Air motors & solutions

Modec: specialists in low speed air motors

Rémy Davin
by Rémy Davin on Mar 23, 2020 11:25:07 AM

There are many applications where there is no choice but to use air motor technology to drive a mechanism. Most of the time it is due to the environment in which the mechanism operates. It can for example be an area with Atex hazards, or dust, high humidity, even underwater, etc.

A small space is also a a good reason to use air motors. Since an air motor is 4 to 5 times more compact than an electric motor at the same power, it perfectly meets the requirements of confined spaces. This is a constraint often encountered by designers of special machines and on-board systems.

The weight of an air motor is also one of its advantages. It fits perfectly portable systems or systems mounted on manipulator robots, deburring or painting robots, etc…

On transportable mechanisms, it is common that the only energy used is compressed air. It is then expensive and sometimes impossible to integrate another energy source.

In addition, when the system requires numerous stop/start operations, or when the motor must be blocked during the cycle, it is easier to use an air motor than any other type of motorisation.

Certain functions using air motors require precision movement and/or a slow rotation speed

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How do you go from high-speed technology such as air motors that run at speeds between 9000 and 12000 rpm to the very slow speeds that these systems require?

The answer is very simple: by integrating a gearbox into the motor ! It will then be possible to reduce the rotation speed to a few revolutions per minute. However, be careful because for the implementation of this solution, the application and the constraints mentioned above must be listed and considered, without forgetting the service rate. 

There are two main ways of adding a gearbox to an air motor:

1. Air motor set on a worm gearbox:

- The main advantage is the possibility to have a static irreversibility of the assembly. It’s the most economical solution

- The main drawback being the efficiency of the motor associated with this type of gearbox is greatly reduced, depending of the input speed. It is not a very compact solution.

The applications that may require this type of solution are crane, load tipper, welding machine, tarpaulin winding, hopper motorization, washing machine, drilling machine, etc. 

2. Air motor with integrated planetary gear reducer:

- The advantages are the extreme compactness and an increased reliability. The parts are designed to work as a single device.

- The disadvantage is, as it is designed to meet particular space constraints, the maximum allowed torque is limited. Depending on the application, this is not always a constraint.

Some application on which we already provide such configuration of air motor are agitators, vibrators,  winders, manipulator arms, etc…

How can a pneumatic motorization problem be solved when the application needs a high torque and compactness?

The solution involves the integration of a torque limiter. This system is used both to protect the motor from the risk of breakage, in this case the torque limit is fixed and does not require adjustment. Also, to control the torque that is generated by the motorized system of the air motor, a solution allowing adjustment of the torque is necessary.  On this matter, we would like to share our experience of two complex implementation of air motors:

1. Air motor - rotation speed of just 1 rpm for a specific application in the nuclear industry 

We first encountered this issue when working with a client in the nuclear industry. The company needed an air motor with a rotation speed of just 1rpm (which involves very high reduction) for a specific application. This meant we had to find a way to control the torque but without installing a large, heavy gear box that would normally be needed to achieve this. We found a solution by incorporating a small torque limiter into the motor.

Building on from this experience, our team has designed a wide range of torque limiters that can be adapted and used in unlimited combinations to respond to our clients’ needs. We have two basic prototypes:

#1  An air motor with a small torque limiter ...

... which is placed in the middle of the air motor as an integral part. Placing it between the pneumatic part and the gearbox means you can manage a large torque with a smaller torque switch. The advantage of this option is a lighter air motor adapted for use in smaller spaces.

#2  An air motor with a larger torque limiter ...

... which is indeed a separate module added to the end of the motor. This is suitable for use in machines based in plants or workshops, or in situations where space is not restricted.

2. Air motor - low speed air motors for the valve manufacturing industry, aircraft industry, chemical refineries

Sans titre-12

One of the advantages of modec torque limiters is that you can either set the motor to disengage once the maximum or selected torque limit is reached, or you can opt to receive a signal that indicates the limit has been reached giving you the option to either stop the motor or any other action (for example change the rotation direction, or change the supply air pressure).

We have clients using our low speed motors in the french valve manufacturing industry and aircraft industry (for slow-moving conveyors), in chemical refineries in China, as well as a major water supply company in France. 

Given that every business will have different requirements, we prefer to work with clients individually to design and build on demand a low-speed air motor that meets their specific needs.

As you may have understood through this blog, which we hope will be informative, it is not necessarily very easy to implement an air motor. Not that it is complicated, on the contrary, because technologies using compressed air are always simple, but because there are many solutions.

Our recommendation: rely on a specialist for the definition of your solution!

Don’t hesitate to contact us and find out what we can do for you, or to download our case studies

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