U.S. patent number 3,793,016 [Application Number 05/298,980] was granted by the patent office on 1974-02-19 for electrophotographic sheet binding process.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Roger Hamilton Eichorn.
United States Patent |
3,793,016 |
Eichorn |
February 19, 1974 |
ELECTROPHOTOGRAPHIC SHEET BINDING PROCESS
Abstract
Sheet binding where the printing medium itself is the sheet
binder. In a xerographic process, high density areas of xerographic
toner are provided at desired binding areas. Sufficiently high
density toner areas are provided by inserting a finely apertured
optical mask adapted to provide edge development effects to
maximize overall toner density over the selected binding area, yet
which is compatible with solid area coverage machines. These toner
binding areas may then be subsequently re-fused between adjacent
overlaying sheets to provide bound stacks, without requiring any
additional binding material.
Inventors: |
Eichorn; Roger Hamilton
(Webster, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
23152832 |
Appl.
No.: |
05/298,980 |
Filed: |
October 19, 1972 |
Current U.S.
Class: |
430/124.1;
430/121.1; 156/151; 156/291; 281/21.1; 402/79; 412/900; 118/638;
281/2; 281/38; 412/33; 399/183 |
Current CPC
Class: |
B42C
9/0093 (20130101); Y10S 412/90 (20130101); G03G
2215/00835 (20130101) |
Current International
Class: |
B42C
9/00 (20060101); G03g 013/00 (); G03g 013/08 () |
Field of
Search: |
;96/1R,15D ;117/17.5
;118/637 ;161/147 ;281/21R ;156/291,151 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Brown; J. Travis
Assistant Examiner: Miller; John R.
Claims
What is claimed is:
1. In an electrophotographic process wherein an indicia bearing
original is optically imagable onto a charged photoreceptor surface
to form an electrostatic image of said indicia thereon, and wherein
this electrostatic indicia image is edge developable by attracting
an electrostatically attractable and fusible electrophotographic
toner to the edges of said electrostatic image, which attracted
toner is then fusible onto the desired copy sheet; the improvement
comprising the steps of:
optically forming an intense electrostatic charge image over at
least one selected minor area of said photoreceptor by applying a
multiplicity of small closely spaced alternating high contrast
light and dark images to said photoreceptor over said minor area of
said photoreceptor;
attracting an overall high density of the same said fusible
electrophotographic toner to said selected minor area by edge
development of said alternating closely spaced light and dark
images;
fusing said high density toner area to said copy sheets at at least
one selected minor binding area of said sheets;
assembling two or more of said copy sheets in a stacked
relationship; and
while said sheets are so assembled, re-fusing said toner between
said adjacent sheets only at said binding areas sufficiently to
achieve inter-sheet binding by commonly fusing said toner between
adjacent sheets only at said binding areas.
2. The process of claim 1 wherein said light and dark images are
consistently spaced apart by a distance corresponding to the
effective edge development distance of said photoreceptor.
3. The process of claim 2 wherein said light and dark images are a
band of closely spaced lines and said binding area is the image of
said band extended along at least one edge of said sheets.
4. The process of claim 1 wherein said light and dark images are
applied by inserting a finely multiply apertured optical mask
between said indicia bearing original and said photoreceptor.
5. The process of claim 1 wherein said mask is inserted by
inserting a transparent overlay bearing said mask.
6. The process of claim 4 wherein said optical mask is inserted by
inserting said original into a transparent folder bearing said
optical mask and positioning said original in said folder so that
no indicia or said original is masked by said optical mask.
7. The process of claim 3 wherein said lines are applied spaced
apart by approximately 0.05 millimeters and are between
approximately 0.05 to 3.2 millimeters in width, and wherein said
band is greater than approximately 6.35 millimeters in width.
Description
The present invention relates to a very simple and economical
method of binding two or more indicia bearing sheets together by
providing on the sheets additional minor high density areas of the
same indicia imparting material in areas of desired binding, where
the sheets are subsequently stacked and the additional indicia
imparting material commonly fused between adjacent sheets at the
binding areas to fasten the sheets together.
