Recorders – Thermal recording
Patent
1990-10-11
1991-12-17
Fuller, Benjamin R.
Recorders
Thermal recording
400 74, G01D 1510
Patent
active
050737864
ABSTRACT:
A detection circuit for determining whether heating members within a thermal head are broken is disclosed. The circuit comprises a voltage source connected in series with a resistor, wherein the voltage source and resistor are connected in parallel with a diode. The diode allows current to flow from a thermal head driving power supply to a thermal head. invention also includes a comparator for comparing the voltage The present level at the output terminal of the diode with a reference voltage. The parallel connection of the diode and the voltage source/resistor allows the output voltage of the diode to maintain an expected voltage level while the heating members are operating normally (i.e. the members are not broken). The parallel connection also allows the voltage level at the output terminal of the diode to increase as the members operate abnormally (i.e. a worn or broken condition). The comparator monitors this voltage level, and detects undesirable fluctuations therein. Thus the circuit of the present invention prevents printing of incorrect letters.
REFERENCES:
patent: 4774526 (1988-09-01), Ito
Shimada Fumihiro
Uemura Hisashi
Fuller Benjamin R.
Kanzaki Paper Mfg. Co. Ltd.
Le Nancy
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