U.S. patent application number 14/190125 was filed with the patent office on 2015-08-27 for media guiding system using bernoulli force roller.
The applicant listed for this patent is David James Cornell, Christopher M. Muir. Invention is credited to David James Cornell, Christopher M. Muir.
Application Number | 20150239690 14/190125 |
Document ID | / |
Family ID | 52395177 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150239690 |
Kind Code |
A1 |
Muir; Christopher M. ; et
al. |
August 27, 2015 |
MEDIA GUIDING SYSTEM USING BERNOULLI FORCE ROLLER
Abstract
A media-guiding system includes a media-guiding roller having a
roller axis and an exterior surface having one or more grooves
formed around the exterior surface. A media travels along a
transport path past the media-guiding roller with a first side of
the media facing the exterior surface of the web-guiding roller. An
air source provides an air flow into one or more of the grooves,
the air flow being directed between the first side of the media and
the exterior surface of the media-guiding roller thereby producing
a Bernoulli force to draw the media toward the exterior surface of
the media-guiding roller and providing an increased traction
between the media and the media-guiding roller.
Inventors: |
Muir; Christopher M.;
(Rochester, NY) ; Cornell; David James;
(Scottsville, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Muir; Christopher M.
Cornell; David James |
Rochester
Scottsville |
NY
NY |
US
US |
|
|
Family ID: |
52395177 |
Appl. No.: |
14/190125 |
Filed: |
February 26, 2014 |
Current U.S.
Class: |
271/3.19 ;
271/3.22 |
Current CPC
Class: |
B65H 29/245 20130101;
B65H 2301/4461 20130101; B65H 23/0212 20130101; B65H 2406/113
20130101; B65H 5/26 20130101; B65H 2404/152 20130101; B65H 20/14
20130101; B65H 2406/111 20130101; B65H 2801/03 20130101; B65H
2406/1132 20130101; B65H 2406/11 20130101; B65H 5/22 20130101; B65H
5/06 20130101; B65H 27/00 20130101; B65H 3/0638 20130101; B65H
3/0692 20130101; B65H 9/166 20130101; B65H 3/14 20130101; B65H
5/066 20130101; B65H 2406/36 20130101; B65H 5/228 20130101; B65H
23/0251 20130101; B65H 2406/12 20130101; B65H 23/24 20130101; B65H
2404/13161 20130101 |
International
Class: |
B65H 3/06 20060101
B65H003/06; B65H 5/26 20060101 B65H005/26; B65H 5/22 20060101
B65H005/22; B65H 3/14 20060101 B65H003/14; B65H 5/06 20060101
B65H005/06 |
Claims
1. A media-guiding system for guiding a media travelling from
upstream to downstream along a transport path in an in-track
direction, the media having a first side and an opposing second
side, comprising: a media-guiding roller having a roller axis and
an exterior surface having one or more grooves formed around the
exterior surface, wherein the media travels along the transport
path past the media-guiding roller with the first side of the media
facing the exterior surface of the media-guiding roller; an air
source for providing an air flow into one or more of the grooves,
the air flow being directed between the first side of the media and
the exterior surface of the media-guiding roller thereby producing
a Bernoulli force to draw the media toward the exterior surface of
the media-guiding roller and providing an increased traction
between the media and the media-guiding roller; and a roller
control mechanism for adjusting an orientation of the roller axis
relative to the in-track direction of the media, thereby providing
a steering force to steer the media in a cross-track direction.
2. The media-guiding system of claim 1 further including a control
system for selectively activating the air source, wherein when the
air source is activated the Bernoulli force draws the media toward
the exterior surface of the media-guiding roller providing a higher
traction between the media and the media-guiding roller, and when
the air source is not activated no Bernoulli force is produced
providing a lower traction between the media and the media-guiding
roller.
3. The media-guiding system of claim 2 wherein the roller axis is
oriented in a non-orthogonal direction relative to the in-track
direction such that when the air source is activated the media is
steered in a cross-track direction as it passes the media-guiding
roller.
4. The media-guiding system of claim 3 further including a media
edge detector that detects a position of an edge of the media, and
wherein the control system controls the air source in response to a
signal from the media edge detector.
5. The media-guiding system of claim 1 further including an edge
stop positioned along one edge of the media, wherein the roller
axis is oriented to provide a steering force that pushes the media
against the edge stop thereby maintaining a substantially constant
cross-track position of the media.
6. The media-guiding system of claim 11 wherein the roller axis is
substantially perpendicular to the in-track direction.
7. (canceled)
8. The media-guiding system of claim 1 further including a media
edge detector that detects a position of an edge of the media, and
wherein the roller control mechanism adjusts the orientation of the
roller axis in response to a signal from the media edge
detector.
9. The media-guiding system of claim 1 wherein the media guiding
roller is mounted to a frame, and wherein the roller control
mechanism includes an actuator or a stepper motor that adjusts the
orientation of the roller axis by rotating the frame around a
rotation axis.
10. The media-guiding system of claim 1 wherein the media contacts
the media-guiding roller for a wrap angle of less than 5 degrees as
it passes the media-guiding roller.
11. A media-guiding system for guiding a media travelling from
upstream to downstream along a transport path in an in-track
direction, the media having a first side and an opposing second
side, comprising: a media-guiding roller having a roller axis and
an exterior surface having one or more grooves formed around the
exterior surface, wherein the media travels along the transport
path past the media-guiding roller with the first side of the media
facing the exterior surface of the media-guiding roller; an air
source for providing an air flow into one or more of the grooves,
the air flow being directed between the first side of the media and
the exterior surface of the media-guiding roller thereby producing
a Bernoulli force to draw the media toward the exterior surface of
the media-guiding roller and providing an increased traction
between the media and the media-guiding roller; and an air shoe in
proximity to the media-guiding roller, wherein the media passes
over the air shoe on a cushion of air, and wherein the
media-guiding roller stabilizes a cross-track position of the media
as the media passes over the air shoe.
12. The media-guiding system of claim 1 wherein the media is a web
of media.
13. The media-guiding system of claim 1 wherein the media is a cut
sheet of media.
14. The media-guiding system of claim 1 wherein the media-guiding
roller spans a cross-track width of the media.
15. The media-guiding system of claim 1 wherein the media-guiding
roller has a width in the direction of the roller axis which is
less than 20% of a cross-track width of the web of media.
16. A media-guiding system for guiding a media travelling from
upstream to downstream along a transport path in an in-track
direction, the media having a first side and an opposing second
side, comprising: a first media-guiding roller having a first
roller axis and an exterior surface having one or more grooves
formed around the exterior surface, wherein the first media-guiding
roller has a width in the direction of the first roller axis which
is less than 20% of a cross-track width of the web of media, and
wherein the media travels along the transport path past the first
media-guiding roller with the first side of the media facing the
exterior surface of the first media-guiding roller; a first air
source for providing an air flow into one or more of the grooves
formed around the exterior surface of the first media-guiding
roller, the air flow being directed between the first side of the
media and the exterior surface of the first media-guiding roller
thereby producing a Bernoulli force to draw the media toward the
exterior surface of the first media-guiding roller and providing an
increased traction between the media and the first media-guiding
roller; a second media-guiding roller having a second roller axis
and an exterior surface having one or more grooves formed around
the exterior surface, wherein the second media-guiding roller has a
width in the direction of the second roller axis which is less than
20% of the cross-track width of the web of media; and a second air
source for providing an air flow into one or more of the grooves
formed around the exterior surface of the second media-guiding
roller, the air flow being directed between the first side of the
media and the exterior surface of the second media-guiding roller
thereby producing a Bernoulli force to draw the media toward the
exterior surface of the second media-guiding roller and providing
an increased traction between the media and the second
media-guiding roller.
17. The media-guiding system of claim 16 wherein the first
media-guiding roller is located in proximity to a first edge of the
media and the second media-guiding roller is located in proximity
to an opposite second edge of the media.
18. The media-guiding system of claim 17 the first roller axis is
not parallel to the second roller axis to provide a stretching
force or a compressing force to the media in the cross-track
direction.
19. The media-guiding system of claim 1 further including a drive
mechanism that rotates the media-guiding roller around its roller
axis.
