CA1070006A - Electrometer apparatus for reproduction machines - Google Patents

Electrometer apparatus for reproduction machines

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Publication number
CA1070006A
CA1070006A CA320,969A CA320969A CA1070006A CA 1070006 A CA1070006 A CA 1070006A CA 320969 A CA320969 A CA 320969A CA 1070006 A CA1070006 A CA 1070006A
Authority
CA
Canada
Prior art keywords
receptacle
probe
test plate
belt
electrometer
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
Application number
CA320,969A
Other languages
French (fr)
Inventor
Charles D. Wilson
Charles J. Urso
John E. Courtney
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xerox Corp
Original Assignee
Xerox Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from US05/552,019 external-priority patent/US3998538A/en
Application filed by Xerox Corp filed Critical Xerox Corp
Priority to CA320,969A priority Critical patent/CA1070006A/en
Application granted granted Critical
Publication of CA1070006A publication Critical patent/CA1070006A/en
Expired legal-status Critical Current

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Abstract

ELECTROMETER APPARATUS FOR REPRODUCTION MACHINES

ABSTRACT OF THE DISCLOSURE

Apparatus to enable potentials applied to various operating components of an electrostatic type reproduction machine to be measured by an electrostatic voltmeter. In one embodiment, the apparatus comprises structures design-ed to place the sensing element of the voltmeter in pre-determined spaced relationship with a test plate, the test plate being electrically connectable to the source of potential to be measured. In another embodiment, the apparatus locates the voltmeter sensing element in pre-determined spaced relation with both the reproduction machine photoreceptor and the test plate.
As a further alternative, a source of calibrating potential is provided for use in calibrating the voltmeter through the test plate.

Description

~Ll)7C100~

This invention relates to electrostatic reproduction machines, and more particularly to an improved apparatus for controlling machine operating potentials and service equipment calibration.
As will be readily undPrstood by those familiar with copiers, the efficacy of electrostatic type copiers depends upon the proper relative charge being maintained between the photoconductive member and the developing means. For, as appreciated, this charge relationship or electrostatic develop-ment field is relied upon to attract the developing material,i.e. toner, from the supply source to the photoconductive member in conformance with both the outline and density of the electrostatic image on the photoconductive member. The electrostatic image which undergoes this development may be formed through the expediency of exposing the previously charged photoconductive member to a light image of the original being copied.
One method of sustaining the proper charge relation-ship between the photoconductive member and the developing means is to use an electrostatic voltmeter, commonly called an electrometer to sense potentials on the photoconductive member at some appropriate pointO This device can be used as a service instrument to provide, by meter, a visible indication of the photoreceptor charge condition from which the electrostatic development field can be manually adjusted. In other cases, a feedback loop may be provided to enable the electrometer to automatically control the development field. Control over the electrostatic development field may be done for example, by controlling or regulating the developer bias, or by con- -trolling potentials on the photoconductor itself by regulating the corona charging means.
-2-~l~7(~6 In machines of the type alluded to, adjustmerlt oE
one or more of the various operating parameters, such as the developer bias, normally requires that the bias be identified, and changes made -therein monitored. Failure to monitor the bias, and changes thereto, may result in biases exceeding safe or designed maximum levels with the consequent possibil.ity of damage to the machine and danger to personnel operating the machine.
Further, electrometers, like most test instxuments, require calibration checks from time to time to assure that the readings obtained are accurate. While numerous proce-dures exist in the prior art for calibrating such devices, many are-limited to off-site locations using relatively com-plex and expensive equipment.
In accordance with one aspect of this invention there is provided an apparatus for supporting the probe element of an electrometer in predetermined operative .relation-ship with a test surface adapted to bear a voltage potential for measurement by the electrometer, comprising: a box-like receptacle, one side of said receptacle being open; said test surface being rigidly supported in said receptacle opposite said receptacle one side whereby said test surface faces the receptacle opening; a complementary shaped frame siæed for insertion through said receptacle openiny and into said receptacle, said frame including means to fixedly .
support said probe element in facing relationship with said test plate, and means in said receptacle and cooperable with said frame to locate said probe in predetermined operative - relationship with said test plate on insertion of said frame into said receptacle.

_3.

