CA1111097A - Charge control system for xerographic machines - Google Patents
Charge control system for xerographic machinesInfo
- Publication number
- CA1111097A CA1111097A CA285,842A CA285842A CA1111097A CA 1111097 A CA1111097 A CA 1111097A CA 285842 A CA285842 A CA 285842A CA 1111097 A CA1111097 A CA 1111097A
- Authority
- CA
- Canada
- Prior art keywords
- photoreceptor
- charge
- charge level
- light
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
- G03G15/0266—Arrangements for controlling the amount of charge
Abstract
CHARGE CONTROL SYSTEM FOR XEROGRAPHIC MACHINES
ABSTRACT OF THE DISCLOSURE
Apparatus for controlling the charge level on the photoconductive surface of a reproduction machine to enhance imaging. A corona generator is used to initially charge the photoconductive surface following which the charge is examined and compared with a preselected reference charge. Where an overcharge is found, a lamp, the illumination intensity of which is matched to the degree of overcharge, is actuated to reduce the charge level on the photoconductive surface to substantially the same as the reference charge. Where an undercharge is found, a supplemental charging device is actuated to the degree necessary to bring the charge level up to the reference charge. The discharge lamp may be combined with the corona generator or be separate therefrom.
An alternate embodiment has a lamp providing a fixed illumination output is provided with a liquid crystal inter-posed between the photoconductive surface and the lamp to control the degree of illumination to which the photoconductive surface is subjected.
ABSTRACT OF THE DISCLOSURE
Apparatus for controlling the charge level on the photoconductive surface of a reproduction machine to enhance imaging. A corona generator is used to initially charge the photoconductive surface following which the charge is examined and compared with a preselected reference charge. Where an overcharge is found, a lamp, the illumination intensity of which is matched to the degree of overcharge, is actuated to reduce the charge level on the photoconductive surface to substantially the same as the reference charge. Where an undercharge is found, a supplemental charging device is actuated to the degree necessary to bring the charge level up to the reference charge. The discharge lamp may be combined with the corona generator or be separate therefrom.
An alternate embodiment has a lamp providing a fixed illumination output is provided with a liquid crystal inter-posed between the photoconductive surface and the lamp to control the degree of illumination to which the photoconductive surface is subjected.
Description
This invention relates to electrostatic reproduction machines, and more particularly to an improved charge control system for use with such machines.
In an electrostatic or xerographic type reproduction machines or copies, the charge level on the machine photo-conductive surface or photoreceptor, is critical to satis-factory operation of the machine. As known to those versed in the art, the photoconductive surface is first charged, desirably to a predet charge level, preparatory to imaging.
The level of this initial charge however, is often critical since too low a charge may result in weak, washed out look-ing copies whereas too high a charge may result in dark copies and overloading of the machine cleaning mechanism.
Normally the charge as aforesaid is placed on the photoconductive surface by a corona generator. Close control over the corona output of devices of this type is often difficult, particularly as the machine components including the corona generator age.
It is therefore an object of an aspect of the present invention to provide a new and improved charge control for xerographic type machines.
It is an object of an aspect of the present invention to provide an improved charge control wherein the initial charge set down by the corona generator is examined and changed as necessary to provide the optimum charge desired.
It is an object of an aspect of the present invention to provide an improved charge control wherein the initial charge set down by the corona generator is examined and reduced as necessary by an illuminator whose illumination intensity is matched to the degree of overcharge.
It is an object of an aspect of the present invention to provide an improved mechanism for changing the charge on a photoreceptor surface in response to the existing charge conditions to provide an optimum photoreceptor charge.
It is an object of an aspect of the present invention to provide a charge control wherein charges on a photoreceptor are auto-matically tailored in response to existing photoreceptor charge conditions to provide an optimized photoreceptor charge.
Various aspects of the invention are as follows:
In an electrostatic type reproduction machine for producing copies of an original, the machine having a photo-receptor, means for charging the photoreceptor in prepara-tion for imaging, exposure means for exposing the charged photoreceptor to the original whereby to create a latent electrostatic image of the original on the photoreceptor, developing means for developing the latent electrostatic image on the photoreceptor, and transfer means for trans-ferring the developed image to a sheet of copy material, the combination comprising: a. means for generating a charge level signal reflecting the charge level of said photoreceptor following charging by said charging means;
b. light means for illuminating said photoreceptor to reduce the charge level of said photoreceptor, said light means reducing the charge level on said photoreceptor in proportion to the intensity of the light produced by said light means; and c. control means for regulating the intensity of said light means in response to said charge level signal.
, ~ 2 The method of controlling the operating charge level on the photoreceptor of an electrostatic type reproduction machine for producing copies of an original, comprising the steps of: generating a charge level signal reflect-ing the charge level of said photoreceptor followingphotoreceptor charging and illuminating said photoreceptor with an intensity proportional to said charge level signal to reduce the charge level of said photoreceptor.
Other objects and advantages will be apparent from the ensuing description and drawings in which:
Figure 1 is a schematic sectional view of an electro-static reproduction machine incorporating the charge control system of the present invention;
Figure 2 is an isometric view showing details of the ch~rge control apparatus of the present invention; and ~` Figure 3 is a circuit schematic of one embodiment of the photoreceptor charge control system of the present invention for reducing or increasing photoreceptor charge.
Figure ~ is a circuit schematic of another embodiment of .he charge control system of ~he present invention for reducing ~hotoreceptor charge.
Figure 5 ~s a circuit schematic of an alternate embodiment wherein a fixed light source with liquid crystal regulator is provided for controlling the intensity of the light shone upon the photoconductive surface for reducing photoreceptor charge.
For a general understanding of the invention, an exemplary copier/reproduction machine in which .he invention may be incorporated, is shown in Figure 1. The reproduction or copying machine, is there designated generally by the numeral 5.
A document 11 to be copied is placed upon a trans-parent support platen 16 fixedly arranged in an illumination assembly, generally indicated by the reference numeral 10, positioned at the left end of the machine 5. Light rays from an illumination system are flashed upon the document to pro-duce image rays corresponding to the information~areas. The _ _ __image rays are projected by means of an optical system onto the photosensitive surface of a xerographic plate in the form of a flexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 9.
The belt 12 comprises a photoconductive layer 15 of selenium which is the light receiving surface and imaging medium for the apparatus, on a conductiVe backing. The sur-face of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device 13, which is connected to a power source 68.
The belt ls journaled for continuous movement upon three rollers 20, 21 and 22 positioned with their axis in parrallel. The photoconductlve belt assembly 9 is slidably mounted upon two support shafts 23 and 24, with the roller 22 rotatably supported on the sha,~. 23 which is secured to the frame of the apparatus and is rotatably driven by a suit-able motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the reflected light image of such original document positioned on the platen is flashed on the surface 15 of belt 12 to pro-duce an electrostatic latent image thereon at exposure station 27.
