Incremental printing of symbolic information – Thermal marking apparatus or processes – Density control
Reexamination Certificate
2001-05-29
2003-08-12
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Density control
Reexamination Certificate
active
06606108
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled Circuit And Apparatus For Driving Thermal Print Head Quickly earlier filed in the Korean Industrial Property Office on Aug. 17, 2000, and there duly assigned Serial No. 2000-47587 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving apparatus for a thermal print head (TPH), and a method of driving a thermal print head.
2. Description of Related Art
A thermal printer is an apparatus which prints text and/or graphic images on a thermal paper using heat produced by heat-generating elements. The thermal printer has been widely used in industrial fields such as a facsimile, a point-of-sale (POS) system, an electronic cash register (ECR), a bar code printer, an automatic teller machine (ATM), an automatic ticket vending machine, and the like.
I have determined that during low-speed printing, accumulated heat of the thermal cells in the thermal printer head does not affect a printing quality, since there is a sufficient time to radiate heat until the next line is printed. However, during high-speed printing, heat of the thermal cells is not satisfactorily radiated when a the next line is printed, resulting in a poor quality print. That is, a printing may be blurred, thereby lowering a printing quality.
The thermal printer cannot control, individually, an on-time of the respective thermal cells of the thermal printer head, and in case of a great number of the thermal cells, their resistance values become higher, thereby shortening their life span. That is, since the thermal printer is operated in the state that heat is accumulated in the thermal cells as described above, the thermal cells may be easily worn due to accumulated heat. Also, output errors may occur, leading to a bad print quality.
For the foregoing reasons, there is a need for an apparatus and a method of driving a thermal printer head of a thermal printer having a long life span and a high printing quality.
Examples of some improved thermal printers for preventing the accumulation of heat in the thermal print head are described in the following patents incorporated by reference herein: U.S. Pat. No. 4,688,051 to Toshio Kawakami et al. entitled Thermal Print Head Driving System; U.S. Pat. No. 5,327,165 to J. W. Elliott entitled Electronic Printing System For Imaging Thermally Sensitive Paper; U.S. Pat. No. 5,677,721 to Minoru Suzuki et al. entitled Thermal Print Head Driving System; U.S. Pat. No. 5,793,403 to Gary M. Klinefelter entitled Thermal Print Head Compensation; U.S. Pat. No. 5,825,985 to Tomotsu Asai et al. entitled Thermal Printer And Thermal Printer Head Driving System; and U.S. Pat. No. 6,034,705 to Charles V. Tolle et al. entitled Thermal Printer Control System.
SUMMARY OF THE INVENTION
To overcome the problems described above, a preferred object of the present invention is to provide an apparatus and a method of driving a thermal printer head of a thermal printer having a long life span and a high printing quality.
Another object of the present invention is to provide a high-speed driving apparatus and method for a thermal printer head using a print history to prevent an accumulation of too much heat in the thermal cells of the print head to ensure that a thermal printer has a long life span and a high printing quality.
A further object of the present invention is to provide a high-speed driving apparatus and method for a thermal printer head using a print history to individually control each thermal cell of the thermal printer head to thereby prevent an accumulation of too much heat in the thermal cells of the print head to ensure that a thermal printer has a long life span and a high printing quality.
In order to achieve the above objects, the preferred embodiment of the present invention provides a thermal printer head high-speed driving apparatus positioned between a microcomputer and a thermal printer head for controlling the on-time of each thermal cell in the thermal printer head. The apparatus stores driving history information of thermal cells in the thermal printer head corresponding to a previous line and a line before last, the driving information of the current cell of a present line to be printed and driving information of adjacent thermal cells preceding and following of the current cell. Using the stored information the high-speed driving apparatus derives drive time data for controlling an on-time of the current cell, thereby individually controlling each thermal cell of the thermal print head.
The apparatus includes a first register portion for storing the driving history information of the thermal cells corresponding a previous line already printed, the driving history information of the thermal cells corresponding a line before last already printed, the driving information of a thermal cell to be printed and the driving information of the two thermal cells immediately adjacent to and on the same line as the thermal cell to be printed, the driving information of a thermal cell to be printed and the adjacent thermal cells being serially applied from the microcomputer; a printing data generating portion for combining the driving history information of the thermal cell of the previous line already printed corresponding to the thermal cell to be printed, the driving history information of the thermal cell of the line before last already printed corresponding to the thermal cell to be printed, the driving information of the thermal cell to be printed and the driving information of the two adjacent thermal to output the driving time information of the corresponding thermal cell at a unit time; a second register portion for renewing the driving history information of the first register portion using the driving time information output from the printing data generating portion; a third register portion for storing the driving time information output from the printing data generating portion and combining the driving time information to generate printing data for driving the thermal cell to be printed; and a latch/time controller for producing and outputting an output enable signal to the third register portion to enable the third register portion to output the stored driving time information to be combined as the printing data and for producing a latch signal, a strobe signal and a clock signal, which are applied to the thermal printer head.
The preferred embodiment of the present invention further provides a method of individually controlling the on-time of each thermal cell of a thermal printer head driven at high speed, the method logically combines, for each thermal cell to be printed, driving history information of the thermal cell corresponding to a previously printed line, driving history information of the thermal cell corresponding to a line before last previously printed, driving information of the thermal cell of a present line to be printed and driving information of the two thermal cells immediately adjacent to and in the same line as the thermal cell to be printed to generate driving time information; stores the driving time information; generates output enable signals for controlling when the driving time information is read from storage; combines the driving time information read from storage to produce printing data for driving the thermal cell of the thermal print head to be printed, wherein the on-time of the thermal cell driven by the print data is variable according to values of the driving time information.
REFERENCES:
patent: 4688051 (1987-08-01), Kawakami et al.
patent: 5327165 (1994-07-01), Elliott
patent: 5677721 (1997-10-01), Suzuki et al.
patent: 5793403 (1998-08-01), Klinefelter
patent: 5825985 (1998-10-01), Asai et al.
patent: 5934811 (1999-08-01), Miyaji
patent: 6008831 (1999-12-01), Nakanishi et al.
patent: 6034705 (2000-03-01), Tolle et al.
patent: 6234695 (2001-05-01), Freedman et al.
patent: 6404452 (2002-06-01), Spano
Robert E. Bushnell, Esq.
Samsung Electronics Co,. Ltd.
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