Ink ribbon feed

Thermal printing apparatus including a print head comprising a plurality of selectively heatable thermal printing elements;

• means to feed a print receiving medium past the thermal printing elements;
• a thermal transfer ink ribbon and means to guide said thermal transfer ink ribbon between the thermal printing elements and the print receiving medium, said ribbon having an ink layer adjacent to the print receiving medium;
• pressure means to urge the print receiving medium into intimate contact with the ink layer of the ribbon and to urge the ribbon into heat transfer relationship with the thermal printing elements, said intimate contact between the ink layer and the print receiving medium being effective to feed the ribbon with the print receiving medium;
• driven take up means to draw used ribbon from the print head;
• a guide edge disposed between said print head and said take up means, drive means to drive said take up means to apply tension to said used ribbon in a direction at an angle from the surface of the print receiving medium such that the used ribbon wraps around the guide edge and is drawn from the surface of the print receiving medium;
• sensing means comprising a pivoted member having a free end engaged by the used ribbon when the ribbon is in a tensioned state to pivot the member to a first position with its free and adjacent said guide edge and means resiliently urging said pivoted member toward a second position in which said free end is spaced away from said guide edge, and said sensing means including means to generate an electrical signal when the member is in one of said positions to control energization of the drive means, said sensing means being responsive to the used ribbon being in a non-tensioned state to energize said drive means and responsive to the used ribbon being in a tensioned state to terminate energization of the drive means.