Usage:
Specifications
NOTE: For Specifications with illustrations, make reference to the Specifications for 953C Track-Type Loader Hydraulics, SENR8408. If the Specifications given in SENR8408 are not the same as given in the Systems Operation and Testing and Adjusting, look at the printing date on the cover of each book. Use the Specifications given in the book with the latest date.
General Description
Location of Components
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Hydraulic oil, under pressure higher than 27 500 kPa (4000 psi) can remain in the hydraulic system after the engine and pump have been stopped. Serious injury can be caused if pressure is not released before any work is done on the hydraulic system. To release any pressure, move the hydraulic control levers into all positions after the engine is OFF. When possible, the bucket must always be flat on the ground before service work is started. When the bucket is raised for tests or adjustments, be sure that the lift arms have correct support and the bucket is in the FULL DUMP position. Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are made. |
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The loader hydraulic system controls the operation of the bucket and attachments (ripper and/or multi-purpose bucket.)
The standard system has an implement pump (13), hydraulic tank and valve group (3) [with lift and tilt control valve (12) and oil filter (4) inside].
It also has a control linkage with mechanical bucket positioner and lift kickout, lift cylinders (8), and tilt cylinder (5).
Location of Pumps
Location of Hydraulic Tank and Valve Group
The optional hydraulic system has ripper cylinders (14) and/or multi-purpose bucket cylinders (7). With a one attachment option, third control valve (11) is used.
The third control valve is inside hydraulic tank and valve group (3). With a two attachment option, diverter valve (10) is used in addition to third control valve (11).
The diverter valve is fastened to the outside of the hydraulic tank and valve group. To control the attachments, an additional control lever is added in the operator's compartment.
Other components include oil cooler (1) and oil cooler supply valve (9).
The hydraulic system is a series circuit that is not completely continuous. The third control valve is first in the series, followed by the tilt and lift circuits.
The lift circuit is last in the series. Return oil from the tilt circuit bypasses (does not flow into) the lift circuit when the tilt control valve is in the TILT BACK position.
All other circuits and functions are in a complete series.
Lift and tilt control valve (12) has two spools; one for bucket raise and lower, and one for bucket tilt back and dump.
The tilt valve spool is manually operated and has three positions: TILT BACK, HOLD and DUMP.
The TILT BACK position has a detent. When moved to an operating position, the tilt valve spool sends oil to tilt cylinder (5).
The lift valve spool is manually operated and has four positions: RAISE, HOLD, LOWER and FLOAT.
The RAISE and FLOAT positions have detents. When moved to an operating position, the lift valve spool sends oil to lift cylinders (8). Both tilt and lift circuits have load check valves.
Makeup valves are in the tilt and lift rod end cylinder lines. Cylinder relief valves are in all cylinder lines except rod end lift.
Operator Control Levers
NOTE: A single control lever is standard, with lift and tilt operations being performed by one control lever.
Third control valve (11) is for multi-purpose bucket or ripper operations.
For fourth valve operations, a diverter valve, located in the third circuit cylinder lines, permits selection of the attachment operation to be performed. Both valves are manually operated.
The third control valve has three positions: OPEN or RAISE, HOLD, and CLOSE or LOWER. The third control valve has a load check valve and cylinder relief valves.
In operation with the tilt hydraulic circuit is the bucket positioner kickout mechanism.
The bucket positioner kick out consists of mechanical linkage and components which automatically return the tilt control lever and valve spool from the TILT BACK detent position to the HOLD position at a preset bucket digging angle. The detent is on the end of the tilt control valve spool.
In operation with the lift hydraulic circuit is the bucket lift kickout mechanism.
The lift kickout consists of mechanical linkage and components which automatically return the lift and tilt control lever and valve spool from the RAISE detent position to the HOLD position at a preset bucket lift height. The detent is on the end of the lift control valve.
Hydraulic Pump
Cross Section of Cartridge
The implement pump is a single-section (cartridge) vane type pump. It is mounted on the splitter box between the drive motor and charge pump.
The components of each cartridge are: inlet support plate (4), outlet support plate (7), rotor ring (6), rotor (8), and vanes (5).
Schematic of Pump Oil Flow
Rotor (8) is driven inside the cartridge by shaft (1). As the rotor speed increases, centrifugal action causes vanes (5) to follow the cam shape (outline with a curve) of rotor ring (6).
System pressure behind vanes (5) keeps them pushed out to make sure there is no leakage around rotor ring (6) surface during normal operations.
