Ink-dot printer with magnetic ink attracting and retention preventing

Abstract

An ink-dot printer comprises a magnetic ink storage tank storing magnetic ink, a pair of pole plates facing each other so as to define a slit one end portion of which is contacted with the magnetic ink supplied from the magnetic ink storage tank, an electromagnet for magnetizing the pole plates, thereby feeding the magnetic ink from the magnetic ink storage tank into the slit to form a magnetic ink curtain in the slit, and a plurality of needles arranged adjacent to one another along the longitudinal direction of the slit and adapted selectively to move in the longitudinal direction thereof between a first position where one end portion of each needle is immersed in the magnetic ink curtain in the slit and a second position where the one end portion is projected from the magnetic ink curtain in the slit, the cross-sectional area of the one end portion of each needle being made to narrower than that of the remaining portion of the needle so that the distance between the one end portions of any two adjacent needles is widened to prevent the magnetic ink from being retained between the portions adjacent to the end faces of the one end portions by surface tension when the two needles are simultaneously located in the second position.