Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
  • G03G15/23—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 specially adapted for copying both sides of an original or for copying on both sides of a recording or image-receiving material
  • G03G15/231—Arrangements for copying on both sides of a recording or image-receiving material
  • G03G15/232—Arrangements for copying on both sides of a recording or image-receiving material using a single reusable electrographic recording member
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
  • G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
  • G03G15/101—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer for wetting the recording material
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G21/00—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
  • G03G21/0088—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge removing liquid developer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G2215/00—Apparatus for electrophotographic processes
  • G03G2215/00362—Apparatus for electrophotographic processes relating to the copy medium handling
  • G03G2215/00443—Copy medium
  • G03G2215/00451—Paper
  • G03G2215/00455—Continuous web, i.e. roll

Definitions

• DOUBLE SIDED IMAGING FIELD OF THE INVENTION The present invention relates generally to improvements in imaging apparatus and, more particularly, to imaging on both sides of a substrate.
• BACKGROUND OF THE INVENTION There are various applications for imaging on both sides of a substrate such as paper.
• Double sided imaging is generally carried out by a system including first and second imaging devices, wherein one side of the substrate is imaged by the first imaging device and the opposite side of the substrate is imaged by the second imaging device. It is appreciated, however, that the use of two imaging devices configured for double-sided printing is expensive and highly space consuming.
• the substrate is provided in sheets having predetermined dimensions adapted for a given page layout, it is possible to image both sides of each sheet by, first, feeding the sheet with a first surface interfacing the imaging device and, then, refeeding the sheet with the second, opposite, surface facing the imaging device.
• This method is not available for web-fed imaging.
• a first surface of a continuous substrate is fed to the imaging device by a controlled feeding mechanism and at least one image is formed on the first surface of the substrate.
• a second, opposite, surface of the substrate is controllably fed to the imaging device and at least one image is formed on the second surface of the substrate.
• the controlled feedings of the first and second surfaces of the substrate are preferably synchronized so as to control the relative locations of the images formed on the first and second surfaces .
• a first plurality of images are formed on the first surface of the substrate and a second plurality of corresponding images are formed on the second surface of the substrate, wherein the order of imaging is adapted to appropriately locate each of the second plural ity of images oppos ite a corresponding image of the first plurality of images .
• the order of imaging includes , initially , imaging a predetermined number of images on the first surface to account for the length of continuous substrate separating between imaging of the first surface and imaging of the second surface and , then, altematingly imaging on the first and second surfaces such that each imaging on the first surface is followed by imaging on the second surface.
• the imaging device includes an intermediate transfer member ( ITM ) which transfers developed toner images from an imaging surface, for example a photoconductor surface, to the substrate.
• ITM intermediate transfer member
• the device preferably further includes first and second impression members , wherein the f irst impression member urges the first surface of the substrate against the ITM at a first image transfer region and the second impression member urges the second surface of the substrate against the ITM at a second image transfer region .
• a given portion of the continuous substrate is fed, first, to the first image transfer region and then, after being guided through the inverter mechanism , the substrate is fed to the second image transfer region.
• an improved BID Binary Image Development
• a BID development system is used in which only a portion of the thickness of the concentrated layer of toner is transferred onto the photoconductor surface.
• the developed images are subsequently transferred to the substrate, preferably via the ITM, with substantially no toner residue remaining on the ITM.
• a system for double-sided, electrostatic imaging on a continuous-web substrate having first and second substrate surfaces including: an imaging device comprising an image transfer member with a toner-image bearing surface having selectively formed thereon first and second images; and a web-feeder system which selectively brings the first and second substrate surfaces into operative engagement with the toner-image bearing surface, to transfer thereto the first and second images, respectively, in accordance with a preselected imaging sequence.
• the first substrate surface engages the toner-image bearing surface at a first impression region and the second substrate surface engages the toner-image bearing surface at a second impression region.
• the predetermined imaging sequence includes first surface imaging cycles, during which cycles the first images are transferred to the first substrate surface, and second surface imaging cycles, during which cycles the second images are transferred to the second substrate surface.
• the predetermined imaging sequence includes a plurality of consecutive first surface imaging cycles followed by alternating, first surface and second surface, imaging cycles.
• the web-feeder system includes a first impression member which urges the continuous substrate against the toner- image bearing surface during each first surface imaging cycle, and a second impression member which urges the continuous substrate against the toner-image bearing surface during each second surface imaging cycle.
• the web-feeder system further includes a substrate inverter, operating on the continuous substrate between the first and second impression members , which inverts between the f irst and second surf aces of the continuous substrate.
• the web- feeder system includes a substrate advance mechanism operative for advancing the continuous substrate through the first and second impression regions.
• the web- feeder system further includes a controller which controls the advance of the continuous substrate through the first and second impression regions, in accordance with the predetermined imaging sequence, by control ling the operation of the substrate advance mechanism .
• the controller preferably also controls the engagement and disengagement of the first and second substrate surfaces with the toner-image bearing surface, in accordance with the predetermined imaging sequence, by controlling the position of the first and second impression members relative to the toner- image bearing surface.
• the first images are formed on the first substrate surface with a preselected spacing .
• the imaging device produces a post-image mark on the space following each first image on the first substrate surface.
• the advancing mechanism rewinds a preselected length of the continuous substrate through the first impression region following each first surface imaging cycle .
• the continuous substrate is accelerated to a surface velocity comparable with that of the toner-image bearing surface before each first surface imaging cycle .
• the web- feeder system further includes a f irst mark detector associated with the first substrate surface, ahead of the first impression region , which detects the post image marks on the first substrate surface and produces first detection signals in response thereto.
• the controller triggers each first surface imaging cycle in response to the first detection signal of the preceding post-image mark.
• the advancing mechanism rewinds a preselected length of the continuous substrate through the second impression region following each second surface imaging cycle.
• the continuous substrate is accelerated to a surface velocity comparable with that of the toner-image bearing surface before each second surface imaging cycle .
• the web- feeder system further includes a second mark detector associated with the first substrate surface , between the first and second impression regions , which detects the post image marks on the first substrate surface and produces second detection signals in response thereto.
