Introduction

NOTE: For Specifications with illustrations, make reference to the SPECIFICATIONS for 931 LOADER HYDRAULICS, Form No. SENR7220. If the Specifications in Form No. SENR7220 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

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

The hydraulic pump (13) is a gear-type and has one section. The location of the pump is on the left side of the engine and is driven by the timing gears for the engine.

RIGHT SIDE OF MACHINE
1. Tilt cylinder. 9. Lift cylinder. 12. Lift arm. 14. Control lever (for tilt and lift control valve sections).

HYDRAULIC PUMP
10. Oil line from hydraulic supply tank. 11. Oil line to control valve sections. 13. Pump for loader hydraulic system.

There is a relief valve in inlet section (8) for the pump oil. The relief valve setting is approximately 2500 psi (175.7 kg/cm²) (17 200 kPa). The relief valve settings of the two relief valves in the section of control valve (4) for bucket TILT BACK and DUMP are lower than the relief valve in the oil inlet section.

When the control valve sections are in HOLD positions, the pump oil goes through all of the sections of the control valves and goes out of section (8), through a line to filter (6), through the element in the filter and into the hydraulic supply tank. If the element in filter (6) 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 (6). The oil does not go through the element as the oil goes into the hydraulic tank.

Control Valve Section For Tilt

A spring (6), on the end of valve spool (4) is compressed when the control lever is moved to either the TILT BACK or DUMP position. The control lever must be held in either position. When the lever is released the spring moves the valve spool and the lever to the HOLD position.

HOLD Position

The control valve section for tilt is between inlet section (14) and control valve section for lift (13). The pump oil from the inlet section goes into passage (2). Passage (2) does not go through the valve section for tilt.

When valve spool (4) is in HOLD position the oil in passage (2) goes around the valve spool and into passages (1 and 3). Passages (1 and 3) are open to the valve section for lift. When the control levers for the control valve assembly are in HOLD positions the pump oil goes through all of the valve sections to end section (12). The pump oil in end section (12) then goes through the control valve. sections and passage (5). Passage (5) is the passage to inlet section (14) which lets the oil go through a line to the filter and then into the tank.

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

CONTROL VALVE ASSEMBLY
7. Relief valve (for dump circuit). 9. Passage oil line to rod ends of tilt cylinders. 11. Passage oil line to head ends of tilt cylinders. 12. End section. 13. Control valve section for lift. 14. Inlet section.

The HOLD position of valve spool (4) stops the oil on the other side of check valve (10) and the pump oil in passage (2) cannot open the check valve. Valve spool (4) in HOLD position also stops the oil in passages (9 and 10) to the tilt cylinders. When the oil in the circuits to the tilt cylinders is stopped, the cylinders cannot move until the control lever, and valve spool (4), is moved to either the TILT BACK or DUMP position.

DUMP Position

When the control lever moves valve spool (4) to the DUMP position, the pump oil in passage (2) cannot go into either passage (1) or passage (3) and the pump oil opens check valve (10).

The pump oil goes through the open check valve, around valve spool (4), and into passage (11) to the head ends of the tilt cylinders. The pump oil in the head ends of the tilt cylinders moves the pistons and rods which move the bucket to dump.

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

The oil pushed from the rod ends of the tilt cylinders, by the pistons, goes through passage (9) and into passage (1) to the valve section for lift. The oil goes through the valve for lift and the end section and then through passage (5) to the filter and tank.

TILT BACK Position

When the valve spool is in the TILT BACK position (not shown), the pump oil in passage (2) opens check valve (10) and the flow of pump oil is to passage (9) to the rod ends of the tilt cylinders. The pump oil in the rod ends of the 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 (10), through control valve section for lift, the end section and through passage (5) to the filter and tank.

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 control valve section for tilt and end section. The oil from the tilt section goes into passage (6) which is a common passage through all control valve sections. Passage (6) has no outlet. The oil from the tilt valve section also 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 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 or end section.

If the next valve section is in HOLD position or if the end section is next, the oil 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.

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 head ends of lift cylinders.

RAISE Position

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 the head ends of lift cylinders.

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.

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.

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.

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.

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

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. 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 Valves

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 (175.7 kg/cm²) (17 200 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 (158.2 kg/cm²) (15 500 kPa). The setting of the relief valve in the head end passage is approximately 1200 psi (84.4 kg/cm²) (8280 kPa).

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.

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.

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.

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.

Ripper Hydraulics

HYDRAULIC SYSTEM WITH RIPPER
1. Relief valve (in passage to head end of ripper cylinder). 2. Valve section (to RAISE and LOWER ripper). 3. Filter. 4. Breather. 5. Supply tank. 6. Cylinder (for ripper). 7. Relief valve (in inlet section of control assembly). 8. Inlet section (of control assembly). 9. Valve sections (for loader control). 10. Hydraulic pump. 11. Ripper assembly.

