Hammer block assembly for line printer

Claim 1

A print hammer assembly including a support constructed to permit interchange of print hammers manufactured within a tolerance limit; a plurality of print hammers each including a head of rectangular cross section having a pair of opposed first surfaces and a pair of opposed second surfaces, a portion of rectangular cross section spaced longitudinally of the hammer from said head and having a pair of opposed third surfaces and a pair of opposed fourth surfaces aligned approximately parallel within a tolerance limit with the first and second surfaces respectively; said support including first guide means engaging the pair of first surfaces of each hammer to locate the heads in line and second guide means engaging the pair of second surfaces of each hammer to locate the heads in spaced relationship along the line with the second surfaces of the hammers parallel to one another said first and second guide means permitting longitudinal movement of each hammer towards and away from a corresponding print area; first locating means engaging the pair of third surfaces of each hammer to locate said portions in a direction transverse to said line and second locating means spaced from said second guide means engaging the pair of fourth surfaces of each hammer at a single pair of opposed areas of small transverse extent relative to the transverse dimension of said fourth surfaces to locate the portions in spaced relationship corresponding to the spacing of the head and maintain the hammers substantially parallel to one another, the fourth surfaces being unrestrained through the remainder of their transverse dimension and the hammers being unrestrained between the respective second guide means and the second locating means to thus avoid jamming during longitudinal movement of the hammers due to misalignment of said portion relative to the head of the respective hammers.