WO1997022039A1

WO1997022039A1 - Electrophotographic apparatus and method

Info

Publication number: WO1997022039A1
Application number: PCT/GB1996/003045
Authority: WO
Inventors: Geoffrey Fermor-Dunman
Original assignee: Gestetner Management Limited
Priority date: 1995-12-11
Filing date: 1996-12-10
Publication date: 1997-06-19
Also published as: AU1103897A; GB9525294D0; GB2308096A

Abstract

A photocopier includes scanning means (2-8 and 12) responsive to the primary colours of an image on an original on a sheet platen (1), and printing means (23-25) for process colours complementary to the corresponding primary colours of said scanning means to apply colouring medium such as toner of the appropriate process colours to a carrier (8) to define a multi-colour image on the carrier. A processor (26) generates respective signals to counters (23a, 24a and 25a) indicative of the consumption of the respective process colouring media or toners. The process and apparatus may be applied to a digital photocopier or to an analog photocopier.

Description

ELECTROPHOTOGRAPHIC APPARATUS AMD METHOD

The present invention relates to an electrophotographic apparatus and to an electrophotographic method in which the copy cost can be more accurately determined than with conventional machines.

In the past the copy cost of an electrophotographic apparatus has been estimated on the basis of an average image density on the sheet (usually less than 15%) , bearing in mind that the typical sheet being copied is a sheet of text which has generous margin areas and which in any case consists of relatively small dark areas on an extensive white background where no toner will be needed. The copy cost is usually a composite of the material costs (toner and other consumables such as the photoconductive member of the copier) , and a second part which iβ a function of the maintenance costs and other overhead charges. The component of the charge to cover the toner usage is normally pitched at a high enough level so that the toner consumption will never outstrip the allowance made for it in the copy cost calculation. This may result in the user of electrophotographic apparatus paying a lot more for the copies than would otherwise be necessary on the basis of material costs.

In the context of a colour reproduction process, the electrophotographic copy costs are much more difficult to compute because first of all there are at least three

(usually four) different toner types being used in the apparatus rather than simply one in a monochrome copier and secondly it is usual for the colour process to be used in the context of pictures where (i) the area of copy sheet covered in toner is much greater than the area which would be covered with the typical (monochrome) text copy, and (ii) the image is often built up of several process colour toners, and optionally black toner, superimposed on one another. It is known to provide, within an electrophotographic apparatus, means to control the dispensing of toner from a supply hopper or cartridge to an image developer so as to maintain an optimum quantity or density of toner in the developer. US-A-4969011, TJS-A-4974024, US-A-5075726 and US- A-5124751 disclose such machines. It is also known to provide such apparatus with means to warn the operator that toner needs to be added in order to maintain copy quality. US-A-5202769 and GB-A-2259583 disclose such machines.

It is an object of the present invention to provide a method and apparatus for enabling copy costs to be determined during operation of an electrophotographic apparatus and method.

Accordingly, one aspect of the present invention provides electrophotographic apparatus comprising means for scanning an original image; printing means effective to apply onto a carrier a pattern of toner, said printing means being controlled in response to said scanning means; means for evaluating the consumption of colouring medium used by said printing means; and means for delivering to the exterior of said electrophotographic apparatus a measure, relevant to a given period, of the consumption of said colouring medium.

Preferably the copy cost calculating means are located at a station remote from the consumption evaluating means so that the individual electrophotographic apparatus only needs additional means to generate a signal of toner consumption. The calculating means can then be common to various electro¬ photographic apparatus units in the field. More preferably the signals are representative of the consumption of all three, or optionally four, toners in a colour copying process.

A second aspect of the present invention provides an electrophotographic process comprising scanning a multi¬ colour image on an original; applying a plurality of process colour images to a carrier in response to said scanning means to build up a multi-colour image on said carrier; measuring the consumption of the colouring medium of the respective process colours; and assessing the material costs of said electrophotographic process.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawing, in which:

Fig. ZI shows a first embodiment of an analog color photocopier in accordance with the present invention; Fig. 2 shows a modification of the photocopier of Fig. 1; and

Fig. 3 βhows a digital colour copier in accordance with the invention.

Figure 1 shows a first embodiment of analog photocopier in which light pasβes along an optical path between a lamp on a moving scanning sledge and a moving photoconductor, by way of a lens, to expose the photoconductor image-wise to an image similar to that on the original sheet on a stationary transparent platen 1 above the path of the scanning sledge. The scanning sledge carries a first mirror 2 which deflects light from the scanning lamp 3 on to an upper compensating mirror 4 which then reflects it on to a lower compensating mirror 5 from which the light passes back across the machine, below the platen 1, through a lens 6 which ensures that the beam, after having been reflected by a stationary mirror 7, iβ focused on the surface of the photoconductor drum 8.

