Abstract: A thermal conductive roller for use in copying machines, steam-heated and induction-heated applications includes a ceramic heating layer formed by plasma spraying a ceramic material to form an electrically conductive heating layer of preselected and and controlled resistance. Several methods of controlling the resistance of the ceramic heating layer are disclosed. The ceramic heating layer is sealed with a solid, low viscosity sealer such as Carnauba wax to protect the ceramic layer from moisture penetration. Electrical current is applied at or near the core and is conducted radially outward through the heating layer to an outer grounded metallic layer. An outer contact layer of metal, ceramic, or polymeric material can be added.

Abstract: An electrostatic assist roller (30) for use in a coating, printing or copying machine includes a cylindrical roller core (35), and a ceramic layer (38) formed by plasma spraying a blend of an insulating ceramic material and a semiconductive ceramic material in a ratio which is selected to control the resistance and thickness of the ceramic layer in response to an applied voltage differential. The semiconductive ceramic layer (38) is sealed with a solid, low viscosity sealer (39), such as Carnauba wax, to protect the ceramic layer (38) from moisture penetration. A second ceramic layer (37) may be used to insulate the semiconductive ceramic layer (38) from the core (35).

Abstract: A charging roller for use in a xerographic copying machine includes a cylindrical roller core, and a ceramic layer formed by plasma spraying a blend of an insulating ceramic material and a semiconductive ceramic material in a ratio which is selected to control an RC circuit time constant of the ceramic layer in response to an applied voltage differential. The ceramic layer is sealed with a solid, low viscosity sealer, such as Carnauba wax, to protect the ceramic layer from moisture penetration.

Abstract: A thermal conductive roller for use in copying machines, steam-heated and induction-heated applications includes a ceramic heating layer formed by plasma spraying a ceramic material. Conductive bands are provided for supplying electrical current to portions of the ceramic heating layer. In one embodiment, heat is generated by passing current through a length of the roller between two narrow bands. In a second embodiment, heat is generated by directing current radially from the core of the roller to an outer ground layer through wide bands corresponding to heating zones for the roller. In a third embodiment, the ceramic layer is inside the steel core.

Abstract: A thermal conduction roller for use in industrial and office equipment includes a ceramic heater layer and a second ceramic layer disposed in between the ceramic heater layer and the core. The second ceramic layer has a resistance characteristic such that resistance of the roller decreases with heating to approximately the same order of magnitude as resistance in the longitudinal direction. This causes electrical current to be diverted from the ceramic heater layer to limit the temperature in that layer and any outer layer contacting a work object. The resistance of the second ceramic layer is controlled in part by controlling the parameters of plasma spraying process, including hydrogen secondary gas flow.

Abstract: An impression roller for an electostatic printing assist system consists of a metal roller core, a relatively thick insulating layer of substantially uniform thickness covering the main body of the core, a relatively thin intermediate conductive layer covering the insulating layer and a relatively thick semiconductive layer covering the intermediate layer. The relatively thin conductive layer is exposed at one end of the roller so it can make contact with a rotary transformer. In a first embodiment of the invention the roller core is tapered at one end and the slope of the tapered end built up with semiconductive material. In a second embodiment there is an annular groove which is cut into the conductive layer to provide improved contact with a transformer. A method of preparing rollers is also disclosed.

Abstract: An impression roller for electrostatically assisted printing distributes a charge across a web of packaging material. The roller has considerably more resistance in the longitudinal direction than in the circumferential direction to restrict the distribution of charge to portions of the roller extending beyond the web. The lower resistance in the circumferential direction is provided by a set of looped conductors--either conductive rubberized strips or wire loops--which are embedded in an outer layer of semiconductive material of the roller to allow electrical current traveling in the circumferential direction to bypass portions of the semiconductive material. The electrical current encounters considerably more resistance in the longitudinal direction, because the conductors are spaced longitudinally along the rollers at intervals and any current traveling from one looped conductor to another travels through the semiconductive material.

Abstract: Several embodiments of a voltage applicator device are disclosed for contacting an impression roller in an electrostatically assisted (ESA) printing machine. The voltage applicator device has rolling conductive surfaces which are spaced apart and selectively connected to a voltage source to limit voltage application to the width of one or more partial webs being run through the machine. In the various embodiments, the conductive surfaces outside the web area can be left unconnected, but are preferably grounded or connected to a voltage of opposite polarity, to drain current from portions of the impression roller lying beyond the web. The rolling conductive surfaces can be formed as individual rollers or preferably as a segmented voltage application roller carrying electrical circuitry to connect the conductive surfaces to the voltage source through a roller journal shaft.

Abstract: An impression roller with an insulated core, with an outer layer of resilient semiconductive material, and with a set of conductive wires extending along its length and out one end for interconnection, to adjust the resistance of the roller to current being conducted between a first region of higher potential and a second region of relatively lower potential. In a first embodiment the wires are connected by jumper wires while in a second embodiment resistors are connected between the conductive elements to provide further increments in the adjustment of roller resistance. A method is also disclosed for making such a roller.