• the controller triggers each second surface imaging cycle in response to the second detection signal of the preceding post-image mark .
• the web-feeder system further includes a cutter, associated with the continuous substrate downstream of the second impression region, which cuts the continuous substrate at the spaces between the first images on the first substrate surface.
• the web-feeder system also includes a third mark detector associated with the first substrate surface, ahead of the cutter, which detects the post image marks on the first substrate surface and produces third detection signals in response thereto. The controller preferably activates the cutter in response to the third detection signals.
• the web-feeder system further includes at least one free- loop arrangement which contains a variable length of the continuous substrate.
• the at least one free-loop arrangement preferably includes a f irst f ree- loop arrangement ahead of the first impression region.
• the at least one free-loop arrangement preferably further includes a second free- loop arrangement between the first impression region and the second impression region .
• the web- feeder system pref erably al so includes a third f ree- loop arrangement, between the second impression region and the cutter, which contains a variable length of the continuous substrate.
• the web- feeder system further includes a first length detector, associated with the continuous substrate between the first and second impression regions , which produces an electric output respons ive to the position of the continuous substrate relative to the f irst impression region .
• the first length detector preferably includes an encoder.
• the controller addresses the first mark detector only within preset , first , detection time windows and wherein the t ime gaps between the f irst detection windows are set in accordance with the output of the first length detector .
• the web- feeder system further includes a second length detector, associated with the continuous substrate downstream of the second impression region , which produces an electric output responsive to the position of the continuous substrate relative to second impression region.
• the second length detector includes an encoder .
• the controller addresses the second mark detector only within preset, second , detection time windows and wherein the time gaps between the second detection windows are set in accordance with the outputs of the first and second length detectors.
• the controller addresses the third mark detector only within preset, third, detection time windows and wherein the time gaps between the third detection windows are set in accordance with the output of the second length detector.
• a method for double-sided imaging on a continuous-web substrate, having f irst and second substrate surfaces using an electrostatic imaging device including an image transfer member having an toner-image bearing surface, the method including: providing a first toner image on the toner-image bearing surface; transferring the first toner image from the toner- image bearing surface to the first substrate surface; providing a second toner image on the toner-image bearing surface; and transferring the second toner image from the toner- image bearing surface to the second substrate surface.
• a method for double-sided imaging on a continuous-web substrate, having first and second substrate surfaces, using an electrostatic imaging device including an image transfer member having an toner- image bearing surface the method including: selectively forming on the toner-image bearing surface first and second toner images, in accordance with a preselected imaging sequence; and selectively transferring the first and second toner images to the first and second substrate surfaces, respectively, in accordance with the preselected imaging sequence.
• selectively forming the first and second toner images in accordance with the predetermined imaging sequence includes, first, consecutively forming a plurality of first toner images and, then, alternatingly forming first and second toner images.
• transferring the first toner image includes transferring the first toner image at a first impression region and wherein transferring the second toner image includes transferring the second toner image at a second impression region.
• the method including inverting the first and second substrate surfaces of the continuous substrate between the first and second impression regions.
• the imaging method further includes advancing the continuous substrate through the first and second impression regions in accordance with the predetermined imaging sequence.
• transferring the first toner images to the first substrate surface includes transferring the first toner images with a preselected spacing.
• the method further includes producing a post- image mark on the space following each first toner image.
• the method further includes rewinding a preselected length of the continuous substrate through the first impression region following transferring of each first toner image.
• the method also includes accelerating the continuous substrate to a surface velocity comparable with that of the toner-image bearing surface before transferring of each first toner image.
• the method includes detecting the post image marks on the first substrate surface ahead of the first impression region.
• the method also includes triggering the transferring of each first toner image in response to the post-image mark of the preceding first toner image.
• the method further includes rewinding a preselected length of the continuous substrate through the second impression region following transferring of each second toner image.
• the method also includes accelerating the continuous substrate to a surface velocity comparable with that of the toner-image bearing surface before transferring of each second toner image.
• the method includes detecting the post image marks on the first substrate surface between the first and second impression regions .
• the method also includes triggering the transferring of each second toner image in response to the post-image mark of the preceding first toner image.
• the imaging method further includes cutting the continuous substrate at the spaces between the first images on the first substrate surface .
• the method further includes detecting the post image marks on the first substrate surface downstream of the second impression region .
• cutting the continuous substrate includes cutting the continuous substrate in response to detection of post-image marks .
• the imaging method further includes monitoring the position of the continuous substrate relative to the first impression region .
• detecting the post-image marks on the continuous substrate ahead of the first impression region includes detecting the post-image marks only within preset, first, detection time windows .
• the imaging method includes setting the time gaps between the first detection time windows in accordance with the monitored position of the continuous substrate relative to the first impression region.
• the imaging method further includes monitoring the position of the continuous substrate relative to the second impression region.
• detecting the post-image marks on the continuous substrate between the first and second impression regions includes detecting the post-image marks only within preset, second, detection time windows.
• the imaging method includes setting the time gaps between the second detection time windows in accordance with the monitored position of the continuous substrate relative to the second impression region.
• the toner-image bearing surface includes a developed imaging surface.
• the imaging surface includes a photoreceptor surface.
• the imaging device includes an intermediate transfer member and the toner- image bearing surface includes a surface of the intermediate transfer member .
• a squeegee device for squeegeeing a first surface comprising: a squeegee roller having a squeegee surface, a first portion of which engages said first surface; a leaf spring which is applied to a second portion of said squeegee surface to urge the squeegee roller against the first surface, wherein the leaf spring contacts the squeegee roller along its length at discrete regions separated by non- contacting areas.
• portions of the spring comprises a low friction material contacting the squeegee roller at said second portion.
• a squeegee device for squeegeeing a first surface comprising : a squeegee roller having a squeegee surface, a first portion of which engages said first surface; a leaf spring which is applied to said first surface and is applied to a second portion of said squeegee surface to urge the squeegee roller against the first surface, and a wire wrapped around the leaf spring such that the wire contacts the squeegee surf ace at a plurality of points along the length of the roller, said points being separated by spaces at which no contact is made with the squeegee roller.
