Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACKGROUND AND SUMMARY OF I~VENTION
The present invention relates generally to the
photocopying of documents, and is illustrated as applied
to the copying of documents by electrostatic photography.
More particularly, the present invention is directed to an
improvement in the copying of duplex documents, and by the
term "duplex documents" is meant a document wherein infor-
mation is contained on both sides of the document sheet.
Further, the present invention contemplates the reproduction
of duplex documents as duplex copy, wherein both sides of
the copy sheet are utilized to reproduce the two sides of
the original duplex document.
The electrostatic photocopying process is well
known. In one common xerographic form of electrostatic
phot~copying, an optical image of a document to be copied
is applied to a uniformly charged photoconductive plate or
photoreceptor, causing the plate to discharge in those
areas which are struck by light. As a result, an electro-
static latent image of the document is formed on the photo-
receptor plate. This latent image may then be developed
to a visible image by the selective attraction of electro-
.
scopic toner particles to the charged areas of the latentimage. Usually, the toner particles of the developed image
are transferred from the photoreceptor to a receiving copy-
sheet so the photoreceptor can be re-used, and the transferred
toner particles may then be fused to the copy sheet to
form a permanent copy of the document.
Many documents carry information on both sides
of the document sheet. To copy both sides of such duplex
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documents in the conventional mode of copier operation,
first one side of the document is exposed to the copier
so that an optical image of the first side is applied to
the photoreceptor, then the document is turned over to ex-
pose the secona side to the copier. Typically, each side
of the document is reproduced on a separate copy sheet,
resulting in two sheets of copy for each single sheet of
duplex document.
In accordance with the present invention, a
duplex document is placed in a sandwich platen which is
: transparent on both sides, and then one side of the document
sheet is exposed to the copier through one side of the
platen, followed by exposure of the other side of the docu-
ment through the other side of the platen. Dual optical
paths are pro~ided, so that each side of the document can
be exposed to the copier automatically, and without the
necessity of turning the document over. In addition, it
is contemplated that the copy sheet will be processed
through the copier twice, being turned over between the
two traverses, so that an image of one side of the docu-
ment will be reproduced on one side of the copy sheet, and
an image of the other side of the document will be repro-
duced on the other side of the copy sheet, to provide a
duplex copy of the original duplex document.
The present invention thus provides a system for
projecting images of both surfaces of an original duplex object
in an object plane to an image plane and includes the means to
support the object to be projected in the object plane, first
optical means is provided for pro~ecting an image of the first
surface at the object plane along a first optical path to the
image plane and a second optical means is provided for pr~jecting
an image of the second surface of the object along a second
optical path to the image plane. Means are provided to orient
the im~ge of the first surface to ~ predetermined sense on the
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image plane and means to orient the image of the second surfa~eat the predetermined sense on the image plane~ The first and
second orientation means providing a resultant 180 change in
orientation of the first and second images at the image plane
relative to the first and second images at the object plane.
A method is also provided for duplex projection
: comprising placing an original duplex object in an object plane.
An image of the first surface of the original is projected along
a first path to an image plane and orienting the image between
the object and image planes to a predetermined sense on the image
plane. An image of the second surface of the original is
projected along a second path to the image plane and orienting
the image of the second surface between the object plane and the
image plane to the predetermined sense on the image plane. The
orientations to the predetermined sense provides a xesultant 180
change in orientation of the first and second images at the image
plane relative to the first and second images at the object
plane.
In another aspect the present invention provides
a method of producing duplex copies with first and second images
on opposite sides respectively of a copy sheet from a single
imaging surface memb~r comprising:
forming first and second transferable developed but
unfixed images on the same imaging surface;
transferring the first unfixed transferable image from
said imaging surface to one side of said copy sheet;
removing said copy sheet from said imaging surface,
and inverting it and returning it to said same imaging surface
without fixing said first ~mage thereto;
then transferring said second transferable unfixed
image directly to the opposite side of said copy sheet from said
~maging surface;
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B
then removing said copy sheet from said imaging surface
with said first and second unfixed images on opposite sides
thereof; and
feeding said copy sheet with said unfixed images on
opposite sides thereof through a fixing apparatus for fixing both
of said first and second images to said opposite sides of said
copy sheet. In accordance with one aspect of the invention said
first and second images are transferred u~fixed to opposite sides of
said copy sheet in immediate sequence, without any intervening
copy sheets having images transferred thereto between said images
of said first and second images. In another aspect a method is
provided wherein said sheet is electrostatically retained on a
transport member between said transfer of said first and second
images to said opposite sides thereof.
