ENGINE NOT RUNNING

Lift Pilot Valve Lower Kickout Cushion Solenoid Valve Sequence Valve Raise Stop Solenoid Valve From Lift Cylinders Tilt To Implement Cooler

Implement Pilot System

The implement pilot system is made up of the following components. The illustration shows the location of the components in the loader frame

- Pilot Filter Group (1) - Loader frame (2) - Pilot pump (gear) (3)

- Selector and pressure reducing valve (4) - Float sequence valve (5)

- Pilot relief valve (6)

- Selector valve (thermal bypass) (7) - Selector valve (thermal bypass) (8)

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4 5

6

The upper illustration shows the pilot filter group that is located in the loader frame (1). The pilot filter group is equipped with a filter (3) that is rated at 6 micron and a differential pressure switch (2). The pressure switch communicates with the VIMS module relaying the pressure drop across the filter group.

The lower illustration shows the location of the following pilot components: the selector and pressure control valve (6), check valve (7), check valve (8), float sequence valve (9), pilot relief valve (10), and selector valves (thermal purge) (11) and (12).

Also shown are the implement hydraulic tank (4) and the variable pump solenoid valve (5). 108 109 2 5 6 7 3 8 9 4 11 12 10 1

Pilot Control Valve

The pilot control is located in the cab to the right of the operator's seat. The control consists of the tilt control lever (2), the lift control lever (3), and the implement lever lock (1). When the implement lever lock is in the forward position, the control levers are unlocked. When the lever lock is pulled back, the control levers are locked.

The pilot control valve is also equipped with detent coils (not shown). The detent coils will hold the lift control lever in the full RAISE position, full LOWER position, and/or the tilt control lever in the full TILT BACK positions until the linkage has reached the set kickout position.

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2

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Tilt Pilot Control Valve

This illustration shows a sectional view of the tilt pilot control valve in the HOLD position. When the engine is running and the control lever is in the HOLD position, pilot oil from the pilot pump enters the pilot control valve and is blocked by the dump and tilt back metering stems.

The lift pilot control valve operates the same way as the tilt pilot control valve.

The tilt pilot control valve is equipped with a detent coil for the tilt back function only. When the tilt control lever is pulled to the DETENT position, the retainer will engage the detent coil. The detent coil will hold the retainer until the current to the detent coil is interrupted. The lift pilot control valve is equipped with a detent coil for both raise and lower functions as shown in the next illustration.

Upper Plunger (Dump)

Upper Centering Spring Lower Plunger

Retainer

Metering Spring

Tilt Back Metering Stem Retainer

Upper Centering Spring Lower Plunger Retainer Lower Centering Spring Metering Stem Spring Dump Metering Stem Retainer

Pivot Plate

Detent Coil

Metering Stem Spring Upper Plunger (Tilt Back)

To Main Control Valve

From Pilot Pump To Hydraulic Tank

TILT PILOT CONTROL VALVE

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Lift Pilot Control Valve

This illustration shows a sectional view of the lift pilot control valve in the RAISE position. In the RAISE position, the pilot oil (orange) from the pilot pump enters the control valve. When the operator moves the lift control lever into the raise direction, the pivot plate is rotated and the upper plunger, the upper retainer, lower plunger, metering spring, the lower retainer and the metering stem moves downward. As the metering stem moves downward, the port holes in the stem pass over the oil passage from the pilot pump. Pilot oil flows from the passage through the center of the metering stem to the end of the lift stem in the main control valve (not shown). At the same time, the metering stem spring is adding an upward force against the upper edge of the metering stem. Return oil from the main control valve through the lower metering stem, the center of the metering stem and to the tank port.

The objective of the metering stem is to allow movement of the stem in the main control valve proportionally with the movement of the pilot control lever. The metering stem and the

metering spring function as a pressure reducing valve and control the pilot oil pressure at the end of the main control valve stem.

As the metering stem moves downward, pilot oil flows through the orifice, the center of the metering stem and out to the main control valve.

