Piston air motor with stall characteristics
January 1st 2008

For stop/start applications where the drive speed is low and torque high, the piston air motor is a suitable choice.

Aluminium foil tray manufacturer Coppice Alupack is systematically replacing all its electric drives on rewind systems that handle the surplus foil after the aluminium coil has been stamped. Inclusion of Huco Dynatork air motors has not only simplified the design but also made it more controllable and safer. Webbing or lacing is left after the foil is stamped and blown to form aluminium containers. Much of this is gravity fed out of the press. On certain tools however it needs to be rewound and its tension maintained allowing containers to be ejected cleanly and assist new foil to be fed-in efficiently.

The original system for rewinding this material had its problems. Its electric drive with limit switches and inverter for speed control made for a complicated design and the high torque involved presented a degree of risk to the operators when removing the coiled lacing. A Deritend is qualified to repair, certify, install and commission electric motors for use in ATEX zoned environments. While traditional ATEX industries such as petrochemical processing facilities are used to conformity, Deritend is warning that motors without correct certification are likely to be used in ATEX zone 20 to 22 dust conditions. Previous regulations for explosive atmospheres did not account for the risk of explosion created by dust. There have been several large explosions investigated in areas such as crop storage, food processing, coal processing and plastics that are attributed to dust. Companies not using motors that have been certified by the supplier or repairer are liable should anything go wrong, under ATEX 137. Zone classification is the responsibility of the company on whose premises machinery is operating. It is also the responsibility of any company manufacturing machinery or repairing machinery that may create a risk or is designed to be used in a risk area. The zone classification depends on the type of hazard present and the duration that machinery is exposed.

Explosive gases such as hydrogen and vapours produced by petrol for example are zoned 0,1 or 2 based on the frequency of their presence and their concentration.

Dust laden atmospheres created by activities such as composite woodworking and flour production are zoned 20, 21 and 22 based on the level of exposure. Settled dust is also included, this can fall into any of the three categories.

Saves costs and emissions For large gear reductions Automated crane For the assembly of servomotors used in automation applications Huntsman Advanced Materials SEW-EURODRIVE uses Araldite epoxy casting systems for embedding the stator wiring in the motor housings. By using Araldite CW 229/Aradur HW 229-1 casting system from Huntsman Advanced Materials, to embed the stator winding, SEW-EURODRIVE get solid and reliable electrical insulation on these components which is effective at dissipating heat in an environment where maximum permanent temperatures are around 155ºC. Araldite CW 229 resin with Aradur HW 229-1 hardener is a liquid, hot curing twocomponent epoxy casting system containing mechanically reinforced fillers. This system is readily processed into a resilient polymer said to have excellent mechanical and electrical characteristics.

re-design was clearly needed and the Huco Dynatork air motor offered many advantages.

"Stall characteristics were the main features we were looking for as well as compact design and ease of installation," explained engineering manager, James Lamin. "As we obviously work to food standards the replacement motor needed to be robust and clean." Trial units were readily available from Huco Dynatork to test the concept before order placement and technical back-up provided to optimise the design. The Huco Dynatork motors run from 0 – 220 rpm for 24 hours a day in a cycle that goes from stall to start in the order of sixty times per minute. "They have worked very well," James Lamin concludes.

"Three units are now running on the shop floor and we have plans for more as the year progresses."

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