Abstract: In some embodiments, an actuator includes a chamber, a piston disposed within the chamber, and a tube. The chamber has a first port and a second port. The piston comprises a first surface, a second surface, and an elongated conduit coupling the first surface to the second surface. The first surface is disposed between the first port and the second port. The second surface is offset from the first surface. The tube is disposed at least partially within the elongated conduit of the piston. The tube comprises a third port disposed within the elongated conduit of the piston and a fourth port disposed outside of the elongated conduit of the piston.

Abstract: A thermal actuator for a rotating shaft shutdown seal that has a piston with a portion of its axial length enclosed within a cylinder shell with a material, such as a fusible link that changes state or deforms above a given temperature, interposed between a closed end of the cylinder and one end of the piston. The piston is spring biased toward the material and moves toward the closed end of the cylinder when the given temperature is reached and the deformation or change of state of the material makes room for the piston to move toward the closed end. Movement of the piston is transferred through a piston rod to activate the seal.

Abstract: An air compressor assembly includes a cylinder housing, an outlet receptacle disposed on the cylinder housing, and a partition having an air passage formed between the cylinder housing and the outlet receptacle, a piston slidably received in the cylinder housing and having a piston rod extended from a piston head for moving relative to the cylinder housing to generate a pressurized air, the piston head includes an upper surface, and includes a cavity formed in the piston head and defined by a bottom surface and an inner peripheral surface and opened upwardly through the upper surface of the piston head and faced and directed toward the partition of the cylinder housing for partially receiving the pressurized air.

Abstract: The present invention relates to a resonant mechanism for compressors which comprises a tubular body (1) containing at least two slot sets (12) that delimit an intermediate surface (13) which central portion has substantially ellipsoidal conformation (14) on which it is located a hole (15) through which the resonant spring will be affixed (2); a resounding spring (2) housed within the tubular body (1); at least two fastening sets (3) for fastening the resonant spring (2) to the tubular body (1), and leaf flat springs (4) alternately and successively mounted with spacers (not shown) along with the circular side faces (11) of the tubular body (1). The slot sets (12) have a specific configuration to allow rigidity and flexibility suitable for the mechanism operation in situations where the resulting axial force differs from zero.

Abstract: The present invention describes a pumping device (1) for pumping fluids. The pumping device (1) comprises a force transmitting element (2), a tension unit (3) coupled to the force transmitting element (2) and a seal element (10). The force transmitting element (2) is adapted for transferring an upstroke and a downstroke to a pump plunger (5) for pumping fluid (12). The tension unit (3) is adapted for applying a tension force (F) to the force transmitting element (2) for keeping the force transmitting element (2) under tension during the upstroke and the downstroke. The seal element (10) is adapted for sealingly preventing pumping fluids (12) during the downstroke and for enabling pumping fluid (12) during the upstroke. A part (16) of the seal element (10) is rigidly coupled with the force transmitting element (2).

Abstract: A tubular actuator including a flexible tube or roll, operable to shift between first and second configurations so as to define a stroke, and utilizing active material activation to produce, modify, and/or retain the stroke.

Abstract: The present invention describes a pumping device (1) for pumping fluids. The pumping device (1) comprises a force transmitting element (2), a tension unit (3) coupled to the force transmitting element (2) and a seal element (10). The force transmitting element (2) is adapted for transferring an upstroke and a downstroke to a pump plunger (5) for pumping fluid (12). The tension unit (3) is adapted for applying a tension force (F) to the force transmitting element (2) for keeping the force transmitting element (2) under tension during the upstroke and the downstroke. The seal element (10) is adapted for sealingly preventing pumping fluids (12) during the downstroke and for enabling pumping fluid (12) during the upstroke. A part (16) of the seal element (10) is rigidly coupled with the force transmitting element (2).

Abstract: A fluid control or actuation system providing selective recruiting of actuators antagonistic to one another to provide variable output power, such as that used to drive a load. The actuators are intended to comprise different sizes, and to be operable with one or more pressure control valves capable of providing displacement of a non-recruited actuator without requiring active input to cause such displacement. Being able to selectively recruit different sized actuators to drive the load, and being able to displace non-recruited without active input, effectively incorporates a gearing function into the fluid control system.