In one embodiment the present invention provides
a copying apparatus in which duplex copies are generated with
first and second images fixed to opposite sides thereof,
utilizing a single imaging surface member on which first and
second images are formed from an imaging station and then are
transferred directly to opposite sides of the same copy sheet
by transferring the first image to one side of the copy sheet
and removing the copy sheet from the imaging surface member and
turning it over and returning it to the same imaging surface
member, then transferring the second image to the opposite sid~
of the copy sheet from that imaging surface member, the
improvement comprising a copy sheet transport means for said
remo~ing and inverting and returning said copy to said imaging
surface member without fixing said first image to said copy
sheet and means for transferring said second unfixed image to
said second side of said copy sheet while said first image
remains unfixed and fixing means for subsequently fixing both of
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B
said unfixed first and second images to said opposite sides ofsaid copy sheet.
Other aspects and advantages of the present invention
will become apparent to those skilled in the art from a
consideration of the following detailed description of several
illustrative specific embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description of the invention
is given in conjunction with the accompanying drawings, in which
like reference characters refer to like or corresponding parts,
and wherein: -
Fig. 1 is a schematic illustration of a xerographic
photocopying machine showing dual optical paths for sequentially
exposing the top and bottom sides of an original duplex document;
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B
Figs 2A and 2G show, in sequence, how a duplex
document is sandwiched between a double-sided glass platen,
and how one side of the document is exposed as the platen
traverses in one direction and the other side of the docu-
ment is exposed as the platen traverses in the opposite
direction;
Figs. 3A and 3B are perspective views showing how
the top and bottom sides of the duplex document are re--
spectively projected onto the photoreceptor during the
two directions of traversé of the platen;
Fig. 4, on the page containing Fig. 1, shows one mode
of recirculating a copy sheet to obtain duplex copy of the duplex
document; and
Fig. 5, on the page containing Fig. 1, shows the dual
optical paths cooperating with two photoreceptors to produce
-duplex copy of a duplex document.
DETAILED DESCRIPTIO~ -
Fig. 1 schematically illustrates a duplex copying
machine embodying the present invention. Within the housing
11, a conventional xerographic electrostatic reproducing
apparatus is illustrated, comprising a rotating photo-
receptor drum 6 having the various operational stations
positioned around its periphery. At station A the photo-
conductive surface of the drum 6 is uniformly electro-
statically charged by means of a corotron. As the drum
rotates, the charged area is moved to station B where it
receives an optical exposure of the documen~ to be copied,
thereby forming an electrostatic latent image of the docu-
ment. At station C this latent image is developed by the
selective attraction of electroscopic toner particles to
the drum surface in accordance with the latent ima~e pattern.
~. .
Sheets of copy paper are fed from supply 20 along path 12
into contact with the drum 6 at station D, where the toner
image on the drum is transferred to the copy sheet, which
may be effected with the aid of a transfer corotron. The
copy sheet then continues along path 12 to a fusing rolls
13, 14 where the toner image is permanently fixed to the
copy sheet; and the copy sheet is then fed to a receivîng
bin 15. After toner transfer, the drum surface is cleaned
of residual toner particle at station E, as may be
accomplished for example by a rotating brush. The
photoreceptor drum surface leaving the cleaning station
E is ready to be recycled to receive another image.
The duplex photocopying feature of the invention
will be best understood by reference to Figs. 2A-2G in
conjunàtion with Fig. 1. The document platen utilized in
the practice of the invention is formed of two transparent
plates 2 and 3, which may be glass or transparent plastic.
These two plates are hinged at 16, and open in the manner
, .
shown in Fig. 2A to receive a duplex document sheet 1.
With a document 1 in position and the platen 2, 3 closed,
a cycle of operation can be iniated, starting from the
position shown in Fig. 2B.
