Gear change mechanism for bicycles - has parallelogram linkage fitted to rear wheel hub with register mechanism

摘要

The gear change mechanism for bicycles fits onto the rear wheel hub. It has a fixed transverse upper carrier and a lower movable carrier that is connected to the chain guide. The carriers are linked together to form a parallelogram. The change element pivots on the upper carrier. It performs two functions. It moves the lower carrier to the required transverse position and it acts as a register retaining the carrier in one of a series of preset positions. There are limit stops to prevent excess movement of the lower carrier. A chain guide is fitted to the lower carrier and the change element is operated by a twin cable. The register is achieved with a ball fitting in one of a group of spherical recesses.