Abstract: This invention relates to an actuator assembly for a turbocharger pressure control valve assembly and a method of assembling a pressure control assembly of a turbocharger. The assembly comprises an actuator coupled to an actuator rod which in use is coupled to the valve assembly to control the position thereof. The actuator rod comprises an elongate member at least a portion of which is flexible. The actuator rod may be a resilient member which may be substantially straight when stressed. In use the actuator rod may extend in a substantially straight line between the actuator and the valve assembly.

Abstract: Various embodiments of the invention provide pumps, plungers and plunger assemblies, as well as methods of using them. In accordance with some embodiments, a plunger may comprise a ceramic material and/or may have a facial profile that may allow for more efficient pumping operations. In particular embodiments, for example, a plunger may have a facial profile that allows for deformation of at least a portion of the plunger when the face of the plunger is in contact with a pressurized fluid. Other embodiments provide plunger assemblies, which may comprise a flexible coupling attachment. Yet other embodiments provide pumps comprising such plungers and/or plunger assemblies.

Abstract: A rotary actuator assembly is provided. The assembly has a flexible member that is attached to a piston for linear movement. The flexible member is also attached to a pinion for pivotable movement.

Abstract: This invention relates to an actuator assembly for a turbocharger pressure control valve assembly and a method of assembling a pressure control assembly of a turbocharger. The assembly comprises an actuator coupled to an actuator rod which in use is coupled to the valve assembly to control the position thereof. The actuator rod comprises an elongate member at least a portion of which is flexible. The actuator rod may be a resilient member which may be substantially straight when stressed. In use the actuator rod may extend in a substantially straight line between the actuator and the valve assembly.

Abstract: A rotary actuator assembly is provided. The assembly has a flexible member that is attached to a piston for linear movement. The flexible member is also attached to a pinion for pivotable movement.

Abstract: Apparatus comprising a pump or compressor operated by a pull-cord wound around a pulley (9), in which the pulley drives a shaft (11) which drives the pump or compressor, and the pulley is recoiled by means of a retractor type spring (32), torsion bar or elastic band. The retractor spring is mounted not both co-planar and co-axial with the pulley. The principal may be applied to reciprocating or rotary pumps or compressors, with compressible or incompressible fluid.

Abstract: An actuator which comprises a pair of elongated elastomer tubes (6,16), sealed by respective members (18, 20, 22, 24) at each end, the members at the one end (18, 20) being fixed and the members at the opposite end (22, 24) sliding in guides (34, 36), the sliding ends of the first and second tubes being connected by a chain (26) and sprocket (10) to convert linear motion to rotary motion.

Abstract: An actuator which comprises a pair of elongated elastomer tubes (6,16), sealed by respective members (18, 20, 22, 24) at each end, the members at the one end (18, 20) being fixed and the members at the opposite end (22, 24) sliding in guides (34, 36), the sli ding ends of the first and second tubes being connected by a chain (26) and sprocket (10) to convert linear motion to rotary motion.

Abstract: A rotary actuator assembly is provided. The assembly has a flexible member that is attached to a piston for linear movement. The flexible member is also attached to a pinion for pivotable movement.

Abstract: Artificial muscle analog 1000 is located within hollow exoskeletal bone 10. Muscle 1000 comprises inflatable bladder 120, cable 130, roller 140, anchor point 150, and connection means 160 whereby said bladder may be inflated and deflated. Bladder 120 is affixed to the interior surface of said bone. Cable 130, attached to bone 10 at point 150, passes over bladder 120 and through roller 140. Cable 130, if unobstructed and taut, takes a shortest path from point 150 to roller 140. When inflated, bladder 120 forces cable 130 to deviate from this shortest path, pulling cable 130 in through said roller, under tension. In their paired opposing muscle form 2000, the artificial muscles synergistically assist each other when used in opposition. Paired muscles 2000 may actuate a robotic arm 3000, and are easily controlled by the associated simple low-cost control systems 100a,b,c of the present invention.

Abstract: A self-balancing synchronization assembly has a support beam pivotally mounted on a guide rail adjacent a hydraulic elevator jack. A synchronization bracket is pivotally mounted at one end of the beam and a pair of synchronization cables is connected between the bracket and a telescoping part of the jack. A return cable is connected between the other end of the beam and the hoistway pit to balance the load and includes a turnbuckle for retensioning the synchronization cables. A second synchronization bracket can be pivotally mounted at the one end of the support beam to synchronize a three-stage jack.

