The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 21, 1981
Filed:
Apr. 02, 1979
Shigeyuki Araki, Tokyo, JP;
Ricoh Company, Ltd., Tokyo, JP;
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.