20. The media-guiding system of claim 1 wherein the media-guiding
roller has a plurality of grooves, and wherein a separate air
source is used to provide the air flow into each of the
grooves.
21. The media-guiding system of claim 1 wherein the media-guiding
roller has a plurality of grooves, and wherein the air source
includes a plenum having openings corresponding to each of the
grooves to direct the air flow into the corresponding grooves.
22. The media-guiding system of claim 1 wherein the air flow is
directed into the one or more of the grooves in a direction
substantially parallel to the grooves.
23. The media-guiding system of claim 1 wherein the exterior
surface of the media-guiding roller is concave.
24. A media-guiding system for guiding a media travelling from
upstream to downstream along a transport path in an in-track
direction, the media having a first side and an opposing second
side, comprising: a media-guiding roller having a roller axis and
an exterior surface having a plurality of grooves formed around the
exterior surface, wherein the media travels along the transport
path past the media-guiding roller with the first side of the media
facing the exterior surface of the media-guiding roller; and a
plurality of air sources for providing air flow into the grooves,
the air flow being directed between the first side of the media and
the exterior surface of the media-guiding roller thereby producing
a Bernoulli force to draw the media toward the exterior surface of
the media-guiding roller and providing an increased traction
between the media and the media-guiding roller, wherein a separate
air source is used to provide the air flow into each of the
grooves.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Reference is made to commonly assigned, co-pending U.S.
patent application Ser. No. 14/016,427, entitled "Positive pressure
web wrinkle reduction system," by Kasiske Jr., et al.; to commonly
assigned, co-pending U.S. patent application Ser. No. ______
(Docket K001684), entitled "Air shoe with roller providing lateral
constraint," by Cornell et al.; to commonly assigned, co-pending
U.S. patent application Ser. No. ______ (Docket K001724), entitled
"Air shoe with integrated roller," by Cornell et al.; to commonly
assigned, co-pending U.S. patent application Ser. No. ______
(Docket K001717), entitled "Wrinkle reduction system using
Bernoulli force rollers," by Muir et al.; and to commonly assigned,
co-pending U.S. patent application Ser. No. ______ (Docket
K001723), entitled "Media diverter system using Bernoulli force
rollers," by Muir et al., each of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention pertains to the field of media transport and
more particularly to an apparatus for guiding a web of receiver
media using rollers that impart a Bernoulli force to the receiver
media.
BACKGROUND OF THE INVENTION
[0003] In a digitally controlled inkjet printing system, a receiver
media (also referred to as a print medium) is conveyed past a
series of components. The receiver media can be a cut sheet of
receiver media or a continuous web of receiver media. A web or cut
sheet transport system physically moves the receiver media through
the printing system. As the receiver media moves through the
printing system, liquid (e.g., ink) is applied to the receiver
media by one or more printheads through a process commonly referred
to as jetting of the liquid. The jetting of liquid onto the
receiver media introduces significant moisture content to the
receiver media, particularly when the system is used to print
multiple colors on a receiver media. Due to the added moisture
content, an absorbent receiver media expands and contracts in a
non-isotropic manner, often with significant hysteresis. The
continual change of dimensional characteristics of the receiver
media can adversely affect image quality. Although drying is used
to remove moisture from the receiver media, drying can also cause
changes in the dimensional characteristics of the receiver media
that can also adversely affect image quality.
[0004] FIG. 1 illustrates a type of distortion of a receiver media
3 that can occur during an inkjet printing process. As the receiver
media 3 absorbs the water-based inks applied to it, the receiver
media 3 tends to expand. The receiver media 3 is advanced through
the system in an in-track direction 4. The perpendicular direction,
within the plane of the un-deformed receiver media, is commonly
referred to as the cross-track direction 7. Typically, as the
receiver media 3 expands in the cross-track direction 7, contact
between the receiver media 3 and contact surface 8 of rollers 2 (or
other web guiding components) in the inkjet printing system can
produce sufficient friction such that the receiver media 3 is not
free to slide in the cross-track direction 7. This can result in
localized buckling of the receiver media 3 away from the rollers 2
to create lengthwise flutes 5, also called ripples or wrinkles, in
the receiver media 3. Wrinkling of the receiver media 3 during the
printing process can lead to permanent creases in the receiver
media 3 which adversely affects image quality.
[0005] U.S. Pat. No. 3,405,855 to Daly et al., entitled "Paper
guide and drive roll assemblies," discloses a web guiding apparatus
having peripheral venting grooves to vent air carried by the
underside of the traveling web.
[0006] U.S. Pat. No. 4,322,026 to Young, Jr., entitled "Method and
apparatus for controlling a moving web," discloses a method for
smoothing and guiding a web in which the web is moved in an upward
direction past pressurized fluid discharge manifolds on either side
of the web. The manifolds direct continuous streams of pressurized
fluid, such as air, outwardly toward the side edges of the web to
smooth wrinkles in the web. Additional manifolds are used to
intermittently direct streams of fluid to laterally move and guide
the web.
[0007] U.S. Pat. No. 4,542,842 to Reba, entitled "Pneumatic
conveying method for flexible webs," discloses a method for
conveying a web using inner and outer pairs of side jet nozzles
employing the Coanda effect to propel the web while preventing
undue distortion.
[0008] U.S. Pat. No. 5,979,731 to Long et al., entitled "Method and
apparatus for preventing creases in thin webs," discloses an
apparatus for removing longitudinal wrinkles from a thin moving web
of media. The media is wrapped around a perforated cylindrical air
bar disposed in proximity to a contact roller.
[0009] U.S. Pat. No. 6,427,941 to Hikita, entitled "Web
transporting method and apparatus," discloses a web transporting
apparatus that transports a web by floating the web on air jetted
from holes formed in a roller while the edges of the web are
supported by edge rollers.
[0010] There remains a need for a means to prevent the formation of
receiver media wrinkles as a receiver media contacts web-guiding
structures in a digital printing system.
SUMMARY OF THE INVENTION
[0011] The present invention represents a media-guiding system for
guiding a media travelling from upstream to downstream along a
transport path in an in-track direction, the media having a first
side and an opposing second side, comprising:
[0012] a media-guiding roller having a roller axis and an exterior
surface having one or more grooves formed around the exterior
surface, wherein the media travels along the transport path past
the media-guiding roller with the first side of the media facing
the exterior surface of the web-guiding roller; and
[0013] an air source for providing an air flow into one or more of
the grooves, the air flow being directed between the first side of
the media and the exterior surface of the media-guiding roller
thereby producing a Bernoulli force to draw the media toward the
exterior surface of the media-guiding roller and providing an
increased traction between the media and the media-guiding
roller.
[0014] This invention has the advantage that the media can be
controlled by providing adequate fraction even when there is
minimal wrap of the media around the media-guiding roller.
[0015] It has the additional advantage that in various embodiments
the media-guiding roller can be used to steer the media, or to
provide a stretching force to prevent wrinkles from forming.
