Control of media movement using a periodic calibration method and

Abstract

A ribbon supply apparatus including a support in which a ribbon supply spool and a take-up spool are rotatably mounted. The supply and take-up spools and the support are designed so that these spools can be mounted in the support in only one way, the correct way. The ribbon is supplied on a tubular core member which is mounted on a cylindrical member which is part of the supply spool. The ribbon supply spool has a large gear thereon which is used in a braking and feeding mechanism which is used to incrementally feed the ribbon to a print station associated with the apparatus. The ribbon take-up spool is identical to the ribbon supply spool, but the ribbon take-up spool is mounted in a reversed manner when compared to the ribbon supply spool. A driving gear, coupled to the large gear on the take-up spool is part of the braking and feeding mechanism which also includes a 'dancer arm'. The dancer arm controls a loop of ribbon which is fed to the print station. A velocity sensor (including a roller and a timing disc) is positioned between the print station and the take-up spool and is used in providing a measure of the velocity of the ribbon being moved from the print station. Outputs from the timing disc are used in determining the number of steps which a stepping motor driving the take-up spool must be incremented by a controller to move a predetermined amount of ribbon to the print station.