Electromagnetic drive for print hammers

Claim 1

A print hammer actuator comprising: a frame means; a print hammer movably mounted on said frame means; an armature means pivotally mounted on said frame means and movable between a ready position and an operative position where it engages said print hammer causing it to print, an including first and second legs and a central portion having an arcuate perimeter; spring means for urging said armature means towards said operative position; magnet means having a first leg portion, a second leg portion, and a central leg portion having a permanent magnet thereon; said magnet having an arcuately shaped recess complementary to said arcuate perimeter on said central portion of said armature means; said central portion and first leg of said armature means cooperating with said first leg portion and central leg portion of said magnet means to produce a first magnetic flux path for holding said armature means in said ready position against the bias of said spring means; said central portion and second leg of said armature means cooperating with said second leg portion and central leg portion of said magnet means to produce a second magnetic flux path whicH assists said spring means in rotating said armature means to said operative position; coil means mounted on the first leg of the armature means for momentarily reducing the flux density in said first flux path enabling the armature means to be rotated to said operative position by said spring means, the rotation of said armature means from said ready position towards said operative position being effective to switch the flux path of said magnet means from said first flux path to said second flux path; said first leg of said armature means striking said print hammer when said armature means is rotated to said operative position; and mechanical means for rotating said armature means back to said ready position from said operative position against the bias of said spring means.