Abstract:
The amount of toner remaining in each toner cartridge (20a-20d) of a printer (1) is estimated by incrementing a count when one pel is detected in each small region of the bit map. The printer senses toner out, after which the scale ascribed to one count is revised to reflect the actual count to toner out. Specifically, the count to toner out becomes the number representative of empty so that one-half of that count is interpreted as half full. The remaining toner in each cartridge is displayed to the operator at a gauge (21).

Description:
RELATED APPLICATION 
     This is a continuation-in-part application of U.S. patent application Ser. No. 08/854,606, filed May 12, 1997, now U.S. Pat. No. 5,802,420 entitled &#34;Method and Apparatus for Predicting and Displaying Toner Usage of a Printer&#34;. 
    
    
     This invention relates to the field of imaging apparatus, such as printers and copiers, and, more specifically, this invention is directed to determining the amount of marking material, such as toner or ink, remains before the supply of marking material will be exhausted. 
     BACKGROUND OF THE INVENTION 
     Displaying the quantity of marking material remaining in a printer or copier is widely achieved in a variety of ways. Typically, the imaging device operates by marking or not marking in grid pattern, each tiny square being termed a pel. It is known to count the number of pels at which ink is printed and the usage of marking material is computed from the number counted. The amount of the beginning or full supply of ink is known and the estimated remaining ink is that amount computed by subtracting the estimated usage. The estimation formulas took into account the size of the dots printed and the characteristics of the imaging device. However, prior to the foregoing parent application, no estimation formula was known which took into account actual usage history of the imaging device. 
     By taking into account actual usage history, the estimation formula is made more accurate. In accordance with the preferred embodiment of this application, only single sensing for toner/ink-out is employed, which is cost effective. Since the estimation formula is dynamically modified to reflect past usage, the amount of toner or ink remaining during use after resupply of toner or ink is determined with satisfactory accuracy. This is communicated to the operator by some display, which may be a standard gauge-face (alternatively by artificial voice message, panel display after operator inquiry or similar alternatives). 
     SUMMARY OF THE INVENTION 
     In an imaging device in which marking material is applied from a supply compartment, the amount of marking material is sensed for exhaustion or near exhaustion of the marking material. Typically, the supply compartment is a separate cartridge which is installed in the imaging device full of marking material and which is removed when empty, followed by a full cartridge being installed. The cartridge may be sensed as near empty by weighing the cartridge or by optical or virtually any other sensing techniques. In a laser cartridge, measuring the physical resistance to movement of a stirrer in the toner is effective and practical. During imaging the bit map of pels to be printed is observed electronically and usage of toner is computed by a formula which ascribes an assumed amount of use based on the presence of bits to be printed. This need not be a rigorous count of the bits. The presence of a bit in a predetermined, small region can be acted on as a &#34;yes&#34; for toner/ink usage in that region. When the sensor signals that toner is out or is near out, the amount calculated is noted and the factors of the estimation formula are adjusted so that the formula would have produced the same result as the sensor. Thus, if the estimation formula shows 1/8 full, the estimation formula is adjusted upward the factor 8/7. 
     The estimation formula is then used after installation of the next cartridge or other refill. The result from the revised estimation formula is signaled to or may be called out by the printer or copier operator to inform the operator of the status. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description and claims serve to explain the principles of the invention. In the drawings: 
     FIG. 1 illustrates generally a printer incorporating this invention. 
     FIG. 2 illustrates the sequence of operations implementing this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of this invention is implemented in a laser printer, shown illustratively as printer 1. Printer 1 receives control information in a standard manner from communications cable 3. Since the printer 1 may be largely pre-existing, such as the Optra™SC or other Optra™ printer sold in large numbers by the assignee of this invention, most aspects of printer 1 will be described only very generally and aspects not interoperative with this invention may not be mentioned. Although the following description given is primarily to an embodiment in a laser printer using toner, inkjet printers also apply ink to print pels in a bit map so the applicability of this invention to inkjet printers will be evident. 
