Abstract:
A tandem printing system includes two printers separated by a dual finisher station centered between the two printers. The system&#39;s two input/output terminals are controlled to act as one high-speed print engine. With this arrangement, improved productivity is realized if one printer is not functional (i.e., 50% instead of 0%). The centrally positioned dual finisher station simplifies the paper path for the second of the dual finishers.

Description:
BACKGROUND  
       [0001]     This disclosure relates in general to copier/printers, and more particularly, to two printers with their outputs linked to a common finisher positioned between them.  
         [0002]     Typically, in an effort to meet demand for high end printers, i.e., 100+ pages per minute (ppm), tandem machine designs place the two machines side by side with the result that the output from the first machine to a finisher or output tray for the machines must route around the second machine with complex paper path hardware. In addition, if one of the machines jams or needs supplies, productivity goes down to zero.  
         [0003]     Multiple print engines have been used in the past to increase productivity. For example, U.S. Pat. No. 5,208,640 issued May 4, 1993 to Kiyoshi Horie et al. shows an image recording apparatus that includes a plurality of recording modules for substantially simultaneously recording of recording sheets images according to image data supplied thereto, an image data supplier for supplying images to the recording modules, a sheet supplier for supplying the recording sheets to the recording modules, and sheet distributors for distributing the recording sheet thus supplied successively by the sheet supplier to the recording modules. Also, U.S. Pat. No. 6,201,946 B1 issued Mar. 13, 2001 to Masakazu Takeuchi et al. discloses a printing system that includes a main printer that is a black and white printer and a support printer, such as, an inkjet a color printer. The system includes a route setting device for printed sheets.  
         [0004]     Obviously, there is still a need for a tandem high end printer system that is not too costly, not too cumbersome with respect to the paper path and does not have to take a 100% hit in productivity when one machine is down.  
         [0005]     Accordingly, an improved tandem machine, high end printing system is disclosed that separates the two 65, 75 or 90 ppm machines and places a common finisher between the machines to simplify the paper path. Using these two machines in the simplex mode results in a digital 130, 150 or 180 ppm system. If one of the machines is for some reason out of order, productivity goes to only 50% instead of 100%. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The foregoing and other features of the disclosure will be apparent and easily understood from a further reading of the specification, claims and by reference to the accompanying drawings in which like reference numerals refer to like elements and wherein:  
         [0007]      FIG. 1  is a schematic elevation view of a typical prior art 65, 75 or 90 ppm printer;  
         [0008]      FIG. 2  is a schematic elevation view of a tandem printer system employing two  FIG. 1  printers linked by a dual finisher positioned between the printers; and  
         [0009]      FIG. 3  is a schematic elevation view of the dual finisher of  FIG. 2 . 
     
    
       [0010]     While the disclosure will be described hereinafter in connection with a preferred embodiment thereof, it will be understood that limiting the disclosure to that embodiment is not intended. On the contrary, it is intended to cover all alternatives, (e.g., 2 copiers, 2 printers, 2 multi-function machines, 1 copier and 1 printer, etc.), modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION  
       [0011]     The disclosure will now be described by reference to a preferred embodiment of a tandem printer system that includes a common finisher positioned therebetween.  
         [0012]     For a general understanding of the features of the disclosure, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to identify identical elements.  
         [0013]      FIG. 1  schematically illustrates a prior art 65, 75 or 90 ppm printer where an original document is positioned in a document handler  27  on a raster input scanner (RIS) indicated generally by reference numeral  28 . The RIS contains document illumination lamps, optics, a mechanical scanning drive and a charge coupled device (CCD) array. The RIS captures the entire original document and coverts it to a series of raster scan lines. This information is transmitted to an electronic subsystem (EES)  29  that controls a raster output scanner (ROS)  30  described below.  
         [0014]      FIG. 1  schematically illustrates an electrophotographic printing machine which generally employs a photoconductive belt  10 . Preferably, the photoconductive belt  10  is made from a photoconductive material coated on a ground layer, which, in turn, is coated on an anti-curl backing layer. Belt  10  moves in the direction of arrow  13  to advance successive portions sequentially through the various processing stations disposed about the path of movement thereof. Belt  10  is entrained about stripping roller  14 , tensioning roller  20  and drive roller  16 . As roller  16  rotates, it advances belt  10  in the direction of arrow  13 .  
         [0015]     Initially, a portion of the photoconductive surface passes through charging station A. At charging station A, a corona generating device indicated generally by the reference numeral  22  charges the photoconductive belt  10  to a relatively high, substantially uniform potential.  
