SUPPORT-ENGINE 1372196 - Caterpillar

HOLD Position
Illustration 1 g01227515
Illustration 2 g01226582
In the HOLD position (5), the spring (8) holds spool (7) in the centered position. No pilot oil enters the control valve through the port (9) and port (10). Any pilot oil in the pilot lines drains through the pilot valve to the tank. The spool (7) blocks the flow of pump supply oil in passage (6) .Passage (6) is common to all control valves in the bank valve. The passage has no outlet. The spool blocks the flow of pump supply oil until the operator moves the pilot valve.STICK OUT Position
Illustration 3 g01227471
Illustration 4 g01226582
When the stick circuit is the only hydraulic circuit in operation, the stick circuit will have the highest signal oil pressure in the hydraulic system. When the pilot valve on the left side is moved to the STICK OUT position (1), pilot oil enter the control valve through port (21) and flows to chamber (22). When the pilot oil overcomes the force of spring (13), spool (12) moves to the right.When the spool moves to the right, pump supply oil flows from passage (17) around the spool and into passage (18) .The hydraulic oil in passage (18) flows to pressure compensator valve (9). In the pressure compensator valve, the hydraulic oil flows into internal passages. The pressure compensator valve moves up. As the pressure compensator valve moves up, the cross-drilled passage is opened to an internal passage that is in the valve. Some of the hydraulic oil flows around the pressure compensator valve to chamber (8). The hydraulic oil that flows to chamber (8) is signal oil. The signal oil balances the pressure compensator valve against the hydraulic oil pressure in passage (18). This controls the flow across spool (12) .The signal oil in the internal passage flows to the pressure compensator valve in each control valve. The signal oil also flows to the pressure and flow compensator valve on the hydraulic pump. The signal oil helps to control the output of the hydraulic pump. The hydraulic pump upstrokes and the hydraulic oil pressure in passage (17) and passage (18) increases. When the hydraulic oil pressure in passage (18) raises above circuit pressure, the hydraulic oil unseats the check valve (7) and the check valve (10). The hydraulic oil flows to passage (16) and passage (19) .In passage (16), spool (12) blocks the flow of oil. In passage (19), the oil flows around the spool (12) to passage (20). Then, the oil flows through port (6) to the rod end of the stick cylinder.Hydraulic oil from the head end of the stick cylinder flows through port (11) to passage (15). The hydraulic oil flows around spool (12) into passages (14) .The hydraulic oil in passage (14) flows to all control valves as makeup oil. Then, the hydraulic oil flows to the tank.When the operator releases the pilot valve, the pilot valve returns to position (5). The flow of pilot oil to the valve is blocked. The loss of pilot oil enables spring