Development system having developer belt

Abstract

To provide a replaceable development system capable of being used at a plurality of positions with respect to a photoconductive surface.SOLUTION: A development system 12A includes a developer housing 30 configured to contain a developer material including toner particles. Two magnetic rollers 32, 34 are disposed in the housing 30 to attract the developer material to a surface of the magnetic rollers 32, 34. A developer belt 14A is supported by developer rollers 18, 20, and 22. The developer belt 14A attracts the toner particles from the two magnetic rollers 32, 34 to a surface of the developer belt 14A. The developer roller 22 is positioned adjacent to an image transfer member 16 such as a belt or a drum having a photoconductive surface. Part of the toner particles are transferred to a latent image formed on the image transfer member 16 to produce a toner image layer, which is applied to a print media sheet.SELECTED DRAWING: Figure 2

Description

BACKGROUND ART

[0001] Exemplary embodiments relate to electrophotographic printing and find particular use in connection with a development system having a variable length development belt.

[0002] The process of electrophotographic printing generally includes charging the surface of a photoconductive member, such as a belt or drum, to a substantially uniform potential to sensitize the surface. The charged portion of the photoconductive surface is exposed to an optical image from either a scanning laser beam, an LED light source, or an original document being reproduced. Thereby, an electrostatic latent image is recorded on the photoconductive surface. After the electrostatic latent image is recorded on the photoconductive surface, the latent image is developed. Two-component developer materials and one-component developer materials are commonly used for development. A typical two-component developer includes magnetic carrier particles having triboelectrically charged toner particles adhering thereto. One-component developer materials typically include toner particles. The toner particles are attracted to the latent image to form a toner powder image on the photoconductive surface. The toner powder image is then transferred to a print media sheet either directly or via an intermediate transfer member. Finally, the toner powder image is heated to more permanently fix it to the print media sheet in an image configuration.

[0003] In many development systems, a magnetic roller (“magroll”) is used to transfer toner particles from a developer housing to the photoconductive surface. To enable a number of development systems to be arranged around a photoconductive member or an intermediate transfer member, each development system is configured to be slightly different such that the magroll can contact the photoconductive member. Thus, the development systems are not interchangeable. Additionally, the replacement of toner containers is not always easy because they are not aligned with each other. These factors tend to increase the downtime of the printing apparatus and increase the cost of the printing apparatus.

[0004] There is still a need for an interchangeable development system that can be used at multiple positions with respect to the photoconductive surface.

[0005] Built-in by reference The following references (their disclosures are incorporated in their entirety herein by reference) are mentioned: U.S. Patent No. 8,005,410(B2) issued by Wu on August 2, 2011, entitled "POLYIMIDE INTERMEDIATE TRANSFER COMPONENTS," describes intermediate transfer belts containing thermosetting polyimide.

[0006] U.S. Patent Application Publication No. 2020 / 0356029(A1) by Takei et al., titled "BELT, INTERMEDIATE TRANSFER BELT, AND IMAGE FORMING APPARATUS," published on November 12, 2020, describes a belt containing a polyimide resin having carbon black particles in its outer layer.

[0007] U.S. Patent Application Publication No. 2004 / 0114969(A1) by Manno, titled “DEVELOPMENT SYSTEM,” published on June 17, 2004, describes a developing system comprising a magnetic developing roll including a rotatable sleeve in which a rotatable magnetic core is disposed, and a developing material delivery system for providing metered dispensing of developing material to the rotatable sleeve. [Overview of the project]

[0008] According to one aspect of an exemplary embodiment, the developing system includes a housing configured to contain a developer material containing toner particles. At least one magnetic roller within the housing attracts the developer material to its surface. A continuous developer belt attracts the toner particles from at least one magnetic roller to the surface of the developer belt. Multiple developer rollers transport the developer belt around them. One of the rollers is positioned adjacent to a related image transfer member, thereby transferring some of the toner particles to a latent image formed on the image transfer member.

[0009] According to another aspect of the exemplary embodiment, the marking apparatus comprises the plurality of developing systems described above.

[0010] According to another aspect of the exemplary embodiment, the printer comprises the marking device described above and a sheet transport system that transports the associated printing medium sheet through the marking device to receive a toner image layer from an image transfer member.

[0011] According to another aspect of the exemplary embodiment, the printing method includes preparing a first developer material in a first housing, wherein the first developer material comprises first toner particles; transferring a portion of the first toner particles to a first continuous developer belt; developing a first latent image on a first image transfer member using the transferred portion of the toner particles to form a first toner image layer; and transferring the first toner image layer to a printing medium sheet.

