for a general understanding of an electrostatographic printing machine in which the present invention may be incorporated , reference is made to fig1 which depicts schematically the various components thereof . hereinafter , like reference numerals will be employed throughout to designate identical elements . although the cleaning apparatus of the present invention is particularly well adapted for use in an electrostatographic printing machine , it should become evident from the following discussion , that it is equally well suited for use in a wide variety of devices and is not necessarily limited to the particular embodiments shown herein . referring now to the drawings , where the showings are for the purpose of describing a preferred embodiment of the invention and not for limiting same , the various processing stations employed in the reproduction machine illustrated in fig1 will be briefly described . a reproduction machine in which the present invention finds advantageous use utilizes a charge retentive member in the form of a photoconductive belt 10 consisting of a photoconductive surface and an electrically conductive , light transmissive substrate and mounted for movement past a charging station a , an exposure station b , developer stations c , transfer station d , fusing station e and cleaning station f . belt 10 moves in the direction of arrow 16 to advance successive portions thereof sequentially through the various processing stations disposed about the path of movement thereof . belt 10 is entrained about a plurality of rollers 18 , 20 and 22 , the former of which can be used as a drive roller and the latter of which can be used to provide suitable tensioning of the photoreceptor belt 10 . motor 23 rotates roller 18 to advance belt 10 in the direction of arrow 16 . roller 18 is coupled to motor 23 by suitable means such as a belt drive . as can be seen by further reference to fig1 initially successive portions of belt 10 pass through charging station a . at charging station a , a corona discharge device such as a scorotron , corotron or dicorotron indicated generally by the reference numeral 24 , charges the belt 10 to a selectively high uniform positive or negative potential . any suitable control , well known in the art , may be employed for controlling the corona discharge device 24 . next , the charged portions of the photoreceptor surface are advanced through exposure station b . at exposure station b , the uniformly charged photoreceptor or charge retentive surface 10 is exposed to a laser based input and / or output scanning device 25 which causes the charge retentive surface to be discharged in accordance with the output from the scanning device . preferably the scanning device is a three level laser raster output scanner ( ros ). the resulting photoreceptor contains both charged - area images and discharged - area images as well as charged edges corresponding to portions of the photoreceptor outside the image areas . [ the high voltage latent image is developed with positive (+) charged black toner and is called charge area development ( cad ). the low voltage latent image is developed with negative (-) charge color toner and discharge area development ( dad )]. the photoreceptor , which is initially charged to a voltage undergoes dark decay to a voltage level . when exposed at the exposure station b it is discharged to near zero or ground potential in the highlight ( i . e . color other than black ) color parts of the image . the photoreceptor is also partially discharged in the background ( white ) image areas . after passing through the exposure station , the photoreceptor contains charged areas and discharged areas which corresponding to two images and to charged edges outside of the image areas . at development station c , a development system , indicated generally by the reference numeral 30 advances developer materials into contact with the electrostatic latent images . the development system 30 comprises first and second developer apparatuses 32 and 34 . the developer apparatus 32 comprises a housing containing a pair of magnetic brush rollers 35 and 36 . the rollers advance developer material 40 into contact with the photoreceptor for developing the discharged - area images . the developer material 40 by way of example contains negatively charged color toner . electrical biasing is accomplished via power supply 41 electrically connected to developer apparatus 32 . a dc bias is applied to the rollers 35 and 36 via the power supply 41 . the developer apparatus 34 comprises a housing containing a pair of magnetic brush rolls 37 and 38 . the rollers advance developer material 42 into contact with the photoreceptor for developing the charged - area images . the developer material 42 by way of example contains positively charged black toner for developing the charged - area images . appropriate electrical biasing is accomplished via power supply 43 electrically connected to developer apparatus 34 . a dc bias is applied to the rollers 37 and 38 via the bias power supply 43 . because the composite image developed on the photoreceptor consists of both positive and negative toner , a pre - transfer corona discharge member 56 is provided to condition the toner for effective transfer to a substrate using corona discharge of a desired polarity , either negative or positive . sheets of substrate or support material 58 are advanced to transfer station d from a supply tray , not shown . sheets are fed from the tray with sheet feeder , also not shown , and advanced to transfer station d through a corona charging