U.S. patent application number 13/040732 was filed with the patent office on 2012-09-06 for web media moving method.
Invention is credited to Randy E. Armbruster, Harsha S. Bulathsinghalage, John L. Hryhorenko, W. Charles Kasiske, JR., Michael J. Piatt.
Application Number | 20120223117 13/040732 |
Document ID | / |
Family ID | 46752692 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120223117 |
Kind Code |
A1 |
Kasiske, JR.; W. Charles ;
et al. |
September 6, 2012 |
WEB MEDIA MOVING METHOD
Abstract
A method of moving a continuous web of print media includes
providing a roller having an axis of rotation. The roller includes
a pattern of recesses and ridges positioned along the axis of
rotation of the roller. A second section of the roller is located
between a first section of the roller and a third section of the
roller as viewed along the axis of rotation. The roller includes a
profile as viewed along the axis of rotation in which the diameter
of the ridges located in the first section of the roller and the
diameter of ridges located in the third section of the roller are
greater than the diameter of the ridges located in the second
section of the roller. A web of print media is caused to contact
and wrap around a portion of the roller as the web of print media
moves past the roller.
Inventors: |
Kasiske, JR.; W. Charles;
(Penfield, NY) ; Piatt; Michael J.; (Dayton,
OH) ; Bulathsinghalage; Harsha S.; (Miamisburg,
OH) ; Hryhorenko; John L.; (Webster, NY) ;
Armbruster; Randy E.; (Rochester, NY) |
Family ID: |
46752692 |
Appl. No.: |
13/040732 |
Filed: |
March 4, 2011 |
Current U.S.
Class: |
226/1 |
Current CPC
Class: |
B65H 27/00 20130101;
B65H 2404/1313 20130101; B65H 2404/13161 20130101 |
Class at
Publication: |
226/1 |
International
Class: |
B65H 20/02 20060101
B65H020/02 |
Claims
1. A method of moving a continuous web of print media comprising:
providing a roller having an axis of rotation, the roller including
a pattern of recesses and ridges positioned along the axis of
rotation of the roller, the roller including a first section, a
second section, and a third section, the second section being
located between the first section and the third section as viewed
along the axis of rotation, the roller including a profile as
viewed along the axis of rotation in which the diameter of the
ridges located in the first section of the roller and the diameter
of ridges located in the third section of the roller are greater
than the diameter of the ridges located in the second section of
the roller; and causing the web of print media to contact and wrap
around a portion of the roller as the web of print media moves past
the roller.
2. The method of claim 1, wherein causing the web of print media to
contact and wrap around a portion of the roller as the web of print
media moves past the roller further comprises: providing a first
nip roller positioned to engage a first ridge of the ridges of the
roller and a second nip roller positioned to engage a second ridge
of the ridges of the roller; causing the web of print media to pass
between the first nip roller and the first ridge and to pass
between the second nip roller and the second ridge; and driving the
roller.
3. The method of claim 1, wherein causing the web of print media to
contact and wrap around a portion of the roller as the web of print
media moves past the roller further comprises: providing the roller
that freely rotates about its axis of rotation; and moving the web
of print media past the roller using a print media driving
mechanism.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Reference is made to commonly-assigned, U.S. patent
application Ser. No. ______ (Docket K000157), entitled "WEB MEDIA
MOVING APPARATUS", Ser. No. ______ (Docket K000159), entitled
"PRINTING SYSTEM INCLUDING WEB MEDIA MOVING APPARATUS", and Ser.
No. ______ (Docket K000160), entitled PRINTING METHOD INCLUDING WEB
MEDIA MOVING APPARATUS", all filed concurrently herewith.
FIELD OF THE INVENTION
[0002] This invention relates generally to a printing system for
printing on a web of print media, and in particular to an apparatus
for moving the web of print media through the printing system.
BACKGROUND OF THE INVENTION
[0003] Some digital printing systems and processes, for example,
inkjet printing systems and processes introduce significant
moisture content during operation, particularly when the system is
used to print multiple colors on a print media. Due to its moisture
content, the print media expands and contracts in a non-isotropic
manner often with significant hysteresis. The continual change of
dimensional characteristics of the print media often adversely
affects image quality. Although drying is used to remove moisture
from the print media, drying too frequently, for example, after
printing each color, also causes changes in the dimensional
characteristics of the print media that often adversely affects
image quality.
[0004] During an inkjet printing process, as the print media
absorbs the water-based inks applied to it, the print media desires
to expand. When the direction of expansion is in a direction that
is perpendicular to the direction of media travel, it is often
referred to as expansion in the cross-track direction. For example,
when the print media wraps around a roller of an inkjet printing
system, the outer, typically unprinted, edges of the print media
remain attached to the roller although the remaining typically
printed portions of the print media expand outwardly. The outward
expansion, commonly referred to as buckling, of the print media in
the cross-track direction between the firmly attached outer edges
of the print media creates lengthwise ripples or wrinkles in the
print media. Wrinkling of the print media during the printing
process often leads to permanent creases forming in the print media
which ultimately affects image quality.
[0005] As such, there is an ongoing need to provide digital
printing systems and processes with the ability to effectively
handle print media expansion associated with the absorption of
water by the print media.
