Abstract: A fluid valve control system includes a linear actuator assembly with a linear actuator, a mechanical amplifier, and a mechanical output member; a fluid control valve, including: a valve body with a fluid chamber and an outlet aperture, a fluid supply line, a plunger member; a fluid reservoir with a pressurized fluid, and a fluid dispensing control unit; such that the fluid flows in a flow from the fluid supply line into the fluid chamber and out via the outlet aperture; such that plunger member moves vertically downward when the outer end of the plunger member is impacted by the mechanical output member, such that an inner end of the plunger member blocks the outlet aperture, such that the flow of the fluid is interrupted.

Abstract: A fluid pressure controlled spool valve minimizes abrasion or sticking caused by a tilted orientation of a pressure plate forcing lands of a spool shaft to abrade or stick internally facing surfaces of a cylindrical barrel supporting the spool shaft. A permanent magnet is mounted on the pressure plate. A round head composed of a ferromagnetic material is formed on an end of a spool shaft and configured to be magnetically attracted to the permanent magnet. A magnetic attraction force vector produced on the round head of the spool shaft remains coaxial with an axis of the spool shaft, when the pressure plate and the magnet are tilted with respect to the axis of the spool shaft.

Abstract: A pneumatic actuator (312, 412) adapted for use with a turbocharger includes a diaphragm (16) having a valley (46), and a piston (314, 414) having a lip (350, 450) extending from a flange (344, 444). A portion of the lip (350, 450) curves or bends around the diaphragm (16) and possibly forms a double bend. The distal end (348, 448) of the piston (314, 414) is adapted to contact a majority of the valley (46) of the diaphragm (16) in its preloaded state. The distal end (348, 448) may have a complementary shape with a shape of the valley (46). The edge of the flange (344, 444) is always spaced away from the diaphragm (16) to prevent contact of the edge with the diaphragm (16).

Abstract: A method for manufacturing a valve unit includes fixing a first flow channel member and a flexible member to one another, the first flow channel member including a first surface, a second surface and a through-hole passing through the first surface and the second surface, in a manner in which the flexible member is supported by a fixing member and the through-hole is covered at the first surface side thereof by the flexible member; and fixing the first flow channel member and a second flow channel member, the second flow channel member including a hole through which a valve body passes, in a manner in which the through-hole is in communication with the hole at the second surface side of the through-hole, the valve body configured to open and close a flow channel in communication with the through-hole according to displacement of the flexible member.

Abstract: The seal made between two surfaces is enhanced by forming a coating, such as a self-assembled monolayer of a functionalized fluorinated macromolecule, on one or both of the surfaces.

Abstract: Fluid valve actuator apparatus having internal tubing and anti-rotation features are disclosed. An example actuator apparatus includes an actuator casing and a diaphragm plate disposed within the actuator casing. The diaphragm plate defines a first pressure chamber and a second pressure chamber opposite the first pressure chamber. A yoke couples the actuator casing to a fluid valve. The yoke includes a first internal fluid passageway in fluid communication with atmosphere and a second internal fluid passageway to receive a control fluid from a controller. A tube fluidly couples the first or second internal fluid passageway to the first pressure chamber via an opening in the diaphragm plate. The tube also prevents the diaphragm plate from rotating relative to the actuator casing.

Abstract: Actuator apparatus having internal passageways are disclosed. An example apparatus includes an actuator casing having a load apparatus to define an upper pressure chamber and a lower pressure chamber. The upper pressure chamber is opposite the lower pressure chamber. A yoke is to couple to the actuator casing to a fluid valve. An internal passageway is formed in a body of the yoke to fluidly couple a control fluid to at least one of the first or the lower pressure chamber. A fluid connector assembly is positioned in the actuator casing to fluidly couple the internal passageway to the upper pressure chamber. The load apparatus is between the internal passageway of the yoke and the upper pressure chamber.

Abstract: Embodiments of a method of operating a safety valve and a safety valve system are provided. The valve system includes a valve, an actuator, a mechanical override, and an indicator. The actuator includes a fail-safe mechanism and the indicator is configured to indicate whether the fail-safe mechanism is operable during use of at least one of the actuator and the mechanical override. In one embodiment, a method of operating the safety valve includes actuating the valve into an open position and sending a signal to indicate that the fail-safe mechanism is operable to move the valve to the closed position, while the valve is in the open position.

