Field of the Invention
The present invention relates to a method for decreasing the volume
of paper after it has been through an image transferring process.
Background of the Invention
Books and other bound paper items are a substantial part of many businesses,
homes and institutions of learning. These printed materials are generally formed
of multiple sheets or layers of paper. Although each sheet may not have a great
individual thickness, the cumulative total of these pages requires significant linear
Many facilities for retaining these publications have a fixed storage
volume. Thus, many materials are either sent off site or destroyed. The destruction
of materials presents numerous negative implications. However, even off site storage
requires cataloging transport and maintenance of the materials, thereby adding to
the overall cost.
While publishers of books and other bound paper items recognize the
shelf space problem, the publishers are limited to the thickness of paper they can
employ. Most printing devices require the paper to have a minimum thickness, resistance
to curl and other parameters that permit rapid processing of the paper. Therefore,
the paper must have a certain thickness to print and the resulting publication has
a corresponding thickness. This results in increased shelf space requirements of
the publications. In addition, binding costs go up when the volume of material to
be bound goes up.
One solution to this problem is to use thinner paper. However, thinner
paper often jams in copiers and other image transfer machines.
In the 1970s, the Xerox Corporation introduced a paper known as micro-spheres
that was made up of paper or plastic miniature spheres for the purpose of reducing
the overall weight of the paper for reduction in mailing costs. This paper had the
normal thickness of copier paper and worked well in copiers and printers without
jamming, and further had the benefit of reduced mailing costs by virtue of its light
weight. This paper is no longer used or manufactured today, but the technology exists
for making it.
Therefore, the need exists for a method of forming an imaged paper,
wherein the imaged paper has a reduced thickness.
EP-A-0343794 discloses a method and an apparatus for producing printed
matter having a high degree of gloss, rub-resistance, water-resistance and resistance
to contamination. Web-fed printed matter or a web-fed printing paper is coated with
a coating agent for roll press working and subjected to hot roll press working while
in the state of a web
U.S. Patent No. 3,933,547 discloses a method of forming a thermoplastic
resin article having a pattern durably described on a surface thereof which comprises
impressing a pattern with inks or colors on the surface of a thermoplsatic resin
article, said surface having a fine interconnected open-cell structure and heating
under pressure the pattern-bearing surface to a temperature above the melting point
of said thermoplastic resin so as to cover the pattern-bearing surface with a thin
film layer of resin formed from the original surface layer resin of the article.
Summary of the Invention
The present invention relates to methods of increasing the density
and decreasing the thickness of a collapsible paper substrate after it acquires
an image, as defined in the accompanying claims. The image may be acquired by any
of a variety of mechanisms such as a printer. The imaged substrate is then subjected
to a sufficient compressive force to decrease the thickness of the substrate without
altering the image.
Brief Description of the Drawings
Detailed Description of the Preferred Embodiment
- Figure 1 is a schematic view of an apparatus for reducing the thickness of a
- Figure 2 a schematic view of an alternative apparatus for reducing the thickness
of a substrate cross-sectional view of a sheet of collapsible paper.
- Figure 3 is a cross sectional view of a substrate with an image forming material
in an imaging state.
- Figure 4 is a cross sectional view of the substrate of Figure 3 in a compressed
- Figure 5 is a cross sectional view of an alternative substrate with an image
forming material in an imaging state.
- Figure 6 is a cross sectional view of the substrate of Figure 5 in a compressed
Referring to Figure 1, the present invention may operate in conjunction
with a printer 10 and be located downstream of the printer. That is, the printer
10 forms an image on a substrate 20 and the substrate then passes to the present
The substrate 20 has a given thickness for processing such as imaging.
The substrate 20 may have any of a variety of widths and lengths depending upon
the intended use and the imaging processing. That is, some imaging of the substrate
20 employs a continuous web, while other imaging processes on a sheet by sheet basis.
As shown in Figures 3-6, the substrate 20 has an imaging state 20'
and a compressed state 20". In the imaging state 20' the substrate has a first thickness
and in the compressed state 20" the substrate has a second lesser thickness. The
substrate 20 may be transformed from the imaging state to the compressed state by
the application of a compressive force. The transformation of the substrate 20 from
the imaging state 20' to the compressed state 20" is a one way process without secondary
processing. That is, upon the substrate 20 being rendered to the compressed state
20", the substrate does not substantially migrate or creep back towards the thickness
of the imaging state. The thickness in the compressed state 20" is between 30 percent
to 90 percent of the thickness in the imaging state 20', with a desired thickness
of less than 70 percent of the imaging thickness. However, it is understood the
thickness in the compressed state may be 30 percent or less, than the thickness
of the substrate in the imaging state.
