Typewriting machines – Typing by other than type-face or type-die – Character formation by impact
Patent
1991-03-21
1993-04-06
Wiecking, David A.
Typewriting machines
Typing by other than type-face or type-die
Character formation by impact
395108, 395110, 340790, B41J 2485
Patent
active
051998033
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of compressing a dot-matrix character and a method of expanding a compressed character, which are suitable for storing several dot-matrix characters in a character generator.
DESCRIPTION OF THE PRIOR ART
Heretofore, printers have been provided which exhibit a character with several dots (for example, 24 dots in a vertical direction and 24 dots in the horizontal direction). Printer of this kind are called as "dot-printer", and among them, wire dot printers which use wires for printing dots are famous. In general, a printer of this kind incorporates a character generator for storing data therein which determines whether or not a dot is printed (which will be hereinbelow abbreviated as "dot data"), and reads dot data to be printed from this character generator when a character is to be printed; thus, the character can be printed. For example, in the case of a wire-dot printer in which 24 wires are arranged in the vertical direction, one character is printed by reading dots in a vertical row (24 dots) from the character generator several times.
Recently, it has been necessary for printers to print several kinds of characters. Accordingly, a method of storing several characters in the character generator was invented. This invention is disclosed in Japanese Laid-Open Patent Publication No. 60-257253 or U.S. Pat. No. 4,704,040. This invention concerns a character compression method in which the configuration of dots (which is hereinbelow simply denoted as a "dot-pattern") is checked for each column, and in the case of plural repetitions of the same pattern, data corresponding to the dot-pattern in one column and data indicating the number of repetitions thereof are stored in the character generator in order to reduce the volume of data for one character. However, there are characters which cannot be compressed by this method. One of such characters is shown in FIG. 1. As understood from this figure, in one and the same row, no dots are successively present in each two adjacent columns. That is, no dots are successive in the lateral direction. Accordingly, the dot-patterns in each two adjacent columns are always different from each other so that the same patterns are not present in succession. This character has been devised in order to improve the printing quality by a printer and to increase the printing speed. Accordingly, the number of dots in the lateral direction is greater than that of a normally printed character. In the character "M" shown in this figure, the number of dots in the lateral direction is 30. Furthermore, as mentioned above, no dots are successive in the lateral direction. An explanation is provided hereinbelow as to the reason for this.
In the case of a wire-dot printer, when a wire is driven, the wire projects from its initial position so as to print a dot on printing paper at a predetermined position, and then it returns to its initial position. In the case of successively driving the same wire, it is driven after having returned to its initial position. By the way, the configuration of the dot pattern in a normal character is not previously known. Dots are sometimes present successively in the lateral direction. Accordingly, the printing control is arranged so that when a dot is printed by a certain wire, another wire cannot be driven until the certain wire has been returned to its initial position. However, with this control method, wires cannot be efficiently driven so that the printing speed cannot be increased. This is because of the presence of wires which can be driven even though the printer has not returned to its initial position. They are wires which are not driven when dots in the column just before the present column are printed. Accordingly, if the dot-pattern of a character has such a configuration that dots are not successive in the lateral direction, the wires can be effectively driven so as to increase the printing speed. This is the reason for the abovementioned matter.
SUMMARY OF THE INVENTION
REFERENCES:
patent: 4632579 (1986-12-01), Takano et al.
patent: 4704040 (1987-11-01), Takano et al.
patent: 4942390 (1990-07-01), Do et al.
"Compression/Decompression of Font Patterns"; Anon.; IBM TDB ; vol. 28, No. 8, pp. 3563-4, Jan. 1986.
Itoh Toshikazu
Shimizu Tadao
OKI Electric Industry Co., Ltd.
Wiecking David A.
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