Abstract: In a control device for a technical processing plant, a pneumatically driven actuator having an actuator stem is provided together with a valve operated by the actuator, the valve having a valve stem. A valve element is attached to the valve stem. A stem connector connects the two stems to each other for a forced transmission of axial actuating movements and for modifying an axial distance between adjacent ends of the valve stem and the actuator stem to adjust a total axial length of the two stems. The stem connector comprises two half-shells connected to each other, and two positioning devices are provided for a friction-locking coupling of the half-shells to the respective ends. At least one of the positioning devices is designed to modify an axial attachment position of the half-shells along one of the stems.

Abstract: An actuator for operating a linear valve, such as a gate valve, includes a sealing plate that extends across the diameter of a housing. A diaphragm is located on, and fully supported by, the plate. When pressure media urges the diaphragm and sealing plate downward, the sealing plate urges a step downward to actuate a valve. A hub and an annular support plate can be assembled to form the plate, and the plate can be different sizes by selecting different sized annular support plates.

Abstract: An apparatus for actuating a valve includes a housing having an axis, a valve end, a cap end, and a cylindrical sidewall defining an inner diameter surface of the housing. A cap is connected to the cap end of the housing. An inlet is located in one of the cap and the housing. A plate is positioned within the housing, the plate having an outer diameter that slidingly engages the inner diameter surface of the housing. The plate moves between an extended position and a retracted position in response to pressure media from the inlet. A down stop is in contact with the plate. A seal nut has a first end in engagement with the down stop. The seal nut has a second end with an end surface, the end surface being spaced apart from the cap when the plate is in the extended position.

Abstract: An actuator for operating a linear valve, such as a gate valve, includes a swivel coupling for detachably connecting an indicator stem to a plate within the actuator. In embodiments, the coupling includes a body with a lock ring groove. The detachable stem includes a downward facing recess having a groove on an inner diameter surface. The stem is placed on the body, and a lock ring engages both grooves to prevent axial movement of the stem relative to the body. The lock ring does not, however, prevent rotational movement of the stem relative to the body.

Abstract: Embodiments of a method of operating a safety valve and a safety valve system are provided. The valve system includes a valve, an actuator, a mechanical override, and an indicator. The actuator includes a fail-safe mechanism and the indicator is configured to indicate whether the fail-safe mechanism is operable during use of at least one of the actuator and the mechanical override. In one embodiment, a method of operating the safety valve includes actuating the valve into an open position and sending a signal to indicate that the fail-safe mechanism is operable to move the valve to the closed position, while the valve is in the open position.

Abstract: In an assembling structure of an actuator part of a chemical liquid valve, a cover is formed with a protrusion extending in a radial direction of a valve element, and a cylinder is formed with an engagement part engageable with the protrusion. A cover is placed to hold a spring in a compressed state in the cylinder and make a cap part cover an opening of the cylinder. The protrusion and the engagement part are engaged with each other to integrally connect the cylinder and the cover without separating from each other.

Abstract: A valve actuator apparatus and method for adjusting for valve bore drift using an adjustable downstop is disclosed. The adjustable downstop comprises a downstop and a drift adjuster. The drift adjuster can me moved in an upwards or downwards direction to increase or decrease the stroke length of the operator shaft.

Abstract: Embodiments of a method of operating a safety valve and a safety valve system are provided. The valve system includes a valve, an actuator, a mechanical override, and an indicator. The actuator includes a fail-safe mechanism and the indicator is configured to indicate whether the fail-safe mechanism is operable during use of at least one of the actuator and the mechanical override. In one embodiment, a method of operating the safety valve includes actuating the valve into an open position and sending a signal to indicate that the fail-safe mechanism is operable to move the valve to the closed position, while the valve is in the open position.

Abstract: A regulator (108) comprising a first chamber (132), and second chamber (134) and an actuator (130). The second chamber (134) is coupled to the first chamber (132) through an aperture (156). The actuator (130) is arranged to the adjust the size of the aperture (156) according to a pressure differential between fluid pressure in the first chamber (132) and a pressure reference (36). The rate of change of the cross sectional area of the aperture (156) is arranged to have a non-linear response to a change in the pressure differential.