Abstract: A rodless cylinder using a round stick type chain can be applied to a carrier for transportation of materials. The rodless cylinder uses a round stick type chain having the round stick type chain and the chain sprocket, which serve to guide the round stick type chain in a caterpillar form. The chain sprocket is axially formed on either side of the frame consisting of the rodless cylinder to install the round stick type chain in a caterpillar form. Both sides of the round stick type chain are connected to a piston within the cylinder on the frame and to a tension adjustment nut on the connector, respectively. The connector is guided to the guide bar formed between the frame vertically and selectively linked to the carrier.

Abstract: This invention relates to a rodless cylinder using a round stick type chain, wherein it can be applied to an elevator or a carrier for horizontal movement for the efficient transportation of materials in the industrial fields with better durability and safety of rodless cylinder, as well as the cost-saving effects in manufacture. This invention further related to the rodless cylinder using a round stick type chain having the round stick type chain and the chain sprocket which serves to guide the round stick type chain in a caterpillar form.

Abstract: A transmission cylinder without axial limitation. A piston is disposed in the transmission cylinder. Multiple flexible members are disposed on one side of the piston. A resilient member is fitted around the flexible members. Each flexible member extends within a guide member which is fixed at a portion of a certain structure. The piston is driven by a power source, whereby the flexible members are flexibly moved along and within the guide member to transmit power in multiple axial directions.

Abstract: A pneumatic linear actuator has a body (10), a chamber (14) in the body that is closed by the end heads (15), a piston (11) that is arranged in the chamber and moved by a fluid sent alternately to the ends of the piston, and a slide or carriage (13) that is movable on the body driven by the piston. A belt (20) is driven on pulleys (19, 21, 22) and connects the piston to the slide, so that a stroke and a velocity at least twice that of the slide correspond to the stroke of the piston.

Abstract: A flexible piston rod for an injection device, which piston has the form of a helical spring made from a number of narrowly adjacent turns of windings. These turns provide an external thread fitting into the internal thread of a nut element. When the nut element is rotated, the piston rod is advanced forward, which movement is used to displace a piston inside a cartridge containing a fluid to be expelled. In order to prevent the piston rod from rotating when the nut element is rotated, the helical spring making up the piston rod is provided with a longitudinal spine, which is located at a peripheral area of the helical spring.

Abstract: An oilless high pressure pump suitable for use in devices such as pressure washers and the like is described. The pump includes an eccentric assembly suitable for converting rotary motion of a rotating shaft to rectilinear motion. One or more straps couple the eccentric assembly to the pump's piston assembly. The straps communicate the rectilinear motion of the eccentric assembly to the piston assembly for reciprocating the pump's pistons to pump the liquid.

Abstract: An anti-skid mechanism operating device includes an operating unit and an operating arm pivotally supported thereby and intended to carry a rotary anti-skid and to operate the latter between an active position and a passive position. The operating unit is formed with a linear drive and a rotationally mounted rotary device, which is connected to the operating arm. A string-like drive transmission element extends essentially along the longitudinal axis of the drive, between the drive and the rotary device, in order to translate a linear movement of the drive into a pivotal movement of the operating arm in two opposite directions.

Abstract: Piston-cylinder assembly, in particular gas spring, comprising a cylinder as a first structural unit, in which a piston rod is arranged in an axially movable manner as a second structural unit. An adjusting device exerting an adjusting force includes an acturator and a force-transmitting means operatively connected to the piston-cylinder assembly, the force-transmitting means engaging concentrically on one of the two structural units of the piston-cylinder assembly.

Abstract: A portable apparatus for ventilation support to persons with respiratory distress is provided with a compressed air pump. The pump may be connected to the mouth or the nose via a tube for generation of pressure pulses with an individually adaptable air volume. The pump comprises a rigid container having two symmetrical halves and with a flexible membrane which is located as a laterally reciprocating diaphragm between the two container halves. These are provided with check valves permitting ambient air to be fed into the pump and from the pump into the tube while the membrane wall is moved, for generation of a pressure pulse. The pump is provided with a flexible pull device for reciprocating operation of the membrane in the container. The pull device extends via pulley wheels to a driving device located substantially in the same plane as the container and beside it.

