Segmented-ring magnet print head

Abstract

A print head for a serial dot matrix printer comprising a sandwich structure including a base plate, a segmented-ring magnet, a print hammer disc and face plate is disclosed. The segmented-ring magnet comprises a ring formed of a magnetic material having spaced apart, magnetized, regions (segments). The print hammer disc is formed of a magnetically permeable, resilient material and has a plurality of inwardly projecting arms (hammers), each of which is aligned with a magnetized segment. Mounted on the hammers are print blades, which are aligned with radial slots formed in the face plate. Each print blade includes a dot-printing tip that projects orthogonally outwardly from the blade, and lies in a central aperture in the face plate. Mounted on the base plate, in line with each hammer, is a post having a coil mounted thereon. When the coils are de-energized, the magnetic field formed at the tips of the posts is adequate to overcome the spring force of the related hammer, whereby the air gap therebetween is closed and the hammer is cocked. Energization of any coil by a pulse of appropriate polarity and magnitude cancels the magnetic pull created by the related magnetic segment and allows the related hammer to pull away from the related post. This action creates a dot as the released spring force causes the dot-printing tip of the related print blade to press a print-producing material (e.g., a ribbon) against a print receiving medium (e.g., a sheet of paper). Rather than defining a single column, the dot-printing tips define two or more columns.