Typewriting machines – Typing by other than type-face or type-die – Character formation by impact
Patent
1991-06-27
1992-12-01
Crowder, Clifford D.
Typewriting machines
Typing by other than type-face or type-die
Character formation by impact
4001571, B41J 2295
Patent
active
051674580
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a wire driving mechanism for driving the print wires of a wire-dot print head and, more particularly, to a wire driving mechanism employing piezoelectric elements or magnetostrictive elements as driving means.
BACKGROUND ART
A known wire-dot print head employs piezoelectric elements capable of converting electric oscillations into mechanical oscillations or magnetostrictive elements capable of being strained by a magnetic field as driving means. Since the piezoelectric action of piezoelectric elements and the magnetostrictive action of magnetostrictive elements are exactly dependent on high-frequency driving pulse signals, the employment of piezoelectric elements or magnetostrictive elements as driving means for a print head enables high-speed printing.
Although piezoelectric elements and magnetostrictive elements have the foregoing advantages, the mechanical strain of those elements, in general, is a very small value in the range of 7 .mu.m to 15 .mu.m, whereas the required stroke of the print wires of a print head is on the order of 0.3 mm at the minimum, and the stroke must be on the order of 0.5 mm to print on various kinds of recording media with a satisfactorily high print quality.
Print heads employing piezoelectric elements or magnetostrictive elements as driving means, such as those disclosed in Japanese Patent Laid-open (Kokai) No. 59-26273 and Japanese Utility Model Laid-open (Kokai) No. 63-198541, multiply the mechanical oscillations of the elements mechanically and transmit the multiplied mechanical oscillations to the print wires.
The known print heads proposed in Japanese Patent Laid-open (Kokai) No. 59-26273 and Japanese Utility Model Laid-open (Kokai) No. 63-198541 need a complicated mechanism, which requires much time and labor for manufacture, for mechanically multiplying dimensional variations of the elements and for transmitting the multiplied dimensional variations to the print wires. Accordingly, these known print heads have a high manufacturing cost and are difficult to manufacture by a mass-production process. The mechanical amplifying mechanism of the print head disclosed in Japanese Utility Model Laid-open No. 63-198541 has a displacement transmission system, including sliding components, which are abraded and thereby reduce the life of the print head.
Techniques for multiplying the oscillation of elements by a simple mechanism are disclosed in the following references.
A method disclosed in Japanese Patent Publication (Kokoku) No. 60-54191 em ploys a plurality of magnetostrictive elements and adds up the respective dimensional variations of the elements. A method disclosed in Japanese Patent Laid-open (Kokai) No. 63-144055 employs a horn for multiplying the oscillations of the elements.
These techniques disclosed in the foregoing two references, however, are capable of multiplying the oscillations of the elements only several times, and the multiplication ratios of these techniques are not large enough for printing with a satisfactorily high print quality.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to solve the foregoing problems in the conventional print heads and to provide a simple wire driving mechanism for a print head, capable of multiplying the dimensional oscillations of piezoelectric elements or magnetostrictive elements at, a multiplication ratio large enough for printing with a satisfactorily high print quality.
It is another object of the present invention to provide a print head incorporating a sufficiently durable wire driving mechanism having high reliablility.
The present invention employs two parallel levers each having one fixed end, and turns the levers by the expansive force of extendable driving means. The extension of the extendable driving means is multiplied by the levers and the displacement of the free ends of the levers corresponds to a multiple of the extension of the extendable driving means. The respective opposite displacements of the free ends of the levers
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Patent Abstracts of Japan (1-275,150), 45 M 926.
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"Magnetostrictive Actuator", IBM Technical Disclosure Bulletin, vol. 29, No. 6 (Nov. 1986) pp. 2603-2604.
IBM Technical Disclosure Bulletin, vol. 20, No. 6, Nov. 1977.
Andou Hirokazu
Kamimura Katsuya
Kikuchi Hiroshi
Koyama Tatsuya
Shimomura Tatsuhiko
Crowder Clifford D.
Funk Stephen R.
OKI Electric Industry Co., Ltd.
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