This invention will be more apparent ~rom the ensuing drawings ln which:
Figure 1 is a schematic sectional view oE an electro-static reproduction machine incorporating the electrometer probe support of -the present invention;
Figure 2 is a side view of the magnetic brush devel-oping apparatus shown in Figure l;
Figure 3 is an elevational view of the opposite ' ~7~6 --side of the magnetic brush developing assembly illustrating the drive mechanism for the magnetic brush roller apparatus;
Figure 4 is a top plane view of the magnetic brush assembly showing details of -the brush bias applying mechanismi Figure 5 is an isometric view showing details of the probe support of the present inventlon, Figure 6 is a schematic view of an operating circuit for use with the probe support of the present invention, Figure 7 is an isometric view of an alternate probe support arrangement.
For a general understanding of the invention, an exemplary copier/reproduction machine in which the 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 produce 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 ~lexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 14.
.

The belt 12 comprises a photoconductive layer of selenium which is the light receiving surface and imagin~
- me~ium for the apparatus, on a conductive backing. The sur-face of the photocoductive belt is made photosensitive by :::

...... .... .. .. . . ... . . . . . .

a previous step of uniformly char~ing the same by means of a corona generating device or corotron 13.
The ~elt is journaled for continuous movement upon three rollers 20, 21 and 2~ positioned with their axes in parallel. The photoconductive belt assembly 14 is slidably mounted upon two support shafts 23 and 24, with the xoller ~ rotatably supported on the shaft 23 which is secured to the frame of the apparatus and is xotatably 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 Lmage of such original document posi-tioned on the plate~ is flashed on the surface of the b~lt to produce an electrostatic latent image thereon at exposure station 27.
As the belt surface continues its movement, the electrostatic image 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 thxough the development zone, as more fully hereinafter described~
The developed electrostatic image is transported by the belt to a transfer station 29 whereat a sheet of copy paper or transer member is moved between a transfer roller and the belt at a speed in synchronism with the moving belt in ord~r to accomplish transfer of the de~eloped image solely by an electrical bias on the transfer xoller. There is pro-vided at this station a sheet transport mechanism, generally indicated at 17, adapted to transport sheets of paper fxom a paper handlin~ m~chanism, generally indicated by the refer-.. ... .. . . ...... . . . .

~ ~)7( 1~6 ence numeral 18, to the developed image on the belt at thestation 29.
After the sheet is stripped fxom the belt 12, it is conveyed into a fuser assembly, generally indicated by the reference numeral 19, wherein the developed and trans-ferred xerographic powder image on the sheet material is permanently affixed th~ereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus~ The toner particles remaining as residue on the developed image, back-ground particles and those particles otherwise not transferred are carried by the belt 12 ~o a cleaning apparatus 26 positioned on the rim of the belt between rollers 20 and 2~ adjacent a charge device 25. Further details regarding the structure of the belt assembly 14 and ltS relationship with the machine and support there~or may be ~ound in U. S. Patent No. 3,730,623 ssued May 1, 1973 and assigned to the same assignee~
Referring to Figures 2 through 4, there is illus-trated a magnetic brush developing assembly, generally indicated as 30, comprising a series of rollers 36 rotatably supported in frame end plates 32, 34. The rollers 36 are each comprised of a cylindrical sleeve 46 of a roughened surface formed of a non-magnetizable material and extending almost the length of the hollslng of the dev~loping apparatus 30.
E~d slePves 48, formed of an insulating material, are shrunk fit on the cylindrical sleeve 46 adjacent the ends thereo.
One end of the sleeve 46 is closed by a cap 50 which supports a roller drive shaft 52 in coaxial alignment with the sleeve 46. The other end of the sleeve 46 is closed by a cap 54 having an orifice 56 through which extends shaft 58 of the - _7_ _ .___ _ __ . . _ . . . .. . . .. .. . . ..

