Introduction

NOTE: For Specifications with illustrations, make reference to the SPECIFICATIONS for 910 LOADER HYDRAULIC SYSTEM, Form No. SENR7220. If the Specifications given in Form SENR7220 are not the same as listed in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications listed in the book with the latest date.

Hydraulic System

LOADER SYSTEM (HYDRAULIC SCHEMATIC)
1. Tilt cylinder on right side. 2. Section of control valve to tilt the bucket. 3. Section of control valve for bucket RAISE or LOWER. 4. Breather for pressure air in hydraulic tank. 5. Filter. 6. Inlet section for pump oil. 7. Pump section for loader hydraulic system. 8. Oil line to loader control valve sections. 9. Pump section for steering hydraulic system. 10. Oil line from hydraulic supply tank. 11. Oil line to steering system. 12. Lift arm on right side. 13. Lift cylinder on right side.

The hydraulic system has one supply tank which holds the oil for both the loader hydraulic system and the steering hydraulic system. The hydraulic pump is a gear-type and has two sections. The location of the pump is on the side of the engine on the right side of the machine. The pump is driven by the timing gears for the engine.

RIGHT SIDE OF MACHINE
1. Tilt cylinder. 7 & 9. Hydraulic pump sections (behind the hood panel). 12. Lift arm. 14. Hydraulic supply tank. 15. Control lever (for tilt and lift control valve sections).

The shaft end is pump section (7) for the loader hydraulic system. The oil from pump (7) goes to inlet section (6) for control valve sections (2) and (3).

HYDRAULIC PUMP
7. Pump section for loader hydraulic system. 8. Oil line to loader control valve sections. 9. Pump section for steering hydraulic system. 10. Oil line from hydraulic supply tank.

There is a relief valve in inlet section (6) for the pump oil. The relief valve setting is approximately 2500 psi (17 000 kPa). The relief valve settings of the two relief valves in the section of control valve (2) for bucket TILT BACK and DUMP are lower than the relief valve in the oil inlet section.

CONTROL VALVE SECTIONS
2. Control valve section to tilt bucket. 3. Control valve section to lift bucket. 6. Inlet section for pump oil. 16. End section.

When both control valve sections (2) and (3) are in HOLD positions the pump oil goes through all of the sections of the control valves and goes out of section (6), through a line to filter (5), through the element in the filter and into the hydraulic supply tank. If the element in filter (5) gets full of dirt, the dirty element is a restriction to the oil going through the element and the oil gets an increase in pressure. The high pressure of the oil opens a bypass valve in filter (5). The oil does not go through the element as the oil goes into the hydraulic tank.

Control Valves

Control Valve Section for Lift

The control lever, for the lift valve section and the tilt valve section, must be held in either the RAISE or LOWER position. A spring on the end of valve spool (4), not shown in the drawings, is compressed when the lever is moved to either the RAISE or LOWER position. The spring will move the lever and valve spool (4) to the HOLD position when the lever is released. A detent, not shown in the drawings, will hold the lever and valve spool (4) in the FLOAT position.

Hold Position

The control valve section for lift is between the inlet section and the control valve section for tilt. The pump oil from the inlet section goes into passage (6) which is a common passage through the control valve sections. Passage (6) has no outlet. The pump oil goes into passages (1) and (3). These two passages do not go through the valve section. When valve spool (4) is in the HOLD position, the pump oil in passages (1) and (3) goes around the valve spool into passage (2). The oil in passage (2) goes into the next control valve section.

If the next valve section is in HOLD position the oil goes through the valve and then goes through a common passage (5) to the tank.

The HOLD position of valve spool (4) and check valve (7) stops the oil in passages (9) and (10). With the oil in the circuit for the lift cylinders stopped the cylinders cannot move until the control lever, and valve spool (4), is moved to either the RAISE, LOWER or FLOAT position.

Raise Position

When the control lever moves valve spool (4) to the RAISE position, the pump oil from the inlet section into passages (1) and (3) cannot go into passage (2) and through the next valve sections to go through passage (5) to the tank.

With no outlet for the pump oil, the oil in passage (6) gets an increase in pressure which opens check valve (7). The pump oil from passage (6) goes through the open check valve into passage (10) and to the head ends of the lift cylinders.