In a known way, in order to maintain focus with a fixed focus lens 6, the upper and lower compensating mirrors 4 and 5 are carried on a sledge which traverses at one half of the traverse speed of the scanning sledge (and hence along a path only half as long as that of the scanning sledge) , thereby ensuring that the light path from the scanned point on the surface of the original 10 on the platen to the stationary line of incidence on the photoconductor drum 8 (which is itself rotating so that the image effectively traverses along the surface of the drum in a circumferential direction) remains constant.

In order to effect a magnification or reduction of the printed image relative to the scanned image, the fixed focus lens 6 will be repositioned so that the scanned line of image will be in a given magnification or reduction ratio a relative to the original image line and the ratio of the linear speed of the surface of photoconductor drum 8 relative to that of the scanning βledge will be reduced or increased accordingly from 1:1 to equal the value of ratio a .

Copy sheets 11 from a copy sheet feed tray 12 are fed one at a time into contact with the surface of a copy carrier drum 13 to which the copy sheet 11 becomes attracted by suction applied within the copy carrier drum 13. This ensureβ that the registration of the sheet 11 remains constant on the surface of the copy carrier drum 13 but more importantly there is also a sheet stop to enβure that the registration iβ accurate in relation to the position of the scanning βledge. When the copy sheet has acquired its multi-colour image it is released from the surface of the copy carrier drum 13 and passes onwardly to a pressure fuser 14 by way of a feed conveyor belt 15, and the finished copy sheet together with its fused multi-colour image thereon is then delivered to a collecting tray 16.

Other elements around the periphery of the photoconductor drum 8 include a pre-clean corona 19, a cleaning brush 20, a charging corona 21, a black toner developer unit 22, and the three process colour developer units 23, 24 and 25 for the three process colours (cyan, magenta, and yellow) .

Throughout this description and claims the term "process colour" is intended to denote the appropriate one of the colours cyan, magenta and yellow, whereas the black toner is always referred to as such.

The four developer units 22 to 25 have respective output lines 22a, 23a, 24a and 25a, applying signals to a processing unit 26 which then delivers four outputs to toner counters 22b, 23b, 24b and 25b.

The signalβ for the toner counters may be derived from the respective developer unit, to record the quantity of toner delivered to that developer or from the developer control unit which determines how long each developer unit remains active during a particular copy cycle, or any other convenient parameter. The procesβor 26 may also have inputs to respond to the pre-exposure charging voltage at charging corona 21, or inputs from βensorβ responsive to ambient conditions which will control the efficiency of toner transfer.

In order to allow for multi-coloured βcanning from the original, a rotating cruciform cross-section optical filter 17 is positioned in the light path between the final mirror 7 and the surface of the photoconductor drum 8 and can be indexed to bring an appropriate one of its four filter paddles into that light path. Thus during a first scanning cycle (when the scanning βledge traverβes the entire original 10 for a first occasion) a first filter paddle (for example the red filter) is positioned in the light path BO that only red light will be able to pass through the filter and to form on the photoconductor drum a negative image corresponding to the cyan process colour needed in the first developer cycle. In the present embodiment the first cycle of the photoconductor drum 8 passes its surface succesβively past the pre-clean corona 19, the cleaning brush 20 and the charging corona 21 so that the surface arriving at the line of incidence with the scanned beam is uniformly non-conduc¬ tive and thereby still charged with the charge imparted by the charging corona 21. At the point of exposure, those parts which are exposed to light will become conductive and will allow the surface charge to dissipate through the photoconductor to an electroconductive metal carrier drum on which the photoconductive material is deposited, whereas those parts which are not expoβed to the scanned light beam will remain non-conductive and therefore still charged with the charge imposed by the charging corona 21.

The thus image-wise exposed photoconductor surface passes onwardly past the four developer units 22 to 25, of which only the cyan developer unit 23 will be active and will develop the image.

Subsequently, at the point where the surface of the photoconductor drum 8 passes the copy carrier drum 13 that cyan image will be transferred to the sheet of paper held firmly against the surface of the copy carrier drum 13.

The surface of the photoconductor drum 8 then continues past the pre-clean corona 19, the cleaning brush 20, and the charging corona 21. By this time the filter 17 will have indexed to bring the green filter paddle into the path of the scanning beam and hence the latent electrostatic image formed on the surface of the photoconductor drum 8 will be different and will correspond to the magenta copy image which will now be developed by activation of the developer unit 24 with the other developer units 22, 23 and 25 inactive.