Abstract: A linear positioning apparatus has a positioning actuator assembly including a cylinder and movable piston to be used for moving a workpiece or a moveable worktable along a rectilinear path or thrust axis. The apparatus includes at least one stop member adjustably mounted on a support such as a plate or hub. To stop the worktable at a selected stop point, each stop member can be positioned to engage an object, for convenience referred to herein as a bumper, that is connected to the moveable worktable to halt movement when the correct position has been reached. The apparatus includes means such as an actuator operatively associated to provide relative aligning movement between the stop member and bumper for placing the bumper and a selected one of the stop members in alignment with each other. The support for the stop member, e.g., a plate or hub, includes a bore or passage that extends entirely through it for each stop member so that each stop member can project out through both sides of the support.

Abstract: A pneumatic linear actuator has a body (10), a chamber (14) in the body that is closed by the end heads (15), a piston (11) that is arranged in the chamber and moved by a fluid sent alternately to the ends of the piston, and a slide or carriage (13) that is movable on the body driven by the piston. A belt (20) is driven on pulleys (19, 21, 22) and connects the piston to the slide, so that a stroke and a velocity at least twice that of the slide correspond to the stroke of the piston.

Abstract: A pressurized working environment for a pneumatic device which permits emission-free utilization of the potential mechanical energy of pressure differentials within compressed gas systems is disclosed. The pneumatic device is contained within a pressure vessel and the pneumatic device exhaust is in fluid communication with the interior of the pressure vessel. In use, the interior of the pressure vessel is in fluid communication with an area of lower pressure in the compressed gas system and the pneumatic device intake is in fluid communication with an area of higher pressure in the compressed gas system. In use, the gas from the area of higher pressure drives the pneumatic device and is then exhausted to the area of lower pressure.

Abstract: A flexible piston rod for an injection device, which piston has the form of a helical spring made up from a number of narrowly adjacent turns of windings. These turns provide an external thread, which thread fits into the internal thread of a nut element. When the nut element is rotated the piston rod is advanced forward, which movement is used to displace a piston inside a cartridge containing a fluid to be expelled. In order to prevent the piston rod from rotating when the nut element is rotated, the helical spring making up the piston rod is provided with a longitudinal spine, which is located at a peripheral area of the helical spring. The spine can either be a mechanical removal of a part of the out-turned area of each winding, or it can be a reduction or removal of an initial tension in a longitudinal area of the helical spring.

Abstract: An actuator for rotating a shaft includes a housing having a first port, a second port and a drive track. A first drive means is coupled to the first port and a second drive means is coupled to the second port. An array of balls which are spaced apart by spacers define a drive train extending from the first drive means to the second drive means via the drive track. A drive pin which extends outwardly from the shaft is connected to the drive train and the first and second drive means are driven so that the drive train will rotate the drive pin and hence the shaft.

Abstract: A rodless cylinder actuator for moving a slide table in machine tools is disclosed. In the actuator, two pneumatic or hydraulic cylinders are parallely arranged to be directed in opposite directions. At least one pulley is rotatably mounted to the outside end of the piston rod of each cylinder using a bracket. A wire is fixed to the cover of a cylinder housing at both ends thereof and passes over the pulleys of the two piston rods. The slide table is mounted to the middle portion of the wire, thus being linearly and longitudinally reciprocable on the top surface of the cylinder housing in accordance with a movement of the piston rods relative to the two cylinders. A connection rod extends between the brackets of the two piston rods, thus maintaining a desired interval between the two brackets. The rodless cylinder actuator of this invention has a simple construction capable of reducing the production cost of such actuators.

Abstract: A system for deforming or actuating an elastomeric structure is described. he system includes a plurality of tubes joined to the elastomeric structure. The tubes extend in the direction of a desired strain to be applied to the elastomeric structure and are constrained from circumferential expansion. When a pressurized fluid is applied to the tubes, the tubes deform causing a like deformation of the elastomeric structure.

Abstract: A positive displacement pump is provided having a housing, a plurality of pistons and an eccentric drive element rotatably mounted about an axis on the housing. A rigid compression member connected to each of the pistons is reciprocatably moveable with the pistons relative to the housing. At least one tension member is provided, connected between each of the pistons and the eccentric drive element at a point displaced from the axis. The tension member is permanently maintained in tension so as to continuously exert force radially inwardly on each of the pistons and to cause each of the pistons to continuously exert radially inward force on the compression member to permanently maintain the compression member in compression. The plurality of pistons preferably includes one or more pairs of pistons with each piston of the pair linked together by the compression element and reciprocates each in synchronism and 180.degree. out of phase with the other.