The electrostatic latent image on the moving belt 12 passes through a developing station 28 in which there is positioned a magnetic brush developing apparatus, generally indicated by the reference numeral 30, and which provides development of the electrostatic image by means of multiple brushes as the same moves through the development zone.
The developed electrostatic image is carried on belt 12 to transfer station 29 whereat a sheet 6 of copy paper is fed between transfer roller 7 and belt 12 at a speed in synchronism with the moving belt to transfer the developed image to sheet 6 without blurring. A sheet transport mechanism, generally indicated at 17, brings sheets 6 from paper supply tray 18 or 18' to the transfer station 29 at the proper time to match the arrival of the sheet with the arrival of the developed image on belt 12.
Following transfer, the image bearing sheet is separated from belt 12 and conveyed to a fuser assembly, gen-erally indicated by the reference numeral l9, wherein the developed powder image on the sheet is permanently affixed thereto. ~fter fusing, the finished copy is discharged from the apparatus into a suitable collector, i.e. tray 8. Residual toner particles and any other residue left on belt 12 are removed by brush 26 at cleaning station 25. Further details regarding the structure of the belt assembly 9 and its rela-tionship with the machine and support therefor may be found _5_ . , . ' s, ~7 in U. S. Patent No. 3,730,623 issued May 1, 1973 and assigned to the same assignee.
As will be understood by those skilled in the art, development of the latent electrostatic image formed on belt 12 is dependent upon the voltage differential between the light image and the developing means. This voltage differential, which may be described as a xerographic development field, serves to attract toner to the latent electrostatic image in accordance with the image outline and density requirements to faithfully reproduce the original being copied.
Referring now to Figures 2 and 3 of the drawings, the charge control 50 of the present invention preferably includes both a supplemental charging section 52 and a charge reducing section 54. As will appear, supplemental charging section 52 is utilized to automatically increase the charge level on the photoconductive surface 15 of belt 12 where the original charge level provided by the corona generating device 13 is found to be too low while charge reducing section 54 is utilized to auto-matically reduce the charge on surface 15 where the original charge is found to be too high. In this way an optimized charge is provided on the photoconductive surface 15.
Supplemental charging section 52 includes a corona discharge wire 61 and adjoining shield 63. Shield 63 is formed from metal and in the arrangement shown, has, when viewed in cross-section, a ~enerally inverted U-shape with top wall 65, depending side walls 66, 67, and end walls 62, 64. Corona wlre 61 is strung between end walls 62, 64 of shield 63. To prevent shorting of corotron wire 61 to metal shield 63, suitable electrical insulators 69 are provided between wire 61 and the ends 62, 64 of shield 63. It will be understood that where corotron shield is composed of an electrical insulating material such as plastic, insulators 69 and, as will appear conductive layer 80, may be dispensed ~Jith.
Charge reducing section 54 of charge control device 50 includes a generally rectangular electro-luminescent panel 70, the length and width dimensions of which are equal to or slightly less than the corresponding length and width dimensions of shield 63, mounted within the shield interior on the inside surface of the shield upper wall 65. One suitable electro-luminescent panel is type 94-0150-1 manufactured by Grimes Manufacturing Co., Urbana, Ohio.
To prevent build-up of static electrical charges on the electro-luminescent panel 70, the exposed or lower surface 71 of panel 70 is covered with a clear conductive material, preferably a thin layer 80 of NESA glass. Conductive layer 80 is electrically coupled to shield 63 through contact with side walls 66, 67 of shield 63. It will be understood that where shield 63 is formed from a non-conductive material, i.e. plastic conductive layer 80 may be dispensed with.
A preset reference signal, which appears in lead 91, is developed from a suitable d.c. voltage source shown in exemplary fashion as battery llO. Battery llO is coupled across voltage level controller 90, shown as a potentiometer serving to regulate the voltage level of the reference signal in lead 91 in accordance with the setting thereof to provide a predet reference signal. The reEerence signal in lead 91 is applied via resistor 92 to one input of voltage comparator 93.
Powe:r input to cotona discharge wire 61 of supplemental charging section 52 and electro-luminescent panel 70 of charge reducing section 54 is derived from viariable d.c. power source 7~, the output of which to either section 52 or section 54 is regulated in accordance with charge conditions of the photo-sensitive surface 15 of belt 12 as sensed by a d.c. type electro-meter 100`. Probe 102 of electrometer 100 is mo~nted in machine 5 in predetermined spaced relationship to .he photoconductive surrace 15 as will be understood by those skilled in the art.
~n a preferred embodiment, probe 102 is disposed downstream of the charge control device 50 but before the developing station 30.
Other probe locations, however, may be contemplated.
The d.c. signal output from probe 102, representative of the charge on the photoconductive surface 15, is inputted via lead 103 to the main body 106 of of electrometer 100 wherein the signal is suitably amplified. The signal output of electro-meter 100 appears in lead 9~ to d.c. power source 74. One type o' d.c. electrometer that can be employed in both embodiments of Figures 3 and 4 are described U.S. Patent 3,852,668 issued on December 3, 1974 in the name of James M. Hardenbrook et al.
Other electxometers including those of the a.c. type may instead be contemplated.
Power source i4 includes a voltage comparator 93, which may comprise any suitable circuit effective to compare voltage levels inpplied thereto and generate an analog signal proportional to the difference between the input signal voltages.
In the exemplary ci-cuit illustrated, comparator 93 comprises an operational amplifier, operative to compare the preset control signal from controller 90 with the signal output of electrometer 100, tha latter being reprasentative of the charge level on the photo-conductive surface 15 of belt 12. Variable resistance controls the gain of comparator 93.
The signal output of comparator 93 is applied via lead 96 to the base electrodes of P~P transistor 97 and ~P~ transistor 98 respactively. The collector of transistor 97 is connected .`~7 by lead 99 to electro-luminescent panel 70. Lead 101 couples the emitter of transistor 97 to a suitable source of positive potential, represented herein by battery 112.
Lead 104 couples the collector of transistor 98 with the input side of a conventional d.c. to d.c. converter 105. The output of converter 105, which is used to drive charging section 52 of charge control device 50, is connected by lead 107 with corona generating wire 61. Lead 108 couples the emitter of transistor 98 with a suitable source of negative potential represented herein by battery 109.
D.C. to d.c. converter 105 serves to amplify the relatively low power variable signal output of transistor 98 to the relatively high power level required to drive charging section 52. Any suitable commereially available d.e. to d.c.
converter having the neeessary operating speeifieations may be used for this purpose.