Abstract: A liquid dispensing valve includes a liquid dispensing portion with a liquid inlet, a liquid outlet, and a liquid passage communicating between the liquid inlet and liquid outlet. A valve member is mounted for movement relative to the liquid outlet between open and closed positions. An actuation portion is coupled with the liquid dispensing portion and includes an inflatable bladder structure. The inflatable bladder structure includes an interior adapted to be coupled in fluid communication with a source of positively pressurized air. The bladder structure may be expanded by the positively pressurized air to move the valve member to at least one of the open or closed positions from the other of the open or closed positions. Methods of dispensing liquid, such as hot melt adhesive, from the valve are also disclosed.

Abstract: A valve manifold assembly including a manifold body defining a primary flow passage and a secondary flow passage fluidly coupled therewith through an aperture in the wall of the primary flow passage. A valve including a head portion and a stem extending therefrom is disposed through the aperture. The head portion has a valve sealing surface adjacent and extending around the stem, and a valve seat having a seat sealing surface facing into the primary flow passage extends around the aperture. The valve is selectively shiftable between a closed position wherein the valve sealing surface is sealingly engaged with the seat sealing surface to block fluid flow between the secondary flow passage and the primary flow passage, and an open position wherein the valve sealing surface is spaced apart from the seat sealing surface to enable fluid flow between the secondary flow passage and the primary flow passage.

Abstract: A hydraulic actuating device for a sliding stem control valve assembly is mounted between a control valve and an actuator housing. The hydraulic actuating device is connected to one of a control valve stem, an actuator stem, and a stem connector and the hydraulic actuating device moves either the control valve stem, the actuator stem, or the stem connector in response to varying hydraulic pressure within the hydraulic actuating device. The hydraulic actuating device may be used to override an actuator of the sliding stem valve during emergency operations, or to provide a backup actuator in the case of a primary actuator malfunction.

Abstract: Bonnet apparatus to provide live-loading to a seal are described herein. An example bonnet assembly includes a housing having a recessed opening to define a shoulder and a sealing disc disposed within the recessed opening. A biasing element is disposed in the recessed opening between a flange of the sealing disc and the shoulder of the housing to provide a load to a seal to be disposed between the housing and the fluid device. The biasing element biases the sealing disc away from the housing and the biasing element enables the sealing disc to move within the recessed opening relative to the housing when the bonnet assembly is coupled to the fluid device.

Abstract: Actuator apparatus having internal passageways are disclosed. An example apparatus includes an actuator casing having a load apparatus to define an upper pressure chamber and a lower pressure chamber. The upper pressure chamber is opposite the lower pressure chamber. A yoke is to couple to the actuator casing to a fluid valve. An internal passageway is formed in a body of the yoke to fluidly couple a control fluid to at least one of the first or the lower pressure chamber. A fluid connector assembly is positioned in the actuator casing to fluidly couple the internal passageway to the upper pressure chamber. The load apparatus is between the internal passageway of the yoke and the upper pressure chamber.

Abstract: A flow controller device for controlling a fluid flow between a petroleum reservoir and a pipe body is described. The fluid flow is carried through a flow restriction. A pressure-controlled actuator is connected to a valve body that cooperates with a valve opening. The valve opening is connected in series subsequent to the flow restriction. A closing side of the actuator communicates with fluid located upstream of the flow restriction. An opening side of the actuator communicates with a fluid located downstream of the flow restriction and upstream of the valve opening.

Abstract: A valve actuator apparatus and method for preventing latitudinal movement of a diaphragm actuator spring. The downstop is fitted with spring retainers to prevent latitudinal movement of the spring upon compression.

Abstract: A valve actuator apparatus having improved diaphragm retention to protect against tensile loading and ability to adjust the top shaft diameter within said actuator.

Abstract: A valve-closing pressure chamber and a valve-opening pressure chamber are arranged on both sides of a main diaphragm inside an outlet shutoff valve. An upper supply/discharge tube and a lower supply/discharge tube are connected to a housing forming the outlet shutoff valve. The upper and lower supply/discharge tube supply and discharge air to and from the valve-closing pressure chamber and the valve-opening pressure chamber, respectively. An opening end, which is on the pressure chamber side, of each supply/discharge tube is obliquely cut relative to the direction of axis of the supply/discharge tube, which increases the opening area of the opening end. This prevents water present in the pressure chamber from adhering to the opening end of each supply/discharge tube and prevents the adhered water from freezing. This in turn prevents the opening end of the supply/discharge tube from being closed or the opening area from being reduced. As a result, operation performance of the outlet shutoff valve is enhanced.

