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| Illustration 1 | g01029129 |
Hydraulic Components (1) Hydraulic tank filter (2) Hydraulic tank (3) Implement pump (4) Steering pump (5) Apron cylinder (6) Sequence and pressure control valve (apron) (7) Carry-check and quick-drop valves (8) Bowl cylinders (9) Ejector cylinder (10) Ejector valve (speed change) (11) Main control valve | |
The following manual covers the system operation of all the hydraulic implements for the 631G and the 637G Wheel Tractor-Scrapers.
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| Illustration 2 | g00770395 |
Right Rear Side of Tractor (3) Implement pump (4) Steering pump | |
The implement hydraulic system includes a pilot hydraulic system and a main hydraulic system. The pilot system controls the functions of the main control valve (11). The pilot hydraulic system is controlled by the implement electronic control system.
The main hydraulic system consists of the implement (3) and steering pump (4), the implement control valve (11), and the implement cylinders. The 631G/637G Wheel Tractor-Scrapers are equipped with an ejector cylinder (9), two bowl cylinders (8), and an apron cylinder (5).
The hydraulic pump is a two-section gear pump. The two-section pump includes the implement pump (3) and the steering pump (4). The two-section pump is installed on the transfer gear case housing. The pump supplies oil to main control valve (11) .
The pilot hydraulic system consists of the cushion-hitch pump (31), which provides the pilot oil supply, and the shuttle valves, the pressure reducing valve, and pilot actuator valves.
The pilot solenoid and pressure reducing valve directs oil from the cushion-hitch pump (31) to the pilot actuators of the implement control valve. The pilot solenoid and pressure reducing valve also reduces the pressure of oil from the cushion-hitch pump to pilot pressure.
The implement control valve (11) contains three valve spools which direct implement pump oil to the ejector cylinder (9), bowl cylinders (8), and apron cylinder (5). Main control valve (11) is electronically controlled by the implement control lever in the operator's compartment. When the implement control lever is moved from the HOLD position, an electrical signal is sent from the Implement ECM to a pilot actuator solenoid. The solenoids activate the pilot control actuators which direct pilot oil in order to shift the valve spools in the implement control valve.
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| Illustration 3 | g00770435 |
Left Rear Side of the Tractor (11) Main control valve | |
In the HOLD position, both solenoids for the pilot control actuator are de-energized. When both solenoids are de-energized, the pilot spools direct pilot oil to the ends of the main spool. The pilot pressure at each end of the main spool, and the force of the centering springs cause the main spool to be centered in the control valve. The centering springs and retainers help stabilize the movement of the main spool. The stabilizing springs dampen the movement of the pilot spools by holding the pilot spools in contact with the feedback springs.
When main control valve (11) is in the HOLD position, pump oil flows through main control valve (11) and through filter (1) in hydraulic tank (2). Oil filter housing (1) has a bypass valve. The oil will flow through the inlet passage. The oil will then flow through the filter element before the oil flows to hydraulic tank (2). The filter element removes debris from the oil before the oil flows to hydraulic tank (2). When the filter element becomes blocked, flow of oil will be restricted. Restriction of oil flow causes an increase in pressure on the outside of the filter element. High oil pressure opens the bypass valve. The bypass valve will allow unfiltered oil to pass to hydraulic tank (2).
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| Illustration 4 | g00788007 |
Front Right Side of the Tractor (1) Hydraulic tank filter (2) Hydraulic tank (12) Breaker relief valve | |
When the valve stems in main control valve (11) are in the HOLD position, pump oil flows through main control valve (11) and through filter (1) in hydraulic tank (2). Oil filter housing (1) has a bypass valve. The oil will flow through the inlet passage. The oil will then flow through the filter element before the oil flows to hydraulic tank (2). The filter element removes debris from the oil before the oil flows to hydraulic tank (2). When the filter element becomes blocked, flow of oil will be restricted. Restriction of oil flow causes an increase in pressure on the outside of the filter element. High oil pressure opens the bypass valve. The bypass valve will allow unfiltered oil to pass to hydraulic tank (2) .
Breaker relief valve (12) is located on hydraulic tank (2). Breaker relief valve (12) opens when the tank pressure reaches approximately 69 kPa (10 psi).
Cushion-Hitch Hydraulic System
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| Illustration 5 | g00932489 |
(13) Bracket assembly (14) Link assembly (two) (15) Accumulator (two) (16) Load cylinder (17) Leveling valve (18) Hitch assembly | |
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| Illustration 6 | g00932493 |
(17) Leveling valve (19) Line to rear accumulator (20) Line to front accumulator (21) Solenoid valve (cushion-hitch) (22) Line to head end of load cylinder (23) Drain line (24) Line to rod end of load cylinder (25) Supply to leveling valve (26) Leaf spring (27) Yoke assembly (28) Drain line | |
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| Illustration 7 | g00932501 |
(25) Pressure line from the outlet of the cushion-hitch pump (29) Drain line from the cushion-hitch pump (30) Supply line to cushion-hitch pump (31) Cushion-hitch pump | |
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| Illustration 8 | g00932509 |
(32) Cushion-hitch control switch | |
The cushion-hitch is the connection between the tractor and the scraper. The cushion-hitch gives smooth vertical movement to the machine. Operation of the cushion-hitch is not needed in every type of machine operation. Operation of the cushion-hitch can be turned on and off in the operator's station with cushion-hitch control switch (32) .
