TURBO GP-BASIC 0R5721 - Caterpillar

Hydraulic Pump (Axial Piston-Type)
HYDRAULIC PUMP (931 Track-Type Loader) 1. Pump servovalve.2. Control piston.3. Spring (for swashplate).4. Swashplate.5. Pump drive shaft.6. Bearings (two, in pump body).7. Inlet opening (from tank).8. Outlet opening (to hydraulic system).9. Pistons (nine, in barrel).10. Barrel.Some vehicle engines have hydraulic pumps that are axial piston-type pumps. The movement of pistons, in this pump, pulls oil from the hydraulic tank and then pushes (pumps) the oil into the hydraulic system. The maximum gpm (liter/min) pump output for backhoe operation is the same for both the pump on the 931 Track-Type Loader and the pump on the D3 Tractor.When the engine is running, it turns pump drive shaft (5) and barrel (10) with nine pistons (9). The ends of pistons (9) are in the shape of a ball that connect to a retraction plate and slippers. The retraction plate and slippers turn with barrel (10) and are against swashplate (4) that does not turn. The two bearing journals, one on each side of swashplate (4), are in bearings (6) in the pump body and can let the swashplate pivot (to change the angle of the swashplate).When pump drive shaft (5) and barrel (10) turn, with swashplate (4) at its maximum angle position, pistons (9) are moved in and out of barrel (10) as the slippers follow the angle of the swashplate. As a piston (9) is moved out of barrel (10), it pulls oil, from the hydraulic tank, through pump inlet opening (7) and into the piston cylinder in the barrel. The barrel turns farther and the piston is moved into the barrel and pushes the oil from the piston cylinder through pump outlet opening (8) and into the hydraulic system.The pump for backhoe operation has maximum gpm (liter/min) pump output when the pressure of the oil in the hydraulic system is less than the pressure setting of pump servovalve.
PUMP SERVOVALVE (931 Track-Type Loader)
1. Servovalve. 11. Pressure compensator. 12. Spring. 13. Shims. 14. Passage (from pump outlet opening). 15. Passage (to control piston in the pump). 16. Oil drain passage.When the engine is running and the pressure of the oil from the pump in the hydraulic system is less than the pressure setting of the servovalve (1), oil from outlet opening (8) is in passage (14) and is stopped by pressure compensator spool (11). If the operation of the hydraulic cylinder gets stopped (with the control lever for the stopped cylinder held in the position to operate the stopped cylinder), the pressure of the oil through pump outlet opening (8) increases. The pressure of the pump oil increases until the oil in outlet opening (8) and in passage (14) has more force on pressure compensator spool (11) than the force of spring (12) has on the other end of spool (11), so the oil in passage (14) moves the pressure compensator spool. The pressure of the oil that can move the pressure compensator spool, and put more compression on spring (12), is approximately 2500 psi (17 000