Patent Application
20110243623
This invention pertains to the field of electrophotographic printing and more particularly to fusing toner to a receiver to produce a specified surface finish.
Electrophotography is a useful process for printing images on a receiver (or “imaging substrate”), such as a piece or sheet of paper or another planar medium, glass, fabric, metal, or other objects as will be described below. In this process, an electrostatic latent image is formed on a photoreceptor by uniformly charging the photoreceptor and then discharging selected areas of the uniform charge to yield an electrostatic charge pattern corresponding to the desired image (a “latent image”).
After the latent image is formed, toner particles are given a charge substantially opposite to the charge of the latent image, and brought into the vicinity of the photoreceptor so as to be attracted to the latent image to develop the latent image into a visible image. Note that the visible image may not be visible to the naked eye depending on the composition of the toner particles (e.g. clear toner).
After the latent image is developed into a visible image on the photoreceptor, a suitable receiver is brought into juxtaposition with the visible image. A suitable electric field is applied to transfer the toner particles of the visible image to the receiver to form the desired print image on the receiver. The imaging process is typically repeated many times with reusable photoreceptors.
The receiver is then removed from its operative association with the photoreceptor and subjected to heat or pressure to permanently fix (“fuse”) the print image to the receiver. Plural print images, e.g. of separations of different colors, are overlaid on one receiver before fusing to form a multi-color print image on the receiver.
Electrophotographic (EP) printers typically transport the receiver past the photoreceptor to form the print image. The direction of travel of the receiver is referred to as the slow-scan or process direction. This is typically the vertical (Y) direction of a portrait-oriented receiver. The direction perpendicular to the slow-scan direction is referred to as the fast-scan or cross-process direction, and is typically the horizontal (X) direction of a portrait-oriented receiver. “Scan” does not imply that any components are moving or scanning across the receiver; the terminology is conventional in the art.
Users require a variety of different surface finishes on prints. For example, a matte finish is typically preferred for black-and-white images, such as text documents, and a glossy finish is preferred for full-color images, such as photographs.
U.S. Pat. No. 5,887,234 to Aslam et al. describes a printer having a first fusing device for producing a low-gloss finish and a second printing device for producing a high-gloss finish. These two fusing devices are separate and do not share components.
U.S. Pat. No. 5,716,750 to Tyagi et al. describes a fixing apparatus for post-treating fused toner to relax residual stress in the toner and adjust the gloss of the finish. Post-treatment methods include reheating and applying a chemical plasticizer to the fused toner. This approach requires additional components, and in some embodiments chemical components, compared to fusing alone.
The approaches of the prior art require additional components and space to selectively provide surface finishes. There is a need, therefore, for an improved method for fusing or glossing toner on a receiver in a space-limited printer.
According to the present invention, there is provided a method of forming a variable finish on a receiver by fusing toner to the receiver in an electrophotographic printer, comprising:
providing a rotatable member, a fusing system disposed with respect to the rotatable member to form a fusing nip, and a glossing system having a glossing belt and disposed with respect to the rotatable member to form a glossing nip, wherein the fusing system and glossing system are adapted to fuse toner to the receiver to produce respective ranges of finish of the fused toner;
selecting a finish within one of the respective ranges, and selecting one of the nips, wherein the finish range of the system corresponding to the selected nip includes the selected finish; and
rotating the rotatable member to feed the receiver through the selected nip to fuse the toner to the receiver and form the selected finish on the receiver.
An advantage of this method is that it reduces the space required to provide selectable surface finishes, and specifically to provide either a fused (matte) finish or a glossed (glossy) finish. Compared to prior art systems with four rollers (two to fuse and two to gloss), the present invention requires only three rollers to perform the same function. By disposing the fusing and glossing systems with respect to a common rotatable member, the space between the fusing and glossing systems is reduced. This advantageously reduces the complexity of the receiver feed path, and can increase throughput. Various embodiments of the invention provide improved release and heat transfer for glossing using a finishing belt. Various embodiments provide adjustable gloss based on temperature, speed, and pressure. Various embodiments provide stable, repeatable gloss over a large operating range of temperature, speed, and pressure. Various embodiments can increase durability and reduce artifacts caused by receivers' damaging the components of the toner-heating apparatus. In various embodiments, the finishing belt advantageously provides a replaceable surface for the impression member of the glossing nip, reducing replacement costs in the event of damage to that member.
