Electro-hydraulic pilot operated relief valve

摘要

Provided is a method of and valve assembly for dumping excess fluid during retraction of a cylinder actuator. The method includes pumping fluid with a pump from a piston side of the cylinder to a rod side of the cylinder; opening a first check valve with relatively high pressure fluid from a downstream side of the pump to allow flow into the rod side of the cylinder; and opening an extend relief valve via a first spool with fluid from the downstream side of the pump to allow excess fluid at an upstream side of the pump to return to a reservoir at relatively low pressure.

主权项

1. A valve assembly for releasing excess fluid to a reservoir at low pressure comprising:
a first spool moveable in a first bore in a valve body having a first side and a second side; a first check valve disposed in the first side of the first bore; an extend relief valve disposed in the second side of the first bore; a second spool moveable in a second bore in the valve body having a first side and a second side; and a second check valve disposed in the second side of the second bore, wherein the first spool is configured to press against and thereby open the first check valve when the first spool is energized by relatively high pressure fluid in the second side of the bore, and is further configured to press against and thereby open the extend relief valve when the first spool is energized by relatively high pressure fluid on the first side, thereby allowing relatively low pressure fluid to flow through the extend relief valve, and wherein the second spool is configured to press against and thereby open the second check valve when the second spool is energized by relatively high pressure fluid in the first side of the second spool.