Image Number 2 for United States Patent #4406643.
A derailleur for a bicycle, which is so constructed that a movable member is supported to a base member through two linkage members, a changeover frame having two pulleys carrying thereon a driving chain is pivoted to the movable member, and a tension spring is interposed between the movable member and the changeover frame, so that the tension spring exerts tension on the driving chain, said changeover frame being subjected to resistance against its swinging motion in a direction opposite to the working direction of the tension spring, thereby swinging the changeover frame easily in the direction of working of the changeover frame, while, requiring more force in the reverse direction to the working thereof, thereby making swinging of the changeover frame in the working direction of the tension spring easy and more difficult in the swinging motion direction opposite to the working direction of the spring.
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