In operation, the optimum eharge level of the photocon-ductive surface 15 of belt 12 is determined, and the signal out-put of electrometer 100 corresponding to the optimum charge level is matched with the reference signal in lead 91. This may be effected by adjusting the setting of controller 90 until the ma~ching signal potential is reached. So long as the charge level on the photoconductive surface 15 remains at the level desired, the signal inputs in leads 91, 94 to comparator 93 match, and the signal output from comparator ~3 to lead 96 holds transistors 97, 98 in a blocking state. As a result, both the supplemental charging section 52 and charge reducing section 54 of charge control 50 are inoperative.
Should the charge level on the photoconductive surface 15 rise above the level desired, as represented by the setting _g_ o~ controller 90, the vol~ag~e potential of the output si~nal from electrometer 100 in lead 9~ rises. Compar~tor 93 responds by generating a positive signal output, the potential of which is proportional to the difference in potential ~etween the input signals to comparator 93 in leads 91, 9~. Transistor 97 feeds a proportional amount of power to electro-luminescent panel 70 to turn panel 70 on and illuminate the photoconductive surface with an intensity proportional to the streng-th of the signal output from comparator 93. Light from panel 70 reduces the charge level on the photoconductive surface 15 to bring the charge level back to the optimum level desired.
Should the charge level on the photoconductive surface 15 fall below the optimum level desired, the voltage potential of the output signal from electrometer 100 in lead 94 falls.
Comparator 93 responds by generating a negative signal output, the potential of which is proportional to the difference in potential between the signal inputs to comparator 93 in leads 91, 94. Transistor 98 feeds a proportional amount of power, which is raised to the requisite power level necessary by d.c.
to d.c. converter, to corona discharge wire 61 of supplemental charging section 52. The resulting corona emissions from w~re 61 add to or supplement the charge previously applied to the photoconductive surface 15 by corona generating device 13 to bring the charge level back to the optimum level desired.
While supplemental charging section 52 and charge reducing section 54 are combined herein to provide a unitary charge control 50, it will be understood -that supplemental charging sect:ion 52 and charge reducing section 54 may comprise separate and discrete entities. In Figure 4, charge reducing section 54 has been combined with the primary corona generation device 13 thereby el-minating the need for a separate charge control 50 as depicted in Figure 1.
- The corona generaling device 13 includes the corona discharge wire ol and shield 63. Shield 63 is formed from metal and in the arrangement shown, has ~hen viewed in cross-section, a generally inverted U-shape with top wall 65, depending side walls 66, o7, and e~d walls 62, 64. Corona wire 51, which is electrically coupled to a suitable d.c. power source, represented in exemplary rashion by battery 68, is strung between end walls 62,6A of shield 63, as shown in Figure 2 shorting of corotron wire 61 to metal shield 63, suitable electrical insulators 69 would be provided between wire 61 and the ends 62,6~ of shield 63.
As in ~he case o' the Figure 3 embodiment, charge control section 54 includes a generally rectangular electro-luminescent panel 70, the length and width dimensions of which are equal to or slightly less than the corresponding length and width dimensions o shield 63, mounted within the shield interior on the inside surface of the shield upper wall 65. Also, panel 70 is electrically connected to a variable power supply 74 by lead 98.
To prevent build-up of static electrical charges on the electro-luminescent panel 70, the ex?osed or lower surface 71 of panel 70 is covered with a clear conductive material, preferably a thin layer 80 of NESA glass. Conductive layer 80 is electrically coupled to shield 63 through contact with side walls 66, 67 of shield 63.
Power supply 7a in this e~bodiment is similar to that of Figure 3 and therefore, like parts have the same referen~e numerals.
A suitable cource of d.c control voltage is provided in the forms of battery 110. Battery 110 is coupled across voltage level controller 90, which is a potentiometer serving to regulate the control voltage provided to voltage comparator 93 in accordance with the setting thereof. The output signal of controller 90 in lead 91 thereof, which serves a a reference potential, if coupled through resistor 92 with one in~)ut of voltage comparator 93.
Lead 94 couples the other input of comparator 93 with a device ~hich generates an output signal indicative of the charge level on the photoconductive sur~ace 15 o~ belt 12 following charging by corona generating ~evice 13. In the exemplary arrangement sho~, the charge measuring device com-prises a d.c. t~pe electrometer 100. Probe 102 of electrometer 100 is mounted in machine 5 in predetermined spaced relationship to the photoconductive surface 15 as will be understood by those skilled in the art. In a preferred embodiment, probe 102 is disposed downstream of the corona generating device 13, but before developing station 30.
The d.c. signal output ~rom probe 102, representative of the charge on the photoconductive surface 15, is connected by lead 103 to the main body 106 of electrometer 100, w~erein ~he signal is suitably ampliried. The signal from electrometer 100 is provided to the input gate of comparator 93 through lead 94.
Comparator 93 may comprise any suitable circuit effective to compare voltage levels supplied thereto and gen-erate an analog signal proportional to the di~ference between the input signal voltages. In the exemplary circuit illustrated, comparator 93 comprises an operational amplifier, operative to compare the signal outputs of controller 90 and electrometer 100, the latter signal bring representative of the charge level on the photoconductive surface 15 of belt 12. The signal output of com-parator 93 is supplied through lead 96 to the bas2 electrode of control transistor 79. Lead 99 couples the emitter of transistor to panel 70 while lead 101 couples the collector of transistor 79 to a suitable power source shown here as battery 112. Control trans-istor 79 regulates the power input to panel 70 in response to the output signal ~rom comparator 93 to control the level of illumination of panel 70. Variable resistor 114 controls the gain of comparator 93.
vi~7 During the operational cycle of reproduction machine 5, the photoconductive surface 15 of belt 12 is charged by the corona generating device 13 and e~posed at e~posure station 27 to the original 11 being copied to produce a latent electro-static image of original 11 on the surface 15 of belt 12. The latent electrostatic image so for~ed is carried past developer station 28 ~;~ereat the image is develped. The developed image t'nen passes to transfer station 29 where the developed image is transferred to a sheet 6 of copy paper brought forward from supply tray 18 or 18' by transport 17 at the proper time so as to assure registration of the developed image on belt 12 with the sheet 6. The copy sheet 6 bearing the developed image is tnereafter transported to fuser 19 where the image is fixed, following which the final copy is discharged into tray 8.