The hydraulic system for the cushion-hitch has a leveling valve (17), a load cylinder (16), two accumulators (15), and cushion-hitch pump (31). The cushion-hitch pump gets oil from the same hydraulic tank that is common to the rest of the tractor-scraper hydraulic systems. There is a filter in drain line (29) that prevents large particles from contaminating the hydraulic oil.
The cushion-hitch is made up of bracket assembly (13), two link assemblies (14), and hitch assembly (18). Bracket assembly (13) is connected to the scraper. Hitch assembly (18) is connected to the tractor. Link assemblies (14) connect bracket assembly (13) and hitch assembly (18). The rod end of load cylinder (16) is connected to bracket assembly (13). The head end is connected to hitch assembly (18). In the LOCKDOWN position, bracket assembly (13) and hitch assembly (18) are held in contact by oil in the rod end of load cylinder (16). In the CUSHION RIDE position, oil in the head end of the load cylinder lifts bracket assembly (13). The oil also lifts the weight of the scraper off the hitch assembly (18) and the tractor.
Cushion-hitch control switch (32) is the on/off control for CUSHION RIDE.
When the machine is in operation and switch (32) is on, the oil from hydraulic pump (31) fills the area below the pistons of accumulators (15). The oil also goes to the head end of load cylinder (16). As the oil enters the cylinder, the rod is extended. The front of the scraper is now supported by a cushion of oil.
Yoke assembly (27) connects leveling valve (17) to leaf spring (26). The leaf spring is connected to the lower link assembly (14). When bracket assembly (13) gets to the correct height above hitch assembly (18), the leaf spring and the yoke assembly cause the leveling valve to stop pump flow to the head end of the load cylinder. The accumulator is still connected to the load cylinder in order to provide the cushion ride. At this time, hydraulic pump (31) is at minimum output.
When switch (32) is off, the oil in the head end of the load cylinder (16) goes back to the hydraulic tank. Pump oil still goes to the accumulators and to the rod end of the load cylinder. The rod of the load cylinder is retracted. Bracket assembly (13) lowers until contact is made with hitch assembly (18). The pump oil in the rod end of the load cylinder keeps the bracket assembly in contact with the hitch assembly.
When the engine is shut off and the key switch is off, the pump oil in the head end of the load cylinder and the oil in the accumulators is released through leveling valve (17). The front of the scraper again lowers onto the tractor.
Push-Pull Hydraulic System
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| Illustration 9 | g01027482 |
(31) Cushion-Hitch pump (33) Push-Pull solenoid valve (34) Manifold for the solenoid valve (35) Valve spool (36) Bail (37) Bail cylinder (38) Push-Pull control valve (39) Line to the cushion-hitch valve (40) Line to solenoid and the pressure reducing valve | |
The push-pull hydraulic system gets oil from cushion-hitch pump (31). The oil from cushion-hitch pump (31) is sent to manifold (34). The oil is then sent to push-pull control valve (38) .
Solenoid valve (33) is used to control the push-pull hydraulic system. Valve spool (35) is moved from the normal spring loaded position when the signal oil from solenoid valve (33) is sent to valve spool (35). The solenoid valve can be switched in two positions by the operator.
The operator can move the switch into the following two positions:
- Push the trigger switch on the joystick control in order to enable BAIL RAISE.
- Push the trigger switch on the joystick control in order to enable BAIL LOWER.
When the ignition switch is in the OFF position, the engine is not running and there is no output oil from cushion-hitch pump (31). Solenoid valve (33) will be in the BAIL LOWER position and valve spool (35) is in the BAIL RAISE. Solenoid valve (33) and valve spool (35) are in these positions whenever the engine is not running. Solenoid valve (33) and valve spool (35) cannot be moved until the engine is started.
When the engine is started, the oil from cushion-hitch pump (31) is sent to the following components: solenoid valve (33), push-pull control valve (38), solenoid and pressure reducing valve and the cushion-hitch leveling valve. The oil is sent to solenoid valve (33) in order to provide pilot oil to valve spool (35). The oil is sent to valve spool (35) in order to enable the BAIL LOWER. When the oil is sent to valve spool (35) the oil is also sent to the cushion-hitch leveling valve and the cushion-hitch accumulators. The cushion-hitch accumulators are recharged by the oil from cushion-hitch pump (31). When the cushion-hitch accumulators reach the pressure setting of the pressure compensator valve, cushion-hitch pump (31) will reduce the flow to the minimum output. Refer to System Operation, "Piston Pump (Cushion-Hitch)". The information is in this manual. Oil goes through push-pull control valve (38) in order to control bail (36).
Bail Lower
Solenoid valve (33) is in the BAIL LOWER position. Pressure in the supply side of solenoid valve (33) is the same pressure at the end of valve spool (35). Valve spool (35) shifts when pump pressure reaches about 400 kPa (58 psi). When pump pressure reaches about 700 kPa (101 psi), valve spool (35) is fully shifted to BAIL LOWER position.
Bail Raise
When the trigger switch is pushed to move the bail to the BAIL RAISE position, solenoid (33) moves to the BAIL RAISE position. Oil from cushion-hitch pump (31) flows from the pump to solenoid valve (33). The oil passes through manifold (34) and flows to the tank through push-pull control valve (38). Oil does not flow to valve spool (35). The spring force pushes valve spool (35) to the BAIL RAISE position. Pump oil enters push-pull control valve (38) and flows to the rod end of bail cylinder (37). Head end oil flows through control valve (38) and returns to the tank.