controller for generating an output signal in response to the piston position signal, a pneumatic valving device for regulating the flow of pneumatic fluid and a solenoid valve configured to energize the pneumatic valving device. The pneumatic valving device comprises a four-way valve, a servo valve coupled to a stepper motor, and a two-way valve. The reversible stepper motor is incrementally rotatable over a desired angle of rotation in proportion to the magnitude of the output signal for linearly translating the servo valve such that the flow of pneumatic fluid maybe manipulated into and out of first and second ends of the cylinder to control the piston position therewithin.

Abstract: A snubbing arrangement functions to control the rate of deceleration of a piston and rod assembly within a fluid cylinder as the piston and rod assembly nears the bottom of the piston cavity. A flow blocking mechanism is attached to the piston and rod assembly and acts to block flow from the piston cavity through a first head end port. A pressure differential valve mechanism is disposed between a second head end port and the rod end port and operative to control the pressure in the head end cavity relative to the pressure in the rod end cavity.

Abstract: A semi-levered landing gear includes a main strut, a wheel truck pivotally attached at a main pivot to a lower end of the main strut and supporting forward and aft wheels, and an auxiliary strut attached at its upper end to the main strut and at its lower end to the wheel truck forward of the main pivot. The auxiliary strut includes a main piston that slides within a cylinder barrel and is attached at its lower end to the auxiliary pivot, and a floating piston that slides relative to the cylinder barrel and the main piston and divides the cylinder barrel into a pair of fluid chambers. The main piston includes snubbing holes or orifices through which fluid can flow between the two fluid chambers.

Abstract: The invention relates to a pressure-cutoff arrangement for an auxiliary power steering system in the end positions of the steering lock, having at least one working poston 2 which is displaceable in the axial direction in a steering housing 1 and delimits two working spaces I, II, cutoff valves 7, 17 associated with the working piston 2, and also stop elements 13, 23 which are associated with the steering housing 1 and are displaceable in the axial direction and against which one of the cutoff valves 7, 17 runs, in each case, in the end position and, in doing so, opens for the purpose of cutting off the pressure, and wherein the stop elements 13, 23 are fixed in a force-locking manner, with a retaining force which exceeds the opening force of the cutoff valves 7, 17, a spring 14, 24 acting in the radial direction.

Abstract: A bypass valve is disclosed which relieves pressure on the end cap and rod guide of a cylinder as the piston approaches them. The bypass valve has a cylindrical body with end caps on each end, the end caps serving as stop members. The bypass valve is provided with longitudinal grooves along the cylinder body, along which working fluid can pass through a bore in the piston in which the bypass valve is inserted. Inner smaller diameter counterbores and outer larger diameter counterbores are provided coaxially with the bore on the opposing faces of the piston. The end caps of the bypass valve are received in the counterbores when the piston is urged along the cylinder. When the piston approaches either the rod guide or the end cap, the bypass valve is urged away from its seated position when an end cap of the bypass valve touches the approached rod guide or end cap of the cylinder.

Abstract: A method and an apparatus for controlling the function of all kinds of reciprocable power machines which are actuated by pneumatic, hydraulic of any other pressure fluid, irrespective if the machines are of rotary or axially operating type, in which the active power stroke is accomplished using full power of pressure fluid against a reciprocatable piston (2) in the active air pressure chamber (10, 12), and in which the reversing of the direction of operation is made by alternatingly supplying pressure fluid to the opposite air pressure chamber (12, 10) of the machine. A valve poppet (6) having several channels alternately places one of the pressure chambers (10, 12) of the reciprocatable fluid actuated machine (1, 2) under full pressure, builds up a certain counter pressure in a pressure chamber which is, at the actual moment, inactive, and evacuates the pressure from an inactive pressure chamber of the fluid actuated machine.

Abstract: A pneumatic cylinder for actuating fume extraction valves in fume and heat extraction plants has a piston (2) that may be actuated from both sides with at least one working surface and that can be made to slide by pressurised air in a cylinder (1) with at least one working chamber (4), as well as an energy accumulator with regulating means. The regulating means can be controlled by control means to open or keep open the fume extraction valves. In order to obtain a compact pneumatic cylinder for a fume and heat extraction plant which is easy to install, a storage chamber in which air or pressurised air is stored as compressible pressure medium is provided as energy accumulator. The storage chamber is in communication with a compression surface (7) of the piston (2), at its side opposite to the working surface (7), so that pressure medium may flow between the storage chamber and the compression surface (7).

Abstract: For a hydraulic rack-and-pinion steering assembly for which a working piston is guided in a hydraulic cylinder which features an end limit stop by which, in an end position of the working piston, a path for the pressure agent supplied to the working piston by drill holes for the pressure agent is formed from the working space under pressure to a space of less pressure, in order to improve the hydraulic rack-and-pinion steering assembly such that it is simple to manufacture at limited cost, a rack-and-pinion steering assembly is improved by having, in the region of each pressure supply drill hole, at least one drill hole which can be executed and sealed from the housing exterior and which can be connected by means of a connecting line to the respective pressure supply.

