Typewriting machines – Annular typewriter
Patent
1987-05-29
1989-05-09
Wright, Jr., Ernest T.
Typewriting machines
Annular typewriter
307318, 400121, 101DIG13, 101DIG37, B41J 318
Patent
active
048284076
ABSTRACT:
A plurality of switched voltage sources (10, 10', 10") apply charge to a sheet of paper (16) by way of respective sets of styli (12, 12', 12"). To print a dot when toner is subsequently applied to the paper, the voltage source (10) deposits charge on the paper (16) by applying a high voltage, and its voltage returns to ground when it is to avoid leaving a mark. In order to avoid the image degradation that results from the proximity of an unenergized stylus to an energized one, a zener diode (14) is interposed between the switched voltage source (10) and its respective styli (12). By virtue of stray capacitance (C.sub.s) between the styli (12) and ground, the potential of the styli does not return completely to ground when their respective voltage source is switched off. Instead, it returns only to the zener voltage, and this reduces the image degradation that the presence that the unenergized styli would otherwise cause.
REFERENCES:
patent: 3631509 (1971-12-01), Marshall
patent: 3732573 (1973-05-01), Merka et al.
patent: 3792495 (1974-02-01), Bliss et al.
patent: 3875892 (1975-04-01), Gregg et al.
patent: 4115763 (1978-09-01), Brown, Jr. et al.
patent: 4141018 (1979-02-01), Mizuguchi et al.
Sanders Associates Inc.
Wright, Jr. Ernest T.
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