Abstract: A load transfer device for use with tandem mounted actuators. The load transfer device includes an actuator coupling assembly and a ground connection assembly. The actuator coupling assembly connects the first actuator to the second actuator and includes a movement apparatus. The movement apparatus is configured to allow the housing of the first actuator to move relative to the housing of the second actuator. The ground connection assembly is associated with the actuator coupling assembly and movably connects the first and second actuators to a rigid support structure. During a load transfer operation, the actuator coupling assembly transfers an unequal load from the first actuator to the second actuator. In particular, the movement apparatus allows the first actuator to move relative to the second actuator. Further, the actuator coupling assembly is configured to transpose movement of the first actuator into a forced, reciprocal movement of the second actuator.

Abstract: A rotary valve actuator with movable actuator linkage maintained in a constant "pull-pull" tension, includes a sliding canister, rotatable lever, and a return spring substantially aligned in-line with each other. The linear motion of the canister in response to an expanding and contracting pressurized bladder is converted through chain linkage into rotary lever motion. The return spring is connected through respective chain linkage to the lever so the pulling tension of the spring/lever linkage rotates the lever and maintains tension on both chain linkages. Adjustable travel stops are provided. In an alternate embodiment the return spring chain linkage is configured at right angles to the linear movement of the canister. A double acting rotary valve actuator with pressurized bladders on opposite sides of a rotatable lever. One bladder is oval shaped.

Abstract: A log trailer load booster is described for construction in combination with or attachment to a log trailer having a wheeled trailer frame, a payload receiving bunk on the trailer frame, and an elongated trailer beam for connection to a log truck. The booster includes an elongated booster frame with a pivot connection on the booster frame configured to pivotably connect the booster frame to the trailer frame for up and down pivotal movement about a horizontal axis. A booster axle is mounted by a suspension on the booster frame. A link is configured to connect the trailer frame and booster frame and is selectively operable between a locked condition in which upward pivotal movement of the booster frame relative to the trailer frame about the horizontal axis is limited and an unlocked condition in which the booster frame is allowed substantially free pivotal movement about the horizontal axis relative to the trailer frame.

Abstract: A slot bearing assembly for a member moveable relative to a slot such as a carrier for a slotted rodless cylinder in which the slot bearing is allowed to float relative to the moveable carrier.

Abstract: A volumetric pump for administering intravenous fluids to a patient includes a first housing having an elongate cavity therein with an open and a closed end. A resilient sheet of material having a centrally-located aperture covers the open end, and a pump shaft is slidably disposed through the aperture to form a sphincter seal therebetween. An inlet conduit leading from a fluid source (an IV bag) passes through the housing into the cavity near the open end thereof, and an outlet conduit leading to a fluid sink (the patient) passes through the housing from the cavity near the closed end thereof. A drive shaft is attached to the pump shaft to drive it back and forth in reciprocating motion inwardly and outwardly of the cavity to produce, respectively, a positive pressure forcing fluid out of the outlet conduit to the fluid sink, and a negative pressure forcing fluid from the fluid source through the inlet conduit.

Abstract: A rotary valve actuator with movable actuator linkage maintained in a constant "pull-pull" tension, includes a sliding canister, rotatable lever, and a return spring substantially aligned in-line with each other. The linear motion of the canister in response to an expanding and contracting pressurized bladder is converted through chain linkage into rotary lever motion. The return spring is connected through respective chain linkage to the lever so the pulling tension of the spring/lever linkage rotates the lever and maintains tension on both chain linkages. Adjustable travel stops are provided. In an alternate embodiment the return spring chain linkage is configured at right angles to the linear movement of the canister.

Abstract: A pump system for producing high and exactly controllable pressure levels includes a piston pump which has a piston (32) connecting to a spindle shaft (22), a spindle nut (44) on said spindle shaft, a cylinder block (34) having a bore (36) for receiving said piston, a mechanism (14, 16, 26) for imparting relative rotational and axial motions between said piston and said cylinder block including a device for causing relative rotary motion of said spindle and spindle nut. A helical spring (46) or other resilient element is connected between said cylinder block (34) and said spindle nut (44) to compensate the reaction force generated by a pressurized fluid sample in said cylinder bore (36) when put under compresion. A flexible element (30) is connected between the piston (32) and the spindle shaft (22) to compensate for any axial misalignment of the piston and the cylinder bore. Methods for operating such a system under adiabatic, isothermal, isobaric and isochoric conditions are described. (FIG. 3).

