Patent Publication Number: US-8121528-B2

Title: Apparatuses useful for printing and methods of treating marking material on media

Description:
BACKGROUND 
     In some printing processes, images are formed on media using a marking material that is treated to fix the marking material onto the media. Printing apparatuses that are used for such printing processes can include members having opposed surface forming a nip. During printing processes, media are fed to the nip, where the marking material is treated to fix the images onto the media. 
     It would be desirable to provide apparatuses and methods for treating marking material on media that can provide reduced warm-up times and higher energy efficiency. 
     SUMMARY 
     Embodiments of apparatuses useful for printing and methods of treating marking material on media are disclosed. An exemplary embodiment of the apparatuses useful for printing comprises a roll including a first outer surface; a continuous belt including an inner surface and a second outer surface forming a nip by contact with the first outer surface, the belt being driven to rotate by rotation of the roll; a heater disposed inside of the belt and comprising a first heating surface contacting the inner surface of the belt at the nip; and a heating fin in thermal contact with the heater, the heating fin including a second heating surface extending circumferentially in contact with a pre-nip portion of the inner surface of the belt. Thermal energy is conducted from the heater to the heating fin. The second heating surface pre-heats the pre-nip portion of the belt before the pre-nip portion is rotated to the nip, and the first heating surface of the heater heats the pre-heated, pre-nip portion at the nip. 
    
    
     
       DRAWINGS 
         FIG. 1  illustrates an exemplary embodiment of a printing apparatus including a fixing device. 
         FIG. 2  is a cross-sectional view of an exemplary embodiment of fixing device. 
         FIG. 3  is an isometric view of the fixing device of  FIG. 2 . 
         FIG. 4  depicts curves showing the fuser belt temperature as a function of the number of prints made (time) for a fuser with a heating fin and a fuser without a heating fin. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed embodiments include an apparatus useful for printing, which comprises a roll including a first outer surface; a continuous belt including an inner surface and a second outer surface forming a nip by contact with the first outer surface, the belt being driven to rotate by rotation of the roll; a heater disposed inside of the belt and comprising a first heating surface contacting the inner surface of the belt at the nip; and a heating fin in thermal contact with the heater, the heating fin including a second heating surface extending circumferentially in contact with a pre-nip portion of the inner surface of the belt. Thermal energy is conducted from the heater to the heating fin. The second heating surface pre-heats the pre-nip portion of the belt before the pre-nip portion is rotated to the nip, and the first heating surface of the heater heats the pre-heated, pre-nip portion at the nip. 
     The disclosed embodiments further include a fuser, which includes a pressure roll including a first outer surface; a continuous fuser belt including an inner surface and a second outer surface forming a nip by contact with the first outer surface, the fuser belt being driven to rotate by rotation of the pressure roll; a heater disposed inside of the belt and comprising a planar first heating surface contacting the inner surface of the fuser belt at the nip; and a heating fin in thermal contact with the heater, the heating fin including a curved second heating surface extending circumferentially in contact with a pre-nip portion of the inner surface of the fuser belt. Thermal energy is conducted from the heater to the heating fin. The second heating surface pre-heats the pre-nip portion of the fuser belt before the pre-nip portion is rotated to the nip, and the first heating surface of the heater heats the pre-heated, pre-nip portion at the nip. 
     The disclosed embodiments further include a method of treating a marking material on a medium, which comprises feeding a medium with a marking material to a nip formed by a first outer surface of a roll contacting a second outer surface of a belt; rotating the belt relative to a heater disposed inside of the belt and comprising a first heating surface contacting the inner surface of the belt at the nip and relative to a heating fin in thermal contact with the heater, the heating fin including a second heating surface extending circumferentially in contact with a pre-nip portion of the inner surface of the belt; activating the heater to conduct thermal energy from the heater to the heating fin to pre-heat the pre-nip portion of the belt with the second heating surface before the pre-nip portion is rotated to the nip and to heat the pre-heated, pre-nip portion with the first heating surface at the nip; and contacting the medium with the first outer surface of the belt and second outer surface of the belt at the nip to treat the marking material. 
     As used herein, the term “printing apparatus” can encompass any apparatus, such as a copier, bookmaking machine, multifunction machine, and the like, or portions of the apparatuses, that can perform a print outputting function for any purpose. 
