YOKE 3T4953 - Caterpillar

Stick Raise Operation
Illustration 1 g00294900
Top view of stick cylinder (1) Line to head end of cylinder. (2) Drain line. (3) Incoming pilot line. (4) Control valve. (5) Line to rod end of cylinder.
Illustration 2 g00294542
(6) Incoming check valve. (7) Bleed line. (8) Line to rod end. (9) Control valve. (10) Pressure relief. (11) Outgoing check valve.The stick pilot control valve moves to the RAISE position. Pump oil from line (5) flows into the stick control valve. The pump oil passes through check valve (6) and flows into the rod end of the stick cylinders.The oil in the head end of the stick cylinders goes through line (1) , and back to the hydraulic tank through the stick control valve.When the implement control lever is moved to the NEUTRAL position, the stick cylinders are held in the lowered position. Check valve (6) prevents the oil in the rod end of the stick cylinders from flowing out of the stick cylinders.Stick Lower Operation
When the stick pilot control valve is moved to the BOOM LOWER position, pilot oil is sent through line (3) to the stick control valve. The pilot oil shifts check valve (11) and control valve (9) . Oil flows from the rod end of the stick cylinders flows through the stick control valves and line (5) to the hydraulic tank.At the same time, main pump oil from the stick control valve flows through line (1) to the head end of the stick cylinders. Relief Valve Operation of the Stick Cylinder Rod End
When the stick is pushed downward by an outside force the oil pressure in the rod end of the cylinder increases. The oil pressure is sensed at relief valve (10) of the stick control valve. When the relief valve opens the oil flows back to the hydraulic tank. Note: The relief valve is set to open at 36300 500 kPa (5265 72.5 psi) .Stick Lower Operation Manually
Illustration 3 g00295465
Bleed Valve (View) (12) Bleeder Valve. (13) Locknut. (14) Piston. This function is used to manually lower the stick when the engine is shut down. This function is also used when no pilot oil pressure is supplied. The oil flows from the rod end of the cylinder through line (7) to bleeder valve (12) . When locknut (13) and piston (14) are slowly loosened, oil is allowed to flow through the bleeder valve. The oil flows through bleeder valve (12) to the head end of the cylinder through line (8) . The head end of the cylinder fills with oil. The excess oil returns to the hydraulic tank.