[0012] According to another aspect of an exemplary embodiment, the printer comprises a print medium source and a marking device that receives a print medium from the print medium source and imparts a toner image to the print medium. The marking device comprises an image transport member, at least one charging station for charging a photoconductive surface of the image transport member, an exposure station for forming a latent image on the charged photoconductive surface, at least one developing system, and a sheet transport system for transporting a sheet of print medium from the print medium source to the marking device to receive a toner image layer from an image transfer member. Each developing system includes a housing configured to contain a developer material containing toner particles and a continuous developer belt for transporting the toner particles from the housing to the surface of an image transfer member to develop a latent image on the image transfer member and form a toner image. [Brief explanation of the drawing]

[0013] [Figure 1] This is a functional block diagram of a printer equipped with a marking device, according to one embodiment of an exemplary design. [Figure 2]This is a side cross-sectional view of a developing system having a developing belt suitable for use in the marking device shown in Figure 1. [Figure 3] This is a side cross-sectional view of a marking device incorporating a set of developing systems and a belt-type image transfer member, according to another embodiment of the exemplary model. [Figure 4] This is a side cross-sectional view of a marking apparatus incorporating a set of developing systems and drum-type image transfer members, according to another embodiment of an exemplary design. [Figure 5] This is a side cross-sectional view of a marking apparatus incorporating a set of developing systems and a set of drum-type image transfer members, according to another embodiment of the exemplary model. [Figure 6] This is a side cross-sectional view of a marking device incorporating a set of developing systems and belt-type image transfer members having developer belts of equal length, according to another embodiment of an exemplary model. [Figure 7] This is a perspective view of a drive mechanism for accommodating developer belts of different lengths, according to another aspect of an exemplary embodiment. [Figure 8] This is a perspective view of a drive mechanism for accommodating developer belts of different lengths, according to another aspect of an exemplary embodiment. [Figure 9] This figure shows a printing method according to another aspect of an exemplary embodiment. [Modes for carrying out the invention]

[0014] Exemplary embodiments include a developing system incorporating a developer belt, a marking device incorporating the developing system, and a printing method that can be performed with the system.

[0015] As will be explained in more detail below, the exemplary system helps optimize space utilization, component commonality, and development tolerance in electrophotographic printers.

[0016] In one embodiment, the marking apparatus comprises two or more developing systems.

[0017] In one embodiment, two or more developing systems incorporate developer belts of different lengths.

[0018] In one embodiment, each developer belt receives toner particles from (at least) two magnetic rollers that are in contact with the developer belt or are positioned sufficiently close so that toner particles can pass therebetween.

[0019] In one embodiment, each developer belt transfers toner to a latent image formed on the surface of an image transfer member at a single transfer nip. This can provide flexibility in the positioning of the developing system.

[0020] In one embodiment, the marking device includes at least two identical (general-purpose replaceable) developing systems.

[0021] In one embodiment, the marking device includes at least two developing systems that are mirror images of each other.

[0022] In one embodiment, the marking device includes at least two vertically stacked developing systems.

[0023] In one embodiment, the marking device includes at least two horizontally aligned developing systems.

[0024] In one embodiment, the marking device includes at least eight or at least ten developing systems.

[0025] In one embodiment, the marking device is used in a printing method.

[0026] As used herein, "printing device" or "printer" can include any device for rendering an image on a print medium, such as a copier, laser printer, bookbinding machine, or multifunction device (including one or more additional functions such as scanning, archiving, email, and fax).

[0027] "Print medium" can be a typically thin physical sheet of paper, plastic, or other suitable physical print medium substrate for images. "Print job" or "document" is typically a set of associated sheets, usually a set of original print job sheets from a particular user, or one or more assembled sets of copies reproduced from page images of an electronic document, or other associated sets of sheets.

[0028] A “digital image” can generally include information in electronic form rendered onto a print medium by a printing device, and may include text, graphics, photographs, etc. For example, the act of applying toner images such as graphics, text, and photographs to a print medium is generally referred to herein as printing or marking.