Rotor ring (6) has a shape (contour) with two chambers opposite each other that are made (formed) to prevent any hydraulic loads on the bearings.
Rotation of valves (5) and rotor (8) causes the chamber area between vanes to increase in size at the inlet (large diameter) section of rotor ring (6).
The increase in size at the inlet section causes a low pressure or vacuum in the chamber. The pressure difference causes oil to flow into the inlet, where it is stopped between vanes while in rotation.
Oil is then sent with force, through passages in the support plate, to the outlet and into the system as the chamber size decreases at the pressure (small diameter) section of the ring.
NOTE: For more information on vane-type pumps, refer to Special Instruction SEHS9353, Vane Type Hydraulic Pump Identification Guidelines.
Hydraulic Tank and Filter
Hydraulic Tank and Valve Group (Optional Three Valve)
Hydraulic oil tank (8) is fastened to the loader frame on the right front side of the machine, under the front guard between the lift arms. The oil tank is on an angle.
All of the standard equipment valves are inside the oil tank except the main relief (dual pressure) with a 24V solenoid. The main relief valve is mounted on the outside of the tank just below the filler tube.
The components of the standard hydraulic tank (two valve) are: breather valve (1), oil filter (18), filter bypass valve (2), the lift and tilt control valve and its components, screen (7), and oil cooler supply valve (5).
Attached to the lift and tilt control valve are: tilt cylinder relief valves (4) and (13), tilt cylinder makeup valve (16), lift cylinders makeup valve (15), lift cylinders relief valve (14), raise detent (11), and tilt detent (10). The main relief valve is attached to the front of the tank.
Inside the lift and tilt control is tilt control valve spool (3), lift control valve spool (17), and a load check valve for each of the lift and tilt circuits.
Third cylinder relief valve (6) is attached to the third control valve. Inside the third control valve is a third control valve spool (9) and a load check valve.
Oil cooler supply valve (5) is in both two and three valve oil tanks.
Lift and Tilt Control Valve
Lift and Tilt Control Valve (Lift Control Valve Spool in HOLD and Tilt Control Valve Spool in DUMP)
When the tilt control lever is moved to the DUMP position, tilt control valve spool (2) moves down from the HOLD position. Oil flow to the tilt cylinder in the DUMP position is the reverse of oil flow in the TILT BACK position.
Pump oil is sent from inlet passage (8) to load check valve (5). The load check valve opens when the inlet pressure becomes greater than the force of spring (3) and the rod end pressure of the tilt cylinder.
The oil is now free to flow through passage (4) to the rod end of the tilt cylinder and causes the bucket to DUMP.
Oil from the head end of the tilt cylinder comes through passage (7), flows around tilt control valve spool (2), through passage (12), around lift control valve spool (1), and through outlet passage (9) to the oil tank.
The flow of oil in the series circuit sends oil from the head end of the tilt cylinder to the lift control valve spool so that both tilt DUMP and lift RAISE operations can be done at the same time.
The lift operation of the lift arms is much slower during dual functions than when tilt control valve spool (2) is in the HOLD position.
Lift and Tilt Control Valve (Lift Control Valve Spool in HOLD and Tilt Control Valve Spool in TILT BACK Detent)
Oil from the oil pump flows through inlet passage (8) to tilt control valve spool (2).
On machines with a third control valve, the oil flows through the third control valve before it flows to the lift and tilt control valve.
The tilt control valve spool is a spring-centered, open center, manually operated spool with three positions: TILT BACK, HOLD, and DUMP.
There is a mechanical detent (11) in the TILT BACK position. Spring (10) keeps the spool in the HOLD position. Movement of the spool is controlled by the tilt control lever, forward or backward from the HOLD position.
When tilt control valve spool (2) is in HOLD position, pump oil flows from inlet passage (8), through passage (12) and outlet passage (9) to the oil tank. The position of the spool holds (blocks) the oil in both ends of the tilt cylinder and keeps the cylinder from moving.
When the tilt control lever is moved to the TILT BACK position, tilt control valve spool (2) moves up from the HOLD position.
Pump oil is sent from inlet passage (8) to load check vale (5). The load check valve prevents reverse oil flow which can cause cylinder drift or load loss.
Load check valve (5) does not open until the oil pressure becomes greater than the force of spring (3) and the head end pressure of the tilt cylinder.