Sheet binding is one of the oldest known arts, and numerous methods
and apparatus are known in the art for permanently or temporarily
securing sheets together. Many of these, of course, are only
economically suited for high priced or high volume commercial
printing operations. There is a long standing need for improved
sheet fastening means for localized, simple, and inexpensive
binding of, for example, stacks of 2 to 50 pages.
This need has been greatly increased by the widespread use of
xerographic equipment, where large numbers of printed sheets are
produced by relatively unskilled personnel in non-commercial
printing operations. The demand for simplicity and economy in these
applications has continued to retain conventional metal staples as
the primary fastening means. This is in spite of the fact that
stapling, riveting or other sheet binding means requiring
penetration of the sheet creates stress points in the sheets which
encourage sheet tearing and inadvertent sheet removal. So does any
sharp edges on the staples or rivets. Further, the pull-off
strength of the top and bottom sheets in any stack fastened in this
conventional manner is liminted by the strength of the sheet over
only the small areas directly underlying the heads of the staple or
rivet.
Thus, it is clear that a sheet binding method which provides
inter-sheet adhension over a much larger binding area than staples
or rivets, and which does not require any sheet penetration or
sharp edges, is greatly preferable. Various adhesive bonding
methods have been developed which have suitable binding strengths
but they have not achieved widespread utilization in many low
volume binding applications, apparently because they are not
sufficiently simple and economical in comparison to metal staples
or rivets. They require the supplying, handling and containment of
separate adhensive materials, and require separate adhesive
application steps in addition to the normal indicia printing steps.
Examples from the adhesive binding are shown in U.S. Pat. Nos.
2,579,488; 2,831,706; 2,898,973; 3,026,228 and 3,502,532. Some of
these utilize chemicals similar to those found in xerographic
toners, but they are not toners or inks. Other examples of adhesive
sheet welding with heat and/or pressure, by pre-coating the sheet
with clear plastics or other separate binding materials, are
discussed in the September, 1971 issue of "Book Production
Industry", PP. 53-55, which discusses U.S. Pat. No. 3,560,290.
It has been known that in certain situations xerographic toners
become tacky, softened or liquified. U.S. Pat. Nos. 2,638,416;
2,788,288; 2,917,460; 3,053,688; 3,262,806; 3,268,332 and 3,488,189
are examples of patents noting these toner characteristics. These
characteristics are conventionally utilized for fixing the desired
indicia onto individual sheets. Or they may be used for
transferring images from one web to another, as in "strip out"
imaging processes, e.g., U.S. Pat. No. 3,275,436. However, printing
inks and toners are carefully selected and prepared to avoid and
prevent any inter copy sheet adhension as soon as possible after
the copy sheet printing is accomplished, because this would
seriously interfere with normal printing operations and is
considered highly disadvantageous in the art. Thus, toners or
printing inks are not considered in the art as adhesives, and, in
fact, inter-sheet adhesive properties are carefully avoided by ink
or toner formulators.
In spite of, and contary to the teachings of the art, it has been
found that a secure inter-sheet binding may be achieved utilizing
only the conventional and commercially available printing indicia
itself as the sole sheet binding agent, rather than adhesives or
other separate bindings. Fusible xerographic toners have been found
to be particularly suitable. By the term "fusible", (as used herein
in connection with the indicia imparting material, such as
xerographic toner) is meant a material which in its normal ambient
state is non-adhesive (non-tacky), but is rendered sufficiently
tacky for sheet adherence temporarily by heat or solvent vapors or
pressure or some combination thereof. The desired toner material
here is one that is refusible, i.e., easily rendered adhesive at
least a second time, at any time after its initial fusing. Some
examples of fusible and refusible xerographic toner compositions
are disclosed in U.S. Pat. Nos. 3,609,082; 3,577,345; 3,590,000 and
Re. 25,126. Suitable refusible xerographic toners are commercially
available world-wide from the Xerox Corporation and its
subsidiaries, and are already present in their existing xerographic
machines.
