GEAR (72 Teeth) 7S8685 - Caterpillar

When poppet (16) shifts to the right, the pressure in cavity (15) will decrease. The pressure on the end of valve (20) overrides spring (22). Then, dump spool (21) moves toward the right. The flow of oil that is needed to lower the pressure at inlet (13) is allowed to flow out of tank passage (14).When the pressure at inlet (13) is less than the adjusted pressure, the force of spring (28) moves poppet (16) to the left. Poppet (16) will seat. Then, the combination of the pressure in cavity (15) and the spring force from spring (22) moves dump spool (21) to the left against the seat. At this time, the flow of oil to tank passage (14) is blocked.Makeup Valve
The line relief valve can be used as a makeup valve. When either the lift cylinder or the tilt cylinder is moving and the pump can not supply the amount of oil that is needed to fill the void in the cylinder, oil through the makeup valve is available to assist in filling the void.
Illustration 7 g02025960
(13) Inlet
(19) Makeup spool
(24) Main control valve
(25) Tank port
(BB) Tank oil
(CC) Active components
(DD) Surface area
(FF) Reduced tank oil When the line relief valve is installed into main control valve (24), makeup spool (19) will be seated against the main control valve. The seat separates the inlet from tank port (25).
Illustration 8 g02025975
(13) Inlet
(19) Makeup spool
(24) Main control valve
(25) Tank port
(BB) Tank oil
(CC) Active components
(DD) Surface area
(FF) Reduced tank oil The oil from tank port (25) flows against makeup spool (19). When the pressure of the tank oil is greater than the force that is holding makeup spool (19) to the left, makeup spool (19) moves off the seat. The tank oil will flow around makeup spool (19) to the inlet (13). Then, the flow of oil will fill the void in the actuator.
Illustration 9 g02026013
(13) Inlet
(19) Makeup spool
(24) Main control valve
(25) Tank port
(26) Disc springs
(BB) Tank oil
(CC) Active components
(DD) Surface area
(FF) Reduced tank oil The line relief valve that protects the head end of the lift cylinder will not function as a makeup valve. The line relief valve has disc springs (26) that are installed between the frame of the valve and makeup spool (19). This will prevent makeup spool (19) from moving away from the seat.Dual Pressure Relief Valve
Illustration 10 g02096018
(AA) Supply oil
(BB) Tank oil
(CC) Active components
(DD) Surface area
(GG) Pilot oil The line relief valve for the rod end of the tilt cylinder is a dual pressure relief valve. This valve has two relief settings. Pilot pressure determines the setting that is active.When the dual pressure solenoid valve is energized, pilot oil from the spring chamber of the relief valve is directed to the tank. This causes the relief valve to open at the lower pressure setting.When the dual pressure solenoid valve is de-energized, pilot oil is directed to the spring chamber of the relief valve. This causes the relief valve to open at the higher pressure setting.Pilot Relief Valve
Illustration 11 g02026180
Pilot relief valve
(27) Tank