Elevator Reverse (No Illustration)

SCHEMATIC OF HYDRAULIC SYSTEM FOR ELEVATOR FAST FORWARD

TM-5-3805-260-24 Scraper Tractor: Elevating Self-Propelled 11 Cubic Yard Sectionalized and Nonsectionalized Manual
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TM 5-3805-260-24 adds to the pump oil in line (10) to elevator control valve (12). With the engine running at high rpm and the valve spool in control valve (12) in FORWARD position (C), the oil from pump (22) goes through line (7) to run elevator hydraulic motor (1) forward at high speed. The oil from the elevator motor goes through line (8), control valve (12) and through return oil line (13) into filter and tank (19). Move the elevator speed lever to the LOW position and the valve spool in elevator speed valve (6) moves to LOW SPEED position (L). Now, the oil from the cover end of pump (22) goes through speed valve (6) and goes into return oil line (13) to the tank. With only oil from one section of pump (22) to elevator motor (1), the elevator runs at a slow speed. The elevator control lever must be moved to the HOLD position to move the elevator valve spool to HOLD position (B). With the valve spool in HOLD position, the oil from pump (22) goes through control valve (12), through return oil line (13) into filter and tank (19). Elevator Reverse (No Illustration) The elevator control lever is held in the REVERSE position by the detent balls in elevator control valve (12). With the valve spool in REVERSE position (A), the oil from pump (22) goes through control valve ( 12) and through line (8) to elevator motor (1) to run the elevator in reverse. The oil from the elevator goes through line (7), through control valve (12) and through return oil line (13) into the filter and tank (19). The reverse speed of the elevator is controlled by the rpm of the engine and the position of the elevator speed lever connected to the valve spool in elevator speed valve (6). HIGH SPEED position (H) lets the oil from the cover end section of pump (22) add to the oil from the drive end section of the pump in line ( 10) to the elevator motor. The speed valve stem in LOW SPEED position (L) lets the oil from the cover end section of pump (22) go through return oil line (13) to the tank. Now, only the oil from the drive end section of the pump goes through line (10) and to the elevator motor. Move the control lever to the HOLD position. This moves the elevator valve spool to HOLD position (B) and stops the elevator. ELEVATOR VALVES Control Valve The location of the elevator control valve is just in front of transmission (2), near the left side of the machine. The flexible cable from the control lever goes under the scraper hitch and is connected to valve spool (I) in the elevator control valve. ELEVATOR CONTROL VALVE 1. Valve spool (in control valve). 2. Transmission. Detent balls, in the control valve, keep valve spool (1) in any of the three positions for the valve spool. When the valve spool is held in FORWARD position (C), the oil from the pump goes in through inlet (6), opens check valve (7),- goes through the check valve and through outlet (4) that connects with an oil line to the elevator hydraulic motor. ELEVATOR CONTROL VALVE (HOLD POSITION) 1. Valve stem. 3. Outlet to tank. 4. Outlet to motor (for reverse). 5. Outlet to motor (for forward). 6. Inlet from pump. 7. Check valve. A. REVERSE position. B. HOLD position. C. FORWARD position. With valve spool (1) in HOLD position (B), the pump oil through inlet (6) does not get any pressure to open check valve (7) because the oil goes out through outlet (3) and to the tank. The spring in check valve (7) keeps it closed, when there is no pump oil pressure in the control valve, and the oil in the lines to the elevator motor is stopped. The hydraulic motor can not be turned when oil is stopped in the lines to the motor. With valve spool (1) in REVERSE position (A), the pump oil through inlet (6) opens check valve (7) and then goes through outlet (5) that connects with an oil line to the elevator motor. 4-20

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