Image Number 2 for United States Patent #4053042.
An endless ribbon cartridge for supplying ribbon to an external printing station with relatively uniform tension and including an anti-fouling mechanism to prevent snarling of the ribbon as it re-enters the cartridge. The cartridge comprises a two-piece housing having a cover and a main body portion with separate exit and entrance slots and interior boundary walls partially defining a ribbon chamber having entrance and exit portions. An endless ribbon is partially received within the chamber in random folds, the remainder of the ribbon traversing a looped path from the chamber exit portion through the housing exit slot and the housing entrance slot to the chamber entrance portion. A capstan and pinch roller assembly is provided adjacent the entrance slot to translate the ribbon along the looped path. Tensioning is located at the chamber exit portion, and optional additional tensioning is located at the exit slot, providing a drag force for maintaining the ribbon tension at the external printing station substantially uniform. These tensioning devices are comprised of a simple spring member having a blade portion and an offset central hub, the spring member being mounted in a flexed position. The boundary wall adjacent the exit portion of the chamber is provided with a relieved channel which receives a mating boss depending downwardly from the inner surface of the cartridge cover member in order to limit motion of the exiting ribbon in the direction transverse to the desired translational direction.