COMPONENT OPERTATION / Signal Control Valve SHOCKLESS VALVE The shockless valve is provided in the boom raise circuit and functions when returning the boom raise control lever suddenly. During Boom Raising Operation 1. Boom raise pilot pressure is routed into port A and acts on the spool. 2. Immediately after operation is started, low pilot pressure flows into the spring B chamber through clearance C between spool and housing. At the same time, pilot pressure flows to port 1 through inner passage 2. 3. When pilot pressure increases, pressure in the spring B chamber increases, and the spool pushes spring A and moves to the left. 4.
As the spool is moved, port A is connected to port 1 and pressure in port 1 increase, so that the spool in control valve is moved. Port A Spool Clearance C T1V1-03-06-003 Port 1 Port A Spring B T1V1-03-06-002 Port 1 T3-6-10 ring A Spool S