     FIG. 1 illustrates an exemplary printing apparatus 100 disclosed in U.S. Pat. No. 7,228,082, which is incorporated herein by reference in its entirety. The printing apparatus  100  includes a fuser  110  with a rotatable, continuous belt  112  and a pressure roll  120  defining a nip  122 . The printing apparatus  100  further includes a rotatable photoreceptor  130 . To form a toner image on the photoreceptor  130 , a charging device  140  is activated to charge the outer surface of the photoreceptor  130 . The photoreceptor  130  is rotated to an exposure device  150  to form an electrostatic latent image on the photoreceptor  130 . Then, the photoreceptor  130  is rotated to a developer device  160 , which applies toner particles to the electrostatic latent image to form the toner image on the photoreceptor  130 . The toner image is transferred from the photoreceptor  130  to a medium  162 , e.g., a sheet of paper, conveyed from a sheet supply stack  164 . The medium  162  on which the toner image has been formed is conveyed to the nip  122  of fuser  110 . The printing apparatus  100  includes a controller  170  configured to control operation of the image-forming devices during printing. After the medium  162  passes through the nip  122 , the medium is conveyed to an output tray  180 . A cleaning device  182  removes residual toner particles from the photoreceptor  182  before the imaging process is repeated for another medium. 
     In fusers, increased demands for energy efficiency can impose limits on warm-up times. In such fusers, there is a need to be able to heat the fusing surface of a fusing member, e.g., a fuser belt, from a stand-by temperature to the desired temperature more quickly. It has been determined that a low-mass fuser belt can be heated quickly with a heater to reduce warm-up time. However, it is desirable that the amount of surface dwell between the heater and the fusing belt be sufficiently-high to supply sufficient thermal energy to the fuser belt to heat media to a desired temperature with the fuser belt. The amount of surface dwell that is sufficient can be higher in fuser belts comprised of polymeric materials that have relatively low thermal conductivity. It is desirable to reduce temperature “droop,” which is caused by the temperature of the fuser belt falling to below a desired temperature (e.g., a temperature set point) as a result of media absorbing more thermal energy from the fuser belt than is supplied to the fuser belt by the heater. When the temperature droop of the fuser belt is too large, poor fixing of marking material on media can occur. 
     Fixing devices for fixing marking materials on media are provided. The fixing devices include opposed members that can apply heat and pressure to media to fix marking material onto the media. Embodiments of the fusers can provide increased fuser dwell and low warm-up times. Embodiments of the fusers can control temperature droop of the fusing member by achieving a balanced thermal input/thermal output. 
       FIGS. 2 and 3  illustrate an exemplary embodiment of the fixing devices. The illustrated fixing device is a fuser  200 . Embodiments of the fuser  200  shown in  FIGS. 2 and 3  can be used, e.g., in place of the fuser  110  in the printing apparatus  100 . The printing apparatus  100  can be used to produce prints from various media, such as coated or uncoated (plain) paper sheets, having various sizes and weights. 
     The fuser  200  includes a continuous fuser belt  210  with an outer surface  212  and inner surface  214 , and a pressure roll  220  with an outer surface  222  contacting the outer surface  212 . The outer surface  212  and the outer surface  222  of the fuser belt  210  form a nip  224 . In embodiments, the pressure roll  220  is a drive roll and the fuser belt  210  is free-spinning and driven by engagement with the pressure roll  220 . The pressure roll  220  rotates clock-wise to cause the belt to rotate counter-clockwise to convey media though the nip  224 . 
     Embodiments of the fuser belt  210  can include two or more layers comprised of polymeric materials. For example, the fuser belt  210  can include a base layer forming the inner surface  214 , an intermediate layer overlying the base layer, and an outer layer forming the outer surface  212 , overlying the intermediate layer. The inner layer can be composed of polyimide, or the like; the intermediate layer of silicone, or the like; and the outer layer of a fluoropolymer having low-friction properties, such as polytetrafluoroethylene (Teflon®), or the like. The fuser belt  210  has a thickness and material composition that allows it be elastically deformed in the fuser  200 . 
     In other embodiments, the fuser belt  210  can be comprised of a metal or metal alloy, such as steel, stainless steel, or the like. The metal or metal alloy can be coated with an elastomeric material forming an intermediate layer. The elastomeric material can be silicone, or the like. A material with low-friction properties, such as polytetrafluoroethylene (PFTE), perfluoroalkoxy (PFA), or the like, can be applied over the intermediate layer to form an outer layer of the fuser belt  210 . 
     The illustrated pressure roll  220  includes a core  224 , an inner layer  226  provided on the core  224 , and an outer layer  228  provided on the inner layer  226 . The core  224  can be comprised of a metal, metal alloy, or the like; the inner layer  226  of an elastic material, such as silicone or the like; and the outer layer  228  of a low-friction material, such as Teflon®, or the like. 
