Matrix printer with magnetic fluid for fixing printing needles - uses individual energising coils to increase response speeds by eliminating magnetic gap

摘要

The magnetic fluid in this type of matrix printer fixes selected needles in the forward position due to its high viscosity when energised for printing, resulting in a very compact printing head. The response speed is increased by attaching each needle to a freely moving coil, thus eliminating the magnetic gap. Each of the 35 printing needles is attached to the coil former (3) on which a coil (7) with connections (8,10) is wound. This coil moves freely within a tube (5), the gap between coil and tube being filled with a magnetic fluid (9). A similar principle is used for fixing the printing head in the forward position during the printing mode.