This cycle proceeds as for the cyan development and the third and subsequent cycle then proceeds with the blue filter paddle in the path of the scanning beam and the yellow developer unit 25 operative with the other three developer unite 22, 23 and 24 inoperative.

Throughout this three cycle copy operation the multi¬ colour image is being built-up in three steps on the copy sheet 11 on the carrier 13, and equally output signals from the three developers 23, 24 and 25 concerned will pass along the lines 23a, 24a and 25a to the processor 26 which will generate appropriate toner consumption signals to the counters 23b, 24b and 25b.

In order to allow for monochrome copying, the fourth paddle of the filter 17 iβ clear and will allow a white scanning beam to pass unfiltered to the line of incidence on the photoconductor drum 8, at which time the elements 19 to 21 will be operating as before but this time the black developer unit 22 will be operating while the cyan, magenta and yellow developer units 23, 24 and 25 are inoperative. Again the appropriate signal is sent down the line 22a to the processor 26 which generates a toner consumed signal for the counter 22b.

By taking the readings on the four counters 22b, 23b, 24b and 25b^~it is possible to monitor the consumption of each of the four toners and to produce, over an extended period of operation of the photocopier, a realistic evaluation of the consumption of the four toner materials so that the actual copy cost can be determined more precisely than hitherto.

Figure 2 shows an alternative form of the photocopier of Figure 1, where the differences reside in the processing of the toner consumption signal. Thus the various optical and electrostatic elements, as well as the paper handling elements, need not be described again.

This time, -the signals from the four developer units pass along telemetry lines 22c, 23c, 24c and 25c to a remote monitoring unit 30 which also receives inputs from other photocopiers in the field, βo that in thiβ case a supplier of photocopying equipment can monitor centrally the toner consumptions of various photocopiers for which he has responsibility for maintenance and supplieβ. This both enables continuous centralised assessment of copy costs and also allows re-supplying of toner, as and when required, to be controlled centrally.

The monitoring can be either continuous or by periodic interrogation of the respective photocopiers from the central remote processor 30.

Figure 3 illustrates in schematic form one embodiment of a digital photocopier. The original 50 on a transparent platen 51 iβ scanned by a βcanning βledge comprising a light source 52 and a first mirror 53 which deflects the scanned beam horizontally towards an upper compensating mirror 54 which then passes the beam downwardly to a lower compensating mirror 55.

As with the embodiment of Figures 1 and 2, the upper and lower compensating mirrors are themselves traversed at a constant speed which is half the constant βcanning speed of the scanning sledge carrying the light source 52 and first mirror 53.

The optical path again includes a lens 56 but the focused beam from the lens is received on a CCD (charge coupled device) 57 from which the electrical output indica- tive of the scanned beam passes along line 58 to a processor

59.

The CCD 57 includes pixels responsive to each of the three primary colours and effectively scans a complete line of the original simultaneously. The traversing of the scanning sledge ensures that the entire original area on the platen is scanned line by line. Hence over one scanning traverse the processor 59 receives electrical signals corresponding to the complete image.

In practice the area to be scanned will be equivalent to that of the largest sheet which is intended to be copied.

For magnification and reduction the ratio of scanning sledge linear speed to the linear speed common to the photoconductor drum 62 and the carrier belt 67 will be variable but magnification or reduction of the scanned line will be effected electronically by expansion or compression of the image line.

The outputs from the processor 59 comprise a first output 60 which drives the print head 61 to expose the photoconductor drum 62 with images of the respective colours. As with the embodiment of Figure 1, the black toner developer unit 63 is energised by output line 63a from the processor 59, and likewise the cyan, magenta and yellow developer units 64, 65 and 66 are energised by lines 64a, 65a and 66a, respectively. The sequence of cleaning, charging, exposure and developing of the surface of the photoconductor drum 62 is the same as for the Figure 1 embodiment, but in this case each of the images is immediately transferred to an endless carrier belt 67 which cycles freely for four (or optionally only three) revolutions of the photoconductor drum 62 to acquire the three separate process colour image components and the optional black component to combine to provide the final colour image. Then only after acquisition of the last (usually the fourth) image component, the yellow image component, does the transfer station 68 operate to transfer the multi-colour i age from the carrier belt 67 to a copy sheet 69 being fed from a copy sheet supply tray 70 to a copy sheet collection tray 71 by way of the image transfer station 68, a copy sheet conveyor belt 72, and a fuser station 73. As in the case of the embodiment of Figure 1, the black toner developer unit 63 can be used, if desired, for mono¬ chrome copying.