A co-pending application Ser. No. 283,676 having the same title and
assignee, by Gordon P. Taillie, filed Aug. 25, 1972, included a
disclosure of details of the present invention, which was not
claimed therein since it is the separate invention of the present
applicant. This application is directed to a sheet binding process
which is particularly suited for electrophotographic apparatus
which does not inherently provide good solid area toner coverage,
and therefore cannot readily provide a sufficiently high density of
toner over a sufficiently wide binding area for good bonding.
The method of sheet binding disclosed herein overcomes the
structural disadvantages of metal rivets and other penetrating
bindings discussed above. It provides strong and sheet
tear-resistant bindings having a larger binding area. The method of
the invention enables the use of existing electrophotographic toner
supply, dispensing, imaging and fusing apparatus without requiring
any modifications. The only additional step required for the
present process is a simple and non-critical re-fusing operation
which can be performed at any time in conjunction with, or
subsequent to, the indicia printing operation, and in any location.
This re-fusing may be accomplished by various inexpensive and
simple or commercially available apparatus, as described
hereinbelow. Thus, it may be seen that the present process is
particularly suitable for local sheet binding in offices or other
existing xerographic machine locations.
The exemplary embodiment described hereinbelow discloses the
incorporation of the process of the invention in an otherwise
conventional exemplary xerographic process and apparatus.
Accordingly, said processes and apparatus need not be described in
detail herein, since various printed publications and patents and
publicly used machines are available which teach details of various
suitable exemplary electrophotographic and xerographic structures,
materials and functions to those skilled in the art. Some examples
are disclosed in the books Electrophotography by R. M. Schaffert,
and Xerography and Related Processes by John H. Dessauer and Harold
E. Clark, both first published in 1965 by Focal Press Ltd., London,
England, and the numerous patents and other references cited in
these books. All of these references are hereby incorporated by
reference in the specification. Also incorporated by reference
herein are the above-cited references from the adhesive binding
art, for their showings of various sheet assembling, clamping and
heating apparatus which may be utilized in the final steps of the
present process. Accordingly, the present specification is specific
to those details of the embodiment which represent a departure from
the prior art, and further desired detailed description will be
provided by the above references.
Further objects, features and advantages of the present invention
pertain to the particular steps and details whereby the
above-mentioned aspects of the invention are attained. Accordingly,
the invention will be better understood by reference to the
following description and to the drawings forming a part thereof,
which are substantially to scale, wherein:
FIG. 1 is a perspective view of a document of bound sheets in
accordance with the present invention;
FIG. 2 is a magnified cross-sectional partial view of the binding
area taken along the line 2--2 of FIG. 1.
FIG. 3 is a perspective view of a transparent overlay with an
optical mask, retaining an original as shown, for producing binding
areas in xerographic copies of the original in accordance with the
present invention;
FIG. 4 is a cross-sectional simplified plan view of an otherwise
conventional xerographic machine showing several modifications
which can be provided thereon for producing the process of the
invention;
FIG. 5 is an enlarged top view of an optical mask which may be
utilized in the apparatus of FIG. 4;
FIG. 6 is a perspective view of an exemplary re-fusing apparatus
for the process of the invention, shown with an exemplary stack of
sheets inserted therein; and
FIG. 7 is a simplified top view of the principal operating
components within the apparatus of FIG. 6.
Referring to the drawings, there is shown in FIGS. 3-7 some
examples of apparatus for performing the sheet binding processes of
the invention. It will be appreciated that various steps of the
process can also be performed manually or by other apparatus,
including that disclosed in the previously cited references.
FIGS. 1 and 2 show one example of a completed article of
manufacture in accordance with the present invention. Specifically
there is shown a securely edge bound stack 10 of individual paper
sheets 12. The sheets 12 are bound only at a binding area 14. This
binding area 14 extends in a stripe along, or closely adjacent to,
the entire left hand edge of all of the sheets 12 in the stack 10.
The binding areas are preferably located at the same position on
each of the sheets 12, so that with the sheets 12 aligned overlying
one another, the binding areas 14 are also so aligned. Each binding
area 14 is substantially continuously covered and occupied by a
corresponding high density area 16 of fusible xerographic toner 18.
