Abstract:
A printing machine adapted to print an image on a plurality of different predefined sized sheets, including: means for selecting a sheet of a predefined size to be imaged; means for recording image; means for developing the image; means for transferring the image on the sheet; and a fuser for fusing the image onto the sheet, the fuser includes an endless belt having a plurality of predefined sized fusing areas being selectively activatable, and wherein the plurality of predefined sized fusing areas are arranged in a substantially parallel manner along a process direction of the belt; and means for activating one or more of the plurality of predefined sized fusing areas to correspond to one of the selected predefined sized sheet.

Description:
BACKGROUND 
   This invention relates generally to electrostatographic reproduction machines, and particularly a fuser adapted to handle different paper widths. 
   In a typical electrostatographic reproduction process machine, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is imagewise exposed in order to selectively dissipate charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated at a thermal fusing apparatus at a desired operating temperature so as to fuse and permanently affix the powder image to the copy sheet. 
   In order to fuse and fix the powder toner particles onto a copy sheet or support member permanently as above, it is necessary for the thermal fusing apparatus to elevate the temperature of the toner images to a point at which constituents of the toner particles coalesce and become tacky. This action causes the toner to flow to some extent onto the fibers or pores of the copy sheet or support member or otherwise upon the surface thereof. Thereafter, as the toner cools, solidification occurs causing the toner to be bonded firmly to the copy sheet or support member. 
   One approach to thermal fusing of toner images onto the supporting substrate is illustrated for example in U.S. Pat. No. 5,350,896 and U.S. Pat. No. 4,920,250. This approach involves passing the substrate with the unfused toner images thereon into nip contact between a pair of opposed roller members at least one of which is heated, and its temperature controlled at a desired high operating or fusing temperature level of about 350 degrees Fahrenheit. Another approach as disclosed for example in U.S. Pat. No. 4,355,225 involves radiant fusing in which the substrate with the unfused toner image thereon is passed without contact, through a radiantly heated channel formed in part by a radiant heat member. The radiant heat member maintains the channel temperature during run or operating periods at the desired high operating or fusing temperature of about 350 degrees Fahrenheit. 
   As is well known, when started up, each reproduction machine typically goes through a warm up phase during which the heated member of the fusing apparatus gradually warms up to where the fusing channel or fusing nip reaches and can be maintained at the high fusing temperature. After that, the machine can be activated to run a job reproducing images through a run or operating cycle. After one of such jobs, the machine may be idle (or even go into an idle or a “standby” mode), while waiting for the next reproduction job. Conventionally, an efficiency practice as disclosed for example in U.S. Pat. No. 4,920,250 has been to turn off the power supply upon entering a idle or standby mode, and to allow the temperature of the fusing nip or channel to drop to, and to then be controlled by restarting and shutting off the power supply, at a lower temperature level. 
   Consistent with such a conventional practice, environmentally sensitive and market place regulations, now call for office equipment, particularly electrostatographic reproduction machines, to be more energy efficient. Such environmental regulations or requirements for office products are covered in the United States under what is currently called the “Energy Star Program”, and under various other similar programs in Europe and elsewhere. Such similar programs include “New Blue Angel” (Germany), “Energy Conservation Law” (Japan), “Nordic Swan” (North Europe), and “Swiss Energy Efficiency Label” (Switzerland). 
   Under the “Energy or Power Star Program” in the United States, several modes are defined for copiers or electrostatographic reproduction machines. These modes for example include the operating or copying mode, the standby mode, and the low-power or energy-saver mode. The low-power or energy-saver mode is the lowest power state a copier can automatically enter within some period of copier inactivity, without actually turning off. The copier enters this mode within a specified period of time after the last copy was made. When the copier is in this mode, there may be some delay before the copier will be capable of making the next copy. For purposes of determining the power consumption in this low-power mode, a company may choose to measure the lowest of either the energy-saver mode or the standby mode. 
   The copier or machine enters the standby mode when it is not in the operating or copying mode, but had just previously been in the operating mode. In the standby mode, the copier or machine is consuming less power than when the machine is in the operating mode but is ready to make a copy, and has not yet entered into the energy-saver mode. When the copier is in the standby mode, there will be virtually no delay before the copier is back in the operating mode and capable of making the next copy. 
   When the machine is in the low-power or energy-saver mode, these regulations call for the total power being consumed by the machine to be limited to no more than 125 watts, of which no more than 50 watts can be to the fusing apparatus. When the copier or machine experiences prolonged low-power or energy-saver mode periods, this level of limited power (50 watts) to the fusing apparatus usually is only sufficient to maintain the temperature of the fusing apparatus at a temperature that is significantly below the desired high and ready-to-run fusing temperature of about 350 degrees Fahrenheit. 