         [0016]     At exposure station B, a controller or electronic subsystem (ESS), indicated generally by reference numeral  29 , receives the image signals representing the desired output image and processes these signals to convert them to a continuous tone or greyscale rendition of the image which is transmitted to a modulated output generator, for example, the raster output scanner (ROS), indicated generally by reference numeral  30 . Preferably, ESS  29  is a self-contained, dedicated minicomputer. The image signals transmitted to ESS  29  may originate from a RIS as described above or from a local and/or remote computer via cable, telephone line or wireless, thereby enabling the electrophotographic printing machine to serve as a remotely located printer for one or more computers. Alternatively, the printer may serve as a dedicated printer for a high speed computer. The signals from ESS  29 , corresponding to the continuous tone image desired to be reproduced by the printing machine, are transmitted to ROS  30 . ROS  30  includes a laser with rotating polygon mirror blocks. The ROS will expose the photoconductive belt to record an electrostatic latent image thereon corresponding to the continuous tone image received from ESS  29 . As an alternative, ROS  30  may employ a linear array of light emitting diodes arranged to illuminate the charged portions of photoconductive belt  10  on a raster-by-raster basis.  
         [0017]     After the electrostatic latent image has been recorded on photoconductive surface  12 , belt  10  advances the latent image to a development station C, where toner, in the form of liquid or dry particles or a solid, is electrostatically attracted to the latent image using commonly known techniques. The latent image attracts toner particles from the carrier granules forming a toner powder image thereon. As successively electrostatic latent images are developed, toner particles are depleted from the developer material. A toner particle dispenser, indicated generally by reference numeral  44 , dispenses toner particles into developer housing  46  or developer unit  38 .  
         [0018]     With continued reference to  FIG. 1 , after the electrostatic latent image is developed, the toner powder image present on belt  10  advances to transfer station D. A print sheet  48  is advanced to the transfer station D by a sheet feeding apparatus  50 . Preferably, sheet feeding apparatus  50  includes a nudger roll  51  which feeds the uppermost sheet of stack  54  to nip  55  formed by feed roll  52  and retard roll  53 . Feed roll  52  rotates to advance the sheet from stack  54  into vertical transport  56 . Vertical transport  56  directs the advancing sheet  48  of support material into the registration transport  120  past image transfer station D to receive an image from photoreceptor belt  10  in a timed sequence so that the toner powder image formed thereon contacts the advancing sheet  48  at transfer station D. Transfer station D includes a corona generating device  58  which sprays ions onto the back side of sheet  48  to assist in removing the sheet from the photoreceptor. After transfer, sheet  48  continues to move in the direction of arrow  60  by way of belt transport  62 , which advances sheet  48  to fusing station F.  
         [0019]     Fusing station F includes a fuser assembly indicated generally by the reference numeral  70  which permanently affixes the transferred toner powder image to the copy sheet. Preferably, fuser assembly  70  includes a heated fuser roller  72  and a pressure roller  74  with the powder image on the copy sheet contacting fuser roller  72 . The pressure roller is cammed against the fuser roller to provide the necessary pressure to fix the toner powder image to the copy sheet. The fuser roll is internally heated by a quartz lamp (not shown). Release agent, stored in a reservoir (not shown), is pumped to a metering roll (not shown). A trim blade (not shown) trims off the excess release agent. The release agent transfers to a donor roll (not shown) and then to the fuser roll  72 .  
         [0020]     The sheet then passes through fuser  70  where the image is permanently fixed or fused to the sheet. After passing through fuser  70 , a gate  80  either allows the sheet to move directly via output path  84  to finisher  90 , or deflects the sheet into the duplex path  100 , specifically, first into single sheet inverter  82 . That is, if the sheet is either a simplex sheet or a completed duplex sheet having both side one and side two mages formed thereon, the sheet will be conveyed via gate  80  directly via output path  84  to disk finisher  90 . However, if the sheet is being duplexed and is then only printed with a side one image, the gate  80  will be positioned to deflect that sheet into the inverter  82  and into the duplex loop path  100 , where that sheet will be inverted and then fed to acceleration nip  102  and belt transports  110 , for recirculation back through transfer station D and fuser  70  for receiving and permanently fixing the side two image to the backside of that duplex sheet, before it exits via exit path  84 .  
         [0021]     Sheets forwarded via output path  84  into finisher  90  are conveyed by nips  91 ,  92  and  93  onto top tray  95 , if stapling is not required. And also when locally scanned and stapling not required. If stapling is required, nip  91  conveys the sheets to nip  94 , which drives them into fingers  97  of disk  96 . Rotation of disk  96  registers the sheets in dual head stapler  98 . After stapling, continued rotation of disk  96  deposits the set of sheets onto main tray  99 .  
         [0022]     After the print sheet is separated from photoconductive surface  12  of belt  10 , the residual toner/developer and paper fiber particles adhering to photoconductive surface  12  are removed therefrom at cleaning station E. Cleaning station E includes a rotatably mounted fibrous brush in contact with photoconductive surface  12  to disturb and remove paper fibers and a cleaning blade to remove the non-transferred toner particles. The blade may be configured in either a wiper or doctor position depending on the application. Subsequent to cleaning, a discharge lamp (not shown) floods photoconductive surface  12  with light to dissipate any residual electrostatic charge remaining thereon prior to the charging thereof for the next successive image cycle.  