To Main Control Valve From Pilot Pump

To Hydraulic Tank

Raise Metering Stem Lower / Float

Metering Stem Detent Coil (Raise)

From Main Control Valve

Detent Coil (Float)

Metering Stem Spring Metering Spring Center Retainer Lower Plunger

Upper Centering Spring Upper Plunger

Upper Retainer Pivot Plate

At the same time, pilot oil from the main control valve flows back to the hydraulic tank through pilot control valve. The lift pilot control valve operates the same way as the tilt pilot control valve.

The lift pilot control valve is equipped with a detent coil for both raise and lower functions. The flow of pilot oil is blocked at the main control valve stem causing the pilot pressure to increase. The pressure increase overcomes the centering spring for the main control valve stem and shifts the stem. Then, supply oil is directed to the actuator.

The pressure increase is also sensed against the lower end of the metering stem. When the pressure increase overcomes the applied force, the metering stem moves up and compresses the metering spring. The upward movement restricts the flow of pilot through the orifice in the metering stem. Restricting the pilot oil flow controls the signal pressure at the stem of the main control valve. The metering spring therefore adjusts the pressure at the main control valve stem in proportion to the movement of the pilot control lever.

When the lift control lever is moved to full travel and the detent coil is energized, the upper retainer (raise) will be held in position by electromagnetic force of the detent coil. The detent coil will be energized until the position sensor (not shown) recognizes the kickout position. The lever can be removed from a detent position manually.

When the operator moves the lift control lever to the full LOWER position, the lower side of the pilot control valve will operate similarly to the raise side and the float detent coil will hold the control valve in the FLOAT position.

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Implement Hydraulic System Not in Dig Trigger Mode

The implement hydraulic system is equipped with three fixed displacement piston pumps and one variable displacement piston pump. The three fixed displacement pumps and the variable displacement pump draw oil from the implement hydraulic tank. The supply oil is directed through the high pressure screens, the individual relief valves, and the check valves. The relief valve limits the supply oil pressure that is flowing to the left and right control valves. This illustration shows the main control valve with a raise signal from the pilot control valve (not shown). Supply oil is sent to the head end of the lift cylinders from the main control valve. Also, each individual piston pump is equipped with its own case drain filter.

Oil flow from the three fixed displacement pumps and the variable displacement pump provide system oil to the lift and tilt cylinders. Oil flow is metered to the cylinders by the stems in the main control valves. The oil flow around the stems is controlled by the movement of the stems in the valve through the pressure that is applied to the ends of the stems. The operator controls the pilot oil flow and pressure that shifts the stems with controlled movement of the pilot control valve. Also, movement of the valve stems opens a passage for the oil in the opposite end of the cylinders to return to the implement hydraulic tank.

Implement Hydraulic Tank

Control Valve (Left side Front Frame) Right Implement Pump Tandem Implement Pump Relief Valve Relief Valve Control Valve (Right Side Front Frame) Relief

Valve

High Pressure Screens

High Pressure Screen Case Drain Filters Check Valve Check Valve Check Valve Solenoid Valve Lift Head End Sensor Implement Pump Pressure Sensor

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Implement Hydraulic System In Dig Trigger Mode

In this illustration, the graphic shows the machine in dig trigger mode. The machine is in first speed forward, the ground speed is less than 6.8 kmh (4.25 mph), and the B-Pin is below the horizontal line of the A-Pin.

The three fixed displacement piston pumps are supplying the oil flow to the implement hydraulic system. The variable displacement piston pump is destroked to zero displacement. The implement pumps draw oil from the implement hydraulic tank. The supply oil is directed through the high pressure screens, past the individual relief valves, and the check valves. The individual relief valve limits the supply oil pressure that is flowing to the left and right control valves. This illustration shows the main control valve with a raise signal from the pilot control valve (not shown).

Also, each individual piston pump is equipped with its own case drain filter.

A decrease of supply oil will be sent to the head end of the lift cylinders until the implement system no longer meets the criteria for dig trigger.

Implement Hydraulic Tank

Control Valve (Left side Front Frame) Left Implement Pump Right Implement Pump Tandem Implement Pump Relief Valve Relief Valve 994F IMPLEMENT HYDRAULIC SYSTEM Relief Valve Control Valve (Right Side Front Frame) Relief

Valve Screen

High Pressure Screens

High Pressure Screen

VARIABLE DISPLACEMENT