Abstract:
A fuser assembly and associated method for an electrophotographic machine. The fuser assembly is preferably detachable and intended for use as a second or external fuser assembly. The fuser assembly contemplated may be used as a backup or a complimentary fuser assembly. An electrophotographic machine may include or be adapted to include a detachable or complimentary fuser assembly. Also, a method of electrophotographic printing or copying using a second or external fuser assembly.

Description:
TECHNICAL FIELD 
     The present invention relates generally to electrophotographic machines and to methods of using such machines. More particularly, the present invention relates to a fuser assembly in an electrophotographic machine. 
     BACKGROUND ART 
     A fuser assembly is used in an electrophotographic machine to fuse previously applied toner onto the surface of a print or copy medium, such as paper. A fuser assembly typically comprises a fuser roller in association with a pressure roller which work together to press the toner onto the print medium. As used herein, the word “print” and the various forms thereof are intended to include printing, copying, and any other form of electrophotographic image production (be it production of an image, text, or otherwise). No limitation is intended by or should be read into the use of the word print. The fuser roller is typically heated to increase the toner&#39;s adherence to the print medium. One method of achieving this result is to use toner with some meltable material such as a plastic so that when heated, the toner effectively melts onto and adheres to the print medium. A variety of methods are known to heat the fuser roller, including heating internally using a heating element, such as a fuser lamp. 
     Typically, the print medium is rolled between a fuser roller and another roller to ensure proper contact between the fuser roller and the print medium. Proper printing requires that the toner and print medium will reach a certain temperature to facilitate proper binding or adherence of the toner to the print medium. The temperature reached is a product of a variety of factors, including the initial temperature of the fuser roller, the type of print medium employed (e.g., thin paper, cardstock, cardboard, or transparencies), the time the print medium is in contact with the fuser roller, and the heat capacitance of the fuser roller. Where the heat capacitance of the fuser roller is relatively low, or the heat absorbance of the print medium is relatively high, a faser assembly often needs to operate more slowly to ensure proper fusing of toner to the print medium. 
     The increasing speed and function of electrophotographic printers and copiers has led to a decrease in the contact time between the print medium and the fuser roller. A prior solution to ensure that the print medium and toner reached sufficient temperature was to slow down the throughput of print medium through the printer or copier in order to increase the overall contact time between the print medium and the fuser roller. Throughput references the total amount of printing accomplished within a given time frame. This solution of slowing down the printer has become unacceptable given the present desire for high throughput and accurate printing. 
     Typically, most fuser rollers operate at one temperature. While this temperature may be suitable for one print medium while the printer is operating at a given speed, it often fails to provide the level of flexibility that might otherwise be provided or that is desired to suit a variety of printing functions. It is desirable to print on a variety of different medium, i.e., medium of different thicknesses and compositions. In many instances printing on thicker-than-normal medium gives rise to a need to adjust the fuser roller temperature and/or the printer throughput in order to sufficiently heat the thicker medium to ensure that the toner adheres to the medium properly. The same is true with printing on transparencies or other materials with varying heat capacitance. 
     SUMMARY 
     In one embodiment, a device for improved printing is provided. By operating two or more fusing apparatuses within the same image producing cycle, toner is more likely to be properly and adequately fused to print medium. Preferably, this improvement in fusing does not affect the operating speed of an image producing apparatus. This is achieved since the total time a given piece of print medium is in contact with a fuser assembly or otherwise being operated upon by a fuser assembly is at least doubled, by using at least two fusing devices. In accordance with one aspect, the present invention may help to ensure that fusing is not a rate limiting step to the overall throughput in an electrophotographic process. 
     In accordance with another aspect, the present invention relates to a device for forming images on at least one sheet of medium. The device includes an image forming section for forming an image on the sheet of medium, an output section located substantially downstream of the image forming section. The output section may or may not include a secondary fusing device. Where a secondary fusing device is included, it may be such that it is selectively used by the imaging forming section as needed. Alternatively, the device may include an image forming section, as well as a first fuser and a second fuser to bind toner on a sheet of media. The fusing devices are typically comprised of a plurality of rollers and a motor. 
     In yet another embodiment of the invention, a method of electrophotographic printing is disclosed. Preferably, the method includes the steps of fusing an image to a print medium with a first fuser and fusing the image to the print medium with a second fuser. Alternatively the method may include steps of determining whether the second fusing step is desired, and determining the temperature of the second fuser. 