device 60 . after transfer , the sheet continues to move in the direction of arrow 62 to fusing station e . fusing station e includes a fuser assembly , indicated generally by the reference numeral 64 , which permanently affixes the transferred toner powder images to the sheets . preferably , fuser assembly 64 includes a heated fuser roller 66 adapted to be pressure engaged with a backup roller 68 with the toner powder images contacting fuser roller 66 . in this manner , the toner powder image is permanently affixed to the sheet . after fusing , copy sheets are directed to catch tray , not shown or a finishing station for binding , stapling , collating etc ., and removal from the machine by the operator . alternatively , the sheet may be advanced to a duplex tray ( not shown ) from which it will be returned to the processor for receiving a second side copy . a lead edge to trail edge reversal and an odd number of sheet inversions is generally required for presentation of the second side for copying . however , if overlay information in the form of additional or second color information is desirable on the first side of the sheet , no lead edge to trail edge reversal is required . of course , the return of the sheets for duplex or overlay copying may also be accomplished manually . residual toner and debris remaining on photoreceptor belt 10 after each copy is made , may be removed at cleaning station f with a brush cleaning system 70 . referring now to fig2 which shows a cleaning brush system . the fiber brushes 82 are located in a cleaner housing 84 . the fibers 90 rotate against the photoreceptor 10 surface supported by a cleaning roll 86 . the dual insulated fiber brushes 82 rotate in opposite directions 87 , 88 . when these insulated fiber brushes 82 rub against the charging bars ( or flicker bars ) 80 , the triboelectric charge produced will attract and hold one of the toners , either positive (+) or negative (-) depending on the selection of the charging bar and fiber . in the case of the present invention &# 39 ; s system the mono filament brush fiber 90 rubbing against charging bars 80 ( e . g . teflon ) produce a high negative (-) field thus attracting and holding the positive (+) black toner . by using the selected fiber brush material ( e . g . kanecaron ) and flicker bars ( or charging bars ) ( e . g . made of teflon ) 80 the positive black toner is held to the brush fiber tip . an air vacuum 89 is used to remove debris from the brush fibers 90 . alternatively , a different fiber to bar combination that produces a high positive (+) charge would attract and hold the color negative (-) type toners . the specific print mode in which the image push defect is initiated is during color executive mode when only color toner is being used , and the additive ( znst ) is being preferentially developed . referring now to fig3 ( a ), 3 ( b ), and 3 ( c ). fig3 ( a ) shows what occurs in the typical mode of cleaning the photoreceptor . the brush fiber 90 as it rotates against the photoreceptor 10 contacting the surface has a tendency to smear the additive particles 100 ( e . g . znst ). the smearing results from the force of the brush fibers 90 rotational momentum as they land on the additive particle . the present invention of adding positively charged toner to the fiber tips of the cleaning brushes 82 ( see fig2 ) to avoid additive smearing and to control additive film buildup can perform in one of the following ways shown in fig3 ( b ) or 3 ( c ). in fig3 ( b ), it is shown how the black toner ( positive ) 110 attaches to the fiber 90 tip to provide a sort of buffer between the individual fibers 90 and the photoreceptor 10 surface thereby , preventing the brush fibers from smearing the additive particles 100 as the fibers 90 rotate . fig3 ( c ) shows the attachment of black toner ( positive ) 110 and aerosil particles 120 to the brush fibers 90 . the aerosil particles 120 abrade the additive particles 100 ( e . g . znst ) film from the photoreceptor 10 surface . referring now to the specific subject matter of the present invention , shown in fig4 is a control process to monitor the black toner throughput . as shown in fig4 a mass of black toner is placed in the image area 150 in a line pattern . this image area 150 with black toner is called the cleaner brush retone area . the line pattern of toner in the image area are called zip tone lines 145 . the zip tone lines 145 form a line pattern of 8 pixels on , 8 pixels off , providing approximately 40 % area coverage of the image area . a process control patch 140 exists in the interdocument area ( i . e . the non - image area ). in this invention , after the mass of black toner on the cleaner brushes drops below an acceptable limit , the printer will enter the brush retone procedure and begin imaging an internal 14 &# 34 ; black detone image . a process control patch 140 exists in the interdocument area ( i . e . the non - image area ). untransferred images ( narrow black lines ) will pass to the cleaner . the retoning continues until the mass of black toner on the cleaner brushes reaches an upper limit . depending on the detoned state of brushes , all or part of the toner will be attached to the fibers . the machine will resume normal operation and the brushes will begin giving up the black toner . this process is cyclical and can be continued for an unlimited volume . this process is called cleaner brush retone or cbr . the process direction is indicated by the arrow 16 , photoreceptor edges by 170 , and the ground strip by 160 . during the color executive print mode , periodically