Preferably, the substrate 20 has a threshold compression pressure
sufficient to permit the desired imaging of the substrate without reducing its volume
or transforming the substrate to the compressed state. That is, in the imaging state
20' the substrate has structural and performance characteristics and parameters
sufficient to permit imaging through simplex or duplex operations including copiers,
printers, facsimiles or the like. The structural characteristics of the substrate
20 in the imaging state are selected to permit the substrate to be used interchangeably
with traditional substrates, such as paper.
Preferably, the substrate 20 can be compressed without changing the
image. That is, the substrate 20 does not significantly distort, warp, or curl upon
compression, and hence any image on the substrate is not degraded.
The substrate 20 may be formed of a variety of constructions such
as a multiplicity of collapsible voids 21. The voids 21 may be formed by microstructures
embedded in the substrate 20, as well as voids in the material of the substrate
itself. The voids 21 may be formed by dispersing a multiplicity of micro capsules
or spheres throughout the substrate 20 when the substrate is manufactured. Thus
deformable embedded structures are located throughout the substrate 20. The deformable
structures are selected such that upon application of the compressive force, the
structures are sufficiently ruptured or collapsed to substantially preclude un aided
return to the imaging configuration. Alternatively, the substrate 20 may include
spacings sandwiched between layers. Other possible methods of constructing such
substrates as laminates having a micro-thin layer of Styrofoam (or other highly
compressible material) between two very thin layers of paper. The laminate has a
sufficiently high tensile strength in the imaging state to permit use in imaging
processes, yet yields to the compressive force to substantially reduce the thickness
without distorting or degrading the image. A further construction of the substrate
20 contemplates the inclusion of a multiplicity of fibrous or puffy particles. Alternatively,
the substrate 20 may include a corrugated layer that is irreversibly compacted upon
exposure to the compressing force. However, any such compressible, collapsible paper
will work well with this method.
The manufacture of such a paper substrate is known technology. Specifically,
U.S. Pat. No. 3,293,114 issued Dec. 20, 1966 discloses papers useful in packaging,
printing, preparation of containers and the like wherein hollow expanded spherical
particles are incorporated into the paper pulp by admixture with the wet pulp prior
to deposition on the screen. These papers demonstrate increase stiffness and increase
U.S. Pat. No. 3,556,934 represents a method of making papers similar
to that described in U.S. Pat. No. 3,293,114, mentioned above, with the exception
that this patent teaches the incorporation of the microspheres in an unexpanded
state to the aqueous suspension and during the drying of the paper subjecting it
to temperatures sufficient to cause the particles to expand within the paper sheet.
U.S. Pat. No. 3,779,951 issued Dec. 18, 1973 relates to an improved
method for the expansion of expandable microspheres in the presence of water.
U.S. Pat. No. 3,941,634 issued Mar. 2, 1976 discloses a method for
the preparation of paper containing plastic particles by forming two-spaced apart
dewatered webs of cellulose fibers introducing expandable thermoplastic beads between
the dewatered webs pressing the spaced apart partially dewatered webs together and
subjecting this product to heat to at least partially dry the fibers and at least
expand a portion of the beads.
U.S. Pat. No. 4,133,688 issued Jan. 9, 1979 discloses a photographic
paper coated with a polyolefin on both sides wherein in the preparation of the paper,
either non-inflated microspheres which are subsequently inflated during the drying
of the paper or inflated microspheres are added to the pulp during preparation of
U.S. Pat. No. 4,268,615 issued May 19, 1981 relates to a method of
producing a relief by forming a layer of a pattern on the surface of a sheet made
of a material having the property of increasing in volume when heated, the pattern
being made of the material having a stronger ability to absorb light than the aforesaid
material, and then radiating a strong light uniformly on the entire surface of the
sheet to selectively heat the portion of the sheet adjacent the undersurface of
the pattern layer whereby the pattern layer is raised from the sheet surface. The
sheet is prepared by mixing microcapsules and a binder such as vinyl acetate polymers.
The image may be formed on the substrate 20 by any of a variety of
mechanisms including, but not limited to xerographic transfer, ink jet, laser, facsimile,
offset printing. It is understood the image may be formed on either, or both sides
of the substrate 20.
The compressive force may be applied by any of a variety of compressing
mechanisms, including but not limited to rollers, calendaring, and presses. The
compressive force acts to compress the substrate 20 so that the thickness of the
substrate is reduced. In addition, it is believed under certain conditions that
the compressive force urges the particles forming the image into the substrate 20.
Thus, the image particles may not project as far from the substrate 20 in the compressed
state as in the imaging state.
The entire surface of the substrate is exposed to the compressive
force. The compressive force may be simultaneously applied to the entire surface
area or sequentially applied to sections of the substrate 20 to encompass the entire
area of the substrate.