• the wire compri ses a low f riction material, preferably, teflon.
• the leaf spring contacts the squeegee roller along substantially its entire length.
• a cleaning device for removing residual toner from a toner-bearing surface comprising: a first, rotating, roller having a conductive surface contacting the toner-bearing surface with substantially zero relative motion therebetween; a sponge roller rotating in the same sense as that of the first roller, wherein the sponge roller is substantially compressed by said first roller at a region of engagement therebetween; and a second roller which compresses said sponge roller at a region thereof remote from said region of engagement.
• the first roller is biased to a voltage which attracts residual toner particles on said toner-bearing surface to said conductive surface.
• the device includes a resilient blade engaging said conductive surface where said surface leaves said region of engagement and operative to remove toner from said conductive surface.
• Fig . 1 is a schematic illustration of a system for double-sided imaging constructed and operative in accordance with a preferred embodiment of the present invention
• Fig. 2 is a schematic illustration of a system for multi-color, double-sided imaging, constructed in accordance with a preferred embodiment of the present invention
• Fig. 3 is a detailed schematic illustration of a cleaning station constructed and operative in accordance with a preferred embodiment of the present invention
• Fig. 4 is a detailed schematic illustration of a developer assembly constructed and operative in accordance with a preferred embodiment of the present invention
• Fig. 1 is a schematic illustration of a system for double-sided imaging constructed and operative in accordance with a preferred embodiment of the present invention
• Fig. 2 is a schematic illustration of a system for multi-color, double-sided imaging, constructed in accordance with a preferred embodiment of the present invention
• Fig. 3 is a detailed schematic illustration of a cleaning station constructed and operative in accordance with a preferred embodiment of the present invention
• Fig. 4 is
• FIG. 5 is a detailed schematic illustration of a web- feeder system constructed and operative in accordance with a preferred embodiment of the present invention
• Fig. 6 is a schematic, block diagram, illustration of circuitry for controlling the operation of the system of Fig. 2
• Figs. 7A and 7B are, respectively, top and perspective, schematic, illustrations depicting a method of inverting a continuous substrate in accordance with a preferred embodiment of the present invention
• Fig. 8 is a schematic flow-chart showing a preferred sequence of operation of the web-feeder system of Fig. 5.
• Fig. 1 illustrates imaging apparatus constructed and operative in accordance with a preferred embodiment of the present invention.
• the apparatus of Fig. 1 comprises a drum 10 arranged for rotation in a direction generally indicated by arrow 14.
• Drum 10 preferably has a cylindrical photoconductive surface 16, made of selenium, a selenium compound, an organic photoconductor or any other suitable photoconductor known in the art.
• Photoconductive surface may be in the form of a photoreceptor sheet and may use any suitable arrangement of layers of materials as is known in the art. However, in the preferred embodiment of the invention, certain of the layers of photoreceptor sheet 16 are removed from the ends of the sheet to facilitate its mounting on drum 10. This preferred photoreceptor sheet and preferred methods of mounting it on drum 10 are described in a co- pending application of Belinkov et al .
• photoreceptor 16 may be deposited on drum 10 and may form a continuous surface.
• a charger 18 may be any type of charger known in the art, such as a corotron, a scorotron or a roller.
• charger 18 is a double scorotron including a housing and two corona wire segments 218.
• the voltage between wires 218 and surface 16 should preferably be as high as possible, the actually obtained voltage is generally not higher than 7000-7500 Volts, typically 7300 Volts, due to discharging between wires 218 and housing 33.
• the present invention provides a method for raising the voltage between wire segments 218 and surface 16.
• housing 33 is electrically insulated from other elements of the imaging device and is charged to a relatively high voltage, preferably on the order of 1500 Volts.
• imaging apparatus 19 is a modulated laser beam scanning apparatus, or other laser imaging apparatus such as is known in the art.
• Light source 19 forms a desired latent image on charged photoconductive surf ace 16 by selectively discharging a portion of the photoconductive surface, the image portions being at a first voltage and the background portions at a second voltage .
• the discharged portions preferably have a negative voltage of less than about 100 volts.
• Surface 21 of developer roller 22 is preferably composed of a soft polyurethane material, preferably made more electrically conductive by the inclusion of conducting additives, while the core of developer roller 22 may be composed of any suitable electrically conductive material.
• drum 10 may be formed of a relatively resilient material, and in such case surface 21 of developer roller 22 may be composed of either a rigid or a compliant material.
• Developer roller 22 is preferably charged to a negative voltage of approximately 300 - 600 volts, desirably approximately -400 volts.
• surface 21 is coated with a very thin layer of concentrated liquid toner , preferably containing 20-50% charged toner particles, more preferably 25% solids or more .
• the layer is preferably between 5 and 30 ⁇ m , more preferably between 5 and 15 ⁇ m , thick .
• Developer roller 22 itself is charged to a voltage that is intermediate the voltage of the charged and discharged areas on photoconductive surface 16.
• a liquid toner similar to the toner described in Example 1 of U. S . Patent 4, 794, 651 , the disclosure of which is incorporated herein by reference, is used although other types of toner are usable in the invention.
• the carbon black in the preferred toner i s replaced by colored pigments as is well known in the art .
• the liquid toner is preferably maintained in a toner reservoir 65 which is associated with development assembly 23.
• a plurality of development assemblies 23A-23D may be provided, one for each color of the multi-color image. According to this embodiment of the invention, assemblies 23A-23D sequentially engage photoconductive surface 16 to develop sequentially produced latent images thereon.
• Assemblies 23A-23D may be combined into an integrated, multi-color, development assembly 63.
• the present invention is described in the context of a BID (Binary Image Development) system in which the concentrated layer of liquid toner is completely transferred to photoconductor surface 16 during development.
• BID Binary Image Development
• the present invention is also compatible with a partial BID system in which only a portion of the thickness of the concentrated toner layer is transferred to surface 16 by appropriately adjusting the development voltages.
