Importance

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Abstract

A thermal conductive roller (10, 80) for use in copying machines, steam-heated and induction-heated applications includes a ceramic heating layer (14, 84) formed by plasma-spraying a ceramic material to form an electrically conductive heating layer. In a first embodiment, power is supplied through connections on opposite ends of the ceramic heating layer (14). Ceramic insulating layers (12, 13) are used between the core (11) and heating layer (14), and between the heating layer (14) and the conductive layer (17). A conductive layer (17) is disposed over and around the ceramic heating layer (14) and the insulating layers (12, 13) to counteract the capacitive effects of the insulating layers (12, 13). Circuitry (38, 39) for detecting faults in the ceramic insulating layers (12, 13) is connected across lines (32, 33) supplying power to the roller, as well as to a conductive portion of the core (11) and to the conductive layer (17). In a second embodiment, current is conducted radially outward through the heating layer (84) to an outer grounded metallic layer (85). In both embodiments an outer functional layer (18, 86) of ceramic, or polymeric material can be added over the conductive layer (17), or the conductive layer (17) can form the outer layer.

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First Claim