Elevator Circuit Neutral Position
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| Illustration 1 | g03646542 |
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Elevator circuit neutral position (1) Implement ECM (2) Elevator motor (3) Flushing relief valve (4) Flushing valve (5) Motor case drain filter (elevator motor) (6) Motor cross-over relief valve (high pressure) (7) Motor cross-over relief valve (high pressure) (8) Joystick thumb wheel (9) Elevator pump (10) Pressure control solenoid (elevator forward) (11) Control spool (12) Actuator pistons (13) Pilot valve (14) Pressure control solenoid (elevator reverse) (15) Pressure override relief valves (forward direction) (16) Case drain filter (elevator pump) (17) Pump cross-over relief valve (high pressure) (18) Pump cross-over relief valve (high pressure) (19) Check valve (20) Pressure override relief valves (rev direction) (21) Charge relief valve (22) Elevator charge pump filter (23) Cold start relief valve (24) Charge pump (A) Elevator motor case drain (B) Elevator forward direction closed-loop line (C) Elevator reverse direction closed-loop line (D) Elevator pump case drain (E) Charge pump supply line | |
The elevator system is a closed loop system. The system operates off a self contained oil supply. A small amount of oil is drawn out of the system through the elevator pump case drain line (D) and elevator motor case drain line (A) as the system operates. This oil is returned to the hydraulic tank in order to cool. The oil that is returned to the hydraulic tank is replaced with cooler oil that is drawn into the elevator system from the hydraulic tank. The charge pump (24) is mounted on the back of the elevator pump (9). The charge pump supplies the elevator circuit with oil from the hydraulic tank. The charge pump is supplied oil from the hydraulic tank through the charge pump supply line (E). the charge pump replenishes the elevator system with oil that is returned top the hydraulic tank from the pump and motor case drains.
Elevator Circuit Forward Position
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| Illustration 2 | g03646547 |
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Elevator circuit forward position (1) Implement ECM (2) Elevator motor (3) Flushing relief valve (4) Flushing valve (5) Motor case drain filter (elevator motor) (6) Motor cross-over relief valve (high pressure) (7) Motor cross-over relief valve (high pressure) (8) Joystick thumb wheel (9) Elevator pump (10) Pressure control solenoid (elevator forward) (11) Control spool (12) Actuator pistons (13) Pilot valve (14) Pressure control solenoid (elevator reverse) (15) Pressure override relief valves (fwd direction) (16) Case drain filter (elevator pump) (17) Pump cross-over relief valve (high pressure) (18) Pump cross-over relief valve (high pressure) (19) Check valve (20) Pressure override relief valves (rev direction) (21) Charge relief valve (22) Elevator charge pump filter (23) Cold start relief valve (24) Charge pump (A) Elevator motor case drain (B) Elevator forward direction closed-loop line (C) Elevator reverse direction closed-loop line (D) Elevator pump case drain (E) Charge pump supply line | |
When the operator holds the thumb roller on the joystick to the left, the elevator will rotate in the forward direction (load). The thumb roller sends a 500 Hz PWM signal to the Implement Control ECM at connector contact J2-26. The ECM sends a signal to the pressure control solenoid (elevator forward) (10) through connector contact J1-67. The pressure control solenoid (elevator forward) (10) current command will be controlled relative to the speed setting. When the operator quickly moves the elevator thumb roller fully to the left and allows it to spring back to the NEUTRAL position, the elevator will continuously rotate in the forward direction (load). The continuous elevator motion will be deactivated by moving the thumb roller out of the NEUTRAL position.
When pressure control solenoid (elevator forward) (10) is activated, the solenoid moves control spool (11) to the right. This movement of control spool supplies pressure to the pilot valve. Pilot valve (13) moves to the right. When pilot valve (13) moves to the right, the pilot valve signals actuator pistons (12) to move. That actuator piston movement then moves the swash plate. The movement of the swashplate upstrokes the pump and causes oil to flow through passage (B). As the pump works, port pressure in line (B) increases, the forward speed of the elevator motor increases also.
Note: The elevator thumb roller will only be used to select the direction of elevator rotation. The rotating velocity will be adjusted by using elevator speed increment and decrement buttons.
