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

摘要

Abstract of the DisclosureIn a dot matrix line printer in which a pluralityof hammer springs mounted along the length of an elongatedreciprocating hammerbank are selectively released or firedto impact dot printing impact tips mounted thereon against aprint paper through a length of ink ribbon to print dots, thewear that would otherwise occur each time one of the hammersprings rebounds back into contact with a pair of pole piecesagainst which the hammer spring resides when in its retractedposition is greatly minimized by chromium masses plated onthe tip of the hammer spring and on the tips of the polepieces. Chromium platings on each hammer spring are confinedto the end of the spring and comprise either a pair of massesadjacent the different pole tips or a single mass encompassingboth pole tips. The chromium masses are of convex contour andof hexavalent chromium composition to provide the masses withhard and smooth surfaces that slide over and do not abradeone another upon impacting.