Hybrid spring for bicycle derailleurs

摘要

A parallelogram link mechanism of a bicycle derailleur has a coil spring tensioned from a first axis of the parallelogram to another axis thereof that is diametrically opposed to the first axis. The coil spring exerts a primary spring force against the rider-supplied derailleur actuation force throughout the actuation range of the derailleur. A secondary member exerts a secondary force throughout a portion of the actuation range of the derailleur, producing a substantially constant resultant actuation force experienced by the rider. The secondary member can take various forms, including an abutment member which selectively abuts the coil spring at an angle to the spring axis; a second spring internal to the first; a member which is attached to spaced-apart coils of the coil spring to limit their linear expansion; and an internal member which limits constriction of a segment of the coil spring inwardly toward the spring axis.