Unihammer

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A Unihammer printer ( computer printer ) is just like its relative, the dot matrix printer , an impact printer and also works with a printing matrix .

Unihammers were primarily manufactured by Seikosha in the 1980s and were popular in home computers , especially for Commodore and Atari computers, because of their low price .

technology

In contrast to the dot matrix printer, individually controlled needles do not press the ink ribbon against the paper, but only a vertical hammer. In connection with a toothed roller, which is located behind the paper web and rotates coordinated with the movement of the printing carriage, there is always a point of intersection between the vertical printing hammer and a horizontal tooth. When the print hammer is triggered, a single pressure point is created at this intersection.

A further simplification of the construction compared to a dot matrix printer results from the direct coupling of the carriage drive and that of the toothed roller - the head continues to move during the actual printing; so that a vertical line can be printed, the print hammer is inclined slightly in the printing direction.

Due to the mechanical coupling of the carriage and the toothed roller, the horizontal and vertical resolution is fixed - unlike with dot matrix printers, no different qualities / print resolutions are possible horizontally. The horizontal point spacing results from the distance that the carriage covers while the toothed roller moves on by one tooth. The vertical point spacing is determined by the beat frequency, whose cycle usually z. B. is obtained by a lamellar wheel from the rotation of the roller. As with the dot matrix printer, it would be possible to increase the vertical resolution using micro-feeds, but this was not implemented in any printer model.

Advantages:

  • low manufacturing costs
  • long service life due to simple construction

Disadvantage:

  • strong noise development due to high impact frequency (with MPS 801 ~ 2100 Hz)
  • low and non-variable resolution
  • low printing performance