internal bar magnets 61. Suitable bearing means 60 are provided to permit the sleeve 46 to rotate relative to shaft 58.
The rollex drive shafts 52 are suitably mounted in bearings in end plate 32 and carry on their projecting ends drive sprockets 96. Sprockets 96 are f~rmed of an insulating material.
Referring specifically to Figures 2 and 3, the magnet roller assembly 30 is disposed within a housing, gen ~rally indicated as 66, having a generally rectangular cross section and a length extending beyond the width of the photo-conductiva belt 12. Housing 66 is substantially closed except for an opening opposite photoconductive belt 12 whereat deveopment of the latent image on belt 12 is effected.
Housing 66 in effect serves as a container for developing material comprising carrier beads from magnetizable material and colored electrostatic toner particles which adhere thexeto.
To provide bias to magnetic brush rollers 36, a suitable wiper 70 is proYided in electrical contact with magnet shafts 58, wiper 70 extending along and being supported by side plate 34 to forrn an electrical path throu~h line 71 from an adjustable power supply 113 (seen in Figures 1 and 6) to each of the roller sleeves 46. Power supply 113 comprises any suitable source of electrical potential, herein designated in exemplary fashion as a battery. A suitable voltage output adjustment 114 is provided. While a d.c. power source is illus-trated, an a.c. or combination a.c./d.c~ may be used.

; ~
During development, the rollers 36 ar rotated in unison in the same direction from a suitable drive source via sprocXets 96, the internal bar magnets 61 remain station-.

Iry. The brush bristles produced by the influence of themagnetic field emanating from ~he bar magnets 61 acting upon the magnetizable carrier beads in the deve:Loping material will form on the upper region of the roller sleeves 46 adjacent the undersurface of the selenium belt 12.
This takes the form of a "magnet.ic blanket" extend-ing continuously from one brush roller 36 to another for the entire width of the development ~one 28 wherein the material is disposed or available to some degree for developing pUl--poses. Further details regarding the formation and erf~ct of the "magnetic blanket" are described in U. S. Patent No.
3,640,248, issued on February 8, 1972 and assigned to the same assignee~
As will be understood by those skilled in the art, develapment o the latent electrostatic image ~ormed on belt 12 is dependent upon the voltage differential between the light image and the developing means. This ~oltage differen-tial, 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. The strength and make-up of the xerographic develop-ment field may change with machine use and age.
To insure optimum machine performance, both initially and during the machine service life, adjustment or tuning of those machine processing components affecting the strength and make-up of the xerographic development field may be made. Such servicing may include adjusting of the power input to the corona generating device 13, re-settlng the bias output of power supply 113 to magnetic brush sleeves - ' .
_g _ :, - ' ' . ' ' : ' 46, resetting the bias on the developing electrode or electrodes in an electroded developing system, etc.
The above adjustments may be performed manually and are normally perormed by the machine technical or service representative may employ an electrostatic voltage measuring device, commonly termed an electrometer, and designated herein by the numeral 77. Electrometer 77 measures the voltage or potential of an electrostatic charge on the surface, for example, the charge on the surface of belt 12 by means of a non-contacting probe 78, probe 78 being positioned in pre-determined spaced Eelationship with the surface whose potential is to be measured for this purpose. Electrometer 77 may include a meter 77' to indicate ~isually the voltage being read. Alternately, an automatic control may be provided wherein the output of the probe 78 to electrometer 77, reflecting the voltage level of the area measured, i.e., belt 12 is used to adjust the power input or bias to one or more of the machine pro~ess components such as described above.
In servicing the reproduction machine 5 in the manner alluded to above, it is often desirable to know the voltage output of power supply 113 to the sleeves 46 of the magnetic brushes 36. To enable electrometer 77 to be used for this purpose, a voltage calibration box 80 illustrated in Figure 5, is provided. Referring now to Figure 5 box BO includes an open generally rectangular block-like receptacle 81 within which a probe support 90 is insertable as will appear. Receptacle 81 includes a base 82 with upstanding sides 83, 84. Cover 98 is hingedly attached to vne of the sides B49.
One side B4 of receptacle 81 is slotted at 85 to :