SUMMARY OF THE INVENTION
[0006] According to an aspect of the invention, a method of moving
a continuous web of print media includes providing a roller having
an axis of rotation. The roller includes a pattern of recesses and
ridges positioned along the axis of rotation of the roller. A
second section of the roller is located between a first section of
the roller and a third section of the roller as viewed along the
axis of rotation. The roller includes a profile as viewed along the
axis of rotation in which the diameter of the ridges located in the
first section of the roller and the diameter of ridges located in
the third section of the roller are greater than the diameter of
the ridges located in the second section of the roller. A web of
print media is caused to contact and wrap around a portion of the
roller as the web of print media moves past the roller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] In the detailed description of the example embodiments of
the invention presented below, reference is made to the
accompanying drawings, in which:
[0008] FIG. 1 is a schematic side view of a digital printing system
according to an example embodiment of the present invention;
[0009] FIG. 2 is an enlarged schematic side view of media transport
components of the digital printing system shown in FIG. 1;
[0010] FIG. 3 is a schematic side view of a large-scale two-sided
digital printing system according to another example embodiment of
the present invention;
[0011] FIG. 4 is a schematic side view of a digital printing system
according to another example embodiment of the present
invention;
[0012] FIG. 5 is a schematic side view of an example embodiment of
the present invention;
[0013] FIG. 6 is a schematic side view of another example
embodiment of the present invention;
[0014] FIG. 7 is a schematic side view of another example
embodiment of the present invention;
[0015] FIG. 8 is a schematic side view of another example
embodiment of the present invention; and
[0016] FIG. 9 is a schematic side view of another example
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present description will be directed in particular to
elements forming part of, or cooperating more directly with,
apparatus in accordance with the present invention. It is to be
understood that elements not specifically shown or described 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.
[0018] The example embodiments of the present invention are
illustrated schematically and not to scale for the sake of clarity.
One of the ordinary skills 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.
[0019] In the context of the present disclosure, the term
"continuous web of print media" relates to a print media that is in
the form of a continuous strip of media as it passes through the
printing system from an entrance to an exit thereof. The continuous
web of print media itself serves as the receiving print medium to
which one or more printing ink or inks or other coating liquids are
applied in non-contact fashion. This is distinguished from various
types of "continuous webs" or "belts" that are actually transport
system components rather than receiving print media and that are
typically used to transport a cut sheet medium in an
electrophotographic or other printing system. The terms "upstream"
and "downstream" are terms of art referring to relative positions
along the transport path of a moving web; points on the web move
from upstream to downstream.
[0020] Generally described, an apparatus and method of moving a web
of print media includes a roller that rotates about an axis of
rotation as the print media makes contact with and wraps around a
portion of the roller as the print media moves past the roller. The
roller includes a pattern of recesses and ridges positioned along
the axis of rotation that help compensate for cross track expansion
of the print media caused by the absorption of water-based ink that
is applied to the print media in the print zone. The recesses and
ridges also help to reduce the likelihood of the print media
wrinkling as the print media wraps around roller and moves through
printing system.
[0021] The printing system and method including the web moving
apparatus are particularly well suited for printing devices that
provide non-contact application of ink, typically water based ink,
or other colorant onto a continuously moving web of print media.
The printhead of the printing system selectively moistens at least
some portion of the media as it courses through the printing
system, but without the need to make contact with the print
media.
[0022] Example embodiments of the print media web moving apparatus
are described below with reference to FIGS. 5-8. Example
embodiments of printing systems including one or plurality of print
media web moving apparatus are described below with reference to
FIGS. 1-4. When included in one of the printing systems described
with reference to FIG. 2 or 3, print media web moving apparatus is
typically located in one or both of roller positions G or M. When
included in the printing system described with reference to FIG. 4,
print media web moving apparatus is typically located in roller
position M.
[0023] The digital printing system can also include components for
drying or curing of the printing fluid on the media; for inspection
of the media, for example, to monitor and control print quality;
and various other functions. The digital printing system receives
the print media from a media source, and after acting on the print
media conveys it to a media receiving unit. The print media is
maintained under tension as it passes through the digital printing
system, but it is not under tension as it is received from the
media source.
[0024] The printing systems described with reference to FIGS. 1-4
include features and principles of exact constraint for
transporting continuously moving web print media past one or more
digital printheads, such as inkjet printheads. The apparatus for
moving a web of print media, however, works equally well in other
types of print media transport systems.
[0025] Referring to the schematic side view of FIG. 1, there is
shown a digital printing system 10 for continuous web printing
according to one embodiment. A first module 20 and a second module
40 are provided for guiding continuous web media that originates
from a source roller 12. Following an initial slack loop 52, the
media that is fed from source roller 12 is then directed through
digital printing system 10, past one or more digital printheads 16
and supporting printing system 10 components. First module 20 has a
support structure, shown in more detail subsequently, that includes
a cross-track positioning mechanism 22 for positioning the
continuously moving web of print media in the cross-track
direction, that is, orthogonal to the direction of travel and in
the plane of travel. In one embodiment, cross-track positioning
mechanism 22 is an edge guide for registering an edge of the moving
media. A tensioning mechanism 24, affixed to the support structure
of first module 20, includes a structure that sets the tension of
the print media.
[0026] Downstream from first module 20 along the path of the
continuous web media, second module 40 also has a support
structure, similar to the support structure for first module 20.
Affixed to the support structure of either or both the first or
second module 20 or 40 is a kinematic connection mechanism that
maintains the kinematic dynamics of the continuous web of print
media in traveling from the first module 20 into the second module
40. Also affixed to the support structure of either the first or
second module 20 or 40 are one or more angular constraint
structures 26 for setting an angular trajectory of the web
media.
