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Engineers who need to monitor shaft speed have available a new device that makes mounting the sensor easier and protecting the speed bump virtually foolproof. The patent-pending Whirligig, from 4B Components Ltd. of East Peoria, Ill., has been met with applause at granaries in the U.S. midlands.

Grain processors use horizontal and vertical conveyors, some of which are fitted with buckets, for moving grain around. Monitoring speed on the tailshaft side of a belt conveyor, because it is located opposite the driven headshaft, is the quickest way to make sure that the conveyor does not succumb to overload. If the rotational rate of the tailshaft drops by a certain specified amount, then the sensor can trigger an alarm or shut down the motor.

Until now, however, there was no convenient way to guard the key, key way, or bolt, which serves as a once-per-revolution discontinuity that is detected by the proximity sensor. A second difficulty was that each speed sensor often required a custom bracket to make it work.

The polypropylene Whirligig bolts right up to the end of a shaft using a 1/2-13 tapped hole. A cover conceals a twice-per-revolution target. Any standard cylindrical or DIN-style inductive sensor mounts with little fuss to the Whirligig's base plate. The company can provide the device with a speed switch, a slip switch, or a stop switch, plus 30 mm or 18 mm proximity probe brackets, and 1/2 or 3/4 NPT conduit adapters.

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Title Annotation:electric sensor
Author:Sharke, Paul
Publication:Mechanical Engineering-CIME
Article Type:Brief Article
Geographic Code:1U3IL
Date:Nov 1, 1999

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