Hammer driver controller for impact printers
AssigneeXerox Corporation
InventorsDavid R. Deetz, Roy H. Ogburn
Life of this patent
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Abstract
To obtain a substantially uniform print density while printing at high speed with a hammer-type impact printer, the hammer is electromagnetically driven in response to an energizing current which decays with a predetermined time constant from a high initial level toward a set point level which is automatically adjusted for different classes of characters so that the impact energy imparted to the hammer is regulated as a function of the character being printed. To adaptively absorb the shock forces generated by the rebounding hammer, the energizing current for the electromagnetic driver is reduced to a predetermined fraction of the set point level.
Claims6
In an impact printer having a hammer mounted for movement toward and away from a recording medium to print a selected character on said recording medium on a forward stroke and to rebound away from said recording medium on a rearward stroke, biasing means coupled to said hammer for biasing said hammer rearwardly away from said recording medium, electromagnetic driver means coupled to said hammer for propelling said hammer forwardly against said bias in response to an energizing current having a predetermined set point level to thereby impart impact energy to said hammer, and a controller for applying energizing current to said driver means on command;
- the improvement comprising control means coupled to said controller for reducing said energizing current to and for substantially maintaining said energizing current at a predetermined finite fraction of said set point level during the rearward stroke of said hammer, whereby said driver means smoothly absorbs shock forces generated by the rebounding hammer.
Dependencies are inferred from the claim text.