Derailleur with improved mechanism for moving and retaining a movable member to and in a desired speed change stage

Claim 1

In a derailleur for a bicycle comprising four members, a fixing member, two linkage members pivoted to said fixing member, and a movable member mounting a chain guide and pivoted to said linkage members, and a return spring carried between two of said four members, so that the cooperative operation of a control cable and the action of said return spring enables said movable member to reciprocate with respect to said fixing member for changing the bicycle speed, the improvement comprising: a control element for setting said movable member in one of a plurality of predetermined positions corresponding to speed change stages, said control element being supported to one of said four members and having a plurality of engageable portions corresponding to each speed change stage defined by reciprocation of said movable member, said engageable portions having engaging faces for each speed change stage and connecting faces for interconnecting said engaging faces; a retainer engageable with one of said engaging faces at said engageable portions of said control element for retaining said movable member in a proper position corresponding to a desired speed change stage, said retainer being supported swingably to another member of said four members which is relatively movable with respect to said one member carrying said control element, said retainer supporting one end of said control cable, said retainer, when said control cable is operated to move said movable member forward with a stroke of said cable less than a given length, being retained in engagement with one of said engageable portions at said control element and, when said cable imparts a stroke over said given length, disengaging from said engageable portions; a tension spring for continuously biasing said control cable in the direction of stretching said cable, said tension spring having one working end, said working end engaging with said retainer to bias said retainer in the direction of disengaging from each of said engageable portions; and, an energy conservation spring for conserving energy when said control cable is pulled against said return spring to swing said retainer, said energy conservation spring having first and second working ends, said first working end engaging with said retainer, said second working end engaging with one of said four members, so that when said control cable is pulled to swing said retainer to disengage the same from said engageable portions, the energy conserved in said energy conservation spring causes said movable member to move rapidly.