Abstract: A gas pressure regulator comprises a main body having a first, gas inlet pipe and a second, gas outlet pipe, a calibrated gas passage through which gas flows from the first pipe to the second pipe, a shutter housed at least partially in the main body and mobile lengthwise along a first defined line to adjust the opening of the calibrated passage, a device for actuating the shutter and a regulator spring unit opposing the movement of the shutter.

Abstract: A control valve has a body that forms a valve chamber and a valve seat, a metal diaphragm installed inside the valve chamber and making contact with and departing from the valve seat, an actuator box fixed to the side of the body, a piezoelectric element installed inside the actuator box to thrust the metal diaphragm through mediation of a metal diaphragm presser by elongating downward when voltage is applied, a conical spring mechanism that absorbs elongation of the piezoelectric element at the time when the metal diaphragm makes contact with the valve seat and a prescribed thrust is applied to the valve seat and the like, and a preload mechanism that applies upward compressive force to the piezoelectric element all the time wherein the compressive force applied to the piezoelectric element is externally adjustable.

Abstract: A control valve has a body that forms a valve chamber and a valve seat, a metal diaphragm installed inside the valve chamber and making contact with and departing from the valve seat, an actuator box fixed to the side of the body, a piezoelectric element installed inside the actuator box to thrust the metal diaphragm through mediation of a metal diaphragm presser by elongating downward when voltage is applied, a conical spring mechanism that absorbs elongation of the piezoelectric element at the time when the metal diaphragm makes contact with the valve seat and a prescribed thrust is applied to the valve seat and the like, and a preload mechanism that applies upward compressive force to the piezoelectric element all the time wherein the compressive force applied to the piezoelectric element is externally adjustable.

Abstract: Stable flow control is made possible even under high-temperature environments by relieving tensional force applied to a piezoelectric element when a piezoelectric actuator is retracted. Thus, a piezoelectric driven control valve includes: a body having a valve seat; a metal diaphragm to contact with and separate from the valve seat; an actuator box supported ascendably and descendably on the body; a split base fixed to the body; a disc spring pressing and urging the actuator box downward to bring the metal diaphragm into contact with the valve seat; and a piezoelectric actuator housed inside the actuator box and that extends upward with application of voltage to press the actuator box upward against the elastic force of the disc spring, and a precompression mechanism, for applying a compression force constantly to piezoelectric elements in the piezoelectric actuator, provided between the split base and the piezoelectric actuator.

Abstract: A pneumatic pressure regulating valve, the opening of which can be automatically changed in a pressure-related manner, including a control diaphragm that is subjected to a reference pressure, to the gas pressure as well as to a governor spring, wherein a change in the differential pressure causes an adjustment of the control diaphragm and the latter itself or a closing element actuated by it changes the opening through an outflow cross-section, and wherein a structure that is arranged adjacent to the outflow cross-section on the diaphragm side forms a stop for the control diaphragm or for the closing element in the closed position of said control diaphragm.

Abstract: A pneumatic valve actuator for moving the valve stem of a control valve comprises an upper casing and a lower casing each having flanges, a diaphragm plate operatively coupled to the valve stem, a spring arranged to bias the diaphragm plate in a first direction, a diaphragm movable in conjunction movement of the diaphragm plate, an air inlet defined in the casing and arranged for attachment to an air supply source to bias the diaphragm plate in a second direction, and a ring disposed between the upper flange and the lower flange and positioned to engage the outer portion of the diaphragm. The ring includes a protrusion positioned to engage a surface of the outer portion of the diaphragm.

Abstract: Methods and apparatus to couple actuator stems and rod end bearings are described. An example apparatus includes a bearing having a body and a portion extending from the body in which the portion includes an internally threaded bore. An actuator stem has a first end that includes an internally threaded bore. An externally threaded stud threadably engages the bores of the rod end bearing and the actuator stem to couple the rod end bearing and the actuator stem.

