Patent Publication Number: US-6993272-B2

Title: Method of development of custom colors without changing developer housing

Description:
This application claims the benefit of Provisional Patent Application No. 60/424,645, filed Nov. 7, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to a development apparatus for ionographic or electrophotographic imaging and printing apparatuses and machines, and more particularly is directed to a developer apparatus for providing custom colored marking particles. 
     Customer selectable colors are typically utilized to provide instant identification and authenticity to a document. As such, the customer is usually highly concerned that the color meets particular color specifications. For example, the red color associated with Xerox&#39; digital stylized “X” is a customer selectable color having a particular shade, hue and color value. Likewise, the particular shade of orange associated with Syracuse University is a good example of a customer selectable color. A more specialized example of customer selectable color output can be found in the field of “custom color”, which specifically refers to registered proprietary colors, such as used, for example, in corporate logos, authorized letterhead, and official seals. The yellow associated with Kodak brand products, and the brown associated with Hershey brand products are good examples of custom colors which are required to meet exacting color standards in a highlight color or spot color printing application. 
     The various colors typically utilized for standard highlighting processes generally do not precisely match customer selectable colors. Moreover, customer selectable colors typically cannot be accurately generated via halftone process color methods because the production of solid image areas of a particular color using halftone image processing techniques typically yields nonuniformity of the color in the image area. 
     Further, lines and text produced by halftone process color are very sensitive to misregistration of the multiple color images such that blurring, color variances, and other image quality defects may result. As a result of the deficiencies noted above, customer selectable color production in electrostatographic printing systems is typically carried out by providing a singular premixed developing material composition made up of a mixture of multiple color toner particles blended in preselected concentrations for producing the desired customer selectable color output. This method of mixing multiple color toners to produce a particular color developing material is analogous to processes used to produce customer selectable color paints and inks. In offset printing, for example, a customer selectable color output image is produced by printing a solid image pattern with a premixed customer selectable color printing ink as opposed to printing a plurality of halftone image patterns with various primary colors or compliments thereof. 
     This concept has generally been extended to electrostatographic printing technology, as disclosed, for example, in commonly assigned U.S. Pat. No. 5,557,393, wherein an electrostatic latent image is developed by a dry powder developing material comprising two or more compatible toner compositions which have been mixed together to produce a customer selectable color output. Customer selectable color printing materials including paints, printing inks, and developing materials can be manufactured by determining precise amounts of constituent basic color components making up a given customer selectable color material, providing precisely measured amounts of each constituent basic color component, and thoroughly mixing these color components. 
     This process is commonly facilitated by reference to a color guide or swatch book containing hundreds or even thousands of swatches illustrating different colors, wherein each color swatch is associated with a specific formulation of colorants. Probably the most popular of these color guides is published by PANTONE®, Inc. of Moonachie, N.J. The PANTONE® Color Formula Guide expresses colors using a certified matching system and provides the precise formulation necessary to produce a specific customer selectable color by physically intermixing predetermined concentrations of up to four colors from a set of up to 18 principal or basic colors. There are many colors available using the PANTONE® system or other color formula guides of this nature that cannot be produced via typical halftone process color methods or even from mixing selected amounts of cyan, magenta, yellow and/or black inks or developer materials. 
     In the typical operational environment, an electrostatographic printing system may be used to print various customer selectable color documents. To that end, replaceable containers of premixed customer selectable color developing materials corresponding to each customer selectable color are provided for each print job. 
     Replacement of the premixed customer selectable color developer materials or substitution of another premixed color between different print jobs necessitates operator intervention which typically requires manual labor and machine downtime, among other undesirable requirements. In addition, since each customer selectable color is typically manufactured at an off-site location, supplies of each customer selectable color printing ink must be separately stored for each customer selectable color print job. 
     SUMMARY OF THE INVENTION 
     There is provided a method for producing a toner of a custom color in a developer unit including a housing defining a reservoir for storing a supply of toner, a donor member for transporting toner to an imaging surface; comprising: identifying custom color requested; determining color of toner in the reservoir; detoning toner on said donor member if the color of toner in the reservoir is beyond a predefined value in color space from said custom color requested; calculating and dispensing primary toner colors to be added to the reservoir to obtained the custom color requested; mixing said primary toner colors dispensed in said reservoir; and evaluating and comparing the color components of said toner being mixed to said custom color requested. 
