Abstract:
A method for filling a developer station for an electrophotographic printer includes mixing or transporting developer in a sump with an auger; driving the auger with a motor; measuring a speed of the motor or a torque applied by the motor or power used by the motor; sending speed, torque, or power information to a filling mechanism for filling the sump with developer; and stopping or reducing the flow of developer into the sump when the speed, torque, or power reaches a predetermined setting.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly-assigned copending U.S. patent application Ser. No. ______ (Attorney Docket No. 96476US01/NAB), filed herewith, entitled SPEED OR TORQUE TO FILL DEVELOPER STATION, by Rapkin et al.; the disclosure of which is incorporated herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates in general to electrophotographic printers and in particular to filling a developer station for an electrophotographic printer. 
       BACKGROUND OF THE INVENTION 
       [0003]    In dual component electrophotographic printers, the developer station requires a precise fill amount of developer (toner and magnetic carrier). This is often accomplished in the factory through the use of premeasured packets. This process is similar to the means used in the field by service personnel, however, the use of premeasured packets requires additional packaging and as a result, additional cost over the use of filling from a bulk reservoir. 
         [0004]    The problem with filling from a bulk reservoir is insuring that the correct amount of developer is added. A typical means used to control the amount added is the weighing of the station before and after the developer is added. The disadvantage of this method is that the addition of developer requires some manipulation or running of the station which interferes with the accurate measurement of the filling load. 
         [0005]    Using prefilled and premeasured packets of developer is time consuming as each packet must first be obtained and opened prior to filling the development station. The packets must first be produced. This requires metering and measuring the correct amount of developer for each packet, filling the packet, sealing the packet, and labeling the packet. It is obvious that the use of packets generates waste in the form of the emptied packets after use that must be processed. 
         [0006]    While using packets of premixed developer may be beneficial in the field when servicing a dry electrophotographic print engine, it is not efficient to use such packets in a factory environment. Rather, it is preferable to fill the development station from a bulk supply of developer. Generally, the development station is filled until a specified weight of developer has been deposited into the development station, generally in a sump within the development station designed to hold, mix, and transport the developer. 
         [0007]    A standard manner of loading a development station in a factory is to weigh the amount of developer being added to the station. This generally requires that the amount of developer be taken from a bulk supply and weighed until the proper weight is obtained. The developer is then added to the station. Alternatively, a development station can be weighed before and during the adding process until the desired amount of developer has been added. However, this generally requires that the addition of developer be stopped while weighing is in progress. In addition, if too much developer is added, removal of the excess developer is problematic. 
         [0008]    It is clear that a more cost effective, less time consuming method of loading precise quantities of developer into a dry electrophotographic development station is needed. 
       SUMMARY OF THE INVENTION 
       [0009]    This invention provides for an improved method and apparatus for loading a two-component developer into a dry magnetic electrophotographic development station. The method and apparatus include a system for filling a developer station for an electrophotographic printer including a sump containing developer; an auger in the sump to transport the developer; a shaft on the auger to drive the auger; a motor to drive the shaft of the auger; a mechanism for measuring speed or torque of the motor; a feedback mechanism; a filling mechanism for filling the sump with developer; and wherein filling is stopped or reduced when the speed or the torque reaches a predetermined setting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a typical dry electrophotographic printer suitable for use with this invention. 
           [0011]      FIG. 2  shows a dry electrophotographic development station containing an inlet for developer and an ammeter for measuring the power needed to drive an auger. 
           [0012]      FIG. 3  shows a dry electrophotographic development station containing an inlet for developer and a slip clutch that regulates a valve for metering developer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    The present invention will be directed in particular to elements forming part of, or in cooperation more directly with the apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.  FIG. 1  shows an electrophotographic (EP) printer  20  having a print engine  22  for recording toner images on an intermediate transfer member (ITM)  30  and an intermediate transport system  32  with at least one intermediate transport motor  34  for moving ITM  30  past print engine  22  and to a transfer nip  40 . The print engine forms a multi-toner image on intermediate transfer member  30  as it is moved past print engine  22 . A receiver transport system  42  moves a receiver  44  along a path  48  from a receiver source  46  through transfer nip  40  so the multi-toner image is transferred from ITM  30  to receiver  44 . Receiver transport system  42  then moves receiver  44  and the transferred multi-toner image through a fuser  60  to fuse, fix, or sinter the transferred multi-toner image to receiver  44 . 
