BLADE AS-WIPER 3151316 - Caterpillar

Illustration 1 g01147924
(1) Tilt pilot control valve. (2) Lift pilot control valve. (3) Selector and pressure control valve. (4) Float valve. (5) Selector valve. (6) Right main control valve. (7) Left main control valve. (8) Left tilt cylinder. (9) Right tilt cylinder. (10) Pilot relief valve. (11) Implement pilot filter. (12) Pilot pump and pump for the implement oil cooler. (13) Lift cylinder. (14) Hydraulic tank (Implement).The pilot circuit sends low pressure oil in order to operate the main control valves.When the engine is running, oil flows from hydraulic tank (14) to pilot pump (12). The pilot pump is a gear pump.Oil flows from the pilot pump through pilot filter (11). The pilot filter has a bypass valve. If the pilot filter becomes restricted, the bypass valve will open and the oil will bypass the filter.The oil then flows to pilot relief valve (10). The relief valve maintains the pilot system pressure at 2400 40 kPa (350 6 psi). When the oil rises above the setting of the pilot relief valve, the pilot relief valve will open. Oil will flow through the pilot relief valve and to the cooling circuit.Oil flows through a check valve and to pilot control valves (1) and (2). The pilot control valves are closed center valves. When the controls of the pilot control valves are moved, pilot oil flows to the main control valve.Selector valves (5) will allow oil to flow through the pilot circuit when pilot control valves (1) and (2) are in the HOLD position. This will help keep the pilot oil warm when the pilot control valves are in the HOLD position.Note: The functions of the tilt pilot control valve and the lift pilot control valve are similar. The function of the lift pilot control valve will be explained.The lift pilot control valve is a closed center valve that has four positions. The four positions are RAISE, HOLD, LOWER, and FLOAT.Lift Pilot Control Valve in HOLD
When lift pilot control valve (2) is in the HOLD position, pilot oil is blocked since the valve is a closed center valve.Lift Pilot Control Valve in RAISE
When lift pilot control valve (2) is moved to the RAISE position, oil flows through the oil lines to the ends of main control valves (6) and (7). This causes the spools in the main control valves to move. Movement of the spools opens passages that will allow high pressure oil to flow to the head ends of the lift cylinders.A detent in the pilot valve allows the control lever to remain in the RAISE position until the operator moves the lever to the HOLD position or until the lift kickout automatically moves the control lever into the HOLD position.Lift Pilot Control Valve in LOWER
When lift pilot control valve (2) is moved to the LOWER position, oil flows through the oil lines to the opposite ends of main control valves (6) and (7) for the lift circuit. This causes the spools in the main control valve to