PTM Geschäftsführer Carsten Angermeyer und Christian Maier von Maier Heidenheim

PTM CEO Carsten Angermeyer and Christian Maier of Maier Heidenheim

Report from our partner Maier Heidenheim about the joint project:

“Stirred and saved money”

PTM mechatronics has developed an efficient solution for companies that have to stir liquids in a large number of containers under ATEX conditions. Instead of an agitator per container, a movable compressed air motor is installed that grips the individual agitator shafts. The cost-saving innovation was made possible by the support of the rotating union specialist Christian Maier.

If you visit PTM mechatronics GmbH in Egenhofen, you will find yourself in rural tranquility between Augsburg and Munich. But idyll and innovation are not mutually exclusive here – after all, the company, founded in 1988, is one of the specialist suppliers in demand worldwide when it comes to compressed air motors and grippers for use in special environments. Pneumatic motors for use in potentially explosive areas, for example in the production of chemicals and paints, seawater-resistant drives for use on drilling rigs or in diving equipment, stainless steel motors for agitators in food production and grippers for various applications from robots to clean rooms: In all of these market niches the products and solutions from PTM mechatronics have a first-class reputation. “The main advantages of the compressed air motor over the electric motor are that there are no risks of sparks due to the mechanical construction of the motors and that the motor can be optimally adapted to the requirements in use,” explains Carsten Angermeyer, owner and managing director of PTM mechatronics.

Radial piston motor for stirring in explosion-proof environment

A specialty of the company is the motor technology: Instead of vane motors, PTM mechatronics relies on compressed air motors with radial pistons, which are arranged around the drive shaft similar to a radial motor and are set in rotation via a rotary valve control. This design has two significant advantages for the user: Even at low speeds, high torques can be achieved, and the compressed air consumption is up to 90 percent lower than that of a vane motor. “Our radial piston motors can show their advantages particularly with agitators in explosion-proof environments,” says Angermeyer. The powerful torque also enables the stirring of more viscous substances, and in the frequently required continuous use, the low compressed air consumption leads to high savings in energy costs. Often a large number of liquid containers are stored in companies that have to be stirred at intervals – for example when mixing colors, chemicals or fragrances. In such cases, the purchase of a complete agitator for each container would be disproportionately expensive. On the basis of a customer project that showed exactly this constellation, PTM mechatronics developed an efficient concept: A single motor should be used, which is mounted on an automatically movable device and equipped with a pneumatic three-jaw gripper on the drive shaft. The motor positions itself alternately over a container, grabs the stirring rod attached to it, mixes the liquid for a predetermined period of time and then moves on to the next container.

Rotary feedthrough enables power transmission to the rotating gripper

A tricky task arose for PTM mechatronics: Because the rotating gripper is attached to the drive shaft, the compressed air had to be fed into the rotating hollow shaft via a valve on the stationary shaft housing. A rotary feedthrough is required for this purpose – a technically sophisticated product, the development and manufacture of which Christian Maier GmbH & Co. KG in Heidenheim in southern Germany has specialized. “In view of the technical framework, it quickly became clear that no standard solution would be possible,” recalls Florian Maier, Managing Director of Christian Maier. While the specifications for the motor geometry could be implemented with constructive adaptations, greater effort was required for use in explosion-proof environments. Only devices with Atex certification, which is only granted after successful completion of extensive test series, is permitted there. After a first prototype showed that the interaction between the Maier rotary feedthrough and the motors and gripper unit from PTM works, the conformity assessment procedure was initiated at Christian Maier. “Since we already have Atex-certified rotary unions in our delivery program, we were able to fall back on existing experience,” reports Florian Maier.

Successful Atex certification

In elaborate tests it was necessary to ensure and document that the rotating union caused neither overheating nor sparks. In concrete terms, this means in the Atex category 2G temperature class T3: Christian Maier had to make the construction so safe that the surface temperature of the rotating union does not exceed 200 degrees Celsius minus a safety margin under any circumstances. “This limit also applies to extreme situations when foreseeable disruptions occur,” says Florian Maier. Appropriate tests were carried out using temperature sensors and, among other things, intentional bearing damage was carried out in order to determine the temperature behavior of the rotating union. Result: Even under the most unfavorable conditions, the surface temperature of the component remained well below the critical range. This cleared the way to submit the documents and protocols to TÜV Süd, which then issued a safety assessment and Atex approval. 

Friction losses are minimized

The ratio of tightness to friction losses was also optimized as part of the tests. A high contact pressure on the seal leads to maximum tightness, but increases the running resistance of the shaft within the rotary feedthrough. The contact pressure of the seal was adjusted using springs in such a way that the frictional resistance and thus the energy consumption were reduced to a minimum while maintaining the sealing function. With the combination of compressed air motor, rotary feedthrough and three-jaw gripper, PTM mechatronics now has a rational concept for companies that previously either had to invest in a large number of agitators or had to change the use of individual agitators by hand in a less economical way. “Our solution opens up the possibility of automating the mixing of 20, 50 or even more containers,” says PTM managing director Carsten Angermeyer, summarizing the advantages. Thanks to the Atex certification, the systems can also be installed in the chemical or paint industry without any problems.

Transfer of the concept to other industries

After the positive response from the first projects, the inventors at PTM mechatronics and Christian Maier are already thinking one step further. Similar constellations, in which liquids have to be stirred in a large number of containers, can also be found in the food industry – for example in the manufacture of dairy products or beverages. “Here, agitators usually have to meet the FDA standard for contact with food, which can be achieved very well with compressed air drives,” says Carsten Angermeyer. The good cooperation with Christian Maier could then be expanded to include FDA-approved assemblies if required.

PTM mechatronics – we generate movement in special environments.