[0029] Referring to Figure 1, an electrophotographic printer 1 for rendering an image onto a print medium is shown. The printer 1 includes a marking device 10 according to one exemplary embodiment. The marking device 10 incorporates one or more developing systems 12A, 12B mounted within / on a common housing / frame 13. Each developing system 12A, 12B is configured to supply toner particles to their respective continuous developer belts 14A, 14B. The developer belts transfer the toner particles to an image transfer member 16, such as a belt or drum, which may have a photoconductive surface. Although two developing systems 12A, 12B are shown in Figure 1, it should be understood that multiple similarly configured developing systems can be arranged to supply toner particles of each color to the same image transfer member 16. Each developing system 12A, 12B, etc., may be similarly configured unless otherwise noted.

[0030] See also Figure 2, in the exemplary developing system 12A, the developer belt 14A is supported by a set of spaced-apart developer rollers 18, 20, 22. Although three developer rollers are shown in the illustrated embodiment, in other embodiments, two developer rollers, more than three developer rollers, or four or fewer spaced-apart developer rollers may be used for each belt 14A. At least one of the rollers 18, 20, 22 is rotated to move the developer belt 14A so that different portions of the outer surface 23 of the belt 14A are in contact with the image transfer member 16. The developer rollers 18, 20, 22 may be driven by a common drive system 24 that moves the belt 14A in the direction of arrow A. At any given time, the first portion 26 of the developer belt 14A is spaced apart by the first and second developer rollers 18, 20, while the third developer roller 22 maintains the second portion 28 of the belt 14A in contact with the image transfer member 16.

[0031] The developer belt 14A may have a length of at least 4 cm, or at least 6 cm, or at least 8 cm, or up to 100 cm, or up to 50 cm, in the continuous direction. The width of the developer belt 14A, perpendicular to its length, may be a function of the width of the image transport member 16 (in the direction across the processing direction), for example, equal to or slightly less than the width of the image transport member 16. The thickness (minimum dimension) of the developer belt 14A may be at least 0.5 mm, or at least 1 mm, or up to 1 cm. Other developer belts 14B, etc., in the marking device 10 may have different lengths, but generally have the same thickness and width.

[0032] The developer rollers 18, 20, and 22 may have the same diameter or different diameters. For example, the roller 22 that contacts the transfer member 16 may have a larger diameter than the other developer rollers 18 and 20, for example, at least 10% larger, at least 20% larger, at least 40% larger, or up to 100% larger. For example, the developer rollers 18 and 20 may each have a diameter of 4 to 12 mm, and the developer roller 22 may have a diameter of 7 to 20 mm.

[0033] The developing system 12A includes a developer housing 30, which holds a certain supply amount of dry developer material, such as magnetic carrier particles having toner particles that are triboelectrically charged and adhere to the surface. The developer belt 14A is partially enclosed within the housing 30. One or more magnetic rollers ("magrolls") 32, 34 (two magrolls in the illustrated embodiment) are mounted within the housing 30. The magrolls may have a larger diameter than the developer rollers 18, 20, 22. Each developing nip 36, 38 is defined between each magroll and the developer belt 14A. In one embodiment, each magroll 32, 34 includes a cylindrical shell or sleeve 40, 42 that is rotatable around a magnetic core 44, 46 containing a set of magnets. Alternatively, the shells 40, 42 are stationary and the cores 44, 46 rotate. The shells may be formed from a conductive non-ferrous material such as aluminum or stainless steel. In other embodiments, a magnetizable brush (not shown) replaces each cylindrical shell. The developer material (including toner particles and magnetic carriers) is attracted to the magnetic rolls 32 and 34 by magnetic force. Next, the toner particles are attracted from the magnetic rolls to the developer belt 14A by the potential difference between the magnetic rolls and the developer belt 14A. Specifically, the toner particles are transferred from the magnetic rolls 32 and 34 to the first portion 24 of the developer belt 14A at the developing nip 36 and 38, while the carrier particles remain in the developing housing 30. The developer belt 14A and the image transfer member 16 define a single transfer nip 50 between them.

[0034] Toner particles are attracted to the image transfer member 16 by the potential difference between the developer belt 14A and the surface 52 of the image transfer member 16. In the illustrated embodiment, the surface 52 is photoconductive, and the toner particles are used to develop the latent image formed on the photoconductive surface 52. In particular, each developing system 12 has an associated charging station 54, such as a charging corotron, for charging the photoconductive surface 52, and an exposure station 56 for forming a latent image on the photoconductive surface. The toner particles are electrostatically attracted to the latent image to form a toner image layer on the surface 52. Residual toner particles not needed to form the toner image layer may be returned to the developer housing 30 on the developer belt 14A for reuse.

