| 摘要 |
A matrix printer includes a printing head which incorporates a plurality of printing needles (11), each of which can be maneuvered individually with the aid of a respective electromagnetic maneuvering device (10), by means of which the printing needle (11), carried by a spring-biassed, movable armature (12), can be caused to carry out a working cycle, upon activation of the maneuvering device, this working cycle including a working stroke, during which the needle (11) is moved in a direction towards a printing anvil (20) for the purpose of printing a punctiform sign on a record carrier (21) located in front of the printing anvil, and a subsequent return stroke, during which the printing needle (11) is returned to a withdrawn rest position. For the purpose of enabling simple inexpensive, but nevertheless reliable monitoring of the manner of working of the printer, it is proposed that the movement of at least one printing needle (11) during at least a part of a needle working cycle is monitored by detecting changes in the magnetic flux in the magnetic circuit (12, 14) of an associated maneuvering device (10) caused by movement of the needle (11). |