The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein:
The attached drawings are for purposes of illustration and are not necessarily to scale.
As used herein, the terms “parallel” and “perpendicular” have a tolerance of ±10°.
As used herein, “toner particles” are particles of one or more material(s) that are transferred by an EP printer to a receiver to produce a desired effect or structure (e.g. a print image, texture, pattern, or coating) on the receiver. Toner particles can be ground from larger solids, or chemically prepared (e.g. precipitated from a solution of a pigment and a dispersant using an organic solvent), as is known in the art. Toner particles can have a range of diameters, e.g. less than 8 μm, on the order of 10-15 μm, up to approximately 30 μm, or larger (“diameter” refers to the volume-weighted median diameter, as determined by a device such as a Coulter Multisizer).
“Toner” refers to a material or mixture that contains toner particles and that can form an image, pattern, or coating when deposited on an imaging member including a photoreceptor, photoconductor, or electrostatically-charged or magnetic surface. Toner can be transferred from the imaging member to a receiver. Toner is also referred to in the art as marking particles, dry ink, or developer, but note that herein “developer” is used differently, as described below. Toner can be a dry mixture of particles or a suspension of particles in a liquid toner base.
Toner includes toner particles and can include other particles. Any of the particles in toner can be of various types and have various properties. Such properties can include absorption of incident electromagnetic radiation (e.g. particles containing colorants such as dyes or pigments), absorption of moisture or gasses (e.g. desiccants or getters), suppression of bacterial growth (e.g. biocides, particularly useful in liquid-toner systems), adhesion to the receiver (e.g. binders), electrical conductivity or low magnetic reluctance (e.g. metal particles), electrical resistivity, texture, gloss, magnetic remnance, florescence, resistance to etchants, and other properties of additives known in the art.
In single-component or monocomponent development systems, “developer” refers to toner alone. In these systems, none, some, or all of the particles in the toner can themselves be magnetic. However, developer in a monocomponent system does not include magnetic carrier particles. In dual-component, two-component, or multi-component development systems, “developer” refers to a mixture of toner and magnetic carrier particles, which can be electrically-conductive or -non-conductive. Toner particles can be magnetic or non-magnetic. The carrier particles can be larger than the toner particles, e.g. 20-300 μm in diameter. A magnetic field is used to move the developer in these systems by exerting a force on the magnetic carrier particles. The developer is moved into proximity with an imaging member or transfer member by the magnetic field, and the toner or toner particles in the developer are transferred from the developer to the member by an electric field, as will be described further below. The magnetic carrier particles are not intentionally deposited on the member by action of the electric field; only the toner is intentionally deposited. However, magnetic carrier particles, and other particles in the toner or developer, can be unintentionally transferred to an imaging member. Developer can include other additives known in the art, such as those listed above for toner. Toner and carrier particles can be substantially spherical or non-spherical.
The electrophotographic process can be embodied in devices including printers, copiers, scanners, and facsimiles, and analog or digital devices, all of which are referred to herein as “printers.” Various aspects of the present invention are useful with electrostatographic printers such as electrophotographic printers that employ toner developed on an electrophotographic receiver, and ionographic printers and copiers that do not rely upon an electrophotographic receiver. Electrophotography and ionography are types of electrostatography, printing using electrostatic fields, which is a subset of electrography, printing using electric fields.
