| 摘要 |
In electrothermic printing devices for dot matrix character printing without stroke on recording media (1) by means of an electrically conducting ink ribbon (2) and by means of recording electrodes (8), cleaning of the print head (7) with the recording electrodes (8) is required in order always to achieve clearly demarcated dot matrix characters on the recording medium (1). For this purpose, electrothermic printing devices are available, in which the ink ribbon cassettes have to be exchanged for a cleaning cassette when required. The underlying object of the invention is to simplify this cleaning operation in such a way that the person operating the machine no longer has to check when cleaning is required. This object is achieved in that the ink ribbon (2), having a layer of meltable particles facing the recording medium (1), has on its side facing the electrodes (8) at least one portion which is covered with cleaning material. By this means, automatic cleaning of the print head (7) is achieved after a certain number of printing operations. The print head (7) is cleaned independently of the assessment of the writing quality by the operator, by which means exact dot matrix characters are always achieved on the recording medium (1). <IMAGE> |