     There is also provided an apparatus for developing a latent image recorded on an imaging surface, comprising: a first developer unit for developing a portion of said latent image with a toner of a custom color, said first developer unit including a housing defining a reservoir for storing a supply of toner; a dispenser for dispensing toner of a first color and toner of a second color into said housing, said dispenser including means for mixing toner of said first color and toner of said second color together to form toner of said custom color; a donor member for transporting toner of said custom color on an outer surface of said donor member to a development zone; means for loading a toner layer of said custom color onto said outer surface of said donor member; a purging system, adjacent to said donor member, for detoning toner said donor member and said reservoir; and a color controller, in communication with said dispenser and purging system, for adjusting color components of said custom color. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic elevational view of an illustrative electrophotographic printing machine incorporating the present invention therein. 
         FIGS. 2 and 3  are a schematic illustration of the development system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE FIGURES 
     While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     Turning now to  FIG. 1 , the electrophotographic printing machine uses a charge retentive surface in the form of a photoreceptor belt  10 . The photoreceptor belt is supported by rollers  14 ,  16 ,  18 , and  20 . Motor  21  operates the movement of roller  20 , which in turn causes the movement of the photoreceptor in the direction indicated by arrow  12 , for advancing the photoreceptor sequentially through the various xerographic stations. 
     With continued reference to  FIG. 1 , a portion of photoreceptor belt  10  passes through charging station A where a corona generating device, indicated generally by the reference numeral  22 , charges the photoconductive surface of belt  10  to a relatively high, substantially uniform potential. For purposes of example, the photoreceptor is negatively charged, however it is understood that the present invention could be useful with a positively charged photoreceptor, by correspondingly varying the charge levels and polarities of the toners, recharge devices, and other relevant regions or devices involved in the image on image color image formation process, as will be hereinafter described. 
     Next, the charged portion of the photoconductive surface is advanced through an imaging and exposure station B. A document  30 , with a highlight color image and/or text original, is positioned on a raster input scanner (RIS), indicated generally by the reference numeral  33 . One common type of RIS contains document illumination lamps, optics, a mechanical scanning drive, and a charged coupled device. The RIS captures the entire image from original document  30  and converts it to a series of raster scan lines. Alternatively, image signals may be supplied by a computer network. This information is transmitted as electrical signals to an image processing system (IPS), indicated generally by the reference numeral  24 . IPS  24  converts image information into two colorant signals (i.e. black and the custom color). Alternatively, highlight color image and/or text original can be externally computer generated and sent to IPS to be printed. 
     The IPS contains control electronics which prepare and manage the image data flow to a raster output scanning device (ROS), indicated by numeral  34 . A user interface (UI) indicated by  26  is in communication with IPS  24 . UI  26  enables an operator to control the various operator adjustable functions such as selecting portion document to be printed with a custom color. 
     The operator actuates the appropriate keys of UI  26  to adjust the parameters of the copy. UI  26  may be a touch screen or any other suitable control panel providing an operator interface with the system. The output signal from UI  26  is transmitted to the IPS  24 . The IPS then transmits signals corresponding to the desired image to ROS  34 , which creates the output copy image. ROS  34  includes a laser with rotating polygon mirror blocks. The ROS illuminates, via mirror, the charged portion of a photoconductive belt  11 . The ROS will expose the photoconductive belt to record single to multiple images which correspond to the signals transmitted from IPS  24 . 
     The photoreceptor, which is initially charged to a voltage V 0 , undergoes dark decay to a level V ddp  equal to about −500 volts. When exposed at the exposure station B the image areas are discharged to V DAD  equal to about −50 volts. Thus after exposure, the photoreceptor contains a monopolar voltage profile of high and low voltages, the former corresponding to charged areas and the latter corresponding to discharged or image areas. 