Electrometer 100 monitors the charge level on the portion of the photoconductive surface 15 of belt 12 viewed by probe 102. The signal ouptut of electrometer 100 is fed to comparator 93 w~ere the signal from electrometer 100 is com-pared with the preset reference signal from voltage level con-troller 90. So long as the voltages of the signal inputs to comparator 93 are substantially identical, LLd~si~LoL 79 ~oes---n~L
conduct and there is no flow of current to panel 70. As a result, electro-luminescent panel 70 is not illuminated. ~`~~ ~~~~^~~~-~~~~ ~
Where the signal imputs to comparator 93 are unbal-anced, reflec~ing charging of the photocinductive surface 15 to a level greater than that represented by the reference ~ol-tage in lead 91, transistor 79 conducts and provides power to panel 70 in proportion to the voltage level of the signal on lead 96 being proportional to the difference in.potential between the signal on lead 91, and the signal on lead 94. The resulting current flow in lead 99 to the electro-luminescent panel 70 energizes panel 70 to produce an illumination whose intensity will be pro-portional to the power supplied thereto. Illumination from panel g7 70 reduces the charge on the photoconductive surface 15 or belt 12 in proportion ~o the amount of illumination.
~ hile the charge generating device 13 and charge control section 54 mav be combined into one unitary device, they may comprise se~arate discrete entities as is true in the arrangement sho~ in Figure 5. There, the cha~ge generating section comprises a corona generator device 13' while the charge control section comprises a modified version 54' of the variable illumination device shown in Figure ~.
Referring now to Figure 5, wherein liXe numerals refer to like parts, electro-luminescent panel 70 is mounted within a generally inverted U-shaped shield 165, panel 70 being disposed against the inside face of the shield upper wall 166.
Shield 165 is supported by suitable means (not shown) in transverse relationship to belt 12 at some convenient point along the belt run. In the arrangement illustrated, shield 165 is dis-posed adjacent to and downstream of corona generator 13'.
~ s will appear, panel 70 serves as the source of illumination with control o~er the amount of light directed onto the photoconductive surface 15 of belt 12 being effected by means of liquid crystal 170 in response to the charge con-ditions of the photoconductive surface. In this embodiment, the side of electro-luminescent panel 70 facing the photocon-ductive surface of belt 12 is overlayed with a liquid crystal 170, crystal 170 preferably being sized and conEigured so as to cover the entire side of panel 70. Suitable light polarizers 168, 169 such as manufactured by Polaroid Corporation under the trade name Polaroid sheet are disposed between panel 70 and liquid crystal :L70, and on the side 171 of cr~stal 170 facing the photoconductive surface 15.
Liquid crystal 170 comprises any suitable liquid crystal of the so-called field effect type wherein the light transmissitivity thereof varies in response to the electric current applied thereof. A liquid crystal suitable for this purpose iis manufactured by ~amlin, ~nc., Lake ~ills, Wisc.
In the arrange~ent shown, tne light trans~issitlvity of liauid crystal 170, and hence the amount of light directed onto the photoconductive surface, is regulated in response to the charge conditions of the photoconductive surface 15.
The output of variable T ower source 74, which is representa-tive of the charge level of the photoconductive surface 15 o_ belt 12 as described heretofore, is applied via lead 98 to liquid crystal 170 to control the light transmissitivity thereof.
Panel 70 in this embodiment serves as the licht source wlth a constant intensity or illumination and is driven from a suit-able power source such as battery 172 through lead 173. On/off switch 174 in lead 173 permits panel 70 to be turned off, as during periods when machine 5 is not in use.
Corona generator device 13, like device 13 of Figure 1, comprises any suitable d.c., a.c., or a.c./d.c. type corona charg-ing device as known to those sXilled in the copier arts. In the arrangement illustrated, the corona generating device 13' includes a corona emitting wire 83 supported within shield 84 and coupled to a suitable source of power, e~emplified by battery 85.
In operation, switch 174 is closed to energize electro-luminescent panel 70 continuously. The amount of light, if any, transmitted by liquid crystal 170 onto the photoconductive surface 15 is varied in response to the strength of the signal in output lead 98 of variable power supply 74, which in turn is represen-tative of the charge level on the photoconductive surface 15.
Where the charge on surface 15 is at the level desired, the signal in lead 98 to crystal 170 causes molecular turbulence which renders crystal 170 opaque with the result that light from panel 70 to the photoconductive surface 15 is partially or completely b:Locked. T,~here the signal in lead 98 reflects overcharging o the photoconductive surface 15, molecular re-orientation of the molecules within crystal 170 proportional y in degree to the signal strength occurs with the result that crystal 170 transmits a proportlonal amount of light from panel 70 therethrough onto the photoconductive surface 15.
The light, thus, reduces the charge level on the photoconductive surface 15 in proportion to the light intensity.
The corona generating device 13' and c~arge control 5A ~ may be combined as a single unlt. In that event, shield 165 would be dis?ensed with and the liquid crystal 170 would instead be disposed inside shield 8~ of corona generator 13'.
In the event shield 84 is formed from a conductive material, a conductive transparent layer, such as the conductive layer 80 shown and described in the Figure 4 embodiment, would preferably be disposed over the polarizer 169 facing the photoconductive surface 15.
While the light source has been illustrated and described as comprising an electro-luminescent panel 70, other suitable light sources who intensity may be varied can be contemplated.
.. ..
~16-' ~ ' ' ' ~, ' , :
In an electrostatic or xerographic type reproduction machines or copies, the charge level on the machine photo-conductive surface or photoreceptor, is critical to satis-factory operation of the machine. As known to those versed in the art, the photoconductive surface is first charged, desirably to a predet charge level, preparatory to imaging.
The level of this initial charge however, is often critical since too low a charge may result in weak, washed out look-ing copies whereas too high a charge may result in dark copies and overloading of the machine cleaning mechanism.
Normally the charge as aforesaid is placed on the photoconductive surface by a corona generator. Close control over the corona output of devices of this type is often difficult, particularly as the machine components including the corona generator age.
It is therefore an object of an aspect of the present invention to provide a new and improved charge control for xerographic type machines.
It is an object of an aspect of the present invention to provide an improved charge control wherein the initial charge set down by the corona generator is examined and changed as necessary to provide the optimum charge desired.
It is an object of an aspect of the present invention to provide an improved charge control wherein the initial charge set down by the corona generator is examined and reduced as necessary by an illuminator whose illumination intensity is matched to the degree of overcharge.
It is an object of an aspect of the present invention to provide an improved mechanism for changing the charge on a photoreceptor surface in response to the existing charge conditions to provide an optimum photoreceptor charge.
It is an object of an aspect of the present invention to provide a charge control wherein charges on a photoreceptor are auto-matically tailored in response to existing photoreceptor charge conditions to provide an optimized photoreceptor charge.