[0035] In contrast to the image transfer member 16, the developer belt 14A transports toner particles (a relatively continuous layer of toner particles), but does not transport the toner image layer (a region of toner particles, separated by regions without toner particles, which are regions exposed / unexposed to the image transfer member, respectively) because there is no associated charging station or exposure station 56 for the developer belt 14A.

[0036] Toner particles may be supplied to the housing 30 from a replaceable toner container 58A. Augers 60, 62 within the housing 30 mix the toner particles with magnetic carrier particles. Although two augers are shown, a separate auger may be provided for mixing and to assist in picking up the developer onto the Magroll. In some embodiments, an intermediate Magroll (not shown) may be placed between the augers 60, 62 and the Magrolls 32, 34 so that the toner concentration is higher on the Magrolls 32, 34.

[0037] The developer belt 14A exits the housing 30 through a narrow slot 64. Suction can be applied to the area of ​​the slot to minimize developer particle leakage. Seals can also be used to limit developer particle leakage.

[0038] The augers 60, 62, the magnetic rollers 32, 34, and the developer rollers 18, 20, 22 may all be driven by a common drive system 24, such as a motor with appropriate gears and / or belts. Alternatively, separate drive systems may be used. The drive system 24 controls the speed of the developer rollers 18, 20, 22 so that the developer belt 14A matches or approximates the speed of the surface of the image transfer member 16 being driven. In other embodiments, the speed of the developer belt and the speed of the surface of the image transfer member being driven do not need to match exactly, and may have a speed ratio of up to, for example, 1.2:1.

[0039] One advantage of the developing system in Figure 2 is that the diameters of the dual magnetic rolls 32 and 34 can be smaller than in conventional systems that use a single large-diameter magnetic roll to transfer toner to a photoconductive surface. For example, two magnetic rolls 32 and 34 with a diameter of 22 mm can be mounted in a developer housing 30 that is smaller than that of a conventional 30 mm magnetic roll.

[0040] Another advantage is that the two small Magrolls 32, 34 provide two developing nips 36, 38, which allows for greater developing tolerance in a limited design space.

[0041] Another advantage is that the single nip 50 between the developer belt 14A and the image transfer member 16 provides flexibility in the final positioning of the developer housing 30, which enables a universal or semi-universal (interchangeable) developing system 12A. The single nip 50 also reduces or eliminates the need to frequently realign the Magroll developing nip. This allows the various interfaces within the developing housing to be maintained in a constant relationship when moving the developing housing 30 to a new position in the marking device. These interfaces may include the relationship between the Magroll and the auger, the relationship between the mixing auger and the pickup auger (if any), and the relationship between the dispenser and the mixing auger.

[0042] Another advantage is that more developing systems 12A, 12B, etc. can be accommodated around a single image transfer member 16 than in conventional marking devices. For example, eight or ten developing systems 12A, 12B, etc. can be installed around a drum transfer member 16 that is approximately 84 mm in size. In Figure 2, the developer roller 22 is partially enclosed within the housing 30, but in other embodiments, the developer roller 22 may be outside the housing 30, as shown in the embodiments of Figures 3 to 5. This helps to accommodate more developing systems 12A, 12B, etc. around a transfer member 16 of conventional size.

[0043] Referring here to Figure 3, in one embodiment, the marking device 10 comprises a first set of interchangeable developing systems 12A, 12B, 12C, 12D, and 12E positioned vertically to the left side of the marking device, and a second set of interchangeable developing systems 12F, 12G, 12H, 12I, and 12H positioned vertically to the right side of the marking device. Each of the first set of interchangeable developing systems may be configured as shown in Figure 2, and the only differences among the five left-side developing systems 12A-E are adjustments to the length of the developer belts 14A, 14B, etc., the position of the rollers 22 relative to the rollers 18, 20, and optionally the position of the slots 64 (Figure 2) through which the belts enter and exit the housing. For example, developer belts 14A and 14E are longer than developer belts 14B and 14D, for example, by at least 5%, or at least 10%, or have a length difference of at least 0.3cm, or at least 0.5cm, or at least 1cm, or at least 2cm. The developer belts 14B and 14D are longer than the developer belt 14C, for example, by at least 2% or at least 5%.

[0044] The second set of interchangeable developing systems 12F, 12G, 12H, 12I, and 12H may each be configured as a mirror image of the first side developing system (where Y defines the axis of symmetry of the marking device). The only differences between the five right-side developing systems are the length of the developer belts 14F, 14G, etc., the position of the roller 22 relative to the rollers 18, 20, and, optionally, the position of the slot 64 through which the belt enters and exits the housing. The belt length is selected based on the distance to the image transfer member 16.