The oil opens the load check valve, flows out passage (7) to the head end of the tilt cylinder and causes the bucket to TILT BACK.
Oil from the rod end of the tilt cylinder comes through passage (4), around tilt control valve spool (2), through passage (6), around lift control valve spool (1) and through outlet passage (9) to the oil tank.
The flow of oil around the lift control valve spool bypasses the lift circuit and prevents TILT BACK and RAISE operations at the same time.
Lift and Tilt Control Valve (Lift Control Valve Spool in RAISE Detent and Tilt Control Valve Spool in HOLD)
Oil from pump flows through inlet passage (8) to tilt control valve spool (2) before it flows to lift control valve spool (1).
The lift control valve spool is a spring centered, manually operated spool with four positions: RAISE, HOLD, LOWER and FLOAT.
There is a mechanical detent (18) in the RAISE and FLOAT positions. Springs (17) keep the spool in the HOLD position. Movement of the spool is controlled by the lift control lever, forward or backward from the HOLD position.
When lift control valve spool (1) is in the HOLD position, oil flows from inlet passage (8), through passage (12), and outlet passage (9) to the oil tank. The position of the spool holds (blocks) the oil in both ends of the lift cylinders and keeps them from moving.
When the lift control lever is moved to the RAISE position, lift control valve spool (1) moves up from HOLD position.
Pump oil is sent from inlet passage (8), around tilt control valve spool (2), through passage (12) to load check valve (15).
The load check valve does not move (open) until the oil pressure from the pump becomes greater than the force of spring (13) and the head end pressure of the lift cylinders. The oil opens load check valve (15), flows out passage (16) to the head end of the lift cylinders, causing the lift arms to RAISE.
Oil from the rod end of the lift cylinders comes through passage (14) and flows through passages (6) and (9) to the oil tank.
When the lift control lever is moved to the LOWER position, lift control valve spool (1) moves down from HOLD position.
The flow of oil to the lift cylinders is now reverse of the flow in RAISE position. Pump oil flows from inlet passage (8) to load check valve (15).
The load check valve opens when the inlet pressure becomes greater than the force of spring (13) and the rod end pressure of the lift cylinders.
The oil now flows out passage (14) to the rod end of the lift cylinders and causes the list arms to LOWER.
Oil from the head end of the lift cylinders comes through passage (16) and flows through outlet passage (9) to the oil tank.
Lift and Tilt Control Valve (Lift Control Valve Spool in RAISE Detent and Tilt Control Valve Spool in DUMP)
When the tilt control lever is in the DUMP position and the lift control lever is moved to the RAISE position, pump oil flows from inlet passage (8), through load check valve (5) on through passage to rod end of the tilt cylinder (4), causing the bucket to dump.
Oil from the head end of the tilt cylinder flows through passages (7) and (12) to load check valve (15) and on through passage to head end of lift cylinders (16).
The lift cylinders operate (raise the bucket), but the movement of the lift arms is much slower than when the tilt lever is in the HOLD position.
Lift and Tilt Control Valve (Lift Control Valve Spool in FLOAT Detent and Tilt Control Valve Spool in HOLD)
When the lift control lever is moved to the FLOAT position, lift control valve spool (1) moves down from LOWER position.
Pump oil is now free to flow to passages (14), (16), and (9) at the same time. The lift cylinders can now move freely in either direction according to the amount and direction of force on the bucket.
As the cylinder pistons move, all extra oil flows through outlet passage (9) to the tank and pump oil comes from inlet passage (8).
Load Check Valves
Load check valves (5) and (15) prevent reverse oil flow in the cylinders (tilt and lift), which can cause cylinder drift.
For example, when the tilt control valve spool is in TILT BACK position, pump oil opens load check valve (5) and flows through passage (6) to the head end of the tilt cylinder.
If the pressure at inlet passage (8) decreases, the pressure of the oil, along with spring (3), closes load check valve (5) and holds the oil in the head end of the tilt cylinder.
Holding the oil in the head end of the tilt cylinder prevents any movement of the tilt cylinder and does not permit the bucket to dump.
Third Control Valve (optional)
Third Control Valve (in CLOSE or LOWER position)
The optional third control valve is for the operation of an additional or third circuit to control the multi-purpose bucket or ripper.
The third control valve is before (ahead of) the lift and tilt control valve in the series hydraulic circuit.
Third Control Valve Spool
The third control valve spool is a spring centered, manually operated spool with three positions; OPEN or RAISE, HOLD, and CLOSE or LOWER.