         [0014]    EP printer  20  is controlled by a printer controller  82  which can take the form of a microprocessor, microcontroller, or other such device and appropriate sensors of conventional design. EP printer  20  is shown having dimensions of A×B which are around in one example, 52×718 mm or less, however, it will be appreciated that such dimensions are exemplary and are not limiting. 
         [0015]    As is shown in the embodiment of  FIG. 1 , print engine  22  has a plurality of electrophotographic modules  24 A,  24 B,  24 C,  24 D,  24 E, and  24 F that are provided in tandem and that transfer the various layers of toner necessary to form the multi-toner image. In this embodiment each electrophotographic module  24 A,  24 B,  24 C,  24 D,  24 E, and  24 F contains a single primary imaging member  26 A,  26 B,  26 C,  26 D,  26 E, and  26 F and a single development system  28 A,  28 B,  28 C,  28 D,  28 E, and  28 F to develop toner for ITM  30  or in other embodiments for a receiver  44 . 
         [0016]    Development stations  28 A- 28 F provide charged toner for use in printing. Generally, toner takes the form of toner particles formed from a material or mixture of materials that can be charged and electrostatically propelled to form an image, pattern, or coating on an oppositely charged imaging member including a photoreceptor, photoconductor, electrostatically-charged, or magnetic surface. Toner is used in an electrophotographic print engine  22  to convert an electrostatic latent image into a visible image or pattern of toner on an ITM  30  and into a visible image on a receiver  44 . 
         [0017]    Toner particles can have a range of diameters, e.g. less than 8 μm, on the order of 10-15 μm, up to approximately 30 μm, or larger. When referring to particles of toner, the toner size or diameter is defined in terms of the median volume weighted diameter as measured by conventional diameter measuring devices such as a Coulter Multisizer, sold by Coulter, Inc. The volume weighted diameter is the sum of the mass of each toner particle multiplied by the diameter of a spherical particle of equal mass and density, divided by the total particle mass. Toner is also referred to in the art as marking particles or dry ink. In certain embodiments, toner can also comprise particles that are entrained in a wet carrier. 
         [0018]    Color toner particles typically have optical densities such that a monolayer coverage (i.e. sufficient application of marking particles such that a microscopic examination would reveal a layer of marking particles covering between 60% and 100% of a primary imaging member) would have a transmission density of between 0.6 and 1.0 in the primarily absorbed light color (as measured using a device such as an X-Rite Densitometer with Status A filters). However, it will be appreciated that these transmission densities are exemplary only and that any conventional range for transmission density or reflectivity can be used with the color toner particles. 
         [0019]    Toner can also include clear particles that have the appearance of being transparent or that while being generally transparent impart a coloration or opacity. Such clear toner can provide for example a protective layer on an image or can be used to create other effects and properties on the image. 
         [0020]    The various electrophotographic modules each deliver only one type of toner and they can be used in various combinations as desired to print different types of images or to achieve other effects. In the electrophotographic engine shown in  FIG. 1  six electrophotographic modules  24 A,  24 B,  24 C,  24 D,  24 E and  24 F enable six different types of toner to be applied in various combinations. 
         [0021]    For example, in one application, electrophotographic modules  24 A,  24 B,  24 C,  24 D can supply toner particles of one of the four subtractive primary colors that can be applied in various combinations to create images having a full gamut of colors, thus creating an opportunity for fifth and sixth electrophotographic modules  24 E and  24 F can be used to deliver additional toner types. These additional toner types can include, but are not limited to toner particles that include different subtractive toner colors, clear toner, and raised print, MICR magnetic characters, as well as specialty colors and metallic toners and can deliver toners that are not produced with the basic four subtractive color marking particles. In this example, fifth electrophotographic module  24 E and sixth electrophotographic module  24 F can deliver a clear toner in a first layer as an overcoat material and in a second layer to form raised textures above the overcoat layer. Here too, it will be understood that these examples are not limiting as fifth electrophotographic module  24 E and sixth electrophotographic module  24 F can delivery any known type of toner as may be useful or required. It will be appreciated that the organization of toner types with respect to particular electrophotographic modules  24 A- 24 F is provided by way of example and is not limiting. 
