Thermal printhead temperature control
First Claim
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1. A thermal printer, comprising:
- a thermal printhead configured for direct thermal printing;
a print-medium subsystem comprising;
a spool for holding a heat sensitive print medium; and
a movement mechanism for moving the print medium along a print-medium path so that the print medium may be heated by the thermal printhead above a thermal threshold to form marks;
a housing encompassing the thermal printhead and the print-medium subsystem;
a first sensor mounted to the thermal printhead for sensing a printhead temperature;
a second sensor positioned within the housing proximate to the spool and apart from the thermal printhead for sensing an environment temperature, the environmental temperature being approximately the temperature of the print medium; and
a processor contained in the housing and communicatively coupled to the thermal printhead, the first sensor, and the second sensor, wherein the processor is configured by software to;
compare the environment temperature and the printhead temperature by calculating a temperature gap that is a difference between the environment temperature and the printhead temperature,compute a temperature value based on the temperature gap, the temperature value computed by adding or subtracting a compensation value to the printhead temperature, andcontrol the heating of the thermal printhead using the temperature value.
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Abstract
Control of the print temperature for a thermal printer is disclosed. Two temperature sensors are used to sense the temperature of both the thermal printhead and the environment around the print medium. In this way, the energy applied to the thermal printhead'"'"'s heating elements may be adjusted to match an ideal print temperature, which depends on both the printhead temperature and the print-medium temperature.
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Citations
17 Claims
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1. A thermal printer, comprising:
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a thermal printhead configured for direct thermal printing; a print-medium subsystem comprising; a spool for holding a heat sensitive print medium; and a movement mechanism for moving the print medium along a print-medium path so that the print medium may be heated by the thermal printhead above a thermal threshold to form marks; a housing encompassing the thermal printhead and the print-medium subsystem; a first sensor mounted to the thermal printhead for sensing a printhead temperature; a second sensor positioned within the housing proximate to the spool and apart from the thermal printhead for sensing an environment temperature, the environmental temperature being approximately the temperature of the print medium; and a processor contained in the housing and communicatively coupled to the thermal printhead, the first sensor, and the second sensor, wherein the processor is configured by software to; compare the environment temperature and the printhead temperature by calculating a temperature gap that is a difference between the environment temperature and the printhead temperature, compute a temperature value based on the temperature gap, the temperature value computed by adding or subtracting a compensation value to the printhead temperature, and control the heating of the thermal printhead using the temperature value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A control system for a thermal printer, comprising:
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a first sensor to measure a printhead temperature, wherein the printhead is a thermal printhead of the printer that is configured for direct thermal printing; a second sensor, positioned proximate to a spool of the thermal printer for holding a heat sensitive print medium, to measure an environment temperature, the environmental temperature being approximately the temperature of the print medium; and a processor communicatively coupled to the first sensor and the second sensor that is configured by software to; compare the environment temperature and the printhead temperature by calculating a temperature gap that is a difference between the environment temperature and the printhead temperature, compute a temperature value based on the temperature gap, the temperature value computed by adding or subtracting a compensation value to the printhead temperature, and adjust the energy applied to the thermal printer'"'"'s printhead using the temperature value. - View Dependent Claims (12, 13, 14, 15)
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16. A method, comprising:
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providing a thermal printer comprising (i) a thermal printhead to heat thermal paper, (ii) a printhead thermistor to measure a printhead temperature corresponding to the temperature of the printhead, and (iii) an environment thermistor to measure an environment temperature corresponding to the temperature of the thermal paper; measuring, with a first sensor, a printhead temperature; measuring, with a second sensor, an environment temperature; comparing, with a processor communicatively connected to the first sensor and the second sensor, the printhead temperature to the environment temperature by calculating a temperature gap that is a difference between the environment temperature and the printhead temperature; compute a temperature value based on the temperature gap, the temperature value computed by adding or subtracting a compensation value to the printhead temperature; and heating a thermal printhead communicatively connected to the processor based on the temperature value. - View Dependent Claims (17)
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Specification