Machine Design

Scanning for Ideas: Linear actuators built for hazardous locations

GSX linear actuators from Exlar Corp., Chanhassen, Minn., are available with CSA Class I, Division 2, Groups A, B, C and D certification. This means they can be used in places near flammable gases and vapors. They will not initiate an explosion due to arcing contacts or equipment with high surface temperatures, according to tests.

The actuators combine a brushless servomotor and an inverted roller screw in a compact assembly. They can serve in closed-loop servosystems where electronics control position and velocity. The actuator’s terminal box features standard NPT entry ports, along with power and feedback terminals.

The brushless servomotor offers a segmented lamination stator (T-LAM) with each stator segment containing individual phase wiring. This lets the actuator provide more continuous motor torque than traditionally wound motors. The roller screw has several threaded helical rollers assembled in a planetary arrangement around an internally threaded cylinder. It converts the motor’s rotary motion into linear movement of the shaft or nut. It also increases the amount of contact surface compared to traditional roller screws, so it is stronger with up to 15 times the life of Acme screws or ball screws. The actuator’s lead accuracy is 25 μm/300 mm and can be supplied with zero backlash. The actuators are available with resolver feedback and handwheel options.

A sealed output rod lets the actuator use a bushing and seal, which keeps abrasive particles and other forms of contamination out of the actuator’s critical mechanisms and ensures reliable operation in severe environments.

© 2011 Penton Media, Inc.

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