Note: Descriptions are shown in the official language in which they were submitted.
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This is a divisional of application Serial Number
178,886 filed August 15, 1~73,
In an electrostatic cop~ing machine of the type
using a photoconductive layer for developing a latent
electrostatic image of the document to ~e copied and
thereafter developing and transferring the image to a
copy sheet, various processing stations are utilized for
uniformly charging, exposing and developing the photo-
sensitive surface, transferring the developed image to a
copy sheet, fusing the transferred image on the copy
sheet, cleaning the photoreceptive surface, etc. Provision
must also be made for the efficient and accurate movement
of sheets of copy paper from the supply station to the
transfer station of the machine.
With the increasing amount of paper work that
must be accomplished in various industries ;`n recent years,
commercial automatic copier/reproduction mach~nes have
been developed to provide extremely high speed copying
of original documents. As machine speeds increase, the
damage or jams that could occur in a machine in the event
of a malfunction also increases. To minimize the possi-
bility of damage, a number of sensors are employed in the
machine to monitor the various machine functions and the
paper position throughout its path in the mach~ne. In
the event of a malfunction~ the sensors, acting through
the machine control system, will cause the machine to shut
down.
In a high speed xerographic copier of t~e t~pe
employing a photoreceptor belt, a number of images ma~
be disposed on the belt before the sheet of paper adapted
to receive the foremost image is fed from the paper supply
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station. In the event of a malfunction of the paper feeder, ~-
these electrostatic images would ~roceed through the deve- -
loper and the transfer rollers to the cleaning station
of the machine wherein the belt is ordinarily cleanea ~-
prior to the charging thereof and exposure of a new image.
If the paper is not present at the transfer station when
the developed image arrives thereat, the xerographic
surface with the toner image thereon can cause numerous
problems. Toner may be transferred from the belt to the
transfer rollers. The toner that is not transferred to
the transfer roll will be conveyed by movement o the belt
to the cleaning station of the machine. Since the cleaning
station is designed to remove the residual toner remaining
after the majority of the toner is transferred to the
' 15 copy sheet, in the évent that a copy sheet is not present
at the transfer rolIs, excess quantities of toner will
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reach the cleaning station, putting an undue load thereon. :
Besides the problems presented at the transfer station
and the cleaning station, this type of operation is ex-
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; 20 tre~ely wasteful of xerographic toner.
SUMMARY OF THE INVENTION
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This invention relates to a method for minimizing
problems in a xerographic machine caused by the misfeed
of copy paper therethrough by discharging the electrostatic
image on the photoconductive surface before that portion
of the surface reaches the developer station, de-energizing -
o the developer, and removing the electrical bias on the
transfer rolls to prevent transfer of toner the~eto and
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, 30 m~nimize the possibility of carrying excess toner to the
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cleaning station of the machine.
Thus, in accordance with the present teachings,
a method is provided for automatically producing copies of
an original which comprises the steps of providing an electro-
static charge pattern of the original on a photoconductive
~ur-fa~e, developing the charge pattern with an electrically
attractable powder as the charge pattern on the photoconductive
surface passes a developer station to provide a powder image
on the photoconductive surface in conformity with the original.
Sheets of copy paper are supplied to the photoconductive surface
in synchronism with the developed image thereon for contact
with the image to transfer the powder image to the copy paper
and in the event of a paper misfeed development of the charge
pattern is prevented as the photoconductive surface moves past
the developer station discharging at least a portion of the
areas of the charge pattern on the photoconductive surface.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic sectional view of a
reproduction machine showing the various processing stations -
therein; and
Figure 2 is a schematic block diagram of the control
system to provide a programmed shutdown of the machine in the
event of a paper misfeed.
DESCRIPTION OF THE PREFERRED EMBODIMENT
I .
; For a general understanding of an electrostatic
; processing system in which the invention may be incorporated,
reference is had to Figure 1 in which various components of a
system are schematically illustrated. As in most electro-
static systems such as a xerographic machine, a light image
of the original to be reproduced is projected onto the
sensitized surface of a xerographic plate to form an
electrostatic latent image thereon. Thereafter, the latent ;
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image is developed with an oppositely charged developing
mate~-ial comprising carrier beads and smaller powder particles
*riboelectrically adhering thereto to form a xerographic
powd_r image corresponding to the latent image on the
plate surface. The powder image is then electrostatically
transferred to a support surface to which it may be fixed by a
fusing device whereby the powder image is caused permanently
to adhere to the support surface.
The electrostatically attractable developing :
material commonly used in electrostatic reproduction systems - ~
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comprises a pigmented resinous powder hereinafter referred
to as "toner", and "carrier" of larger granular beads
formed from a material removed in-the triboelectric series
from the toner so that a triboelectric c~arge is generated
~5 - between the toner powder and the granular carrier. The
-carrier also provides mechanical control so that the toner
can be readily handled and brought into contact with the
exposed xerographic surface where the toner is attracted
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to the electrostatic latent image from the carrier to pro- -~
duce a visible powder image on the xerographic surface.
