Mechanism for shifting the track position of a multi-track ink ribbon in a printer

Claim 1

In a ribbon track selecting mechanism for use with a printer having a ribbon cassette table with a ribbon cassette supported on an upper side thereof, the ribbon cassette containing a ribbon on a front side thereof facing a platen, wherein the ribbon is provided with a plurality of color tracks extending in a length direction of the ribbon and arranged in order vertically in a width direction of the ribbon, a carriage movable in a longitudinal direction along the platen, wherein the ribbon cassette table is supported vertically above the carriage and is shiftable by the ribbon track selecting mechanism in a vertical direction perpendicular tφ the longitudinal direction, in order to shift a selected one of the color tracks of the ribbon to a printing positon in front of the platen; the improvement wherein said ribbon track selecting mechanism comprises: a pair of support arms oriented in the vertical direction having one of their ends pivotally mounted to opposing lateral sides of said ribbon cassette table in the longitudinal direction and positioned toward a rear side of said ribbon cassette table remote from said platen, and having the other of their ends pivotally supported on said carriage, wherein said support arms may pivot freely to support movement of said rear side of said ribbon cassette table in the vertical direction; ribbon driving means mounted on a bottom side of said ribbon cassette table toward the rear side thereof adjacent said support arms, said ribbon driving means being drivingly connected to said ribbon cassette; a drive mechanism including a drive plate having one end pivotally mounted to a front side of said ribbon cassette table toward said platen, and a stepping motor mounted on said carriage below said ribbon cassette table and driving a drive gear engaged with engagement means on the other end of said drive plate, wherein said one end of said drive plate on the front side and said one ends of said support arms on the rear side of said ribbon cassette table define a plane which is selectively shiftable in the vertical direction by said drive mechanism to bring the selected one of the color tracks of the ribbon in said ribbon cassette to the printing position; and a detent mechanism for stopping and holding said drive plate in selected shift positions corresponding to positioning the color tracks, respectively, at the printing position, said detent mechanism including a detent cam rotatable on an axis together with said drive gear and having a cam surface formed with detent recesses corresponding to the selected shift positions of the color tracks, and a detent member for engaging in the corresponding one of said detent recesses of said detent cam at each selected shift position.