Patent ID: 7611430

Claim:
A transmission system, comprising: a chain; a sprocket cluster comprising a plurality of transmission sprockets having different outer diameters, the sprockets of the sprocket cluster being arranged along a common sprocket axis; a changing mechanism and an operation cable for use in operating the changing mechanism, the changing mechanism being detachably linked to the operation cable, the changing mechanism being operable to move the chain in an axial direction of the sprocket cluster such that the chain moves from one transmission sprocket to another among the sprocket cluster in response to movement of the operation cable, the changing mechanism comprising a linking part which detachably links the operation cable to the changing mechanism; and a transmission case for housing the sprocket cluster, the changing mechanism and the chain, the transmission case comprising an axially-directed case wall having a work opening formed therein, and a radially-directed case wall having an operation opening formed therein through which an end portion of the operation cable extends; wherein the operation cable and the linking part of the changing mechanism may be accessed via the work opening in the axially-directed case wall of the transmission case component to permit connection or disconnection of the operation cable, and wherein the chain may be lubricated via the work opening; wherein the work opening is located closest in the sprocket axis direction to a transmission sprocket having the largest outer diameter among the sprocket cluster, and wherein the transmission sprocket having the largest outer diameter, within the sprocket cluster, is also located closest to the work opening in a direction radial to the sprocket axis.