Printing – Selective or progressive – Bed and platen machines
Patent
1979-04-02
1981-04-21
Coven, Edward M.
Printing
Selective or progressive
Bed and platen machines
4001573, 400166, B41J 792
Patent
active
042625920
ABSTRACT:
A coil (12), when electrically energized, magnetically drives a printing hammer to impact a type element against paper for printing a character. The coil (12) is connected to a power source (+V) for a predetermined time (T1) during which the hammer moves toward the paper and the current (I) through the coil (12) increases exponentially. Then, the coil (12) is energized for another predetermined time (T2) in response to logically high portions of a train of high frequency drive pulses (B). A diode (23) connected in parallel with the coil (12) maintains current flow through the coil (12) due to counter electromotive force during the logically low portions of the drive pulses (B) by providing a low resistance path across the coil (12).
The average value of current through the coil (12) decreases exponentially during the time the drive pulses (B) are applied. The duty cycle of the drive pulses (B) is varied in accordance with the printing area of the character so that the rate at which the current (I) through the coil (12) decreases and thereby the force of impact of the type element against the paper vary accordingly. This enables all characters to printed with the same density regardless of the printing area thereof.
REFERENCES:
patent: 3712212 (1973-01-01), Beery
patent: 3858509 (1975-01-01), Grundherr
patent: 3909681 (1975-09-01), Campari et al.
patent: 4027761 (1977-06-01), Quaif
patent: 4083299 (1978-04-01), Norton
patent: 4118129 (1978-10-01), Grundherr
patent: 4162131 (1979-07-01), Carson et al.
Alexander David G.
Coven Edward M.
Ricoh & Company, Ltd.
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