However, in the context of multi-colour copying it is also possible to economize on the process colour toners by analysing the digital image electronically and ensuring that to whatever extent the image is composed of equal quantities of all three process colours (making a black component to the copy image) the whole of that common component or at least a proportion of it can be made up of a single initial applica¬ tion of black toner and the remaining proportions of the process colour toner components to complete the multi-colour image can be superimposed on this. This process would require four steps, one for each of the four developer units 63 to 66 which successively operate to build up the required multi-colour image on the image carrier belt 67 for subse- quent transfer complete to the copy sheet 69. As with the analog copier shown in Figure 1, the sequence of printing the process colours is cyan-magenta-yellow (after the optional black first toner) . Such four component operation allows the four developer units 63, 64, 65 and 66 to build up the required image, but with an overall economy of toner used. Such four component operation is normal in digital copiers. Where only a proportion of the common image component is substituted by black toner, the proportion may be adjustable by the user of the copier.

The processor 59 delivers further "toner consumption" outputs on lines 63b, 64b, 65b and 66b, equivalent to the consumption of toner for each of the four developer units 63, 64, 65 and 66, respectively. Those βignalβ are passed by telemetry lines 63b to 66b on to a remote toner consumption monitoring station 74, equivalent to the remote monitoring station 30 of Figure 2.

If desired, the multi-colour image can be built-up directly on the copy sheet, much in the manner described above with reference to Figures 1 and 2, rather than being transferred from the photoconductor drum first to the carrier belt 67 and then to the copy βheet.

Although in the description of the embodiment of Figure 1 we refer to a clear filter paddle in the light path in the monochrome (black toner) mode, there may in practice be a colour correction filter permanently in the light path, for example carried by the scanning sledge. Such a colour correction filter is not necessary in the embodiment of Figure 3 where the circuitry of the digital photocopier allows electronic processing to correct for colour sensitiv¬ ity. When calculating the material costs of a monochrome photocopier, the calculation is simplified by the fact that there is only one toner used. Furthermore it is uβual for monochrome printerβ to be used for copying typescript or line drawings in which there will be a relatively constant margin area and a relatively constant image density outside the margin area for example on the page of typescript.

By contrast, a multi-colour photocopier is usually reserved for pictorial images with solid outline where the consumption of toner iβ much higher, and furthermore the toner itself may be more costly.

Equally, the optional black toner and the individual toners used for the three process colour developers may differ in cost and thus the total material cost of running such a multi-colour photocopier may depend greatly upon the nature of the work of a particular user. The image area of a colour photocopy may be in excess of 80% of the total sheet area (compared with a typical figure of the order 15% for a monochrome photocopier copying typescript) ; also this image is made up of three or four separate toners which in many parts of the image all of the printed components will be βuperimposed on one another with the result that the total quantity of toner used for a multi¬ colour image may be equivalent to a lot more than 100% of the sheet area. Becauβe of this higher actual toner consumption, it iβ uβeful to know the consumption of toner rather than simply assuming an average consumption becauβe it will vary so much between one user and another, and it is also useful to know the make up of that total in terms of the three process colour toners (Cyan, Magenta and Yellow) , and optionally the black fourth toner, used in the copy. Thus the three process colour toner counters 23b, 24b and 25b and the optional black toner counter 22b (Fig. 1) can be read at the same time aβ the copy count meter, so that all relevant parameters (copy count, cyan toner count, magenta toner count, yellow toner count and optionally black toner count) can be used to calculate the actual toner costs of a particu¬ lar user's photocopier. The counters 22b, 23b, 24b and 25b therefore have a display which can be read by the user, and checked by the engineer on any service calls.

If desired, the lines to the toner counters 22b, 23b, 24b and 25b may be replaced by a single line by which the signals to the toner counters can be multiplexed.

Throughout the above description the term electrophotographic process has been used to denote a process which uses an electric drive means to generate the image. In the preferred embodiments the electric drive means may comprise an electrostatic charge device for charging a photoconductor while in its non-conductive state so aβ to allow select discharging of the photoconductor when it becomes selectively photoeonductive in an image-wise manner after exposure to an optical scanning system. Equally the electric driver may comprise an electric print head respon¬ sive to input signals derived from an electric image scanning array. Other electrophotographic mechanisms may be used in conjunction with the toner consumption-measuring concept of the present invention. The toner consumption signal may be taken from any convenient part of the apparatus. For example, in the caβe of a digital photocopier the signal may be derived from the scanning signal (for example the output of the CCD 57 in Figure 3) . Equally the toner consumption output may be taken from the processor unit 59 or equivalent in a digital photocopier.