         [0022]    In particular, the selection of an individual operating or owning (hereafter referred to as the operator) EP printer  20  can provide control signals to controller  82  by way of a user input  84  that printer controller  82  can use to determine which specialty marking particles to apply to an image and where to apply these specially marking particles in order to achieve a particular print outcome. Similarly, input allowing printer controller  82  determines which specialty marking strip like an image and where to apply these specially marking particles can be can take the form of signals from a user input system signals from signals that are associated with a digital image provided for printing. 
         [0023]    In the embodiment that is illustrated in  FIG. 1 , development systems  28 A- 28 F develop the electrostatic latent image on a primary imaging member (PIM)  26 A- 26 F respectively and thereby convert the electrostatic latent image a visible image. Each toner image is transferred, in register, to an intermediate transfer member (ITM)  30  to form a toner transfer image. Method and systems for imparting the charge pattern are well known to those of skill in the art. The ITM can be in the form of a continuous web as shown or can take other forms such as a drum or sheet. It is preferable to use a compliant intermediate transfer member, such as described in the literature, but noncompliant ITMs  30  can also be used. 
         [0024]    The multi-toner image formed on ITM  30  is then transferred to a receiver  44 , when receiver  44  passes through transfer nip  40  in conjunction with the multi-toner image. In the embodiment that is illustrated in  FIG. 1 , receiver  44  is provided in the form of receiver sheets that are held in the printer at receiver source  46 . However, in other embodiments, receiver  44  can be provided on rolls or other forms. As toner is depleted, the toner concentration of the developer decreases until it becomes necessary to add additional toner to replenish the developer within the development station. This is done by adding toner T from replenishment stations  70 A,  70 B,  70 C,  70 D,  70 E, and  70 F to a developer station  540  contained in electrophotographic modules  24 A,  24 B,  24 C,  24 D,  24 E, and  24 F, respectively. 
         [0025]    Receiver  44  enters receiver path  48  so as to travel initially in a counterclockwise direction through receiver path  48 . Alternatively, receiver  44  could also be manually input from the left side of the electrophotographic printer  20 . The multi-toner image is transferred from the ITM to a receiver  44  and the image bearing receiver then passes through a fuser  60  where the image is fixed to the receiver. 
         [0026]    The image then enters a region where the receiver either enters an inverter  62  or continues to travel counterclockwise through a recirculation path  64  that returns receiver  44  to receiver path  48  such that receiver  44  will pass through transfer nip  40  and fuser  60  again, exiting the fuser in fuser exit nip  152 . If receiver  44  enters inverter  62 , receiver  44  travels clockwise, stops, and then travels counterclockwise back through recirculation path  64  to receiver path  48 . This inverts the image, thereby allowing the image to be duplexed. Prior to the inverter is a diverter  66  that can divert receiver  44  from inverter  62  and send receiver  44  along recirculation path  64  in a counterclockwise direction. 
         [0027]    Recirculation of a non-inverted receiver  44  allows multiple passes of on a same side of receiver  44  as might be desired if multiple layers of marking particles are used in the image or if special effects such as raised letter printing using large clear toner are to be used. Operation of diverter  66  to enable a repeat of simplex and duplex printing can be visualized using the recirculation path  64 . 
         [0028]    It should be noted that, if desired, the fuser  60  can be disabled so as to allow a simplex image to pass through the fuser without fusing, if desired. This might be the case if an expanded color balance in simple printing is desired and a first fusing step might compromise color blending during the second pass through the EP engine. Alternatively, a fusing system  60  that merely tacks or sinters, rather than fully fuses, an image and is known in the literature can be used if desired such as when multiple simplex images are to be produced. The image can also be sent through a subsystem that imparts a high gloss to the image, as is known in the art. 
         [0029]    The term auger refers to a rotatable member located within the sump  550  contained within an enclosure  18  of the developer station that is used to feed developer onto the development shell, transport developer within the development station, or mix developer such as might be required when replenishing fresh toner to replace toner that has been removed from the developer during development of the electrostatic latent image. The auger  370 , can have a single shaft  375  attached to one or more spiral members  376  that move developer. Alternatively, the term auger can also mean any rotatable mechanical means for transporting developer such as a screw mechanism, a paddle mechanism, or a spiral shaft. The shaft typically extends outside the sump at least on one side to enable the shaft to be connected to a drive motor  380 . 