         [0023]     Controller  29  regulates the various machine functions. The controller is preferably a programmable microprocessor, which controls all of the machine functions hereinbefore described. The controller provides a comparison count of the copy sheets, the number of documents being recirculated, the number of copy sheets selected by the operator, time delays, jam correction, etc. The control of all of the exemplary system heretofore described may be accomplished by conventional control switch inputs from the printing machine consoles selected by the operator. Conventional sheet path sensors or switches may be utilized to keep track of the position of the document and the copy sheets.  
         [0024]     Turning next to  FIGS. 2 and 3 , illustrated schematic views of a tandem printing system are shown that answer the deficiencies of tandem copiers of the past. For example, the tandem printing system in  FIG. 2  includes two of the 65, 75 or 90 ppm printers disclosed in  FIG. 1  which in a simplex mode results in a high end, digital 130, 150 or 180 ppm machine. User interface (UI)  222  controls the two printers to act as one high-speed print engine. Once the UI is actuated, sheets are fed into the system and machine  1 , referred to as reference numeral  210 , either from a special materials handler (SMH)  212  or High capacity feeder (HCF)  211 . The sheets are conveyed by part of duplex loop  100  in the direction of arrow  213  over photoreceptor  214  to be imaged and later fused. The resultant copies are inverted at  217  (if required) and then deflected away from the duplex loop and outputted into dual finisher station  300 . Dual finisher station  300  preferably comprises two conventional finishers that are each sold as part of the Xerox® 4900 shown schematically in  FIG. 1 . The second machine  220  receives sheets from HCF  221  and conveys the sheets in the direction of arrow  223  past photoreceptor  228  to receive an image with the help of duplex loop  100 . Once the now imaged copies are fused, they are conveyed straight through the inverter  225  (no inversion, unless required) and then sent by duplex path  100  towards finisher station  300 . Copies from the second machine  220  are now moving right to left in  FIG. 2  and are alternated into finisher station  300  with the output from the first machine  210 . A diverter (not shown) causes the copy sheets to exit from the left side of machine  220  into finisher station  300 . If either of printers  210  or  220  is not operable for some reason, the one working machine maintains productivity at 50% instead of 0% as with prior tandem copier/printer systems. Finisher station  300  is positioned in the center of printers  210  and  220  in order to eliminate the complex hardware needed to go around the second printer and to lessen possible machine down time.  
         [0025]     As shown in  FIG. 3 , finisher station  300  includes first and second finishers  310  and  350 , respectively. Sheets conveyed in the direction of arrow  213  from first printer  210  are directed nip  312  which conveys the sheets into first finisher  310  to be stapled as sets or forwarded onto bypass tray  330 . Sheets that are not to be stapled are driven by nips  312 ,  316  and nip  318  onto bypass tray  330 . If the sheets are to be stapled as sets, in finisher  310 , they are driven by nips  312  and  314  into finger  342  or  344  of disk  340 . Disk  340  is rotated in order to register the sheets in dual head stapler  346  where the sheets are stapled into a set. After stapling, disk  340  is rotated in a clockwise direction and allows the set of sheets to drop onto common catch tray  335 . Imaged sheets from second printer  220  conveyed in the direction of arrow  223  enter nip  352  and are either conveyed into finisher  350  via nip  338  into either finger  372  or  374  of disk  370  that drives them into dual stapler head  380  to be stapled into sets or transported up and onto bypass tray  360  by the use of drive nips  352 ,  356  and nip  358 . If the sheets are stapled into sets, they are released from fingers  372  or  374  of disk  370  onto common catch tray  335 . Common catch tray  335  is a conventional tray with a movable platform that is controlled by springs or rotation of screws, etc. and adapted to reposition itself after a predetermined number of sets have been deposited thereon from finisher  310  and/or finisher  350 . Sets from second finisher  350  are ejected alternately with sets ejected from first finisher  310 . Second finisher  350  is rotated 180° with respect to standard positioning of first finisher  310 , i.e., the inboard side of the finisher is facing outboard. It operates the same as first finisher  310 . With second finisher being rotated 180° with respect to the positioning of first finisher  310 , stapled sets are alternated from each finisher and sent to common catch tray  335 . As the staples now alternate between diagonal corners, stapled sets are half as high as would be the case with both finishers positioned the same. The center positioned, dual finisher station  300  is user friendly since it eliminates bending over for stapled sets as the output in common tray  335  is basically waist high due to its positioning on HFC  221 .  
         [0026]     It should now be understood that an improvement has been disclosed for a tandem printer system that includes two 65, 75 or 90 ppm machines that feed imaged sheets into a common finisher that is centrally positioned between the machines to simplify the paper path. Using these two machines in the simplex mode results in a digital 130, 150 or 180 ppm system.  
         [0027]     The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.