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A. ROTARY AIR VALVE/FEED ROLL
The front section of the tandem pump feeds oil to the rotary air valve motor through a solenoid
valve. The solenoid valve is an open-center spool valve with built in relief set at 2100 psi (14500
kPa). The spool in the valve is spring-centered and is moved by actuating a 12 VDC solenoid on
either end of the spool. Spool movement can be checked manually by pressing the button located
at either end. This action energizes a solenoid that produces high-pressure oil at the work port
away from that solenoid, thus, energizing the bottom solenoid on the valve that then channels oil
from the pump to the top work port on the valve. This is forward position on the rotary air valve
motor. Energizing the top solenoid produces reverse rotation on the rotary air valve motor.
B. FLOOR (DRAG CONVEYOR)/FEED ROLL
The rear section of the tandem pump feeds oil to the floor motor through a dump valve system.
The floor speed control valve, located on the conveyor leg next to the control box, is actually three
valves in one manifold: a relief valve set at 1,850 psi (12,800 kPa) to protect this circuit, a 12 VDC
normally open solenoid dump valve, and a flow control valve.
Oil entering this manifold flows back to the tank. Energizing the solenoid valve forces oil through
the flow control valve where a certain amount flows to the feed roll hydraulic motor, causing the roll
to rotate. Turning the adjustment knob on top of the valve increases or decreases the amount of
oil going to the feed roll motor and, in turn, increases or decreases the speed. The floor is chain-
driven off the feed roll motor.
SUBSYSTEM 3: HYDRAULIC CONTROL SYSTEM
The hydraulic control system is an electrical system that controls the ON/OFF function of the con-
veyor motor and the rotation direction of the rotary air valve motor. This 12 VDC system runs off
the engine electrical system. It is a self-contained PLC system located in the control box, which
controls the solenoid valves in the hydraulic system.
When the START button is pushed, the forward solenoid on the solenoid valve is energized, start-
ing the rotary air valve and the drag conveyor, but only if the conveyor toggle switch is in the ON
position. As material drops into the top of the rotary air valve, the pressure to turn the rotary air
valve varies. If the pressure reaches the high-pressure relief valve threshold in the solenoid con-
trol valve, the oil is channeled through the relief valve to the hydraulic tank. In the forward work
line is a normally open pressure switch. When the pressure in the work line exceeds the pressure-
switch setting, the switch then closes and triggers the auto-reverse sequence.
During auto-reverse, the rotary air valve reverses direction for approximately 1 second. While in
reverse, it also cuts power to the floor, shutting it OFF. At the end of the auto-reverse cycle, power
is restored to the forward solenoid, putting the rotary air valve back into forward.
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