[0027] Still referring to FIG. 1, printing system 10 optionally
also includes a turnover mechanism 30 that is configured to turn
the media over, flipping it backside-up in order to print on the
reverse side. The print media then leaves the digital printing
system 10 and travels to a media receiving unit, for example, a
take-up roll 18. A take-up roll 18 is then formed, rewound from the
printed web media. The digital printing system can include a number
of other components, including multiple print heads and dryers, for
example, as described in more detail subsequently. Other examples
of system components include web cleaners, web tension sensors, and
quality control sensors.
[0028] A support structure 28 provides a supporting frame for
mounting components within module 20. Similarly, a support
structure 48 provides a supporting frame for mounting components
within module 40. A continuous web of print media 60 moves through
printing system 10 beginning at the source roller 12 and ending at
the take-up roll 18.
[0029] The schematic side view diagram of FIG. 2 shows, at enlarged
scale from that of FIG. 1, the media routing path through modules
20 and 40 in one embodiment. Within each module 20 and 40, in a
print zone 54, each print head 16 is followed by a dryer 14.
[0030] Table 1 that follows identifies the lettered components used
for web media transport and shown in FIG. 2. An edge guide in which
the media is pushed laterally so that an edge of the media contacts
a stop is provided at A. The slack web entering the edge guide
shifts the print media laterally without interference and without
overconstraining the print media. An S-wrap device SW provides
stationary curved surfaces over which the continuous web slides
during transport. As the paper is pulled over these surfaces the
friction of the paper across these surfaces produces tension in the
print media. In one embodiment, this device helps to adjust the
positional relationship between surfaces, to control the angle of
wrap and adjust web tension.
TABLE-US-00001 TABLE 1 Roller Listing for FIG. 2 Media Handling
Component Type of Component A Lateral constraint (edge guide)
SW-S-Wrap Zero constraint (non-rotating support), Tensioning B
Angular constraint (in-feed drive roller) C Zero constraint
(Castered and Gimbaled Roller) D* Angular constraint with hinge
(Gimbaled Roller) E Angular constraint with hinge (Gimbaled Roller)
F Angular constraint (Fixed Roller) G Zero constraint (Castered and
Gimbaled Roller) H Angular constraint with hinge (Gimbaled Roller)
TB-TURNOVER Discussed in more detail below I Zero constraint
(Castered and Gimbaled Roller) J* Angular constraint with hinge
(Gimbaled Roller) K Angular constraint with hinge (Gimbaled Roller)
L Angular constraint (Fixed Roller) M Zero constraint (Castered and
Gimbaled Roller) N Angular constraint (out-feed drive roller) O
Zero constraint (Castered and Gimbaled Roller) P Angular constraint
with hinge (Gimbaled Roller) Note: Asterisk (*) indicates locations
of load cells.
[0031] The first angular constraint is provided by in-feed drive
roller B. This is a fixed roller that cooperates with a drive
roller in the turnover section and with an out-feed drive roller N
in second module 40 in order to move the web through the printing
system with suitable tension in the movement direction (from left
to right as shown in FIG. 2). The tension provided by the preceding
S-wrap serves to hold the paper against the in-feed drive roll so
that a nip roller is not required at the drive roller. Angular
constraints at subsequent locations downstream along the web are
often provided by rollers that are gimbaled so as not to impose an
angular constraint on the next downstream web span.
[0032] There is a single lateral constraint mechanism used at A.
Here, at the beginning of the media path, a single edge guide
provides lateral constraint that is sufficient for registering the
continuous web of print media along the media path. It is
significant that only one lateral constraint is actively applied
throughout the media path, here, as an edge guide. However, given
this lateral constraint and the following angular constraint, the
lateral constraint for each subsequent web span is fixed. In one
embodiment, a gentle additional force is applied along the
cross-track direction as an aid for urging the media edge against
the edge guide at A. This force is often referred to as a nesting
force as the force helps cause the edge of the media to nest
alongside the edge guide.
[0033] Angular constraints, rollers B, D, E, F, H, J, K, L, N, P,
are Included in printing system 10. Each angular constraint sets
the angular trajectory of the web as it moves along. However, the
web is not otherwise steered in the embodiment shown.
[0034] Fixed rollers at F and L precede the printheads for each
module, providing the desired angular constraint to the web in the
print zone. These rollers provide a suitable location of mounting
an encoder for monitoring the motion of the media through the
printing system. Under the printheads, the print media is supported
by fixed non-rotating supports. These supports provide zero
constraint to the web.
[0035] Roller G is a castered and gimbaled roller providing zero
constraint. Castered and gimbaled rollers provide zero constraint
along the web path. These mechanisms are used, for example, near
the input to each module, making each module independent of angular
constraints from earlier mechanisms. Other types of mechanisms that
provide zero constraint include stationary curved surfaces or
castered rollers.
[0036] If the span between roller F and G is sufficiently long, the
continuous web can lack sufficient stiffness to cause castered
roller G to align properly with the web. In such cases, roller G
need not be castered. Because of the relative length to width ratio
of the media in the segment between F and G, the continuous web in
that segment is considered to be non-stiff, showing some degree of
compliance in the cross-track direction. As a result, an additional
constraint is included to exactly constrain that web segment. This
is accomplished by eliminating the caster from roller G. Axially
compliant rollers can alternately be used where cross-track
constraint is undesirable.
[0037] A digital printing system 50 shown schematically in FIG. 3
has a considerably longer print path than that shown in FIG. 3, but
provides the same overall sequence of angular constraints, with the
same overall series of gimbaled, castered, and fixed rollers. Table
2 lists the roller arrangement used with the system of FIG. 3 in
one embodiment. Brush bars, shown between rollers F and G and
between L and M in FIG. 3, are non-rotating surfaces and thus apply
no lateral or angular constraint forces.
