US Patent 11981399 Bicycle derailleur structure

A bicycle derailleur structure is mounted on a bicycle frame to correspond to a flywheel unit and includes a support arm, a screw rod, a tension bar, a gear shift unit. and a drive unit. The tension bar has an end having an interior space receiving an elastic member therein to be mounted on the support arm in an elastically oscillating manner. The gear shift unit includes two protector plates in threading engagement with screw rod, and first and second pulleys arranged between the two protector plates. The screw rod is operable to drive the gear shift unit in order to align a chain on the flywheel unit to align with the gear shift unit.