GUIDE AS. 2747933 - Caterpillar

Illustration 1 g00896718
Flushing valve with the transmission control lever in the NEUTRAL position
(1) Spring
(2) Chamber
(3) Spool
(4) Orifice
(5) Passage
(6) Chamber
(7) Chamber
(8) Spring
(9) Spacer
(10) Port from the drive loop
(11) Spool
(12) Port from the drive loop
(13) Spacer
(14) Spring 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 (10) into chamber (6). Also, oil flows from the other side of the drive loop through port (12) into chamber (7). Since the oil pressure on both sides of the drive loop is equal, the oil pressure in chamber (6) 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 2 g00896909
Flushing valve with the transmission control lever in the FORWARD position or in the REVERSE position
(1) Spring
(2) Chamber
(3) Spool
(4) Orifice
(5) Passage
(6) Chamber
(7) Chamber
(8) Spring
(9) Spacer
(10) Port from the drive loop
(11) Spool
(12) Port from the drive loop
(13) Spacer
(14) Spring
(15) Passage
(16) 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 (12) into chamber (7). At the same time, reduced pressure oil from the other side of the drive loop flows through port (10) into chamber (6). Since the oil pressure in chamber (7) is greater than the oil pressure in chamber (6), spool (11) shifts to the left until spool (11) contacts spacer (9). The oil pressure in chamber (7) overcomes the force of spring (8). Spool (11) and spacer (9) continue to move to full travel. As spool (11) moves to full travel, spool (11) opens port (6) to chamber (16). Reduced pressure oil flows from port (6) into chamber (16). The oil flows from chamber (16) through orifice (4). The restriction of oil flow through orifice (4) creates pressure for spool (3) against spring (1). As the pressure of spool (3) overcomes the force of spring (1), passage (5) opens to chamber (2). Then, the oil flows from orifice (4) through passage (5) of spool (3) into chamber (2). Then, the oil flows from chamber (2) through passage (15) to the case of the piston motor.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.