Oil from the oil pump flows through inlet passage (8) to the third control valve spool (1). Spring (10) keeps the spool in HOLD position.
Movement of the spool is controlled by the third control lever, forward or backward from the HOLD position.
When third control valve spool (1) is in HOLD position, pump oil flows from inlet passage (8), through passage (6) and outlet passage (9) to the inlet passage of the lift and tilt control valve.
The position of the spool holds (blocks) the oil in passages (4) and (5) and keeps the attachment (multi-purpose bucket or ripper) cylinders from moving.
When the third control lever is moved to the OPEN or RAISE position, third control valve spool (1) moves up from the HOLD position. Pump oil flows from inlet passage (8), through passage (7) to load check valve (3).
The load check valve opens when the pump pressure becomes greater than the force of spring (2) and the rod end pressure of the attachment cylinders.
The oil is now free to flow through passage (5) to the rod end of the attachment cylinders and causes the multi-purpose bucket to OPEN or the ripper to RAISE.
Oil from the head end of the attachment cylinders comes through passages (4) and (6) to outlet passage (9). From the outlet passage, the oil flows to the lift and tilt control valve and back to the oil tank.
When the third control lever is moved to the CLOSE or LOWER position, third control valve spool (1) moves down from the HOLD position.
Oil flow in the CLOSE or LOWER position is the reverse of oil flow in OPEN or RAISE position. Pump oil flows from inlet passage (8) to load check valve (3).
The load check valve opens when the inlet pressure becomes greater than the force of spring (2) and the head end pressure of the attachment cylinders.
The oil flows out passage (4) to the head end of the attachment cylinders and causes the multi-purpose bucket to CLOSE or the ripper to LOWER.
Oil from the rod end of the attachment cylinders comes through passages (5) and (6) to outlet passage (9). From the outlet passage, the oil flows to the lift and tilt control valve and back to the oil tank.
Load Check Valve
The operation of load check valve (3) is the same as the load check valves in the lift and tilt control valve. The load check valve prevents reverse oil flow in the attachment cylinders which can cause cylinder drift.
Relief Valve for Tilt and Lift Cylinders (Head End), and Attachment (Third) Cylinders
Relief Valve
There is a relief valve in each of these circuits: head end of the tilt cylinder, head end of the lift cylinder, head and rod ends of the attachment or third cylinders. These valve are the same in construction and operation.
When any valve spool (tilt control, lift control, or third control) is in HOLD position, the relief valves in the tilt and lift head end or third control head and rod ends limit the maximum amount of pressure in the cylinder lines.
The relief valve for the head end of the lift cylinder gives protection against high outside forces.
If forces become too high, the relief valve opens and permits movement of the lift cylinder pistons.
The relief valve also releases head end pressure when the lift arms are raised or lowered and the tilt control lever is in HOLD position.
The relief valves for the head and rod ends of the bucket or ripper cylinders provide protection against high outside forces.
If forces become too high, the relief valves permit movement of the cylinder pistons preventing damage to the machine components.
Oil from either the head end or rod end of the cylinders is in passage (7).
When the pressure of the oil becomes greater than the force of springs (3), valve (2) moves off its seat and let the oil in passage (7) flow back into the oil tank through passages (1) and (6).
Relief Valve for Tilt Cylinder (Rod End)
Relief Valve
The relief valve for the tilt cylinder rod end circuit has a dual pressure setting.
The dual pressure setting provides a lower pressure setting for the tilt cylinder rod end circuit during normal operation. The dual pressure setting also provides a higher pressure setting during back dragging operation.
When the tilt control valve spool is in HOLD position, the lower pressure setting limits the maximum amount of pressure in the tilt cylinder lines.
Limiting the maximum pressure in the tilt cylinder lines provides protection against high outside forces. If forces become too high, the relief valve permits movement of the cylinder piston preventing damage to the machine components.
The lower pressure setting also releases the rod end pressure when the lift arms are raised with the tilt control valve spool in HOLD position.
Oil from the rod end of the tilt cylinder is in cavity (11). When the pressure of the oil becomes greater than the force of spring (3), valve (2) moves off its seat, allowing oil in cavity (11) to flow back to the oil tank though passage (1).
When the tilt control valve spool is in HOLD position and the lift cylinder rod end oil is under pressure.