[0016] It has the further advantage that it can reduce fluttering
in receiver media webs that can result from insufficient traction
between media-guiding rollers and the receiver media web in prior
art systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates the formation of flutes in a continuous
web of receiver media due to cross-track expansion of the receiver
media;
[0018] FIG. 2 is a simplified side view of an inkjet printing
system;
[0019] FIG. 3 is a simplified side view of an inkjet printing
system for printing on both sides of a web of receiver media;
[0020] FIG. 4 shows a schematic side view of a prior art
media-guiding system;
[0021] FIG. 5 shows a schematic side view of a media-guiding system
in accordance with an embodiment of the present invention;
[0022] FIG. 6 illustrates the media-guiding system of FIG. 5 being
operated to draw the receiver media down onto the media-guiding
roller;
[0023] FIGS. 7 and 8 are perspective drawings of the media-guiding
system of FIG. 5 illustrating two different air source
configurations;
[0024] FIG. 9 illustrates an alternate embodiment of a
media-guiding system where an orientation of the roller axis can be
adjusted to steer the receiver media;
[0025] FIG. 10 illustrates a media-guiding system according to an
alternate embodiment featuring a narrow media-guiding roller having
an adjustable roller axis orientation;
[0026] FIG. 11 illustrates a media-guiding system according to an
alternate embodiment featuring a narrow media-guiding roller having
a roller axis orientation that is adjusted using an actuator;
[0027] FIG. 12 illustrates a media-guiding system according to an
alternate embodiment where a narrow media-guiding roller is used to
pull the receiver media against an edge stop to control the
cross-track position of the receiver media;
[0028] FIG. 13 illustrates a media-guiding system according to an
alternate embodiment where the air flow provided to a narrow
media-guiding roller is controlled responsive to a signal from a
media edge detector;
[0029] FIG. 14 illustrates a media-guiding system according to an
alternate embodiment where the air flow provided to two narrow
media-guiding rollers is controlled responsive to signals from one
or more media edge detectors;
[0030] FIG. 15 illustrates a wrinkle-reduction system which uses
two narrow media-guiding rollers to provide a stretching force to
the receiver media;
[0031] FIGS. 16A-16B illustrate a sheet-diverter system which uses
a media-guiding roller to direct a media sheet into one of two
media paths;
[0032] FIG. 17 illustrates a sheet-diverter system which uses two
media-guiding rollers to direct a media sheet into one of two media
paths;
[0033] FIG. 18 illustrates a sheet-diverter system which uses
media-guiding rollers to direct a media sheet a left or right media
path;
[0034] FIG. 19 is a perspective diagram illustrating a web-guiding
system which includes a grooved web-guiding roller providing a
Bernoulli force and a fixed web-guiding structure in accordance
with an alternate embodiment;
[0035] FIG. 20A illustrates a prior art concave media-guiding
roller; and
[0036] FIG. 20B illustrates a grooved concave media-guiding roller
in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The present description will be directed in particular to
elements forming part of, or cooperating more directly with, an
apparatus in accordance with the present invention. It is to be
understood that elements not specifically shown, labeled, or
described can take various forms well known to those skilled in the
art. In the following description and drawings, identical reference
numerals have been used, where possible, to designate identical
elements. It is to be understood that elements and components can
be referred to in singular or plural form, as appropriate, without
limiting the scope of the invention.
[0038] The invention is inclusive of combinations of the
embodiments described herein. References to "a particular
embodiment" and the like refer to features that are present in at
least one embodiment of the invention. Separate references to "an
embodiment" or "particular embodiments" or the like do not
necessarily refer to the same embodiment or embodiments; however,
such embodiments are not mutually exclusive, unless so indicated or
as are readily apparent to one of skill in the art. It should be
noted that, unless otherwise explicitly noted or required by
context, the word "or" is used in this disclosure in a
non-exclusive sense.
[0039] The example embodiments of the present invention are
illustrated schematically and may not be to scale for the sake of
clarity. One of ordinary skill in the art will be able to readily
determine the specific size and interconnections of the elements of
the example embodiments of the present invention.
[0040] As described herein, the exemplary embodiments of the
present invention provide receiver media guiding components useful
for guiding the receiver media in inkjet printing systems. However,
many other applications are emerging which use inkjet printheads to
emit liquids (other than inks) that need to be finely metered and
deposited with high spatial precision. Such liquids include inks,
both water based and solvent based, that include one or more dyes
or pigments. These liquids also include various substrate coatings
and treatments, various medicinal materials, and functional
materials useful for forming, for example, various circuitry
components or structural components. As such, as described herein,
the terms "liquid" and "ink" refer to any material that is ejected
by the printhead or printhead components described below.
[0041] Inkjet printing is commonly used for printing on paper,
however, there are numerous other materials in which inkjet is
appropriate. For example, vinyl sheets, plastic sheets, textiles,
paperboard and corrugated cardboard can comprise the receiver
media. Additionally, although the term inkjet is often used to
describe the printing process, the term jetting is also appropriate
wherever ink or other liquids is applied in a consistent, metered
fashion, particularly if the desired result is a thin layer or
coating.
[0042] Inkjet printing is a non-contact application of an ink to a
receiver media. Typically, one of two types of ink jetting
mechanisms is used, and is categorized by technology as either
drop-on-demand inkjet printing or continuous inkjet printing.
[0043] Drop-on-demand inkjet printing provides ink drops that
impact upon a recording surface using a pressurization actuator,
for example, a thermal, piezoelectric or electrostatic actuator.
One commonly practiced drop-on-demand inkjet type uses thermal
energy to eject ink drops from a nozzle. A heater, located at or
near the nozzle, heats the ink sufficiently to form a vapor bubble
that creates enough internal pressure to eject an ink drop. This
form of inkjet is commonly termed "thermal inkjet." A second
commonly practiced drop-on-demand inkjet type uses piezoelectric
actuators to change the volume of an ink chamber to eject an ink
drop.
[0044] The second technology commonly referred to as "continuous"
inkjet printing, uses a pressurized ink source to produce a
continuous liquid jet stream of ink by forcing ink, under pressure,
through a nozzle. The stream of ink is perturbed using a drop
forming mechanism such that the liquid jet breaks up into drops of
ink in a predictable manner. One continuous inkjet printing type
uses thermal stimulation of the liquid jet with a heater to form
drops that eventually become printing drops and non-printing drops.
Printing occurs by selectively deflecting either the printing drops
or the non-printing drops and catching the non-printing drops using
catchers. Various approaches for selectively deflecting drops have
been developed including electrostatic deflection, air deflection,
and thermal deflection.
[0045] There are typically two types of receiver media used with
inkjet printing systems. The first type of receiver media is in the
form of a continuous web, while the second type of receiver media
is in the form of cut sheets. The continuous web of receiver media
refers to a continuous strip of receiver media, generally
originating from a source roll. The continuous web of receiver
media is moved relative to the inkjet printing system components
using a web transport system, which typically include drive
rollers, web guide rollers, and web tension sensors. Cut sheets
refer to individual sheets of receiver media that are moved
relative to the inkjet printing system components via rollers and
drive wheels or via a conveyor belt system that is routed through
the inkjet printing system.
[0046] The invention described herein is applicable to both
drop-on-demand and continuous inkjet printing technologies that
print on continuous webs of receiver media. As such, the term
"printhead" as used herein is intended to be generic and not
specific to either technology. Additionally, the invention
described herein is also applicable to other types of printing
systems, such as offset printing and electrophotographic printing,
that print on continuous webs of receiver media.
[0047] The terms "upstream" and "downstream" are terms of art
referring to relative positions along the transport path of the
receiver media; points on the receiver media move along the
transport path from upstream to downstream.
[0048] Referring to FIG. 2, there is shown a simplified side view
of a portion of a digital printing system 100 for printing on a
first side 15 of a continuous web of receiver media 10. The
printing system 100 includes a printing module 50 which includes
printheads 20a, 20b, 20c, 20d, dryers 40, and a quality control
sensor 45. In this exemplary system, the first printhead 20a jets
cyan ink, the second printhead 20b jets magenta ink, the third
printhead 20c jets yellow ink, and the fourth printhead 20d jets
black ink.
[0049] Below each printhead 20a, 20b, 20c, 20d is a media guide
assembly including print line rollers 31 and 32 that guide the
continuous web of receiver media 10 past a first print line 21 and
a second print line 22 as the receiver media 10 is advanced along a
media path in the in-track direction 4. Below each dryer 40 is at
least one dryer roller 41 for controlling the position of the web
of receiver media 10 near the dryers 40.
[0050] Receiver media 10 originates from a source roll 11 of
unprinted receiver media 10, and printed receiver media 10 is wound
onto a take-up roll 12. Other details of the printing module 50 and
the printing system 100 are not shown in FIG. 2 for simplicity. For
example, to the left of printing module 50, a first zone 51
(illustrated as a dashed line region in receiver media 10) can
include a slack loop, a web tensioning system, an edge guide and
other elements that are not shown. To the right of printing module
50, a second zone 52 (illustrated as a dashed line region in
receiver media 10) can include a turnover mechanism and a second
printing module similar to printing module 50 for printing on a
second side of the receiver media 10.