A digital reproduction printing system (“printer”) typically includes a digital front-end processor (DFE), a print engine (also referred to in the art as a “marking engine”) for applying toner to the receiver, and one or more post-printing finishing system(s) (e.g. a UV coating system, a glosser system, or a laminator system). A printer can reproduce original pleasing black-and-white or color onto a receiver. A printer can also produce selected patterns of toner on a receiver, which patterns (e.g. surface textures) do not correspond directly to a visible image. The DFE receives input electronic files (such as Postscript command files) composed of images from other input devices (e.g., a scanner, a digital camera). The DFE can include various function processors, e.g. a raster image processor (RIP), image positioning processor, image manipulation processor, color processor, or image storage processor. The DFE rasterizes input electronic files into image bitmaps for the print engine to print. In some embodiments, the DFE permits a human operator to set up parameters such as layout, font, color, paper type, or post-finishing options. The print engine takes the rasterized image bitmap from the DFE and renders the bitmap into a form that can control the printing process from the exposure device to transferring the print image onto the receiver. The finishing system applies features such as protection, glossing, or binding to the prints. The finishing system can be implemented as an integral component of a printer, or as a separate machine through which prints are fed after they are printed.
The printer can also include a color management system which captures the characteristics of the image printing process implemented in the print engine (e.g. the electrophotographic process) to provide known, consistent color reproduction characteristics. The color management system can also provide known color reproduction for different inputs (e.g. digital camera images or film images).
In an embodiment of an electrophotographic modular printing machine useful with the present invention, e.g. the NEXPRESS 2100 printer manufactured by Eastman Kodak Company of Rochester, N.Y., color-toner print images are made sequentially in a plurality of color imaging modules arranged in tandem, and the print images are successively electrostatically transferred to a receiver adhered to a transport web moving through the modules. Colored toners include colorants, e.g. dyes or pigments, which absorb specific wavelengths of visible light. Commercial machines of this type typically employ intermediate transfer members in the respective modules for the transfer to the receiver of individual print images. Of course, in other electrophotographic printers, each print image is directly transferred to a receiver.
Electrophotographic printers having the capability to also deposit clear toner using an additional imaging module are also known. The provision of a clear-toner overcoat to a color print is desirable for providing protection of the print from fingerprints and reducing certain visual artifacts. Clear toner uses particles that are similar to the toner particles of the color development stations but without colored material (e.g. dye or pigment) incorporated into the toner particles. However, a clear-toner overcoat can add cost and reduce color gamut of the print; thus, it is desirable to provide for operator/user selection to determine whether or not a clear-toner overcoat will be applied to the entire print. A uniform layer of clear toner can be provided. A layer that varies inversely according to heights of the toner stacks can also be used to establish level toner stack heights. The respective color toners are deposited one upon the other at respective locations on the receiver and the height of a respective color toner stack is the sum of the toner heights of each respective color. Uniform stack height provides the print with a more even or uniform gloss.
Referring to
Each receiver, during a single pass through the five modules, can have transferred in registration thereto up to five single-color toner images to form a pentachrome image. As used herein, the term “pentachrome” implies that in a print image, combinations of various of the five colors are combined to form other colors on the receiver at various locations on the receiver, and that all five colors participate to form process colors in at least some of the subsets. That is, each of the five colors of toner can be combined with toner of one or more of the other colors at a particular location on the receiver to form a color different than the colors of the toners combined at that location. In an embodiment, printing module 31 forms black (K) print images, 32 forms yellow (Y) print images, 33 forms magenta (M) print images, and 34 forms cyan (C) print images.
Printing module 35 can form a red, blue, green, or other fifth print image, including an image formed from a clear toner (i.e. one lacking pigment). The four subtractive primary colors, cyan, magenta, yellow, and black, can be combined in various combinations of subsets thereof to form a representative spectrum of colors. The color gamut or range of a printer is dependent upon the materials used and process used for forming the colors. The fifth color can therefore be added to improve the color gamut. In addition to adding to the color gamut, the fifth color can also be a specialty color toner or spot color, such as for making proprietary logos or colors that cannot be produced with only CMYK colors (e.g. metallic, fluorescent, or pearlescent colors), or a clear toner.
Subsequent to transfer of the respective print images, overlaid in registration, one from each of the respective printing modules 31, 32, 33, 34, 35, the receiver is advanced to a fuser 60, i.e. a fusing or fixing assembly, to fuse the print image to the receiver. Transport web 101 transports the print-image-carrying receivers to fuser 60, which fixes the toner particles to the respective receivers by the application of heat and pressure. The receivers are serially de-tacked from transport web 101 to permit them to feed cleanly into fuser 60. Transport web 101 is then reconditioned for reuse at cleaning station 106 by cleaning and neutralizing the charges on the opposed surfaces of the transport web 101.