     Additional advantages and novel features of the present invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be appreciated further by practice of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Features and advantages of the present invention will become apparent to those stilled in the art from the following description with reference to the drawings in which: 
     FIG. 1 is a representational view of a laser printer; 
     FIG. 2 is a side view of components in a fuser assembly in accordance with one embodiment of the present invention; 
     FIG. 3 is a representational block diagram of one embodiment of the present invention; 
     FIG. 4 is a flowchart depicting a method as contemplated in one embodiment of the present invention; 
     FIG. 5 is a flowchart depicting another method as contemplated in one embodiment of the present invention; 
     FIG. 6 is a representational block diagram in accordance with one embodiment of the present invention; and 
     FIG. 7 is a representational block diagram in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     For simplicity and illustrative purposes, the principles of the present invention are described by referring mainly to various exemplary embodiments thereof. Although the preferred embodiments of the invention are particularly disclosed herein, one of ordinary skin in the art will readily recognize that the same principles are equally applicable to, and can be implemented in other systems, and that any such variation would be within such modifications that do not part from the true spirit and scope of the present invention. Before explaining the disclosed embodiments of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of any particular arrangement shown, since the invention is capable of other embodiments. The terminology used herein is for the purpose of description and not of limitation. 
     FIG. 1 illustrates an exemplary printing apparatus or printer, designated by reference number  10 . A computer or other device (e.g., network, Internet, scanner) transmits data to an input port  12  of the printer  10 . This data is analyzed in a formatter  14 . Formatter  14  comprises a microprocessor, related programmable memory and preferably a page buffer. Formatter  14  formulates and stores an electronic representation of each page to be printed. Once the pages have been formatted, data is transmitted to a printer controller  15 . Controller  15  fires laser  16  and controls the drive motor(s), fuser temperature and pressure, and any other print engine components and operating parameters. 
     The data is used to modulate the light being produced by laser  16 . A light beam is reflected off a multifaceted spinning mirror  18 . As each facet of the mirror  18  spins with the light beam, it reflects or “scans” the light beam across the side of a photoconductive drum  20 . Photoconductive drum  20  rotates so that each successive scan of the light beam is recorded on photoconductive drum  20  immediately after the previous scan. In this manner, the data is recorded on photoconductive drum  20 . Toner is electrostatically transferred from developing roller  28  onto photoconductive drum  20  according to the data previously recorded on the photoconductive drum  20  by the light beam. The toner is thereafter transferred from photoconductive drum  20  onto print medium  30  as print medium  30  passes between photoconductive drum  20  and a transfer roller  32 . Photoconductive drum  20  is cleaned of excess toner with a cleaning blade  36 . Photoconductive drum  20  may be completely discharged by discharge lamps  38  before a uniform charge is restored to the photoconductive drum  20  by charging roller  26 , in preparation for the next toner transfer. 
     The print medium  30  is advanced to the photoconductive drum  20  by a pick/feed mechanism  42 . Pick/feed mechanism  42  includes motor driven feed roller  44  and registration rollers  56 . A stack of medium  48  is positioned in an input tray  50  to allow sliding passage of the top piece of print medium  30  into pick/feed area  40  at the urging of feed roller  44 . In operation, as feed roller  44  rotates, the frictionally adherent outer surface  54  of feed roller  44  contacts the upper surface of print medium  30  and pulls it into pick/feed area  40 . As a leading edge of the print medium  30  moves through pick/feed area  40 , it is engaged between the pair of registration rollers  56 . A ramp  58  may be used to guide print medium  30  into the registration rollers  56 . Registration rollers  56  advance print medium  30  fully into image area  52  until it is engaged between photoconductive drum  20  and transfer roller  32 , where toner is applied to the print medium  30  as described above. Once the toner is applied to print medium  30 , it is advanced along the print medium path to fuser  34 . Fuser  34  includes a heated fusing roller  60  and a pressure roller  62 . In certain embodiments, the pressure roller  62  is also heated. As the print medium  30  passes between the rollers  60 ,  62 , toner is fused to the print medium  30  through a process preferably involving heat and pressure. 
     Print medium  30  then passes along the print medium path to a second fuser  61 . Second fuser  61  preferably includes a fusing roller  64  and a pressure roller  66 . In a preferred embodiment, the fusing roller  64  is heated. In certain embodiments, the pressure roller  66  is also heated. Alternatively, the second fuser  61  may include a variety of fusing rollers and/or pressure rollers. As the print medium  30  passes between the rollers  64 ,  66 , toner is fused to the print medium  30  through a process preferably involving heat and pressure. 