Elevator Circuit Reverse Position
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| Illustration 3 | g03646554 |
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Elevator circuit reverse position (1) Implement ECM (2) Elevator motor (3) Flushing relief valve (4) Flushing valve (5) Motor case drain filter (elevator motor) (6) Motor cross-over relief valve (high pressure) (7) Motor cross-over relief valve (high pressure) (8) Joystick thumb wheel (9) Elevator pump (10) Pressure control solenoid (elevator forward) (11) Control spool (12) Actuator pistons (13) Pilot valve (14) Pressure control solenoid (elevator reverse) (15) Pressure override relief valves (fwd direction) (16) Case drain filter (elevator pump) (17) Pump cross-over relief valve (high pressure) (18) Pump cross-over relief valve (high pressure) (19) Check valve (20) Pressure override relief valves (rev direction) (21) Charge relief valve (22) Elevator charge pump filter (23) Cold start relief valve (24) Charge pump (A) Elevator motor case drain (B) Elevator forward direction closed-loop line (C) Elevator reverse direction closed-loop line (D) Elevator pump case drain (E) Charge pump supply line | |
When the operator holds the thumb roller on the joystick to the right, the elevator will rotate in the reverse direction. The thumb roller sends a 500 Hz PWM signal to the Implement Control ECM at connector contact J2-26. The ECM sends a signal to the pressure control solenoid (elevator reverse) (14) through connector contact J1-68. The pressure control solenoid (elevator reverse) (14) current command will be controlled relative to the speed setting. When the operator quickly moves the elevator thumb roller fully to the right and allows it to spring back to the NEUTRAL position, the elevator will continuously rotate in the reverse direction (load). The continuous elevator motion will be deactivated by moving the thumb roller out of the NEUTRAL position.
When pressure control solenoid (elevator reverse) (14) is activated, the solenoid moves control spool (11) to the left. This movement of control spool supplies pressure to the pilot valve. Pilot valve (13) moves to the left. When pilot valve (13) moves to the left, the pilot valve signals actuator pistons (12) to move. That actuator piston movement then moves the swash plate. The movement of the swashplate upstrokes the pump and causes oil to flow through passage (B). As the pump works, port pressure in line (B) increases, the reverse speed of the elevator motor increases also.
Note: The elevator thumb roller will only be used to select the direction of elevator rotation. The rotating velocity will be adjusted by using elevator speed increment and decrement buttons.
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| Illustration 4 | g02580123 |
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(1) Springs (mechanical zero)
(2) Actuator pistons (3) Swashplate (4) Electro-hydraulic control | |
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| Illustration 5 | g02580120 |
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Cross Section of the Elevator Pump (3) Swashplate (4) Electro-hydraulic control (5) Driveshaft (6) Retainer (7) Pistons (nine) (8) Barrel (9) Port plate (10) Hydrostatic bearings (two) | |
When the engine is running, pump driveshaft (5) turns at engine speed. Driveshaft (5) rotates barrel (8) with nine working pistons (7). The ends of the slipper are in the shape of a ball that fits into the pistons (7). The slipper is held against the swashplate by retainer (6). The slipper slides on a thin film of oil on swashplate (3). Swashplate (3) does not turn. There are hydrostatic bearings (10) on each side of swashplate (3). Swashplate (3) rests on the hydrostatic bearings (10). The hydrostatic bearings (10) allow swashplate (3) to pivot in the pump housing. By pivoting, swashplate (3) changes angles. This change in the angle results in a change of the pump displacement. Swashplate (3) is positively held in no-flow position by the springs (1) at the actuator pistons (2). At the moment of starting, the pump runs in mechanical neutral position with no displacement. When the pump is driven and proportional solenoids (18) are not energized, swashplate (3) is held in hydraulic neutral position. In the central position pilot valve (17) connects both actuator pistons (2) with the control (servo) pressure with no displacement. In the neutral position of the swashplate (3) there is no axial stroking of the actuator pistons (2) therefore there is no pump delivery.