In the roller configuration, a single roller may be employed to apply
the pressure. Alternatively, a pair of opposing rollers 32, 34 may be used. The
hardness and surface finish of the roller is at least partially determined by the
anticipated processing volume, the substrate 20, the image and the desired finish
to the substrate. The compressed substrates 20' may be compressed to exhibit a glossy,
smooth, shiny, antiqued or matte finish. It is anticipated that at least some processing
will seek to achieve a resulting finish that closely matches the imaged and uncompressed
If rollers are used in the compressing process, fuser oil or toner
residue may build up on these rollers. If so, a rubber squeegee, blade or knife
may be used to remove or reduce accumulated oil or toner.
In the stacked substrate 20 configuration, a press plate acts over
the surface area of the substrate. Although the press plate may have a variety of
configurations for applying the compressive force such a piston, cam or a roller
acting on a back of the press plate. A vacuum support plate may be used in cooperation
with the press plate to assist in compressing those substrates having trapped or
The sheet of collapsible paper is sent through a printer such as a
copier or other imaging system. The page (substrate) is imaged on one or both sides.
The page is then moved towards a compaction system 30 that may be connected to or
integral with the imaging system 10 or it may be a separate element (Figure 1).
The compaction system then applies the compressive force to the major planes of
the substrate (page). A simple manner of accomplishing compaction is to run the
sheet of paper between two rollers or between a roller and a relatively hard surface.
The substrate in the compressed state then moves to an output device or to be used.
The compressing mechanism 30 may be cooperatively engaged with current
high speed printers having a bypass transport. The bypass transport distributes
the printed sheets (substrates) 30 directly out of the printer into secondary processing
equipment. Thus, the compressing mechanism 30 would be operably located as the secondary
Alternatively, the compressing mechanism 30 can be readily attached
to the printer 10 and apply the necessary compressive force to reduce the paper
thickness to the desired dimension as an intermediate step between the printer and
subsequent secondary processing equipment.
Alternatively the pages of the substrate 20 can be loaded into a press
that applies a predetermined amount of pressure on the pages resulting in compaction
of the pages and the toner surface. The compressed pages may then be removed from
the press. The loading and unloading may be done by hand, or it may be done through
automated means. For example, in the case of a printer with a bypass transport,
the press may be a simple bin where imaged pages are collected and then pressed
before being extracted and sent on to the secondary processing equipment.
Thus, the compressing mechanism exerts the compressing force over
the entire surface area of the substrate 20. In contrast to devices which may locally
compact a section of a substrate, such as a seal, the present invention applies
the compressive force over the entire area of the substrate 20.
In cooperation with the compressing mechanism 30, a heating mechanism
40 can be employed to assist in the reduction of the substrate thickness. The heating
mechanism 40 may be any of a variety of configurations including radiant, convective
or conductive heat. In one configuration, the compressing roller 32 or 34 may include
a resistive heater such that the surface of the roller transfers heat tot he substrate
being compressed. Alternatively, a separate heating roller may be employed upstream
of the compressing roller. It is contemplated that radiative heaters, such as heat
lamps, could be used to heat the substrate prior to exerting the compressive force.
The substrate 20 may thus be heated above an ambient temperature, and if necessary
to a higher temperature that is below a degradation temperature of the substrate.
In a reference example, as shown in Figures 3 and 4, a Xerox 4024
Bond paper was used as the substrate. the thickness of the substrate and image forming
toner on two side of the substrate was 112 µm (0.0044 inches). This substrate 20
has an imaging thickness of 102 µm (0.004 inches). Upon the application of the compressing
force between 71 to 285 kg per linear cm (400 to 1600 pound per linear inch), the
substrate had a thickness of 94 µm (0.0037 inches) in the compressed state. The
combined thickness of the substrate and the image forming toner on two sides of
the substrate in the compressed state was 104 µm (0.0041 inches). Thus, the resulting
imaged substrate has a thickness of approximately 93 percent of original thickness
paper. Thus, even substrates that do not include compressible or collapsible microstructures,
can be compressed by over 5 percent.
In a further example, as shown in Figures 5 and 6, the substrate 20
was formed with collapsible micro capsules. The imaged substrate in the imaged state
had a thickness of 102 µm (0.004 inches) with a combined substrate and image forming
toner on two sides of the substrate thickness of 112 µm (0.0044 inches). After a
compressive force of between 2760 to 11,000 kPa (400 to 1600 pound per square inch),
the substrate in the compressed state retained a thickness of 66 µm (0.0026 inches)
with a with a combined substrate and image forming toner on two sides of the substrate
thickness of 7 µm (0.0028 inches). Thus, the substrate 20 in the compressed state
had a thickness that was 65 percent of the original thickness. That is, the substrate
20 had been compressed by 35 percent.