The pump oil going into the head ends of the cylinders moves the pistons and rods which move the lift arms to raise the bucket. The oil from the rod ends of the cylinders goes through passage (9) and then through passage (5) to the filter and tank. The location of the relief valve, for the circuit to lift the bucket, is in the inlet section for the lift valve section.

Lower Position

When the spool valve is in the LOWER position (not shown), the pump oil in passage (6) opens check valve (7) and the flow of pump oil is to passage (9) to the rod ends of the lift cylinders. The pump oil to the rod ends of the cylinders moves the pistons and rods toward the head ends of the cylinders which moves the lift arms down. The oil from the head ends of the cylinders goes through passage (10), through passage (5) and to the filter and tank. The relief valve for the circuit is the relief valve in the inlet section.

VALVE SECTION FOR LIFT (HOLD Position)
1. Passage from pump. 2. Passage to next valve section. 3. Passage from pump. 4. Valve spool (in HOLD position). 5. Passage to tank. 6. Passage from pump. 7. Check valve. 8. Make-up valve. 9. Passage to rod ends of lift cylinders. 10. Passage to the head ends of lift cylinders.

VALVE SECTION FOR LIFT (RAISE Position)
1. Passage from pump. 2. Passage to next valve section. 3. Passage from pump. 4. Valve spool (in RAISE position). 5. Passage to tank. 6. Passage from pump. 7. Check valve. 8. Make-up valve. 9. Passage to rod ends of lift cylinders. 10. Passage to head ends of lift cylinders.

VALVE SECTION FOR LIFT (FLOAT Position)
1. Passage from pump. 2. Passage to next valve section. 3. Passage from pump. 4. Valve spool (in FLOAT position). 5. Passage to tank. 6. Passage from pump. 7. Check valve. 8. Make-up valve. 9. Passage to rod ends of lift cylinders. 10. Passage to head ends of lift cylinders.

Float Position

A detent on the end of valve spool (4) (not shown) holds the valve spool in the FLOAT position. The operator must move the lever to get the valve spool out of the detent for the FLOAT position.

When valve spool (4) is in FLOAT position, the pump oil goes through passages (1) and (3) into passage (2) and through the next valve sections to passage (5). The position of valve spool (4) lets the pump oil in passage (5) go to both passage (9) and (10), to the rod ends and head ends of the lift cylinders. With the pump oil in both ends of the lift cylinders at the same pressure and passages (9) and (10) open to the tank through passage (5), the position of the lift arms is not controlled by the pump oil.

With the control lever and valve spool (4) in FLOAT Position, the weight of the lift arms and bucket is the only controlling force.

Make-Up Valve

The make-up valve is in the control valve section for lift. The make-up valve is in passage (2) to the rod ends of the lift cylinders.

A spring (1) and oil pressure in the spring chamber hold the valve closed. The valve opens only when the flow of pump oil to the rod ends of the lift cylinders is not enough when the control valve spool is in either the FLOAT or LOWER position.

MAKE-UP VALVE
1. Spring. 2. Passage to rod ends of lift cylinders. 3. Valve in CLOSED position. 4. Valve in OPEN position.

When the flow of oil to the rod ends of the cylinders is not enough, the pressure of the oil in passage (2) is low. The higher pressure of the oil in the passage to the tank opens the valve and lets more oil go to the rod ends of the cylinders.

Main Relief Valve and Tilt Relief Valve

The location of the main relief valve is in the inlet section for the control valve. The setting of the main relief valve is approximately 2500 psi (17 000 kPa).

The location of the two tilt relief valves is in the control valve for TILT BACK and DUMP. The setting of the relief valve in the rod end passage is approximately 2250 psi (15 500 kPa). The setting of the relief valve in the head end passage is approximately 1200 psi (8300 kPa).

RELIEF VALVE CROSS SECTION
1. Passage to spring chamber. 2. Valve. 3. Spring. 4. Passage to tank. 5. Pilot valve. 6. Spring. 7. Screw for adjustment. 8. Locknuts.