Various aspects of the invention are as follows:
In an electrostatic type reproduction machine for producing copies of an original, the machine having a photo-receptor, means for charging the photoreceptor in prepara-tion for imaging, exposure means for exposing the charged photoreceptor to the original whereby to create a latent electrostatic image of the original on the photoreceptor, developing means for developing the latent electrostatic image on the photoreceptor, and transfer means for trans-ferring the developed image to a sheet of copy material, the combination comprising: a. means for generating a charge level signal reflecting the charge level of said photoreceptor following charging by said charging means;
b. light means for illuminating said photoreceptor to reduce the charge level of said photoreceptor, said light means reducing the charge level on said photoreceptor in proportion to the intensity of the light produced by said light means; and c. control means for regulating the intensity of said light means in response to said charge level signal.
, ~ 2 The method of controlling the operating charge level on the photoreceptor of an electrostatic type reproduction machine for producing copies of an original, comprising the steps of: generating a charge level signal reflect-ing the charge level of said photoreceptor followingphotoreceptor charging and illuminating said photoreceptor with an intensity proportional to said charge level signal to reduce the charge level of said photoreceptor.
Other objects and advantages will be apparent from the ensuing description and drawings in which:
Figure 1 is a schematic sectional view of an electro-static reproduction machine incorporating the charge control system of the present invention;
Figure 2 is an isometric view showing details of the ch~rge control apparatus of the present invention; and ~` Figure 3 is a circuit schematic of one embodiment of the photoreceptor charge control system of the present invention for reducing or increasing photoreceptor charge.
Figure ~ is a circuit schematic of another embodiment of .he charge control system of ~he present invention for reducing ~hotoreceptor charge.
Figure 5 ~s a circuit schematic of an alternate embodiment wherein a fixed light source with liquid crystal regulator is provided for controlling the intensity of the light shone upon the photoconductive surface for reducing photoreceptor charge.
For a general understanding of the invention, an exemplary copier/reproduction machine in which .he invention may be incorporated, is shown in Figure 1. The reproduction or copying machine, is there designated generally by the numeral 5.
A document 11 to be copied is placed upon a trans-parent support platen 16 fixedly arranged in an illumination assembly, generally indicated by the reference numeral 10, positioned at the left end of the machine 5. Light rays from an illumination system are flashed upon the document to pro-duce image rays corresponding to the information~areas. The _ _ __image rays are projected by means of an optical system onto the photosensitive surface of a xerographic plate in the form of a flexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 9.
The belt 12 comprises a photoconductive layer 15 of selenium which is the light receiving surface and imaging medium for the apparatus, on a conductiVe backing. The sur-face of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device 13, which is connected to a power source 68.
The belt ls journaled for continuous movement upon three rollers 20, 21 and 22 positioned with their axis in parrallel. The photoconductlve belt assembly 9 is slidably mounted upon two support shafts 23 and 24, with the roller 22 rotatably supported on the sha,~. 23 which is secured to the frame of the apparatus and is rotatably driven by a suit-able motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the reflected light image of such original document positioned on the platen is flashed on the surface 15 of belt 12 to pro-duce an electrostatic latent image thereon at exposure station 27.
The electrostatic latent image on the moving belt 12 passes through a developing station 28 in which there is positioned a magnetic brush developing apparatus, generally indicated by the reference numeral 30, and which provides development of the electrostatic image by means of multiple brushes as the same moves through the development zone.
The developed electrostatic image is carried on belt 12 to transfer station 29 whereat a sheet 6 of copy paper is fed between transfer roller 7 and belt 12 at a speed in synchronism with the moving belt to transfer the developed image to sheet 6 without blurring. A sheet transport mechanism, generally indicated at 17, brings sheets 6 from paper supply tray 18 or 18' to the transfer station 29 at the proper time to match the arrival of the sheet with the arrival of the developed image on belt 12.
Following transfer, the image bearing sheet is separated from belt 12 and conveyed to a fuser assembly, gen-erally indicated by the reference numeral l9, wherein the developed powder image on the sheet is permanently affixed thereto. ~fter fusing, the finished copy is discharged from the apparatus into a suitable collector, i.e. tray 8. Residual toner particles and any other residue left on belt 12 are removed by brush 26 at cleaning station 25. Further details regarding the structure of the belt assembly 9 and its rela-tionship with the machine and support therefor may be found _5_ . , . ' s, ~7 in U. S. Patent No. 3,730,623 issued May 1, 1973 and assigned to the same assignee.
As will be understood by those skilled in the art, development of the latent electrostatic image formed on belt 12 is dependent upon the voltage differential between the light image and the developing means. This voltage differential, which may be described as a xerographic development field, serves to attract toner to the latent electrostatic image in accordance with the image outline and density requirements to faithfully reproduce the original being copied.
Referring now to Figures 2 and 3 of the drawings, the charge control 50 of the present invention preferably includes both a supplemental charging section 52 and a charge reducing section 54. As will appear, supplemental charging section 52 is utilized to automatically increase the charge level on the photoconductive surface 15 of belt 12 where the original charge level provided by the corona generating device 13 is found to be too low while charge reducing section 54 is utilized to auto-matically reduce the charge on surface 15 where the original charge is found to be too high. In this way an optimized charge is provided on the photoconductive surface 15.
Supplemental charging section 52 includes a corona discharge wire 61 and adjoining shield 63. Shield 63 is formed from metal and in the arrangement shown, has, when viewed in cross-section, a ~enerally inverted U-shape with top wall 65, depending side walls 66, 67, and end walls 62, 64. Corona wlre 61 is strung between end walls 62, 64 of shield 63. To prevent shorting of corotron wire 61 to metal shield 63, suitable electrical insulators 69 are provided between wire 61 and the ends 62, 64 of shield 63. It will be understood that where corotron shield is composed of an electrical insulating material such as plastic, insulators 69 and, as will appear conductive layer 80, may be dispensed ~Jith.
Charge reducing section 54 of charge control device 50 includes a generally rectangular electro-luminescent panel 70, the length and width dimensions of which are equal to or slightly less than the corresponding length and width dimensions of shield 63, mounted within the shield interior on the inside surface of the shield upper wall 65. One suitable electro-luminescent panel is type 94-0150-1 manufactured by Grimes Manufacturing Co., Urbana, Ohio.
To prevent build-up of static electrical charges on the electro-luminescent panel 70, the exposed or lower surface 71 of panel 70 is covered with a clear conductive material, preferably a thin layer 80 of NESA glass. Conductive layer 80 is electrically coupled to shield 63 through contact with side walls 66, 67 of shield 63. It will be understood that where shield 63 is formed from a non-conductive material, i.e. plastic conductive layer 80 may be dispensed with.
