A pneumatic cylinder with a piston rod movable to fully extended, intermediate and fully retracted positions. The cylinder may have a first head engaging one end of a first tube with a first piston slidably received therein, an intermediate connector engaging the other end of the first tube and one end of a second tube with a second piston slidably received therein, and a second head engaging the other end of the second tube. The piston rod may be attached to the second piston for movement therewith and extend through the intermediate connector, first piston, first tube, and the first head to the exterior thereof.

A fluid actuator arrangement comprises a first cylinder housing including a first head member and a second head member; a first piston body is slidable arranged in said first cylinder housing; the first piston body divides the first cylinder housing interior into a first cylinder chamber and a second cylinder chamber, at least the first cylinder chamber is coupled to a fluid supply. The first piston body exhibits a first through-bore and a second through-bore that extend through the first piston body in an axial direction; a first piston rod is arranged slidable in the first through-bore and a second piston rod is arranged slidable in the second through-bore; and the first through-bore comprises a first engagement and disengagement device and the second through-bore comprises a second engagement and disengagement device, which are arranged for providing individual engagement or disengagement to or from the respective first and second piston rod.

A proportional control fluid actuator that is used as a positioning device in applications such as a hydraulic directional control valve. The activating device has a cylinder body attachable to a valve body and has a bore carrying a piston that is coaxially secured to an end of a valve spool. The device is provided with spaced openings in the cylinder body that communicate with the bore therein to introduce fluid to act on opposite sides of the piston. Factory pre-compressed spring means are provided for normally urging the piston and spool to a center position. Since the areas of the fluid pressure applied on both sides of the piston are different (due to a spool on one side of the piston), two pre-compressed springs are used to compensate the area difference to achieve a proportional movement of the spool.

A fluid actuator arrangement comprises a first cylinder housing including a first head member and a second head member; a first piston body is slidable arranged in said first cylinder housing; the first piston body divides the first cylinder housing interior into a first cylinder chamber and a second cylinder chamber, at least the first cylinder chamber is coupled to a fluid supply. The first piston body exhibits a first through-bore and a second through-bore that extend through the first piston body in an axial direction; a first piston rod is arranged slidable in the first through-bore and a second piston rod is arranged slidable in the second through-bore; and the first through-bore comprises a first engagement and disengagement device and the second through-bore comprises a second engagement and disengagement device, which are arranged for providing individual engagement or disengagement to or from the respective first and second piston rod.

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.

An actuator unit includes two chambers defined in the cylinder; a supply passage allowing a working fluid discharged from the pump to be supplied to the two chambers; a discharge passage allowing the two chambers to communicate with the tank; a direction control valve configured to selectively communicate each of the two chambers with one of the pump and the tank; a control passage that branches from the supply passage on a side of the pump rather than the direction control valve so as to communicate the pump with the tank; a variable relief valve provided on the control passage, the variable relief valve opening so as to allow the working fluid to flow from the supply passage toward the tank when a pressure in the supply passage reaches the valve opening pressure; and a center passage that communicates the tank with an interior of the cylinder.

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.

An actuator unit includes a rod side chamber and a piston side chamber defined in the cylinder by a piston; a tank; a direction control valve configured to allow a working fluid discharged from the pump to be supplied selectively to the rod side chamber and the piston side chamber; a first control passage that communicates the rod side chamber with the tank; a second control passage that communicates the piston side chamber with the tank; a first variable relief valve provided on the first control passage, the first variable relief valve being configured to have a varied valve opening pressure; a second variable relief valve provided on the second control passage, the second variable relief valve configured to have a varied valve opening pressure; and a center passage that communicates the tank with the interior of the cylinder.

A three-position control device includes a cylinder device, a fluid control unit, and a displacement restriction device. The cylinder device displaces a piston to each of a retracted position, an intermediate position, and an advanced position. The cylinder device has a first fluid chamber for retraction and a second fluid chamber for advance. A fluid control unit switches an advanced/retracted position of the piston. A second working pressure during displacement from an intermediate position to the advanced position is set to be greater than a first working pressure during displacement from the retracted position to the intermediate position. The displacement restriction device has a load receiving portion and a biasing means. A biasing force of the biasing means is set to be greater than a thrust caused by the first working pressure and smaller than a thrust caused by the second working pressure.

A three-position control device includes a cylinder device, a fluid control unit, and a displacement restriction device. The cylinder device displaces a piston to each of a retracted position, an intermediate position, and an advanced position. The cylinder device has a first fluid chamber for retraction and a second fluid chamber for advance. A fluid control unit switches an advanced/retracted position of the piston. A second working pressure during displacement from an intermediate position to the advanced position is set to be greater than a first working pressure during displacement from the retracted position to the intermediate position. The displacement restriction device has a load receiving portion and a biasing means. A biasing force of the biasing means is set to be greater than a thrust caused by the first working pressure and smaller than a thrust caused by the second working pressure.