[0051] Referring to FIG. 3, there is shown a simplified side view
of a portion of a printing system 110 for printing on both a first
side 15 and a second side 16 of a continuous web of receiver media
10. Printing system 110 includes a first printing module 55, for
printing on a first side 15 of the continuous web, having two
printheads 20a, 20b and a dryer 40; a turnover mechanism 60; and a
second printing module 65, for printing on the second side of the
continuous web, having two printheads 25a and 25b and a dryer 40. A
web-guiding system 30 guides the web of receiver media 10 from
upstream to downstream along a transport path in an in-track
direction 4 past through the first printing module 55 and the
second printing module 65. The web-guiding system 30 includes
rollers aligned with the print lines of the printheads 20a, 20b,
25a, and 25b. These rollers maintain the receiver media 10 at a
fixed spacing from the printing modules to ensure a consistent time
of flight for the print drops emitted by the printheads. The
web-guiding system 30 also includes a web-guiding structure 66,
which can be a roller for example, positioned near the exit of
first printing module 55 for redirecting a direction of travel of
the web of receiver media 10 along exit direction 9 in order to
guide web of receiver media 10 toward the turnover mechanism 60.
The movement of the receiver media of the guiding rollers of the
web guide system also maintains the cross-track position of the
continuous web provided there is sufficient traction between the
continuous web and the guiding rollers.
[0052] FIG. 4 shows a side view of prior art system where a
continuous web of receiver media 10 moves in an in-track direction
4 past a media-guiding roller 70 rotating in a rotation direction
72. As the continuous web moves through the air its motion can
entrain a flow of air, denoted by entrained airflow 76, causing the
entrained air to move together with the receiver media along both
the first side 15 and the second side 16 of the receiver media 10.
The velocity of the entrained airflow 76 at the surfaces of the
receiver media 10 is approximately equal to the velocity of the
receiver media 10, and the velocity of the entrained airflow 76
drops off with increasing distance from the receiver media 10.
[0053] If there is insufficient wrap of the web of receiver media
10 around the media-guiding roller 70 or insufficient tension in
the web of receiver media 10, the entrained airflow 76 can cause
the receiver media 10 to float free of the media-guiding roller 70
on a thin air cushion 74 of the entrained air, and can induce
fluttering of the receiver media 10, a vibration of the receiver
media 10 perpendicular to the in-track direction 4 and the
cross-track direction 7 (FIG. 1). When the receiver media 10 is
floating free of the media-guiding roller 70, the media-guiding
roller 70 is no longer able to provide a lateral constraint on the
web of receiver media 10, allowing the receiver media 10 to drift
in the cross-track direction 7.
[0054] To avoid these stability problems, U.S. Pat. No. 3,405,855
to Daly Jr. et al., entitled "Paper guide and drive roll
assemblies," introduced grooves into the media contact surface of
the media-guiding roller 70. The air entrained by the moving web of
receiver media 10 can flow into the grooves of the roller, allowing
the web of receiver media 10 to contact the contact surface of the
media-guiding roller 70 in the area between the grooves. There are
times when design constraints of the printing system are such that
little or no wrap is possible around a media-guiding roller 70. In
such printing systems, it has been found that even the use of a
grooved guiding roller is insufficient to ensure traction between
the receiver media 10 and the grooved surface of the media-guiding
roller 70. Such printing systems are therefore susceptible to
cross-track wander of the receiver media 10, and also to media
flutter. The present invention overcomes the limitations of such
prior art web-guiding systems.
[0055] FIG. 5 is a schematic side view of a media-guiding system 78
according to an embodiment the present invention, showing a portion
of the receiver media 10 as it passes by a media-guiding roller 80
having a roller axis 81 and rotating in a rotation direction 82.
The media-guiding roller 80 has one or more grooves 84 formed
around its exterior surface 83. The grooves 84 are typically
aligned parallel to the direction of the surface rotation of the
media-guiding roller 80, so that the grooves 84 extend around the
circumference of media-guiding roller 80. First side 15 of the
receiver media 10 faces toward the exterior surface 83 of the
media-guiding roller 80, while the second side 16 faces away from
the media-guiding roller 80. An air source 86 directs a flow of air
88 into the one or more grooves 84 providing an airflow 90. In a
preferred embodiment, the airflow 90 is substantially parallel to
the plane of the receiver media 10 (i.e., a vector representing the
direction of airflow 525 is within about 10.degree. of being
parallel to the plane of the receiver media 10) and to the grooves
84 (i.e., a vector representing the direction of airflow 90 is
within about 10.degree. of being parallel to a plane through the
center of the groove 84, where the plane through the center of the
groove 84 will generally be perpendicular to the roller axis
81.)
[0056] The one or more grooves 84 serve as air channels for the
airflow 90. As the airflow 90 passes through a groove 84 between
the first side 15 of receiver media 10 and the exterior surface 83
of the media-guiding roller 80, the contour of the bottom of the
groove 84 forms a constriction 92 to the airflow 90. The well-known
"continuity principle" of fluid dynamics requires the airflow 90 to
accelerate as it passes through the constriction 92. According to
the well-known Bernoulli's Principle, the increased velocity of the
airflow 90 at the constriction 92 is accompanied by the development
of a low pressure zone between the high point of the groove 84 and
the receiver media 10. A pressure differential is therefore
developed from the second side 16 to the first side 15 of the
receiver media 10, resulting in a Bernoulli force F on the receiver
media 10 which draws the receiver media 10 down toward, or into
contact with, the exterior surface 83 of the media-guiding roller
80. As a result, the media-guiding roller 80 is able to provide a
lateral constraint on the web of receiver media 10, preventing the
receiver media 10 from drifting in the cross-track direction 7
(FIG. 1).
[0057] An advantage provided by the media-guiding system 78 of the
present invention is that all of the system components are located
on one side of the receiver media 10. This is useful in many
systems where there are tight geometric constraints.
[0058] In some embodiments, the media-guiding roller 80 is a
passive roller having no drive mechanism so that it rotates freely
in response to traction with the receiver media 10. In other
embodiments, a drive mechanism (not shown) can be used to rotate
the media-guiding roller 80 around its roller axis 81. In such
configurations, the media-guiding roller 80 can be used to impart a
force on the receiver media 10 to move it along the transport path
in the in-track direction 4. Driven media-guiding rollers 80 are of
particular value when the receiver media 10 is in the form of cut
sheets, as the intermittent passage of individual sheets past the
media-guiding roller 80 may be insufficient to maintain the
rotation of the media-guiding roller.
[0059] FIG. 6 illustrates the media-guiding system 78 of FIG. 5
being operated such that the airflow 90 from the air source 86 is
being directed into the one or more grooves 84 of the media-guiding
roller 80, thereby causing the receiver media 10 to be deflected
downward into contact with the exterior surface 83 of the
media-guiding roller 80 as a result of the Bernoulli force F. In
some embodiments, an optional airflow guide 85 can be provided to
channel the airflow 90 into the grooves 84. The receiver media 10
is shown as contacting the exterior surface 83 of the media-guiding
roller 80 for a wrap angle of a. While a larger wrap angle is shown
in FIG. 6 for clarity, in practice, the wrap angle .alpha. will
typically be less than about 5.degree., and will often be less than
about 2.degree.. In some embodiments, if the air source 86 is
turned off so that it doesn't provide any airflow 90, the receiver
media 10 may be separated from the exterior surface 83 of the
media-guiding roller 80 by a small gap as shown in FIG. 5, or may
contact the media-guiding roller 80 with a small wrap angle (e.g.,
between 0.degree. and 2.degree.).
[0060] Commonly-assigned U.S. patent application Ser. No.
14/016,427, entitled: "Positive pressure web wrinkle reduction
system," by Kasiske Jr., et al, describes a web-guiding system
where an air source is used to direct an airflow through a pattern
of recesses in a web-guiding structure. The described
configurations prevent wrinkles from forming in the receiver media
as it passes around the web-guiding structure by causing portions
of the receiver media overlying the recesses to lift away from the
web-guiding structure. In some of the embodiments described by
Kasiske Jr., et al., the recesses are grooves similar to those
described with respect to FIG. 5 in the present disclosure. Whether
the airflow 90 through the grooves 84 produces a Bernoulli force F
to draws the receiver media 10 down toward the media-guiding roller
80, or whether it produces a lifting force to lift the portions of
the receiver media 10 overlying the grooves 84 away from the
media-guiding roller 80 will depend on a number of different
factors including the wrap angle of the receiver media 10, the rate
of the airflow 90, the geometry of the grooves 84, and the presence
of any blockages to block air flow from passing through the
grooves. Generally, it has been found that an adequate downward
Bernoulli force F results for relatively small wrap angles (e.g.,
less than about 5-10.degree.) and for open grooves having no
blockages, whereas a lifting force results for relatively large
wrap angles, particularly when blockages (e.g, fingers 91 in FIG.