Fuser 60 includes a heated fusing roller 62 and an opposing pressure roller 64 that form a fusing nip 66 therebetween. Fuser 60 also includes a release fluid application substation 68 that applies release fluid, e.g. silicone oil, to fusing roller 62. Other embodiments of fusers, both contact and non-contact, can be employed with the present invention. For example, solvent fixing uses solvents to soften the toner particles so they bond with the receiver. Photoflash fusing uses short bursts of high-frequency electromagnetic radiation (e.g. ultraviolet light) to melt the toner. Radiant fixing uses lower-frequency electromagnetic radiation (e.g. infrared light) to more slowly melt the toner. Microwave fixing uses electromagnetic radiation in the microwave range to heat the receivers (primarily), thereby causing the toner particles to melt by heat conduction, so that the toner is fixed to the receiver.
The receivers carrying the fused image are transported in a series from the fuser 60 along a path either to a remote output tray 69, or back to printing modules 31 et seq. to create an image on the backside of the receiver, i.e. to form a duplex print. Receivers can also be transported to any suitable output accessory. For example, an auxiliary fuser or glossing assembly can provide a clear-toner overcoat. Printer 100 can also include multiple fusers 60 to support applications such as overprinting, as known in the art.
Printer 100 includes main printer apparatus logic and control unit (LCU) 99, which receives input signals from the various sensors associated with printer 100 and sends control signals to the components of printer 100. The LCU can include a microprocessor incorporating suitable look-up tables and control software executable by the LCU 99. It can also include a field-programmable gate array (FPGA), programmable logic device (PLD), microcontroller, or other digital control system. The LCU can include memory for storing control software and data. Sensors associated with the fusing assembly provide appropriate signals to the LCU 99. In response to the sensors, the LCU 99 issues command and control signals that adjust the heat or pressure within fusing nip 66 and other operating parameters of fuser 60 for imaging substrates. This permits printer 100 to print on receivers of various thicknesses and surface finishes, such as glossy or matte. Image data for writing by printer 100 can be processed by a raster image processor (RIP; not shown), which can include a color separation screen generator or generators. The output of the RIP can be stored in frame or line buffers for transmission of the color separation print data to each of respective LED writers, e.g. for black (K), yellow (Y), magenta (M), cyan (C), and red (R) respectively. The RIP or color separation screen generator can be a part of printer 100 or remote therefrom. Image data processed by the RIP can be obtained from a color document scanner or a digital camera or produced by a computer or from a memory or network which typically includes image data representing a continuous image that needs to be reprocessed into halftone image data in order to be adequately represented by the printer. The RIP can perform image processing processes, e.g. color correction, in order to obtain the desired color print. Color image data is separated into the respective colors and converted by the RIP to halftone dot image data in the respective color using matrices, which comprise desired screen angles (measured counterclockwise from rightward, the +X direction) and screen rulings. The RIP can be a suitably-programmed computer or logic device and is adapted to employ stored or computed matrices and templates for processing separated color image data into rendered image data in the form of halftone information suitable for printing. These matrices can include a screen pattern memory (SPM).
Further details regarding printer 100 are provided in U.S. Pat. No. 6,608,641, issued on Aug. 19, 2003, by Peter S. Alexandrovich et al., and in U.S. Publication No. 2006/0133870, published on Jun. 22, 2006, by Yee S. Ng et al., the disclosures of which are incorporated herein by reference.
One of the rotatable members forming each nip is an impression member adapted to provide a desired surface finish to image side 43 of receiver 42, and the other rotatable member forming each nip is a pressure member adapted to maintain the receiver in contact with the impression member while the receiver travels through the respective nip. “In contact” does not require complete mechanical contact at all times; voids can be present between the two due to e.g. imperfections in the rotatable members or wrinkles, holes or roughness in receiver 42. “Impression” does not require that the roller have any kind of pattern or texture, or print or press any image, pattern, or texture onto receiver 42. In this embodiment, first nip 211 has as its impression member central rotatable member 203, and as its pressure member first rotatable member 201. Second nip 211 has as its impression member second rotatable member 202, and as its pressure member central rotatable member 203.