A preset reference signal, which appears in lead 91, is developed from a suitable d.c. voltage source shown in exemplary fashion as battery llO. Battery llO is coupled across voltage level controller 90, shown as a potentiometer serving to regulate the voltage level of the reference signal in lead 91 in accordance with the setting thereof to provide a predet reference signal. The reEerence signal in lead 91 is applied via resistor 92 to one input of voltage comparator 93.
Powe:r input to cotona discharge wire 61 of supplemental charging section 52 and electro-luminescent panel 70 of charge reducing section 54 is derived from viariable d.c. power source 7~, the output of which to either section 52 or section 54 is regulated in accordance with charge conditions of the photo-sensitive surface 15 of belt 12 as sensed by a d.c. type electro-meter 100`. Probe 102 of electrometer 100 is mo~nted in machine 5 in predetermined spaced relationship to .he photoconductive surrace 15 as will be understood by those skilled in the art.
~n a preferred embodiment, probe 102 is disposed downstream of the charge control device 50 but before the developing station 30.
Other probe locations, however, may be contemplated.
The d.c. signal output from probe 102, representative of the charge on the photoconductive surface 15, is inputted via lead 103 to the main body 106 of of electrometer 100 wherein the signal is suitably amplified. The signal output of electro-meter 100 appears in lead 9~ to d.c. power source 74. One type o' d.c. electrometer that can be employed in both embodiments of Figures 3 and 4 are described U.S. Patent 3,852,668 issued on December 3, 1974 in the name of James M. Hardenbrook et al.
Other electxometers including those of the a.c. type may instead be contemplated.
Power source i4 includes a voltage comparator 93, which may comprise any suitable circuit effective to compare voltage levels inpplied thereto and generate an analog signal proportional to the difference between the input signal voltages.
In the exemplary ci-cuit illustrated, comparator 93 comprises an operational amplifier, operative to compare the preset control signal from controller 90 with the signal output of electrometer 100, tha latter being reprasentative of the charge level on the photo-conductive surface 15 of belt 12. Variable resistance controls the gain of comparator 93.
The signal output of comparator 93 is applied via lead 96 to the base electrodes of P~P transistor 97 and ~P~ transistor 98 respactively. The collector of transistor 97 is connected .`~7 by lead 99 to electro-luminescent panel 70. Lead 101 couples the emitter of transistor 97 to a suitable source of positive potential, represented herein by battery 112.
Lead 104 couples the collector of transistor 98 with the input side of a conventional d.c. to d.c. converter 105. The output of converter 105, which is used to drive charging section 52 of charge control device 50, is connected by lead 107 with corona generating wire 61. Lead 108 couples the emitter of transistor 98 with a suitable source of negative potential represented herein by battery 109.
D.C. to d.c. converter 105 serves to amplify the relatively low power variable signal output of transistor 98 to the relatively high power level required to drive charging section 52. Any suitable commereially available d.e. to d.c.
converter having the neeessary operating speeifieations may be used for this purpose.
In operation, the optimum eharge level of the photocon-ductive surface 15 of belt 12 is determined, and the signal out-put of electrometer 100 corresponding to the optimum charge level is matched with the reference signal in lead 91. This may be effected by adjusting the setting of controller 90 until the ma~ching signal potential is reached. So long as the charge level on the photoconductive surface 15 remains at the level desired, the signal inputs in leads 91, 94 to comparator 93 match, and the signal output from comparator ~3 to lead 96 holds transistors 97, 98 in a blocking state. As a result, both the supplemental charging section 52 and charge reducing section 54 of charge control 50 are inoperative.
Should the charge level on the photoconductive surface 15 rise above the level desired, as represented by the setting _g_ o~ controller 90, the vol~ag~e potential of the output si~nal from electrometer 100 in lead 9~ rises. Compar~tor 93 responds by generating a positive signal output, the potential of which is proportional to the difference in potential ~etween the input signals to comparator 93 in leads 91, 9~. Transistor 97 feeds a proportional amount of power to electro-luminescent panel 70 to turn panel 70 on and illuminate the photoconductive surface with an intensity proportional to the streng-th of the signal output from comparator 93. Light from panel 70 reduces the charge level on the photoconductive surface 15 to bring the charge level back to the optimum level desired.
Should the charge level on the photoconductive surface 15 fall below the optimum level desired, the voltage potential of the output signal from electrometer 100 in lead 94 falls.
Comparator 93 responds by generating a negative signal output, the potential of which is proportional to the difference in potential between the signal inputs to comparator 93 in leads 91, 94. Transistor 98 feeds a proportional amount of power, which is raised to the requisite power level necessary by d.c.
to d.c. converter, to corona discharge wire 61 of supplemental charging section 52. The resulting corona emissions from w~re 61 add to or supplement the charge previously applied to the photoconductive surface 15 by corona generating device 13 to bring the charge level back to the optimum level desired.
While supplemental charging section 52 and charge reducing section 54 are combined herein to provide a unitary charge control 50, it will be understood -that supplemental charging sect:ion 52 and charge reducing section 54 may comprise separate and discrete entities. In Figure 4, charge reducing section 54 has been combined with the primary corona generation device 13 thereby el-minating the need for a separate charge control 50 as depicted in Figure 1.
- The corona generaling device 13 includes the corona discharge wire ol and shield 63. Shield 63 is formed from metal and in the arrangement shown, has ~hen viewed in cross-section, a generally inverted U-shape with top wall 65, depending side walls 66, o7, and e~d walls 62, 64. Corona wire 51, which is electrically coupled to a suitable d.c. power source, represented in exemplary rashion by battery 68, is strung between end walls 62,6A of shield 63, as shown in Figure 2 shorting of corotron wire 61 to metal shield 63, suitable electrical insulators 69 would be provided between wire 61 and the ends 62,6~ of shield 63.
As in ~he case o' the Figure 3 embodiment, charge control section 54 includes a generally rectangular electro-luminescent panel 70, the length and width dimensions of which are equal to or slightly less than the corresponding length and width dimensions o shield 63, mounted within the shield interior on the inside surface of the shield upper wall 65. Also, panel 70 is electrically connected to a variable power supply 74 by lead 98.
To prevent build-up of static electrical charges on the electro-luminescent panel 70, the ex?osed or lower surface 71 of panel 70 is covered with a clear conductive material, preferably a thin layer 80 of NESA glass. Conductive layer 80 is electrically coupled to shield 63 through contact with side walls 66, 67 of shield 63.
Power supply 7a in this e~bodiment is similar to that of Figure 3 and therefore, like parts have the same referen~e numerals.
