A center biased actuator having an outer cylinder, a slave cylinder linearly transposed within the outer cylinder, a rod assembly with a piston linearly transposed within the slave cylinder and a rod extending from the outer cylinder, one or more first dynamic seals arranged to act on a sidewall of the rod to inhibit hydraulic fluid leaking from the outer cylinder, one or more second dynamic seals arranged to act on a sidewall of the slave cylinder or an inner surface of the outer cylinder to inhibit hydraulic fluid leaking from the outer cylinder, and a gas chamber comprising a sealed expandable chamber containing gas. The expandable chamber is arranged to act on hydraulic fluid within the center biased actuator to bias the center biased actuator to assume an intermediate condition which lies between a compressed condition and an extended condition.

A pneumatic actuator and control valve assembly has a housing with a control cavity for a control valve and an actuator cavity for an actuator piston and rod assembly. The control cavity and actuator cavity both have an elongated shape and are substantially parallel to each other. The control cavity has a supply port and first and second control valve outlet ports and at least one vent port with the control valve being movable through the control cavity for controlling communication between the supply port and the first and second outlet ports. The actuator cavity has first and second ports at the retracted and extended ends for shuttling the piston and within the actuator cavity between a retracted and extended end position. The housing has a first inlet and second inlet for passage of pressurized fluid to and from the housing,

A modular actuator assembly which can be used for partial stroke testing of a valve, the assembly having a force module and a tandem piston module. The force module has a primary piston and piston rod interconnected to a shaft which is movably mounted therein. The tandem piston module is connected to the force module and has a tandem piston and piston rod. An indicator plate is connected to the piston rod and is selectively positionable on the tandem piston rod. The tandem piston rod extends into the force module and acts as a pneumatically engaged hard stop for preventing spurious travel of the primary piston and hence spurious valve travel.

An actuator assembly comprises a housing having a piston at least partially disposed therein. The actuator assembly includes at least one biasing mechanism disposed within the housing to selectively position the piston between a first position, a second position, and a third position located between the first and second positions.

The invention relates to a compressed-air device for controlling valves comprising, in a longitudinal direction, a first vane-type rotary cylinder (1) having a front face (2) as well as a back face (4), said front face (2) being provided with a rotatable head (3), and a second vane-type rotary cylinder (10) having a front face (11) and a back face, said first (1) and second (10) cylinders each being supplied with compressed air by means of a compressed air valve connected to two ports (7, 8; 14, 15) on each of said first and second cylinders.

A variable compression ratio apparatus may include: a connecting rod having an end connected with a crank pin of a crank shaft; a plunger housing formed at the other end of the connecting rod, the plunger housing having a space to which a plunger is inserted. In particular, the plunger moves upwardly and downwardly, and an outer circumference surface of the plunger contacts an inner circumference surface of the plunger housing. The apparatus further includes a protrusion protruded from the plunger to the plunger housing and connected with a piston, and a hydraulic pressure control valve for supplying hydraulic pressure to the space and moving the plunger by supplying hydraulic pressure.

Disclosed is a pin lifting device for moving and positioning a substrate. Also, a pneumatic drive cylinder is provided having a cylindrical housing enclosing a first internal volume and a first piston assembly, having a first piston and a first piston rod. The first piston assembly can be moved into a fitting position by pressurization of the first internal volume. The device has at least one supporting pin connected to the first piston rod. The drive cylinder has a second piston assembly, which has a second piston and a second piston rod. The second piston assembly is arranged for motion coaxial to the first piston assembly. An end surface of the second piston rod faces the first piston. The first and second piston assemblies are arranged so the first piston and the second piston rod have no contact in the fitting position.

A piston-cylinder assembly (1) has a cylindrical housing (3), with a main piston (2) and at least one trailing piston (11, 12). The trailing piston (11, 12) is axially guided on a cylindrical outer lateral face (38) of the main piston (2). The trailing piston (11, 12) has a thrust portion (13, 14) at one end near a piston web on the main piston, The thrust portion extends axially inward toward the piston web (10) A travel limiter (28) on the cylindrical housing limits a travel range of the trailing piston (11, 12) Under pressure, the trailing piston (11, 12) follows the main piston (2) until the trailing piston (11, 12) hits the travel limiter (28). The thrust portion (13, 14) of the trailing piston (11, 12) is shaped to fit into an associated recess (30, 31) in the piston web with a positive lock.

An actuator assembly comprises a housing having a piston at least partially disposed therein. The actuator assembly includes at least one biasing mechanism disposed within the housing to selectively position the piston between a first position, a second position, and a third position located between the first and second positions.

A hydraulic system is described, in particular for a motor vehicle transmission, with an actuator, a valve, a pressure supply line and a tank line. The actuator may have a first pressure chamber and a second pressure chamber, which can have pressure applied for actuation of the actuator, wherein the pressure chambers, the pressure supply line and the tank line are each connected to a port (A, B, P, T) of the valve. The valve may have several different switching positions, in which the pressure chambers with the pressure supply line or the tank line are selectively connected to each other or shut off from each other.