Patent Publication Number: US-6982781-B2

Title: Automatic fuser control

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to image reproduction devices or image forming apparatuses, such as high speed digital printers. More specifically, the present invention relates to improving the productivity of print jobs handled by such devices, apparatuses and printers when the stock for the print jobs is heterogeneous. 
     BACKGROUND OF RELATED ART 
     It is well known by those skilled in the art that many image forming apparatuses utilize fusing mechanisms (“fusers”) to bond toner, ink or other image substances to pages receiving reproduced images. Fusers often function at an effective operating temperature needed for proper bonding of the image substance to the target page. If the fuser temperature is too low, the bond may be inadequate, possibly leading to smudging when the page is touched. With each fused page is a drop in the fuser temperature and the need for the fuser to recover to the appropriate temperature before the next page should be processed. 
     It is also well understood that different printing stock may require a longer fusing time (“dwell time”) than others. Thus the appropriate dwell time for a particular stock is often directly proportional to metrics such as the stock thickness, and the amount and type of coating on the stock surface. 
     High speed digital copying machines for processing large print jobs are capable of copying books and other documents using mixed stock. For example, several pages of a pamphlet, book, etc. may be printed on “thin” stock making up the body of the book, while the book cover is typically printed on heavier stock requiring a longer dwell time. The typical prior art approach to printing a mixed stock print job is to print the entire job using the slower dwell time required by the heavier stock. For example, a print job using low weight paper or stock (often measured in gsm—“grams per square meter” or pounds per 500 sheets) might have a productivity of 66.6 prints per minute (PPM), while a print job using heavy stock might need to have a 50 percent reduction in the productivity at 33.3 PPM. So that all of the papers are properly fused, the entire print job is processed at 33.3 PPM. 
     As a further illustration, the prior art approach to print a seven-page print job such as a pamphlet with 5 regular or lightweight stock pages for the body and 2 heavyweight stock pages for the cover pages might reduce the productivity for the entire job to 33.3 PPM to accommodate the heavy cover stock, rather than a productivity (e.g., 66.6 PPM) closer to that available if just the lightweight stock were used. 
     One prior art approach is described by U.S. Pat. No. 6,160,974 issued to Takahiro Yoshikawa, et al. In the Yoshikawa patent an image forming apparatus such as a conventional copying machine allows a user to choose an “increased interval mode” for processing stock from a particular paper bin or paper tray when the bin or tray contains heavyweight or other paper requiring extra fusing. In other words, the interval between sheets to be processed is standard for all pages, unless the paper emanates from a paper bin which the user has designated for the Copies Per Minute Down Mode, in which case the interval is increased between pages to give the fusing unit extra time to return to the target operating temperature after a thick page has been processed. 
     In an alternate mode of the Yoshikawa patent approach, the sheet interval is increased during a print cycle when the temperature of the fusing unit drops below a threshold. 
     What is desirable is a reproduction device that automatically determines the fuser dwell time according to the stock required in the print job without the user having to specify particular paper trays or bins for increased dwell times. It is also desirable to carry out the above aspirations for stored print jobs that are expected to be processed at high rates using the likes of high speed digital printers. 
     SUMMARY 
     In view of the above-identified problems and limitations of the prior art, the present invention provides a print job processing method that at least includes: providing processing attributes for particular print stock, including a predetermined fuser dwell time; establishing a print job, including the stock to be used for each page of the print job; for each page in the print job, selecting the appropriate subsystem containing the stock specified for the particular page; for each page in the print job, transferring image substance to each sheet to be printed, the placement of the image substance corresponding to an image to be duplicated on the page; matching the appropriate portion of the processing attributes to each subsystem; for each page, automatically fusing the image substance to the page according to the dwell time established by the processing attributes for the stock used for the page; and outputting processed pages. 
     The present invention also provides a print job processing system that at least includes: a stock library adapted to provide processing attributes for particular print stock, including a predetermined fuser dwell time; a user input adapted to establish a print job, including the stock to be used for each page of the print job; a plurality of subsystems containing stock, adapted to be selected as required for each page in the print job, according to the stock specified for the particular page; an image substance transferor adapted to transfer, for each page in the print job, image substance to each sheet to be printed, the placement of the image substance corresponding to an image to be duplicated on the page; a stock library/subsystem matcher adapted to match the appropriate portion of the stock library to each subsystem; a fuser adapted to automatically fuse the image substance to the page according to the dwell time established by the stock library for the stock used for the page; and an output adapted to output pages processed by the fuser. 
     The present invention is not limited to image forming apparatuses using toner as the image substance for forming images on the pages. Apparatuses using certain types of ink as the image substance can also employ the present invention. Further, the present invention is suitable for both monochromatic and color reproduction techniques. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features of the present invention will become apparent to those skilled in the art from the following description with reference to the drawings, in which: 
         FIG. 1  is a general schematic diagram of the present-inventive system for optimizing printer productivity by automatically adjusting fuser dwell times for different printing stock; and 
         FIG. 2  is a flowchart detailing the steps employed by the present-inventive method for optimizing printer productivity by automatically adjusting fuser dwell times for different printing stock. 
     
