Wear-indicating resistors for thermal printhead
First Claim
1. A thermal printhead comprising:
- a substrate;
a plurality of heating elements disposed on the substrate, the heating elements adapted to cause thermochromic media to selectively darken in accordance with selective activation of the heating elements as the thermochromic media moves in relation to the thermal printhead, to print a desired image on the thermochromic media;
a nonconductive coating over the substrate to protect the heating elements and with which the thermochromic media comes into contact during printing of the desired image on the thermochromic media, the nonconductive coating to wear away with usage of the thermal printhead; and
,one or more resistors at least partially disposed within the nonconductive coating to indicate wear of the thermal printhead, the resistors having electrical resistances that increase as the resistors are worn away in accordance with wearing away of the nonconductive coating.
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Accused Products
Abstract
A thermal printhead includes a substrate, a nonconductive coating over the substrate, a number of heating elements disposed on the substrate, and one or more resistors at least partially disposed within the nonconductive coating. The heating elements cause thermochromic media to selectively darken in accordance with selective activation of the heating elements as the media moves in relation to the thermal printhead, to print a desired image on the media. The nonconductive coating protects the heating elements and wears away with usage of the printhead. The media comes into contact with the nonconductive coating during printing of the desired image on the media. The resistors indicate wear of the thermal printhead, and have electrical resistances that increase as the resistors are worn away in accordance with wearing away of the nonconductive coating.
17 Citations
19 Claims
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1. A thermal printhead comprising:
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a substrate; a plurality of heating elements disposed on the substrate, the heating elements adapted to cause thermochromic media to selectively darken in accordance with selective activation of the heating elements as the thermochromic media moves in relation to the thermal printhead, to print a desired image on the thermochromic media; a nonconductive coating over the substrate to protect the heating elements and with which the thermochromic media comes into contact during printing of the desired image on the thermochromic media, the nonconductive coating to wear away with usage of the thermal printhead; and
,one or more resistors at least partially disposed within the nonconductive coating to indicate wear of the thermal printhead, the resistors having electrical resistances that increase as the resistors are worn away in accordance with wearing away of the nonconductive coating. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method comprising:
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forming a plurality of heating elements on a substrate of a thermal printhead, the heating elements adapted to cause thermochromic media to selectively darken in accordance with selective activation of the heating elements as the thermochromic media moves in relation to the thermal printhead, to print a desired image on the thermochromic media; and
,forming one or more resistors at least partially within a nonconductive coating over the substrate of the thermal printhead, the resistors to indicate wear of the thermal printhead and having electrical resistances that increase as the resistors are worn away in accordance with wearing away of the nonconductive coating, wherein the nonconductive coating is to protect the heating elements, the thermochromic media to come into contact with the nonconductive coating during printing of the desired image on the thermochromic media, the nonconductive coating to wear away with usage of the thermal printhead. - View Dependent Claims (10, 11)
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12. A method comprising:
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using a thermal printhead of a thermal printing device to print a desired image on thermochromic media, the thermal printhead comprising; a substrate; a plurality of heating elements disposed on the substrate, the heating elements adapted to cause the thermochromic media to selectively darken in accordance with selective activation of the heating elements as the thermochromic media moves in relation to the thermal printhead, to print the desired image on the thermochromic media; a nonconductive coating over the substrate to protect the heating elements and with which the thermochromic media comes into contact during printing of the desired image on the thermochromic media, the nonconductive coating to wear away with usage of the thermal printhead; and
,one or more resistors at least partially disposed within the nonconductive coating to indicate wear of the thermal printhead, the resistors having electrical resistances that increase as the resistors are worn away in accordance with wearing away of the nonconductive coating; determining whether the wear of the thermal printhead has exceeded a threshold past which the thermal printhead should be replaced within the thermal printing device, based on the electrical resistances of the resistors; and
,in response to determining that the wear of the thermal printhead has exceeded the threshold, alerting a user that the thermal printhead should be replaced within the thermal printing device. - View Dependent Claims (13, 14, 15)
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16. A thermal printing device comprising:
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a thermal printhead that is replaceable within the thermal printing device; a first mechanism to move thermochromic media past the thermal printhead, the thermal printhead comprising; a substrate; a plurality of heating elements disposed within the substrate, the heating elements adapted to cause the thermochromic media to selectively darken in accordance with selective activation of the heating elements as the thermochromic media moves in relation to the thermal printhead, to print a desired image on the thermochromic media; a nonconductive coating over the substrate to protect the heating elements and with which the thermochromic media comes into contact during printing of the desired image on the thermochromic media, the nonconductive coating to wear away with usage of the thermal printhead; one or more resistors at least partially disposed within the nonconductive coating to indicate wear of the thermal printhead, the resistors having electrical resistances that increase as the resistors are worn away in accordance with wearing away of the nonconductive coating; and
,a second mechanism to determine whether the wear of the thermal printhead has exceeded a threshold past which the thermal printhead should be replaced within the thermal printing device, based on the electrical resistances of the resistors, and to alert the user that the thermal printhead should be replaced upon determining that the wear of the thermal printhead has exceeded the threshold. - View Dependent Claims (17, 18, 19)
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Specification