When the machine has a ripper, the ripper hydraulics is part of the hydraulic system. Valve section (2) for the ripper is an addition to valve sections (9).

CONTROL ASSEMBLY
1. Relief valve (in passage to head end of ripper cylinder). 2. Valve section (to RAISE and LOWER ripper). 7. Relief valve (in inlet section of control assembly). 8. Inlet section (of control assembly). 9. Valve sections (for loader control).

CONTROL LEVERS
12. Control lever (held in RAISE position for ripper). 13. Control lever (to control valves for loader). 14. Control lever (to valve section for multi-purpose bucket).

Control lever (12) for the ripper is connected to the valve spool in valve section (2).

RIPPER
6. Ripper cylinder. 11. Ripper assembly.

Relief valve (7) is in the pump oil passage to all of the valve sections (2 and 9) and to both the head end and rod end of cylinder (6). Relief valve (1) is in the passage to the head end of cylinder (6). The relief valve opens at approximately 3750 psi (263.6 kg/cm²) (25 860 kPa).

Relief valve (1) in the hydraulic system is a protection for the tooth groups of ripper assembly (11). Ripper assembly (11) can move the rod up into cylinder (6), which opens relief valve (1), if the tooth group comes against material that can not be moved.

Valve Section for Ripper in HOLD Position

VALVE SECTION IN HOLD POSITION
1. Passage to tank. 2. Passage from pump. 3. Passage to end section. 4. Passage from pump. 5. Valve spool. 6. Passage from pump. 7. Passage to rod end of the cylinder. 8. Check valve. 9. Passage to head end of the cylinder. 10. Relief valve. A. LOWER position. B. HOLD position. C. RAISE position.

The pump oil from the other valve sections of the control assembly goes into passages (2), (4) and (6). When valve spool (5) is in HOLD position the oil in passages (2) and (4) goes around the valve spool and through passage (3). The oil in passage (3) goes to the end section of the control assembly and then through passage (1). Passage (1) is to the passages through all of the valve sections and the oil goes to the filter and tank.

The HOLD position of valve spool (5) stops the oil in passages (7) and (9) to the cylinders. The cylinders can not move until the control lever for the ripper is moved to another position.

When the ripper, in the ground, comes against a piece that will not move, the ripper moves up. As the ripper is moved up, the pressure of the oil in the head end of the cylinder gets an increase. Relief valve (10) opens to let the oil run out of the head end of the cylinder when the pressure of the oil is approximately 3750 psi (263.6 kg/cm²) (25 860 kPa).

Valve Section for Ripper in LOWER Position

VALVE SECTION IN LOWER POSITION
1. Passage to tank. 2. Passage from tank. 3. Passage to end section. 4. Passage from pump. 5. Valve spool. 6. Passage from pump. 7. Passage to rod end of cylinder. 8. Check valve. 9. Passage to head end of the cylinder. 10. Relief valve. A. LOWER position. B. HOLD position. C. RAISE position.

When valve spool (5) is in the LOWER position, the pump oil in passages (2) and (4) can not go into passage (3) and the pump oil in the valve section gets an increase. The pressure of the oil in passage (6) opens check valve (8) and the oil goes through the check valve, through passage (9) to the head end of the ripper cylinder. The oil in the head end moves the rod out of the cylinder which moves the ripper assembly down.

The oil from the rod end of the cylinder goes through passage (7), through passage (1) and to the filter and tank.

RAISE Position

When valve spool (5) is in RAISE position (not shown), the pump oil in passage (6) goes through the check valve and passage (7) to the rod end of the ripper cylinder. The oil in the rod end moves the rod into the cylinder which moves the ripper assembly up.

The oil from the head end of the cylinder goes through passage (9), through passage (1) and to the filter and tank.

Multi-Purpose Bucket

The hydraulics for the multi-purpose bucket is part of the hydraulic system. The valve section for the bucket is part of the control assembly for the loader. The valve section for the bucket is between the valve section for lift and the end section. If the machine has a ripper and a multi-purpose bucket, the valve section for the bucket is between the valve section for lift and the valve section for the ripper.

MULTI-PURPOSE BUCKET IN CLOSED POSITION
1. Hydraulic cylinders (to open or close the bucket).

The valve section for the bucket is the same as the valve section for the ripper except the valve section for the bucket has two relief valves. The two relief valves have the same settings, approximately 3000 psi (210.9 kg/cm²) (20 700 kPa).

CONTROL LEVERS
2. Control lever for bucket (held in CLOSED position). 3. Control lever (for loader lift and bucket tilt). 4. Control lever (for ripper).

When control lever (2), for the bucket, is moved to CLOSED position the linkage from the lever moves the valve spool farther into the control valve. The pump oil in the control valve now goes to the head ends of the cylinders on the bucket. The oil in the head ends push the pistons and rods farther out of the cylinders which closes the bucket.

The flow of oil in the control valve for the bucket in CLOSED position is the same as the flow of oil in the control valve for the ripper in LOWER position. See the illustration for the subject, VALVE SECTION FOR RIPPER IN LOWER POSITION.