15 of Kasiske Jr., et al.) are inserted into the grooves to block
the airflow 90.
[0061] In an exemplary embodiment, the media-guiding roller 80 has
a radius of 2.5 inches, the grooves 84 have a groove width w.sub.g
of 0.375 inches and a groove depth d.sub.g of 0.125 inches. The
exit of the air source 86 is preferably sized such that the width
of the opening is approximately the same as the groove width
w.sub.g, and the height of the opening is somewhat larger than the
groove depth d.sub.g of the grooves 84 to provide an airflow depth
d.sub.a that will be reduced as it passes through the constriction
92 in order to accelerate the airflow 90 and produce the Bernoulli
force F. In the exemplary embodiment, the groove depth d.sub.g is
smaller than the airflow depth d.sub.a by about 20% (i.e., the
airflow depth d.sub.a entering the grooves 84 is about 0.150
inches). In other embodiments, other air flow depths d.sub.a can be
used to provide different amounts of constriction. For example, in
some embodiments the groove depth d.sub.g can be smaller than the
airflow depth d.sub.a entering the grooves 84 by about 10-50%.
[0062] The magnitude of the Bernoulli force F will be related to
magnitude of the airflow 90 provided into of the grooves 84,
together with the amount of constriction 92 the airflow 90
experiences as it passes by the grooves 84. In an exemplary
embodiment, it has been found that an acceptable Bernoulli force F
to guide the receiver media 10 with the media-guiding roller 80 is
obtained when the air source 86 provides an airflow 90 having a
velocity of about 100-400 m/s, although different velocities can be
used depending on the geometry of the grooves 84 and the
requirements of the particular application.
[0063] FIGS. 7 and 8 show two different embodiments for the air
source 86 that directs airflow 90 into the grooves 84 of the
media-guiding roller 80. The air source 86 of the FIG. 7 embodiment
uses a common plenum 91 to direct the air flow into each of the
grooves. The plenum 91 is partitioned by barriers 87 to form
individual openings 89 aligned with the grooves 84. In FIG. 8, a
plurality of individual air sources 86 are used to direct airflow
90 into corresponding grooves 84 of the media-guiding roller 80.
This approach has the advantage that it enables the flow rate of
the airflow 90 to be adjusted or turned off on a groove-by-groove
basis (e.g., to account for different media widths). In the
illustrated embodiments, the grooves 84 are shown as having sharp
corners at the top and bottom edges. In alternate embodiments, the
grooves 84 can have rounded corners at one or both of the top or
bottom edges. This can have the advantage that it will be less
likely to crease the receiver media 10 when it is pulled down into
the grooves 84.
[0064] The media-guiding system 78 can be used to provide a variety
of media control process functions. For example, in some printing
systems 110 (FIG. 3), the web-guiding structure 66 can be an air
shoe which enables the receiver media to travel around the
web-guiding structure 66 at least partially on a cushion of air.
While this can provide various advantages such as reducing the
likelihood of wrinkling the receiver media 10, the lack of traction
between the receiver media and the air shoe removes a lateral
constraint on the receiver media 10, allowing the receiver media to
drift in the cross-track direction as it passes around the air
shoe. In some embodiments, the media-guiding system 78 can be
positioned in proximity to the air shoe to provide a lateral
constraint to the receiver media 10 in close proximity to the air
shoe in order to stabilize the cross-track position of the receiver
media as the media passes around the air shoe. In an exemplary
embodiment, the media-guiding system 78 of the present invention
can be used with the air shoe configuration described in commonly
assigned, co-pending U.S. patent application Ser. No. ______
(Docket K001684), entitled "Air shoe with lateral constraint," by
Cornell et al., which is incorporated herein by reference.
[0065] FIG. 9 illustrates an embodiment of a media-guiding system
79 in which the roller axis 81 of the media-guiding roller 80 can
be tilted using a roller control mechanism. In particular, the
media-guiding roller 80 is mounted on pivot arms 93 that can be
steered by an actuator 94. A steering controller 95 receives
signals from one or more media edge detectors 96 and provides
signals to the actuator 94 thereby enabling the web of receiver
media 10 to be steered to follow a desired path. For example, if
the media edge detector 96 detects that the receiver media 10 is
starting to drift to one side, then the steering controller 95 can
cause the actuator 94 to tilt the roller axis 81 of the
media-guiding roller 80, thereby steering the receiver media 10 to
compensate for the drift. Due to the airflow 90 through the grooves
84 of the media-guiding roller 80, the receiver media 10 can be
brought into sufficient contact with the media-guiding roller 80 to
have the traction needed for the media-guiding roller 80 to be able
to steer the web of receiver media 10. The present invention has
the advantage that a sufficient steering force can be provided,
even in systems where there is minimal wrap around the steered
media-guiding roller 80.
[0066] When the actuator 94 tilts the media-guiding roller 80 so
that the roller axis 81 is oriented in a non-orthogonal direction
relative to the in-track direction 4 (i.e., in a direction that is
not parallel to the cross-track direction 7), when the air source
86 is activated the traction between the media-guiding roller 80
and the receiver media 10 will steer the web of receiver media 10
in accordance with the tilt direction. In the configuration shown
in FIG. 9, if the bottom portion of the roller axis 81 is tilted
toward the left side of the figure, then the receiver media 10 will
be steered (i.e., deflected) toward the bottom side of the figure.
Conversely, if the bottom portion of the roller axis 81 is tilted
toward the right side of the figure, then the receiver media 10
will be steered toward the top side of the figure. When the roller
axis 81 is oriented in a substantially orthogonal direction
relative to the in-track direction 4 (i.e., the roller axis 81 is
substantially parallel to the cross-track direction 7), or if the
airflow 90 is turned off, the receiver media 10 will be maintained
at its current cross-track position.
[0067] In the configurations shown in FIGS. 7-9, the media-guiding
roller 80 spans the entire cross-track width of the receiver media
10. FIG. 10 shows an embodiment of a media-guiding system 170 that
uses a narrow media-guiding roller 180, having a single groove 84
in its exterior surface 83. In this case, the width of
media-guiding roller 180 in the cross-track direction 7 spans only
a relatively small fraction (e.g., less than 20%) of the
cross-track width of the receiver media 10. This type of
media-guiding roller 180 is sometimes referred to as a "wheel." In
other embodiments (no shown), the narrow media-guiding roller 180
may have a plurality of grooves 84. When the media-guiding roller
180 is positioned adjacent to the web of receiver media 10, and the
air source 86 is activated to direct airflow 90 into the groove 84
between the exterior surface 83 of the grooved media-guiding roller
180 and the receiver media 10, the low pressure zone that is
generated as the air flows through the groove 84 creates a
Bernoulli force on the receiver media 10, which causes the receiver
media 10 to move into contact with (or to increase its contact
with) the exterior surface 83 of the media-guiding roller 180. One
application of such a media-guiding system 170 is as a web steering
system. In the exemplary embodiment of FIG. 10, the media-guiding
roller 180 and the air source 86 are mounted on a common frame 99.
The frame 99 can be rotated around the vertical rotation axis 98 by
an active steering system. By rotating the media-guiding roller 180
about the rotation axis 98, the direction of travel of the receiver
media 10 can be altered. The active steering system can include a
stepper motor 97 to rotate the frame 99 holding the media-guiding
roller 180, in response to steering signals provided by a steering
controller 95. In some embodiments, the steering controller 95
provides the steering signals in response to output signals from
one or more media edge detectors 96. In this way, any drift in the
cross-track position of the receiver media 10 can be corrected.