TABLE-US-00002 TABLE 2 Roller Listing for FIG. 3 Media Handling
Component Type of Component A Lateral constraint (edge guide)
SW-S-Wrap Zero constraint (non-rotating support) B Angular
constraint (in-feed drive roller) C Zero constraint (Castered and
Gimbaled Roller) D* Angular constraint with hinge (Gimbaled Roller)
E Angular constraint with hinge (Gimbaled Roller) F Angular
constraint (Fixed Roller) G Angular constraint with hinge (Gimbaled
Roller) H Angular constraint with hinge (Gimbaled Roller)
TB-TURNOVER Discussed in more detail below I Zero constraint
(Castered and Gimbaled Roller) J* Angular constraint with hinge
(Gimbaled Roller) K Angular constraint with hinge (Gimbaled Roller)
L Angular constraint (Fixed Roller) M Angular constraint with hinge
(Gimbaled Roller) N Angular constraint (out-feed drive roller) O
Zero constraint (Castered and Gimbaled Roller) P Angular constraint
with hinge (Gimbaled Roller) Note: Asterisk (*) indicates locations
of load cells.
[0038] Turnover mechanism (TB) 30 is shown as part of second module
40. Turnover mechanism TB can optionally be configured as a
separate module, with its web media handling compatible with that
of second module 40. The position of turnover mechanism TB is
appropriately between print zones 54 for opposite sides of the
media.
[0039] Load cells are provided in order to sense web tension at one
or more points in the system. In the embodiments of FIGS. 2 (Table
1) and 3 (Table 2), load cells are provided at gimbaled rollers D
and J. Control logic for the respective digital printing system 50
monitors load cell signals at each location and, in response, makes
any needed adjustment in motor torque in order to maintain the
proper level of tension throughout the system. For the embodiments
of FIGS. 2 and 3, the pacing drive component of the printing
apparatus is the turnover module TB. There are two tension-setting
mechanisms, one preceding and one following turnover module TB. On
the input side, load cell signals at roller D indicate tension of
the web preceding turnover module TB; similarly, load cell signals
at roller J indicate web tension on the output side, between
turnover module TB and take-up roll 18. Control logic for the
appropriate in- and out-feed driver rollers at B and N,
respectively, can be provided by an external computer or processor,
not shown in the figures of this application. Optionally, an
on-board control logic processor 90, such as a dedicated
microprocessor or other logic circuit, is provided for maintaining
control of web tension within each tension-setting mechanism and
for controlling other machine operation and operator interface
functions.
[0040] The tension in a module preceding the turn bar and a module
following the turnover module TB can be independently controlled
relative to each other further enhancing the flexibility of the
printing system. To accomplish this, a drive motor is included in
the turnover module TB. Alternatively, a drive motor is
appropriately located along the web path so that tension within one
module is independently controlled relative to tension in another
module.
[0041] The configurations of FIGS. 1 and 2 were described as
including two modules 20 and 40. In the FIG. 1 configuration, each
module provided a complete printing apparatus. However, the
"modular" concept need not be restricted to apply to complete
printers. For example, the configuration of FIG. 3 is considered as
formed of as many as seven modules.
[0042] An entrance module 70 is the first module in sequence,
following the media supply roll, as was shown earlier with
reference to FIG. 1. Entrance module 70 provides the edge guide A
that positions the media in the cross-track direction and provides
the S-wrap SW or other appropriate web tensioning mechanism. In the
embodiment of FIG. 3, entrance module 70 provides the in-feed drive
roller B that cooperates with SW and other downstream drive rollers
to maintain suitable tension along the web, as noted earlier.
Rollers C, D, and E are also part of entrance module 70 in the FIG.
3 embodiment.
[0043] A first printhead module 72 accepts the web media from
entrance module 70, with the given edge constraint, and applies an
angular constraint with fixed roller F. A series of stationary
brush bars or, optionally, minimum-wrap rollers then transport the
web along past a first series of printheads 16 with their
supporting dryers and other components. Here, because of the
considerable web length in the web segment beyond the angular
constraint provided by roller F (that is, the distance between
rollers F and G), that segment can exhibit flexibility in the cross
track direction which is an additional degree of freedom that needs
to be constrained. Eliminating the expected caster of roller G
provides the additional constraint needed in that span.
[0044] An end feed module 74 provides an angular constraint to the
incoming media from printhead module 72 by gimbaled roller H.
Turnover module TB accepts the incoming media from end feed module
74 and provides an angular constraint with its drive roller, as
described previously.
[0045] A forward feed module 76 provides a web span corresponding
to each of its gimbaled rollers J and K. These rollers again
provide angular constraint only; the lateral constraint for web
spans in module 76 is obtained from the edge of the incoming media
itself.
[0046] A second printhead module 78 accepts the web media from
forward feed module 76, with the given edge constraint, and applies
an angular constraint with fixed roller L. A series of stationary
brush bars or, optionally, minimum-wrap rollers then feed the web
along past a second series of printheads 16 with their supporting
dryers and other components. Here again, because of considerable
web length in the web segment (that is, extending the distance
between rollers L and M), that segment will exhibit flexibility in
the cross track direction which is an additional degree of freedom
that needs to be constrained, eliminating the expected caster of
roller M provides the additional constraint needed in that span.