Finishing belt 220 is entrained around one of the rotatable members, here central rotatable member 203, and movable with that member, so that the finishing belt passes through one or both of the nips. Finishing belt 220 is further entrained around tensioning roller 225 to maintain tension.
Diverter 230 is disposed in receiver feed path 242 to selectively engage the moving receiver 42 in a first position 231 or a second position 232, so that as receiver 42 moves along feed path 242 through diverter 230 in the first position 231, it engages first nip 211, and as receiver 42 moves along feed path 242 through diverter 230 in second position 232, it engages second nip 212.
Diverter 230 is a sliding member that contacts receiver 42 on one of its two concave faces to direct receiver 42 to one of the nips (211, 212). In another embodiment, diverter 230 is a hinged plate controlled by a solenoid. The plate can have a lip to grip receiver 42 and direct it to the nip at which the plate is pointing.
Apparatus 200 includes a structure for providing the selected surface finish. The structure includes drive 255, first heater 251, and second heater 252. Drive 255 selectively rotates central rotatable member 203 to draw receiver 42 through the engaged nip (211 or 212), i.e. the selected nip through which receiver 42 is drawn. For first nip 211, central rotatable member 203 rotates clockwise; for second nip 211, it rotates counterclockwise. First heater 251 (represented graphically as a four-pointed star) is effective when diverter 230 is in the first position to heat the impression member (central rotatable member 203) of first nip 211 to impart the first surface finish. First heater 251 can be active while receiver 42 passes through first nip 211, before receiver 42 reaches first nip 211, or both. The heating profile for first heater 251 can be selected by those skilled in the art to provide the desired surface finish.
Second heater 252 is effective when diverter 230 is in second position 232 for heating the impression member (second rotatable member 202) of the second nip 212 to impart the second surface finish. As with the first heater 251, second heater 252 can be active at various times, as can be determined by one skilled in the art. First heater 251 and second heater 252 can be positioned inside the rotating members, as shown, or outside the rotating members to directly heat the surface that contacts the receiver.
Drive 255 can be a servomotor, stepper motor, linear actuator driving a crankshaft, or other types of drive known in the art. First heater 251 and second heater 252 can be resistive, inductive, radiant, thermoelectric, combustion, convective, conductive, or other types of heaters known in the art.
As shown in
Rotating members 201, 202, and 203 can be formed of metals such as steel, stainless steel, or aluminum. Rotating members that are not heated (e.g. first rotating member 201 in
Elastomer 204 can be of various formulations. Moreover, elastomer 204 can include a base cushion around or adjacent to the corresponding rotating member, and a topcoat around the base cushion. On the pressure roller of one of the nips, lower-thermal-conductivity elastomers such as EMERSON CUMING 55100 can be employed. Topcoats are useful to lower the surface energy; the topcoat can include fluoroplastics including PFA (perfluoroalkoxy), PTFE (polytetrafluoroethylene), and PFE (polyfluoroethylene). On the impression member of one of the nips, a thermally conductive base cushion material is preferably used. An example is EMERSON CUMING EC4952. Thermally-conductive base cushions are particularly useful with internally-heated impression members, such as shown in
Elastomer 204 has lower thermal conductivity than rotating members 201, 202, and 203, and therefore heats and cools more slowly. In various embodiments, one of the rotating members 201, 202, 203 serves as an impression member at some times and as a pressure member at other times; this is referred to herein as the “multifunctional member.” In
In an embodiment, heat energy is transferred back and forth between the impression member of the fusing nip (here, second rotating member 202) and the impression member of the glossing nip (here, central rotating member 203). Receiver 42 passes through only one nip at a time. The impression member of the selected nip has a higher temperature than the pressure member of the selected nip. This is particularly important for duplex operations, in which already-fused toner should not be damaged or re-fused. Moreover, elevated pressure-member temperatures promote paper blistering in coated media.
In this embodiment, after receiver 42 exits second nip 212, second rotating member 202 is hotter than central rotating member 203. When the next receiver 42 is to be fused in first nip 211, central rotating member 203 and second rotating member 202 are retained in mechanical contact with each other so that heat is transferred from second rotating member 202 to central rotating member 203. Second rotating member 202 and central rotating member 203 can be rotated to transfer heat over an increased percentage of the members' surfaces.
