Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR STABILIZING A MOVING WEB
RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application Serial No. 61/155,583, filed on February 26, 2009, the
entirety of which is incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] Webs of material (including but not limited to tissue, towel, paper,
board, plastics, and polymers) are transported through spans that
typically have web stabilizers, such as shown in U.S. Patent 4,321,107.
The webs move at a relatively high speed through the spans and across
the stabilizers.
[0003] As the web moves across the flat surface of the stabilizers, the
side edges of the web tend to curl. Curling may increase the stresses
applied to the web, especially at the web edges. Curling may result in
non-uniform stretching of the web across the width of the web and
increase the risk of web tearing. The side edges most commonly curl
away from the stabilizers due to web tension, gravity, differences in
material properties, outside influences such as air currents and that the
material on the web ends is connected to other web material only on
one side of the web. There is a need for devices and methods to reduce
curling at the side edges of webs.
BRIEF DESCRIPTION OF THE INVENTION
[0004] To minimize web curling, a force is applied to the outside sheet
edge region of the stabilizer to draw the side edges of the web to the
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stabilizer. By drawing the side edges of the web to the stabilizer, the
edges of the web are kept in-line with other portions of the web moving
across the stabilizer. Minimizing curling of the side edges assists in
stabilizing the web, reduces stresses in the web material, reduces web
breaks and may improve characteristics of the web material because
the side ends are subjected to less stress and stretching.
[0005] The force applied to the web edge may be formed by air
movement along and away from the outside sheet edge region of the
surface of the stabilizer facing the web. For example, compressed air or
a vacuum (collectively referred to as "pressurized" air) may be applied
at or near the sheet edge region to draw air from between stabilizer
surface and the edge of the web to create a suction force between the
web and stabilizer pushing the edge of the web towards the stabilizer.
To create the suction force, air may be forced or drawn through a gap
adjacent the sheet edge and between the outside sheet edge region
and an air movement direction device. The gap is generally parallel to
and adjacent the side edge of the web. As the air flows through the
gap, a pressure drop forms at the web side edge that draws the side
edge towards the sheet edge region of the stabilizer.
[0006] To create the force applied to the side edge of the web, the air
movement over the sheet edge region is preferably in a direction flowing
away from the web, substantially perpendicular, e.g., 65 degrees to 125
degrees, to the web edge, and aligned, e.g., in a plane, with the
intended elevation of the web. In addition or alternatively, air movement
may be directed in other directions, including towards or away from the
stabilizer. The air flow should create a low pressure between the web
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and the sheet edge of the stabilizer such that the low pressure pulls the
side edges of the web towards the sheet edge.
[0007] The invention may be embodied as a web stabilizer comprising: a
surface adjacent a moving web, wherein the surface includes a sheet
edge region adjacent each side edge of the web, and a fluid moving
device mounted to or near the sheet edge region, wherein the fluid
moving device causes fluid to move adjacent the sheet edge region in a
direction moving away from the side edge of the web aligned with the
sheet region.
[0008] In another embodiment, the invention may be a web stabilizer
comprising: a surface adjacent a moving web, wherein the surface
includes a sheet edge region adjacent each side edge of the web; a gap
forming device mounted to or near the sheet edge region; a gap
adjacent the side edge of the web and formed between the gap forming
device and the surface, and a source of pressurized fluid positioned to
force a fluid through the gap in a direction away from the side edge of
the web.
[0009] The invention may be embodied as a method to reduce curl in a
side edge of a moving web comprising: moving the web along a surface
of a stabilizer; moving air away from a side edge of the web as the web
moves along the surface of the stabilizer; moving the edge of the web
towards the surface of the stabilizer by a force formed by the movement
of the air away from the side edge.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIGURE 1 is a schematic diagram showing in cross-section a
web stabilizer and a web moving below the stabilizer in a direction
perpendicular to the page of the figure. The figure shows a curl at the
side edges of the web.
