Printing apparatus with a thermal print head

Claim 1

A printing apparatus for printing on a sheet of paper via a thermal ribbon having a thermally transferable ink layer, comprising: a paper feeding device for feeding the sheet of paper; a thermal print head including heat generating elements which are held in pressed contact with the surface of said sheet of paper via said thermal ribbon, said heat generating elements being selectively energized to apply heat to said ink layer of the thermal ribbon to fuse the ink for adherence of the fused ink to the surface of the paper; a first pair of rollers disposed on opposite sides of a path along which said sheet of paper is fed toward said thermal print head, and a second pair of rollers disposed on opposite sides of said path, said first and second pairs of rollers applying a tension to a portion of said sheet of paper between the first and second pairs of rollers; a detecting device disposed between said first and second pairs of rollers in the direction of feed of said sheet of paper for sensing the surface smoothness of said sheet of paper fed by said paper feeding device; a print-quality improving device for improving the quality of printing on said sheet of paper, said print-quality improving device being disposed downstream of said detecting device in said direction of feed of said sheet of paper; and a control device connected to said detecting and print-quality improving devices and activating said print-quality improving device while said surface smoothness sensed by said detecting device is lower than a preset lower limit, said control device deactivating said print-quality improving device while the sensed surface smoothness is not lower than said preset lower limit.