Pneumatic Motors

Introduction to Pneumatic Motors

Pneumatic motors, also called air motors or compressed air engines, are a kind of motors which work by expanding the compressed air. The pneumatic motors convert the compressed air to mechanical motions to drive a device. The mechanical motions can be either linear or rotary. If using the linear method, the motion would come from a diaphragm or piston actuator. On the other hand, when it comes to the situation to use the rotary method, the motion would be generated either by a vane type air motor, piston air motor, air turbine or gear type motor.

During the past two centuries, pneumatic motors have existed in several types and developed with various forms. The size of this unique motor could be as small as the hand-held types or as large as engines that contain huge horsepower. Some of the pneumatic motors generate energy by pistons or cylinders while others would rely on slotted rotors with vanes, which are called vane motors, and turbines.

Pneumatic motors can improve their performance by heating the incoming air or the engine on their own. Up to now, the pneumatic motors have been adopted by hand tool industries and factories. However, when speaking to the transportation industry, pneumatic motors are still considered low efficiency and are not used on any vehicles.


Types of Pneumatic Motors

Pneumatic motors have been developed in various kinds. Generally, they can be divided into the following three types:.


● Linear Motors

Pneumatic motors of this kind can be divided into piston motors and hydraulic motors, which convert hydraulic energy into mechanical energy. Among these two, the piston motor is the mostly used one. Piston motors are designed with pistons, springs, and chambers. While working these motors, the compressed air would be sent into the air-tight chamber where the shaft of the piston is.

The air going into the chamber would cause the force on the piston shaft to begin to overcome the force being exerted on the spring. As more air is pumped into the chamber, the pressure on the piston shaft becomes more and more that would press the piston go down. When it reaches the maximum length, the compressed air would be released and the piston would return to the original position through the help of the spring, and get ready for the next cycle.

When the motors are not working, that means the air is not pumped into the chamber, the spring coiled around the shaft of the piston would keep the chamber open. Piston motors are often used in series of multiple cylinders which are enclosed in a housing. This would allow the motors to generate more energy to deliver.


● Rotary Vane Motors

Rotary vane motors use air to produce rotational motion to a shaft. The slotted rotor which is mounted on the drive shaft is responsible for the work of rotating. Each slot of the rotor would be fitted with a freely sliding rectangular vane. As for the vanes, they would be extended to the housing walls using springs, cam action, or air pressure. It depends on the design of the motors.

While working, the air would be pumped through the motor input and drive the vanes and result in the rotation of the central shaft. The speed of rotation can be between 100 and 25,000 RPM, which would depend on the amount of air pressure at the motor inlet and the diameter of the housing. Rotary vane motors are widely used in industrial fields for starting large industrial diesel or natural gas engines.

Compressed air, nitrogen, or natural gas can be the energy to drive the motor. The high pressure they add on the vanes would drive the rotor spins at a high speed. However, the most important factor to start the engine would be the torque, so that the reduction gears which create huge torque would be used. This kind of gear can create high torque levels with the lower amounts of energy input and enables the motor to create enough torque to start the engine.


● Turbine Motors

Turbine motors are mostly used in handpieces because it is small enough and would not increase the weight of the devices. It can spin at speeds over 180,000 RPM, but with limited torque.


Applications of Pneumatic Motors

Pneumatic motors are now mostly used in industrial starters and hand tools, especially pneumatic tools such as impact wrenches, pulse tools, screwdrivers, nut runners, drills, grinders, sanders, etc. For industrial use, because of the features below, they are also popular in this field.


Features of Pneumatic Motors

● Able to offer greater power density than the electric ones can do.
● Do not require an auxiliary speed controller.
● Generate less heat.
● Be used in more volatile atmospheres.
● Do not require electric power.
● Do not create sparks.
● Not easy to be broken.

In conclusion, features that pneumatic motors contain have made machining works easier and more convenient. Moreover, the pneumatic motors provide less energy consumption.

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