• a preferred partial BID system of this type is described in PCT publication WO 94/16364, the disclosure of which is incorporated herein by reference.
• Downstream of development assembly 23, as shown in Figs. 1 and 2 a preferred embodiment of the imaging apparatus further includes a background discharge device 28.
• Discharge device 28 is operative to flood the sheet 12 with light which discharges the voltage remaining on sheet 12, mainly to reduce electrical breakdown and improve subsequent transfer of the image. Operation of such a device in a write black system is described in U.S. Patent 5,280,326, the disclosure of which is incorporated herein by reference.
• the latent image developed by means of the process described above may then be directly transferred to a desired substrate in a manner well known in the art.
• the developed image is transferred to the desired substrate via an intermediate transfer member 40, which may be a drum or belt, in operative engagement with photoconductive surface 16 of drum 10 bearing the developed image.
• Intermediate transfer member 40 rotates in a sense opposite to that of photoconductive surface 16, as shown by arrow 43, providing substantially zero relative motion between their respective surfaces at the point of image transfer.
• Intermediate transfer member 40 is operative for receiving the toner image from photoconductive surface 16 and for transferring the toner image to a final substrate 42, such as paper.
• Final substrate 42 which is preferably continuously fed as described below, is urged against the image bearing surface of ITM 40 by either a first impression roller 39 or a second impression roller 41, in accordance with a predetermined imaging sequence, as described in detail below.
• the transfer of the toner image from ITM 40 to substrate 42 is preferably electrostatically assisted by charging impression rollers 39 and 41 to an appropriate voltage, which is adapted to counteract the electrostatic attraction of the toner image to ITM 40.
• substrate 42 engages ITM 40 at a first impression region 239, when urged by roller 39, and at a second impression region 241, when urged by roller 41.
• Impression rollers 39 and 41 form part of a web-feeder system 100 which is described below with reference to Fig. 5.
• a heater 45 Disposed internally of intermediate transfer member 40 there may be provided a heater 45, to heat intermediate transfer member 40 as is known in the art. Transfer of the image to intermediate transfer member 40 is preferably aided by providing electrification of intermediate transfer member 40 to provide an electric field between intermediate transfer member 40 and the image areas of photoconductive surface 16.
• Intermediate transfer member 40 preferably has a conducting layer 44 underlying an elastomer layer 46, which is preferably a slightly conductive resilient polymeric layer.
• Intermediate transfer member (ITM) 40 may be any suitable intermediate transfer member, for example, as described in U.S. Patents 4,684,238 and 4,974,027 or in PCT Publication WO 90/04216, the disclosures of which are incorporated herein by reference.
• ITM 40 has a multilayered transfer portion such as those described below or in U.S. Patents 5,089,856 and 5,047,808, or in U.S. Patent application S. ⁇ . 08/371,117, filed January 11, 1995 and entitled IMAGING APPARATUS AND INTERMEDIATE TRANSFER BLANKET THEREFOR and corresponding applications in other countries, the disclosures of all of which are incorporated herein by reference.
• Member 40 is maintained at a suitable voltage and temperature for electrostatic transfer of the image thereto from image bearing surface 16.
• the single color image is transferred to intermediate transfer member 40.
• Subsequent images in different colors are sequentially transferred in alignment with the previous image onto intermediate transfer member 40.
• the complete multi-color image is transferred from transfer member 40 to substrate 42.
• Impression rollers, 39 or 41 produce operative engagement between intermediate transfer member 40 and substrate 42 at regions 239 or 241, respectively, when transfer of the composite image to substrate 42 takes place.
• each single color image can be separately transferred to the substrate via the intermedi ate trans f er member .
• the substrate may be fed through the imaging device once for each color , using dual- feeder system 100 .
• the intermediate transfer member can be omitted and the developed single color images transferred sequentially directly from surface 16 of drum 10 to substrate 42.
• the invention is not limited to the specific type of image forming system used and the present invention is also useful with any suitable imaging system which forms a liquid toner image on an image forming surface, such as that shown in the above referenced Patent Application S . N .
• cleaning station 49 includes a casing 81 which i s associated with a carrier liquid inlet 90 and a carrier liquid outlet 92 .
• Carrier liquid inlet 90 preferably includes a perforated nozzle 191 which disperses the supplied carrier liquid .
• Fresh and , preferably , cooled carrier liquid is preferably pumped from a carrier liquid reservoir (not shown ) to inlet 90 which scatters the liquid in the direction of a wet cleaning roller 88.
• Wet cleaning roller 88 i s preferably formed of a relatively rigid material , such as metal , and is mounted j uxtaposed with surface 16 of drum 10, preferably with a gap of 120 to 150 micrometers from surface 16.
• Roller 88 which preferably has a di ameter of approximately 22 mi l l imeters , i s preferably rotated in the same sense as that of drum 10 , such that their respective surfaces move in opposite directions at the region of interface .
• the linear velocity of surface 16 is between 60 and 150 centimeters per second
• the surface velocity of roller 88 is equal to approximately 80 percent of the velocity of surface 16.
• the toner on surface 16, which is now diluted in the wetting carrier liquid, is carried by surface 16 of drum 10 towards a sponge roller 82 which is urged against surface 16, such that the surface of roller 82 is deformed inwardly by approximately 1.5 millimeters.
• Sponge roller 82 which is preferably constructed of an approximately 4 millimeter layer of open-cell polyurethane around a metal core having a diameter of approximately 14 millimeters, absorbs the diluted toner and scrubs it off surface 16.
• sponge roller 82 preferably rotates in the same sense as that of drum 10, such that their respective surfaces move in opposite directions at their region of contact.
• a squeezer roller 84 which is urged deeply into sponge roller 82, preferably to a depth of approximately 2 mi ll imeters f rom the original surf ace of roller 82 , squeezes used carrier liquid out of roller 82.
• Squeezer 84 which is preferably a metal roller having a diameter of approximately 16 millimeters , is preferably an idler roller, i . e. rotates in response to the rotation of sponge roller 82.