     In another embodiment, the printing apparatus  10  includes machinery (not shown) to optionally or selectively direct the print medium  30  through the second fuser  61 . In this way, the second fuser  61  is only employed when necessary to complete the fusing process. The selection of whether or not to employ the second fuser  61  may be performed by a controller within the printing apparatus  10 . The selection may ultimately depend upon a variety of factors, including input from a temperature gauge that checks the temperature of the print medium  30 , or input from a user about whether to use the second fuser  64 , or input from hardware or software that determines whether to use the second fuser  61 , based on the type of print medium  30  being used or the operating temperature of the first fuser  34 . The machinery that might enable the optional use of the second fuser  61  could vary widely. In a preferred embodiment this machinery includes components to route and pass the print medium  30  through the second fuser  61  or alternatively, to route and pass the print medium  30  around the second fuser  61 . 
     Referring to FIG. 2, the fusing roller  60  and pressure roller  62  are mounted on bearings (not shown) which are biased to press the fusing roller  60  and pressure roller  62  against one another. This assembly may be used as a first or second fuser  60 ,  61 . The fusing roller  60  and pressure roller  62  engage to form a nip  80 . Toner is fused to print medium  30  in nip  80 . One or both rollers  60 ,  62  are motor driven to advance print medium  30  through nip  80 . Fusing roller  60  is typically constructed with a metal core  84  and an outer layer  68 . Outer layer  68  is often made of a hard material such as TEFLON™. Metal core  84  is typically hollow. A heating element  70  is positioned inside metal core  84  along the length of fusing roller  60 . Pressure roller  62  is typically constructed with a metal core  72  and a relatively pliable outer layer  74 . Pressure roller  62  may include a TEFLON™ release layer (not shown). Alternatively, pressure roller  62  may include its own heating system such as a heating element (not shown) within the metal core  72  or a series of heating wires  76  extending axially along the length of pressure roller  62 . 
     Referring to FIG. 3, there is illustrated an exemplary block diagram of an image producing apparatus  200  in accordance with the principles of one embodiment of the present invention. The following description of the exemplary block diagram illustrates one manner in which an image producing apparatus  200  may operate. In this respect, it is to be understood that the following description of the exemplary block diagram is but one of a variety of different manners in which the image producing apparatus  200  of the present invention may operate. 
     A fuser  34  may be rotated by operation of a motor  102 . The fuser  34  is preferably configured to apply heat and pressure to print medium, such that with its rotation, toner adhering to the print medium becomes relatively permanently affixed to the print medium to form a particular image (e.g., picture, text, diagrams). 
     A controller  220  may be configured to provide control logic for a fuser assembly  100 . In this respect, the controller  220  may possess a microprocessor, a micro-controller, an application specific integrated circuit, or the like. The controller  220  may be interfaced with a memory  230  configured to provide storage of a computer software that provides the functionality of the image producing apparatus  200 . The memory  230  may also be configured to provide a temporary storage area for data or files received by the image producing apparatus  200  from a host device  240 , such as a computer, server, workstation, image forming device, or the like. The memory  230  may be implemented as a combination of volatile and non-volatile memory, such as dynamic random access memory (“RAM”), EEPROM, flash memory, or the like. It is also within the purview of the present invention that the memory  230  may be included in the host device  240 . 
     The controller  220  may further be interfaced with an I/O interface  250  configured to provide a communication channel between the host device  240 , the image producing apparatus  200 , and a second fuser  120 . The I/O interface  250  may conform to protocols such as RS-232, parallel, small computer system interface, and universal serial bus. In addition, the controller  220  may be interfaced with the motor  102  and the fuser  34 . 
     The image producing apparatus  200  preferably includes interface electronics  260  configured to provide an interface between the controller  220  and components (not shown) for manipulating the motor  102 , for receiving data from a sensor  104 , and for operating the second fuser  120 . It may be appreciated from the foregoing that while the second fuser  120  is intended as a detachable device, it may be adapted so that it draws power from the image producing apparatus  200 . In this way, the second fuser  120  does not require a separate power source. In an preferred embodiment, the second fuser  120  uses a separate power source. In such an embodiment, the second fuser  120  draws power from an external source other than the image producing apparatus  200 . The second fuser  120  should also include the necessary electronics to interface with the controller  220  of the image producing apparatus  200 . Preferably, these interface electronics transmit directly to a controller  122  of the second fuser  120 . Alternatively, the second fuser  120  may lack its own controller  122  and may rely on the controller  220  of the image producing apparatus  200 , or the image producing apparatus  200  may transmit directly from its controller  220  to the second fuser  120 . 
