Print hammer and interposer captivating linkage

In an impact printer having a printer frame to which is mounted carrier means for periodically presenting a plurality of type die to a print line adjacent a document on which a printing operation is to be performed, and a print impacting mechanism, including at least one print hammer arranged to impact the document with selected ones of the type die at the print line, a source of mechanical energy including an impeller having at least one impeller tooth rotating in synchronism with the periodic presentation of the type die by the carrier means, an interposer having a mass smaller than the mass of the hammer and associated with the hammer and arranged for selective movement by a control element from a normal position into the path of motion of the impeller tooth such that the impeller tooth engages the interposer driving it and the associated print hammer from a rest position toward the print line to impact the document with a selected type die, said impeller tooth and hammer having the same plane of motion;

• said print impacting mechanism being characterized by the print hammer having a pair of spaced apart and generally parallel surfaces defined by a base end, a hammer head end and by a front and a back edge, the hammer head end having a hammer face toward the front edge and an interposer striking face toward the back edge, first and second spaced apart portions projecting from the back edge near the hammer head and base ends, respectively, with the base end being secured to the printer frame to allow pivotal motion of the hammer;
• by said interposer having a length 1 and a generally rectangular cross-section of dimensions x and y, where x is greater than y, and which is arranged to have its surface defined by the x dimension engaged by said impeller tooth;
• by said interposer being mechanically coupled to said print hammer in a linkage which allows motion of the interposer into and out of the path of said impeller tooth and captivates the smaller mass interposer to travel with the larger mass hammer after engagement of the interposer by the impeller tooth;
• by said interposer being flexible in the plane of motion of said hammer and impeller tooth and flexing in such plane when engaged by the impeller tooth such that a relatively smooth accelerating force is imparted to the print hammer and such that the removal of the interposer from the path of the impeller tooth and return to the normal position after such engagement is enhanced by such flexing and by the captivation linkage to the print hammer;
• said linkage being characterized by an aperture through said second portion in a direction generally parallel to said surfaces and large enough to allow insertion of the interposer with its x dimension parallel to said surfaces and to also allow rotation thereof until its y dimension is parallel to said surfaces and further characterized by a T-shaped opening through the first portion in a direction generally parallel to said surfaces and both legs of the T having a width slightly larger than y with the cross leg of the T having a length slightly larger than x so that the interposer may be inserted through both the aperture and the opening with its x dimension parallel to said surfaces and then rotated until it fits entirely within the cross leg of the T-shaped opening with its y dimension parallel to said surface.