• a scraper 56 preferably a resilient blade urged against surface 16 next to sponge roller 82 , completes the removal of any residual toner on surface 16 which may have not been removed by sponge roller 82 .
• Blade 56 is preferably formed of polyurethane and has a thickness of approximately 3 millimeters .
• the used carrier liquid squeezed out of roller 82 is drained by free-fall , along the surface of a fluid guide 86 which separates the relatively warm and soiled carrier liquid from the fresh carrier liquid supplied by inlet 90 , back to the liquid toner reservoir via carrier liquid outlet 92.
• Fluid guide 86 is preferably resiliently urged against the surface of roller 88 via a, preferably spongy, sealing pad 87.
• Fluid guide 86 is preferably formed of metal and sealing pad 87 is preferably formed of closed- cell polyurethane.
• a lamp 58 completes the imaging cycle by removing any residual charge, characteristic of the previous image, from photoconductive surface 16, if necessary.
• lamp 58 may be omitted and surface 16 is discharged only by discharge device 28, as described above with reference to Fig. 1 and Fig. 2.
• the liquid toner concentrate which is transferred to drum 10 has substantially the same toner particle concentration as the image when it is transferred from drum 10. This is in contrast to traditional liquid development where the liquid developer has a comparatively low concentration of particles before development and where excess liquid is removed from the image before transfer from the photoconductor. It is also in contrast to U.S. Patent 4,504,138, in which the toner supplied to the drum is more concentrated, but where excess liquid must still be removed from the image before transfer to the final substrate.
• the toning material developed onto drum 10 is at a solids concentration substantially equal to that of the image transferred from the drum. Since the toner supplied during development to surface 21 of developer roller 22 is generally not sufficiently concentrated, the toner on surface 21 is further concentrated before contact with drum 10, for example by mechanical and electrical squeegeeing as described below with reference to Fig. 4. In addition to the details of the imaging methods and apparatus given above, additional details of imaging processes and devices are given in the patents and publications incorporated herein by reference. Reference is now made to Fig. 4 which schematically illustrates the construction and operation of developer assembly 23.
• Developer assembly 23 may be a f ixed component within the imaging apparatus or , alternatively , assembly 23 may take the f orm of a replaceable cartridge (not shown) which is readily inserted into the housing of the imaging apparatus and removed therefrom when the supply of liquid toner concentrate has been depleted.
• assembly 23 preferably includes a housing 60 having a toner inlet 62 and a toner outlet 64 which are associated with toner reservoir 65.
• the liquid toner in reservoir 65 contains up to 8 percent charged toner particles , preferably 1 . 8-2 percent , and carrier liquid .
• Fresh liquid toner from container 65 is preferably pumped via toner inlet 62 into an inlet chamber 63 of assembly 23 by a pump (not shown ) , and unused toner is returned from housing 60 to reservoir 65 via toner outlet 64.
• assemblies 23A- 23D o f mult i -color development assembly 63 are associated with respective reservoirs 65A- 65D , each reservoir containing a different color toner.
• developer roller 22 which is mounted within housing 60 , is preferably composed of any suitable electrically conducting material and has a surface composed of a soft polyurethane material , preferably made more electrically conductive by the inclusion of conducting additives .
• roller 22 has a small diameter , desirably less than 4 cm and preferably approximately 30 millimeters .
• developer rol ler 22 includes a metal core , having a diameter of approximately 26 millimeters , coated with a 1 . 95 mil limeter layer of polyurethane having a Shore A hardness of 20.
• the polyurethane layer is preferably coated with a 4-5 micrometer layer of a conductive lacquer which also extends along the sides of roller 22 so as to be electrically connected to the metal core .
• the conductive lacquer preferably includes three parts H322 (Lord Corporation, U.S.A.
• roller 22 protrudes somewhat from the opening of housing 60 such that, when assembly 23 is installed in the imaging apparatus, surface 21 of roller 22 is in contact with photoconductive surface 16 of drum 10.
• roller 22 is electrically charged, preferably to a negative voltage of 300-600 volts, for example -400 volts, and is rotated in the direction indicated by arrow 13.
• a layer of highly concentrated liquid toner is deposited on surface 21 of roller 22, as described below, and thus, roller 22 functions as a developer roller with regard to latent images formed on photoconductive surface 16 of drum 10, as described above with reference to Fig. 1.
• the pressurized toner received via inlet 62 is deposited on developer roller 22 by a depositing electrode 70 which forms one wall of inlet chamber 63.
• the opposite wall 72 of inlet chamber 63 is preferably formed of an insulating material, for example a plastic insulator, and is juxtaposed with surface 21 by a distance of approximately 0.5 millimeters.
• Electrode 70 which is preferably charged to a negative voltage of 900-2000 volts, for example -1400 volts, is preferably situated juxtaposed with a portion of developer roller 22, preferably at a distance of approximately 400 micrometers therefrom.
• the large difference in voltage between electrode 70 and developer roller 22 causes toner particles to adhere to developer roller 22, while the generally neutral carrier liquid is generally not affected by the voltage difference.
• the deposited liquid toner is carried by surface 21 of roller 22 in the direction indicated by arrow 13.
• the layer of liquid toner deposited on surface 21 is preferably at a concentration of 15-17 percent as described below.
• assembly 23 includes a squeegee roller 66 and a cleaning roller 74 which are mounted within housing 60 in contact with the surface of developer roller 22.
• Rollers 66 and 74 are composed of any suitable electrically conducting material , preferably metal , having a smooth surface .
• the diameters of squeegee roller 66 and cleaning roller 74 are preferably significantly smaller than that of developer roller 22 . Thus , if the diameter o f roller 22 is approximately 3 centimeters , the diameters of rollers 66 and 74 are preferably approximately 10 millimeters.
• rollers 66 and 74 are electrically charged and are caused to rotate in a sense opposite that of roller 22, as indicated by arrows 67 and 73 , while being urged against the resilient surface of roller 22.
• squeegee roller 66 is charged to a negative voltage of 400- 800 volts , pref erably approximately - 600 volt s
• cleaning roller 74 is preferably charged to a negative voltage of 0-200 volts .