Bucket Positioner (Visual)

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

Rod assembly (1) is on rod (2) of the tilt cylinder, on the right side of the machine. The rod assembly goes through tube assembly (3) on the tilt cylinder. The correct angle to dig (bucket position) is when the rod assembly is seen at the end of the tube assembly. Stop the tilt back at this time.

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

Lift and Tilt Back Kick-Outs And Bucket Positioner - (With 6S8367 Lever Assembly, 6S 6S8356 Switch Assembly)

The lift and tilt back kick-outs and the bucket positioner are electric and both the kick-outs and the bucket positioner are automatic.

WIRING DIAGRAM
1. Ammeter. 2. Oil pressure switch. 3. Fuse. 4. Electro-magnet. 5. Solid state switch. 6. Lift lever switch assembly (normally open). 7. Tilt lever switch assembly (normally open). 8. Switch on tilt cylinder (normally open). 9. Switch on loader frame (normally open).

When the engine is running, switch (2) is closed by engine lubrication oil pressure. Electro-magnet (4) holds lift lever (11) and control handle (10) in RAISE and/or TILT BACK positions. Move control handle (10) to RAISE position. Lift lever (11) moves away from switch assembly (6), which closes switch assembly (6) and puts a charge in electro-magnet (4). At the same time lift lever (11) is against the electro-magnet which holds it and control handle (10) in RAISE position.

HYDRAULIC CONTROL CONSOLE
4. Electro-magnet. 5. Solid state switch. 6. Lift lever switch assembly (normally open). 10. Control handle. 11. Lift lever.

NOTE: The 6S8356 Switch Assembly is made up of a magnet and a normally open switch. When metal goes between the magnet and the switch, the switch opens. When there is no metal between the magnet and the switch, the switch is closed.

When the bucket lift arms move up, plate (12) on the right side arm, will move toward switch assembly (9) on the loader frame. When plate (12) is between the magnet and switch, switch assembly (9) opens and electro-magnet (4) has no charge to hold lift lever (11) and control handle (9) in RAISE position. The lift kick-out will prevent the lift arms from hitting the lift stops.

LIFT ARM (RIGHT SIDE)
9. Switch assembly (normally open). 12. Plate.

HYDRAULIC CONTROL CONSOLE (SIDE COVER REMOVED)
4. Electro-Magnet. 6. Lift lever switch assembly. 7. Tilt lever switch assembly. 11. Lift lever.

Move control handle (10) to the TILT BACK position. When the bucket is dumped, tilt lever (13) will move away from switch assembly (7). At the same time tilt lever (13) is against electro-magnet (4), which holds tilt lever (13) and control handle (10) in TILT BACK position.

TILT LEVER
4. Electro-magnet. 7. Tilt lever switch assembly. 13. Tilt lever.

TILT CYLINDER (RIGHT SIDE)
8. Switch assembly. 14. Plate.

Move control handle (10) to TILT BACK position, when the bucket is in the correct position to dig, electro-magnet (4) holds the controls in TILT BACK position. When the bucket tilts back, plate (14) on the right side tilt cylinder, opens switch assembly (8), and the electro-magnet has no charge. With no charge, the electro-magnet can not hold tilt lever (13) and control handle (10) in TILT BACK position.

Lift And Tilt Back Kick-Outs And Bucket Positioner - (With 6S9161 Lever Assembly, 6S5996 Switch Assembly, and 3Y2126 Magnet)

The 6S5996 Switch Assembly (normally open) is located behind the 6S9161 Lever Assembly. The 3Y2126 Magnet is clamped to bracket (16).

6S5996 SWITCH ASSEMBLY
7. 6S5996 Switch Assembly. 13. 6S9161 Lever Assembly. 15. 3Y2126 Magnet. 16. Bracket.

Move control handle (10) to TILT BACK position. When the bucket is in dump, switch assembly (7) on tilt lever (13) moves toward magnet (15). The magnet closes switch assembly (7) and puts a charge in electro-magnet (4). At the same time tilt lever (13) is against electro-magnet (4) which holds tilt lever (13) and control handle (10) in TILT BACK position.

HYDRAULIC CONTROL CONSOLE
7. Switch Assembly. 13. Tilt Lever Assembly. 15. Magnet.

When the bucket moves to the correct position to dig, plate (14) on rod (3) of the right side tilt cylinder opens switch assembly (8) and the electro-magnet has no charge. With no electro-magnet charge, tilt lever assembly (13) and control handle (10) are not held in TILT BACK position.

TILT CYLINDER (RIGHT SIDE)
8. Switch assembly (normally open). 14. Plate.

Move control handle (10) to TILT BACK position, when the bucket is in DUMP position, and electro-magnet (4) has no charge. With no charge, electro-magnet (4) can not hold tilt lever (13) and control handle (10) in TILT BACK position.