Actuators in Pneumatic System.

Updated: Apr 23, 2020

As we know that actuators are the components which performs the work which we can see as output.

They work on basis of signal or input provided. In this blog we will see types of actuators and there uses.

Let us start with very common linear actuators and they are:

1. Single Acting Pneumatic Cylinder.

These cylinder are operated in one direction only, as we know cylinders have two strokes forward and backward, the single acting cylinders are controlled for only one stroke either forward or backward(generally their forward stroke is controlled) and the other is spring controlled it means once the piston reaches to its maximum possible point it is reverted back by spring force, at this point compressed air stops acting.

In these cylinder their is only one inlet port from where compressed air can be supplied, during exhaust stroke air inside the cylinder is released by a exhaust port.

Fig. 1: Single acting cylinder.

2. Double Acting Cylinder.

These cylinders consists of two ports so that both forward and reverse motion of the cylinder can be controlled. To get forward motion compressed air is inserted from piton side port and to obtain reverse motion air is inserted from rod side.

In double acting cylinder there is no return spring. Benefit of double acting over single acting is magnitude of motion is controllable for both strokes.

Fig. 2: Double acting cylinder

3. Double Acting Cylinder with In and Out Piston Rod and Shock Absorber at Stroke end.

Double These cylinder are very similar to the double acting cylinders,difference between these two are, the rod is attached to the both faces of the piston making the system two work on two loads simultaneously. When one rod gets extend the second one will contract and vice-versa. This system is used to improve efficiency and to use both of the strokes of the cylinder to get work output. W spring is used in these cylinders for shock absorption. They are mounted inside the cylinders at stroke end.

Fig. 3: Double acting cylinder with in and out piston rod

4. Linear Solenoid Coupled Actuator:

A linear solenoid actuator is a device which converts electrical energy into mechanical work using electromagnetic property.

This actuator has a solenoid coil warped inside the cylinder with a ferromagnetic plunger (actuator), this plunger is free to move in and out.

The movement of the actuator depends on the flow of the current, the direction of current creates a magnetic field in the coil in regard of its north and south pole.

To speed of the actuator is controlled either by controlling the flow of current or by increasing or decreasing the number of active coil in the solenoid.

At the inner side of the actuator a spring is attached for return mechanism. When current flows electromagnets get activated and causes the piston to move outward, once the flow of current stops, the spring pulls the piston inside and in this way this actuator works.

Fig. 4: Linear solenoid actuator.

5. Cylinder without Piston Rod.

As the name signifies these cylinder don't have any rod to actuate instead they have a sliders to provide linear motion and power while supporting a load.

These cylinder are mainly used as conveyors or when a longer distance movement is required (example is packaging industry). Also these cylinders can be used in applications like opening and closing of doors. These cylinders are much compact and due to higher load carrying capacity they are much efficient.

Fig. 5: Cylinder without piston rod by Festo.

6. Air Motor(Pneumatic Motor)

These are type of motors which does mechanical work by expanding compressed air. With help of linear or rotary actuators, these motors convert the energy of compressed air into mechanical energy.

Air motors are classified as

i) Linear Air motor.

ii) Rotary Vane motor

Linear Air Motor:

As we know in rack and pinion mechanism, the rack gives linear motion but it can be converted to rotary by help of a pinion, gears of same configurations are used on both rack and pinion to obtain this motion.

In this actuator similar mechanism is used, a geared rack is mounted with piston heads from both ends and in between a pinion is placed. Air is supplied from both sides of the rack to rotate the pinion clockwise and counter-clockwise.

Fig. 6: Piston based air motor.

Rotary Vane Motor:

It's name says limited rotation because in this actuator we can not obtain a complete rotation but the torque and motion produced in rotary sense.

These actuators got circular design with two ports, inside the circular housing there is a shaft which is connected to a vane, the vane is in between both ports so when compressed air is inserted from one port the vane moves toward the other port and it rotates the shaft, once the vane is at the end of stroke the second port is feeded with compressed air now vane will move in reverse direction and the first port will act as exhaust port.

Fig. 7: Rotary vane motor.

7. Fluidic Muscle:

Fluidic is referred for the mechanical devices which uses pneumatic or hydraulic methods to give a work output in controlled manner. Developer have developed and the research is still in process to develop a muscle which is acts and operates exactly like human muscle but can be operated mechanically or elctro-mechanically.

These actuators contains multiple flexible cylinders of smaller diameter which behave like actual muscle when air pressure is passed from it. Fluidic muscles are being used in creating robots with similar behavior as human, there brain can be created using AI but only with mechanical advancement there action can be matched and fluidic muscle is another step toward it.

Fig. 8: Fluidic muscle developed by Festo

Fig. 9: Another Fluidic Muscle by Festo

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