Method and device for controlling a thermal printing head
AssigneeSociete d'Applications Generales d'Electricite
InventorsMaurice Lacord, Christian Lavergne, Patrick Vegeais
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Abstract
A thermal series type printing head is controlled on-the-fly, during a succession of cycles of a duration at most equal to the time for printing the points, so as to be heated independently during the first half and during the second half of each cycle. Thus an offset dot can be printed of half a length of a a normal dot, or an extended dot, one and half times as long as the normal dot, for improving the definition of printing without reducing the writing speed. The invention applies to printing systems, particularly for printers connected to word processing devices.
Claims8
A method of controlling a series-type thermal writing head for a printing system, the head having at least one transfer strip of heating elements for printing dots on a recording medium, said method comprising:
- (a) driving said head longitudinally along a line at a given speed;
- (b) subjecting each of the heating elements to a succession of thermal cycles, each of said cycles having a time duration less than or equal to a time required for the heating element to print a dot on the recording medium;
- (c) during a first half cycle of each of said cycles subjecting each of the heating elements respectively to one of a non-zero and a zero initial heating time in accordance with whether a dot is to be printed or not printed by the respective heating element during said first half cycle;
- (d) during a second half cycle of at least one of said cycles subjecting at least one of the heating elements subjected to a non-zero initial heating time during said first half cycle to a second non-zero heating time to print an extended dot;
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- (e) during a second half cycle of at least one of said cycles subjecting at least one of the heating elements subjected to a zero initial heating time during said first half cycle to a second non-zero heating time to print an offset dot.
A device for controlling a series-type thermal printing head for a printing system having at least one transfer strip of heating elements for printing dots on a recording medium, said device comprising:
- (a) driving means for driving said head longitudinally at a given speed;
- (b) heating means for heating said heating elements;
- and
- (c) computer-controller means for calculating heating times for each of the heating elements and controlling said heating times to subject the heating elements to a succession of thermal cycles, each cycle having a time duration less than or equal to a time required for the heating elements to print a dot on the recording medium, wherein (i) during a first half cycle of each of said cycles, each of the heating elements is subjected respectively to one of a non-zero and a zero initial heating time in accordance with whether a dot is to be printed or not printed by the respective heating element during said first half cycle of the thermal cycle, (ii) during a second half cycle of at least one of said cycles, at least one of the heating elements subjected to a non-zero initial heating time during said first half cycle is subjected to a second non-zero heating time to print an extended dot, and (iii) during a second half cycle of at least one of said cycles, at least one of the heating elements subjected to a zero initial heating time during said first half cycle is subjected to a second non-zero heating time to print an offset dot.
Dependencies are inferred from the claim text.