[0068] FIG. 11 shows another embodiment of a media guiding system
171, which is similar to that shown in FIG. 10. In this case, the
frame 99 rotates around a rotation axis 98 toward the rear of the
frame 99, and an actuator 94 is used to steer the media-guiding
roller 180 in response to signals received from the steering
controller 95.
[0069] FIG. 12 shows another embodiment of a media guiding system
172. In the case, the frame 99 on which the media-guiding roller
180 is mounted is castered and is biased using a spring 182 to skew
the roller axis 81 of the media-guiding roller 180 relative to the
in-track direction 4 of the receiver media 10. The airflow 90
through the groove 84 of the media-guiding roller 180 causes the
receiver media 10 to have sufficient contact with the media-guiding
roller 180 so that the skew of the media-guiding roller 180 causes
the receiver media 10 to be pushed against an edge stop 184,
thereby accurately maintaining the cross-track position of the
receiver media 10.
[0070] FIG. 13 shows another embodiment of a media guiding system
173, which is similar to that shown FIG. 12 where the frame 99 on
which the media-guiding roller 180 is mounted is castered and is
spring biased to skew the media-guiding roller 180. In this case,
one or more media edge detectors 96 provide signals to steering
controller 95 related to the cross-track position of the receiver
media 10. In response to the signals from the media edge detectors
96, the steering controller 95 generates signals to alter the
cross-track position of the receiver media 10. In this embodiment,
rather than providing signals to vary the skew of the media-guiding
roller 180, the steering controller 95 provides signals to alter
the airflow 90 provided by the air source 86. When no airflow 90 is
provided, the receiver media 10 doesn't contact the media-guiding
roller 180 so that the skewed media-guiding roller 180 has no
effect on the cross-track position of the receiver media 10. When a
sufficient rate of airflow 90 is provided through the groove 84 of
the media-guiding roller 180, the receiver media 10 is pulled into
contact with the exterior surface 83 of the media-guiding roller
180 such that the media-guiding roller 180 moves with minimal slip
relative to the receiver media 10. The skew on the media-guiding
roller 180 relative to the receiver media 10 therefore provides a
significant lateral force bias to shift the receiver media 10 in
the cross-track direction. At rates of airflow 90 between these two
conditions, the skewed media-guiding roller 180 provides
intermediate amounts of lateral force to the receiver media 10. In
this way, the steering controller 95 is able to control the amount
of lateral force applied to the receiver media 10 by controlling
the rate of airflow 90 provided by the air source 86.
[0071] FIG. 14 shows another embodiment of a media guiding system
174 having two media-guiding rollers 180, each located near an edge
of the receiver media 10 and each skewed outward relative to
direction of media travel (i.e., the in-track direction 4). Like
the media-guiding rollers 180 in FIGS. 10-13, the width of both
media-guiding rollers 180 in the cross-track direction 7 spans only
a relatively small fraction (e.g., less than 20%) of the
cross-track width of the receiver media 10. The steering controller
95 receives signals from one or more media edge detectors 96. Based
on the sensed cross-track position of the receiver media 10, the
steering controller 95 sends signals to the air sources 86
associated with the two media-guiding rollers 180 to adjust the
rate of airflow 90 into the grooves 84 in the two media-guiding
rollers 180. By directing a sufficient airflow 90 into the groove
84 of a selected one of the skewed media-guiding rollers 180, the
receiver media 10 can be made to contact and have traction with
that media-guiding roller. The receiver media 10 is thereby steered
in a corresponding cross-track direction.
[0072] FIG. 15 shows another embodiment of a media-guiding system
175 useful for providing a wrinkle-reduction feature. Like the
previous embodiment shown in FIG. 14, this system has two
media-guiding rollers 180, each skewed outward relative to the
direction of media travel (i.e., in-track direction 4). In this
case, a controller 195 controls the airflow 90 of the two air
sources 86 in a balanced manner so both air sources 86 provide a
similar amount of airflow 90. At sufficient rates of airflow 90
from the air sources 86, the receiver media 10 is drawn down into
good contact with exterior surfaces 83 of the grooved media-guiding
rollers 180. As the media-guiding rollers 180 are skewed away from
each other, the media-guiding rollers 180 each apply a lateral
force on the receiver media 10 to laterally spread the receiver
media 10, thereby providing a wrinkle reduction process. When no
airflow 90 is provided from either of the air sources 86, no
spreading force is applied on the receiver media 10. By controlling
the airflow 90 to intermediate air flow rates, the media-guiding
system 175 can produce intermediate levels of spreading force on
the receiver media 10. In some embodiments, the controller 195
receives signals from a flute detection system 185.
[0073] The flute detection system 185 can use any method known in
the art to detect the presence of any flutes (also known as
wrinkles or ripples) in the receiver media 10. Preferably the flute
detection system 185 detects the height and spacing of any detected
flutes. In an exemplary embodiment, the flute detection system 185
uses laser triangulation to detect and characterize any ripples or
flutes in the receiver media 10. In an alternate embodiment, the
flute detection system 185 projects a grating pattern onto the
receiver media 10 from one angle and the projected grating pattern
on the receiver media 10 is viewed, typically with a digital
camera, from a different angle; a procedure known as fringe
projection or projection moire interferometry. Any distortion in
the surface of the receiver media 10 causes the viewed grating
lines to be warped, enabling any flutes to be easily detected. In
an another alternate embodiment, the receiver media 10 can be
illuminated by a light source at a low incidence angle, and a
digital imaging system can be used to capture an image of the
receiver media 10. In this case, the sides of the flutes facing the
light source will show up as lighter regions, while the sides of
the flutes facing away from the light source will show up as darker
regions.
[0074] Based on the detection of flutes (i.e., wrinkles), including
the height and spacing of flutes, the controller 195 adjusts the
rate of airflow 90 to control the degree of spreading of the
receiver media 10 to keep the fluting below an acceptable level.
For example, the rate of airflow 90 can be increased to a higher
level when larger flutes are detected relative to when smaller
flutes are detected.
[0075] In another embodiment (not shown), force sensors attached to
the media-guiding rollers 180 measure the lateral force applied by
the media-guiding rollers 180 on the receiver media 10. The
controller 195 regulates the airflow 90 provided by air sources 86
such that the spreading force doesn't exceed the tensile strength
of the receiver media 10. As the tensile force applied by the
receiver media 10 on the media-guiding rollers 180 will be low
until the receiver media 10 has been spread sufficiently to flatten
the ripples and fluting of the receiver media 10, the output of the
force sensors attached to the media-guiding rollers 180 can be
analyzed to detect when a sufficient spreading force has been
applied to the receiver media 10 to sufficiently flatten the
flutes, and the airflow 90 can be controlled to maintain the
desired level of spreading force.
[0076] In some embodiments, the two media-guiding rollers 180 in
FIG. 15 can be controlled to provide both the media spreading
function described above together with the steering function
described with respect to FIG. 14. In this case, the amount of
airflow 90 provided by one air source 86 can be adjusted to be
larger than that provided by the other air source 86 to steer the
receiver media 10 in response to signals from one or more media
edge detectors 96, while still providing a spreading force on the
receiver media 10.
[0077] In some embodiments, the tilt angle of the roller axes 81 of
the media-guiding rollers 180 can also be controlled (e.g., using
the actuator mechanism shown in FIG. 11). By independently
controlling the tilt angles, the media-guiding rollers 180 can be
used to both steer the receiver media 10, as well as to provide a
stretching force to reduce media wrinkling.
[0078] In an alternate embodiment, the two media-guiding rollers
180 in FIG. 15 can be skewed inward relative to the direction of
media travel (i.e., in-track direction 4). In this way, the
media-guiding rollers 180 can provide a compressing force to the
receiver media 10 in the cross-track direction. Such an embodiment
can be used to introduce a buckle into the receiver media, in
preparation, for example, for a folding operation.
[0079] In some embodiments, the tilt angle of the roller axes 81 of
the media-guiding rollers 180 can also be controlled (e.g., using
the actuator mechanism shown in FIG. 11). By independently
controlling the tilt angles, the media-guiding rollers 180 can be
used to both steer the receiver media 10, as well as to provide a
stretching force or a compressive force to the receiver media 10.