     The fuser  200  further includes a heater  230  located inside of the fuser belt  210 . The heater  230  is stationary and extends axially (longitudinally) along the fuser belt  210 . In embodiments, the heater  230  is located at the nip  224  and configured to heat the fuser belt  210  rotated to the nip  224 . The heater  230  includes a heating surface  232  and an opposite surface  234 . The heating surface  232  is configured to contact the inner surface  214  of the fuser belt  210 . The heater  230  heats the fuser belt  210  by thermal conduction. The heating surface  232  can be planar, as shown. In embodiments, substantially the entire heating surface  232  can contact the inner surface  214  of fuser belt  210 . 
     The body of the heater  230  can be comprised of ceramic materials. The ceramic materials have sufficiently-high thermal conductivity to transfer thermal energy to the fuser belt  210  rapidly when the heater  230  is activated. In embodiments, the heater  230  has a low thermal mass, allowing it to be rapidly heated when activated. The heating surface  232  can have a smooth finish to reduce friction between it and the inner surface  214  of the rotating fuser belt  210 . A thermally-conductive lubricant can be applied to the heating surface  232  to reduce friction between it and the inner surface  214  during rotation of the fuser belt  210 . 
     In embodiments, the heater  230  includes one or more heating elements (not shown). The heating elements are activated to heat the heating surface  232 . The heating elements extend along the axial direction of the fuser belt  210 . The heating elements can be embedded in the heater  230 , for example. The heating elements can be connected to a power supply  240  and a controller  242  connected to the power supply  240  to control the supply of power to the heating elements to heat the fuser belt  210  to a desired temperature. The temperature of the fuser belt  210  is typically measured at the outer surface  214  close to the inlet end of the nip  224 . In embodiments, the heating elements can heat substantially the entire heating surface  232  that is in contact with the fuser belt  210 . 
     The fuser  200  further includes a heating fin  250 . The illustrated embodiment of the heating fin  250  includes a planar portion  252  and a curved portion  254 . The planar portion  252  is positioned in thermal contact with the surface  234  of the heater  230 . As shown, the curved portion  254  of the heating fin  250  includes an outer heating surface  256  contacting the inner surface  214  of the fuser belt  210 . The heating surface  256  has a curved shape. For example, the heating surface  256  can be generally semi-circular shaped, as depicted. The heating fin  250  extends along the axial direction of the fuser belt  210 . The heater  230  and heating fin  250  are adapted to heat the portion of the outer surface  214  of the fuser belt  210  that defines the media path of media passing through the nip  224  (i.e., contacts the media). The heating fin  250  conducts thermal energy produced by the heater  230  to heat a pre-nip portion of the fuser belt  210  adjacent to an inlet end of the nip  224 . In embodiments, the curved portion  256  of the heating fin  250  can be positioned in contact with the heater  230 . In embodiments, the pre-nip portion of the fuser belt  210  can extend circumferentially over an angle of at least about 30°, such as at least about 45°, at least about 60°, or at least about 90°, about the fuser belt  210 . 
     In embodiments, the curved portion  254  of the heating fin  250  is not actively heated by a heating element associated with the curved portion  254 . In the illustrated embodiment, the heating fin  250  is comprised of a material having sufficiently-high thermal conductivity to conduct sufficient heat from the heater  230  along the planar portion  252  and to the curved portion  254  to heat the pre-nip portion of the fuser belt  210  to the desired temperature. In other embodiments, the heater and heating fin can be configured to conduct heat directly from the heater to the curved portion of the heating fin. The pre-nip portion of the fuser belt  210  can be heated to the desired temperature in embodiments of the fuser belt  210  having different structures and material compositions. For example, embodiments of the fuser belt  210  can have a coating of a polymeric material, such as an elastomer, that has a relatively lower thermal conductivity than other materials forming other portions of the fuser belt  210 . The heating fin  250  can be comprised, e.g., of a metal or metal alloy, such as aluminum, aluminum alloys, copper, copper alloys, and the like. The heating fin  250  can be a fabricated plate of a single piece of material, for example. The heating fin  250  can also have a low thermal mass to allow it to quickly reach a desired heating temperature and have only a minor effect on the warm-up time of the fuser  200 . In embodiments, the heating fin  250  can have a thickness of less than 3 mm, e.g., less than about 2 mm or less than about 1 mm. 
     The fuser  200  can have a warm-up time for the fuser belt  210  to reach the desired temperature for treating marking material on media of less than about 15 seconds. Heating the heating fin  250  with thermal energy produced by the heater  230  can reduce the loss of thermal energy that otherwise would not be transferred to the fuser belt  210 , but would be transferred to other portions of the fuser  200  or to the environment. 
     In embodiments, the heating fin  250  is supported by a belt guide  260  located inside of fuser belt  210 . The belt guide  260  includes an outer guide surface  262  contacting a portion of the inner surface  214  of the fuser belt  210 . The belt guide  260  can be comprised of a material having low thermal conductivity (i.e., a thermal insulator) to reduce heat transfer from the heating fin  250  and fuser belt  210  to the belt guide  260 . 
