SHAFT 3T9958 - Caterpillar

The push-pull solenoid valve is normally in the BAIL LOWER position when the valve is not activated by the bail control switch. The push-pull solenoid valve is activated when the switch is moved to the BAIL RAISE position. When the push-pull solenoid valve is in the BAIL LOWER position, oil is sent to cavity (7) and valve spool (1) is shifted to the left. Pump oil enters the valve through passage (23) and passes through check valve (22). The oil moves through passage (12) around valve spool (1). From valve spool (1), oil flows through passage (4) to the head end of the bail cylinder. This extends the rod in the bail cylinder and this lowers the bail. This oil also passes through orifice (21) and into spring cavity (19). The pressure of this oil acts on poppet (17).
Illustration 2 g00733579
(6) Oil passage to the hydraulic tank (8) Retainer (10) Spring (11) Shuttle valve (24) Oil passage to the hydraulic tank (25) Oil passage to the hydraulic tank (26) Oil passage to the hydraulic tankRod end oil is returned through passage (2) to passage (6). The oil from passage (6) moves shuttle valve (11) to the left against retainer (8). Return oil flows through the small orifices in shuttle valve (11) and drains to the hydraulic tank through passage (26). When the oil from passage (6) flows through the small orifices in shuttle valve (11), the restriction of the orifices meters oil flow from passage (6). The small orifices control the speed of the bail as the bail is lowered.
Illustration 3 g00733585
Position of Shuttle Valve with Application of External Force (6) Oil passage to the hydraulic tank (8) Retainer (10) Spring (11) Shuttle valve (24) Oil passage to the hydraulic tank (26) Oil passage to the hydraulic tankIf an external force is applied to the bail, the flow of oil from the bail cylinder increases. Oil continues to flow through the small orifices until the pressure increases enough to overcome the spring force of spring (10). Shuttle valve (11) moves retainer (8) to the left in order to compress spring (10). This opens the slots on shuttle valve (11) to passage (26). Return oil drains to the tank and the bail lowers rapidly. This prevents the pressure in passage (6) from rising too high.Pressure Relief Valve
Illustration 4 g00720232
(12) Passage (14) Passage (15) Piston (16) Spring (17) Poppet (18) Valve (19) Spring cavity (20) Spring (21) Orifice (26) Oil passage to tankAt the same time as oil is entering passage (2), oil also enters orifice (21) and flows into spring cavity (19). When the oil pressure in spring cavity (19) overcomes the force of spring (16), the oil pressure in spring cavity (19) unseats poppet (17) .When poppet (17) unseats, the oil in spring cavity (19) vents to the tank through tank passage (26). The pressure in passage (12) causes valve (18) to shift downward. This blocks the flow of oil from passage (23) to passage (12) .As the oil vents past