In either a digital or analog copier the toner consump¬ tion signal may be derived from the control line to the developer units. As indicated above this may involve taking the developer unit "on" time aβ a measure of the toner consumption. Otherwise it is possible for the toner density of the image to be analysed optically, for example by printing a calibration patch on the photoconductor, or on the carrier 67 of Figure 3 and observing the quantities of the toners (the three proceβB colourβ and the optional black) used to make up that image.

The important requirement is that there should be a measure of the toners used, and that this should be inte¬ grated over an extensive number of copies to indicate the average content of toner consumed.

Claims

1. Electrophotographic apparatus comprising means for scanning an original image; printing means effective to apply onto a carrier a pattern of toner, said printing means being controlled in response to said scanning means; means for evaluating the consumption of colouring medium used by said printing means; and means for delivering to the exterior of said electrophotographic apparatus a measure, relevant to a given period, of the consumption of said colouring medium.

2. Electrophotographic apparatus according to claim 1, wherein βaid printing means comprise three printing means each for printing a respective procesβ colour, and wherein the βcanning means are effective to scan the original image in a manner appropriate for controlling the three process colour printing means.

3. Electrophotographic apparatus according to claim 2 in the form of a photocopier including indicating means for indicating the consumptions of the respective toners.

4. Electrophotographic apparatus according to claim 2 in the form of a photocopier having an output line connected to βaid colouring medium consumption evaluating means, for transmitting to a remote location βignalβ indicative of the consumption of βaid respective colouring medium.

5. Electrophotographic apparatus according to any one of claim 2 , wherein said scanning means comprise respective scanning heads responsive to visible light of the respective primary colour complimentary to the procesβ colour of a respective said printing means.

6. Electrophotographic apparatus according to claim 5, wherein said carrier is a copy sheet, βaid βcanning means comprises means for scanning the image pixels on an original sheet, and said printing means each comprise a respective printer to deposit a pixel pattern of a respective toner on said copy sheet to build up thereon a multi-colour image corresponding to that of the original sheet.

7. Electrophotographic apparatus according to claim 5, wherein said printing meanβ comprise a photoconductor drum exposed to the scanned image and having a respective devel¬ oper unit for each of the three process colours.

8. Electrophotographic apparatus according to claim 7, wherein said carrier is a belt contacting said drum.

9. Electrophotographic apparatus according to any one of claimβ 5 to 8, wherein said colouring medium consumption evaluating means include means responsive to digital signals from said control means to said printing meanβ for βummating the partβ of the βignal to the respective printing means corresponding to pixels of the appropriate process colour.

10. Electrophotographic apparatus according to any one claims 2 to 4, wherein said carrier comprises at least one photoconductor on which an electrostatic latent image of the appropriate proceββ colour is formed; wherein said printing means compriβes a developer for applying toner to develop said electrostatic latent image; and wherein said colouring medium consumption evaluation means are connected to meanβ for sensing the consumption of colouring medium from the respective procesβ colour developer.

11. Electrophotographic apparatus according to any one of claims 1 to 8, and including, in addition to printing means for three proceββ colourβ, further printing means for generating a monochrome image, or for applying a black toner to supplement a multi-colour image formed by the first mentioned three printing meanβ, and wherein the consumption of the black toner is also evaluated.

12. An electrophotographic process comprising scanning a multi-colour image on an original; applying a plurality of process colour images to a carrier in response to said βcanning meanβ to build up a multi-colour image on βaid carrier; meaβuring the consumption of the colouring medium of the respective proceββ colourβ; and assessing the material costs of said electrophotographic process.

13. An electrophotographic procesβ according to claim 12, comprising βcanning the original image in three primary colours to control three printing means each printing the respective proceββ colour complimentary to one of said primary colours, printing the three proceββ colourβ to generate a multi-colour image, and further comprising meaβuring the consumption of all three process colour colouring media.

14. A process according to claim 13, and further including analysing the scanned primary colour images to determine where points on the original image are made up of all three process colourβ, and then replacing equal portions of each of the three procesβ colours which are at most equal to the value of that procesβ colour density which is the least of the three present, by a common black toner constituent by means of a fourth printing meanβ.

15. An elec rophotographic process according to claim 12, comprising scanning said original image with a single scanning head and electronically analysing the output from the βcanning head to derive primary colour control signals for driving respective procesβ colour printing meanβ, and further comprising measuring the consumption of all three process colour colouring media.

16. Electrophotographic apparatus substantially aβ hereinbefore described with reference to, and as illustrated in Fig. 1 or Fig. 2 or Fig. 3 of the accompanying drawings.

17. An electrophotographic proceββ substantially aβ hereinbefore deβcribed with reference to the accompanying drawingβ.