For example, if both media-guiding rollers 180 are tilted outward
with tilt angles of the same magnitude, a stretching force will be
provided to the receiver media 10. However, if one of the
media-guiding rollers 180 is tilted outward with a larger tilt
angle, then the receiver media 10 can be steered while still
providing a stretching force.
[0080] While the above embodiments of Bernoulli-force media-guiding
rollers 80, 180 have been described with respect to printing
systems 100, 110 configured to print on a continuous web of
receiver media 10, it will be obvious to one skilled in the art
that the disclosed Bernoulli-force media-guiding rollers can also
be used in media-guiding systems for cut sheets of media. In some
embodiments, the Bernoulli-force media-guiding rollers can be used
in cut sheet media transports for operations such as cross-track
steering and cross-track spreading of cut sheets, which are similar
to the analogous operations which have been discussed above for
web-fed media transports. In other embodiments, the Bernoulli-force
media-guiding rollers of the present invention can also be used to
alter the path taken by a sheet of media.
[0081] FIGS. 16A-16B illustrate an embodiment of a sheet-diverter
system 200 in which a media sheet 210 traveling horizontally in
in-track direction 4 is diverted either upward or downward with
respect to the in-track direction 4 and guided into either an upper
media path 220 or a lower media path 225, respectively, by
selective activation of the air source 86 in a roller assembly 260,
wherein the roller assembly 260 includes both an air source 86 and
a media-guiding roller 80. The media sheet 210 is moved along an
input media path 205 defined by media guides 215 using a media
drive mechanism (not shown), such as drive rollers or a transport
belt. FIG. 16A illustrates the case where the air source 86 is not
activated. In this case, the media sheet 210 is undeviated as it
passes by the media-guiding roller 80 and moves forward into the
upper media path 220.
[0082] In FIG. 16B, the air source 86 has been activated by a
controller 295 to provide an airflow 90 which is directed into the
groove 84 in the media-guiding roller 80, and a motor (not shown)
has been activated to drive the media-guiding roller 80 in the
rotation direction 82. As discussed earlier, the flow of air
through the constriction 92 produces a Bernoulli force F which
pulls the first side 15 of the media sheet 210 down into contact
with the exterior surface 83 of the media-guiding roller 80,
entraining the media sheet 210 around the media-guiding roller 80
for some wrap angle .alpha.. This causes leading edge 212 of the
media sheet 210 to be diverted downward, bending the media sheet
210 and directing the media sheet 210 into the lower media path
225. In some embodiments, the motor driving the media-guiding
roller 80 is activated continuously, even when the media sheet 210
is to be directed into the upper media path 220, but since the air
source 86 is not activated, no Bernoulli force F is present to
direct the media sheet 210 into contact with the media-guiding
roller 80 and to direct it into the lower media path 220.
[0083] FIG. 17 illustrates another embodiment of a sheet-diverter
system 201 in which a media sheet 210 is guided into either an
upper media path 220 or a lower media path 225. In this case, a
second roller assembly 261, including a second upper air source 286
and a second upper media-guiding roller 280, is provided facing the
second side 16 of the media sheet 210. The upper media-guiding
roller 280 has one or more grooves 284 formed into its external
surface 283, and rotates around a roller axis 281 in a rotation
direction 282. The rotation direction 282 is opposite to the
rotation direction 82 of the first media-guiding roller 80. The
controller 295 controls which media path that the media sheet 210
by selectively activating the corresponding air source 86, 286. As
in FIG. 16B, the lower air source 86 can be activated to divert the
media sheet 210 into the lower media path 225. However, to divert
the media sheet 210 into the upper media path 220, the upper air
source 286 is activated to provide an airflow 290 into the groove
284 in the upper media-guiding roller 280, and a motor (not shown)
is activated to drive the media-guiding roller 280 in the rotation
direction 282. The flow of air through the constriction 292
produces a Bernoulli force F which pulls the second side 16 of the
media sheet 210 up into contact with the exterior surface 283 of
the media-guiding roller 280, entraining the media sheet 210 around
the media-guiding roller 280. This causes the leading edge 212 of
the media sheet 210 to be diverted upward, bending the media sheet
210 and directing the media sheet 210 into the upper media path
220. In some embodiments, the motors driving both media-guiding
rollers 80, 280 are activated continuously, even when the media
sheet 210 is to be directed into the other media path.
[0084] The embodiments of FIGS. 16-17 are directed to diverting a
media sheet 210 vertically into either an upper media path 220 or a
lower media path 225. FIG. 18 illustrates another embodiment of a
sheet-diverter system 202 which uses media-guiding rollers 180 to
divert a media sheet 210 laterally to direct it into either a left
media path 230 or a right media path 235. In this configuration,
the media sheet 210 travels along an input media path 205 using a
media drive mechanism (not shown), such as drive rollers or a
transport belt.
[0085] When the media sheet 210 reaches a transfer position 240, it
can be directed into either the left media path 230 or the right
media path 235. To direct the media sheet 210 into the left media
path 230, controller 295 leaves the air sources 86 in a deactivated
state. The media sheet 210 will then continue in an undeviated
direction and will move into the left media path 230. To divert the
media sheet 210 into the right media path 235, the controller 295
activates the air sources 86 in the roller assemblies 260 when the
media sheet 210 reaches the transfer position 240. As discussed
above, directing the airflow 90 from the air sources 86 through the
grooves 84 in the media-guiding rollers 180 causes the media sheet
210 to be drawn down into contact with the rotating media-guiding
rollers 180 by a Bernoulli force. The resulting traction will cause
the media sheet 210 to be moved by the media-guiding rollers 180
along a media diversion path 245 until it reaches a shifted
position 250, which is laterally shifted relative to the input
media path 205, at which time the air sources 86 are deactivated by
the controller 295. The media sheet 210 can then proceed along the
right media path 235 using any appropriate media drive mechanism
(not shown).
[0086] The direction of the media diversion path 245 is determined
by the orientation of the roller assemblies 260. Generally, the
direction of the media diversion path 245 will be perpendicular to
the direction of the roller axis 81, and parallel to the direction
of the groove 84. In the illustrated embodiment, the media
diversion path 245 is angled at approximately 30.degree. relative
to the in-track direction 4, however, this is not a requirement. In
other embodiments, different directions can be used for the media
diversion path 245 as long as the direction includes a lateral
component. For example, in some embodiments, the roller assemblies
260 can be oriented such that the rotation axis 81 is parallel to
the in-track direction 4. In this case, the direction of the media
diversion path 245 will be perpendicular to the in-track direction
4, and will therefore have only a lateral component and will have
no forward component.
[0087] Typically, media sensors (not shown) are used to detect when
the media sheet 210 has reached the transfer position 210 and the
shifted position 250. Signals from the media sensors are fed into
the controller 295 and are used to determine the times that the air
sources 86 are activated and deactivated.
[0088] The illustrated embodiment shows roller assemblies 260 are
positioned at different points along the media diversion path 245.
They are spaced such that at least one of the media-guiding rollers
180 will be in contact with the media sheet 210 at all times as it
moves along the media diversion path 245. In other embodiments, a
single media-guiding roller 180 can be used, or more than two
media-guiding rollers 180 can be used, depending on the geometry of
the media diversion path.
[0089] In the illustrated embodiment, the media-guiding rollers 180
are used to divert the media sheet 210 into the right media path
235, which is shifted laterally to the right of the input media
path 205. It will be obvious to those skilled in the art that in
other embodiments the left media path 230 can be shifted laterally
to the left of the input media path 205 and the media-guiding
rollers 180 can be oriented to divert the media sheet 210 into the
left media path 235. In other embodiments, different sets of
media-guiding rollers 180 that are oriented in different directions
to direct the media sheet 210 into a plurality of media paths at
different lateral positions. It will be obvious to one skilled in
the art that this same approach can be extended to direct the media
sheet 210 into more than two media paths.