The higher pressure setting limits the maximum amount of pressure in the tilt cylinder lines. The higher pressure setting prevents the bucket from rolling out during back dragging operations.
Oil from the rod end of the tilt cylinder is in cavity (11).
Oil from the lift cylinder rod end is in cavity (6).
The oil in cavity (6) is under pressure from the lift cylinder head end circuit. The pressurized oil in cavity (6), combined with the force of spring (5), provides the higher pressure setting.
As oil pressure increases beyond the lower pressure setting, cavity (9) fills with oil forcing valve (2) back against its seat. As oil pressure increases in cavity (6), piston (7) is forced against its seat. The movement of piston (7) increases the force of spring (5) against valve (4).
As pressure increases in cavity (9) to the higher setting, valve (4) moves off its seat allowing oil in passage (8) to flow back to tank through passage (10).
Main Relief Valve (Dual Pressure)
Main Relief valve (Dual Pressure) With Solenoid
The oil pressure on the oil pump is limited by the main relief valve. When a control valve spool is out of HOLD position, the main relief valve also limits the oil pressure to the cylinders.
The main relief valve is in front of all other valves in the series hydraulic circuit.
The main relief valve is a dual setting relief valve. With 24V applied to the solenoid valve, relief moves to the HIGH setting. When the 24V is removed, relief moves to the LOW setting.
The electric signal to the solenoid is controlled by an ON-OFF switch installed in the tilt hand control lever linkage. 24V is applied to the solenoid at all times except when the linkage is in TILT BACK position.
Because of the increased bucket capacity of the machine and improved power to ground, the HIGH relief setting is required to keep from stalling the implements during certain applications. The LOW relief setting is required during TILT BACK of the bucket.
Makeup Valve
Makeup Valve
There are two makeup valves in the hydraulic system. Makeup valve (9) is in the rod end of the lift circuit. Makeup valve (4) is in the rod end of the tilt circuit.
Housing (8) is fastened directly to the lift and tilt control valve. The makeup valves permit oil from the return line to add with pump oil when the cylinder rods are retracted faster than the pump can supply oil to the cylinders.
Orifice (5) causes a restriction to the flow of oil back to the oil tank. The orifice makes sure that there is enough oil available at the makeup valves so that there is not cavitation (vacuum) in the cylinders.
Makeup valve (4) operates when the rod end of the tilt cylinder is retracted quickly as the bucket is dumped.
When the pressure in passage (2) decreases enough, the pressure in passage (7) becomes greater than the force of spring (3).
Makeup valve (4) moves up and oil from passage (7) flows into passage (2) and adds to the oil in the rod end of the tilt cylinder. Makeup valve (4) operates in the same manner when an outside force on the bucket causes the tilt cylinder to be retracted.
Makeup valve (9) operates the same manner as makeup valve (4). Makeup valve (9) operates when the lift arms are lowered.
Oil Cooler
The air-cooled oil cooler uses air that passes through the fins of the cooler to remove the heat from the oil.
Oil Cooler Supply Valve
Oil Cooler Supply Valve
The machine is equipped with a standard oil cooler for the hydraulic and transmission oil. The oil cooler supply valve is needed to send oil to the oil cooler.
Return oil flows through passage (7) and most flows out passage (1). Bypass valve (6) sends all of the oil out of passage (1) and the remainder (only on cold start-up) of the oil flows through the orifice valve.
Oil from the oil cooler comes back through passage (2). The oil then flows out passage (5) to the oil filter.
On cold start-up, when there is a sudden increase (surge) in pressure from passage (7), bypass valve (6) opens, allowing additional oil to flow out passage (5). The additional oil flowing out passage (5) gives protection to the oil cooler against pressure surges. The remainder flows through bypass valve (6) and through passage (5) to the tank.
Oil Filter
Oil Filter
Filter element (2) is held in position inside oil tank (1) by retainer assembly (3) and cover (8). The oil filter is the last component that the oil flows through on its way back into the tank.
During normal operation, all return oil passes through tube (5), housing (4), and retainer assembly (3) to the inside of filter element (2). The oil flows though the element and back into oil tank (1). The element stops any debris that is in the oil.
If the filter element becomes full of debris, the restriction to the flow of oil causes a pressure increase inside filter element (2).
The pressure of the oil causes filter bypass valve (6) to move against the force of its spring allowing some of the oil to flow through tube (7) into the tank.
When the oil does not flow through the filter element, the debris in the oil may cause damage to other components in the hydraulic system.