     A first development station C, indicated generally by the reference numeral  100 , advances development material into contact with the electrostatic latent image. The development housing contains custom color toner and carrier. Appropriate developer biasing is accomplished via power supply. Electrical biasing is such as to effect discharged area development (DAD) of the lower (less negative) of the two voltage levels on the photoreceptor with the development material. This development system may be either an interactive or non-interactive system. 
     The photoconductive belt is recharged by corona device  31 . A second exposure or imaging device  43  which may comprise a laser based output structure is utilized for selectively discharging the photoreceptor on toned areas and/or bare areas to approximately −50 volts, pursuant to the image to be developed with the second color developer. After this point, the photoreceptor contains toned and untoned areas at relatively high voltage levels (e.g. −500 volts) and toned and untoned areas at relatively low voltage levels (e.g. −50 volts). These low voltage areas represent image areas which are to be developed using discharged area development. To this end, a negatively charged developer material comprising, for example, a black toner is employed. The toner is contained in a developer housing structure  44  disposed at a second developer station and is presented to the latent images on the photoreceptor. 
     The photoreceptor belt  10  then advances the developed latent image to transfer station D. At transfer station D, a sheet of support material such as paper copy sheets, is advanced into contact with the developed latent images on the belt  10 . A corona generating device  46  charges the copy sheet to the proper potential so that it becomes tacked to the photoreceptor belt  10  and the toner powder image is attracted from the photoreceptor belt  10  to the sheet. After transfer, the corona generator  48  charges the copy sheet to an opposite polarity to detack the copy sheet from the photoreceptor belt  10 , whereupon the sheet is stripped from the photoreceptor belt  10  at stripping roller  14 . 
     Sheets of support material  49  are advanced to transfer station D from a supply tray  50 . Sheets are fed from tray  50 , with sheet feeder  53 , and advanced to transfer station D along conveyor  56 . 
     After transfer, the sheet continues to move in the direction of arrow  60  to fusing station E. Fusing station E includes a fuser assembly indicated generally by the reference numeral  70 , which permanently affixes the transfer toner powder images to the sheets. Preferably, the fuser assembly  70  includes a heated fuser roller  72  adapted to be pressure engaged with a backup roller  74  with the toner powder images contacting the fuser roller  72 . In this manner, the toner powder image is permanently affixed to the sheet, and such sheets are directed via a chute  62  to an output  80  or finisher. 
     Residual particles, remaining on the photoreceptor belt  10  after each copy is made, are removed at cleaning station F. 
     A machine controller  96  is preferably a known programmable controller or combination of controllers, which conventionally control all the machine steps and functions described above. The controller  96  is responsive to a variety of sensing devices to enhance control of the machine, and also provides connection diagnostic operations to an user interface (not shown) where required. 
     It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine incorporating the development apparatus of the present invention therein. 
     Focusing on the development station C before describing the color mixing and control system of the present invention, in the exemplary developing apparatus of  FIG. 2 . Preferably developing apparatus employs MAZE (magnetically agitated zone) such as disclosed in U.S. Pat. No. 5,933,683 which is hereby incorporated by reference. Donor member  42  comprises an interior rotatable harmonic multiple magnetic assembly within a sleeve. The sleeve can be rotated in either the “with” or “against” direction relative to the direction of motion of the photoreceptor belt  10 . Similarly, the magnetic core can be rotated in either the “with” or “against” direction relative to the direction of motion of the sleeve developing material is transported from an supply sump  57  to the donor member  42  via a transport roll  51 . Supply sump  57  acts as a holding receptacle for providing an operative solution of developing material comprised of toner material and carrier, which, in the case of the customer selectable color application of the present invention, includes a blend of different colored marking particles on a common carrier. Preferably color marking particles are Emulsion Aggregation or Chemical Toners (EA) toners, but could be toner particles made from any variety of methods. 
     A plurality of replaceable supply dispensers p 1  through p n , each containing a concentrated supply of marking particles corresponding to a basic color component in a color matching system, are provided in association with the operational supply sump  57 . Housing  60  includes blender  62  blends the basic color component together which is then released into sump  57 . Augers  52  and  54  transport developer material to transport roll  51 . Housing  60  is removable from development station  100 . 