and automatically turn - off the color development and paper feed systems , turn on the black development system , adjust the pre - transfer , transfer , and preclean dicorotrons and initiate black only imaging in a zip tone ( line pattern ) type document . without paper feed and with selected dicorotron treatment , the untransferred toner is fully removed from the photoreceptor by the cleaner brushes . the negative field generated on the brush fibers will attract and hold the low charged black toner presented to the cleaner during this time thus providing a renewable brush conditioning . in order to prevent the aerosil / zinc stearate film formation , a control algorithm which tracks the approximate rate of black toner being sent to the cleaner as a function of print count in used in the cleaner brush retone ( cbr ) process of the present invention . when the throughput minus the toner depletion weight reaches a predetermined limit , the controls will enact a retone routine which will retone the cleaner brushes . where : mb is the mass of black toner in the cleaner brush in tenths of a milligram . mb will be allowed to vary from 0 to 30 , 000 . np is the number of pitches during which the cleaner brush is turning and ( xxx ) is a non volatile memory ( nvm ) variable which describes the slope of the toner removal rate . initial value for ( xxx ) is 30 . maximum range will be 0 - 255 . pi is the black pixel count in the image area in units of 2 ** 18 pixels ( i . e . 2 to the 18th power ). ( yyy ) is an nvm variable which represents the efficiency with which the cleaner brush retains the black toner sent to it . initial value for ( yyy ) is 22 . the maximum range will be 1 - 255 . pm is the pixel count in the interdocument area in units of 2 ** 18 pixels . it is multiplied by 5 because the toner is not transferred . hence the amount of toner that reaches the cleaner per pixel is approximately 5 times that which reaches the cleaner from the transferred image area . mb will be capped at 30 , 000 which is the assumed saturation mass of toner in the brush . when ( yyy ) pi + 5 ( yyy ) pm is less than ( xxx ) np , mb will be decremented until a lower bound ( zzz ) is reached . the lower bound will be an nvm variable which will be between 0 and 30 , 000 . the initial value will be 15 , 000 . when the lower boundary is reached , the printer will interrupt the printing process and force dead cycles to perform the following functions : color housing will be left on to maintain standard tri - level electrostatics ; black housing will be turned on ; pre - transfer shield voltage , transfer current , and preclean current will be set to special temporary nvm selectable value ; paper feeding will be inhibited ; tri - level electrostatics will be maintained ; the 14 inch black detone document will be run . for each black detoned document mb will be incremented by ( yyy ) pi . this will continue until mb is equal the 30 , 000 cap . runtime feed forward pixel counting and ird control will be maintained for toner dispense during this routine . after completing the designated number of black detone images , one additional cleaning belt cycle will be run before returning the machine to normal run mode . since electrostatics will be maintained during the run , there will be no need for a cycle up convergence . mb will be neither incremented nor decremented during any state other than normal tri - level , black executive or color executive mode run time . all pixel counting and pitch counting will be suspended during diagnostics , txc ( total xerographic convergence ), tc ( toner concentration ) adjust , electrostatic adjust and cycle up . note this routine will be invoked only during normal tri - level , black executive or color executive mode running . for a new build machine or when new cleaner brushes are installed in the field , a full retoning of the brushes will be required . a new diagnostic routine will be required to run a programmable number ( 10 , 20 , 30 , 40 , or 50 ) of prints in the retone mode and set the mbn variable to 30 , 000 . for this diagnostic routine the tri - level mode will be used . all other control conditions will be identical to the runtime routine . while the methods used in these process inventions are described in terms of the black ( i . e . positive ) toner to attract negatively charged film particles , the methods described herein are reversible for negative (-) toners . in recapitulation , the present invention is a process for providing a renewable source of toner to the cleaner brushes thus controlling additive buildup . it is evident that the addition of toner to the cleaner brushes will remove the additive buildup common in color toner . it is also evident that the charge on the brushes can be switched to allow effective cleaning of oppositely charged filming on the photoreceptor surface . the advantage of cbr is that is can be used in the color exec . mode of development . it is , therefore , apparent that there has been provided in accordance with the present ivention , processes for providing a renewable source of toner to the cleaner brushes thus controlling additive buildup that fully satisfies the aims and advantages hereinbefore set forth . while this invention has been described in conjunction with a specific embodiment thereof , it is evident that many alternatives , modifications , and variations will be apparent to those skilled in the art . accordingly , it is intended to embrace all such alternatives , modifications and variations that fall within the spirit and broad scope of the appended claims .