| 摘要 |
Quick drop valves are usable in hydraulic circuits in which fluid is expelled from a hydraulic cylinder due to gravity force acting on a load connected to the hydraulic cylinder. The present quick drop valve has a sleeve carried by a valve member for establishing an orifice through which the fluid expelled from the hydraulic cylinder passes. When the flow rate of the expelled fluid exceeds a predetermined flow rate, a differential pressure generated by the orifice causes the valve member to start moving toward a quick drop position. In so doing, the sleeve quickly establishes a more restrictive orifice to immediately generate a higher differential pressure to cause the valve member to quickly move to the quick drop position. The more restrictive orifice also causes a greater amount of the expelled fluid to be returned by the valve member to the expanding ends of the hydraulic cylinders, yet still allows sufficient flow therethrough so that the quick drop action can be stopped if so desired. The sleeve also functions similar to a check valve and moves to a position permitting substantially unrestricted fluid flow through the quick drop valve when the fluid is being directed to the hydraulic cylinder to raise the load. An actuating chamber is defined in the valve member and is subjected to pressurized fluid generated in the circuit to hold the valve member in a blocking position when the blade is forced into the ground. |