     In operation, the application of marking particles to the latent image, clearly depletes the overall amount of the operative solution of developing material in supply sump  57 . Therefore, sump  57  is continuously replenished, as necessary, by the addition of developing material or selective components thereof from dispensers  66 . Since the total amount of any one component making up the developing material utilized to develop the image may vary as a function of the area of the developed image areas and the background portions of the latent image on the photoconductive surface, the specific amount of each component of the developing material which must be added to the supply sump  57  varies with each development cycle. 
     For example, a print job having a developed image having a large proportion of printed image area will cause a greater depletion of marking particles from a developing material sump as compared to a print job having a developed image with a small amount of printed image area. 
     The replenishment system includes a plurality of differently colored developing material supply dispensers p1 through pn, each coupled to the operative supply sump. Preferably, each supply dispenser contains a developing material of a known basic or primary color such as Cyan, Magenta, Yellow and Black. In one specific embodiment, the replenishment system includes nine supply dispensers, wherein each supply container provides a different basic color developing material as described in U.S. Pat. No. 5,892,891. Mixtures of the nine basic or constituent colors emulate the color mixtures of the PANTONE® Color Matching System, which employs a set of eleven basic ink colors. 
     Color formulations, similar to those provided by the PANTONE® System can be utilized, as for example, by storage in a look up table, to produce thousands of desirable output colors and shades in a customer selectable color printing. Using this system, as few as two different color developing materials, from supply containers P 2  and P 3  for example, can be combined in sump  57  to expand the color gamut of customer selectable colors far beyond the colors available via half tone imaging techniques. An essential component of the developing material color mixing and control system is a color control system. 
     An advantageous feature of the present invention is the toner purging station  200 . This toner purging station  200  allows for a quicker color change over for new print jobs requiring a new custom color substantially different from the prior job without removing the development housing. Further, the carrier is left in the development housing and is reused with the next custom mixed color toner. The toner for this invention is preferably triboelectrically compatible across each of the 9 color pigments that have been identified as needed to emulate the Pantone color set. This invention allows for the reuse of carrier, is attractive from a Total Cost of Ownership, and environmental waste reduction standpoint. 
     Toner purging station  200  is within development housing. However toner purging can be remote from the printing. Toner purging station  200  includes a receiver roll  202  and a cleaning device  204  to clean receiver roll  202 . Receiver roll  202  includes a conductive roll such as anodize aluminum. A cam assembly (not shown) moves receiver roll  202  in to operative position adjacent to donor member  42 . The operative position can be in contact with receiver roll  202  or be closely spaced therefrom, so that the toner bed height of the donor roll is about 0.010 to 0.020 inches from the receiver roll. A power supply (not shown) is electrically connected to receiver roll  202  and applies an electrical bias. The electrical bias is setup on the housing such that the development field is very strong, to allow for the rapid purging of the toner from the carrier. The receiver roll functions as a toner collector that is then cleaned by cleaning device  204 . Cleaning device  204  includes cleaning means such as a blade  205  or brush to clean toner from surface of receiver roll  202 . Cleaning device also includes a toner transport auger  206  for transporting the removed toner to a waste or reclaim container (not shown). 
     In operation of toner purging, receiver roll  202  is cammed into operative position adjacent to donor member  42 . Development system parameter is changed from a printing mode to a purging mode. In the purging mode, development parameter is changed to obtained the maximum toner output from supply sump  57  employing donor member  42 , and a transport roll  51 . This can be achieved by increasing speed of donor member  42  and a transport roll  51  and adjusting the bias applied to donor member  42  and a transport roll  51 . The purging station is run until the development housing is sufficiently stripped of toner. Depending on the change in hue, saturation and lightness between the purged color and the replacement color, the purged carrier must be stripped to a predefined TC, (for eg. &lt;0.5% TC) to avoid visible cross contamination of colors. At this point, the carrier is ready to be retoned by the introduction of the new custom color that needs to be printed. The toner mixture comprising the new custom color toner can be dispensed into the housing as a single pre-measured color mixture. Alternatively, the new custom color toner mixture can be measured and blended in situ by dispensing the appropriate ratio of each of the required basic toner colors either in parallel or sequentially. 