With the upper exposure lamp 4 illuminated, a
rack and pinion drive 17, 18 causes the platen to traverse
to the right as viewed in Figs. 1 and 2. Simultaneously,
drum 6 is rotated clockwise in synchronism with the traverse
of the platen. Light from lamp 4 is reflected from the
upper surface of document 1, and is then directed by mirror
7 through a focusing lens system 8, and reflected by mirror
9 to the surface of drum 6 at station B. As the platen 2,
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3 continues its traverse to the right as depicted in Figs.
2s-2D, a continuous incremental image of the upper surface
of document 1 is focused on the surface of rotating drum 6,
as is well understood in the art. At the completion of
the traverse of the platen 2, 3 to the right, a complete
image of the upper surface of document 1 is formed on the
drum 6, and on continuing operation of the machine, that
image will be developed at station C and then transferred
to a copy sheet at station D.
Upon completion of the platen traverse to the
right, a limit switch (not shown) is actuated, which turns
off upper exposure lamp 4, turns on lower exposure lamp 5,
and reverses the rack and pinion drive 17, 18 causing the
platen 2, 3 to traverse to the left as viewed in Figs. 1
and 2. Under these circumstances, the lower side of docu-
ment 1 is illuminated, and light reflected therefrom is
directed by mirror 10 through the focusing lens system 8,
and by mirror 9 to the surface of photoreceptor 6 at
station B. As the platen 2,3 traverses to the left
through the stages illustrated in Figs. 2E-~G, an image
of the under side of document 1 is focused on the photo-
receptor drum 6, and like the image from the upper surface
of document 1, this image is also developed at station C
and transferred to a copy sheet at station D.
Figs. 3A and 3B depict the optical representations
of the images obtained from the document sheet 1. Fig. 3A
does this for the upper surface of document 1 moving to the
right, using the optical path of mirror 7, lens 8, and mirror
g.
As clearly shown from this comparative representation
the optical projection system provides a manner of reorienting
images present on opposite sides of a duplex original such that
they are provided at the image plane, in this case the photo-
receptor, in an orientation or sense that may be predetermined.
A particular advantage is the ability to reorient images such
that they are provided at the image plane in the same orientation
or sense. This feature has particular significance in the
reproduction of manuscript and some pictorial representations
in duplex form in that it provides a simple manner of reproducing
the images of the original in simplex form with the images reading
in the same direction or in duplex form with images in the
original orientation.
Illumination and exposure of the duplex original may be
achieved with well known techniques such as full frame exposure,
including flash techniques, as well as scanning. A particular
advantage of a scanning technique is illustrated in Figures 3A
and 3B wherein the manuscript material on both sides of the duplex
original is scanned in the same sense or in the reading direction
from edge to edge providing successive images which are in the
same sense or reading direction. The advantage is achieved in
manuscript reproduction if the scanning is from edge to edge of
the original in the reading direction. With most duplex
originals such as pages from a report or the like the intelligence
on one side reads from left to right and the intelligence on
the other side without reorienting the original and reading from
underneath reads from right to left~ Thus a positive scan of the
one side of the original parallel to the reading direction and a
reverse scan of the opposite side of the original parallel to the
reading direction combine to produce images having the same
orientation or sense. In contrast, sranning of the original
from top to bottom produces a satisfactory image on one side but
the reverse scan on the opposite side of the original would
provide a distorted image having, for example, an incorrect
line sequence corresponding to an order of from bottom to top
of the original.
A further advantage of the system is the ability to
use common elements in the optical paths for the projections
from both surfaces of the duplex original. Thus Figures 3A
and 3B represent this in simple form by using a single reflecting
surface to reflect the image from the top of the duplex original
and a single reflecting surface to reflect the image from the
bottom of the duplex original and thereby obtain comparative
images in an image plane which are in a predetermined sense or
180 different in orientation relative to their orientation in
the object plane. Thereafter, common optical elements such as
lenses and reflectors may be common to the two optical paths if
desired.
In the foregoing embodiment of the invention, the
duplex original document is copied from both sides as a result
of one cycle of scan of the platen 2, 3 utilizing dual optical
paths. However, as depicted, the copy is simplex, i.e., each
side of the document is reproduced on a separate copy sheet.
It is apparent that by recirculating the copy sheet and turning
it over after receiving the image of the first side of the original
document, the second side of the document can be reproduced
on the second side of the CoFy sheet. Such a mechanism is
schematically illustrated in Fig. 4, for making multiple
duplex copies of a duplex document. The dual optical
scanning paths of Figs. 1 and 2 are utilized for Fig. 4,
but are omitted from this figure for simplifications.