[0045] By using developer belts 14A, 14B, etc., of different lengths, it becomes possible to stack the developing systems on each side vertically, which makes it easier to access the developing systems from adjacent sides 70, 72 of the marking device to replace, for example, toner containers 58A to 58J, which can also be stacked vertically.

[0046] Therefore, the marking device 10 in the embodiment of Figure 3 can consist of only two interchangeable developing system types: a left-side type configured as system 12A and a right-side type configured as system 12F. This reduces the unit manufacturing cost of the marking device 10 and also reduces the number of interchangeable developing systems 12A, 12F (or their components) that the manufacturer or customer needs to have on hand to repair the marking device.

[0047] While eight developing systems 12A, 12B, etc., are shown in Figure 3, please understand that fewer or more developing systems, such as three, four, five, or six, may be used. Each developing system develops the latent image using one of the following toner colors: cyan, magenta, yellow, or black, or a set of custom toners such as white, metallic, clear, or magnetic.

[0048] Although not shown in the illustration, the developer housing 30 may include a suitable manifold, end cap, electrical connections, etc., which are adapted to have the capability to be used in left-hand and right-hand housings, thereby providing a universal housing or a substantially universal housing.

[0049] In the embodiment shown in Figure 3, the image transfer member 16 is in the form of a continuous belt having a photoconductive surface 52. The belt is carried by a set of transfer rollers 74 (six transfer rollers in the illustrated embodiment), one or more of which are driven by an associated drive system (not shown). A latent image is formed on the belt 16 by associated charging and exposure stations (not shown for ease of explanation), as described with respect to Figure 2. The toner image layer formed on the image transfer belt 16 by the developing system is transferred to the printing medium sheet 76 as the sheet passes through the nip 78 to form a multilayer toner image. A transfer corotron 80 helps to attract the toner image to the sheet 76. A transport member 82, such as a conveyor belt or a plate with sheet transport rollers, transports the printing medium sheet 76 through the nip.

[0050] In addition to the advantages mentioned above, the embodiment in Figure 3 allows the developing systems 12A-F to be positioned at different distances from the image transfer belt 16 by providing developer belts 14A-J of different lengths. This allows for the centralized placement of the developing housings and opens up additional space around the image transfer belt 16 for modules for cleaning, charging, and discharging the belt 16.

[0051] Another advantage is that the developer housings 30A-30J can be placed close to the respective toner bottles 58A-58J, avoiding complex dispensing lines. This makes it easier to integrate the developer and toner containers into a single, replaceable unit.

[0052] Another advantage is that the size of the marking device housing 13 can be significantly reduced compared to existing marking devices. A reduction of 30-50% in the installation area of ​​the marking device is expected.

[0053] Figure 4 shows another embodiment of the marking apparatus 10 suitable for use in the system of Figure 1. The marking apparatus 10 may be configured similarly to the marking apparatus of Figure 3, unless otherwise noted. Similar elements are given the same numbering. The image transfer member 16 in this embodiment includes a hollow cylindrical drum 86 formed from, for example, a conductive metal and covered with a layer 88 of polymer photoconductive material defining a photoconductive surface 52. The drum transfer member 16 is driven by an associated drive system (not shown). A latent image is formed on the surface 52 of the drum transfer member 16 by associated charging and exposure stations (not shown for ease of explanation), as described with respect to Figure 2. The toner image layer formed on the drum transfer member 16 by the developing systems 12A-12J is transferred to the printing medium sheet 76 as the printing medium sheet 76 passes through a nip 78 between the drum transfer member 16 and a transport member 82. A transfer corotron 80 helps to attract the toner image layer to the sheet 76.