~10- ' _. .. .. _ _ ._ .. . _ .. .... . . . . . .. . . . . _ .. _ . . . ~

~7~

accommodate cord 79 of electrometer probe 78. The depth of receptacle 81 is such as to limit insertion of probe support gO therewithin throu~h engagement with base 82. In this way, the open side or face 78' of probe 78 is set in correct spacillg relationship with test plate 88 in receptacle 81 as will appear.
Test plate 88 comprises a generally rectangular metal piece, preferably brass, supported in fixed position on base.82 of receptacle 81. A test lead 89 projects from plate 88 through side 84' o~ receptacle 81, lead 89 being utilized to couple test plate 88 with the voltage source to be measured as for example r magnetic brush power supply 113.
Test lead 89 is electrically coupled to test plate 88 as by soldering.
Probe support 90 comprises a generally rectangularly shaped member having a central web portion 93 flanked on two sides thereof by vertical side walls 91, it being understood that the overall shap~ and dimension of probe support 90 is such as to permit the probe support to be snugly inserted within receptable 81 with the lower edge of walls 91 abutting against base 82 of receptacle 81.
Web 93 of probe support gO is provided with a circular receptacle 96 dimensioned to receive probe 78 of electrometer 77 therewithin. Suitable means, such as set screw 97, is provided to retain probe 78 in receptacle 96 and in preset spaced relationship with test plate 88 when probe support 90 is assembled with receptacle 81.
In use, probe 78 is secured within receptacle 96 of probe support 90u Support 90 is then inserted into receptacl~ 81 until walls 91 thereof contact base 82 of ~11---_ _ _ _ .. _. . _ ._ ... . . . . . . . ,. . . .. , ~_ receptacle 81. This locates face 78' of probe 78 in preset spaced relationship to test plate 88. Cover 98 may then be closed to retain the parts in assembled relat.ionship and provide a unitary calibration box 80.
Test lead 89 is connected to the bias source to be measured, as for example, power supply 113 for magnetic brushes 30. For this purpose, a suitable switching mechanism such as the switching mechanism 98 shown i.n Fiyure 6 may be provided to couple through switch contact 101 power source 113 to test plate 88~ The resulting potential appearing on test plate 88 is read by probe 7B, the voltage reading appearing on meter 77' of electrometer 77. As will be understood this reading indicates the voltage bias of power supply 113 to magnetic brush sleevçs 46 and serves as a reference when adjustments to the voltage supply are made.
It will be understood that bi~s to the reproduction machine component being measured, for example t magnetic brushes 36, may be interrupted during measurement. In that circu~-stance, an additional switch contact or switching mechanism ~not shown~ would be provided to interrupt the circuit from power supply 113 to brush sleeves 46 during measurement.
It is sometimes desirable to calibrate electrometer 77, to insure accuracy in the voltage readings provided. For this purpose, a source of known potential such as battery lno-is pxovidedO Battery 10~ is coupled to test plate 88 through lead 89 to provide a preset potential, and the ensuing reading of meter 77' o electrometer 77 compared with the kno~n potential of battery 100~ For this purpose, a second switch terminal of the aforedescribed switching mechanism such as terminal 103 of mechanism 98 may ~e set to couple bat-tery 100 with test plate 88.

' .

.. _ . . . . .. . .. .. . .

