Bicycle front deraileur with a smooth gear switching mechanism

摘要

A bicycle front derailleur with a cam level for smoother gear switching is disclosed. The bicycle derailleur is operated by pulling a wire which shifts a chain between at least a large sprocket, a medium sprocket and a small sprocket. The bicycle front derailleur contains a cam lever which is pivotably connected to a four-linkage chain guide moving system at a pivoting point for pulling the chain guide moving system, and thus shifting the chain, when a cable is pulled in a pulling direction. The cam lever has a cam groove formed on the peripheral surface of the cam lever for receiving the wire. The cam lever is structured such that the radial distance between the cam groove and the pivoting point increases in a direction opposite of the pulling direction, so as to provide a greater effective length vertical to the pulling direction when the wire is subject to a greater linear displacement resulting in a greater counterforce. Such an increased effective length provides a greater torque at the same pulling force.