CONTROL GP-JOYSTICK 4574637 - Caterpillar

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Hydraulic schematic for return circuit (1) Swing motor (2) Travel motors (3) Drain line (4) Makeup line (5) Orifice (6) Return passage (7) Drain line (8) Center bypass passage (9) Main control valve (10) Center bypass passage (11) Orifice (12) Return line (13) Drain line (14) Case drain filter (15) Slow return check valve (16) Drain line (17) Oil cooler (18) Return filter (19) Return line (20) Bypass check valve (21) Return line (22) Hydraulic tank (23) Front pump (24) Rear pump (25) Pilot pumpIntroduction
The oil from front pump (23) and rear pump (24) enters the main control valve. The oil then flows to return passage (6) in one of the following manners.There is no load on the machine.
Front pump oil flows through center bypass passage (10) and orifice (11) to return passage (6) .
Rear pump oil flows through center bypass passage (8), orifice (5) and return line (12) to return passage (6) .
Return oil from each control valve for travel, swing and implements flows to return passage (6) .The oil from return passage (6) flows through slow return check valve (15) to the hydraulic tank in the following manner.
With very low oil temperature, most of the oil flows through bypass check valve (20). The remainder of the oil flows through oil cooler (17). The oil then flows through return line (18) and return filter (18) to hydraulic tank (22) .
When the oil temperature increases, the rate of oil flow through bypass check valve (20) decreases. This causes the rate of oil flow through oil cooler (17) to increase.Case drain oil from swing motor (1) flows into drain line (3). Case drain oil from travel motors (2) flows into drain line (7). The oil combines in drain line (13) and flows through case drain filter (14) to hydraulic tank (22) .If a vacuum occurs in the swing motor, makeup line (4) will route oil to the inlet of the motor. Routing oil to the inlet of the motor will eliminate the vacuum condition.Components in Return Circuit
This section contains the description on the construction and operation of the following return circuit components.
Drain filter (14)
Oil cooler (17)
Return filter (18) and hydraulic tank (22)
Bypass check valve (20) Slow Return Check Valve and Oil Cooler
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Main control valve compartment (return circuit) (4) Makeup line (9) Main control Valve (12) Return line (15) Slow return check valve (19) Return line
Illustration 3 g00546009
Rear view of cab (16) Inlet line to oil cooler (17) (19) Return line (21) Return line (26) Block (built-in bypass check valve (20) )
Illustration 4 g00546005
Oil cooler (16) Inlet line to oil cooler (17) (17) Oil cooler (27) Outlet line (oil cooler to the hydraulic tank)Slow return check valve (15) is contained in return line (19). Slow return check valve (15) restricts the oil flow which causes a pressure increase in return line (19). Oil from return line (19) flows into makeup line (4). This removes the vacuum condition in the swing motor.Return oil flow from slow return check valve (15) passes