When overhang is present in the web span (that is, extending the
distance between rollers L and M), exact constraint principles are
sometimes difficult to apply successfully. Gimbaled roller M
provides additional constraint over this long web span.
[0047] An out feed module 80 provides an out-feed drive roller N
that serves as angular constraint for the incoming web and
cooperates with other drive rollers and sensors along the web media
path that maintain the desired web peed and tension. Optional
rollers O and P (not shown in FIG. 3) are also provided for
directing the printed web media to an external accumulator or
take-up roll.
[0048] Each module in this sequence provides a support structure
and an input and an output interface for kinematic connection with
upstream or downstream modules. With the exception of the first
module in sequence, which provides the edge guide at A, each module
uses one edge of the incoming web media as its "given" lateral
constraint. The module then provides the needed angular constraint
for the incoming media in order to provide the needed exact
constraint or kinematic connection of the web media transport. It
can be seen from this example that a number of modules can be
linked together. For example, an additional module can alternately
be added between any other of these modules in order to provide a
useful function for the printing process.
[0049] Module function is adaptable to the configuration of the
complete printing system. In many cases, rollers and components are
interchangeable, including rollers at the interface between
modules, moved from one module to another depending on the printer
configuration. Frames and other support structures for the
different modules either use a standard design and dimensions or
are designed differently according to the contemplated application.
This also helps to simplify upgrade situations.
[0050] There are a number of ways to track web position in order to
locate and position inkjet dots or other marking that is made on
the media. A variety of encoding and sensing devices are used for
this purpose along with the associated timing and synchronization
logic, provided by control logic processor 90 or by some other
dedicated internal or external processor or computer workstation.
Such encoders or sensing devices are typically placed just upstream
of the print zone containing the one or more printheads, and are
preferably placed on a fixed roller so as to avoid interfering with
self aligning characteristic of castered or gimbaled rollers.
[0051] Sometimes an active steering mechanism is used within a web
span, for example, when the web span length of an overhang exceeds
its width, so that the web no longer has sufficient mechanical
stiffness for exact constraint techniques. This happens, for
example, where there is considerable overhang along the web span,
that is, length of the web extending beyond the angular constraint
for the span. This is the case for modules 72 and 78 in the
embodiment described with respect to FIG. 3. In such a case, a
castered roller in the overhang section of the web often no longer
behave as a zero constraint, since some amount of lateral force
from the web is needed in order to align the castered roller
mechanism to the angle of the web span. This under-constraint
condition, due to length of the overhang along this lengthy web
span, is corrected by application of an additional constraint.
[0052] Kinematic connection between modules 20 and 40 follows the
same basic principles that are used for exact constraint within
each web span. That is, cross-track or edge alignment is taken from
the preceding module. Any attempt to re-register the media edge as
it enters the next module would cause an overconstraint condition.
Rather than attempting to steer the continuously moving media
through a rigid and possibly over-constrained transport system, the
media transport components self-align to the media, thereby
providing acceptable registration at high transport speeds and
reducing the likelihood of damage to the media or misregistration
of applied ink or other colorant to the media.
[0053] Where multiple modules are used, as was described with
reference to the embodiment shown in FIG. 3, the system should
include a master drive roller that is in control of web transport
speed. Often multiple drive rollers are used and help provide
proper tension in the web transport (x) direction, such as by
applying suitable levels of torque, for example. In one embodiment,
the turnover TB module drive roller acts as the master drive
roller. The in-feed drive roller at B in module 20 adjusts its
torque according to a load sensing mechanism or load cell that
senses web tension between the drive and in-feed rollers.
Similarly, out-feed drive roller N is controlled in order to
maintain a desired web tension within second module 40.
[0054] Referring to FIG. 4, the web position in the span containing
the printheads 16 and dryers 14 is defined by a lateral constraint
in the form of an edge guide F located immediately before the print
zone and an angular constraint, non-pivoting roller M, located
immediately after the print zone. With the media under tension as
it wraps around the shoe of the edge guide F, the shoe is free to
pivot. This ensures that the media has uniform tension across its
width in the print zone. In this embodiment, the shoe rotates about
an axis at the center of the shoe and perpendicular to the plane of
the web segment from F to M. This rotation orientation reduces
variation in spacing between the media and printheads 16 as shoe F
pivots. When the media is not under tension as it passes over the
edge guide, the edge guide shoe need not be free to pivot.
[0055] This embodiment also has an edge guide A and a non-pivoting
drive roller B that establish an initial path for the media in the
first span of the media entering the printing system. The
combination of the castered and gimbaled rollers C and E and the
gimbaled roller D removes an overconstraint condition that would
have existed between the first media span and the span across the
print zone. Edge guide A helps to ensure that the only minor
shifting of the lateral position of the web is needed at edge guide
F. This allows the bias force needed to shift the media to the edge
stop to be kept to a minimum. With the media under tension as it
passes edge guide F, the required bias force to shift the media is
greater than it would be if the media were not under tension. The
constraints provided by each roller are listed in table 3.
TABLE-US-00003 TABLE 3 Roller Listing for FIG. 4 Media Handling
Component Type of Component A Lateral Constraint (Edge Guide)
SW-S-Wrap Zero Constraint (Non-Rotating Support), Tensioning B
Angular Constraint (In-Feed Drive Roller) C Zero Constraint
(Castered and Gimbaled Roller) D* Angular Constraint with Hinge
(Gimbaled Roller) E Zero Constraint (Castered and Gimbaled Roller)
F Lateral Constraint (Edge Guide) Brush Bars Zero Constraint
(Non-Rotating Support) M Angular Constraint (Non-Pivoting Roller) N
Zero Constraint (Castered and Gimbaled Roller) O Angular Constraint
(Out-Feed Drive Roller) P Zero Constraint (Castered and Gimbaled
Roller) Q Angular Constraint with Hinge (Gimbaled Roller) Note:
Asterisk (*) Indicates Locations Of Load Cells.
