COMPONENT OPERTATION / Signal Control Valve During Boom Raising Operation (Shockless Op- eration) 1. When the boom is returned suddenly, port A is connected to the hydraulic oil tank through the pilot valve. Return oil from the boom raise spool in the control valve acts on port 1. 2. Pressure oil from port 1 flows to spring chamber A through inner passage 1 and to port A through the spool. Oil in spring chamber B flows to port A through the spool. 3. Pressure acting on the spring A side moves the spool to the right. 4. Therefore, clearance C between spool and hous- ing is closed, so that pressure oil is blocked. 5.
When clearance C is closed, pressure in spring chamber B increases and moves the spool to the left. Then, clearance C is opened again and pressure oil flows to the port A side. 6. As operations in steps (2 to 5) are repeated, pressure oil is gradually returned to port A, so that the control valve spool returns slowly. Spring B T1V1-03-06-002 Port 1 T1V1-03-06-004 T3-6-12 Spring A Spool Port A Port 1 Spring A Spool Spring B Cle Spring A Spool Port A Spring B T1V1-03-06- Spring B Port 1 Port 1