Ink ribbon

Ink ribbons are part of standard designs for hand- or motor-driven typewriters, teleprinters, stenotype machines, computer-driven printers, and many mechanical calculators.

The prototypical assembly consists of a length of a medium, either pigment-impregnated woven ribbon or pigment-coated polymer tape, and a transport mechanism involving two axles.

At any given moment, most of the length of the medium is wound as a close-spaced spiral around one axle or the other, tight enough for friction among turns to make it behave mostly like a solid cylinder.

There often is a small grommet or eyelet near each end of the ribbon, which activates an automatic ribbon-reversal feature of the ribbon-advance mechanism.

Heavy-duty high-speed line printers may use wider ink ribbons, ranging up to the full width of a 132-column printout, nominally 14 inches (360 mm).

Another alternative design omits the spools, and simply stuffs inked ribbon into a plastic box through a narrow vertical slot, pulling it out the other end as needed.

Some of these spool-less cartridge designs make a half-twist in the ribbon before joining it up into a loop, resulting in a Mobius strip.

With this newer medium, the entire impacted area of the pigment coating adheres to the paper and transfers from the ribbon, producing typed copy with greater uniformity of character shape, reflecting a sharper contrast between the unmarked paper and the pigmented characters compared to cloth ribbons.