   Timely and satisfactory recovery from such a significantly low low-power or energy-saver mode temperature back to the desired high fusing temperature is ordinarily difficult. This is because once the temperature of a fusing apparatus starts to drop or fall, it acquires a thermal inertia which then makes reversal or recovery difficult. Unfortunately, the “power or energy star” regulations, have made such a concern a problem for conventionally designed and controlled fusing apparatus, by calling for the reproduction machine to fully recover from such a low-power or energy-saver mode temperature back up to the desired, high fusing temperature in 30 seconds or less. 
   There is provided a printing machine adapted to print an image on a plurality of different predefined sized sheets including system for selecting a sheet of a predefined size to be imaged; system for recording image; developer for developing the image; transfer system for transferring the image on said sheet; and a fuser for fusing the image onto said sheet, said fuser includes an endless belt having a plurality of predefined sized fusing areas being selectively activatable, and wherein the plurality of predefined sized fusing areas are arranged in a substantially parallel manner along a process direction of said belt; and controller for activating one or more of said plurality of predefined sized fusing areas to correspond to one of said selected predefined sized sheet. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the detailed description below, reference is made to the drawings, in which: 
       FIG. 1  is an elevational view showing relevant elements of an exemplary toner imaging electrostatographic machine including a first embodiment of the fusing apparatus of the present disclosure; and 
       FIG. 2  is an enlarged schematic end view of an embodiment of the fusing apparatus of  FIG. 1 ; 
       FIG. 3  is an enlarged schematic top view of the fusing apparatus showing an end-to-end series arrangement of the fuser belt in accordance with the present disclosure; 
       FIG. 4  is an enlarged schematic cross sectional view of the fuser belt in accordance with the present disclosure. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIG. 1 , it is a simplified elevational view showing relevant elements of an electrostatographic or toner-imaging machine  8 . As is well known, a charge receptor or photoreceptor  10  having an imageable surface  12  and rotatable in a direction  13  is uniformly charged by a charging device  14  and imagewise exposed by an exposure device  16  to form an electrostatic latent image on the surface  12 . The latent image is thereafter developed by a development apparatus  18  that for example includes a developer roll  20  for applying a supply of charged toner particles  22  to such latent image. The developer roll  20  may be of any of various designs such as a magnetic brush roll or donor roll, as is familiar in the art. The charged toner particles  22  adhere to appropriately charged areas of the latent image. The surface of photoreceptor  10  then moves, as shown by the arrow  13 , to a transfer zone generally indicated as  30 . Simultaneously, a print sheet  34  on which a desired image is to be printed is drawn from a sheet supply stack  36  and conveyed along a sheet path  40  to the transfer zone  30 . 
   At the transfer zone  30 , the print sheet  34  is brought into contact or at least proximity with a surface  12  of photoreceptor  10 , which at this point is carrying toner particles thereon. A corotron or other charge source  32  at transfer zone  30  causes the toner image on photoreceptor  10  to be electrostatically transferred to the print sheet  34 . The print sheet  34  is then forwarded to subsequent stations, as is familiar in the art, including the fusing station having a high precision-heating and fusing apparatus  50  of the present disclosure, and then to an output tray  60 . Following such transfer of a toner image from the surface  12  to the print sheet  34 , any residual toner particles remaining on the surface  12  are removed by a toner image bearing surface cleaning apparatus  44  including a cleaning blade  46  for example. 
   As further shown, the reproduction machine  8  includes a controller or electronic control subsystem (ESS), indicated generally by reference numeral  90  which is preferably a programmable, self-contained, dedicated mini-computer having a central processor unit (CPU), electronic storage  102 , and a display or user interface (UI)  100 . At user interface (UI)  100  at user can select one of the plurality of different predefined sized sheets to be printed on. The ESS  90 , with the help of sensors, a look up table  202  and connections, can read, capture, prepare and process image data such as pixel counts of toner images being produced and fused. As such, it is the main control system for components and other subsystems of machine  8  including the fusing apparatus  200  of the present disclosure. 
   Referring now to  FIG. 2 , the fusing apparatus  200  of the present disclosure are illustrated in detail, and are suitable for uniform and quality heating of unfused toner images  213  in the electrostatographic reproducing machine  8 . As illustrated, fusing apparatus  200  includes a rotatable pressure member  204  that is mounted forming a fusing nip  206 . A copy sheets  24  carrying an unfused toner image  213  thereon can thus be fed through the fusing nip  206  for high quality fusing. As illustrated in  FIG. 3 , the fusing device  200  comprises an endless rotatable belt  212  and having a plurality of predefined sized fusing areas  301 ,  302  and  303  with each one of the fusing areas  301 ,  302  and  303  being selectively activatable by controller  300 . Fusing areas  301 ,  302  and  303  are arranged in a substantially parallel manner along a process direction  305  of belt  212 . Controller  300  activating one or more of fusing areas  301 ,  302  and  303  to correspond to sized sheet entering the fusing device  200 . For example the width of fusing area  301  when activated may correspond to A4 sized paper while the width of predefined sized fusing area  302  when activated may correspond to A3; the width of predefined sized fusing area  303  when activated may correspond to A2 sized paper. 
