973K Track-Type Loader Systems Flushing Valve Caterpillar


Flushing Valve
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973K Track-Type Loader Systems [M0086865]
HYDRAULIC SYSTEM
VALVE GP-PURGE
973K Track-Type Loader Systems Flushing Valve


Illustration 1g01957990
Flushing valve with the transmission control lever in the NEUTRAL position
(1) Spacer
(2) Spring
(3) Chamber
(4) Passage
(5) Orifice
(6) Passage
(7) Chamber
(8) Spring
(9) Spacer
(10) Port from the drive loop
(11) Spool
(12) Port from the drive loop

When the transmission control lever is in the NEUTRAL position, both sides of the drive loop have equal pressure. Oil flows from one side of the drive loop through port (12) into chamber (3). Also, oil flows from the other side of the drive loop through port (10) into chamber (7). Since the oil pressure on both sides of the drive loop is equal, the oil pressure in chamber (3) and in chamber (7) is equal. As a result, spool (11) is centered and oil does not flow through the rest of the flushing valve.



Illustration 2g01957991
Flushing valve with the transmission control lever in the FORWARD position or in the REVERSE position
(1) Spacer
(2) Spring
(3) Chamber
(4) Passage
(5) Orifice
(6) Passage
(7) Chamber
(8) Spring
(9) Spacer
(10) Port from the drive loop
(11) Spool
(12) Port from the drive loop
(13) Chamber

When the transmission control lever is moved to the FORWARD position or to the REVERSE position, one side of the drive loop has a greater pressure than the other side of the drive loop. High pressure oil from one side of the drive loop flows through port (10) into chamber (7). At the same time, reduced pressure oil from the other side of the drive loop flows through port (12) into chamber (3). Since the oil pressure in chamber (7) is greater than the oil pressure in chamber (3), spool (11) shiftsuntil spool (11) contacts spacer (1). The oil pressure in chamber (7) overcomes the force of spring (2). Spool (11) and spacer (1) continue to move to full travel.

As spool (11) moves to full travel, spool (11) opens port (3) to chamber (13). Reduced pressure oil flows from port (3) into chamber (16). The oil flows from chamber (16) through orifice (5) and passage (6). The restriction of oil flow through orifice (5) flows to the motor bearings as lube oil. The oil flow through passage (6) flows to the motor charge relief valve.

Reference: Refer to Systems Operation, "Relief Valve (Charge Pressure) (Motor)" for more information on the motor charge relief valve.

The purpose for the flushing spool is to flush heat out of the closed loop and the motor case. The flushing spool also purges contaminants for the closed loop.