Ribbon cartridge construction

Claim 1

In a ribbon cartridge construction having a housing including means forming a ribbon access window at the outer perimeter thereof for exposing a run of ribbon for printing on an oppositely facing surface, a ribbon inlet aperture and a ribbon outlet aperture on either side of the window for the passage of ribbon into and out of the housing and means disposed adjacent said window for shielding all but a predetermined portion of the exposed ribbon from an oppositely facing surface, the improvement wherein: the shielding means comprises a resiliently flexible planar shield including a shielding portion configured to cover the exposed run of ribbon and having a printing aperture corresponding in size to said predetermined portion of the exposed ribbon and first and second elongated mounting arms extending outwardly from the shielding portion in opposite directions and configured to be slidably received in the ribbon inlet and outlet apertures to dispose the shield in an operative position wherein the printing aperture is aligned with the predetermined portion of the exposed ribbon upon the full insertion of both arms; the ribbon inlet and outlet apertures have a width sufficient to receive the mounting arms outwardly of a ribbon passing therethrough; and the cartridge construction further comprises one-way locking means disposed on the first arm and adjacent the corresponding one ribbon aperture for permitting the sliding insertion of said first arm into the one ribbon aperture and for preventing subsequent removal thereof; wherein the one-way locking means comprises a hole in said first arm, guide means disposed adjacent said one ribbon aperture and forming a guide path receptive of said first arm upon insertion in the one ribbon aperture and a first locking projection in the guide path and engageable with said hole.