Abstract:
A method and apparatus for cooling copy sheets in a high speed copy machine while en route to an output tray. The invention utilizes a blower connected to manifolds positioned on opposite sides of copy sheets transported in a paper path en route to the output tray. Airflow is supplied to both sides of copy sheets as they are conveyed throughout the paper path in order to cool the copy sheets before they enter the output tray and thereby prevent fusing of the copy sheets together.

Description:
This invention relates generally to exit tray stacking in printers or copiers, and more particularly concerns a paper cooling system for cooling copy sheets before they enter an exit tray where sheet stacking is performed. 
     BACKGROUND OF THE INVENTION 
     As xerographic copiers and printers of all kinds increase in speed or decrease in paper path length to achieve smaller equipment footprints, heat provided to imaged sheets by fusing methods has significantly less time to dissipate prior to stacking. This results in an excess amount of heat stored in each copy sheet as it is delivered to a stacker or finisher. When these printed sheets are stacked, the combination of excess heat and pressure of the stack weight can fuse the two face to face images together. In the duplex mode, if the stack is left undisturbed, allowing the copy sheets to cool in the stack, the toner on the simplex side of one sheet can stick to the toner on the duplex side of the next sheet, thus fusing the sheets together. Obviously, it is difficult to subsequently separate these sheets, particularly in off-line finishing devices. 
     The following disclosure may be relevant to various aspects of the present invention and may be briefly summarized as follows: 
     U.S. Pat. No. 3,901,591 issued to Sakae Mitsumasu is directed to a mechanism for cooling photosensitive materials in an electrophotographic copying machine that includes a cooling means for blowing a first air stream onto the surface of a photosensitive material and an air directing means for producing a second air stream through a thermal fixing device with the second air stream operating to draw the first air stream into and through the fixing device. A ventilator collects and discharges the air stream produced by the cooling means and the air directing means out of the copying machine after passing through the fixing device. 
     The above reference cited herein is incorporated by reference for its teaching. 
     Accordingly, although known apparatus and processes are suitable for their intended purposes, a need remains for an apparatus that can cool copy sheets before they enter a stacking or output tray. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided an apparatus for transporting copy sheets traveling at high rates of speed through a paper path to a fuser and then to a copy sheet stacking tray, which apparatus includes a system for cooling copy sheets after they exit the fuser and before they enter the copy sheet stacking tray. The apparatus includes a blower connected to two manifolds by way of a ducting system. The manifolds supply airflow over upper and lower surfaces of each copy sheet and thereby cools both copy sheet surfaces before they reach the copy sheet stacking tray. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which: 
     FIG. 1 is an elevation view illustrating the principal mechanical components of a typical printing system that incorporates the copy sheet cooling system of the present invention; 
     FIG. 2 is a schematic isometric view of the copy sheet cooling apparatus in accordance with the present invention and employed in the printing system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     Referring now to the drawings, the various processing stations employed in a typical printing machine are depicted in FIG.  1 . Printer section  8  comprises a laser type printer and for purposes of explanation is separated into a Raster Output Scanner (ROS) section  87 , Print Module Section  95 , Paper Supply section  107 , and Finisher  120 . ROS  87  has a laser, the beam of which is split into two imaging beams  94 . Each beam  94  is modulated in accordance with the content of an image signal input and in this example, by acousto-optic modulator  92 , to provide dual imaging beams  94 . Other arrangements for modulating beams  94  are possible, and the invention is not limited to this embodiment. Beams  94  are scanned across a moving photoreceptor  98  of Print Module  95  by the mirrored facets of a rotating polygon  100  to expose two image lines on photoreceptor  98  with each scan and create the latent electrostatic images represented by the image signal input to modulator  92 . Photoreceptor  98  is uniformly charged by corotrons  102  at a charging station preparatory to exposure by imaging beams  94 . After exposure with beams  94 , the latent electrostatic images are developed by developer  104  and transferred at transfer station  106  to a print media  108  delivered by Paper Supply section  107 . Media  108 , as will appear, may comprise any of a variety of sheet sizes, types, and colors. For transfer, the print media is brought forward in timed registration with the developed image on photoreceptor  98  from either a main paper tray  110  or from auxiliary paper trays  112 , or  114 . The developed image transferred to the print media  108  is permanently fixed or fused by fuser  116  and the resulting prints discharged to either output tray  118 , or to output collating trays in finisher  120 . Finisher  120  includes a stitcher  122  for stitching (stapling) the prints together to form books, a thermal binder  124  for adhesively binding the prints into books and a stacker  125 . 
     Reference is now made to FIG. 2, which shows an isometric view of the copy sheet cooling system  200  of the present invention. The system is configured to supply a large amount of air in a small area and focused directly onto each copy sheet in order to cool each copy sheet without requiring an air conditioning unit or a cooling system that cools the entire machine. The cooling system  200  comprises a blower  210  connected by ducting  215  to a pair of manifolds  220  and  225 . The blower is required to supply the necessary air flow onto copy sheets and is located near the bottom of copier/printer of FIG. 1 in order to draw cooler air than is at the top of the copier/printer. If necessary, the blower can also be used to draw external ambient air to cool the copy sheets even further. Conventional ducting  215  routes the airflow from blower  210  to upper manifold  220  and lower manifold  225 . The ducting cross-sectional area is the same as that of the blower outlet in order to eliminate back pressure and to maximize the air flow that reaches the manifolds. Manifolds  220  and  225  have their exits positioned to apply cool air to copy sheets into a small gap where two separate transports meet. Each manifold is configured to be long enough so that air is blown over a majority of the length of each copy sheet and the entire width of each copy sheet is cooled as each sheet is moved past the manifolds by the copy sheet transport system of the copier/printer. The air is blown at acute angles towards the copy sheets so that in addition to the initial contact from the airflow on the copy sheets, cooler air will follow the copy sheets and provide even further cooling. Both manifolds  220  and  225  are preferred with one on each side of a copy sheet transport path in order to supply air to both sides of a copy sheet conveyed through the transport path and thereby contact as much surface area of each copy sheet as possible, and thus magnify the cooling effect and to assist in preventing jams in the paper paths of the copier/printer. Using only one manifold is contemplated, but complicated since the edge of a copy sheet can be blown out of the paper path causing a jam. If the gap between transports is small enough, using a single manifold on one side of the sheet is feasible. However, it should be tested to assure that the edge of the sheet is not blown out of the transport, and should be used only when there are space limitations whereas both manifolds cannot fit. If one manifold is utilized, it should be positioned on the side of the copy sheet that was just printed, as that side of the sheet contains the most heat. By blowing on each side of the copy sheets, there is assurance that the copy sheets maintain a straight path into the next transport. It should be understood that the outlets of cooling system  200  could be designed into the paper transports, if desired. 
     In recapitulation, the present invention discloses a technique used to cool copy sheets prior to stacking in an output tray. In high speed or short paper transport copier/printing machines, heat provided into each imaged sheet during the fusing process has an inadequate amount of time to dissipate. If the copy sheets are stacked without cooling, they will stick together as the toner cures. A blower and associated ductwork are mounted in a copier/printer such that ambient air is blown, uniformly, across at least one copy sheet surface, sufficiently cooling it before it is stacked. Preferably, air is blown over both sides, thereby giving greater cooling effects. 
     It is, therefore, apparent that there has been provided in accordance with the present invention, a copy sheet cooling system for high speed document reproduction that fully satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.