STRAINER-SUCTION 3633445 - Caterpillar

Illustration 2 g02731251
Main control valve
(1) Main control valve
(2) Bucket control valve
(3) Boom control valve
(4) Right travel control valve
(5) Left travel control valve
(6) Stick control valve
(7) Swing boom control valve
(8) Auxiliary control valve
(9) Priority valve
(10) Swing control valve
(11) Blade control valve
(14) Relief valve (main pump)
(15) Relief valve (main pump)
(19) Relief valve (secondary pump)
(20) Line relief valve (typical)
(P1) Inlet port (main pump)
(P2) Inlet port (main pump)
(P3) Inlet port (secondary pump)
(T1) Return port
(T2) Return port There are nine major control valves in the main control valve. Oil is directed from the pumps to these valves in the following manner:Part of the oil flow from main pump (23) enters the main control valve through inlet port (P1). Then the oil flows through center bypass passage (13) to the right travel control valve (4), boom control valve (3) and bucket control valve (2).Part of the oil flow from main pump (23) enters the main control valve through inlet port (P2). Then the oil flows through center bypass passage (17) to the left travel control valve (5), stick control valve (6), swing boom control valve (7) and auxiliary control valve (8).Oil from the secondary pump (22) enters through inlet port (P3). The oil is directed to blade control valve (11), swing control valve (10) and priority valve (9).The main control valve performs the following functions:Control in the NEUTRAL position - When the joysticks are in the NEUTRAL position, oil passes through the center bypass passages in the main control valve. The oil then flows to the return port (T1) and return port (T2) to the hydraulic tank.Operation of individual valves - Individual valves are used to actuate the implement cylinders. These valves are also used to actuate the hydraulic motors. Pump oil is supplied to the valves through the center bypass passages and the parallel feeder passages.Prevention of leakage and drift in cylinders and motors - This function is performed by using load check valves. The load check valves prevent oil pressure in an implement circuit that is higher than the pump pressure to lessen. This action prevents undesired motion from an implement circuit.Limitation of circuit pressure - This function is performed by using relief valves.Flow priority - The priority control valve enables the machine to operate multiple implement functions at one time. When the machine is operating a combination of one or more implement circuits, the priority valve shifts and supplies secondary pump flow to the boom, stick and bucket circuits. When no implement circuit is being operated, the secondary pump oil flow is supplied to the attachment control valve in addition to the blade and swing circuits.Individual Valve Operation
Note: The bucket control valve is used as an example in order to describe the operation of the individual control valves.
Illustration 3 g02731261
Bucket control valve (CLOSE position)
(2) Bucket control valve (spool)
(12) Parallel feeder passage
(13) Center bypass passage
(16) Return passage
(25) Port B
(26) Port A
(27) Pilot port B1
(28) Pilot port A1 When the pilot control valve is moved to the BUCKET CLOSE position, pilot oil flows to port