Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~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.
- 15-
_ _ -- ---- r--