In the illustrated machine, an-original D to -
be copied is placed upon a transparent support platen P, -
fixedly arranged in an illumination assem~ly generally
` indicated by the reference numeral 10. While upon the
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platen, an illumination system L comprising two or more
i lamps and reflectors is flash energized to direct light
rays upon the original to produce image rays corresponding
to-the-informational areas---on-the-original.~-The-image
~!~ rays are projected by means of an optical system ll to
jl 20 an exposure station A for exposing the photosensitive
b' . ', surface of a moving xerographic plate in the form o~ a
3 flexible photoconductive belt 12. In moving in the direc- ;
~ tion indicated by the arrow, prior to reaching the exposure
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station A, that portion of the belt being exposed would
have been uniformly charged by a corona device 13 indi-
cated at a belt run extending between belt supporting
rollers 14 and 15, the latter being the drive roller
.. . . . . . . . . ; for the belt. The exposure station extends between the
roller 14 and a third support roller 16. The belt run
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~ 30 between these rollers is encompassed entirely by the
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exposure station for minimizing the space required by
the belt and its supporting rollers.
The exposure of the belt to the light image
discharges the photoconductive layer in the areas struck
by light whereby there remains on the belt a~latent elec-
trostatic image in image configuration corresponding
to the light image projected from the original document.
A discharge device, preferably a flourescent lamp 17
; is provided adjacent support roller 16 for reasons to
be explained hereinafter.
As the belt surface continues its movement,
the electrostatic image passes around the roliér 16 to
a developer station B located at a third run Qf the belt
in which there is positioned developing apparatus generally
indicated by the reference numeral 18. The developer
apparatus 18 comprises a plurality of brushes adapted
for rotation by a suitable motor 19 to carry developer
' along the adjacent-surface of the upwardly moving inclined ;~
; photoconductive belt 12 to provide development of the
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electrostatic image.
The developed electrostatic image is transported
` by the belt 12 to a transfer statian C located at a point
o~ tangency on the belt around the drive roller lS whereat
a sheet of copy paper is moved at a speed in synchronism
~ 25 With the moving belt in order to accomplish transfer of
'- a properly registered developed image. A transfer rolller
20 is provided at transfer station C for contacting the
upper surface of the copy paper to assure good contact
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petween the copy paper and the belt 12 during transfer
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of the toner image from the belt to the paper. An electrical
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bias may De provided on roller 20 to attract the toner
from belt 12 to the copy paper.
There is also provided a copy sheet supplying ~
apparatus comprising a main paper feed supply 21 and ~ '
' an auxiliary paper feed supply 22. Each of the paper c~
supplies is adapted to separate sheets from their res-
pective supply stacks and to transport the sheets to a '
sheet registration station and eventually into contact -
with the developed image on the belt as the same is ' ;
carried around the drive roller 15. Control means 23
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- are operatively associated with each of the paper supply -`
mecha,nisms 21, 22 and the flash illumination device L, ~'~
for pxoducing an electrostatic latent image on the belt
12 to present a developed image at the transfer station', '
C in timed sequence with the arr}val of a sheet of paper,
and is coordinated with the activation of othex processing
' ,and c~ntrol devices at the precise time that these elements ' '
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, are~ to function for their intended purpose. A paper
sensing device 24 is positioned adjacent the paper path
between the paper supply mechanism 21 and 22 and the
, transfer stat,ion C, to determine if the paper is fed there-
from at the proper time relative to the image on,the
', photoreceptor belt. ' ' ,
'i After the developed image is transferred to ,
', 25 a sheet of paper,'it is stripped from the belt 12 and
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3 conveyed by conveying system 25 into a fuser apparatus
generally indicated by reference numeral 26 wherein the , ~ ,,
developed and transferred xerographic powder image on ', '
the sheet material is affixed thereto. After fusing, the '
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finished copy is discharged from the apparatus by a conveyor
27 at a suitable point for collection externally of the
apparatus. The toner particles remaining as residue on
the developed image and those particles not otherwise
' transferre~ are carried by the belt 12 to a cleaning
apparatus 28 positioned on the run of the belt between
the rollers 14 and 15 adjacent the charging device 13. ~'
; The cleaning apparatus comprises a discharge device 29
for neutralizing charges remaining on the particles and a '
rotating brush 30 which operates in conjunction with a ~
vacuum system to remove the residual toner particles ' "~
from the brush. - '~ '
As stated heretofore, in a high speed copier
of the type illustrated, a number of images may have been '
fl'ashed on the belt by the time ~he'sheet of paper is
fed for transfer of the foremost image thereto. In the
event~of a malfunction in the paper feed mechanism which
' would be sensed by the sensor 24, a number of operations
are immediately instituted to avoid deleterious effects
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'~ 20 on the machine caused by developed images reaching the
transfer station in the absence of copy paper thereat.
Therefore, upon the sensing of a paper misfeed by sensor
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,` 24 t~e control system 23 is adapted to immeidately energize
' lamp 17,deactivate the developer motor 19 r remove the
electrical bias on transfer roller 20 and move the transfer
~ roller out of contact with the belt by a suitable mechanism
'` ~not shown).
~ hus in theevent of a paper misfeed, the elec- '
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trostatic image on the belt passing beneath lamp 17 will ~ -'
be discharged, those'~mages that are passed the lamp when
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the misfeed is detected and have not reached the developer
will not be developed and those images that are developed
when the misfeed is detected will not be transferred to
the transfer roll since the electrical bias thereon is
removed and the roll is withdrawn from the belt. There-
fore the cleaning station will only be required to remove
toner from one or two developed images rather than all
the images that were on the belt prior to the detection
of the misfeed.
While we have described the preferred embodi-
ment of our invention it is to be understood that the
invention is not limited thereto but may be otherwise
embodied within the scope of the following claims.
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