Abstract: A pneumatic pressure regulating valve, the opening of which can be automatically changed in a pressure-related manner, including a control diaphragm that is subjected to a reference pressure, to the gas pressure as well as to a governor spring, wherein a change in the differential pressure causes an adjustment of the control diaphragm and the latter itself or a closing element actuated by it changes the opening through an outflow cross-section, and wherein a structure that is arranged adjacent to the outflow cross-section on the diaphragm side forms a stop for the control diaphragm or for the closing element in the closed position of said control diaphragm.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A piston (124) is in a cylinder (128) and mechanically coupled to the valve element. A control valve (40; 42) is coupled to a headspace (138) of the cylinder to selectively expose the headspace to a fluid source (144), pressure of fluid in the headspace producing a force on the piston and valve element in a direction from the second condition toward the first condition. The compressor includes means (190, 192; 210; 220) for relieving excess pressure in the headspace.

Abstract: An adjustment valve includes a first diaphragm integrally formed from an attachment section engaged with and fixed to the bottom of a rod, a joining section to which a valve body is fixed, a thin film section radially extending from a shoulder section, a thick wall section continuous with the thin film section, and a seal section provided at the peripheral edge of the thick wall section. The second diaphragm has a central hole, and includes an integrally formed thin film section radially extending from a thick wall section at the center hole, and a seal section is provided at the peripheral edge thereof. A diaphragm hold-down member penetrates the central hole at the shoulder section of the rod, causing the second diaphragm to be sandwiched and fixed. The rod is disposed with play in the through-hole in the bottom of the cylinder, and is supported by a spring engaged between a step section of the cylinder and the bottom surface of the shoulder in a state such that radial movement is prevented.

Abstract: A compressor apparatus (20) has a housing (22) having first (53) and second (58) ports along a flow path. One or more working elements (26; 28) cooperate with the housing (22) to define a compression path between suction (60) and discharge (62) locations along the flow path. An unloading valve (100) has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. Means (120, 160) bias the valve element toward a third condition intermediate the first and second conditions.

Abstract: An on-board oxygen generating system is provided, which includes an air supply duct, a breathing gas duct, and an oxygen generator fluidly coupled between the air supply duct and the breathing gas duct. The oxygen generator is configured to enrich the oxygen content of air flowing from the air supply duct to the breathing gas duct. A drain valve assembly is fluidly coupled to the air supply duct and configured to move between: (i) an open position wherein condensation may drain from the air supply duct, and (ii) a closed position.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A first surface (200) of the valve element (102) is in sliding engagement with a second surface (202) of the housing (22) during movement between the first and second conditions. The compressor includes means for lubricating the first (200) and second (202) surfaces.

Abstract: A membrane air dryer includes a proportioning valve for providing sweep air to the dryer. The valve may be located in an easily accessible location and may be oriented so that the movable valve element extends transverse to the length of the shell. The valve may be configured to allow air to flow back from the delivery port to the fibers during a compressor unload cycle to maintain pressure on the fibers, while blocking flow of air from the delivery port to the sweep chamber.

Abstract: A diaphragm valve having an inlet sleeve and an outlet sleeve that converge to a fluid flow chamber contains a valve seat engaged by an elastic diaphragm that is composed of a peripheral flange connected to a central dome-shaped part. The cross section of the two sleeves near the valve seat is flattened in the direction of flow and elongated in the direction transverse thereto, so to form a substantially elliptical port, corresponding to the dome of the diaphragm, which has the shape of a sector of an ellipsoid.

Abstract: A positioner for a control valve assembly is disclosed wherein the positioner is mounted internally to thus protect the positioner from damage stemming from environmental, impact, or other outside influences. Accordingly, not only can the position of the valve be accurately measured, but the sensing hardware is less subjected to damage or other drawbacks associated with exposure.

Abstract: The invention relates to a device for at least intermittently generating an overpressure in a system S in relation to an ambient pressure U, with a pump P that has a pressure side 20 and an intake side 10, where during the generation of an overpressure, the pressure side 20 is connected to the system S and the intake side 10 is connected to the ambient pressure by means of at least one first valve MV1, in particular a solenoid valve. According to the invention, means are provided, which can provide an additional cross section for the intake volume flow during the generation of an overpressure. The invention also relates to a valve, which is particularly provided for use with the device according to the invention.