[0056] In the embodiment of FIG. 4, the printing system doesn't
comprise multiple modules. The media transport components are
secured to a single support structure. Through the use of rollers
that align to the web, it is not necessary to precisely align the
rollers to each other in this system. This greatly reduces the
assembly costs for the system. As precise alignments are not
required, the support structure to which the various rollers and
web guides are mounted doesn't need to be as stiff as prior art
frames. This allows the mass of the support structure to be greatly
reduced which reduces shipping and setup costs.
[0057] As described above, continuous web media transport within
and between one, two three, or more modules is accomplished by
applying exact constraint techniques. This flexibility allows a web
transport arrangement that provides acceptable registration and
repeatable performance at high speeds commensurate with the
requirements of high-speed color inkjet printing. As has been
shown, multiple modules can be integrated to form a printing
system, without the requirement for painstaking alignment of
rollers or other media handling components at the interface between
two modules.
[0058] It has been found that web transports systems as described
above maintain effective control of the print media in the context
of a digital print system where the selected portions of the print
media are moistened in the printing process. This is true even when
the print media is prone to expanding in length and width and to
becoming less stiff when it is moistened, such as for cellulose
based print media moistened by a water based ink. This enables the
individual color planes of a multi-colored document to be printed
with acceptable registration to each other.
[0059] The digital printing systems having one or more printheads
that selectively moisten at least a portion of the print media as
described above include a media transport system that serves as a
support structure to guide the continuous web of print media. The
support structure includes an edge guide or other mechanism that
positions the print media in the cross track direction. This first
mechanism is located upstream of the printheads of the digital
printing system. The print media is pulled through the digital
printing system by a driven roller that is located downstream of
the printheads. The systems also include a mechanism located
upstream of printheads of the printing system for establishing and
setting the tension of the print media. Typically it is also
located downstream of the first mechanism used for positioning the
print media in the cross track direction. The transport system also
includes a third mechanism to set an angular trajectory of the
print media. This can be a fixed roller (for example, a
non-pivoting roller) or a second edge guide. The printing system
also includes a roller affixed to the support structure configured
to align to the print media being guided through the printing
system without necessarily being aligned to another roller located
upstream or downstream relative to the roller. The castered,
gimbaled or castered and gimbaled rollers serve in this manner.
[0060] As noted earlier, slack loops are not required between or
within modules. Slack loops can be appropriate where the continuous
web is initially fed from a supply roll or as it is re-wound onto a
take-up roll, as was described with reference to the printing
apparatus of FIG. 1.
[0061] This system is adaptable for a printing system of variable
size and facilitates straightforward reconfiguration of a system
without requiring precise adjustment and alignment of rollers and
related hardware when modules are combined. By using exact
constraint mechanisms, rollers can be mounted within the equipment
frame or structure using a reasonable amount of care in mechanical
placement and seating within the frame, but without the need to
individually align and adjust each roller along the path, as would
be necessary when using conventional paper guidance mechanisms.
That is, roller alignment with respect to either the media path or
another roller located upstream or downstream is not needed.
[0062] Referring to FIGS. 5-8, example embodiments of an apparatus
for moving the continuous web of print media 60 are shown. A roller
100, having an axis of rotation 102, includes a pattern of recesses
104 and ridges 106 positioned along the axis of rotation 102.
Roller 100 is divided into sections including a first section 108,
a second section 110, and a third section 112. The second section
110 is located between the first section 108 and the third section
112 when viewed along the axis of rotation 102. Roller 100 includes
a profile as viewed along the axis of rotation 102 that is
typically referred to as a concave profile. In this profile, the
diameter 114 of the ridges 106 located in the first section 108 of
the roller 100 and the diameter 116 of ridges 106 located in the
third section 112 of the roller 100 are greater than the diameter
118 of the ridges 106 located in the second section 110 of the
roller 100.
[0063] The concave profile of roller 100, created by ridges 106,
causes the print media 60 to contact different locations of roller
100 as the web of print media 60 wraps around a portion of roller
100. This allows causes roller 100 to provide lateral forces on the
web of print media 60 that spread (or stretch) the print media 60
in the cross track direction of the printing system 10 (to left and
to the right as shown in FIG. 5). This helps to compensate for
cross track expansion of the print media 60 caused by the
absorption of water-based ink that is applied to the print media 60
in print zone 54. The surface finish and coefficient of friction of
the ridges 106 of roller 100 can be selected to provide appropriate
friction between print media 60 and roller 100 for the level of
in-track tension, tension in the direction of print media travel,
and amount of wrap, referred to as wrap angle, of print media 60
around roller 100.
[0064] In contrast to a pattern of ridges and recesses that spiral
around and along a roller in a non-perpendicular fashion relative
to the axis of rotation of the roller, the edges 120, 122 of ridges
106 and the edges 124, 126 of recesses 104 wrap directly around
roller 100 in a perpendicular fashion relative to the axis of
rotation 102 of roller 100. This creates ridges 106 and recesses
104 of roller 100 that also extend (or wrap around) the
circumference of roller 100 in a perpendicular fashion relative to
the axis of rotation 102 roller 100. Ridges 106 and recesses 104
extend in periodic manner along the length 128 of roller 100.
