The oil from main pump (19) enters

The oil from main pump (19) enters main control valve (4). Then, the oil flows to the return passages in one of the following conditions. Return oil flow takes one of two paths: 1.When all joysticks and/or travel levers/pedals are in the NEUTRAL position, oil from main pump (19) flows through bypass spool into drain passage (10). Oil then flows through drain passage (11) to hydraulic tank (17). 2.When any one of the joysticks and/or travel levers/pedals shift from the NEUTRAL position, pilot oil flows to shift the appropriate spool. The oil flows through the appropriate spool into the appropriate component. The oil returns through the spool and enters drain passages (9), flows through drain passage (11), into hydraulic tank (17). The pilot oil flows to hydraulic tank (17) through pilot drain passage (9) and pilot drain line (5). Bypass spool (6) returns oil to hydraulic tank (17) differently depending on the position: 1.In the right position, bypass spool (6) drains high pressure in drain passage (10) through bypass drain line (12) to hydraulic tank (17). 2.In the center position, bypass spool (6) will open up the pilot passage through the control valves to the pilot drain passage (9) when all controls are in the neutral position. Return oil is still drained as in the previous condition. 3.In the left position, bypass spool (6) immediately drains supply oil from supply line (20) into hydraulic tank (17) through bypass drain line (12). Pilot oil and return oil are still drained as in the previous condition. Travel motors (1) and swing motor (2) both drain oil to hydraulic tank (17) through drain line (3).