[0054] Figure 5 shows another embodiment of a marking apparatus 10 suitable for use with the system of Figure 1. The marking apparatus 10 may be configured similarly to the marking apparatus of Figure 4, unless otherwise noted. Similar elements are given the same numbering. In this embodiment, the marking apparatus includes a set of image transfer members 16A to 16F for each of a set of developing systems 12A to 12F. Each of the image transfer members 16A to 16F is in the form of a hollow cylindrical drum having a photoconductive surface 52, as described with respect to Figure 4. Each of the drum transfer members 16 to 16F is driven by an associated drive system (not shown). Alternatively, a common drive system may drive all of the drum transfer members 16A to 16F. Latent images are formed on the respective surfaces 52 of the transfer members 16A to 16F by associated charging stations and exposure stations (not shown for ease of explanation), as described with respect to Figure 2. The toner image layer formed on the transfer members 16A to 16F by the developing systems 12A to 12F is transferred to an intermediate transfer member in the form of a belt 89, which is transported by a set of driven rollers 90A, 90B, and 90C. Transfer Corotrons 80A to 80F, each associated with the drum transfer members 16A to 16F, help transfer the toner image layer to the belt 89. The transferred image is transferred from the belt 89 to the printing medium sheet 76 as the printing medium sheet 76 passes through a nip 78 between the belt and the transport member 82, adjacent to the rollers 90. A transfer Corotron 80G located beneath the transport member 82 helps attract the toner image layer to the sheet 76.

[0055] In this embodiment, each of the developing systems 12A to 12F may be identically configured and may be horizontally aligned, allowing each of the toner containers 58A to 58F to be accessible from the upper end 91 of the marking device housing.

[0056] In another embodiment, the upper horizontal portion of the belt 89 functions as a conveying member 82 (not shown) 76, and the Corotron 80G is omitted.

[0057] Figures 3 and 4 show the direct transfer of the toner image layer from the image transfer members 16, 16A, etc., to the sheet. However, in the embodiment shown in Figure 5, the image is transferred from the image transfer members 16, 16A, etc., to an intermediate transfer member 89 such as a belt, and from there the toner image layer is transferred to the printing medium sheet. This configuration is also advantageous when a larger number of developing systems are to be accommodated, as a first set of developing systems can be arranged around the first image transfer member, and a second set of developing systems can be arranged around the second image transfer member, with the first and second image transfer members transferring their respective toner image layers to the intermediate transfer member.

[0058] Figure 6 shows an embodiment of the marking device 10 similar to the marking device in Figure 3, except that the developer belts 14A to 14J are all the same length. This allows the left-side developing systems 12A to 12E to be identical to each other, and the right-side developing systems 12A to 12F to be identical to each other and mirror images of the left-side developing systems. The commonality between the developer housings 30A to 30J reduces the cost of manufacturing and replacement parts.

[0059] Another advantage of the various embodiments described herein is that the versatility of arranging the developer housing around the drum or belt image transfer member can provide an increased color gamut and / or additional colors / coatings, etc.

[0060] Returning to Figure 1, the multilayer toner image may be permanently attached to the sheet 76 by heat and / or pressure, for example, by a fixing unit 92. The fixing unit may be located downstream of the marking device 10 within the marking device housing. In the embodiment of Figure 5, there may be a single fixing unit located downstream of the last drum transfer member 16F. Alternatively, each fixing unit may be located downstream of each of the transfer members 16A to 16F to fix each toner image layer before the next toner image layer is placed on the sheet.

[0061] Figure 1 also shows a printing medium source 94, a sheet feeder 96, an optional post-processing device 98, and an output device 100, which are connected by a sheet transport system 102. Each of the components 10, 92, 94, 96, 98, 100, and 102 may be under the control of a common control system 104. The printing medium source 94 contains, for example, a certain supply amount of printing medium sheets 76 in one or more supply trays. The sheet feeder 96 supplies the sheets in a line to the sheet conveyor system 102. The sheet transport system 102, including transport members 82, transports the sheets to the downstream marking device 10, fixing unit 92, optional post-processing device 98, and finally to the output device 100. The sheet transport system 102 may include rollers, air jets, conveyor belts, or a combination thereof. In some embodiments, the sheet transport system 102 may provide a return path for inverting the printed sheet 76 and returning it to the marking device 10 and fuser unit 92 in order to print a toner image on a second side of the printed sheet 76 (duplex printing). An optional post-processing device 98 may include one or more of the following: a stacker, binder, stapler, hole puncher, sheet folder, etc. The output device 100 may include one or more output trays from which the user can collect printed and optionally post-processed sheets 76 from the output trays. The control system 104 may include memory for storing software that is executed by the associated hardware processors to operate the other components 10, 92, 94, 96, 98, 100, and 102 of the printer 1 during printing.