     The image producing apparatus  200  is configured to detachably engage the second fuser  120 . The second fuser  120  operates to further the fusing-process beyond that achieved by the fuser assembly  100 . The second fuser  120  may include its own fuser controller  122 , which may operate in a fashion similar to that of the controller  220  of the image producing apparatus  200 . The fuser controller  122  may be configured to operate components within a second fuser assembly  130  and to communicate with the image producing apparatus  200 , the host device  240 , or another peripheral device (not shown). 
     The second fuser  120  includes the second fuser assembly  130  which includes a motor  132  adapted to operate a fuser  134 . The motor  132  is preferably adapted to operate at varying speeds, while the second fuser assembly  130  is preferably adapted to operate at varying temperatures. The second fuser  120  may be adapted to control and adjust the operating temperature of the second fuser assembly  130  in response to varying inputs. The second fuser assembly  130  may also include a sensor  136  or multiple sensors (not shown) to determine, for instance whether the fuser  134  has reached sufficient operating temperature. The one or more sensors may operate in conjunction with the separate controllers  122  and  220 , as well as the host device  240 , in order to ensure that the fuser  134  has reached a temperature sufficient for the particular print medium being used. The second fuser  120  may also include interface electronics (not shown) similar to those depicted for the image producing apparatus  200 . These interface electronics (not shown) would include electronics (both hardware and software) that facilitate communication between the image producing apparatus  200  and the second fuser assembly  130 . 
     With reference to FIG. 4, there is illustrated an exemplary flow diagram  400  of a manner in which the principles of the present invention may be practiced. The following description of the flow diagram  400  is made with reference to the exemplary block diagram illustrated in FIG. 3, and thus makes reference to the elements illustrated therein. It is to be understood that the steps illustrated in the exemplary flow diagram  400  may be contained as a program, routine, or subroutine in any desired computer accessible medium. For purposes of this disclosure, such mediums, including the memory  230 , may exist as internal and external computer memory units, and other types of computer accessible medium, such as a compact disc readable by a storage device. Thus, although particular reference is made in the following description of FIG. 3 to the controller  122  or  220  as performing certain functions of the image producing device, it is to be understood that those functions may be performed by any apparatus  200  capable of executing the above-described functions. 
     At step  402 , data is received from the host device  240 . This data includes image data as well as data relating to the necessary operating temperature of the second fuser  120  or the type of print medium about to be used or intended for a particular image producing job. Where the data relates to the operating temperature of the second fuser  120 , it may be passed from the image producing apparatus controller  220  to the second fuser controller  122  and along to the second fuser assembly  130 . Thus, the data may include a signal to check the temperature and return it to the image producing apparatus controller  220  for a time delay calculation prior to continuing the image producing process. Alternatively, the data may include a signal with the type of print medium to be employed, and leave any time delay calculation for the second fuser controller  122 . 
     At step  404 , the image is placed on and fused to the print medium as previously described with reference to FIGS. 1 and 2. At step  406 , a determination is made as to whether supplemental basing is necessary. This may be determined by the image producing apparatus controller  220  where, for instance, secondary or supplemental basing is known to be unnecessary. Where supplemental fusing is determined to be unnecessary the process moves to step  408 . 
     In step  408 , the print medium is sent directly to a bin for later retrieval by a user, or for further processing or handling by another device, such as a stapler or binding apparatus. This step may be followed by deactivating the second fuser  120  where, for instance, no further print jobs are spooled or otherwise scheduled. This deactivating step may simply involve stopping the motors that drive the second fuser  120 , and may also involve shutting off any heating elements associated with the second fuser  120 . 
     Where supplemental fusing is determined to be desirable, the process moves to step  410 . At step  410 , the print medium is fed to a second fuser  120 . At step  412 , the second fuser  120  is activated and operates to further fuse the toner to the print medium. This activation step may involve activating the motors that drive the second fuser  120 , and may also involve activating any heating elements associated with the second fuser  120 . In the latter instance, activating any heating elements associated with the second fuser  120  may take place earlier in the process so as to allow ample time for the second fuser  120  to reach the desired operating temperature. The process then proceeds to step  408  as described above. Two high throughput fusers operating in this fashion may achieve the equivalent beating and pressure application of one fuser operating at a slower speed. In this way, print medium may be continuously fed through a printer with little to no delay attributable to fuser operation. 
