Patent ID: 7276899

Claim:
The combination of a positional transducer and a motor driven gear changer for a bicycle, the combination comprising: a motor driven gear changer associated with a portion of a bicycle frame that positions the motor driven gear changer in an operative association with a gear wheel driven by a chain extending between the gear wheel and a pedal assembly carried by a bottom bracket in a portion of the bicycle frame; a transducer operatively associated with the gear wheel for determining the angular position of the gear wheel with respect to pre-set shift points, the transducer having a first fixed element and a first mobile element which are mounted for relative movement with respect to each other about a predetermined common axis; a magnetized element fixed to a selected first element; at least one pair of Hall-effect sensors fixed angularly with respect to one another about the common axis and fixed to the other non-selected first element within the field of the magnetized element; and at least one pair of conductors, each connected to a respective Hall-effect sensor, for outputting signals generated by relative movement of the first fixed element and the first mobile element about the common axis; whereby the transducer is resistant to environmental attacks and prevents errors in the motor driven gear changer by providing indications of chain movement, direction of chain movement and pedal cadence.