A suitable cource of d.c control voltage is provided in the forms of battery 110. Battery 110 is coupled across voltage level controller 90, which is a potentiometer serving to regulate the control voltage provided to voltage comparator 93 in accordance with the setting thereof. The output signal of controller 90 in lead 91 thereof, which serves a a reference potential, if coupled through resistor 92 with one in~)ut of voltage comparator 93.
Lead 94 couples the other input of comparator 93 with a device ~hich generates an output signal indicative of the charge level on the photoconductive sur~ace 15 o~ belt 12 following charging by corona generating ~evice 13. In the exemplary arrangement sho~, the charge measuring device com-prises a d.c. t~pe electrometer 100. Probe 102 of electrometer 100 is mounted in machine 5 in predetermined spaced relationship to the photoconductive surface 15 as will be understood by those skilled in the art. In a preferred embodiment, probe 102 is disposed downstream of the corona generating device 13, but before developing station 30.
The d.c. signal output ~rom probe 102, representative of the charge on the photoconductive surface 15, is connected by lead 103 to the main body 106 of electrometer 100, w~erein ~he signal is suitably ampliried. The signal from electrometer 100 is provided to the input gate of comparator 93 through lead 94.
Comparator 93 may comprise any suitable circuit effective to compare voltage levels supplied thereto and gen-erate an analog signal proportional to the di~ference between the input signal voltages. In the exemplary circuit illustrated, comparator 93 comprises an operational amplifier, operative to compare the signal outputs of controller 90 and electrometer 100, the latter signal bring representative of the charge level on the photoconductive surface 15 of belt 12. The signal output of com-parator 93 is supplied through lead 96 to the bas2 electrode of control transistor 79. Lead 99 couples the emitter of transistor to panel 70 while lead 101 couples the collector of transistor 79 to a suitable power source shown here as battery 112. Control trans-istor 79 regulates the power input to panel 70 in response to the output signal ~rom comparator 93 to control the level of illumination of panel 70. Variable resistor 114 controls the gain of comparator 93.
vi~7 During the operational cycle of reproduction machine 5, the photoconductive surface 15 of belt 12 is charged by the corona generating device 13 and e~posed at e~posure station 27 to the original 11 being copied to produce a latent electro-static image of original 11 on the surface 15 of belt 12. The latent electrostatic image so for~ed is carried past developer station 28 ~;~ereat the image is develped. The developed image t'nen passes to transfer station 29 where the developed image is transferred to a sheet 6 of copy paper brought forward from supply tray 18 or 18' by transport 17 at the proper time so as to assure registration of the developed image on belt 12 with the sheet 6. The copy sheet 6 bearing the developed image is tnereafter transported to fuser 19 where the image is fixed, following which the final copy is discharged into tray 8.
Electrometer 100 monitors the charge level on the portion of the photoconductive surface 15 of belt 12 viewed by probe 102. The signal ouptut of electrometer 100 is fed to comparator 93 w~ere the signal from electrometer 100 is com-pared with the preset reference signal from voltage level con-troller 90. So long as the voltages of the signal inputs to comparator 93 are substantially identical, LLd~si~LoL 79 ~oes---n~L
conduct and there is no flow of current to panel 70. As a result, electro-luminescent panel 70 is not illuminated. ~`~~ ~~~~^~~~-~~~~ ~
Where the signal imputs to comparator 93 are unbal-anced, reflec~ing charging of the photocinductive surface 15 to a level greater than that represented by the reference ~ol-tage in lead 91, transistor 79 conducts and provides power to panel 70 in proportion to the voltage level of the signal on lead 96 being proportional to the difference in.potential between the signal on lead 91, and the signal on lead 94. The resulting current flow in lead 99 to the electro-luminescent panel 70 energizes panel 70 to produce an illumination whose intensity will be pro-portional to the power supplied thereto. Illumination from panel g7 70 reduces the charge on the photoconductive surface 15 or belt 12 in proportion ~o the amount of illumination.
~ hile the charge generating device 13 and charge control section 54 mav be combined into one unitary device, they may comprise se~arate discrete entities as is true in the arrangement sho~ in Figure 5. There, the cha~ge generating section comprises a corona generator device 13' while the charge control section comprises a modified version 54' of the variable illumination device shown in Figure ~.
Referring now to Figure 5, wherein liXe numerals refer to like parts, electro-luminescent panel 70 is mounted within a generally inverted U-shaped shield 165, panel 70 being disposed against the inside face of the shield upper wall 166.
Shield 165 is supported by suitable means (not shown) in transverse relationship to belt 12 at some convenient point along the belt run. In the arrangement illustrated, shield 165 is dis-posed adjacent to and downstream of corona generator 13'.
~ s will appear, panel 70 serves as the source of illumination with control o~er the amount of light directed onto the photoconductive surface 15 of belt 12 being effected by means of liquid crystal 170 in response to the charge con-ditions of the photoconductive surface. In this embodiment, the side of electro-luminescent panel 70 facing the photocon-ductive surface of belt 12 is overlayed with a liquid crystal 170, crystal 170 preferably being sized and conEigured so as to cover the entire side of panel 70. Suitable light polarizers 168, 169 such as manufactured by Polaroid Corporation under the trade name Polaroid sheet are disposed between panel 70 and liquid crystal :L70, and on the side 171 of cr~stal 170 facing the photoconductive surface 15.
Liquid crystal 170 comprises any suitable liquid crystal of the so-called field effect type wherein the light transmissitivity thereof varies in response to the electric current applied thereof. A liquid crystal suitable for this purpose iis manufactured by ~amlin, ~nc., Lake ~ills, Wisc.
In the arrange~ent shown, tne light trans~issitlvity of liauid crystal 170, and hence the amount of light directed onto the photoconductive surface, is regulated in response to the charge conditions of the photoconductive surface 15.
The output of variable T ower source 74, which is representa-tive of the charge level of the photoconductive surface 15 o_ belt 12 as described heretofore, is applied via lead 98 to liquid crystal 170 to control the light transmissitivity thereof.
Panel 70 in this embodiment serves as the licht source wlth a constant intensity or illumination and is driven from a suit-able power source such as battery 172 through lead 173. On/off switch 174 in lead 173 permits panel 70 to be turned off, as during periods when machine 5 is not in use.
Corona generator device 13, like device 13 of Figure 1, comprises any suitable d.c., a.c., or a.c./d.c. type corona charg-ing device as known to those sXilled in the copier arts. In the arrangement illustrated, the corona generating device 13' includes a corona emitting wire 83 supported within shield 84 and coupled to a suitable source of power, e~emplified by battery 85.
In operation, switch 174 is closed to energize electro-luminescent panel 70 continuously. The amount of light, if any, transmitted by liquid crystal 170 onto the photoconductive surface 15 is varied in response to the strength of the signal in output lead 98 of variable power supply 74, which in turn is represen-tative of the charge level on the photoconductive surface 15.