[0062] Referring here to Figure 7, a drive mechanism 110 suitable for accommodating developer belts 14A, 14B, etc., of different lengths is shown. The drive mechanism includes a motor 112 that drives a drive shaft 114. The drive shaft carries the drive belt 116, thereby rotating the shafts 118, 120, and 122 of three rollers 18, 20, and 22. The drive shaft 114 and / or motor 114 are repositionable, as indicated by arrow X. This ensures that the drive belt 112 remains taut when the rollers 22 are repositioned, as indicated by arrow Z. For example, when a longer developer belt 14A is used, the roller 22 is further displaced from the rollers 18 and 20, and the drive shaft 114 / motor 112 is moved closer to the nearest of the rollers 18 and 20. The ends of shafts 118 and 120 are positioned in slots 124 and 126 within the support member 128, thereby constraining the rollers to rotational motion, while the end of shaft 122 is repositionable vertically within slot 130. As can be understood, other mechanisms are conceivable for accommodating developer belts 14A, 14B, etc., of different lengths. For example, drive belts 112 of different lengths may be provided.

[0063] In another embodiment, gear mechanisms 132, 134, and 136, which are transported by a telescopic drive shaft, may be used, as shown in Figure 8. This allows the gear mechanism 136 to be moved further away from the motor 112 in the direction of arrow Z when a longer developer belt 14B is used.

[0064] The image transfer belt 16 shown in Figures 3 and 6 may be formed from, for example, a conductive material. Suitable materials include polymers in which conductive particles are dispersed in at least a portion thereof. For example, the outer layers of image transfer belts 16, 16A, 16B, etc., may include a first layer containing carbon black particles. Carbon black particles have high conductivity, and conductivity can be greatly increased even with a small amount of carbon black particles used. Examples of carbon black particles included in the first layer include Ketjenblack, oil furnace black, channel black, acetylene black, and surface-oxidized carbon black. Among these, surface-treated carbon black is preferred from the viewpoint of consistency of electrical resistance over time. As the polymer, polyimide resins, such as polyimide resins, polyamideimide resins, polyetherimide resins, siloxane-modified polyimide resins, siloxane-modified polyamideimide resins, mixtures of polyamideimide and polybenzimidazole, fluoropolyimide, or combinations thereof can be used. For examples of such polymer materials, see, for example, U.S. Patent Application Publications 2011 / 0244247(A1), 2012 / 0183783(A1), 2013 / 0273373(A1), 2015 / 0227065(A1), 2020 / 0325333(A1), 2020 / 0326645(A1), and 2020 / 0356029(A1) (all of which are incorporated herein by reference).

[0065] In the case of drum-shaped image transfer members 16, 16A, 16B, etc., as shown in Figures 2, 4, and 5, the outer layer 88 may be configured in the same way as the image transfer belts 16, 16A, 16B described above. However, since the layer 88 is not self-supporting, it can be made thinner than the belt.

[0066] The developer belts 14A, 14B, 14C, etc., shown in Figures 2-8 can be formed from any suitable material that can become charged relative to the magnetic roller and attract toner particles to the developer belt. Suitable materials include those described for the image transfer members 16, 16A, etc. (or, in the case of a drum, its polymer layer). The developer belts 14A, 14B, 14C, etc., may be joined or seamless endless belts.

[0067] The image transfer member (belt or drum) may be coated with a ceramic or Ceramer-type coating. Ceramer is a sinterable high-performance polymer based on polyphenylene sulfone (PPSO2). The coating may be 0.01 to 5 mm thick, for example, at least 0.05 mm or up to 0.3 mm thick. For example, a ceramic coating measured at 200 V yielded 10 megaohms / cm² for a 0.13 mm thick ceramic coating. 3 It provides 6 × 10 in an electric field of 1.5V / micron. 7 It can provide the volume resistivity.

[0068] Referring now to Figure 9, a printing method that can be performed using one or more of the exemplary developer systems described herein is shown. The method begins in S100.

[0069] In S102, a first developer material is prepared in the first developer housing 30A of the first developing system 12A, and the first developer material includes first toner particles.

[0070] In S104, S102 may be repeated for one or more additional developing systems 12B, 12C, etc.

[0071] In S106, a portion of the first toner particles is transferred to the first continuous developer belt 14A of the first developing system 12A by, for example, at least one magnetic roller 32, 34.

[0072] In S108, S106 may be repeated for each additional developer system.

[0073] In S110, a first latent image is formed on the first image transfer members 16, 16A.

[0074] In S112, S110 may be repeated for each additional developer system, and the latent image is formed on the first image transfer members 16, 16A, or on additional image transfer members 16B, 16C, etc.