The relief valve is a pilot-type valve. Pump oil, through passage (1) into the spring chamber, and spring (3) hold valve (2) closed. The pressure of the pump oil is against pilot valve (5) which is held closed by spring (6).

Pump oil in spring (3) chamber with more pressure than the force of spring (6), holding pilot valve (5) closed, will open the pilot valve. The oil in spring (3) chamber goes through the open pilot valve and through passage (4) to the tank, faster than the oil which goes through passage (1). With only the force of spring (3) on valve (2) the pressure of the pump oil against valve (2) opens it and the pump oil goes to the tank. The open relief valve keeps the pressure of the pump oil from going higher than the setting of the relief valve.

The relief valve is also a make-up valve. When the pressure of the pump oil to the cylinder is less than the pressure of the return oil from the cylinders the pressure of the oil through passage (1) into the chamber for spring (3) is also less. When the pressure of the return oil has more force on valve (2) than spring (3) has on the valve, the valve opens. The return oil goes through valve (2) into the pump oil and the pressure of the pump oil and the return oil is the same.

VALVE SECTION FOR TILT (HOLD Position)
1. Passage from pump. 2. Passage to next section. 3. Passage from pump. 4. Valve spool (HOLD position). 5. Passage to tank. 6. Passage from pump. 7. Relief valve for bucket dump circuit. 8. Relief valve for bucket tilt back circuit. 9. Passage to rod ends of tilt cylinders. 10. Check valve. 11. Passage to head ends of tilt cylinders.

If the relief valve setting needs an adjustment, screw (7) is turned in the direction needed to get either a pressure decrease or pressure increase. Locknuts (8) are used to keep screw (7) from turning after the adjustment is made.

Control Valve Section for Tilt

The control lever, for the tilt valve section, must be held in either the TILT BACK or DUMP position. A spring on the end of valve spool (4), not shown in the drawings, is compressed whenever the lever is moved to either the TILT BACK or DUMP position. When the lever is released the spring moves valve spool (4) and the lever to the HOLD position.

Hold Position

The location of the control valve section for tilt is between the control valve section for lift and section (12) at the end of the valve sections. The section at the end turns the pump oil from passage (2) into passage (5) in the valve section for tilt.

The pump oil from the valve section for tilt goes into passage (6) which is a common passage through the sections of the control valve. Passage (6) has no outlet to the tank. The pump oil also from the valve section for tilt goes into passages (1) and (3). These passages do not go through the valve section. When valve spool (4) is in HOLD position, the oil in passages (1) and (3) goes around the valve spool into passage (2). The oil in passage (2) goes to the end section (12). The oil from passage (2), in the end section, goes into passage (5) to the tank.

LOADER CONTROL VALVE
4. Valve spool for tilt. 7. Relief valve. 11. Passage (in tilt valve section) for head ends of tilt cylinders. 12. End section.

VALVE SECTION FOR TILT (TILT BACK Position)
1. Passage from pump. 2. Passage to next section. 3. Passage from pump. 4. Valve spool (TILT BACK position). 5. Passage to tank. 6. Passage from pump. 7. Relief valve for bucket dump circuit. 8. Relief valve for bucket tilt back circuit. 9. Passage to rod ends of tilt cylinders. 10. Check valve. 11. Passage to head ends of tilt cylinders.

The HOLD position of valve spool (4) and check valve (10) stop the oil in passages (9) and (11). With the oil in the circuits to the tilt cylinders stopped the cylinders cannot move until the control lever, and valve spool (4), is moved to either the TILT BACK or DUMP position.

Tilt Back Position

When the control lever moves valve spool (4) to the TILT BACK position, the pump oil in passages (1) and (3) cannot go into passage (2), through the next valve section and through passage (5) to the tank.

With no outlet for the pump oil, the oil in passage (6) gets an increase in pressure which opens check valve (10). The pump oil in passage (6) goes through the open check valve into passage (9) and to the rod ends of the tilt cylinders.

The pump oil going into the rod ends of the tilt cylinders moves the pistons and rods which move the bucket to tilt back. The oil from the head ends of the cylinders goes through passage (11) and then through passage (5) to the filter and tank.