    
    
     DETAILED DESCRIPTION 
     The term “printer” refers, for example, to reproduction devices in general, such as printers, facsimile machines, and copiers, and the term “print job” refers, for example, to information including the electronic item or items to be reproduced. 
     General System Description 
     The basic components of the system  100  incorporating the present-inventive automatic fuser dwell time adjustment feature are shown in  FIG. 1 . In embodiments, the system  100  is subsumed by a high speed digital printer, although it will be appreciated by those skilled in the art that this need not be so. 
     A functioning system for processing print jobs nominally includes components such as a photoreceptor belt  120  for registering and transporting images in a manner well-known in the art. Numerous sources exist that describe the general image reproduction process in more detail than here. One such source, for example, is U.S. Pat. No. 6,484,934 issued to David L. Salgado, and assigned to the same assignee of the present application for Letters Patent, which patent is hereby incorporated by reference. 
     Several subsystems  132 ,  134 , and  136  contain stock for having print images transferred thereto. The subsystems can contain different types of print stock requiring different dwell times for effective fusing. 
     During an image transfer operation, a substrate page  116  from one of the subsystems  132 ,  134 ,  136  has an image substance such as toner deposited thereon by a toner unit  170  according to a page image  174  transferred from the photoreceptor belt  120  along a defined paper feed path  126 . Those skilled in the art will appreciate that the image substance can be other than toner, including ink. The toner is fused to the substrate  116  in a fuser unit  180  and then output ( 190 ) for further handling such as collating, sorting, binding, etc. 
     The dwell time of the fuser  180  and the speed of the path are controlled by a fuser control  184  and a path control  128 , respectively. The fuser control  184 , path control  128 , and indeed the printing operation as a whole are controlled by the printer control logic represented schematically as  140 . The printer control  140  receives input from, inter alia, a user accessible control panel  160  and a stock library  150 . The stock library  150  contains for all types of stock anticipated to be utilized by the system  100 , information to be used by the printer control  140 , such as the dwell time required for acceptable bonding and other processing attributes for the stock. 
     The amount of dwell time might be proportional to the weight of the stock used, the thickness of the stock used, or the amount of coating on the stock used. Alternatively in the case of coated paper, the fuser dwell time can be a standard value when the coating is below a threshold level, and can be a longer value when the coating exceeds the threshold level. The coating and thresholds correspond to types of coated stock that will use standard fuser dwell times and types of coated stock that that will need a longer fuser dwell time. 
     General Print Job Process Description 
     The present-inventive process in embodiments for executing print jobs requiring mixed stock and variable fuser dwell times is illustrated as an algorithm  200  in  FIG. 2 . 
     The process is initiated by a user requesting (via the control panel  160 ) that a print job be executed, the print job requiring more than one type of stock (Step  202 ). The print job may be already stored in memory, or stored while being produced on the fly. 
     The user can choose to execute the print job using a uniform dwell time or have the dwell time automatically adjusted for different stocks. If the user has not chosen the variable fuser dwell option, the print job is executed at a uniform dwell (the longer dwell needed for the stock requiring extra bond time) in Steps  204  and  206 . The algorithm stops after executing Step  222 . When the user selects the variable dwell option (Steps  204  and  208 ), the system  100  begins to process each page of the print job by selecting the appropriate subsystem for the required stock. The stock library  150  supplies the necessary dwell and other information for the subsystem to the printer control  140 . 
     The image reproduction substance such as toner is applied to each page of the print job in Step  210 . Under the control of the printer control  140 , the path control  128  controls the path speed according to the type of stock currently being processed. The fuser control  184  also controls the dwell time of the fuser unit  180  to match that indicated by the stock library  150  (Steps  212  and  214 ). The dwell time can be controlled in a variety of ways, including varying the speed of rollers used to form the nip accepting each page. 
     The pages output by the fuser unit  180  are output during a constant paper pitch mode in the preferred embodiment, where “pitch” defines a sheet length (or width) plus the distance between the end of one sheet and the beginning of another sheet to be processed (Step  216 ). When increased dwell time has caused a delay in the output, the pitch is merely skipped. Thus, no page is output for that pitch, but the next page is output during the next available pitch once it is ready. Steps  208 – 216  are carried out for each page of the print job (Step  218 ). 
     The output pages are further processed according to print job or user instructions, including such steps as sorting the copies of the print job, collating the copies of the print job, or binding the copies of the print job (Step  220 ). 
     Variations and modifications of the present invention are possible, given the above description. However, all variations and modifications which are obvious to those skilled in the art to which the present invention pertains are considered to be within the scope of the protection granted by this Letters Patent.