Correct maintenance must be used to make sure that filter element (2) does not become full of debris and stop the flow of clean oil to the hydraulic system.
Valves
Diverter Valve (Optional)
On machines that have two attachments (multi-purpose bucket and ripper), a diverter (fourth) valve is needed.
The diverter valve is fastened to the rear side of the oil tank. It is the third circuit cylinder lines between the third control valve and the cylinders.
Selector Spool
Diverter Valve in Ripper Control Position
Selector spool (3) is manually operated and has two positions: MULTI-PURPOSE BUCKET CONTROL and RIPPER CONTROL.
In the RIPPER CONTROL position, passages (4) and (7) are open to oil from passage (5) and (6) so that the ripper can be operated. Passages (1) and (2) are closed (blocked).
In the MULTI-PURPOSE BUCKET position, passages (1) and (2) are open to oil from passages (5) and (6) so that the multi-purpose bucket can be operated. Passages (4) and (7) are closed (blocked).
Bucket Control Group
Bucket Control Group
The bucket control group provides a way to control the operation of bucket (6).
The group is made up of: two lift cylinders (1), one tilt cylinder (2), lift arm assembly (3), lever (4) and link (5).
Placement of link (5) between the lift arm assembly is known as Z-bar linkage because of the "Z" formed by the tilt cylinder, lever and link.
Tilt cylinder (2) lift cylinders (1) and lift arm assembly (3) are fastened to the loader frame by pins.
When pressure oil is sent to the head of the lift cylinders, lift arm assembly (3) is raised. When pressure oil flows to the rod end of the lift cylinders (1), the lift arm assembly is lowered.
The bucket tilts back when pressure oil is sent to the head end of tilt cylinder (2). The bucket dumps when pressure oil flows to the rod end of the tilt cylinder.
Bucket Positioner Mechanism (Tilt Kickout)
Bucket Positioner Mechanism in KICKOUT Position
The bucket positioner (tilt kickout) mechanism automatically moves the tilt control valve spool and lever from TILT BACK detent position to HOLD position when the bucket gets to the desired digging angle.
Bar assembly (7) is fastened to the rod end of the tilt cylinder. Adjustment of bar assembly (7) changes the contact point of cam (4) with signal roller (6), which changes the digging angle.
Tilt lever (9) is connected to the tilt control valve spool in the oil tank and the tilt control lever in the cab.
When the tilt control lever is moved to TILT BACK detent position and the bucket is between the FULL DUMP position and the preset digging angle, the following movement occurs: the tilt control valve spool moves up from HOLD position into the TILT BACK detent; bar assembly (7) moves out (to the right) as the tilt cylinder is extended.
When cam (4) comes in contact with signal roller (6), lever (5) moves in a counterclockwise direction, causing lever (3) to turn in the opposite direction. Roller (2) causes the levers (1) and (8) to turn in a counterclockwise direction.
When lever (8) comes in contact with tilt lever (9), it causes the tilt control valve spool to move out of the detent. The spring on the spool cause the spool and the tilt control lever to move to HOLD position.
Movement to the HOLD position stops the movement of the bucket at the correct digging angle.
Lift Kickout Mechanism
Lift Kickout Mechanism in KICKOUT Position
The lift kickout mechanism automatically moves the lift control valve spool and lever from RAISE detent position to HOLD position when the bucket gets to the desired dump height.
Signal plate (1) is connected to the lift arm assembly. Adjustment of signal plate (1) changes the contact point of the signal plate with pin (2), which changes the dump height of the bucket.
Lift lever (6) is connected to the lift control valve spool in the oil tank and the lift control lever in the cab.
When the lift control lever is moved to the RAISE detent position, the lift control valve spool moves up from HOLD position into the RAISE detent. The lift cylinders now extend and cause the lift arm assembly to raise.
When the high point (lobe) of signal plate (1) comes in contact with pan (2), levers (3) and (4) turn in a clockwise direction. Rod assembly (5) moves lift lever (6) in a clockwise direction which causes the lift control spool to move out of the detent.
The springs on the spool cause the spool and the lift control lever to move to HOLD position. The movement to the HOLD position stops the movement of the lift cylinders, which stops the movement of the lift arm assembly at the correct dump height.
Tilt Circuit
Tilt Circuit in DUMP Position
Dump Operation
When the engine is running with the control levers in HOLD position, oil pump (15) takes oil from oil tank (19) and sends it first to main relief valve (18), which controls the maximum pressure in the system.
