without and with pre-release
Pilot-operated check valves are spring-loaded poppet valves with free flow from B to A and blocked flow in the opposite direction that can be "unblocked" by pressurizing the control port Z. The minimum pressure required for unblocking depends on the height of the counter pressure at port A (see diagram).
In the pilot-operated version fist a smaller poppet valve located in the main valve piston is opened.
This offers the following advantages:
Blocking of leakage-free cylinders combined with non leakage-free directional control valves and pressure maintenance on uncoupled parts of the installation (clamping pallets).
In the case of swing clamps and pull-type cylinders, a dangerous pressure intensification can occur during unclamping, if the release pressure is not sufficient for opening.
Therefore pilot-operated check valves must be used, that require a substantially lower opening pressure.
pipe-thread type C2.9511
manifold-mounting type C2.9512