TUBE AS 2926418 - Caterpillar

Note: Valve sections (1), (2), (3), (4), (5), (6), (7), and (8) have two stroke limiter screws (17). Valve sections (4), (5), (6), (7), and (8) have two signal limiter valves (11) and two line relief valves (18) .Pressurized oil from the hydraulic oil pump flows into the main control valve through port (12). The hydraulic oil pump controls the oil pressure to the main control valve. The main relief valve protects the main control valve by preventing pressure spikes. Adjustment screw (13) controls the pressure setting of the main relief valve. The oil returns to the machine through return port (16) .The valve spools in the main control valve are controlled by solenoids. The solenoids control the flow of pilot pressure oil to the ends of the valve spools. The pilot pressure oil is generated inside the main control valve by pilot pressure reducing valve (15). Pilot relief valve (10) limits the maximum pilot pressure to the valve sections. The flow of oil from valve sections (1) and (2) is controlled by proportional solenoids. The flow of oil from the other valve sections is controlled by on/off solenoids.Line relief valves (18) protect the cylinders and hydraulic oil lines from damage. When an external load acts on a cylinder, the oil pressure in the circuit increases. When the pressure in the circuit exceeds the relief valve pressure setting, the relief valve opens. The oil in the circuit returns to the hydraulic oil tank on the machine through port (14).
Illustration 2 g00647639
Section View of a Typical Valve Section in the Main Control Valve (HOLD position) (19) Light emitting diode (proportional valves) (20) Connector (21) Position transducer (Proportional valves) (22) Port to hydraulic components (23) Valve spool (24) Port to hydraulic components (25) Lever (26) Stroke limiter screw (27) Stroke limiter screw (A) Lever position (B) Lever positionProportional Valve Sections
The speed of the feed rollers is controlled by the amount of oil flow to the feed roller motors. The flow of oil to the motors is varied by controlling the stroke of valve spool (23). By increasing the stroke of the valve spool from the HOLD position, more oil will flow to the motors.
Illustration 3 g00743865
Electrical Schematic of Proportional Valve SectionPin "1" of connector (20) receives a constant 24 volt signal. When the operator activates a control to move the feed rollers forward, a pulse width modulated signal is sent to pin "2" of the connector.Pilot pressure oil then flows to the left side of valve spool (23). The valve spool moves to the right. Position transducer (21) measures the location of the valve spool. The measuring and control system uses the signal from the transducer to move the valve spool to the correct position.When the signal voltage is 12 V, valve spool