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| Illustration 6 | g02580121 |
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(4) Electro-hydraulic control
(11) Combination high-pressure relief and boost check valve (12) Combination high-pressure relief and boost check valve (13) Charge pump (14) Boost pressure relief valve (15) Pre-loading valve | |
The pump shaft drives not only the rotating group of the main pump but also the charge pump (13). This draws hydraulic oil from the hydraulic tank and sends the oil into the HPV pump through the port F. In the pump the oil passes the combination high-pressure relief and boost check valves (11) and (12), flows on to the two high-pressure ports and then to the electro-hydraulic control (4). The excess oil not required to make up for leakage purges off at the boost pressure relief valve (14). This maintains the set boost pressure for the low-pressure return side of the main circuit and the control pressure. Depending on the direction of swashplate (3) tilt either port P or S carry high pressure, at the same time closing the respective combination high-pressure relief and boost check valves (11) and (12). Boost oil can only be fed in on the low-pressure line. In case high pressure exceeds the set max. value of the combined boost and high-pressure relief valve the surplus spills over through the connecting channel to the opposite boost valve and into the low-pressure line (cross-over relief function).
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| Illustration 7 | g02580119 |
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(16) Slave piston
(17) Pilot valve (18) Proportional solenoids (19) Proportional valves | |
With the implement ECM the pump flow rate and flow direction are controlled via the energized proportional solenoid. The electro-hydraulic control (4) uses pilot valve (17) for actuation which is integrated in electro-hydraulic control (4). Pilot valve (17) is moved with the actuation piston (2) which normally is held in the middle position by two springs. Pilot valve (17) and actuating pistons (2) are mechanically linked to each other by a lever. Control of the actuating piston (2) is realized with a control pressure selected at proportional solenoids (18), which determines both flow rate and flow direction. The maximum pressure override device reduces pump delivery upon reaching the maximum pressure. While maintaining the system pressure, only a small residual flow passes the high-pressure relief valves. This helps to optimize energy consumption and thermal balance of the system. Propulsion drives with override device may show a different behavior than without.
Pump driveshaft (5) turns barrel (8). When swashplate (3) is at an angle, pistons (7) move in and out of the barrel. Pistons (7) move in and out of barrel (8) as pistons (7) follow the angle of swashplate (3). Swashplate (3) is shown at the maximum angle. As pistons (7) move out of barrel (8), pistons (7) pull oil from the return flow side of the closed loop. The oil flows from the return flow side through the pump inlet and port plate (9) into the piston cylinder. As barrel (8) continues to turn, pistons (7) are moved into barrel (8). This compresses the oil. Pistons (7) push the oil from the piston cylinder through port plate (9) to the pump outlet. Then, the oil flows to the elevator motor.
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| Illustration 8 | g03485536 |
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(1) Shuttle valve
(1A) Conical seat (1B) Shuttle valve piston (2) A-port (3) B-port (4) Housing (5) Discharge valve | |
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| Illustration 9 | g03485642 |
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(1) Shuttle valve
(4) Housing (5) Discharge valve (6) Cylinder block (7) Working piston | |
The flow of oil coming from the hydraulic pump is delivered to the high-pressure connection port (2) and (3) of the hydraulic motor. The pressure fluid passes through the port in the port plate housing and cylinder block (6) on to the end face of piston (7). This displaces piston (7), and setting the hydraulic motor in rotary motion. The direction of rotation, forward or reverse, is determined by whether the pressure oil is admitted into high-pressure connection port (2) or port (3): - Flow in at port (2): Direction of rotation reverse - Flow in at port (3): Direction of rotation forward.
Shuttle valve (1) is located in housing (4). As long as both high-pressure lines are without load and only have boost pressure (for example, when the pump is in the neutral position), the two pistons of shuttle valve (1) are in the spring-centered position. Operating fluid is unable to flow to the discharge valve (5) from either the high-pressure connection port (2) or the high-pressure connection port (3). However, if high pressure builds up, for example on port (2) side, then this high pressure displaces shuttle valve piston (1B), driving shuttle valve piston (1B) towards the low-pressure connection port (3). The conical seat (1A) on shuttle valve piston (1B) acts as a stop. Thereby simultaneously preventing high-pressure fluid from being transferred out of shuttle valve piston (1B) spring chamber towards discharge valve (5). A dose of oil flow is discharged from the shuttle valve piston (1B) spring chamber via discharge valve (5) into motor housing (4). When, return oil flow pressure from the pump drops below