Preferably each sheet 12 has at least one such high density area
16. The toner 18 of this high density area 16 is the same toner 18
as provides the indicia 20 on the sheets 12, and it is preferably
provided in the same step and at the same time as the imaging of
the indicia 20.
As may be seen particularly from the magnified cross-sectional view
of FIG. 2, the inter-sheet binding consists solely of the high
density areas 16 of toner 18 being commonly fused between
immediately adjacent sheets 12 at the binding area 14. It may be
seen that the toner 18, which was initially prefused into the
binding areas of the individual sheets 12, is additionally refused
into the sheet immediately above or below it. The toner is refused
into all of the sheet surfaces in the case of conventional porous
paper, as shown, to form a strong interlocking bond.
The strength of the inter-sheet bond is a function of the area,
density, and degree of fusing of the xerographic toner between
adjacent sheets. By increasing these parameters the inter-sheet
bond can be made substantially stronger than the tear resistance of
the sheet material itself. Correspondingly however, by reducing one
or more of these parameters in the binding process there can be
provided an inter-sheet bond which is sufficient to normally retain
the sheets together, but yet which allows removal of individual
sheets without sheet tearing. I.e., a pad type of binding can be
provided wherein one or more sheets can be pulled off the stack
neatly, with the separation occuring at the respective inter-sheet
toner bond.
It will also be noted that the stack 10 may be additionally bound
by conventional staples, rivets or other mechanical fastening
means, as shown by exemplary staple 22 in FIG. 1. If done in the
binding areas, this provides a binding which is far stronger than
such conventional mechanical binding means can provide in
themselves. This is because when such mechanical fasteners
penetrate the sheets in the stack only within the fused binding
areas, they are not limited by their normal stress concentrations
and small area sheet strength limitations. The stack area around
the area of fastener penetration is bonded together and reinforced
by the re-fused toner and strongly resists sheet tearing as a unit.
These advantages similarly apply if apertures through the sheets
are desired at the binding areas for ring binding or the like. It
will be appreciated that combinations with mechanical fastenings
means are not required and that the present process can provide
sufficient binding strength to be the sole binding means for
permanent binding.
The binding area 14 of FIGS. 1 and 2 is a contiguous single edge
binding area. However, it will be appreciated that the binding area
may be in only one corner of the sheets, for example, or there may
be several separate binding areas rather than a single one.
Referring to FIG. 4, there is shown therein by way of example, one
type of conventional xerographic apparatus. The process of the
invention may be performed thereon utilizing this apparatus in its
conventional mode of operation. Thus, an indicia bearing original
24 here is conventionally optically imaged onto a charged
photoreceptor surface 26 to form an electrostatic image of said
indicia thereon. This electrostatic indicia image is conventionally
developed by attracting an electrostatically attractable and
fusible xerographic toner 18 to said electrostatic image, which
attracted toner 18 is then fused onto the desired copy sheets 12.
(As is well known, in certain other types of xerographic processes
using photosensitive treated paper, the charged photoreceptor is
integral the copy sheet.) The fusing of all of the toner 18 onto
the copy sheet is accomplished by a conventional fusing operation
30 in the xerographic apparatus. The completed image copy sheets 12
are then deposited at the output in a catch tray 32 or other
suitable sheet receptor which provides assembly of the copy sheets
in an overlying stacked uniform relationship.
Considering now FIGS. 3-5, there are illustrated thereon examples
of differences in otherwise conventional xerographic sheet
processing which enable the sheet binding process of the invention
to be accomplished. FIG. 3 illustrates an optical mask 34 which
functions as an overlay to the indicia bearing original during
imaging in the apparatus of FIG. 4, or other xerographic apparatus.
The optical mask 34 is provided by an opaque area 36 on an
otherwise fully transparent clear plastic jacket 38 into which the
original 24 is simply inserted. This jacket does not obstruct
indicia imaging of the original, unlike the "half tone" jackets in
use for breaking up indicia areas for xerographic reproduction. The
opaque area 36 corresponds in proportion, size, location and area
to the desired binding area 14 on the copy sheet. (With a one to
one reduction it will be identical.) I.e., the optical mask 34 is
dimensioned so as to provide a high density binding area 16 of
toner on the copy sheet of the dimensions previously discussed.
