Control of Pneumatic Double Acting Actuator Using Multiple Push Buttons

 

Introduction

Controlling the actuator using multiple push buttons is a very common requirement in manufacturing lines, assembly stations, and safety-based operations. This assignment explains in detail how a double acting pneumatic actuator can be controlled using multiple push buttons, along with working principles, components, control logic, advantages, limitations, and industrial applications.

Double Acting Pneumatic Actuator

A double acting pneumatic actuator uses compressed air for both extension and retraction of the piston. Unlike a single acting cylinder, it does not rely on a spring for return motion. Air pressure is supplied alternately to both sides of the piston through a directional control valve (DCV), usually a 5/2.When compressed air enters the cap end, the piston extends. When air enters the rod end, the piston retracts. This makes double acting actuators suitable for precise control, higher force output, and continuous industrial operations.

The main components used in this control system are:

1. Air Compressor – Supplies compressed air to the system.

2. FRL Unit (Filter, Regulator, Lubricator) – Cleans, regulates, and lubricates compressed air.

3. Double Acting Pneumatic Cylinder – Performs linear motion (forward and backward).

4. Directional Control Valve (5/2 DCV) – Controls the direction of airflow.
s (3/2 DCV – Normally Closed) – Used as manual input devices.

6. Tubing and Fittings – Carry compressed air between components.

7. Logic Valves (AND / OR valves) – Used when multiple push buttons must be pressed together or separately.

Concept of Multiple Push Button Control

Multiple push button control means more than one push button is used to operate a single actuator. This is commonly used for:

Safety purposes (two-hand operation)

Sequential control

Operator confirmation

Multi-location control

Depending on the requirement, push buttons can be connected using AND logic or OR logic.

Two-Hand Safety Control Using AND Logic

In many industrial machines, safety regulations require that both hands of the operator must be engaged during operation. This prevents accidental injuries.

Working Principle:

Two normally closed 3/2 push button valves are used.
The outputs of both push buttons are connected to an AND logic valve.
The output of the AND valve is connected to the pilot port of a 5/2 DCV.


Operation:

When only one push button is pressed, no output signal is generated.
When both push buttons are pressed simultaneously, the AND valve allows air to pass.

This pilot air shifts the 5/2 DCV, causing the double acting actuator to extend.

Releasing any one push button removes the pilot signal, and the actuator retracts.

This method ensures high safety and is widely used in press machines and cutting operations.
OR Logic Control Using Multiple Push Buttons. In OR logic control, the actuator can be operated from any one of multiple push buttons.

Working Principle:

Multiple 3/2 push button valves are connected to an OR logic valve (shuttle valve).The output of the OR valve is connected to the pilot port of the 5/2 DCV.

Operation:

Pressing any one push button sends a pneumatic signal.
The OR valve passes the signal to the directional control valve.

The actuator extends.

Releasing the push button removes the signal and the actuator retracts.This system is useful when multiple operators or stations need control over the same actuator.

Advantages of Multiple Push Button Pneumatic Control

High safety for operator

Simple and robust system

No electrical power required

Easy maintenance

Reliable operation under harsh industrial conditions

Limitations

Limited precision compared to electrocute-pneumatic systems.

Speed control depends on air pressure and flow control valves.

Not suitable for complex automation without PLC integration.

Air leakage can reduce efficiency.

Industrial Applications

Press machines (two-hand safety control).

Packaging machines.

Assembly lines.

Material handling systems.

Pneumatic clamping operations.

Conclusion

Controlling a pneumatic double acting actuator using multiple push buttons is a practical and widely adopted industrial control method. By using pneumatic logic such as AND OR valves, safe and reliable control can be achieved without electrical components.