     FIG. 5 shows an exemplary flow diagram of a heating process  500  in which the principles of the present invention may be practiced. The following description of the flow diagram  500  is made with reference to the exemplary block diagram illustrated in FIG.  3  and the flow diagram depicted in FIG. 4, and thus making reference to the elements illustrated therein. It is to be understood that the elements of the heating process  500  may exist as a program, routine, or subroutine within the process depicted in FIG.  4  and may be included within a subroutine of or as part of any computer accessible medium. 
     Where step  402 , as previously described above, includes a signal to check the temperature of the second fuser assembly  130 , the process continues to step  502  where a sensor  136  determines the temperature of the second fuser assembly  130 . Step  504  involves determining whether the temperature returned by the sensor  136  is above a predetermined temperature. Step  504  may be carried out by either the image forming apparatus controller  220  or the second fuser controller  122 . If the temperature returned by the sensor  136  is above a predetermined temperature then the process continues to step  410  and the print medium is fed to the fuser  120 . If the temperature returned by the sensor  136  is below a predetermined temperature, then the process continues to step  506 . At step  506 , the second fuser  134  is heated to achieve an appropriate temperature. The process continues back to step  502  to recheck the temperature or alternatively may simply continue to step  410 . 
     In certain instances it may be necessary to delay the image producing process of FIG. 4 while the heating process of FIG. 5 is completed. Preferably, a heating process of FIG. 5 is complete by the time step  410  of FIG. 4 is reached so that the print medium may proceed directly to the second fuser  120  without delay. This helps to ensure that a proper fusing temperature is reached by the print medium. 
     FIG. 6 depicts a block diagram of one embodiment of the present invention as a multi-bin image producing apparatus  600 . In FIG. 6, an image producing apparatus  200  is shown with a first bin  602  and a second bin  604  affixed thereto. Both or either of these bins may be detachably connected to the image producing apparatus  200 . The first bin  602  is intended for use when no secondary fusing is required. The second bin  604  is used when secondary fusing is required. The second bin  602  includes a fuser therewith or has a fuser attached thereto or is otherwise associated with a second fuser  120 . For purposes of the present disclosure, the words “associated with” mean to be attached to, including detachable connections, or otherwise working in combination with. It should be appreciated that a variety of other bins may be attached to or associated with the image producing apparatus  200  of FIG.  6 . This multi-bin image producing apparatus  600  is useful where for instance, a variety of print jobs are run through a single image producing apparatus and the print jobs vary in the type of print medium they employ. 
     As previously described with reference to FIG. 4, it is sometimes desirable to send print medium directly to a bin such as first bin  602  for further handling or storage for later retrieval. Alternatively, it is sometimes desirable to send print medium to a second fuser to complete the image creation process and ensure proper adherence of the toner to the print medium. 
     FIG. 7 depicts a block diagram of another, embodiment of the present invention as a multi-bin image producing apparatus  700 . In FIG. 7, an image producing apparatus  200  is shown with a second fuser  120  detachably connected thereto or otherwise associated therewith. A variety of bins  702 ,  704 , and  706  are associated with the second fuser  120 . In this way, print medium is always run through the second fuser  120  before being delivered to one of the bins  702 ,  704 , and  706 . Where it is unnecessary to provide secondary fusing, print medium may pass directly through the second fuser  120 . For instance, if the heating elements within the second fuser  120  are turned off. It should be appreciated that a variety of other bins may be attached to or associated with the image producing apparatus  200  of FIG.  7 . 
     While the invention has been described with reference to certain exemplary embodiments thereof, those skilled in the art may make various modifications to the described embodiments of the invention without departing from the true spirit and scope of the invention. The term and descriptions used herein are set forth by way of illustration only and not meant as limitations. In particular, although the present invention has been described by examples, a variety of devices would practice the inventive concepts described herein. Thus, although the present examples relate to a printer, the present invention would have application to a copier, or any other electrophotographic image-producing device employing a fuser. Although the invention has been described and disclosed in various terms and certain embodiments, the scope of the invention is not intended to be, nor should be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved, especially as they fall within the breadth and scope of the claims here appended. Those skilled in the art will recognize that these and other variations are possible within the spirit and scope of the invention as defined in the following claims and their equivalents.