Abstract: A bicycle derailleur gear changer has a device for guiding the chain and the device has chain-guiding and chain-adjusting pulleys which are mounted between the ends of two cheek plates. The device is movable to effect gear changes by transferring the chain from one to another of sprockets attached to the hub of the bicycle rear wheel. The cheek plates are specially shaped with radial extensions adjacent the chain-guiding pulley, the extensions terminating in turned over edges facing away from the pulley to prevent possible jamming of the gear changer when the chain is driven in the reverse direction.This is a continuation, of application Ser. No. 539,852 filed Jan. 9, 1975 now abandoned.

Abstract: A derailleur gear for a bicycle comprises a chain displacement means having a rigid linkage part movable transversely of the rear wheel in a direction generally along the axis of the rear wheel of the bicycle, the linkage part forming a side link in a support parallelogram linkage that includes vertically movable interconnected link portions connected to the rigid linkage part, the support parallelogram being in a plane generally transverse to the axis of the rear wheel. The chain guide pulley or sprocket is rotatably mounted on a spindle carried by a vertically movable portion of the support parallelogram linkage, as is an elongated cap or arm member that supports a chain tension pulley at a remote end from the spindle-connected end. A coil spring normally resiliently biases the vertically movable portions of the support parallelogram upwardly generally towards the rear wheel axis, and various motion limiting features are included.