BUSHING 1C7138 - Caterpillar

Coupler Circuit
The lines group of the coupler circuit is designed so that once the coupler cylinder has fastened the implement to the quick coupler frame, the lines to the coupler cylinder can be disconnected and connected to another cylinder, usually part of the implement. This means the coupler control valve can be used to control another cylinder once the coupler cylinder has been used. The following description is for the coupler cylinder.Engage Operation
When the coupler control lever is moved to ENGAGE position, coupler valve spool (14) moves to ENGAGE position. Coupler cylinder oil (head end) goes through coupler valve spool (14). This oil now becomes signal oil. Signal oil then goes through shuttle valve (12) to unloading valve (9) and margin stem (8) of inlet valve group (1). Unloading valve (9) moves completely to the left and the implement oil pressure increases. Margin stem (8) is held to the left (does not move).The implement oil now opens load check valve (15). The oil goes around coupler valve spool (14) and out coupler control valve (13) to the head end of coupler cylinder (16). The cylinder rods extend and the implement is fastened to the quick coupler frame.The movement of the cylinder rods push oil out of the rod ends of coupler cylinder (16). This oil comes into coupler control valve (13) and goes around coupler valve spool (14). Then the oil goes through the common tank passages in the coupler control valve and inlet valve group (1) on its way back to oil filter (7) and hydraulic tank (6).When the coupler control lever is released, the lever and coupler valve spool (14) go back to their HOLD positions. The coupler valve