The indexer was initially developed for bicycle gear shifting to keep rides within a predetermined pedaling cadence range.
A patented mechanical indexer indexes a fixed number of degrees when the motor input shaft reaches a preset speed. The initial 2.5-inch diameter model has five indexes and rotates through 17 degrees. For other models, the angle varies by the number of indices and size of the unit. When a preset speed is attained, a flyweight with a helical segment engages and interlocks with a helical thread on the inside bore of the housing. This action advances the output drum one index. If the input shaft drops a fixed amount below the present speed, the mechanism will index back to its original start position. If the input shaft speed drops to a speed between the advance and return speed, a ball-detent mechanism will stop indexing and hold position. The speed differential at which the indexer will advance, hold, or return is adjustable by changing the helix' circumferential position. Applications include advance or retard speed indexing such as on bicycle shift mechanisms.
Oliver Tysver, T DESIGN LTD, W76N1062 Hampton Ave; Cedarburg, WI 53012 Tel: (262) 375-8727; E-mail: [email protected].
For more information, enter 509 at www.designnews.com/info.
Submit your ideas and rough drawings for this section to Rick DeMeis, Designer's Corner, Design News, 275 Washington St., Newton, MA 02458