The opaque area 36 is located on the side of the jacket 38 which is
between the original and the photoreceptor, i.e., in the optical
path therebetween, and outside of the indicia area. Thus, in the
xerographic imaging process there is thereby formed an intense
additional electrostatic charge image on the minor area of the
photoreceptor which corresponds to the desired binding area on the
copy sheet. The mask provides in itself a very high contrast
multiplicity of closely spaced alternating light and dark images to
the photoreceptor. This additional image is in addition to the
electrostatic indicia image, and is formed at the same time and by
the same apparatus. Accordingly, in the same operation in which
toner 18 is attracted to the electrostatic indicia image, the high
density area 16 of toner is attracted to the additional minor image
area and additionally imparted to the copy sheet at the binding
area 14. This additional toner area is fused along with the indicia
in the conventional fusing operation 30.
FIGS. 4 and 5 illustrate a different type of optical masking
operation to achieve the same result of forming the high density
area 16 of toner at the binding area 14. This optical mask 40 is
shown in an enlarged top view in FIG. 5, and in position in a side
view in FIG. 4. The exemplary mask 40 is a plate reciprocally
movable in and out of the optical path between the original 24 and
the photoreceptor at one edge thereof. When so inserted, it
functions in the same manner as described above for the optical
mask 34. It may be inserted manually or by an automatic apparatus
such as the electrical solenoid 42 shown.
It has been found by the present inventor that both the optical
masks 34 and 40, should be finely optically apertured if good toner
binding is to be achieved in the many xerographic machines that do
not provide solid area development. That is, the optical masks are
preferably made up of a multiplicity of small opaque areas
separated by small transparent spaces in between. For a desired
binding area 14 in the form of a stripe or band as illustrated, the
optical mask is preferably made up of a multiplicity of closely
spaced opaque lines. Preferably these lines are approximately 0.05
to 3.2 millimeters (0.002 to 1/8 inch) wide and are spaced apart by
approximately 0.05 millimeters (0.002 to 0.003 inches or slightly
greater), whereas the entire band is preferably wider than
approximately 6.35 millimeters (1/4 inch). This band width can
provide good binding with the process herein even in xerographic
machines with edge development and poor solid area toner coverage.
In a machine providing good solid area development a solid toner
band as narrow as 3.2 millimeters (1/8 inch) can provide a
sufficient binding area.
The use of an apertured optical mask as taught here takes advantage
of, and utilizes for the purpose of the invention, the phenomenon
of "edge development" in electrophotography. This phenomenon per se
is well discussed in the previously cited text references and
accordingly need not be discussed herein. The result of a mask of
this apertured configuration with edge development is a much higner
toner concentration over what would otherwise be the hollow (low
toner) interior of solid areas. Thus, a much higher overall toner
density, and much better bond, is provided in the desired binding
areas than would be provided by a solid area mask. Closely spaced
dots in these dimensions and spacings rather than lines may also be
used for the same purpose, although lines are preferred.
An alternative method by which the desired optical mask may be
provided in the path between the original and the photoreceptor is
to simply preprint a finely apertured dark area on the original. As
a further alternative, the copy sheets themselves may be preprinted
with sufficient toner in the desired binding areas. These methods
of course require an additional step unless preprinting is required
for other reasons.
