Image Number 6 for United States Patent #8317420.
In one embodiment, a ribbon cassette includes two rows of spherical bumps extending between sidewalls of the cassette on both a floor and ceiling of the cassette and a pair of concentric arched retaining walls on both the floor and ceiling between an exit gate and the rows of bumps. In another embodiment, there is only one row of bumps and one retaining wall on the floor and ceiling. In another embodiment, the retaining walls are straight. The two rows and retaining walls, along with cassette sidewalls, form three distinct zones for densely packing the ribbon, unpacking the ribbon, and isolating the ribbon, resulting in less jamming with longer lengths of ribbon.