Patent attributes
The present invention refers to a bicycle gearshift with improved precision control, which comprises a kinematic mechanism in the form of a four-bar linkage with a base body and a mobile body connected together through a pair of connecting rods articulated to the base body and to the mobile body at four pin elements, each pair of opposite pin elements of the four pin elements defining a diagonal of the four-bar linkage-kinematic mechanism, the base body comprising a first attachment group to a bicycle frame and the mobile body being connected to a chain guide at a second attachment group, the four-bar linkage-kinematic mechanism being associated with gearshift actuation means suitable for deforming the four-bar linkage-kinematic mechanism so as to determine a displacement of the mobile body with respect to said base body and consequently a primary displacement of the chain guide in the axial direction with respect to the axis (A) of a cogset, at least one from the first attachment group and the second attachment group comprising a chain tensioning spring, the chain tensioning spring determining a set-up of the chain guide when engaged with a chain of a bicycle transmission, and it is characterized in that it comprises a kinematic mechanism for adjusting the preload of the chain tensioning spring as a function of the primary displacement of the chain guide so as to determine a variation in the set-up of the chain guide.