         [0030]    As developer is added to a developer station though a developer inlet  240 , the auger shaft  375  is rotated by the drive motor  380  to transport the developer along the length of the sump, as shown in  FIG. 3 . As the quantity of developer is increased, the auger encounters increasing drag caused by the developer, requiring that the power supplied to the drive motor  380  be increased by increasing either the current or the voltage supplied to the drive motor. The increase drag is especially noticeable when the carrier contains hard magnetic carrier particles or when magnetic hysteresis causes soft magnetic carrier particles to retain some magnetism. 
         [0031]    The present invention can be practiced by automatically limiting the filling of the developer station by the system for filling a developer station  500  when a predetermined torque required to rotate the auger is reached. This can be done using a torque meter, an ammeter, or a voltmeter to measure the torque experienced by the auger shaft or the current or voltage required to drive the shaft. The motor or auger shaft can be attached to a governor to automatically increase the power to the motor to compensate for the increased drag as developer is added. When a predetermined torque, current, or voltage is required, a signal is sent to a processor  510  that operates a gate or valve  512  that closes the feed tube so that no more developer enters the development station. Alternatively, a slip clutch  515  can be inserted between the drive motor and auger shaft, as shown in  FIG. 2 . When a predetermined drag is reached, the clutch disengages causing the gate or valve  512  to close. Drag can also be monitored using a tachometer to measure the speed of the auger shaft at constant voltage and current applied to the motor. If the shaft slows due to increasing drag, the voltage or current applied to the drive motor can be increased to compensate for the increased drag. Alternatively, if the auger speed slows to a predetermined speed, the development station can be considered to be full and further addition of developer is stopped. 
         [0032]    Of particular value in practicing this invention is to use a drive motor that is either a constant speed or constant torque drive motor so that the current or voltage applied to the drive motor is automatically increased as the drag is increased until a predetermined current or voltage needed to drive the drive motor has been reached. At that point the filling process is terminated either automatically or through manual intervention, as discussed previously. 
         [0033]    In an alternative method of practicing this invention, an operator can manually close the valve or gate when a predetermined voltage, current, or torque is reached. 
         [0034]    The present invention has an additional benefit in that, as the drag is increased, the valve can be closed in response to the increasing torque, voltage, or current, thereby reducing the chance of overfilling the developer station or spilling developer due to overfilling the developer station. The ability to monitor the voltage, current, or torque provides a feedback mechanism that can be used to either automatically or manually control or limit the amount of developer that is added to the developer station. 
         [0035]    While various sources of developer to be added to the developer station can be used, including small packets of developer, scoops of developer and the like, it is preferable that the developer to be added to the developer station be contained within a large hopper capable of holding sufficient developer to fill multiple developer stations. 
         [0036]    It should be noted that the geometry of the station including sump size and auger design, as well as the specific magnetic and physical properties of the carrier, toner, and combined developer and the strength of the magnetic core will all affect the drag. Consequently, the drag needs to be calibrated against the mass of developer added to the development station prior to using this invention. Once calibration has been done, it should not have to be repeated as long as the same type of developer is being used to fill the same type of development station. 
         [0037]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
       PARTS LIST 
       [0000]    
       
           18  enclosure 
           20  electrophotographic (EP) printer 
           22  print engine 
           24 A- 24 F electrophotographic module 
           26 A- 26 F primary imaging member (PIM) 
           28 A- 28 F development system 
           30  intermediate transfer member (ITM) 
           32  intermediate transport system 
           34  intermediate transport motor 
           40  transfer nip 
           42  receiver transport system 
           44  receiver 
           46  receiver source 
           48  receiver path 
           60  fuser 
           62  inverter 
           64  recirculation path 
           66  diverter 
           70 A- 70 F replenishment stations 
           82  controller 
           84  user input 
           152  fuser exit nip 
           240  developer inlet 
           370  auger 
           375  shaft 
           376  blade 
           380  motor 
           500  system for filling a developer station 
           510  processor 
           512  gate 
           515  slip clutch 
           540  developer station 
           550  sump containing developer