Considering next the exemplary ways in which the high density
binding areas 14 of toner 18 on the individual sheets 12 are bound
together to form an integral stack 10, as previously described the
sheets are assembled together in a directly overlying relationship
in a position in which they are to be bound. It is not essential
that all of the binding areas directly overlie one another although
this is preferable. At the catch tray 32 of FIG. 4 there is
provided an exemplary pair of pressure platens or dies 46 and 48
located at the lower end of the catch tray where one edge of the
sheets commonly abuts a stack stop. They comprise here one fixed
heated platen 46 and one movable heated platen 48, located
respectively at opposite sides of the stack 10. The platens 46 and
48 provide re-fusing for binding between adjacent sheets by heating
the stack at the binding area 14 sufficient to render the high
toner density area 16 on the sheets (only at the binding areas)
sufficiently tacky to adhere between adjacent sheets, while
simultaneously pressing the binding areas 14 together under
pressure between the platens 46 and 48. The platen 48 is moved with
pressure down against the top of the stack. This pressure is
sufficient to remove air spaces between the sheets at the binding
areas, and to provide good inter-sheet toner transfer, including
improving the flow of toner from its carrier sheet into the
adjacent sheet surface. The heating is continued until the toner on
at least one sheet is softened sufficiently to adhere to the next
adjacent sheet for each of the number of sheets being bound.
Preferably, the stack 10 is further held between the dies for a
time period after the heating is terminated sufficiently to allow
the toner to substantially re-solidify by cooling.
The platens 46 and 48 are shown here with schematic representations
of conventional electrical heating coils in the platen surface to
provide the re-fusing heat. However, it will be appreciated that
numerous other fusing means and processes may be utilized including
those described in the above-cited references.
While, as described above, all of the sheets to be bound in a
single stack may be first assembled together and bound
simultaneously in a single binding re-fusing step, other variations
are possible. For example the re-fusing process may be repeated for
each individual sheet to be bound. One way this may be accomplished
is for the binding area of the uppermost sheet in the stack to be
radiant heated to maintain the toner therein sufficiently adhesive,
the next sheet for the stack to be individually placed on the stack
with a binding area contacting the stack, and this single
additional sheet to be bound to the stack by downward movement of
the platen in synchronism with the addition of the sheet. By
repeating this step for each additional sheet, as many additional
sheets as are desired may be bound to the same stack without
requiring heating of the entire stack. Correspondingly, or in
combination, individual sheets may be added and bound to the stack
one at a time by rendering or maintaining the toner area on the
added sheet sufficiently tacky during the time that it is added to
the stack and clamped by the platen thereon. A thermal shield 50
extending from the fusing operation 30 down over the catch tray 32
is illustrated here by way of an example for effecting the latter
step by maintaining the toner area 16 warm and tacky from the
original fusing operation 30 for the brief time needed to place it
over the stack and press it down thereon.
FIGS. 6 and 7 illustrate the exterior and interior details
respectively of a further exemplary apparatus 52 for performing the
final re-fusing step for binding described above. As may be seen
from FIG. 6, the apparatus 52 is designed to accept the stack 10 of
sheets 12 vertically downwardly therein and to align the lower
edges thereof for binding as a single bound stack. As may be seen
from FIG. 7 this may be accomplished by a relatively simple
apparatus 52 comprising a stationary platen 54 operated against by
an opposing moving platen 56. The moving platen 56 is driven under
pressure to compress together the binding areas 14 of the stack 10
by a rotatably driven cam 58. The cam 58 causes a cam follower 59
to reciprocate, and it in turn moves the moving platen 56 through
coil compression springs 60. The springs 60 restrict the amount of
force which can be applied to the moving platen 56, and thereby
prevent jamming of the machine. However, an increased thickness of
the stack 10 will cause greater compression of the springs 60 and
therefore a desired greater compression force to be applied to the
stack. Electrical heating elements as shown may also be provided
here to heat the platens. Additional heating means can also be
provided in the bottom surface against which the stack abuts.
The above described apparatus 52 is for the purpose of providing
the application of both heat and pressure for stack binding. It
will be appreciated that depending on the type of xerographic toner
selected, that pressure alone may be sufficient, or that vapor or
other known fusing methods may be provided. It will also be
appreciated that numerous other apparatus may be utilized, such as
pressure dies in the form of continuous rollers, etc. Further,
pressure can be, but need not necessarily be, applied before,
while, or after the toner is heated.