Abstract: The present invention relates to fluid control valves. The invention provides an improved diaphragm useful for a large hydraulically-operated valve or pressure regulating valve of the type used in pipelines to transport water, oil, gas, acids, alkalis and other fluids. The diaphragm being provided with an upper face arranged to be exposed to a control hydraulic pressure and a lower face arranged to selectively seal and open a passage between a valve inlet and a valve outlet, ribs on said upper face urging the diaphragm towards a sealing position. The diaphragm being characterized by the addition of an elastomer ring element disposed adjacent to the upper face and adjacent to the largest diameter of the diaphragm exposed inside a valve to which it may be assembled, an upper face of the flexible ring element being in pressure contact with a portion of the rigid body of the valve.

Abstract: A valve actuator apparatus and method comprises an operator housing secured to a bonnet assembly. The bonnet assembly is secured to the valve body, and includes a bonnet stem movably within a bonnet housing for moving a gate within the valve body to open and close the valve. A downstop member is fixably secured to the bonnet stem and engages removable stem spacers which are added or removed to obtain a selected bonnet stem drift setting. The operator housing connects to a base ring that surrounds the bonnet housing and rotates to allow positioning of a fluid port in the operator housing. The operator housing may removed and replaced without altering the bonnet stem drift adjustment. A top shaft extends from the operator housing and rotates with respect to the bonnet stem to prevent torque transmission from the top shaft to the bonnet stem. A replaceable sealing cartridge sealingly supports the top shaft for axial movement within the operator housing.

Abstract: The present invention relates to a valve assembly for use in below freezing conditions which includes a valve housing with a connection to a supply of fluid, and a primary chamber, and a secondary chamber, and a flexible diaphragm, and an equalisation port, and a safety port the valve assembly characterised in that has a safety port associated with the secondary chamber wherein the safety port is configured to have a lower flow-rate than that through the equalisation port.

Abstract: A valve actuator apparatus and method comprises an operator housing secured to a bonnet assembly. The bonnet assembly is secured to the valve body, and includes a bonnet stem movably within a bonnet housing for moving a gate within the valve body to open and close the valve. A downstop member is fixably secured to the bonnet stem and engages removable stem spacers which are added or removed to obtain a selected bonnet stem drift setting. The operator housing connects to a base ring that surrounds the bonnet housing and rotates to allow positioning of a fluid port in the operator housing. The operator housing may removed and replaced without altering the bonnet stem drift adjustment. A top shaft extends from the operator housing and rotates with respect to the bonnet stem to prevent torque transmission from the top shaft to the bonnet stem. A replaceable sealing cartridge sealingly supports the top shaft for axial movement within the operator housing.

Abstract: A Valve actuator with integral amplifying means having multiple linkage arrangements able to amplify the force generated by an air signal acting on a flexible diaphragm, and to transmit this force amplified on to a lower compression spring and ultimately on to a sliding actuator stem.

Abstract: A drive for a control valve has a drive force unit, a yoke for connecting to a valve in a fixed manner, a drive spindle for transmitting the movement of the drive force unit to the valve and a sensor unit for detecting the position of the valve. The sensor unit includes a magnetic track with a reoccurring structure which is integrated into the drive spindle, a sensor which is connected to the yoke of the drive in the vicinity of the magnetic track, which is suitable for detecting the changing magnetic field lines and at least one permanent magnet in the area of the magnetic track and the sensor, whose magnetic field lines penetrate both the magnetic track and the sensor.

Abstract: Disclosed is a pneumatic actuator which includes a housing comprised of two halves and having at least two passages defined therethrough, including a “loop” groove defined in an inner peripheral wall of the housing into which a seal member is inserted. A rotary piston is rotatably received in the housing. The piston has a top and a bottom with an intermediate wall connected there between, and an actuating shaft extending through the housing, which is rotated by movement of the rotary piston. The seal member extends into the housing and is in contact with the top and bottom of the rotary piston all the times. The rotary piston moves free of contact with the interior surface of the housing and this one seal member provides a seal for the joint created between the halves of the housing, the chambers of the housing as well as the actuating shaft. Movement of the piston is effected by air pressure and return motion of the piston can be air driven or spring assisted.