Contemporary xerographic or electrophotographic printers and copiers include a device to fuse or permanently bond loose toner transferred from a photoconductor carrier to a cut sheet media such as paper. The more common fuser structures employed for this purpose include the heated roller type and the flash fuser type. In the former, the toner is melted onto the media substrate by heated rollers that press against the media sheets whereas the latter is energized to cause fusing by intense heat and light impinging upon a relatively wide area for a very brief period of time.
In commonly-assigned U.S. Pat. No. 4,386,840 by Garthwaite and Suarez, multiple flash fuser heads are sequentially actuated from a common power supply to effect fusing on different portions of the copy media. This permits minimization of the power supply size. It is also known to employ a plurality of fuser lamps and to actuate them in sequence as in Japanese Patent JA 55-131285, or to stagger the heads but fire them all at the same time as in Japanese Patent JA 61-200566. Yet another configuration is shown in U.S. Pat. No. 4,434,353 by Marsh wherein selected flash heads are energized as a function of the length of the copy sheet under consideration. These fuser lamps may actually perform drying functions when liquid developer is in use as in U.K. Patent 2,159,462.
Machines for duplex copying or printing are configured in several arrangements. For instance, a separate storage tray is sometimes used with the copy sheet returned to the original transfer station as in U.S. Pat. No. 4,067,649 by Hubbard, LeClere and Underhill. A reversing drum and flipper structure is employed in U.S. Pat. No. 4,272,181 by Treseder.
A single flash fuser with a return path to a duplex reversing roller so that the first side is completely handled before the copy sheet is returned over a reversing roller to the image station for second side image processing is shown in the IBM TECHNICAL DISCLOSURE BULLETIN of June 1981 at pages 810-811. Copy sheet return paths for reversing the copy sheet and returning it to the imaging station after hot roll fusing are shown in U.S. Pat. Nos. 4,488,801 by Gibson and 4,496,142 by Iwasaki. U.S. Pat. No. 4,541,705 by Knechtel is somewhat similar except it includes an intermediate set of fuser rollers in the return path.