| 摘要 |
<p>1. An electrothermal printer comprising a printing support (2) for supporting a sheet (3) to be printed, an ink ribbon (15) arranged adjacent to this sheet and displaced by first drive means (29, 32) and means (21, 16) for producing heating of predetermined surfaces (24) of the ink ribbon so as to transfer the ink from said surfaces onto the sheet,these heating means comprising a printing head (7) comprising a series of first electrodes (21) stressed with a predetermined pressure in the direction of said support and capable of being connected to a first potential during printing, at least one second electrode (22) connected to a second potential different from the first and a heating ribbon (16) independent of the ink ribbon (15), displaced by second drive means (33, 34), inserted at the time of printing between the first electrodes (21) and the ink ribbon (15) and of a composition such that a current passing between the first and second electrodes produces heating in the vicinity of the first electrodes when these electrodes are connected to said first potential, said first and second drive means (29, 32 to 34) being arranged to produce displacement of the ribbons (15, 16) with respect to the printing head (7), characterized in that the ink ribbon (15) and the heating ribbon (16) are contained in a cassette (30) munted on a carriage (45) capable of displacement with respect to the printing support (2), and in that the ink ribbon at least five times the length of the heating ribbon is unwound from a supply spool (31) and wound onto a receiving spool (32) while the heating ribbon (16) is a closed loop, the latter comprising an electrically conductive layer (19) arranged opposite the ink ribbon (15) and in contact with said second electrode (22) and a less electrically conductive layer (20) in contact with the printing head (7), said first and second drive means (29, 32 to 34) being so arranged that the ink ribbon (15) and the heating ribbon (16) are driven at identical speeds with respect to the printing head (7).</p> |
