PUMP GP-GEAR 2939113 - Caterpillar

STICK OUT Position
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Backhoe control pattern
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Excavator patternWhen 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 (10). 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 (7) and 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. More oil flows to chamber (7). When the hydraulic oil pressure in chamber (7) raises above circuit pressure, the hydraulic oil unseats the check valve (9). 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).
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When the oil pressure overcomes the force of spring (22) and spring (23), the lower section (24) of the poppet moves upward. Oil flows through the lower section (24) of the poppet into chamber (26). The oil flows through section (27) of the poppet. The oil then flows through the port (6). As the flow of oil increases, the ball (25) moves up. Spring (23) is compressed more. Oil flows around the ball (25) into chamber (26). This oil helps balance the pressure in chamber (26) and chamber (20) .The oil that flows through port (6) flows to the rod end of the stick cylinder. This extends the stick.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 HOLD position (5). The flow of pilot oil to