Recesses 104 provide area for the expanded print media 60 to fit
into as the print media 60 wraps around roller 100. This reduces
the likelihood of the print media 60 wrinkling as the print media
60 wraps around roller 100 and moves through printing system 10.
Preferably, the combination of in-track web tension and the wrap
angle is sufficient to cause print media 60 to pull slightly into
the recesses 104 of roller 100. In some applications, the depth of
recesses 104 is sized so that the portions of the print media 60
pulled into the recesses 104 of roller 100 contact a lower surface
130 of roller 100 which helps minimize print media 60 distortion as
the print media is pulled into the recesses 104.
[0065] In FIG. 5, the pattern of recesses 104 and ridges 106
positioned along the axis of rotation 102 of roller 100 is an
alternating pattern of recesses 104 and ridges 106. The ridges 106
have a uniform width 142 as viewed along the axis of rotation 102
of roller 100. The diameter of each ridge 106 increases in a
stepwise manner as viewed from the second section 110 of roller 100
toward both the first section 108 of roller 100 and the third
section 112 of roller 100. Each recess 104 includes a surface 130
that is parallel to the axis of rotation 102 of roller 100. The
depth 132 of each recess varies when viewed from the second section
110 of roller 100 toward both the first section 108 of roller 100
and the third section 112 of roller 100. The surfaces 134 of ridges
106 are parallel to the axis of rotation 102 of roller 100
[0066] In FIG. 6, the pattern of recesses 104 and ridges 106
positioned along the axis of rotation 102 of roller 100 is an
alternating pattern of recesses 104 and ridges 106. The ridges 106
have a uniform width 142 as viewed along the axis of rotation 102
of roller 100. The diameter of each ridge 106 increases when viewed
from the second section 110 of roller 100 toward both the first
section 108 of roller 100 and the third section 112 of roller 100.
Each recess 104 includes a lower surface 130 that is parallel to
the axis of rotation 102 of roller 100. The depth 132 of each
recess varies when viewed from the second section 110 of roller 100
toward both the first section 108 of roller 100 and the third
section 112 of roller 100. The surfaces 134 of ridges 106 are
angled relative to the axis of rotation 102 of roller 100 and are
configured to create a radius of curvature 136 as viewed from a
plane perpendicular to the axis of rotation of the roller. The
radius of curvature 136 begins at the outside edge 138 of the first
section 108 of roller 100, extends through the section 110 of
roller 100, and ends at the outside edge 140 of the third section
112 of roller 100.
[0067] In FIG. 7, the pattern of recesses 104 and ridges 106
positioned along the axis of rotation 102 of roller 100 is an
alternating pattern of recesses 104 and ridges 106. The diameter of
each ridge 106 increases when viewed from the second section 110 of
roller 100 toward both the first section 108 of roller 100 and the
third section 112 of roller 100. Additionally, the width 142 of at
least a portion of ridges 106 located in the first section 108 of
roller 100 and the third section 112 of roller 100 is greater than
the width of ridges located in the second section 110 of roller
100. The increased width of the ribs toward each end of the roller
enhance the lateral forces to spread the print media, when compared
to rollers having uniform rib width along the length of the roller.
Each recess 104 includes a lower surface 130 that is parallel to
the axis of rotation 102 of roller 100. The depth 132 of each
recess varies when viewed from the second section 110 of roller 100
toward both the first section 108 of roller 100 and the third
section 112 of roller 100. The surfaces 134 of ridges 106 are
angled relative to the axis of rotation 102 of roller 100 and are
configured to create a radius of curvature 136 as viewed from a
plane perpendicular to the axis of rotation of the roller. The
radius of curvature 136 begins at the outside edge 138 of the first
section 108 of roller 100, extends through the section 110 of
roller 100, and ends at the outside edge 140 of the third section
112 of roller 100.
[0068] In FIG. 8, the pattern of recesses 104 and ridges 106
positioned along the axis of rotation 102 of roller 100 is an
alternating pattern of recesses 104 and ridges 106. The ridges 106
have a uniform width 142 as viewed along the axis of rotation 102
of roller 100. The diameter of each ridge 106 increases in a
stepwise manner as viewed from the second section 110 of roller 100
toward both the first section 108 of roller 100 and the third
section 112 of roller 100. Each ridge 106 includes rounded corners
144. These rounded corners reduce the stresses on print media
moving over the roller near the edges of the ridges. Each recess
104 includes a surface 130 that includes a radius of curvature 146
relative to the axis of rotation 102 of roller 100. The depth 132
of each recess varies when viewed from the second section 110 of
roller 100 toward both the first section 108 of roller 100 and the
third section 112 of roller 100. The surfaces 134 of ridges 106 are
parallel to the axis of rotation 102 of roller 100. The pattern of
ridges and recesses is symmetric about the center (represented by
centerline 150) of the roller, so that left side of the roller is a
mirror image of the right side of the roller as viewed in FIG.
8.
[0069] Although certain aspects of the example embodiments of the
web moving apparatus have been discussed with reference to
individual figures of FIGS. 5-8. It should be understood that these
aspects are interchangeable or combinable. For example, the width
142 of ridges 106 located in the first section 108 of roller 100
and the third section 112 of roller 100 can be greater than the
width ridges located in the second section if the roller in the
example embodiment described with reference to FIG. 5. The
embodiments described with reference to FIGS. 5-7 can have recess
104 that include a surface 130 that includes a radius of curvature
146 relative to the axis of rotation 102 of roller 100. The ridges
106 described in these embodiments can include rounded corners
144.