In an embodiment, finishing belt 220 is field-replaceable. Replacing finishing belt 220 has an effect similar to that of replacing the outer sleeve of the rotating member around which finishing belt 220 is entrained, which capability is not present in prior-art systems. Replacement of finishing belt 220 does not require replacement of any cores or bearings. In embodiments using lightweight belts (e.g. polyimide), shipment and storage requirements are much less than those requirements for replacement of rotating members.
Thin, hard materials in finishing belt 220 are typically more durable than elastomers or elastomer-coated materials. For example, perfluoroalkoxy (PFA) copolymer resins, such as DUPONT TEFLON PFA, can be used for a rotating-member sleeve. However, PFA-sleeved rollers applied to elastomer-coated cores can be damaged by paper edges, both in-track and cross-track. The softer of the two contacting surfaces gets the most damage. This damage can cause wear artifacts visible in high-quality prints. The relatively hard surface of finishing belt 220 reduces the probability of this type of damage and permits effective cold release (i.e. release of toner at a temperature below Tg from finishing belt 220). The advantageously reduces artifacts in the high-gloss output of printer 100 (
“Surface finish” refers to the general appearance of a printed image or document, independent of the content of that image. It includes texture, gloss, and other factors known in the art. Gloss refers to the reflectivity of the surface of the image under specular illumination. Gloss can be measured at various angles, and is reported in Gnn units, where nn is the angle off the normal from which test light is shone and at which the measurement is taken (incident angle=reflected angle). Gnn values are nonnegative numbers, where Gnn=100 is the reflectance of a gloss calibration standard (see ASTM standard D2457 for more details).
Below temperature 1110, toner 43 (
Above temperature 1110, the glossing nip (belt fusing) produces a glossy surface finish on receiver 42. Curve 1122 shows the G20 values for this condition. However, the preferable G20 range described above is not reached until temperature 1120 (“OK glossy”). In this example, the preferable range is therefore achieved by temperatures from 140-190° C.
First nip 211 is a fusing nip having the central rotatable member 203 as its impression member. Second nip 212 is a glossing nip having second rotatable member 202 as its impression member. First heater 251 is effective to heat central rotatable member 203, and second heater 252 is effective to heat second rotatable member 202, as described above.
First nip 211 is a fusing nip having first rotatable member 201 as its impression member. Second nip 212 is a glossing nip having second rotatable member 202 as its impression member.
First heater 251 is effective when diverter 230 is in the first position to heat the impression member (first rotatable member 201) of first nip 211 to impart the first surface finish (a fused, e.g. matte, finish). Second heater 252 is effective when diverter 230 is in second position 232 for heating the impression member (second rotatable member 202) of the second nip 212 to impart the second surface finish (e.g. a glossy finish). First heater 251 and second heater 252 can be active at various times, as can be determined by one skilled in the art.
In an embodiment, apparatus 200 includes inverter 496 (represented graphically as a rotating cylinder) adapted to selectively flip receiver 42 as it moves along feed path 242 (
In this example, receiver 42 enters inverter 496 with image side 43 facing to the right. When diverter 230 is in first position 231, inverter 496 flips receiver 42 before receiver 42 enters first nip 211. Receiver 42A is shown after flipping, with its image side 43A facing to the left. Image side 43A therefore faces first rotatable member 201, which member is the impression member of first nip 211.
When diverter 230 is in second position 232, inverter 496 does not flip receiver 42 before receiver 42 enters second nip 212. Receiver 42B is shown after passing through diverter 496, with its image side 43B still facing to the right. Image side 43B therefore faces second rotatable member 202, which member is the impression member of second nip 212.
Apparatus 200 includes controller 510, temperature probe 520 for measuring a surface temperature of the pressure member of a selected one of the nips, and cooling unit 530 (represented graphically as a box with a snowflake). In response to a measured surface temperature above a selected limit, controller 510 causes cooling unit 530 to cool the pressure member of the selected nip before the receiver is guided into the selected nip. In this example, the selected nip is second nip 212, and receiver 42 is shown about to enter second nip 212.