• Squeegee roller 66 is preferably urged against roller 22 , at a pressure of approximately 100 grams per centimeter o f l ength , by means o f a lea f spring 68 , pref erably extending along substantially the entire length of the squeegee roller and having a, preferably teflon, tip which engages the surface of roller 66.
• the tip is preferably formed with grooves in the direction of motion of the surface of roller 66 which prevent accumulation of toner between roller 66 and spring 68 by allowing draining of the toner therefrom. Alternatively as shown in Fig .
• the leaf spring includes a wire, preferably of a low friction material such as teflon, wrapped around the leaf as around a core to form a flat coil with an axis along the length of the squeegee roller .
• the wires are spaced in the winding direction so that they contact the squeegee roller only along discrete portions or points along its length so that the above described draining of toner may occur.
• the spring is formed with spaced winding grooves to position the wire and stabilize its position.
• Squeegee roller 66 is operative to squeegee excess carrier liquid from surface 21 of developer roller 22, thereby to further increase the concentration of solids on surface 21.
• squeegee roller 66 Because of the squeegee action at the region of contact between resilient surface 21 and the surface of squeegee roller 66, a large proportion of the carrier liquid contained within the toner concentrate is squeezed out of the layer, leaving a layer having a solids concentration of 20 percent or more as described below.
• the excess carrier liquid which may include a certain amount of toner particles, drains towards toner outlet 64.
• the ends of squeegee roller 66 and roller 22 are formed with matching chamfered ends to reduce the effects of end overflow. Such chamfered rollers are described more fully in a PCT application titled "Squeegee roller for Imaging Systems" which corresponds to Israel application 111441, filed October 28, 1994.
• Cleaning roller 74 by virtue of the relatively low voltage to which it is charged, is operative to remove residual toner from surface 21 of developer roller 22.
• the toner collected by roller 74 is then preferably scraped off roller 74 by a, preferably resilient, cleaning blade 76 which is urged against the surface of roller 74.
• the scraped toner is preferably absorbed by a sponge roller 78, which is urged against roller 74 so as to be slightly deformed thereby, preferably by approximately 1.5 millimeters radially.
• Sponge roller 78 rotates in the same sense as that of roller 74, such that the surfaces of rollers 74 and 78 move in opposite directions at their region of contact. Sponge roller 78 also absorbs some of the excess liquid toner from the deposition region between electrode 70 and roller 22, mainly including carrier liquid, which is drained along the external surface of insulator wall 72 of chamber 63. Roller 78 preferably has a diameter of approximately 20 millimeters and is preferably formed of open-cell polyurethane surrounding a metal core having a diameter of approximately 8 millimeters.
• the layer deposited on surface 21 of roller 22 has a very high solids concentration, preferably greater than about 15 percent and typically between 15 and 17 percent, depending on which color toner is deposited. This concentration is much higher than the initial concentration of solids supplied to inlet 62 from reservoir 65, which concentration is generally lower than 8 percent solids and typically between 1.8 and 2 percent solids.
• Squeegeeing of the deposited layer of toner by squeegee roller 65 further increases the concentration of solids in the toner layer to approximately 20-50 percent solids, depending on the color of the toner. This high concentration has been found to be almost dry to the touch, non-flowing and crumbly in texture. It has also been found that the quality of the developed latent image is enhanced greatly as a result, and no additional drying mechanism is needed when the image is transferred to final substrate 42. Since so much liquid has been removed from the layer, a thickness of 2-8 micrometers on surface 21 of roller 22 is sufficient.
• portions of the layer of the dry to the touch liquid toner concentrate are selectively transferred to surface 16 of drum 10, thereby developing the latent image as explained above. After portions of the layer of toner concentrate have 1 been transferred to surface 16 of drum 10 to develop the
• roller 22 continue to rotate on surface 21 until they
• the oil temperature in the heating unit is set to 300 ⁇ F.
• the oil temperature in the heating unit is set to 300 ⁇ F.
• RV6803 pigment by Mobay
• the diluted toner is then mixed at approximately 150 RPM for approximately 2 hours.
• CONCENTRATION Black, Yellow, Magenta and Cyan Toners The magnetically treated toner is placed in a vacuum nutcha, such as a Buchner Funnel, having a polypropylene cloth support, and is concentrated using a vacuum pump. The toner concentration exceeds 22% solids after approximately 4 hours of pumping.
• CHARGING Black, Yellow, Magenta and Cyan Toners The concentrated toner is placed in a planetary mixer. A predetermined amount of charge director is added, preferably approximately 9 milligrams charge director per gram of toner solids. The toner concentration is adjusted, using Isopar-L, to approximately 20% solids.
• the toner is then pumped into 380 gram containers using a gear pump system.
• a variety of charge directors known in the art are operative in this embodiment of the invention.
• a preferred charge director for the present invention preferably utilizing lecithin, BBP and ICIG3300B, is described in U.S. Patent Application 07/915,291 and in P.C.T. Publication W.O. 94/02887.
• each toner concentrate is diluted by a predetermined amount of carrier liquid.
• the toner is generally diluted with Isopar-L type carrier liquid but may additionally include 1-2 percent of Marcol-82.
• the carrier liquid may be at least partially replaced by a grease or petroleum which has a high viscosity and is thixotropic, thereby reducing leaks.
• Fig. 5 schematically illustrates a preferred embodiment of web-feeder system 100
• Fig. 6 schematically illustrates, in block diagram form, a preferred circuit for controlling the operation of web-feeder system 100.
• Fig. 8 schematically illustrates a preferred sequence of operation of web-feeder system 100.
• web-feeder system 100 includes first and second impression rollers 39 and 41 which are alternatively applied to support final substrate 42 against the surface of ITM 40 at regions 239 and 241, respectively.
• first and second impression rollers 39 and 41 which are alternatively applied to support final substrate 42 against the surface of ITM 40 at regions 239 and 241, respectively.
• a first surface 101 of substrate 42 engages ITM 40 when roller 39 is urged against the ITM
• a second, opposite surface 103 of substrate 42 engages ITM 40 when roller 41 is urged against the ITM.