     The principles of the present invention have been tested, wherein a development housing was run in the configuration shown in  FIG. 2  with a 800 gram cyan EA developer package with no additives. Initially the material had a tribo around 30 μC/g and a TC of 8.7%. After 5.5 minutes of stripping by a receiver roll, the resulting material properties revealed a tribo of around 130 μC/g and TC of 0.47%. The housing was then run for an additional 2 minutes, but there was no further change in the material properties. This indicates that in a very short amount of time a complete 800 gram developer package can be stripped of its toner. 
     One embodiment of this invention is to use the photoreceptor itself as the toner receiver for purging toner; the internal cleaning system could remove the stripped toner. This would stress the capacity of the cleaning system, but it could be overcome. One possible solution is the addition of a secondary cleaning system for detoning operations that could allow for the recycling and reuse of the toner. An alternate embodiment is to use a stand alone toner purging station with or without an integrated toner dispensing system for re-toning the stripped carrier. The station is available for servicing color changeovers for several development housings for a single printing machine or a fleet of machines. 
     Another advantageous feature of the present invention is that it can be employed with a customer selectable color mixing controller  142 . Customer selectable color mixing controller is provided in order to determine appropriate amounts of each color developing material in supply containers P 1  through Pn to be added to supply sump  57  to achieve the custom color, and to controllably supply each of such appropriate amounts of developing material. 
     Controller  142  may take the form of any known microprocessor based memory and processing device, as are well known in the art. The approach provided by the color mixing control system includes a sensing device  76  and  77 , an optical sensor for monitoring the output color of the developer layer on donor member  42  and receiver roll  202 , sensors  73  and  77  monitoring the output color on the donor member, photoconductive surface, and fused paper sheet, respectively. A toner concentration sensor  75  used in conjunction with a pixel counter. These sensors are connected to controller  142  for providing sensed color information thereto, which, in turn is used for controlling the flow of the variously colored replenishing developing materials from dispensers. The colored developing materials in dispensers correspond to the basic constituent colors of a color matching system, and are selectively delivered into the developing material supply sump  57  from each of the supply containers to produce the customer selectable color output image. 
     In operation, the UI  26  can indicate to the operator “please wait adjusting color” when a new custom color is requested (say red color associated with Xerox&#39; digital stylized “X”). Purging station is engaged for a short period of time for controller  142  to take data from sensor  76  to read the color within the housing. Then controller  142  compares new color with previous color printed by the housing  60 . If the new custom color is within the pre-set value color space value then the housing (say housing having reddish colorant) then the purge mode is not activated. Next, customer selectable color mixing controller  142  determines the appropriate amounts of each color developing material in supply containers P 1  through Pn to be added to supply sump  57  to achieve the new required custom color from the reddish colorant. 
     If custom color is outside the preset value color space (say housing having bluish colorant) then the purge mode is activated. The purging station is run until the development housing is sufficiently stripped of toner. At this point, the carrier is ready to be retoned by the introduction of the new custom color. Next, customer selectable color mixing controller  142  determines the appropriate amounts of each color developing material in supply containers P 1  through Pn to be added to supply sump  57  to achieve the new required custom color. 
     In recapitulation there has been provided a method for producing a toner of a custom color in a developer unit including a housing defining a reservoir for storing a supply of toner, a donor member for transporting toner to an imaging surface; including identifying custom color requested; determining color of toner in the reservoir; detoning toner on said donor member if the color of toner in the reservoir is beyond a predefined value in color space from said custom color requested; calculating and dispensing primaries toner colors to be added to the reservoir to obtained the custom color requested; mixing said primary toner colors dispensed in said reservoir; and evaluating and comparing the color components of said toner being mixed to said custom color requested. Wherein said evaluating and comparing comprises: sensing color components of said toner being mixed in said reservoir with a first sensor; detoning toner on said donor member; and sensing color components of said toner being detoned with a second sensor; and repeating said calculating and dispensing in response to said sensing until color components of said toner being mixed to said custom color requested are within a predefined value in color space. 
     Other embodiments and modifications of the present invention may occur to those skilled in the art subsequent to a review of the information presented herein; these embodiments and modifications, as well as equivalents thereof, are also included within the scope of this invention.