Dump Position

When the valve spool is in the DUMP position, not shown, the pump oil in passage (6) opens check valve (10) and the flow of pump oil is to passage (11) to the head ends of the tilt cylinders. The pump oil to the head ends of the cylinders moves the pistons and rods which move the bucket to dump. The oil from the rod ends of the cylinders goes through passage (9), through passage (5) and to the filter and tank.

Bucket Positioner (Visual)

BUCKET POSITIONER (VISUAL)
1. Rod assembly. 2. Rod of the tilt cylinder. 3. Pipe assembly.

The bucket positioner is a visual aid, for the operator to stop the bucket at the correct digging angle when the bucket is being moved from dump toward tilt back.

A rod assembly (1) is on the rod (2) of the tilt cylinder on the right side of the machine. The rod assembly goes through a pipe assembly (3) on the tilt cylinder. The correct digging angle (bucket position) is when the rod assembly is seen at the end of the pipe assembly. Stop the tilt back at this time.

Lift And Tilt Back Kickouts And Bucket Positioner

The lift and tilt back kickouts and the bucket positioner are electric and both the kickouts and the bucket positioner are automatic.

LIFT CONTROL
1. Control lever. 2. Lift lever assembly. 3. Electro magnet.

When the engine is running, an electric switch (14) is closed by engine lubricating oil pressure. An electro-magnet (3) holds control lever (1) in RAISE and/or TILT BACK positions. Move control lever (1) to RAISE position. Lift lever assembly (2) in the linkage to the hydraulic control valve moves a magnet, on lever assembly (2) near open switch (4) which closes the open switch and puts a charge in electro-magnet (3). At the same time lever assembly (2) is against the electro-magnet which holds it and control lever (1) in the RAISE position.

CONTROL LEVER LINKAGE
1. Control lever. 2. Lift lever assembly (Magnet). 3. Electro-magnet (not seen). 4. Switch (normally open). 5. Solid state switch. 6. Switch (normally open). 7. Magnet (on tilt lever assembly). 8. Tilt lever assembly.

When the lift arms go up, magnet (9) on the lift arm moves toward a closed switch (10) on the vehicle frame. When magnet (9) gets near switch (10) the switch opens and electro-magnet (3) has no charge to hold lift lever assembly (2) and control lever (1) in RAISE position. The lift kickout can prevent the lift arms from hitting the lift stops.

LEVER LINKAGE
1. Control lever. 2. Lever assembly. 3. Electro-magnet. 6. Switch (normally open). 7. Magnet (on tilt lever assembly). 8. Tilt lever assembly.

LIFT ARM FOR RIGHT SIDE
9. Magnet (on lift arm). 10. Switch (normally closed).

Move the control lever (1) to TILT BACK position, when bucket is in dump, and magnet (7) on tilt lever assembly (8) moves near normally open switch (6). The magnet closes the switch and puts a charge in electro-magnet (3). At the same time tilt lever assembly (8) is against the electro-magnet which holds the tilt lever assembly and control lever (1) in TILT BACK position.

When the bucket moves to the digging position, magnet (12) on the plate on the retracted rod, of the right side tilt cylinder, opens switch (11) and the electro-magnet has no charge. With no electro-magnet charge, tilt lever assembly (8) and control lever (1) are not held in TILT BACK position.

TILT CYLINDER FOR RIGHT SIDE
11. Switch (normally closed). 12. Magnet. 13. Magnet.

Move control lever (1) to TILT BACK position, when the bucket is in digging position, and electro-magnet (3) holds the controls in TILT BACK position. When the bucket tilts back, magnet (13) on the plate on the tilt cylinder rod, nears normally closed switch (11) and the switch opens. With switch (11) open, electro-magnet (3) has no charge and control lever (1) is not held in TILT BACK position. The tilt back kickout can prevent the bucket from hitting the tilt back stops.

WIRING DIAGRAM
2. Magnet for lift lever assembly. 3. Electro-magnet. 4. Switch (normally open). 5. Solid state switch. 6. Switch (normally open). 7. Magnet on tilt lever assembly. 9. Magnet on lift arm. 10. Switch (normally closed). 11. Switch (normally closed). 12 & 13. Magnets on plate on tilt cylinder rod. 14. Switch (oil pressure). 15. Fuse. 16. Battery.