Switch terminal 103 is coupled to calibxation battery 100 by lead 104.
It will be understood that voltage calibration box 80 may be utili~ed to check other biases within the machine 5.
Referring now to Figures 1 and 5, reproduction machine 5 includes a fadeout lamp assembly 150 having lamp pair 151 disposed within reflector housing 152 between exposure stat.ion 27 and developer station 28. As understood by those skilled in the art, lamps 151 function to fadeout or erase unwanted margin edges of the latent electrostatic imaye on belt 12.
; Lamp assembly 150 is slidably supported by a plate 154 for movement of the-assembly into and out of operative position opposite belt 12. This construction permits the. -lamp assembly 150 to be removed for servicing and replacement.
Where it is desired to measure voltage condition on belt 12, lamp assembly 150 may be removed, and probe support 90 together with probe 78 mounted t~erewithin inserted onto plate 154. For this purpose, edges 102 of probe support 90 are turned in to enable the probe support 90 to be slidably disposed upon plate 154 thereby locating probe 78 in proper spaced relationship with belt 12 for accurate measurement o the potential thereof. For this purpose, the relative dimen-sions o plate 154 and probe support 90 are selected so as to provide the requisite mounting for support 90 yet permit slidable movement along plate 154.
In the embodiment shown in Flgures 6 and 7, where l.ike numerals refer to like parts, elestrometer probe 78 is supported in preset spaced relationship ~ith the photosensitive surface o~ belt 12 for slidable movement transversely back ~nd forth thereacross. For this purpose, a pair of slotted supports 125, are provided, supports 125 being suitably mounted on adjoining rame members (not showrl) o reprod~ction machine 5 so that slots 128 therewithin form a pair of parallel tracks a preset distance above the su.rface of belt 12. The longitudinal extent o~ supports :L25 ~nd slots 128, are such that a portion 126 of each support 1~5 and the slots 128 therewithin extend sufficientl~ to locate probe 78 over test plate i35 adjoining one side of belt 12.
Probe 78 is fixedly attached to a carriage 130, carriage 130 having a pair of oppositely extending arms 13~ extenaing in and slidable within slots 128. Suitable locking caps 133 may be provided on the terminal ends of arms 132 to prevent arms 132 from slipping out of slots 128 as carxiage 130, together with probe 78, is moved along slots 128.
A calibration/bias test plate 135 which is prefer-ably made of brass, is supported by legs 136 adjacent one side of belt 12 adjacent th~ extend~d portion 126 of supports 125. The dimension of the supporting legs 136 is such that test plate 135 is parallel to the path followed by electro-meter probe 78 and spaced a preset distance therebelow. To prevent short circuiting or dissipation of any bias applied to test plate 135, supporting legs 136 are comprised o a suitable electrical insulating material.
~ e~erring to Figures.6 and 7, the electrometer probe support there descxibed together with test plate 135 are preferably built-into the reproduction machine.5 to form a rel~tively permanent installation at a select.ed point along the photoreceptor belt 12~ One suitable location is between .

-1 ~ ' corona charging device 13 and exposure station 270 In use, probe 78 is electrically connected to electrometer 7~by co~-d 79, and readings oE the voltage potential on the photosensitive surface of belt 1~ are obtained.
Conveniently, by moving carriage 130 back and forth along slots 128, probe 78 can be made to scan the surface of belt 12 to provide readings across the entire width of belt 12 as desired.
Where it is desixed to take a reading of the voltage potential on test plate 135, as for example ~here checking and!or adjusting bias to sleeves 46 of mag brushes 3G, plate 135 is electrically connected to the voltage source, i.e., power supply 113, by switching mechanism g8 in the manner described heretofore. Carriage 130 together with probe 78 may be moved along slots 128, to a point opposite test plate 135 and the desired reading taken.
While the invention has been described with reference to the structure disclosed~ it is not confined to the details set ~orth, but is intended to cover such modifications or changes as may come within the scope of the following claims.

_ _ -- ---- r--

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for supporting the probe element of an electrometer in predetermined operative relationship with a test surface adapted to bear a voltage potential for measurement by the electrometer, comprising:
a box-like receptacle, one side of said receptacle being open;
said test surface being rigidly supported in said receptacle opposite said receptacle one side whereby said test surface faces the receptacle opening;
a complementary shaped frame sized for insertion through said receptacle opening and into said receptacle, said frame including means to fixedly support said probe element in facing relationship with said test plate, and means in said receptacle and cooperable with said frame to locate said probe in predetermined operative relationship with said test plate on insertion of said frame into said receptacle.
CA320,969A 1975-02-24 1979-02-06 Electrometer apparatus for reproduction machines Expired CA1070006A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA320,969A CA1070006A (en) 1975-02-24 1979-02-06 Electrometer apparatus for reproduction machines

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US05/552,019 US3998538A (en) 1975-02-24 1975-02-24 Electrometer apparatus for reproduction machines
CA242,994A CA1063175A (en) 1975-02-24 1976-01-06 Electrometer apparatus for reproduction machines
CA320,969A CA1070006A (en) 1975-02-24 1979-02-06 Electrometer apparatus for reproduction machines

Publications (1)

Publication Number Publication Date
CA1070006A true CA1070006A (en) 1980-01-15

Family

ID=27164266

Family Applications (1)

Application Number Title Priority Date Filing Date
CA320,969A Expired CA1070006A (en) 1975-02-24 1979-02-06 Electrometer apparatus for reproduction machines

Country Status (1)

Country Link
CA (1) CA1070006A (en)

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