Abstract: A multi-axle steering system which is intended for vehicles has a steering gear (4) for a first steering axle (1) and hydrostatic steering for a second steering axle (2). A master cylinder (11) is disposed on the first steering axle (1) and a slave cylinder (23) on the second steering axle (2). The work chambers (12, 13; 24, 25) of the master cylinder (11) and the slave cylinder (23) are connected with each other by pressure lines (26, 27) and in this way together constitute the hydrostatic steering. A centering device (34) for a return of the steered wheels of the second steering axle (2) into their straight-ahead running position is provided on the second steering axle (2).

Abstract: A novel adjustment assembly for use with a hydraulic control apparatus. The hydraulic control apparatus is attached to a hydraulically operated tool to provide a desired hydraulically powered function. The present invention allows the hydraulic control apparatus to be used with either a constant volume (open-center) hydraulic system or constant pressure (closed-center) hydraulic power system. The novel adjustment assembly of the present invention provides a structure which can be configured to force open shuttle spool valves in the control apparatus in a neutral condition for use with a constant volume power supply. The adjustment assembly can also be configured to be disengaged from the shuttle spool valves in a neutral condition for use with a constant pressure hydraulic power system. Operation of the adjustment assembly is made using standard tools and without disassembly of the control apparatus.

Abstract: A relief valve for a hydraulic piston consists of a tubular mid-section with closed ends and circular stops at each end. The tubular center section has cross ports at each end that run perpendicularly to the axis of the valve. The cross parts are situated as close to the end stops as possible. The cross ports intersect the hollow center of the spool and allow hydraulic oil to flow through the piston via the passageway in the center of the valve when the valve is in the open position.

Abstract: In an artificial leg for a person having an upper thigh cut and a knee joint lost, a cylinder disposed between upper and lower leg members, which are coupled through a pivotable joint, for controlling bending and straightening of the joint by an air cushion for convenience of walking. The cylinder includes a cylindrical sleeve closed at both ends and a piston having a piston rod and sliding in the sleeve, and has its structure improved by using as a cushion one of two inner cavities separated by the piston, which encloses the piston rod, thereby buffering butting between the upper and lower leg members to remove unpleasant shock resulting at the end of straightening the joint.

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: Device and procedure for the supply, with recovery of the raising energy, of press actuators having a cylinder within which a piston delimits two chambers, namely an upper and a lower chamber, which are supplied with pneumatic power, the said device having a pneumatic control unit connected to the mains and including at least one supply line to the upper chamber of the actuator and one supply line to the lower chamber of the actuator, these lines having supply and discharge valves, in which device the supply lines to the chambers of the actuator pass through an economizer unit interposed between the control unit and the actuator and including a servocontrolled valve which intercepts the supply line to the upper chamber, a servocontrolled valve which intercepts the supply line to the lower chamber, and a connecting pipe between the supply line of the lower chamber and that of the upper chamber, downstream of the said intercepting valves, and provided with its own servocontrolled intercepting valve, while means

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 hydraulic servo actuator adapted to control a driven member in accordance with an operation of a servo circuit through which servo oil flows comprises a main cylinder and an associated piston, associated piston being reciprocable within the cylinder and the main cylinder divided by the piston into a first chamber and a second chamber which are adapted to be in fluid communication with the servo oil, a damper means provided within the main piston for dampening reciprocating movement of the main piston. A hydraulic servo actuator also includes a throttle means for imparting a predetermined restriction to the servo oil that flows between the second chamber and the damper means along the predetermined passage formed within the cylinder.

Abstract: A gas compressor for use in a gas refrigerator includes a compression space having a volume varied with a positional shift of a piston when the latter reciprocates in a cylinder, a first buffer space communicating with the compression space in one direction with respect to the compression space and a second buffer space communicating with the compression space in the opposite direction. Forces acting on working surfaces of the piston are set in such a way that, when a reciprocation stroke of the piston is to be lengthened, a shift of a neutral position of the piston reciprocation toward the compression space is prevented and, when the reciprocation stroke is to be shortened, a shift of the neutral position away from the compression space is prevented, so that the dead space in the compression space is minimized and a highly efficient operation can be realized in a wide output control range.

Abstract: A flush valve operating means having a housing with a sleeve assembly therein and a piston actuating means within the sleeve, the housing having two fluid inlets and the sleeve having a by-pass means for diverting fluid from one side of the piston to the other to provide equal fluid pressure over the face of the piston and the piston being slidable within the sleeve in response to fluid supply line pressure being applied to one face of the piston to actuate the flush valve.

Abstract: A vehicle steering for turning the steerable wheels of a vehicle having a fluid motor with a housing defining a fluid chamber and a piston in the chamber dividing the chamber into first and second chamber portions. A rotatable steering input member is supported by the housing. A rotatable follow-up member is associated with the piston and rotatable upon movement of the piston in the chamber. A valve controls pressurized fluid flow to the first and second chamber portions. The valve comprises first and second relatively movable valve parts. One of the valve parts is connected with the input member and the other of the valve parts is connected with the follow-up member forming a unit therewith. The unit has a surface against which fluid pressure in the first and second chamber portions acts tending to create an axial force on the unit. Pressure is applied to another surface area of the unit to balance the axial force acting on the unit.