As shown in Fig. 4, the photoreceptor drum 6 is
divided into three image fields, and the document e~posure
is keyed thereto and alternates between the document top
side (image A) and the document bottom side (image B).
Copy sheets are fed from sheet feeder 20 to endless belt
31, in synchronism with the document exposure cycle and
the positions of the image fields on drum 6. After each
sheet receives its first side image from drum 6, it is
retained on belt 31 by aid of tacking corotron 19 and
recycles back toward the feeder 20 on the lower course
of the belt, where it is received on lifter 32, raised
thereby to the vacuum conveyor 33 of the sheet feeder,
and returned to the upper course of the belt 31. In this
process, it will be appreciated that the sheet has been
turned over. It is now returned to the drum 6 to receive
its second side image, after which it is removed from the
conveyor belt 31 and fed by rolls 21 through a toner fuser
22, and thence to the copy receiving bin 15 shown in Fig. 1.
Obviously, the length of conveyor 31 and the operation of
sheet feeder 20 must be appropriately related to each
other, and synchronized with the cycling rate of the
document plagen 2, 3 and the drum 6 to effect proper
registration of each copy sheet side with the proper
document image and image field on drum 6.
An illustrative timing chart for a copy sheet
feed operation of three sheets per cycle of the drum 6
is presented in the following table.
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N ~ ~ ~ ~O
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o~ E-~ ~q ,g
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E~
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An alternative manner of producing duplex copies
from a duplex document is shown in Fig. 5. Again, the
system uses the same dual optical paths as described for
Fig. 1 for scanning the duplex original 1 in the sand-
wich platen 2,3. In this instance, a semi-transparent
mirror 23 reflects the image onto photoreceptor drum 6,
as in the preceding embodiments. In addition, the image
transmitted by mirror 23 is reflected by mirror 24 to a
second photoreceptor drum 25. Each of the drums 6 and 25
is provided with charging, developing, transfer, and
cleaning stations, although they are not shown in this
figure to simplify the presentation. Thus, with each
cycle of traverse of platen 2, 3, latent images of one
side and then of the other side of document l are formed
on both drums 6 and 25, and these latent images are
developed and transferred to receiving sheets. As
schematically illustrated, a copy sheet is fed from a
sheet feeder to bring one side into image transfer
relation with drum 25. When the copy sheet leaves drum
25, it is turned and re-fed with the opposite side in image
transfer relation with drum 6. A proper timing relation-
ship between sheet feed, rotation of the photoreceptor
drums, and the scan traverse of platen 2, 3, produces a
duplex copy of the duplex document 1.
For example, upon completion of scan of side A
of the document, a copy sheet from the feeder can reach
the image transfer station of drum 25 to pick up image A.
This copy sheet i~ then turned and re-fed to drum 6 as the
scan of side B of the document is completed, to pick up the
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B image from drum 6 at its transfer station. While the
first copy sheet is picking up image B from drum 6, a
second copy sheet can be picking up image B from drum 25.
As the system continues to cycle, the second copy sheet
will be turned and re-fed to drum 6 in time to pick up
image A, while a third copy sheet is fed to pick up image A
from drum 25.
Accordingly, it will be appreciated that a copying
system is provided for the efficient reproduction of duplex
document sheets, wherein both sides of the document are
scanned in sequence during one cycle of the document platen.
In addition, the copy sheet can provide a duplex reproduction
of the document, either by turning and recirculating the
copy sheet, or by utilizing two photoreceptors and feeding
the copy sheet to receive from one photoreceptor the image
from one size of the document on one side of the copy sheet,
and from the other photoreceptor the image from the other
side of the document on the other side of the copy sheet.
While the operation of applicant's device has been
described for use with a document having printing or image
material on both sides of a single document, it should be
understood that the term document embraces not only a single
sheet of support material having image material on both sides
but also two (2) sheets of support material each having images
on only one side which are thereafter placed in back-to-back
relationship to provide, in effect, a double-sided document.
It is understood that the specific embodiments shown
and described are presented only as illustrative of the invention.
Various modifications will be apparent to those skilled in the
art, and such modifications as are embraced by the spirit and
scope of the appended claims are contemplated as being within
the purview of the present invention.