     The belt guide  260  is attached to a heater housing  270 . The heater housing  270  extends along the axial direction (longitudinal direction) of the fuser roll  210 . As shown, a portion of the heater housing  270  can overlie the planar portion  252  of the heating fin  250 . The heater housing  270  can be comprised of a material having low thermal conductivity (i.e., a thermal insulator) to reduce heat transfer from the heating fin  250  to the heater housing  270 . 
     In embodiments, the fuser  200  can include a load member (not shown) constructed to apply a load to the heater housing  270  to urge the heating surface  232  into contact with the inner surface  214  of fuser belt  210  at the nip  224 . The load member extends axially along the fuser belt  210 . The load member can comprise, e.g., a metal or metal alloy. 
     During operation, media are fed to the nip  224 .  FIG. 2  shows a medium  275  traveling in the process direction A toward the nip  224 . The medium  275  can be, e.g., a paper sheet with at least one toner image. At the nip  224 , the outer surface  212  of fuser belt  210  and the outer surface  222  of pressure roll  220  contact opposite surfaces of the medium  275 . The fuser belt  210  supplies sufficient thermal energy to the medium  275  to heat the marking material to a sufficiently-high temperature to fix the marking material. The heating fin  250  pre-heats the pre-nip portion of the fuser belt  210  as the portion rotates past the heating surface  256  before rotating further to the nip  224 . In embodiments, the pre-heated portion of the fuser belt  210  can enter the nip  224  at or above the temperature set point for fixing marking material, such as toner, onto media fed to the nip  224 . At the nip  224 , the heater  230  supplies additional thermal energy to the fuser belt  210 . 
     In the fuser  200 , a typical dwell time is about 20 ms. In embodiments, the arc length of the portion of the fuser belt  210  heated by the heating fin  250  and heater  230  can be equal to at least the media dimension in the process direction A. When the heating fin  250  pre-heats the fuser belt  210  to at least the temperature set point, the amount of work that the heater  230  then needs to supply to fix the marking material onto media at the nip  224  is reduced as compared to heating the fuser belt  210  only at nip  224  with the heater  230 . When the pre-heated portion of fuser belt  210  arrives at the nip  224  at about the temperature set point or higher, the heater  230  needs to only supply an additional amount of thermal energy sufficient to increase the temperature of the marking material and media to the desired temperature, e.g., the fusing temperature of toner. The fusing temperature can be, e.g., about 180° C. to about 210° C. for different media weights. In the fuser  200 , media can be contacted with the fuser belt  210  at or above the temperature set point for about the entire dwell time to produce a high fix level on media. 
     In embodiments, the fuser  200  including a heating fin  250  can provide improved temperature uniformity in both circumferential and axial directions in the fuser belt  210  during print jobs.  FIG. 4  depicts modeled curves showing the fuser belt temperature at the outer surface of the fuser belt close to the inlet of the nip as a function of the number of prints (time) made for a fuser with a heating fin and a fuser without a heating fin. As shown, the fuser including a heating fin produces a generally uniform fuser belt temperature during a print run, while the fuser belt in the fuser without a heating fin shows a significant reduction in temperature during the print run. The outer surface temperature of the fuser belt with the heating fin displays the form shown in  FIG. 4  in both circumferential and axial directions (i.e., across the media path) in the fuser belt. 
     As shown in  FIG. 2 , a sensor  280  (e.g., optical sensor) can be located upstream of the nip  224  to sense the arrival of the medium  275  at the nip  224 . The sensor  280  can be connected to the controller  250 , as shown. By sensing the arrival time of medium  275  at the nip  224 , power can be supplied from the power supply  240  to the heater  230  to heat the outer surface  212  of the fuser belt  210  to the desired temperature before the medium  275  arrives at the nip  224 . In embodiments, once medium  275  has passed through the nip  224 , the supply of power to the heater  230  by the power supply  240  can be turned OFF until the sensor  280  senses the arrival of the next medium at nip  224 . 
     Although the above description is directed toward fusers used in xerographic printing, it will be understood that the teachings and claims herein can be applied to any treatment of marking material on a medium in apparatuses useful for printing. For example, the marking material can be toner, liquid or gel ink, and/or heat- or radiation-curable ink; and/or the medium can utilize certain process conditions, such as temperature, for successful printing. The process conditions, such as heat, pressure and other conditions that are desired for the treatment of ink on media in a given embodiment may be different from the conditions suitable for xerographic fusing. 
     It will be appreciated that various ones of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, 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.