The oil then flows through the lift and tilt control valve because both spools are in HOLD position. From here, the oil flows on to makeup valves (3) and (7), through orifice (6) to oil cooler supply valve (21).
From the supply valve, the oil is sent to oil cooler (20), oil filter (1), filter bypass valve (2), and back to oil tank (19).
When there is a sudden increase (surge) in line pressure, supply valve (21) diverts oil directly to oil filter (1), providing protection to oil cooler (20) against pressure surges.
When the tilt control lever is moved to DUMP position, tilt control valve spool (9) moves to DUMP position and the oil flowing through the lift and tilt control valve is stopped by the spool.
The pump pressure increases, causing load check valve (13) to open. The oil from the pump now flows to the rod end of tilt cylinder (10), causing the cylinder piston and rod to retract.
The Z-bar linkage causes the bucket to dump. The movement of the cylinder piston and rod pushes the oil out of the head end of the cylinder.
The oil flowing out the cylinder flows into the lift and tilt control valve, flows around both spools (8) and (9) on its way back to oil filter (1) and oil tank (19).
When the tilt control lever is released, the spring on the end of tilt control valve spool (9) moves the spool back to HOLD position. The flow of oil to tilt cylinder (10) is stopped and the oil is held in the tilt cylinder by the spool. the cylinder piston stops it movement and the bucket is held in the DUMP position until the control lever is moved again.
Tilt Back Operation
When the bucket is dumped and the tilt control lever is moved to TILT BACK detent position, tilt control valve spool (9) moves to the TILT BACK position and detent (17) is engaged with the spool.
The flow of oil to tilt cylinder (10) is the reverse of bucket dump. The oil pressure increases and causes load check valve (13) to open. The oil now flows to the head end of the tilt cylinder and causes the cylinder piston to extend.
The Z-bar linkage causes the bucket to tilt back. The oil is pushed out of the rod end of tilt cylinder (10) and flows back to the oil tank.
When the tilt control lever is moved to the TILT BACK position, it activates the rackback switch and two-level main relief and solenoid valve for lower level relief setting.
As the bucket moves toward tilt back, the bucket positioner mechanically stops the movement of the bucket at the correct angle to dig.
The bucket positioner moves the valve spool out of detent (17). The springs on tilt control valve spool (9) now cause the spool to move to HOLD position. The oil in tilt cylinder (10) is held by the spool and movement of the cylinder piston stops.
The bucket stays at the correct angle to dig until the tilt control lever is moved again. There is not detent for the tilt control lever when the bucket is moved from the digging angle to TILT BACK position. The control lever must be held in TILT BACK position.
Lift Circuit
Lift Circuit in RAISE Position
Raise Operation
When the engine is running with the control levers in HOLD position, oil pump (15) takes oil from oil tank (19) and sends it first to main relief valve (18) which controls the maximum pressure in the system.
The oil then flows through the lift and tilt control valve because both spools are in HOLD position. From here, the oil flows on to makeup valves (3) and (7), through orifice (6) to oil cooler supply valve (21).
From the supply valve, the oil is sent to oil cooler (20), oil filter (1), filter bypass valve (2), and back to oil tank (19).
When there is a sudden increase (surge) in line pressure, supply valve (21) diverts oil directly to oil filter (1) providing protection to oil cooler (20) against pressure surges.
When the lift control lever is moved to RAISE detent position, lift control valve spool (8) moves to RAISE position and detent (16) engages with the spool.
The pump pressure increases and causes load check valve (12) to open. The oil from the pump now flows to the head end of lift cylinders (11) and causes the cylinder pistons and rods to extend.
The lift arms causes the bucket to raise. The movement of the cylinder pistons and rods pushes oil out of the rod end of the cylinders. The oil flowing from the rod end of the cylinders flows into the lift and tilt control valve, flows around spool (8) on its way back to oil filter (1) and oil tank (19).
When the lift control lever manually moves lift control valve spool (8) out of detent (16) or if the lift kickout mechanically moves the lift control valve spool out of the detent, the springs on the end of the valve spool move the spool back to HOLD position.
In the HOLD position, lift control valve spool (8) stops the flow of oil to the lift cylinders and holds the oil in both ends of the cylinders. The cylinder pistons and rods stop their movement and the lift arms and bucket are held up until the lift control lever is moved again.
