Actuator systems and methods of operation are disclosed. The systems include a hydraulic actuator having a primary piston having a piston head arranged within a housing defining retract and extend chambers on opposite sides of the piston head. A control element is configured to control a supply of pressure to each of the retract and extend chambers. An actuator valve is coupled to the housing and includes a secondary piston that is biased into the retract chamber in an open flow state and when the primary piston is in a fully retracted state the piston head urges the secondary piston into a closed flow state. The actuator valve defines a flow chamber where, in an open flow state, fluid can be passed through the flow chamber and in a closed flow state the fluid is prevented from passing through the flow chamber.

A pneumatic or hydraulic mechanism has a housing defining a piston chamber and having a fluid inlet port. A piston is slidable in the piston chamber. The piston partitions the piston chamber into a front chamber and a rear chamber. The piston has one or more passages for fluid communication between the rear chamber and the front chamber, the one or more passages being sealed by a sealing mechanism. The sealing mechanism has a sealing state in which the sealing mechanism substantially inhibits fluid communication between the rear chamber and the front chamber, and a non-sealing state in which the sealing mechanism allows fluid communication between the rear chamber and the front chamber. The piston is slidable between a first position and a second position. When the piston is positioned in the first position, the sealing mechanism is in the sealing state. Upon supply of a fluid to the inlet port, the fluid urges the piston to its second position and then causes the sealing mechanism to change to the non-sealing state until the pressure in the rear chamber and the front chamber equalises, allowing the sealing mechanism to return to the sealing state. Upon removal of fluid from the rear chamber, the fluid in the front chamber urges the piston to return to its first position.

A self-setting valve assembly for a power steering gear assembly includes a plug, a first plunger, a second plunger, and a biasing member. The plug extends between a first end and a second end. The plug defines a cavity that is disposed between the first end and the second end, a first bore that extends from the first end to the cavity, and a second bore that extends from the second end to the cavity. The first plunger has a first head that is disposed within the cavity and a first stem that extends from the first head through the first bore. The second plunger has a second head that is disposed within the cavity and a second stem that extends from the first head through the second bore. The biasing member is disposed within the bore and extending between the first head and the second head.

When pressurized fluid is not supplied into or discharged from the first channel 28a of the piston rod 28, that is, when the first channel 28a is isolated from the outside, the cylinder tube 22 is in a stopped state. At this time, fluid inside the first cylinder chamber 36a is compressed, and the pressure is increased accordingly to match the sum of the weights of the cylinder tube 22, the table 18, and the workpiece W.

The claimed invention is an end-of-stroke recirculation system for use with a hydraulic cylinder. Generally speaking, the fluid in a hydraulic cylinder remains trapped on one side of the piston and is unable to recirculate. The claimed invention provides a bypass that allows for hydraulic fluid to circulate through a cylinder when the hydraulic cylinder is at either end or both ends of its stroke.

A technique facilitates rapid transitioning of a valve, e.g. a gate valve. According to an embodiment, a system comprises a valve actuator constructed for coupling with a valve to actuate the valve between closed and open positions. Hydraulic actuation fluid may be supplied to the valve actuator under pressure via a hydraulic supply system to enable selective shifting of the valve actuator, and thus the valve, from a closed position to an open position. The system also comprises a dump tank coupled to the valve actuator in a manner to receive hydraulic fluid. In a rapid valve actuation operation, e.g. closing operation, the dump tank receives hydraulic fluid from the valve actuator rather than returning the hydraulic fluid to the hydraulic supply system. This, in turn, enables rapid shifting of the valve actuator and thus rapid shifting of the valve.

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.

A hydraulic actuator includes a piston and a cylinder. The piston is axially movable within the cylinder. A stroke end damping valve is provided in a hydraulic fluid flow passage of the actuator and adjacent an end of the cylinder. The stroke end damping valve comprises a damping orifice and a valve element for selectively varying the area of the damping orifice and thereby changing the damping provided by the orifice. The valve element projects from a wall of the cylinder into the cylinder and is engageable by the piston as the piston moves towards the end of the cylinder. This reduces the area of the damping orifice and thereby increases the damping effect on the piston towards the end of its stroke in the cylinder.

A system for providing pressure/load control at an end stroke stop is provided. The system includes an actuator housing having an end stroke stop and a first actuator housing side, an actuator piston provided in the actuator housing, wherein the actuator piston is movable along a longitudinal axis (A), the actuator piston having a first piston portion perpendicular to the longitudinal axis (A), and means for regulating the pressure/load control at the end stroke stop provided in the first piston portion, wherein the means for regulating the pressure/load control at the end stroke stop is configured to move from a closed position to an open position when in contact with the first actuator housing side.

A hydraulic actuator includes a piston and a cylinder. The piston is axially movable within the cylinder. A stroke end damping valve is provided in a hydraulic fluid flow passage of the actuator and adjacent an end of the cylinder. The stroke end damping valve comprises a damping orifice and a valve element for selectively varying the area of the damping orifice and thereby changing the damping provided by the orifice. The valve element projects from a wall of the cylinder into the cylinder and is engageable by the piston as the piston moves towards the end of the cylinder. This reduces the area of the damping orifice and thereby increases the damping effect on the piston towards the end of its stroke in the cylinder.