Any type of original image indicia may be utilized with the present
process, whether hard copy, microfilm, microfiche, graphic, or
alpha numeric, since the binding process does not interfere in any
way with normal indicia imaging or printing except at the selected
binding areas. Likewise, almost any copy paper may be utilized. For
example, the present process may be utilized to provide bound
demand-printed paper copies of microfilm reports, texts or the
like. It is especially suitable for direct on-line binding of
pre-collated output sets from high speed machines.
For microfilm or other reversal image input, it will be appreciated
that an opaque image mask will not be suitable. In this case the
additional image area for toner binding can be provided by
additional light sources imaged through apertures corresponding to
the above-described masks.
It will also be noted that either one or both of the immediately
adjacent (overlying) binding areas may have the pre-fused toner
binder areas thereon. If both adjacent surfaces have high density
toner areas 16, this will give an even stronger bond since more
binding toner 18 is available in the inter-sheet space, and also
since deeper toner penetration of both sheets may have been
provided in the original fusing in this manner.
It will also be noted that in situations where there is not an
esthetic problem, that it is possible with the pressent process to
print or indicia a number of additional unused binding areas in
addition to the binding area which may eventually be utilized. In
fact, by printing binding areas on all copies produced whether
intending them to be bound or not, subsequent binding together of
any of the sheets may be readily accomplished at any time by
completion of only the re-fusing step of the above-disclosed
process. The black binding areas which would be exposed on the
unbound copies would not be objectionable in many situations, since
they would occupy only a small area of the sheet margin outside of
the normal indicia-occupying area. Thus, for convenience, it is
also possible to completely mask both edges of the original so as
to provide a substantial toner area along both edges of the copy
sheets. Only the one edge which is clamped and subjected to
re-fusing will be a binding area. There is no binding effect by
these further high density areas of toner, since if they are not
re-fused in the re-fusing step, they will not bind the sheets
together.
Providing binding areas at both sheet edges may be particularly
desirable in the case of duplex or pseudo-duplex copying where the
desired binding areas may be at alternating sides of the respective
sheets. In pseudo-duplex output format, where two sheet folds of
material are bound together at every other fold line to provide the
individual duplex pages, it may be desirable to place the binding
areas on both sides of both edges of each sheet.
In situations where the esthetic factor of exposed black toner
areas is a problem, it will be noted that all the binding areas
which are bound are not visible except for binding areas exposed on
the upper or lowermost sheets of the stack. These can be eliminated
simply by ensuring that the upper and lowermost sheets to be bound
only have binding areas facing the stack.
Several stacks 10 can be simultaneously bound by a modification of
the process herein. A large common assemblage of all the sheets for
several stacks can be formed, interspersed with one or more sheets
having no adjacent inter-sheet binding area thereon. These
interspersed sheets are located between the desired individual
bound stacks. The entire assemblage can then be subjected to the
toner re-fusing step. The interspersing sheets will prevent
inter-sheet binding to themselves, but not interfere with the
binding together of all of the other sheets with toner binding
areas. Thus, in a single binding operation, several bound stacks
can be simultaneously produced without adhering to one another.
Note that these interspersed non-binding sheets can be provided by
the last sheet of one stack and the first sheet of the next stack
having no binding areas on their outward facing surfaces, which is
also desirable esthetically. This elimination of binding areas on
selected sheet surfaces can be provided automatically, for example,
by programmed actuation of the solenoid 42 to remove the imaging
light mask 40 for preselected sheets.
Note that the term "sheet" as used in the specification and claims
herein is defined (conventionally) as including both individual cut
sheets and also sheet segments of continuous web or fan fold or
accordian fold paper or the like, whether burst or unburst. The
subject method is applicable to those machines in which the paper
is roll fed and is cut or folded into its individual sheets only
after the toner has been applied and first fused into the binding
areas.
In conclusion, it may be seen that there has been disclosed herein
a novel and improved sheet binding method, and a bound stack
produced therefrom, having numerous advantages in both simplicity,
economy, and fastening security. The exemplary embodiments
described herein are presently considered to be preferred; however,
it is contemplated that further variations and modifications with
the purview of those skilled in the art can be made herein. The
following claims are intended to cover all such variations and
modifications as fall within the true spirit and scope of the
invention.
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