semi-automatic control of a double-acting pneumatic cylinder

SEMI-AUTOMATIC CONTROL OF A DOUBLE-ACTING PNEUMATIC CYLINDER 

(SEMI-AUTOMATIC MATERIAL HANDLING CIRCUIT)

1. Circuit

Fig.13.6 illustrates a circuit that provides semi-automatic operation by using pressure- operated pilot controls.

2. Operation

Extension: When operator momentarily presses the push-button of 3/2 pilot control. valve, the compressed air flows through this valve and enters pilot chamber X shifting the 4/2 DC valve to its right envelope flow path configuration. When the 4/2 DC valve is shifted to its right mode, the compressed air flows to blind end of the cylinder and thus the cylinder extends. At the same time, the air at the rod end of the cylinder is exhausted into the atmosphere directly. It may be noted that the piston out speed of the cylinder is controlled by flow control valve.

Retraction: Once the extension stroke of the cylinder completes, the cam-operated pilot control valve is tripped and air flows to pilot chamber Y of 4/2 DC valve shifting its position. When the 4/2 DC valve is shifted to its left mode, the compressed air flows to the rod end of the cylinder and thus the cylinder retracts. At the same time, the air at the blind end of the cylinder is exhausted to the atmosphere.

For the next cycle, again the operator only needs to momentarily press the push-button. Thus in this semi-automatic circuit, once the operator momentarily presses the push-button, the circuit completes its cycle automatically. This circuit may be used as semi-automatic material handling circuit for pushing the large boxes from transfer table onto conveyor, as shown in Fig.13.6.