Thermal ink cassette for a thermal printing device

Claim 1

An improved thermal ribbon cassette for attachment to a thermal printing apparatus having a housing formed by a forward section attached to a rear wall to define a chamber, wherein the improvement comprises: a supply spool rotatably mounted to said forward section and said rear wall and located in said chamber, said supply spool having an ink transfer ribbon continuously wrapped therearound and a plurality of interrupters continuously formed therearound; a drag spring mounted to said rear wall and biased against said interrupters for providing a rotational drag force on said supply spool; a take-up spool rotatably mounted to said forward section and said rear wall located in said chamber; said ink transfer ribbon having one end fixedly mounted to said take-up spool and having a portion extending through slots in said housing such that a portion of said ink transfer ribbon extends external to said chamber; and means for preventing rotation of said take-up spool except in a forward direction, said rotation preventing means comprising said rear wall having a locking pin in said chamber, a first gear rotatably and transversely mounted in said chamber, said take-up spool having a second gear formed thereon in constant mesh with said first gear such that rotation of said take-up spool in the forward direction causes said first gear to transversely displace away from said locking pin and such that rotation of said take-up spool in a reverse direction causes said first gear to engage said locking pin.