Incremental printing of symbolic information – Thermal marking apparatus or processes – Having driving circuitry for recording means
Reexamination Certificate
1999-11-08
2001-02-13
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Having driving circuitry for recording means
C347S171000
Reexamination Certificate
active
06188423
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
TECHNICAL FIELD
The present invention is directed to a thermal printer for printing tags and/or labels and more particularly to such a printer and method for predicting thermal printhead failure.
BACKGROUND OF THE INVENTION
Known thermal label/tag printers include thermal printheads containing individual printing elements. When a printing element fails, it may result in a discontinuity in the printing. Prior thermal label printers have used data dot shift routines to shift data around a failed printing element so that the failed printing element is aligned with “zero” print data. This feature extends the useful life of a thermal printhead. However, such routines do not provide any warning as to when a printing element is failing.
BRIEF SUMMARY OF THE INVENTION
The early thermal printhead failure prediction system of the present invention is directed to overcome the limitations of the prior data dot shift routines described above. The early thermal printhead failure prediction system of the present invention monitors the resistive trends of the individual printing elements of a thermal printhead to provide a warning indication when the resistive trends deviate beyond predetermined limits.
More particularly, in accordance with the present invention, a microprocessor monitors the resistive trends of the printing elements of the thermal printhead. A read/write memory is used to store previously determined resistive values of the individual printing elements sampled over time for use in determining the resistive trend. Specifically, the microprocessor compares a current resistance value determined for a particular printing element to one or more previously determined resistance values for that particular printing element including the resistance value determined immediately preceding the current value to determine the trend in the resistance for that printing element. The microprocessor compares one or more characteristics of the resistive trend to predict whether an individual printing element is failing. If the microprocessor determines that an individual printing element may be failing, a warning to that effect is generated.
When the microprocessor of a thermal label/tag printer executes such a printhead failure prediction routine, maintenance may be scheduled before the thermal printhead fails and/or data dot shift routines become ineffective.
These and other advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
REFERENCES:
patent: 4595935 (1986-06-01), Brooks et al.
patent: 4769657 (1988-09-01), Takahashi
patent: 4774526 (1988-09-01), Ito
patent: 4996487 (1991-02-01), McSparran et al.
McAndrews Held & Malloy Ltd.
Monarch Marking Systems, Inc.
Tran Huan
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