Abstract: Rack and pinion steering gear with hydraulic power assist that is reduced as the vehicle wheels approach their positive wheel stops so that hydraulic loads on the steering gear and linkage are reduced and the power steering pump is not forced to excessive operation in relief.

Abstract: A fluid-operated cylinder to be used as a load lifting cylinder includes a cylinder casing defining a cylinder bore between two opposed ends, one of which ends is provided with a fluid supply/discharge port, a piston unit having a piston element and a piston rod, the piston unit being axially movably arranged in the cylinder bore of the cylinder casing, and a flow rate control valve unit axially movably mounted in the piston element so as to cause a gradual change in a flow rate of working fluid throughout a predetermined amount of piston stroke when the piston unit starts to move out of the cylinder casing and comes to a stop at a bottom position in the cylinder casing, thereby cushioning shock occurring in the fluid-operated cylinder.

Abstract: A full hydraulic power steering system for a forklift truck is disclosed wherein in order to correct the position of a steering wheel in relation to an actuator for a steered wheel, hydraulic fluid is discharged from a portion of hydraulic fluid line means interconnecting a steering unit operable by the steering wheel and the actuator.

Abstract: A hydraulic trim-tilt system for an outboard motor (10) utilizes a first pilot operated relief valve (48) in one trim piston (21) to limit the stroke of the trim pistons (21, 22) under load. After the trim pistons have reached the top of their stroke, under reduced load, the first pilot operated relief valve (48) is blocked and a second pilot operated relief valve (58) operates to allow a higher pressure to be supplied to the trim-tilt unit (16) to lift the outboard propulsion unit (15) in a higher shallow water drive range.

Abstract: An oleodynamic steering control device for vehicles having a straight traveling stabilizer, the device comprising a cylindrical member containing a reciprocatable or rotatable element connected to the main steering system and operative to generate a fluid pressure which is transmitted to a steering actuator on an axle to be steered. The device provides a fluid bypass to a reservoir for a certain range relative to the position corresponding to the straight traveling condition of the vehicle. This relieves the pressures generated by small deviations from straight traveling, which occur at relatively high speed, and thus they are not transmitted and multiplied on the steered axle which is thus stabilized, affording greater traveling safety.

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: An improved trigger valve for a pneumatic nailing machine is disclosed. A communication hole between the main air chamber and the pilot air chamber is made as small as possible. This allows the trigger valve to return in a delayed manner so that the head valve and driver piston operate properly.

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: Disclosed is apparatus for permitting hydraulic lost motion between the push chamber and the pull chamber of the tilt cylinder(s) for a tiltcab truck. The apparatus comprises a pilot-operated check valve having a through passage (a) which is part of a hydraulic connection between the push chamber and the pull chamber and (b) which is only shut off when hydraulic pressure is applied to the push chamber(s) of the tilt cylinder(s).

Abstract: A tool for driving fasteners includes a casing defining a nose portion and a handle portion within which is a reservoir for pressurized fluid. A driver is mounted in the nose portion that is reciprocated by a piston attached thereto and an assembly for returning the piston to a static position after a driving stroke is also included. The return assembly includes a chamber in fluid communication through an inlet with pressurized air and with an outlet that is in communication with a location beneath the return piston. A diaphragm is mounted within the chamber and is biased by pressurized fluid into sealing engagement with the inlet and the outlet. Another metered inlet is also included in the chamber that is in fluid communication with the source of pressurized fluid and controls the sealing action of the diaphragm. The chamber for the return assembly is also in fluid communication with a second chamber within which is mounted a differential area piston.

Abstract: A gripping arrangement includes a gripping member operatively connected with a differential both-side acted piston movable in a pneumatic or hydraulic cylinder. The piston stroke includes a first step and a second step. The pressure acted upon the piston to move the same into the respective gripping position is partially counteracted at the first step so as to eliminate an undesirably fast movement of the gripping member during at least initial portion of the stroke. The remaining portion of the stroke the piston moves under full pressure exerted by the pressure medium supplied in the cylinder without any counteracting effect.

Abstract: The use of the air-spring in automatically retracting (or extending) an air cylinder after it was extended (or retracted) by the air pressure supplied from the compressed air line is disclosed.

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 digitally controllable pneumatic linear actuator in which a moving piston driven by compressed air is initially decelerated by the pressure of compressed air applied to the both sides thereof in the course of its advancing movement toward a predetermined stop position and is then braked by a mechanical brake, thereby obviating failure of precise positioning of the piston due to the compressibility of air. The piston displacement is digitally detected, and the result of detection is fed back to a digital controller.

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 hydraulic actuator comprising a pair of pressure oil chambers each of which has a cushioning port, the two cushioning ports being connected to each other through a cushioning means. The cushioning means includes a pair of cracking valves whose closing pressure is lower than its opening pressure and a pair of restricting means for restricting the flow of a pressure oil provided with regard to said cracking valves. This structure permits an output means for the actuator to be stopped smoothly as a result of fully absorbing the inertial energy that accompanies the output means.