Printing head for high speed dot matrix printer

Claim 1

A printing head for a high speed dot matrix printer comprising: a frame; a plurality of electromagnets, mounted in an arcuate array, each electromagnet including an fixed magnetic structure having a central axial aperture and a coil mounted within the fixed magnetic structure in symmetrical coaxial alignment with its central aperture, the projected axes of said central apertures of said electromagnets converging toward and extending through a print location in a predetermined pattern; a corresponding plurality of elongated,stiff, linear printing rods, each extending coaxially through the central aperture of an associated electromagnet, to a point immediately adjacent to said print location; a corresponding plurality of magnetic armatures, one for each electromagnet, each armature being affixEd to the outer end of the printing rod for its electromagnet in coaxial alignment with said printing rod to afford a print rod assembly for the associated electromagnet, said print rod assembly being the only structure located in said central aperture, energization of the electromagnet coil driving the armature toward abutting engagement with the fixed magnetic structure; fixed inner end guide means, engaging only a limited inner end portion of each of said printing rods, for maintaining the inner end of each printing rod in co-linear alignment with the axis of the central aperture in its associated electromagnet and in alignment with said predetermined pattern; and a corresponding plurality of individual, independent suspension springs, each affixed to the outer end of the fixed magnetic structure of one electromagnet and to the outer end of the print rod assembly for that electromagnet; one of said suspension springs and said inner end guide means constituting the sole support for the entire print rod assembly for each electromagnet, maintaining both said armature and said print rod in coaxial linear alignment with the central aperture of the fixed magnetic structure and totally free of engagement with said central aperture at all times and limiting the print rod assembly and the fixed magnetic structure to abutting engagement of the armature and the fixed magnetic structure whenever the coil is energized, whereby friction losses in operation are limited to frictional engagement of the printing rods with the inner end guide means and internal friction in the suspension springs.