Dot printer head with reduced magnetic interference

A dot printer head comprising an annular plurality of armatures each mounted for motion to actuate a needle, a spring for urging each of said armatures in a printing direction, a permanent magnet on which cores holding faces are formed in a plane perpendicular to a line connecting said cores and said plurality of armatures, a yoke providing a magnetic path between said permanent magnet and said armatures, and an annular plurality of cores each having a mounting portion contacted with one said core holding face of said permanent magnet, each of said cores further having a post-like projection which extends from said mounting portion and has an electromagnetic coil held thereon, the area of each said mounting portion which is contacted with said core holding face being greater than the area of the cross section of said post-like projection, said cores being secured to said permanent magnet in spaced relationship from each other in an annular row on said core holding faces of said permanent magnet, said area of said mounting portion defining a trapezoid having sides defined by radii of said annular row so that said area of said mounting portion is maximized.