① Bucket retraction operation.
As shown in Figure 1-41, when the bucket is retracted, the pressure of the pilot control valve is supplied to the port XBk, and the bucket spool 5 moves to the left against the two springs 2 and 3 inside and outside.
The hydraulic oil of pump P2 enters the parallel channel, directly enters the oil port Bk1 through the load check valve LCK, and then flows into the large cavity end of the bucket cylinder.
The return flow from the rod end of the bucket cylinder returns to the bucket spool through the oil port Ak1, and then directly enters the oil return port R2 through the channel.
②Modern excavator bucket extension operation.
As shown in Figure 1-42, when the bucket is extended, the pilot pressure of the pilot control valve is supplied to the oil port
XAk, the bucket spool 5 moves to the right against the springs 2 and 3.
The hydraulic oil of the pump P2 enters the parallel channel through the load check valve LCk and flows directly to the oil port AK1, and then flows into the rod end of the bucket cylinder.
The return flow from the rod end of the bucket cylinder returns to bucket spool 5 through port Bk1, and then directly flows into the return port R2 through the channel.
(4) When the rotary control spool rotates left and right, only the hydraulic oil of the pump Pl is supplied to the rotary motor.
As shown in Figure 1-43, the pilot pressure of the pilot control valve is supplied to the port XAs, and the rotary spool 2 moves to the left against the inner and outer springs 7, 8.
The hydraulic oil of the pump Pl flows into the rotary spool 2 through the parallel channel, and then directly enters the rotary motor through the check valve LCs and the oil port As. Therefore, the swing motor rotates, and the return oil of the swing motor enters the oil port Bs. The oil flow returned by the motor returns to the tank port R2 through the rotary valve core and the passage.
Rotation work is basically the same.