Lower Operation
When the lift control lever is moved to LOWER position, lift control valve spool (8) is move to LOWER position.
The oil flow to lift cylinders (11) is the reverse of bucket RAISE. The oil pressure increases and causes load check valve (12) to open. The oil now flows to the rod end of the lift cylinders and causes the cylinder pistons to retract.
The lift arms cause the bucket to lower. The oil is pushed out of the head ends of lift cylinders (11) and flows back to the oil tank.
When the lift control lever is released, the springs on the end of lift control valve spool (8) move the spool back to HOLD position, stopping the movement (lowering) of the bucket.
Float Operation
When the lift control lever is moved to FLOAT detent position, lift control valve spool (8) is moved to FLOAT position and detent (16) engages with the spool.
The head ends and rod ends of lift cylinders (11) are all open to pump oil and each other. Outside forces control the movement of the cylinder pistons. As the cylinder pistons move, any extra oil needed comes from oil pump (15) or makeup valve (3).
When the engine is off, the bucket can be lowered by use of the FLOAT position. The weight of the lift arms and bucket causes the lift cylinders to retract.
The lift control lever must be manually moved out of the FLOAT detent position. There is no kickout for the FLOAT position.
Third Circuit (Optional)
Third Circuit with Front or Rear Attachments (In OPEN or RAISE Position)
Open or RAISE Operation
When the engine is running with the control levers in HOLD position, oil pump (15) takes oil from oil tank (19) and sends it first to main relief valve (18), which controls the maximum pressure in the system.
The oil then flows through the third control valve and the lift and tilt control valve because all three spools are in HOLD position. From here, the oil flows on to makeup valves (3) and (7), through orifice (6) to oil cooler supply valve (21).
From the supply valve, the oil is sent to oil cooler (20), oil filter (1), filter bypass valve (2), and back to oil tank (19).
When there is a sudden increase (surge) in line pressure, supply valve (21) diverts oil directly to oil filter (1) providing protection to oil cooler (20) against pressure surges.
When the third control lever is moved to OPEN position for the multi-purpose bucket or RAISE position for the ripper, third control valve spool (22) moves to OPEN or RAISE position.
The flow through the third control valve is stopped and the pressure increases at load check valve (25). The load check valve opens and lets oil flow to the rod end of attachment (multi-purpose bucket or ripper) cylinders (24).
The cylinder pistons retract and cause the multi-purpose bucket to OPEN or the ripper to RAISE. The movement of the cylinder pushes the oil out of the head end of the attachment cylinders.
The oil flowing out of the head end of the attachment cylinders flows into the third control valve, around the third control valve spool (22) and on to the lift and tilt control valve. The oil flows around spools (8) and (9) on its way back to oil filter (1) and oil tank (19).
When the third control lever is releases, the spring on the end of the third control valve spool (22) moves the spool back to HOLD position. The cylinder piston is stopped and the multi-purpose bucket stays open or the ripper stays raised until the control lever is moved again.
Close or Lower Operation
When the third control lever is moved to CLOSE or LOWER position, third control valve spool (22) is moved to CLOSE or LOWER position.
The oil flow to attachment cylinders (24) is the reverse of OPEN or RAISE. Load check valve (25) opens and oil flows to the head end of the attachment cylinders.
The cylinder pistons extend and cause the multi-purpose bucket to CLOSE or the ripper to LOWER. The oil is pushed out of the rod ends of attachment cylinders (24) and flows back to the oil tank.
When the third control lever is released, third control valve spool (22) again flows back to HOLD position.
Fourth Circuit (Diverter Valve)
Fourth Circuit with Front or Rear Attachments (in Ripper Control, RAISE Position)
The flow of oil in the fourth circuit is the same as the third circuit except for the addition of diverter valve (26) between third control valve spool (22) and the attachment cylinders.
The fourth circuit has both a multi-purpose bucket and a ripper for a total of four cylinders.
Multi-purpose Bucket Operation
When the fourth control lever is moved to MULTI-PURPOSE BUCKET CONTROL, the selector spool of diverter valve (26) opens passage to multi-purpose bucket cylinders (27) and closes passages to ripper cylinders (24).
The multi-purpose bucket can now be operated by the third control lever.
Ripper Operation
When the fourth control lever is moved to RIPPER CONTROL, the selector spool of diverter valve (26) opens passages to ripper cylinders (24) and closes passages to multi-purpose bucket cylinders (27).
The ripper can now be operated by the third control lever.