[0070] As shown in FIGS. 5-8, roller 100 is free to rotate about
its axis of rotation 102. Referring to FIG. 9, in other example
embodiment, roller 100 is a driven roller, for example, driven
directly by a motor 152 or by using another conventional roller
driving mechanism. A first nip roller 154 is positioned to engage a
first ridge 156 of the ridges 106 of roller 100 and a second nip
roller 158 is positioned to engage a second ridge 160 of the ridges
of the roller. Typically, the first ridge 156 is located in the
first section 108 of roller 100 and the second ridge 160 is located
in the third section 112 of roller 100 to help facilitate print
media movement and minimize potential wrinkling of the print media.
As shown in FIG. 9, first ridge 156 is a ridge located proximate to
a first edge 162 of print media and second ridge 160 is a ridge
located proximate to a second edge 164 of print media, as viewed in
a cross track direction. As described above, certain aspects of the
example embodiments of the web moving apparatus have been discussed
with reference to individual figures of FIGS. 5-9. It should be
understood that these aspects are interchangeable or
combinable.
[0071] As shown in FIGS. 5-9, the width 148 of each recess 104 of
roller 100 is uniform. In other example embodiments, the recess 104
width 148 can vary. Alternatively, the width 142 of ridges 106 as
viewed along the axis of rotation can vary. For example, the width
of the ridges located proximate to a first edge and a second edge
of print media, as viewed in a cross track direction, is different
when compared to the width of ridges located in other areas of the
print media. This is done so that the edges 162, 164 of the print
media 60 are in contact with a ridge 106 of roller 100. In
applications that contemplate moving print media 60 of various
widths, wider ridges 156, 160 are located proximate to the
anticipated edge 162, 164 locations for each of the anticipated
print media 60 widths.
[0072] Referring back to FIGS. 1-8, after roller 100 has been
provided, the web of print media 60 is caused to contact and wrap
around a portion of roller 100 as the web of print media 60 moves
past roller 100. Typically, this is accomplished by appropriately
positioning roller 100 and print media web 60 relative to each
other, for example, by locating roller 100 in one or both of roller
locations G or M as described above. When provided roller 100
freely rotates about its axis of rotation, movement of the web of
print media is accomplished using a print media driving mechanism,
for example, one of the driven rollers described above with
reference to FIGS. 1-4.
[0073] When roller 100 is a driven roller, the web of print media
60 is also caused to contact and wrap around a portion of roller
100 as the web of print media 60 moves past roller 100. After first
nip roller 154 is positioned to engage first ridge 156 of ridges
106 of roller 100 and second nip roller 158 is positioned to engage
second ridge 160 of ridges 106 of roller 100, the web of print
media 60 is caused to pass between first nip roller 154 and first
ridge 156 and to pass between second nip roller 158 and second
ridge 160. Typically, this is accomplished by appropriately
positioning roller 100, first nip roller 154, second nip roller
158, and print media web 60 relative to each other, for example, by
locating roller 100, first nip roller 154, and second nip roller
158, in one or both of roller locations G or M as described above.
Movement of the web of print media 60 is accomplished by driving
roller 100 using, for example, a motor or another conventional
roller driving mechanism.
[0074] One or more of printheads 16 ejects ink selectively moisten
at least a portion of the web of print media 60 as the web of print
media 60 is guided through printing system 10. Roller 100 is
positioned downstream from the printhead 16. An optionally included
dryer 14, positioned downstream from the printhead and upstream
from the roller, removes moisture from the print media 60 as the
print media 60 moves past dryer 14.
[0075] 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
[0076] 10. Printing system [0077] 12. Source roller [0078] 14.
Dryer [0079] 16. Digital printhead [0080] 18. Take-up roll [0081]
20. Module [0082] 22. Cross-track positioning mechanism [0083] 24.
Tensioning mechanism [0084] 26. Constraint structure [0085] 28.
Support structure [0086] 30. Turnover mechanism [0087] 40. Module
[0088] 48. Support structure [0089] 50. Digital printing system
[0090] 52. Slack loop [0091] 54. Print zone [0092] 60. Web of print
media [0093] 70. Entrance module [0094] 72. Printhead module [0095]
74. End feed module [0096] 76. Forward feed module [0097] 78.
Printhead module [0098] 80. Out-feed module [0099] 90. Control
logic processor [0100] 100. Roller [0101] 102. Axis of rotation
[0102] 104. Recesses [0103] 106. Ridges [0104] 108. First section
[0105] 110. Second section [0106] 112. Third section [0107] 120.
Edges [0108] 122. Edges [0109] 124. Edges [0110] 126. Edges [0111]
128. Length [0112] 130. Surface [0113] 132. Depth [0114] 134.
Surfaces [0115] 136. Curvature [0116] 138. Outside edge [0117] 140.
Outside edge [0118] 142. Uniform width [0119] 144. Rounded corners
[0120] 146. Curvature [0121] 148. Width [0122] 150. Centerline
[0123] 152. Motor [0124] 154. First nip roller [0125] 156. First
ridge [0126] 158. Second nip roller [0127] 160. Second ridge [0128]
162. First edge [0129] 164. Second edge [0130] A, B, C, D, E, F, G,
H, I, J, K, L, M, N, O, P. Rollers [0131] SW. S-wrap [0132] TB.
Turnover module
* * * * *