     Printer 1 has an optical system 5 operative on drum 7. Drum 7 transfers images defined by optical system 5 at transfer station 9 to paper 11. The image is fixed, typically by heat, at fixing station 13, and the finished printed page is delivered to output tray 15. 
     Data processor 17 in printer 1 monitors the data received and interprets the data in accordance to the control language or other mode to which the data processor 17 is set. Information received on cable 3, as well as other information, is stored electronically in memory 19. Data processor 17 creates a bit map in a given resolution, in the preferred embodiment, 600×600 dpi (dots per inch resolution). The bit map is stored electronically in memory 19. (Such storing may be by compression, but such memory techniques are irrelevant to this invention.) Each bit in the bit map stored in memory 19 defines a significance (such a white or black) exclusive to one 1/600 inch square in the final image. 
     This embodiment was developed for use with a multicolor printer. Accordingly, the single imaging mechanism described is illustrative of four separate mechanisms, one in which the toner is black, one for which the toner is magenta, one for which the toner is cyan, and one for which the toner is yellow. This is shown illustratively by four toner-supply cartridges 20a, 20b, 20c and 20d, shown spaced from the drum 7 for purposes of illustration. In actual use, cartridge 20a-20d are adjacent to drum 7 and, in fact, in addition to a compartment for the toner, typically contain their associated drum 7, so that drum 7 and generally other developing mechanisms are replaced with each replacement of a cartridge 20a-20d. 
     Also, for purposes of this invention a use gauge 21 of toner is shown on the top of printer 1 where it readily may be observed by an human operator of printer 1. (This positioning is illustrative. In practice such a full showing preferably would be on the monitor of a computer in communication with printer 1.) The display of this gauge might be a continuous bar, each of which is at the top of gauge 21 when a cartridge 20a-20d is full and each of which shortens to a bottom level in proportion to the estimated use of toner in its respective cartridge 20a-20d. Of course, virtually any form of communication, including modern introductions such as artificial voice, would be consistent with this invention. 
     With reference to FIG. 2, the following sequence conducted by microprocessor 17 using memory 19 unless otherwise stated is employed. In the first function 30 a bit map of the image to be printed is created from information received on cable 3. In action 32, a section of the bit map of a size about 1/500 of an 81/2 inch by 11 inch page (specifically, a rectangle in the bit map of 512×128 pels) are examined for at least one pel of toner. If yes, counter 34 is incremented. At each tenth page or other suitable interval, the estimate of remaining toner is computed, action 36. 
     The computation is an entirely linear one. Each increment of counter 34 results in an increase by a set amount of the former amount computed in action 36. The resulting amounts are subtracted from the initial amount in a full cartridge 20a-20d, which is, of course, readily known from the physical dimensions of the cartridges 20a-20d. The output of the estimate is employed to control display 21. In the four color embodiment, the computation as described is separate for each color and display 21 shows the four different results. The original or default amounts applied in the estimates are typically twice as large for color as for black, as black is typically text and lines. 
     When the empty signal is received for one of the cartridges 20a-20d, this activates the revise scaling function 38 for that cartridge. Since the computation is linear, the coefficient of the estimate computation is simply multiplied by the reciprocal of the proportion of usage computed at near empty. For example, if the estimate from the computation of 36 is 3/4 empty, the coefficient of the estimate function is multiplied by 4/3, which scales that function to one based on the actual operation of the cartridge 20a-20d just used. In implementation, the number of counts to empty becomes the beginning number in the subsequent estimate, so that for example, half of the new number is interpreted as half empty. A new cartridge 20a-20d is inserted to replace the empty one and counter 34 is reset with respect to the replaced cartridges. 
     Since this embodiment was developed for use with an existing printer mechanism, the manner of sensing near empty on that particular mechanism is not known in detail. It apparently employs a stirrer which in a manner useful only when each of the cartridges 20a-20d are near empty. 
     It will be apparent that the dynamic estimates of this invention are applicable to all imaging devices whether employing dry material or liquid ink so long as the marking material is resupplied in a known volume, which is true for toner and ink in replaceable cartridges as is now very common.