1. Field of the Invention
This invention generally relates to copiers and printers and, more particularly, to an apparatus for corrugating curled materials, such as paper, used in such copiers and printers.
2. Description of the Related Art
Many materials, such as paper, become curled after bending and/or heating. Paper may, for example, curl after one side of the paper undergoes a printing process. Electrophotographic imaging (i.e., laser printing) typically involves bonding toner to a sheet of paper using heat (typically about 400.degree. F.). This application of heat often results in significant curling (i.e., the tendency of paper to bend in the free state) or "scrolling" (i.e., paper which is folded over onto itself) of the paper. This scrolling can cause paper jams in a laser printer. Scrolling can also cause poor stacking in an exit tray. Although this discussion focuses on paper, it is to be understood that it applies to any media to which a printing process is applied, such as paper, card stock, transparencies, envelopes, labels, etc.
Thus, the challenge is to get the printed media from the printer to span the relatively large distance from the exit rollers to the exit tray without scrolling. The larger the span distance, the higher the exit tray capacity and the greater the reliability of the media stacking. This challenge can be addressed using a corrugation system. A corrugation system is used to stiffen the paper and to prevent scrolling. Corrugation is the forming of the media with ridges and valleys parallel to the direction of travel. While more commonly used to stiffen cardboard, it can also be used to strengthen common sheets of paper. A corrugation system adds furrows and ridges to the paper, and these furrows and ridges increase the strength of the paper. It also tends to counteract curl which typically occurs perpendicular to the direction of the corrugation. This corrugation system is commonly used in laser printers to eliminate the problems associated with scrolling.
Any corrugation system must, however, compensate for a full range of paper weights used in the printer. For example, lightweight, medium weight, and heavy weight papers can be used in a printer. Lightweight paper typically requires much corrugation, whereas heavy weight paper and card stock do not often need corrugation. Further, corrugating heavy paper can result in undesirable creasing and, perhaps, ruining of the heavy weight paper. A corrugation system must, therefore, provide maximum corrugation to lightweight paper which scrolls easily, provide minimum corrugation to heavy weight paper which rarely scrolls, and not result in permanent deformation of any paper (media) type. The corrugation system should be cost effective, and the corrugation system should also be reliable for reduced warranty and service repairs. There is, accordingly, a need in the art for an apparatus that corrugates lightweight paper, yet, compensates for heavy weight paper, and an apparatus which is cost effective and reliable.