   As further illustrated in  FIG. 3 , belt  212  further comprises a heating element  312  having a common resistive element  312  for output voltage in which the resistance varies with its length (for example: fusing area  303  total resistance is 12 ohms and 1000 watts is required to maintained fusing area  303  at a desired temperature; fusing area  302  total resistance is 8 ohms and 500 watts is required to maintained fusing area  302  at the same desired temperature; and: fusing area  301  total resistance is 4 ohms and 333 watts is required to maintained fusing area  302  at the same desired temperature). Belt  212  also includes a plurality of voltage input conductor taps  501 ,  502  and  503  along the length of belt in which the voltage input taps are selectively engaged which activates the predefined sized fusing areas  301 ,  302  and  303  that corresponds to the selected predefined sized sheet. 
   Power supply  320  supplies a voltage to each one voltage input taps  501 ,  502  and  503 . Power supply supplies  320  each one voltage input taps  501 ,  502  and  503  a different predefine voltage uses voltage dividers  322  and  324  for input taps  501  and  502  respectively to obtained the same desired operating temperate in each predefined sized fusing areas  301 ,  302  and  303 . 
   Temperature controller  600  controls the temperature in each predefined sized fusing areas  301 ,  302  and  303 . Temperature controller includes temperature sensors  601 ,  602  and  603  associated with each predefined sized fusing areas  301 ,  302  and  303 . Temperature controller, coacts with controller  500  and selectively activates one or more of predefined sized fusing areas  301 ,  302  and  303  in response to temperature sensors  601 ,  602  and  603  to maintain a constant temperature in one of said predefined sized fusing areas. Temperature sensors  601 ,  602  and  603  include thermistors for controlling power regulation associated with each predefined sized fusing areas  301 ,  302  and  303 . For example in a possible control strategy all areas of the belt will be at a specified operating set point temperature, a thermistor would control the power regulation. For example if paper was running such that thermistor (TH 2 ) was in control and TH 3  (outside paper path) senses temperature dropping from set point, TH 2  would be opened temporarily and TH 3  would allow power to the entire element until it&#39;s satisfied, then it would be opened and TH 2  would control again. 
   As illustrated in  FIG. 4  belt  212  comprises a thermally conductive ceramic substrate layer  8 , a low friction coating layer  7 , having a conductor/heater interface thereon; conductor  5 ; resistive traces  6 , and ceramic glazing electrical insulation layer  10 . Power delivered at the conductors is delivered to the resistive traces causing them to heat up. The heat is then transferred through the thermally conductive ceramic substrate and the low friction coating layer to the belt. The resistive traces are electrically isolated by the ceramic glazing. 
   In recapitulation, there has been provided a multi-tap heater element design which is a simple, cost effective method to control temperatures of a ceramic element both inside and outside the paper path. The multi-tap heater element design is extremely flexible to application demands. It can be designed for any number of segment lengths, can be used in center and edge registered printers, and for short edge feed and long edge feed printers. The multi-tap heater element design segments can have different power ratings which can be tailored to demand. In addition to demand, segments could be designed in such a way as to maximize energy savings. 
   The multi-tap heater element controls all segments of the heater at a temperature set point even though there is non-uniform power demand across the entire element. The heater is therefore segmented into regions of a desired length based on perceived power demand. To control these segments individually, each segment has a common supply or return path at one end, and a supply or return path that intersects (tapped into) the element trace, defining the circuit. Each segment region now has a circuit path that can be switched according to demand; this demand is monitored by a thermistor. The temperature signal from the thermistor for each segment is fed to a control logic and switching logic. The control logic may consist of a power control algorithm, for example, a PID. 
   The switching logic may control which relay closes to activate a segment circuit. The switching algorithm may use a hierarchy strategy to determine which element needs power. Each subsequent element includes on the last one, and the whole element will be powered by the last relay. Sensing temperature drop in smallest segment is controlled at the relay to the smallest segment. Sensing temperature drop in smallest and next segment is controlled at the relay to the next segment, etc. Sensing temperature drop in any segment is controlled at the relay to the entire element. This also ensures that only one relay is closed at a time. Different design configurations could use a different strategy. 
   It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material.