The subject matter of this specification can be embodied in, among other things, a method that includes actuating a closure member at a predetermined first velocity a predetermined first number of cycles between a first configuration and a second configuration, actuating the closure member at a predetermined second velocity a predetermined second number of cycles between the first and the second configuration, actuating the closure member at a predetermined third velocity a predetermined third number of cycles and the second configuration, actuating the closure member at a predetermined fourth velocity a predetermined fourth number of cycles and the second configuration, and actuating the closure member to the second configuration at a predetermined fifth velocity for a predetermined flushing period.

A pneumatic trip valve that may include a valve structure, a switch plate air path and an internal check valve. In various aspects, the pneumatic trip valve may be connected to a valve positioner, an actuator, or a combination thereof to control the operation of a fluid process control valve. In operation, the Pneumatic trip valve acts to put the actuator in a preset fail-safe position when the actuator loses sufficient pressure or communication from a main air supply, stored pressurized air from an actuator air reservoir, and/or an external air reservoir.

A system for charging and discharging at least one hydraulic accumulator (10), which can be connected to a valve control device (12), wherein the valve control device (12) comprises at least one logic valve (14), is characterized in that a shuttle valve (16) and a switching valve (18) are also provided and the valves (14, 16, 18) are interconnected such that the hydraulically actuatable switching valve (18) compares the accumulator pressure (p.sub.A) to a minimum accumulator pressure (p.sub.A0) that can be adjusted via the control pressure setting of this switching valve (18).

The disclosure relates to an electro-hydraulic control system for directing fluid to at least one hydraulic actuator, the system comprising at least one electronic controller; first and second pilot valves being electrically connected to the at least one electronic controller which is arranged to control the operation of the first and second pilot valves, third and fourth pilot valves being electrically connected to the at least one electronic controller which is arranged to control operation of the third and fourth pilot valves. A pilot operated main valve is configured to control fluid flow to at least one hydraulic actuator. Each of the first and second pilot valves and the third and fourth pilot valves is a fail-safe pilot valve arranged to drain a regulated outlet port to a low pressure reservoir if a spool of the fail-safe pilot valve becomes stuck in an open state.

An example valve includes: (i) a valve body comprising a supply port and an operating port; (ii) a sleeve comprising a first opening fluidly coupled to the supply port, a second opening fluidly coupled to the operating port, and a seat; (in) a spool configured to move axially within the sleeve, wherein the spool is configured to he seated on the seat of the sleeve when the valve is unactuated, and wherein when the valve is actuated, the spool moves such that a gap is formed at the seat; and (iv) a flow restriction disposed downstream of the gap, wherein when the valve is actuated, fluid is allowed to flow from the supply port through the first opening and the gap and through die flow′ restriction prior to flowing through the second opening to the operating port, such that the flow restriction generates an increased pressure level at the gap.

The present disclosure relates to a hydraulic valve arrangement comprising a first pilot operated proportional directional control valve having a first valve member that is displaceable in a first and a second axial direction for controlling direction of supply and discharge of hydraulic fluid to and from a hydraulic actuator, a first proportional electro-hydraulic control valve for controlling displacement of the first valve member in the first axial direction, a second proportional electro-hydraulic control valve for controlling displacement of the first valve member in the second axial direction, and a second pilot operated proportional control valve having a second valve member configured to be controlled by the first and second proportional electro-hydraulic control valves via a shuttle valve arrangement. Individual meter-in and meter-out control of the hydraulic actuator is providable by having the second pilot operated proportional control valve configured to operate as a meter-in valve of the hydraulic actuator and the first pilot operated proportional directional control valve configured to operate as a meter-out valve of the hydraulic actuator, or by having the first pilot operated proportional directional control valve configured to operate as a meter-in valve of the hydraulic actuator and the second pilot operated proportional control valve configured to operate as a meter-out valve of the hydraulic actuator. The present disclosure also relates to a vehicle comprising a hydraulic actuator and a hydraulic valve arrangement for controlling the motion of the hydraulic actuator.

The subject matter of this specification can be embodied in, among other things, an electrohydraulic positioning control system that includes a shuttle valve configured to direct fluid flow between a selectable one of a first fluid port and a second fluid port, and a fluid outlet configured to be fluidically connected to a fluid actuator, a first servo valve controllable to selectably permit and block flow between the first fluid port, a fluid source, and a fluid drain, a second servo valve controllable to selectably permit and block flow between the second fluid port, the fluid source, and the fluid drain, a first servo controller configured to provide a first health signal and control the first servo valve based on a second health signal, and a second servo controller configured to provide the second health signal and control the second servo valve based on the first health signal.

The subject matter of this specification can be embodied in, among other things, a method that includes actuating a closure member at a predetermined first velocity a predetermined first number of cycles between a first configuration and a second configuration, actuating the closure member at a predetermined second velocity a predetermined second number of cycles between the first and the second configuration, actuating the closure member at a predetermined third velocity a predetermined third number of cycles and the second configuration, actuating the closure member at a predetermined fourth velocity a predetermined fourth number of cycles and the second configuration, and actuating the closure member to the second configuration at a predetermined fifth velocity for a predetermined flushing period.

The present invention provides a switching valve comprising: a housing including a first port, a second port, and a third port; a valve element configured to be movable in the housing so as to selectively allow one of the first port and the second port to communicate with the third port in accordance with a pressure difference between the first port and the second port; and a pressing member configured to press the valve element toward a side of the first port.

An air cylinder in which a flow rate controller is built in, has a head cover and a rod cover. A pilot air adjustment unit guides exhaust air to a switch valve of the flow rate controller as pilot air, and the switch valve is switched by an increase in the pressure of the pilot air.