• This arrangement enables imaging on both surfaces 101 and 103 of substrate 42 using a single imaging apparatus, wherein ITM 40 engages surfaces 101 and 103 in accordance with a predetermined imaging sequence, as described below.
• Rollers 39 and 41 are driven by impression motors 158 and 160, the operation of which is controlled by a controller 150.
• Substrate 42 which may be formed of paper or any other suitable material, is preferably a continuous web supplied from a web-dispenser roll 102, through a substrate input arrangement which preferably includes input roller 104 and 105. Input rollers 104 and 105 are preferably driven by an input motor 152, the operation of which is controlled by controller 150 as described below. It should be appreciated that first surface 101, as defined above, is the top surface of continuous substrate 42 when the substrate is between rollers 104 and 105. The dispensed continuous web 42 is guided to a first free-loop arrangement 107, having maximum height detectors 106 and minimum height detectors 108 associated with controller 150.
• Detectors 106 are activated when the loop of substrate 42, dispensed into arrangement 107, is above a predetermined maximum height, while detectors 108 are activated when the loop of substrate 42 in arrangement 107 is below a predetermined minimum height.
• controller 150 activates motor 152 so as to dispense more of web 42 from dispenser 102 into loop arrangement 107, thereby to lower the loop in arrangement 107.
• controller 150 deactivates motor 152 so as to stop dispenser 102 from dispensing web 42 into loop arrangement 107, thereby to raise the loop in arrangement 107. In this manner, the length of substrate 42 in loop arrangement 107 is maintained within a predetermined length range which allows sufficient timing flexibility during imaging.
• Continuous web 42 is pulled out of free loop arrangement 107, via a support roller 110, by a collection arrangement which preferably includes tension rollers 112 and 113. Rollers 112 and 113 are preferably driven by a 1 tension motor 154 which is controlled by controller 150.
• Motor 154 is preferably a torque motor operative for
• impression roller 39 which is
• a preselected post- 29 image mark i s imprinted on surf ace 101 immediately
• web 42 is partial ly
• detector 114 is preferably operative only within preset detection time windows, during which time controller 150 queries for a detection signal.
• the time gaps between consecutive detection time windows are preferably set in accordance with the page layout of the respective first surface images.
• the first surface images are reproduced with a minimal spacing, preferably not more than a few millimeters, whereby the post-image marks are imprinted within the boundaries of the spacings.
• the images on ITM roller 40 are preferably bottom-justified, such that a substantially constant spacing is maintained between images.
• pre-image marks may be used rather than post-image marks and, in such an embodiment, the images on the surface of ITM 40 are preferably top-justified.
• Web 42 bearing images on first surface 101 thereof, then passes through indexing rollers 116 and 117 which are, preferably, driven by first indexing motor 158.
• Indexing motor 158 communicates with controller 150 and is operative, together with motor 156, to advance web 42 in accordance with the first surface imaging cycles, i.e. for a specified length of web 42 after each First Image Trigger signal generated by controller 150.
• the velocity and relative position of web 42 during each first surface imaging cycle are preferably monitored by controller 150 through an encoder which is preferably associated with rollers 116 and 117.
• Detectors 118 are activated when the loop of substrate 42 dispensed into arrangement 119 is above a predetermined maximum height, while detectors 120 are activated when the loop of substrate 42 in arrangement 119 is below a predetermined minimum height.
• controller 150 activates a second tension motor 160 which drives second tension rollers 124 and 125, downstream of loop arrangement 119, to collect web 42 from loop arrangement 119 thereby to raise the loop in arrangement 119.
• controller 150 deactivates motor 160 so as to stop tension rollers 124 and 125 from collecting web 42 from loop arrangement 119, thereby to lower the loop in arrangement 119. In this manner, the length of substrate 42 in loop arrangement 119 is maintained within a predetermined length range which allows sufficient imaging timing flexibility.
• Motor 160 is preferably a torque motor which maintains a substantially constant tension in web substrate 42, downstream of rollers 124 and 125, during operation of the web-feeder system.
• Web 42 is preferably collected from second loop arrangement 119 via a support roller 122 similar to support roller 110.
• Figs. 7A and 7B schematically illustrates inversion of continuous substrate 42 in accordance with a preferred embodiment of the present invention.
• substrate 42 is "folded" three times, about three respective axes. For example, substrate 42 may be folded, first, about a 45 degree axis 170, then, about an axis 172 parallel to the advance of substrate 42 and, finally, about another 45 degree axis 174.
• inverter 130 may be equally suitable for inverting the surfaces of substrate 42 as described above, for example a Mobius belt arrangement wherein the substrate is inverted by being gradually rotated about its longitudinal axis while being advanced.
• the arrangement of Figs. 7A and 7B has been found to be effective in operation and economic in space.
• web 42 Downstream of inverter mechanism 130, web 42 is directed around a support roller 126 towards impression roller 41, passing a second detector 128 which is operative for detecting the post-image synchronization marks imprinted between the images on surface 101.
• Impression roller 41 is driven by a second impression motor 162, which is activated by controller 150 in accordance with the predetermined imaging sequence.
• impression roller 41 is urged against the surface of ITM 40 only when second surface 103 of web 42 is to be imaged according to the imaging sequence.
• each period of engagement between surface 103 with ITM 40 i.e. each second surface imaging cycle, is initiated by a Second Image Trigger signal from controller 150.
• web 42 is accelerated by motor 162 and by a second indexing motor 164 which is described below, until the velocity of surface 103 is comparable with the surface velocity of ITM 40. This allows position controlled, slip-free, engagement between surface 103 and ITM 40 during imaging on the second surface.
• web 42 is rewound , preferably by reverse operation of motors 160, 162 and 164, after each second surface imaging cycle. This provides the length of web necessary for subsequent reacceleration of web 42 for the next second surface imaging cycle.
• Correct positioning of a given second surface image is enabled by detection of the post-image mark of the preceding first surface image, so as to accurately position the given second surface image opposite its corresponding image on surface 101.
