Typewriter Ribbon

A typewriter ribbon is an expendable module serving the function of transferring pigment to paper in various devices for impact printing. Such ribbons were part of standard designs for hand- or motor-driven typewriters, teleprinters, stenotype machines, computer-driven printers and many mechanical calculators, before electronic alternatives replaced most of them.

The module 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 between turns to make it behave mostly like a solid cylinder. Rotation of the axles moves the ribbon or tape after each impact and usually aids in maintaining tension along the roughly straight-line path of the medium between the axles. The module may itself include mechanisms that control the tension in the temporarily unwound portion of the medium.