BOLT 1H4215 - Caterpillar

Illustration 1 g00548477
Typical example (1) Shock reducing valveThe shock reducing valves are located in the pilot line supply passage for the following positions: boom raise, boom lower, bucket close, bucket open, forward travel, stick in, stick out, blade/stabilizer up, blade/stabilizer down, VA boom raise and VA boom lower.When the pilot control valve lever is moved, pilot oil is sent from the pilot control valve to the bottom passage of the shock reducing valve. Pilot pressure acts against the surface of the orifice check valve in order to unseat the valve. This will permit oil flow to the control valve spool. Full pilot oil is now allowed to flow to the main control valve to move the control valve spool. When the pilot control valve is placed in the NEUTRAL position, the pilot oil is restricted from returning to the hydraulic tank by the closed orifice check valve. The closed orifice check valve reduces the speed of the main control valve spool as the spool returns to the center position. Slowing the flow of the pilot oil causes the hydraulic control valve spool to return to neutral gradually in order to help to reduce shock loads at the end of the spool travel.