COMPONENT OPERTATION / Control Valve ANTI-DRIFT VALVE The anti-drift valve is provided in the circuits of boom cylinder bottom side and arm cylinder rod side, and prevents the cylinders from drifting. NOTE: Both boom and arm anti-drift valves are identical in construction. Therefore, the boom anti-drift valve is explained as an example. Holding Operation 1. Pressure oil from the boom cylinder bottom side flows to the spring (5) chamber and the spring (4) chamber in switch valve (3) through orifice (7) in check valve (6). 2. When the control lever in neutral (boom 1 spool (8): neutral), pressure oil from port 4Pc3 is blocked so that switch valve (3) in the anti-drift valve is not shifted. 3.
Consequently, as check valve (6) is pushed by force of spring (5) and pressure of the spring (5) chamber, and the return circuit is blocked, drift amount of the cylinder is reduced. From Port 4Pc3 (Pressure Oil from Pilot Pump) Boom 1 Spool Anti-Drift Valve (Switch Valve) Boom Cylinder T450-03-03-037 Anti-Drift Valve (Check Valve) T3-3-28