[0090] FIG. 19 shows an exemplary embodiment of a web-guiding
system 300 that includes a media-guiding system 78 as described
earlier, together with an air shoe. The air shoe includes a fixed
web-guiding structure 305 having a convex exterior surface 310. The
fixed web-guiding structure 305 is "fixed" in the sense that it
doesn't rotate or move with a surface speed that corresponds to the
surface speed of the web of receiver media. The fixed web-guiding
structure 305 being "fixed" is not intended to indicate that
orientation of the fixed web-guiding structure 305 cannot be
adjusted, either actively or passively, to align the fixed
web-guiding structure 305 relative to the transport path of the
receiver media 10. In the illustrated embodiment first side 15 of
the receiver media 10 faces the exterior surface 310 of the fixed
web-guiding structure 305, while second side 16 faces away from the
fixed web-guiding structure 305.
[0091] A pattern of air holes 315 is formed through the exterior
surface 310 of the fixed web-guiding structure 305, through which
air 325 supplied by an air source 320 can flow. As the web of
receiver media 10 travels around the fixed web-guiding structure
305, the flow of air 325 through the air holes 315 serves as an air
bearing lifting the web of receiver media 10 away from the fixed
web-guiding structure 305 such that first side 15 of the web of
receiver media 10 is substantially not in contact with the fixed
web-guiding structure 305. Within the context of the present
disclosure, "substantially not in contact" means that the receiver
media 10 contacts less than 5% of the exterior surface 310 of the
fixed web-guiding structure 305 that is adjacent to the receiver
media 10. (The fixed web-guiding structure 305 is sometimes
referred to in the art as an "air shoe" or an "air bearing
structure.")
[0092] As the web of receiver media 10 is supported by the air 325
so that there is minimal contact between the receiver media 10 and
the exterior surface 310 of the fixed web-guiding structure 305,
the receiver media 10 has minimal friction with the fixed
web-guiding structure 305. As a result, the receiver media 10 can
pass over the fixed web-guiding structure 305 without scuffing the
receiver media 10. Furthermore, the transverse bending of the web
of receiver media 10 as it goes around the fixed web-guiding
structure 305 tends to flatten the web of receiver media 10. The
lack of angular constraint on the receiver media 10 allows the
receiver media 10 to spread laterally to enable the flattening of
the web. The fixed web-guiding structure 305 can therefore
accommodate large wrap angles of the receiver media 10 without
wrinkling.
[0093] Because the receiver media 10 has minimal friction with the
fixed web-guiding structure 305, it provides little or no lateral
constraint to impede the lateral (i.e., cross-track) movement of
the web of receiver media 10. Therefore, while the low friction is
beneficial for inhibiting the formation of wrinkles, it has the
detrimental effect of allowing the print media to drift in the
cross-track direction 7. The media-guiding system 78, including
media-guiding roller 180 and air source 86, is used to provide a
lateral constraint on the receiver media 10 by placing it in close
proximity to the fixed web-guiding structure 305 to inhibit
cross-track drift or wander of the receiver media 10.
[0094] FIG. 20A shows a cross-section (taken in the cross-track
direction 7) of a prior art concave media-guiding roller 370. Such
concave media-guiding rollers 370 are known in the art to produce a
spreading force on the web of receiver media 10 is it moves past
the concave media-guiding roller 370. However, it has been found
that in certain situations, such as when the media-guiding roller
370 has a large amount of concavity and a small wrap angle, that a
central portion 375 of the receiver media 10 fails to make contact
with the exterior surface 373 of the concave media-guiding roller
370, leaving a reduced contacting portion 377. This can have the
undesirable effect of limiting the amount of media spreading
provided by the concave media-guiding roller 370. Inventors have
found that this problem can be overcome, or reduced in magnitude,
by using an embodiment of the invention.
[0095] FIG. 20B shows a cross-section (taken in the cross-track
direction 7) of a concave media-guiding roller 380 in accordance
with an embodiment of the present invention. In this configuration,
one or more grooves 384 are formed in the central portion 375 of
the exterior surface 383 of the concave media-guiding roller 380.
As was discussed earlier with respect to FIG. 5, an air source 86
(not shown in FIG. 20B) is positioned to direct an airflow 90 (not
shown in FIG. 20B) into the one or more grooves 384, the airflow 90
being directed between the first side 15 of the receiver media 10
and the exterior surface 383 of the concave media-guiding roller
380. This produces a Bernoulli force F on the central portion 375
of the receiver media 10 to deflect the central portion 375 of
receiver media 10 toward the concave media-guiding roller 380. This
results in an increased contacting portion 377 of the receiver
media 10 being in contact with the exterior surface 383 of the
concave media-guiding roller, when compared to the conventional
concave media-guiding roller 370 shown in FIG. 20A. As a result,
using a grooved concave media-guiding roller 380 in accordance with
the invention can increase the spreading effect provided to the
receiver media 10.
[0096] It will be obvious to one skilled in the art that in
addition to guiding receiver media 10 through a printing system
100, the media guiding systems of the present invention can also be
used to guide other types of media in other types of media
transport systems. For example, the present invention can also be
used to move various kinds of substrates through other types of
systems such as media coating systems, or systems for performing
various media finishing operations (e.g., slitting, folding or
binding).
[0097] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
PARTS LIST
[0098] 2 roller [0099] 3 receiver media [0100] 4 in-track direction
[0101] 5 flute [0102] 7 cross-track direction [0103] 8 contact
surface [0104] 9 exit direction [0105] 10 receiver media [0106] 11
source roll [0107] 12 take-up roll [0108] 15 first side [0109] 16
second side [0110] 20a printhead [0111] 20b printhead [0112] 20c
printhead [0113] 20d printhead [0114] 21 print line [0115] 22 print
line [0116] 25a printhead [0117] 25b printhead [0118] 30
web-guiding system [0119] 31 print line roller [0120] 32 print line
roller [0121] 40 dryer [0122] 41 dryer roller [0123] 45 quality
control sensor [0124] 50 printing module [0125] 51 first zone
[0126] 52 second zone [0127] 55 printing module [0128] 60 turnover
mechanism [0129] 65 printing module [0130] 66 web-guiding structure
[0131] 70 media-guiding roller [0132] 72 rotation direction [0133]
74 air cushion [0134] 76 entrained airflow [0135] 78 media-guiding
system [0136] 79 media-guiding system [0137] 80 media-guiding
roller [0138] 81 roller axis [0139] 82 rotation direction [0140] 83
exterior surface [0141] 84 groove [0142] 85 airflow guide [0143] 86
air source [0144] 88 air [0145] 89 openings [0146] 90 airflow
[0147] 91 plenum [0148] 92 constriction [0149] 93 pivot arm [0150]
94 actuator [0151] 95 steering controller [0152] 96 media edge
detector [0153] 97 stepper motor [0154] 98 rotation axis [0155] 99
frame [0156] 100 printing system [0157] 110 printing system [0158]
170 media-guiding system [0159] 171 media-guiding system [0160] 172
media-guiding system [0161] 173 media-guiding system [0162] 174
media-guiding system [0163] 175 media-guiding system [0164] 180
media-guiding roller [0165] 182 spring [0166] 184 edge stop [0167]
185 flute detection system [0168] 195 controller [0169] 200
sheet-diverter system [0170] 201 sheet-diverter system [0171] 202
sheet-diverter system [0172] 205 input media path [0173] 210 media
sheet [0174] 212 leading edge [0175] 215 media guide [0176] 220
upper media path [0177] 225 lower media path [0178] 230 left media
path [0179] 235 right media path [0180] 240 transfer position
[0181] 245 media diversion path [0182] 250 shifted position [0183]
260 roller assembly [0184] 261 roller assembly [0185] 280
media-guiding roller [0186] 281 roller axis [0187] 282 rotation
direction [0188] 283 exterior surface [0189] 284 groove [0190] 286
air source [0191] 290 airflow [0192] 292 constriction [0193] 295
controller [0194] 300 web-guiding system [0195] 305 fixed
web-guiding structure [0196] 310 exterior surface [0197] 315 air
holes [0198] 320 air source [0199] 325 air [0200] 370 concave
media-guiding roller [0201] 373 exterior surface [0202] 375 central
portion [0203] 377 contacting portion [0204] 380 concave
media-guiding roller [0205] 383 exterior surface [0206] 384 groove
[0207] d.sub.a airflow depth [0208] d.sub.g groove depth [0209] F
Bernoulli force [0210] w.sub.g groove width [0211] .alpha. wrap
angle
* * * * *