Where the charge on surface 15 is at the level desired, the signal in lead 98 to crystal 170 causes molecular turbulence which renders crystal 170 opaque with the result that light from panel 70 to the photoconductive surface 15 is partially or completely b:Locked. T,~here the signal in lead 98 reflects overcharging o the photoconductive surface 15, molecular re-orientation of the molecules within crystal 170 proportional y in degree to the signal strength occurs with the result that crystal 170 transmits a proportlonal amount of light from panel 70 therethrough onto the photoconductive surface 15.
The light, thus, reduces the charge level on the photoconductive surface 15 in proportion to the light intensity.
The corona generating device 13' and c~arge control 5A ~ may be combined as a single unlt. In that event, shield 165 would be dis?ensed with and the liquid crystal 170 would instead be disposed inside shield 8~ of corona generator 13'.
In the event shield 84 is formed from a conductive material, a conductive transparent layer, such as the conductive layer 80 shown and described in the Figure 4 embodiment, would preferably be disposed over the polarizer 169 facing the photoconductive surface 15.
While the light source has been illustrated and described as comprising an electro-luminescent panel 70, other suitable light sources who intensity may be varied can be contemplated.
.. ..
~16-' ~ ' ' ' ~, ' , :
Claims (12)
1. In an electrostatic type reproduction machine for producing copies of an original, the machine having a photo receptor, means for charging the photoreceptor in prepara-tion for imaging, exposure means for exposing the charged photoreceptor to the original whereby to create a latent electrostatic image of the original on the photoreceptor, developing means for developing the latent electrostatic image on the photoreceptor, and transfer means for trans-ferring the developed image to a sheet of copy material, the combination comprising: a. means for generating a charge level signal reflecting the charge level of said photoreceptor following charging by said charging means;
b. light means for illuminating said photoreceptor to reduce the charge level of said photoreceptor, said light means reducing the charge level on said photoreceptor in proportion to the intensity of the light produced by said light means; and c. control means for regulating the intensity of said light means in response to said charge level signal.
b. light means for illuminating said photoreceptor to reduce the charge level of said photoreceptor, said light means reducing the charge level on said photoreceptor in proportion to the intensity of the light produced by said light means; and c. control means for regulating the intensity of said light means in response to said charge level signal.
2. The reproduction machine according to claim 1 in which said control means includes means providing a predeter-mined reference signal reflecting optimum charge level of said photoreceptor, and comparator means for comparing said reference signal with said charge level signal, said comparator means producing a control signal for regulating the intensity of said light means.
3. The reproduction machine according to claim 1 in which said light means comprises a constant light source and variable light conducting means disposed between said light source and said photoreceptor, said control means including means for controlling the light transmissitivity of said light conducting means in response to said charge level signal.
4. The reproduction machine according to claim 3 in which said variable light conducting means comprises a liquid crystal.
5. The reproduction machine according to claim 1 including:
supplemental charging means for increasing the charge on said photoreceptor, said control means proportionally actuating one of said light means and said supplemental charging means in response to said charge level signal.
supplemental charging means for increasing the charge on said photoreceptor, said control means proportionally actuating one of said light means and said supplemental charging means in response to said charge level signal.
6. The reproduction machine according to claim 5 in which said supplemental charging means and said light means com-prise a unitary structure.
7. The reproduction machine according to claim 6 in which said light means comprises a variable intensity lamp and transparent conductive means between said lamp and said photoreceptor for reducing static charge build-up.
8. The reproduction machine according to claim 5 in which said charging means includes at least one corona generating device and a housing for said device, said light means forming at least a portion of said housing.
9. The reproduction machine according to claim 5 in which said control means includes for generating a first signal reflecting the optimum charge for said photoreceptor, means for generating a second signal reflecting the exist-ing charge on said photoreceptor, and comparator means for comparing said first and second signals to provide said control signal.
10. The reproduction machine according to claims 5, 8 or 9 in which said light means comprises a variable intensity lamp.
11. The method of controlling the operating charge level on the photoreceptor of an electrostatic type reproduction machine for producing copies of an original, comprising the steps of: generating a charge level signal reflect-ing the charge level of said photoreceptor following photoreceptor charging and illuminating said photoreceptor with an intensity proportional to said charge level signal to reduce the charge level of said photoreceptor.
12. The method according to claim 11 including the steps of: monitoring the charge level on said photoreceptor to determine if the charge level is above or below said pre-selected operating charge level; applying additional charge to said photoreceptor in proportion to the degree of under-charge to bring the charge level on said photoreceptor up to said preselected operating charge level when said photoreceptor charge level is below said preselected operating charge level.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US736,035 | 1976-10-27 | ||
| US05/736,035 US4248519A (en) | 1976-10-27 | 1976-10-27 | Charge control system for xerographic machines |
| US05/736,033 US4105321A (en) | 1976-10-27 | 1976-10-27 | Illuminated charge control system for xerographic machines |
| US736,033 | 1985-05-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111097A true CA1111097A (en) | 1981-10-20 |
Family
ID=27112985
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA285,842A Expired CA1111097A (en) | 1976-10-27 | 1977-08-31 | Charge control system for xerographic machines |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5355031A (en) |
| CA (1) | CA1111097A (en) |
| FR (1) | FR2369604A1 (en) |
| GB (1) | GB1585233A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5521832U (en) * | 1978-07-28 | 1980-02-12 | ||
| JPS5522810U (en) * | 1978-07-28 | 1980-02-14 | ||
| JPS5520714U (en) * | 1978-07-28 | 1980-02-09 | ||
| JPS5521403U (en) * | 1978-07-28 | 1980-02-12 | ||
| JPS5529856A (en) * | 1978-08-24 | 1980-03-03 | Canon Inc | Image former |
| US4456370A (en) * | 1982-11-08 | 1984-06-26 | Xerox Corporation | Charge control system |
| CA1229652A (en) * | 1983-10-03 | 1987-11-24 | Nexpress Solutions, Inc. | Method and apparatus for controlling charge on a photoconductor |
-
1977
- 1977-08-29 FR FR7726167A patent/FR2369604A1/en active Granted
- 1977-08-31 CA CA285,842A patent/CA1111097A/en not_active Expired
- 1977-10-19 JP JP12564977A patent/JPS5355031A/en active Pending
- 1977-10-26 GB GB4454477A patent/GB1585233A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5355031A (en) | 1978-05-19 |
| FR2369604A1 (en) | 1978-05-26 |
| FR2369604B1 (en) | 1984-04-20 |
| GB1585233A (en) | 1981-02-25 |
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| MKEX | Expiry |