[0075] In S114, the first latent image is developed on the first image transfer member using a portion of the toner particles transferred from the first developer belt 14A to form the first toner image layer.

[0076] In S116, S114 may be repeated for each additional developer system, and the latent image is developed on the first image transfer member 16, or on additional image transfer members 16B, 16C, etc., to form an additional toner image layer on or away from the first toner image layer.

[0077] In S118, the first toner image layer is transferred from the first image transfer member to the printing medium sheet 76.

[0078] In S120, an additional toner image layer may be transferred from the first image transfer member 16 (or, if present, from additional image transfer members 16B, 16C, etc.) to the printing medium sheet 76.

[0079] In S122, the sheet having the toner image thereon may be fixed, optionally post-processed, and output.

[0080] In some embodiments, the printed sheet may be inverted and returned to the marking device for printing on a second side of the sheet, as described with respect to S106-S122, before being optionally post-processed and output.

[0081] This method terminates in S124.

[0082] It will be understood that variations of those disclosed above, as well as other features and functions, or substitutes thereof, may be combined into many other different systems or applications. Various substitutes, modifications, variations, or improvements therein that are not currently anticipated or anticipated may be made thereafter by those skilled in the art, and these are also intended to be covered by the following claims.

Claims

1. An image transfer member, and 1. A marking device including a plurality of development systems, each of said development systems comprising: a housing configured to contain a developer material including toner particles; at least one magnetic roller within said housing for attracting said developer material to its surface; a continuous developer belt that attracts the toner particles from the at least one magnetic roller to a surface of the developer belt; a plurality of developer rollers around which the developer belt is conveyed, one of the developer rollers being positioned adjacent to the image transfer member, whereby a portion of the toner particles are transferred to a latent image formed on the image transfer member; at least two of the plurality of development systems are stacked vertically directly on top of one another, the developer belt of a first of the at least two development systems having a first length and the developer belt of a second of the at least two development systems having a second length longer than the first length, the lengths being based on the distance of each of the development systems to the image transfer member.

2. A marking device as described in claim 1, wherein in each of the plurality of development systems, the at least one magnetic roller includes two magnetic rollers.

3. A marking device as described in claim 1, wherein in each of the plurality of development systems, the plurality of developer rollers includes three developer rollers.

4. A marking device as described in claim 1, wherein in each of the multiple development systems, the set of developer rollers is driven by a common drive mechanism.

5. The marking device of claim 1 , wherein at least two of the plurality of development systems are replaceable.

6. The marking device of claim 1 , wherein at least two of the plurality of development systems are mirror images of each other.

7. The marking device of claim 1 , wherein at least two of the plurality of development systems are horizontally aligned.

8. The marking device of claim 1 , wherein the marking device includes at least eight of the development systems.

9. The marking device of claim 1 , wherein the image transfer member comprises one of a belt and a drum having a photoconductive layer.

10. 10. A printer comprising the marking device of claim 1 and a sheet transport system that conveys an associated print media sheet through the marking device to receive a toner image layer from the image transfer member.

11. 1. A printing method comprising: Providing a first developer material containing first toner particles in a first housing; transferring a portion of said first toner particles to a first continuous developer belt; developing a first latent image on a first image transfer member with a portion of the transferred toner particles to form a first toner image layer; transferring the first toner image layer to a print media sheet; Providing a second developer material containing second toner particles in a second housing; transferring a portion of said second toner particles to a second continuous developer belt; developing a second latent image on the first image transfer member or a second image transfer member with a portion of the transferred second toner particles to form a second toner image layer, the second continuous developer belt having a different length from the first continuous developer belt, the length being based on the distance to the image transfer member where the second latent image is developed; transferring the second toner image layer to the print media sheet; A method comprising:

12. The method of claim 11 , wherein the second latent image is developed on the first image transfer member.

13. a print media source; a marking device that receives a print medium from the print medium source and applies a toner image to the print medium, an image transfer member; at least one charging station for charging the photoconductive surface of said image transfer member; an exposure station for forming a latent image on said charged photoconductive surface; a plurality of development systems, at least two of said plurality of development systems each comprising: a housing configured to contain a developer material including toner particles; a continuous developer belt that transports the toner particles from the housing to a surface of the image transfer member to develop the latent image on the image transfer member to form a toner image layer, the first development system having a longer developer belt than the second development system; at least one development system comprising: a marking device comprising: a sheet transport system for conveying the sheet of print media from the print media source to the marking device to receive the toner image layer from the image transfer member; A printer comprising:

Images