• detector 128 is preferably operative only within preset detection time windows, during which time controller 150 queries for a detection signal therefrom. The time gaps between consecutive detection time windows are preferably the same as those of the respective first surface images.
• time gaps are preferably calculated by controller 150 based on the substrate length of the corresponding images, as measured by the encoders associated with indexer rollers 116 and 117. It is appreciated that in order to maintain the minimal spacing between images, as described above, the page layout of each image on surface 103 is preferably the same as that of the corresponding image on surface 101.
• the second surface images are preferably bottom-justified on ITM 30, as described above regarding the first surface images.
• Web 42 which now bears a series of images on first surface 101 and a corresponding series of images on opposite surface 103, is guided by a roller 132 and then passes through a second indexing rollers 134 and 135 which are preferably driven by second indexing motor 164.
• Indexing motor 164 communicates with controller 150 and is operative together with motor 160, to advance web 42 in accordance with the second surface imaging cycles, i.e. for a specified length of web 42 after each Second Image Trigger signal generated by controller 150.
• the velocity and relative position of web 42 during each second surface imaging cycle are preferably monitored by controller 150 through an encoder which is preferably associated with rollers 134 and 135. Downstream of indexing rollers 134 and 135 , continuous web 42 is guided into a third free-loop arrangement 137 , having maximum height detectors 136 and minimum height detectors 138 associated with controller 150.
• Detectors 136 are activated when the loop of substrate 42 dispensed into arrangement 137 is above a predetermined maximum height
• detectors 138 are activated when the loop of substrate 42 in arrangement 137 is below a predetermined minimum height
• controller 150 activates an output motor 166 which drives output rollers 142 and 143, downstream of a support roller 140, to collect web 42 from loop arrangement 137 thereby to raise the loop in arrangement 137.
• controller 150 deactivates motor 166 so as to stop output rollers 142 and 143 from collecting web 42 from loop arrangement 137 , thereby to deepen the loop in arrangement 137.
• the length of substrate 42 in loop arrangement 137 i s maintained wi thin a predetermined length range which allows sufficient imaging timing flexibility.
• the double-sided image bearing substrate 42 exiting output rollers 142 and 143 is then cut between images by a cutter 146 , as known in the art .
• a third detector 144 is provided between rollers 142 and 143 and cutter 146 for detecting the post - image marks imprinted between the images on surface 101 .
• the position of substrate 42 relative to cutter 146 is adj usted by controlled operation of output motor 146 based on the detection signal s f rom third detector 144 to controller 150.
• detector 144 is preferably operative only within preset detection time windows , during which time controller 150 queries for a detection signal therefrom .
• the time gaps between consecutive detection time windows are preferably the same as those of the respective f irst and second surface images .
• These time gaps are preferably calculated by controller 150 based on the substrate length of the corresponding images , as measured by the encoders associated with indexer rollers 134 and 135.
• eight motors are involved in the operation of the web- feeder system, namely, motors 152 , 154 , 156 , 158 , 160 , 162 , 164 and 166 .
• motors 152-164 are brushless servo-motors driven by a plurality of corresponding digital servo-drivers (not shown) , as known in the art .
• the predetermined imaging sequence may be as follows . First , a predetermined number of images are reproduced on first surface 101 to account for the length of continuous substrate 42 separating between first impression roller 39 and second impression roller 41. Then, ITM 40 is alternatingly engaged by surfaces 101 and 103 such that each first surface imaging cycle is followed by a second surface imaging cycle.
• the present invention provides an initiation procedure for synchronizing between the first surface imaging cycles, the second surface imaging cycles and the cutting of substrate 42.
• imaging begins with substrate 42 being at a "stretched-out" configuration, wherein substrate 42 is stretched across loop arrangements 119 and 137, i.e. extends directly from indexers 116 and 117 to roller 122 and from indexers 134 and 135 to roller 140. It should be appreciated that in this configuration, the length of substrate 42 between impression regions 239 and 241 and the length of substrate 42 between region 241 and cutter 146 are both well defined.
• a plurality of first surface images are then produced on surface 101, as described above, and controller 150 keeps track of the length of substrate 42 passing through impression region 239, for example by measuring the length of substrate passing through indexer rollers 116 and 117. This length may be added to the known length of the stretched substrate between regions 239 and 241.
• the advance of substrate 42 through region 239 results in deepening of the loop of substrate in loop arrangement 119, until minimum height detectors 120 are activated as described above.
• substrate 42 starts to advance also through impression region 241, and the length of this advance is monitored by controller 150 using indexer rollers 134 and 135.
• the length of substrate 42 between regions 239 and 241 is monitored by controller 150 by subtracting the length measured at indexers 134 and 135 from the length measured at indexer 116 and 117. Based on this information, controller 150 synchronizes between the detection time windows of the first surface imaging cycles and the corresponding detection windows of the second surface imaging cycles.
• controller 150 synchronizes between the detection time windows of the first surface imaging cycles and the corresponding detection windows of the second surface imaging cycles.
• the advance of substrate 42 through region 241 results in deepening of the loop of substrate in loop arrangement 137, until minimum height detectors 138 are activated as described above. At this stage, substrate 42 starts to 1 advance also through cutter 146.
• controller 150 by adding the length measured at indexers
• controller 150 synchronizes between the

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• 1995
  • 1995-04-03 IL IL113235A patent/IL113235A/en not_active IP Right Cessation
  • 1995-06-06 AU AU25795/95A patent/AU2579595A/en not_active Abandoned
  • 1995-06-06 JP JP53020296A patent/JP3685337B2/ja not_active Expired - Fee Related
  • 1995-06-06 DE DE69536043T patent/DE69536043D1/de not_active Expired - Lifetime
  • 1995-06-06 EP EP95920301A patent/EP0819269B1/en not_active Expired - Lifetime
  • 1995-06-06 WO PCT/NL1995/000199 patent/WO1996031809A1/en active Application Filing
• 2005
  • 2005-03-07 JP JP2005062972A patent/JP3890348B2/ja not_active Expired - Fee Related

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