Vektek currently offers three-position valves with two different center positions, “Closed Center” and “P Blocked”: 3 X 4 “closed” center valve blocks all internal fluid paths (“P”, “T”, “A”, &”B”) so that no flow is permitted from either the pump or the actuator when in the center position.
When the inlet flow is stopped the valve will close and block the passage preventing the return, or backward flow of fluid. This type of valve requires a separate control valve, path, or device to release the downstream fluid blocked by the valve. Pilot operated check valve is a valve that combines the function of a check valve as well as an internal pilot piston to unseat the check valve.
When pressure is applied to the pilot port, it will open or “unseat” the check valve, allowing return flow through the valve. The pilot operated valve is commonly used as an “A” or “A-B” check valve to provide various control of the flow in the actuator circuit. Sequence valve is a manually adjustable, normally closed device that prevents the flow of fluid in the hydraulic circuit until a pre-set pressure setting has been achieved.
The solenoid version of this configuration has a mechanical spring to return the operator to the center position when there is no electrical signal. 3 X 4 “P” blocked center valve blocks the fluid path from the pump (“P”), but allows flow from both sides of the actuator (“A” & “B”) to return to tank (“T”) when in the center position.
SPECIAL FUNCTION VALVES Check valve is a device that will allow flow through the valve in one direction only. The solenoid version of this configuration has a mechanical spring to return the operator to the center position when there is no electrical signal.
Once the pre-set pressure has been achieved, the valve will open and allow fluid to flow through the valve to an actuator. This allows the devices in one branch of a circuit to be actuated at a different pressure setting than items in another branch of the same circuit. This device does not regulate pressure on an actuator, therefore once activated the down stream pressure will equalize with that of the main supply pressure.
7 of 40
Hydraulic Clamping Fundamentals Aug 09 Rev - D
Made with FlippingBook - Online Brochure Maker