Patent ID: 8033937

Claim:
An actuator device for a bicycle gearshift, comprising an actuation mechanism that is driven by a drive member that in turn drives a derailleur of a gearshift, wherein said mechanism comprises at least one member which is capable of elastically yielding when subjected to a stress above a predetermined stress threshold, wherein the drive member comprises a motor and a threaded drive shaft rotated by the motor, wherein the mechanism comprises: an articulated quadrilateral with at least four connecting rods hinged together about at least four pin axes by at least four pin elements, wherein a first connecting rod is fixed to a bicycle frame, and a second connecting rod is opposite the first connecting rod in the articulated quadrilateral and is fixed to a support for the derailleur; a support for the motor associated with a first of the pin elements; and a nut associated with a second of the pin elements, opposite the first, the nut engaged with the drive shaft so that the action of the motor moves two opposite first and second pin elements closer and farther away, deforming the articulated quadrilateral, said nut comprising an internally threaded tubular sleeve engaged with the drive shaft, and the member which is capable of elastically yielding, wherein the elastically yielding member is positioned about the tubular sleeve and permits pivotal movement of the connecting rods with respect to each other without regard to whether the motor is rotating the drive shaft, the nut further comprising: an internally hollow tubular body surrounding a portion of the internally threaded tubular sleeve that slides axially in the tubular body; two abutment surfaces in the axial direction formed at opposite ends of the tubular body; two opposite pin portions integral and perpendicular to the tubular body; two protruding abutment collars provided on the tubular sleeve at opposite ends; and the elastically yielding member is a spring inserted on the tubular sleeve, compressed between a first of the abutment collars of the tubular sleeve and a first of the abutment surfaces of the tubular body, and a second of the abutment collars of the tubular sleeve facing a second of the abutment surfaces of the tubular body due to the elastic thrust of the spring.