IMPACT PRINTER HAVING WEAR-RESISTANT PLATINGS ON HAMMER SPRINGS AND POLE PIECE TIPS

摘要

In a dot matrix line printer in which a plurality of hammer springs mounted along the length of an elongated reciprocating hammerbank are selectively released or fired to impact dot printing impact tips mounted thereon against a print paper through a length of ink ribbon to print dots, the wear that would otherwise occur each time one of the hammer springs rebounds back into contact with a pair of pole pieces against which the hammer spring resides when in its retracted position is greatly minimized by chromium masses plated on the tip of the hammer spring and on the tips of the pole pieces. Chromium platings on each hammer spring are confined to the end of the spring and comprise either a pair of masses adjacent the different pole tips or a single mass encompassing both pole tips. The chromium masses are of convex contour and of hexavalent chromium composition to provide the masses with hard and smooth surfaces that slide over and do not abrade one another upon impacting.