Abstract: The slide unit includes a rodless power cylinder having a cylinder tube. End caps are attached to both ends of the cylinder tube. A slit extending in parallel with the axis of the cylinder tube is formed on the wall of the cylinder tube. A piston is disposed in the bore of the cylinder tube and is movable along the slit. An external carriage is connected with the piston by a yoke extending through the slit. An inner seal band and an outer seal band extending along the slit for closing the opening of the slit from the inside and outside, respectively, are provided. The ends of the inner seal band and the outer seal band are inserted into corresponding recesses formed on each of the inner end faces of the end caps. A pin hole crossing the recesses and extending to the upper face of each end cap is provided. A fitting hole is disposed on each end of the inner seal band and the outer seal band at the position corresponding to the pin hole.

Abstract: A linear actuator comprising a guide section formed along a longitudinal direction to protrude on a bottom surface of a slide table, a pair of guide blocks formed mutually opposingly and seperated from each other by a predetermined spacing distance on an upper surface of the main cylinder body, attachment holes for attaching the main cylinder body to another member in any direction of attachment from a side of the slide table or from a side of the main cylinder body, and an adjuster bolt for adjusting an amount of displacement of the slide table.

Abstract: A flexible plunger apparatus includes an elongated flexible member having a pair of opposite end portions and a longitudinal length extending between the opposite end portions, with the flexible member being adapted to flex in transverse relationship to its length and to undergo free movement through a hollow tubing of a well. The apparatus also includes a physical barrier producing mechanism attached to and extending between the opposite end portions of the flexible member for substantially separating gas under pressure in the tubing below the lower end portion of the flexible member from a slug of liquid in the tubing above the upper end portion of the flexible member. The physically barrier producing mechanism is carried along the interior surface of the tubing in a substantially sealing relationship therewith as the flexible member undergoes free movement through the tubing of the well in response to the pressure of the gas and opening of the tubing of the well at the earth surface.

Abstract: Power transmission torque transmitting assemblies, such as clutches and brakes, have an axially movable piston which is hydraulically actuated to engage and enforce frictional contact between a plurality of friction discs. Upon piston retraction during disengagement, a stroke adjustment mechanism establishes the retraction distance of the piston and thereby the free-running clearance in the torque transmitter. The stroke adjustment mechanism has a helical gear movable axially with the piston during engagement and disengagement. During engagement, the piston is free to rotate as required by a retainer plate to accommodate fall engagement with the torque transmitting assembly. During disengagement, a one-way assembly prevents rotation of the gear relative to a spring retainer plate and limits axial movement of the piston relative to the retainer plate to establish the disengaged position of the piston and the proper free-running clearance in the torque transmitting assembly.

Abstract: In a hydraulic rodless cylinder type actuator, a piston is movable back and forth in a hydraulic cylinder. Housing elements are respectively mounted on the opposite ends of the cylinder. Parallel output shafts are respectively accommodated in the housing elements and protrude therefrom in a fluid-tight condition. The linear movement of the piston is translated into the rotation of the output shafts by flexible inner power transmission elements. Flexible outer power transmission elements are provided on the protruding ends of the output shafts in order to deliver a high output from a high-pressure chamber defined in the cylinder to the outside of the cylinder.

Abstract: A rodless cylinder has a linear guide which primarily bears loads F.sub.1, F.sub.2, F.sub.3 applied to a slide table and a table guide which secondarily bears those loads F.sub.1, F.sub.2, F.sub.3. The table guide has a centering function performed by being displaced a small distance in a direction substantially perpendicular to the axis thereof when a load is applied to the slide table.

Abstract: A linear actuator has an actuator body having a through hole defined axially therein and an opening defined in an upper surface thereof, a pair of end blocks, a slide table reciprocally movable in the directions indicated by the arrows X, Y, a pair of cylindrical members coupled to the end blocks, respectively, and having respective passages communicating with fluid outlet/inlet ports, respectively, defined in the actuator body, a joint member movable in unison with the slide table, a pair of cover members held in surface-to-surface contact with the joint member in confronting relation to each other and hermetically surrounding outer circumferential surfaces of the cylindrical members, for sliding displacement in unison with the slide table, and a pair of pressure chambers defined by the cylindrical members and the cover members and closed by the cover members, the pressure chambers communicating with passages in the cylindrical members.