PLATE 6E5296 - Caterpillar

Illustration 1 g00923903
Drift Reduction Valve (1) Relief valve (5) Manual lowering valve
Illustration 2 g02406363
Drift reduction valve - neutral state (A) Return to tank (B) Pilot pressure - Stick in and boom lower (C) To and from rod end of stick cylinder (D) To and from control valve (1) Relief valve (2) Resolver check valve (3) Load check valve (4) Line from control valve (5) Screw for manual lowering (6) Pilot piston (7) Line from pilot valve (8) Spring chamber (9) Port to cylinder (10) Ball check valves
Illustration 3 g02406663
Drift reduction valve - stick in or lowering of VA boom (A) Return to tank (B) Pilot pressure - Stick in and boom lower (C) To and from rod end of stick cylinder (D) To and from control valve (1) Relief valve (2) Resolver check valve (3) Load check valve (4) Line from control valve (5) Screw for manual lowering (6) Pilot piston (7) Line from pilot valve (8) Spring chamber (9) Port to cylinder (10) Ball check valvesThe drift reduction valves for the head end of the VA boom cylinder and for the stick cylinder rod end are pilot controlled valves. The drift reduction valve will prevent circuit leakage in the main control valve when the implement control valve is in the NEUTRAL position.While implement is in NEUTRAL position and load is raised, the static pressure from the load goes into drift reduction valve at port (9). This forces load check valve (3) against the seat which blocks the return oil flow. Now, the cylinder position will be maintained.Load check valve (3) is opened by pilot controlled pressure (7) to permit oil in spring chamber (8) behind load check valve (3) to return to tank. The pressure in spring chamber (8) decreases and double check valve (10) opens in order to return the cylinder oil to the tank. The effective area at cylinder port at load check valve (3) and static pressure from cylinder is now able to open load check valve (3). The oil is now able to drain through the control valve.When main control valve is activated to STICK OUT position or to VA BOOM RAISE position, the pump pressure is applied against bottom end of load check valve (3). When pump pressure increases beyond the force of spring for load check valve (3), load check valve (3) opens in order to provide pressure to the cylinder.The relief valve in drift reduction valve opens when circuit pressure between cylinder and load check valve (3) exceeds the setting of relief valve (1). When relief valve (1) opens, oil is sent to the opposite end of the cylinder in order to lower the load.The VA boom or the stick can be lowered manually if pilot pressure is lost. Manual lowering screw (5) moves pilot piston (6) downward in order to lower the implement without pilot pressure.