Rotating the smooth, unthreaded driveshaft through the series of ring bearings, with specially contoured inner races, creates compression and friction that drive the bearing housing back and forth.
Continuous vibration from a diesel engine powering a sizable sea-going vessel shook apart conventional lever throttles with mechanical linkages. The resulting "play" decreased throttle accuracy and efficiency, and caused excessive maintenance. The problem prompted design engineers at a large European shipbuilder to develop an engine throttle control system that uses a "rolling-ring" linear actuator to control the throttle adjustment arm's advances and retractions.
On the ship's bridge, a transmitter potentiometer sends an electronic signal to a variable speed gearmotor located in a water-tight box in the engine room. Since the output shaft on the variable-speed gearmotor holds a spur gear that meshes with a gear on the rolling ring linear actuator drive shaft, the signal generates the appropriate gearmotor response to rotate the drive shaft. The rolling ring actuator moves when the drive shaft turns, and is attached to the throttle adjustment arm via a metal bracket.
Equal resistance values of the transmitter and receiver potentiometers trigger a switch that shuts off the motor. Moving the speed control on the bridge reactivates the system, and switches the motor back on. The system not only overcomes the vibration problems, but also is said to dramatically reduce maintenance because the design lends itself to being sealed against the intrusion of moisture, dirt, and debris.
Mark Wilson, Amacoil Inc., Box 2228, 2100 Bridgeton Rd., Aston, PA 19014; Tel: (800) 252-2545; Fax: (610) 485-2357; E-mail: firstname.lastname@example.org.
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