When reliable, safe power is required, air/pneumatic motors can easily produce rotational & torque motion from compressed air. Air motors have tremendous power density as compared to electric motors. So they are able to transmit more power from the same envelope or the same strength from a smaller container. This is especially the case when loads must be operated at less than the nominal speed of the electric motor — which requires using an electric motor with a separate gearbox or electric gear motor.
The pneumatic motor is a device, which is employed to perform a particular task more efficiently saving energy, time and efforts. There are physical tools to do mechanical jobs, or just technical means to make a job easy, such as a software program or mobile apps. The tools facilitate a task to be performed in a more organized way without getting involved. A hand-held tool is an instrument of manual operation for performing or facilitating mechanical operations. For performing different tasks, there is a different tool. There are machine tools for Industries, farm implements for agriculture, operating tools for doctors, and the list can go on endlessly.
For millions of years, tools were used in one form or other. Man learn to kill animals with a stick rather than engaging into a fist fight. He progressed with learning to make his tools more capable and dedicated to a task. This has continued till date. The hand-held tools, used for both industries and homes, required considerable human efforts to do the task. The force applied by hands results in whitening knuckles, fatigue, and strain. We are now living an era of powered tools, which incorporate emerging technologies, to do a task more efficiently, by multiplying the applied force. A hand-held power tool can draw power either from compressed air or electricity. We will discuss the air-powered tools and their driving motors here.
An air-powered tool or pneumatic tool is driven by the flow of compressed air at high pressure. The device is connected to a compressed air tank through a power hose. Pneumatic tools have become so popular that you can see a compressed air tank at a mechanic’s shop, near your home. The compressed air is used for inflating and maintaining required air-pressure in tires, as well as, unscrew and screw them for replacing or rotating. A slight rumbling and rattling are all that you feel, and a stubborn wheel screw comes undone. A pneumatic tool has many variations; it could just be a drill, impact wrench, ratchet, riveter, nail gun, sander, grinder, polisher, construction tools, paint sprayer or reciprocating saw. Due to their versatility, pneumatic tools, are extensively used in industrial assembly units and workshops, and now finding its way to homes to become indispensable to DIYers.
Pneumatic motors are designed to convert the energy of compressed air to mechanical energy in the form of linear or rotary motion. The linear motion air-powered tools use a system of pistons. The compressed air is fed to an air-tight chamber, the piston moves down the chamber and at its maximum length, air pressure is released, and a spring pulls the piston back to its original state. In heavy duty machines, some pistons are synchronized to give maximum torque.
A rotary vane motor generates rotational motion to a shaft. It is comprised of a rotating element with a slotted rotor mounted on the shaft. These slots are fitted with vanes extending up to the housing with the help of spring. Pressurized Air (4 – 6 bars) is pumped to the blades that cause the rotor to turn at high speed. A flywheel, with a planetary gear reduction system, helps maintain a high torque with low energy. It allows for the decrease in speed (10 – 20,000 rpm) and increases in torque. When the speed is maximum, the torque is zero. As soon as it is engaged, the engine flywheel delivers sufficient torque for the desired application. When the applied load exceeds the motor’s maximum torque, it causes the engine to stall. The rotary motion can be reversed with the injection of air from the opposite direction.
Pneumatic motors offer greater power density (power-to-weight ratio) than that of an electric motor. Unlike electric motors, they are safer to run in wet or damp environmental conditions. They have longer life span than electric motors.