When a receiver is fused in first nip 211, central rotatable member 203 is heated by first heater 251. When the subsequent receiver 42 is to be fused in second nip 211, central rotatable member 203 changes function from the impression member (of first nip 211) to the pressure member (of second nip 212). For fusing or glossing in either nip, the pressure member is preferably cooler than the impression member, e.g. at room temperature. This reduces the likelihood of overheating and damaging receiver 42. In duplex systems, it also advantageously reduces re-melting and smearing of the image on the back side 543 of receiver 42.
To achieve these advantages, controller 510 causes cooling unit 530 to activate in order to remove excess heat from central rotatable member 203 before passing receiver 42 through second nip 212.
One of the rotatable members is not an impression member of either nip. In
Apparatus 200 disengages the nip other than the engaged nip while the receiver is drawn through the engaged nip. In this example, diverter 230 is in first position 231 so receiver 42 will be engaged in and drawn through first nip 211. First rotatable member 201 and second rotatable member 202 ride on rails 721, 722 respectively, driven by respective actuators 711, 712. Second rotatable member 202 is drawn out of engagement with central rotatable member 203, thus disengaging second nip 212 while receiver 42 is drawn through first nip 211. This advantageously reduces wear on, and undesired heat transfer to, second rotatable member 202 while it is idle. It also reduces the rolling friction on central rotatable member 203, and thus reduces the energy consumed in driving central rotatable member 203. Actuators 711, 712 can be linear actuators, or servomotors or stepper motors driving chains or belts. Other embodiments of motors and actuators known in the art can also be used.
In another embodiment, first rotatable member 201 and second rotatable member 202 are mounted on pendulums or other shafts rotated by motors to disengage nips.
In another embodiment, first rotatable member 201 and second rotatable member 202 move vertically or longitudinally (the two directions perpendicular to the lateral axis of rails 721, 722) to disengage the nips.
In another embodiment, first rotatable member 201 and second rotatable member 202 are fixed in position, and central rotatable member 203 is moved by an actuator back and forth between them to engage one nip at a time.
The pressure member of at least one nip has higher surface hardness than the impression member. For example, surface 835 of the pressure member (central rotatable member 203) of second nip 212 is harder than surface 825 of the impression member (second rotatable member 202) of second nip 212. The fusing nip preferably has this property, but both nips can have this property.
“Hardness” or “durometer” refers to the deformation of a surface under known test conditions (e.g. applied force and shape of a test pin pressed into the surface). A first surface is harder than a second surface if the same test conditions produce greater surface deformation on the second surface than the first. Shore A is a commonly-used hardness scale. Elastomers generally have Shore A hardnesses from 20-70; steel measures over 90. Hard rollers can have thin elastomer coatings. The rotatable members can be covered with an elastomeric base cushion with a harder material, e.g. a metal, coated on top; the hardness of the surface then also depends on the thickness and hardness of the base cushion.
This difference in surface hardness improves the release geometry of a fusing nip, e.g. second nip 212, compared to a nip having rollers of equal surface hardnesses. Toner in contact with a heated impression member is in a molten or semi-molten state, and therefore adheres to the surface of the impression member through surface tension. For rollers of equal surface hardnesses, there is little force to counteract this adhesion and separate receiver 42 cleanly from the surface of the impression member. However, separation is necessary for normal operation of printer 100 (
Rollers of different surface hardnesses, by contrast, give rise to forces due to their geometries that cleanly release receiver 42 from the impression member. When a harder and a softer roller are pressed together, the harder makes an indentation in the surface of the softer. For example, central rotating member 203 (the pressure member) makes an indentation in the elastomer over second rotating member 202 (the impression member). Receiver 42 therefore takes the path shown, conforming to the surface of central rotating member 203 through the indentation. At release point 840, receiver 42 is pointing in direction 842. The stiffness of receiver 42 (however much or little it has) develops a force which opposes attempts to change the direction of receiver 42 away from direction 842. The adhesion of receiver 42 to second rotating member 202 develops a force which attempts to pull receiver 42 in direction 844. One skilled in the art can select direction 842 for a given stiffness of receiver 42 so that the force in direction 842 will overcome the adhesion force in direction 844, and receiver 42 will release (separate or de-tack) from the surface of second rotating member 202.
