dual-cylinder sequencing circuit (sequencing of two hydraulic cylinders using solenoids and limit switches)

DUAL-CYLINDER SEQUENCING CIRCUIT

(SEQUENCING OF TWO HYDRAULIC CYLINDERS USING SOLENOIDS AND LIMIT SWITCHES)

1. Circuits and Construction

Fig.14.13 illustrates a electrohydraulic system that provides a cycle sequence of two hydraulic cylinders. Fig.14.13(a) shows the hydraulic circuit of the system and Fig.14.13(b) shows its ladder diagram: This system uses two sequence valves V1 and V2 to control the sequence of operations of two double-acting cylinders.

2. Operation

The sequence of operation is as follows:

Extension stroke

1. When the START push-button switch is momentarily pressed, solenoid SOL A is energized.

2. When the SOL A is energized, the 4/2 DC valve V1 is shifted to left mode and it forces the oil to flow into the blind end of the cylinder 1. Thus, the cylinder 1 extends.

3. When limit switch 1-LS is actuated, solenoid SOL C is energized.

4. When the SOL C is energised, the 4/2 DC valve V2 is shifted to left mode and it forces the oil to flow into the blind end of the cylinder 2. Thus, the cylinder 2 extends.

Retraction stroke

5. When limit switch 2-LS is actuated, solenoid SOL B is energized.

6. When the SOL B is energized, the valve V1 is shifted to right mode and it forces the oil to flow into the rod end of the cylinder 1. So the cylinder 1 starts to retract.

7. As the cylinder 1 starts to retract, it deactuates the limit switch 1-LS, which de- energizes SOL C.

8. When the SOL C is de-energised, the valve V2 is shifted to spring offset mode. This forces the piston of the cylinder 2 to retract to its original position.

9. As a result, both cylinders 1 and 2 retract at the same time, and thus a cycle of operation is completed.