| 摘要 |
Ink printing mechanisms operate with a very low degree of noise and, because of the possible high print frequencies, can be used advantageously as output printing mechanisms in data processing systems. It is a disadvantage with these printing mechanisms that the outlet openings of the outlet jets can be easily blocked by ink slugs. As a result of this, uniform formation of ink droplets which is required in order to achieve a uniformly good print quality is no longer possible. It is the object of the invention to detect the failure of droplet formation of the individual outlet jets at an early point. For this purpose, monitoring characters are produced on the edge, located outside the printing area, of recording carriers (1) which are then scanned by a sensor device (53) consisting of an optical transmitter (61) and an optical receiver (63). By means of a counter unit (65), the points are counted and compared with a reference value point number in a comparator (65). When this reference value point number is not attained, either a warning signal is generated or the machine is switched off so that no more poor quality print can be produced. <IMAGE>
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