The oil leaves the pump and passes through a check valve. The pilot oil then flows into the selector and pressure control valve. The oil then flows into the pilot control valves. The return oil passes through a filter with a replacement element. The return oil then flows back to the hydraulic oil tank.
Note: On machines with hydraulic over hydraulic brakes, the machine is equipped with a pressure reducing valve. The pilot oil flows into the pressure reducing valve before reaching the selector and pressure control valve. On machines with air over hydraulic brakes, the pilot/brake pump is equipped with a pressure relief valve. The pressure relief valve eliminates the need for a pressure reducing valve.
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| Illustration 1 | g00281022 |
Component Locations (1) Selector and pressure control valve. (A) Pressure tap for the implement pilot circuit. | |
Selector and pressure control valve (1) is located on the right side of the machine under the operator's platform, and behind the secondary steering motor. The valve controls the pressure of the oil in the pilot circuit.
The pressure tap for the implement pilot circuit (A) is located just above pilot selector and pressure control valve (1) .
The pilot control valves are two-spool closed center valves. The two spools are held in a CENTER position by springs when the control levers are in the HOLD position.
When a pilot control valve is moved out of the HOLD position, the pilot control valve directs the flow of pilot oil to a valve spool in the main control valve. This causes the valve spool to shift in order to allow high pressure oil from the implement pump to flow to the implement.
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| Illustration 2 | g00752751 |
(2) Auxiliary control lever (third function). (3) Lift control lever. (4) Tilt control lever. (5) Implement lockout feature. | |
Levers (2), (3), and (4) are located on the right side of the operator station next to the seat. The control lever for the implement lockout feature (5) is also located on the right side of the operator station next to the seat.
Lift control lever (3) and tilt control lever (4) are components of the standard hydraulic system. Lift control lever (3) activates the lift control valve. This will control the raising and lowering of the bucket. Tilt control lever (4) activates the tilt control valve. This will control the dump or the tilt back of the bucket.
The auxiliary hydraulic system has control lever (2) and auxiliary cylinders in addition to the standard hydraulic system.
Implement lockout feature (5) is used to sustain the control levers in the neutral or HOLD positions. The hydraulic control lever lock is moved toward the operator in order to lock out the hydraulic control levers. The shaft of the hydraulic control lever lock goes through a hole in each of the hydraulic control levers. This will not permit the hydraulic control levers to be moved out of the HOLD position.