In step 910, a rotatable member is provided (e.g. central rotatable member 203). A fusing system is provided (e.g. second rotatable member 202 and second heater 252) disposed with respect to the rotatable member to form a fusing nip (e.g. second nip 212). A glossing system is provided (e.g. first rotatable member 201, first heater 251, finishing belt 220, and tensioning roller 225) having a glossing belt (e.g. finishing belt 220). The glossing system is disposed with respect to the rotatable member to form a glossing nip (e.g. first nip 211). The fusing system and glossing system are adapted to fuse toner 44 to receiver 42 to produce respective ranges of finish of the fused toner 44. Ranges of finish are discussed further above with reference to
The ranges of finish of the fusing system and glossing system preferably do not overlap, as discussed above. For example, the fusing system can have a range of finish of G60=4-70, which can correspond to G20=0-20 (see
In step 920, a surface finish is selected within one of the respective ranges (i.e. the ranges of the fusing system and the glossing system). One of the nips is selected so that the finish range of the system corresponding to the selected nip includes the selected finish.
In optional step 925, a diverter 230 is provided disposed in receiver feed path 242 to selectively engage the moving receiver 42 in a first position 231 or a second position 232, so that as receiver 42 moves along feed path 242 through diverter 230 in first position 231, it engages the glossing nip (or the fusing nip), and as the receiver moves along the feed path through the diverter in the second position, it engages the fusing nip (or the glossing nip). The orientation of the diverter can be selected by those skilled in the art. Receiver 42 is diverted to engage with the selected nip.
In step 930, the rotatable member is rotated to feed receiver 42 through the selected nip to fuse toner 44 to receiver 42 and form the selected finish on the receiver.
In an embodiment, the rotatable member feeds the receiver through the selected nip at a first speed when the fusing system is selected, and at a second speed different from the first speed when the glossing system is selected.
In various embodiments, first rotatable member (e.g. second rotatable member 202) is provided in the fusing system and a second rotatable member (e.g. first rotatable member 201) is provided in the glossing system, so that one of the rotatable members forming each nip (i.e. one of the rollers in the fusing or glossing system, or the rotatable member with respect to which the fusing and glossing systems are disposed) is an impression member adapted to provide the selected finish to the image side of the receiver. This is discussed above with reference to
In optional step 940, the impression member of the selected nip is heated to a temperature corresponding to the selected finish while the receiver is fed through the selected nip.
In optional step 950, the pressure member of the selected nip contacts the impression member of the selected nip with a pressure corresponding to the selected finish while the receiver passes through the selected nip.
The invention is inclusive of combinations of the embodiments described herein. References to “a particular embodiment” and the like refer to features that are present in at least one embodiment of the invention. Separate references to “an embodiment” or “particular embodiments” or the like do not necessarily refer to the same embodiment or embodiments; however, such embodiments are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. The use of singular or plural in referring to the “method” or “methods” and the like is not limiting. The word “or” is used in this disclosure in a non-exclusive sense, unless otherwise explicitly noted.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations, combinations, and modifications can be effected by a person of ordinary skill in the art within the spirit and scope of the invention.
Reference is made to commonly assigned, co-pending U.S. patent application Ser. No. 12/491,320, filed Jun. 25, 2009, entitled “FUSING APPARATUS FOR HIGH SPEED ELECTROPHOTOGRAPHY SYSTEM,” by Muhanuned Aslam et al.; co-pending U.S. patent application Ser. No. 12/507,823, filed Jul. 23, 2009, entitled “OPTIMIZED FUSING FOR HIGH SPEED ELECTROPHOTOGRAPHY SYSTEM,” by Richard H. Berg et al.; and U.S. patent application Ser. No. ______, (Docket 96087) filed concurrently herewith, entitled “TONER HEATING APPARATUS WITH BELT AND NIP,” by Robert D. Bobo et al; the disclosures of which are incorporated by reference herein.