[0011] FIGURE 2 is a schematic diagram showing in cross-section a
web stabilizer and a web moving below the stabilizer, wherein the side
edges of the web have curled and air (shown by arrows with dotted
lines) is flowing away from the sheet edge and through a gap.
[0012] FIGURE 3 is a schematic diagram showing in cross-section a
web stabilizer and a web moving below the stabilizer, wherein the side
edges of the web have been drawn to the sheet edge of the stabilizer by
the air flowing through a gap.
[0013] FIGURE 4A is a bottom view of the stabilizer showing the web
and air flowing in several possible directions away from the side edges
of the web.
[0014] FIGURE 4B is a schematic diagram showing in cross-section a
side of a web stabilizer and an apparatus for creating a force, e.g., an
air movement, adjacent and away from the edges of the web.
[0015] FIGURE 5 is a schematic diagram showing in cross-section a
web stabilizer and a web moving below the stabilizer, wherein recesses
or projections are formed in the stabilizer surface adjacent the side
edges of the web to supply and direct the air movement.
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[0016] FIGURE 6A is a schematic diagram showing in cross-section a
web stabilizer and a web moving below the stabilizer, wherein air
nozzles are arranged in the stabilizer adjacent and outside of the side
edges of the web.
[0017] FIGURE 6B is a schematic diagram showing in cross-section a
web stabilizer and a web moving below the stabilizer, wherein air
nozzles are arranged in the stabilizer adjacent and inside of the side
edges of the web.
[0018] FIGURE 7A is a schematic diagram showing in cross-section a
side of a web stabilizer and illustrating a Coanda effect as the air
movement through the gap with the stabilizer.
[0019] FIGURE 7B is a schematic diagram showing in cross-section a
side of a web stabilizer and air flowing through a gap where the air flows
from the air source in or near the gap.
[0020] FIGURE 8 illustrates an installation of a device to form a gap near
a side edge of the web and apply an air movement through the gap.
[0021] FIGURE 9 is a schematic diagram showing in cross section an air
knife, as an air movement device, adjacent a stabilizer and a web,
wherein only a portion of the stabilizer and the web are illustrated.
DETAILED DESCRIPTION OF THE INVENTION
[0022] FIGURES 1 and 2 are schematic cross-sectional diagrams of a
web stabilizer 1 and a web or sheet 4 (collectively referred to as a web)
moving below the stabilizer in a direction perpendicular to the page of
the figure. A moving fluid, preferably a gas such as air, is introduced
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along a strip, e.g., sheet edge region 16 of a bottom surface 17 of the
stabilizer, and just at or outside the edges 5 of the moving web 4. The
moving fluid, e.g. air, 9 creates a force that stabilizes the web edges 5
and reduces or eliminates curling of the edges 5. Figures 1 and 2 show
curled edges of the web. Reducing curling should reduce sheet breaks
and improve performance and the speed potential of the web machine,
which may be a tissue, paper, board or other web processing machine.
[0023] The stationary web stabilizer 1 may be a generally rectangular
device having a substantially flat bottom surface 17. The web 4 moves
at a high velocity, e.g., such as 4,000 to 7,000 feet per minute (1,200 to
2,100 meters per minute). The movement of the web causes the air
next to the web to move and particularly causes the air to move in a gap
between the web and stabilizer. Because of the movement air, there the
gap is at a lower static pressure as compared to the air on the opposite
side of the web. This pressure difference across opposite sides of the
web draws the web towards the bottom surface 17 of the stabilizer. The
center portion of the web 4 may be adjacent the bottom of the stabilizer.
The side edges 5 of the web may curl away from the sheet edge region
16 of the bottom 17 of the stabilizer. There is a desire to eliminate the
curling and force the side edge 5 into the same plane as the center
portion of the web 4.
[0024] Figure 3 illustrates a moving web 4 having side edges 5 that are
uncurled due to moving fluid, e.g., air streams, 9 moving away from the
side edges. To remove the curl of side edges 5 of the web 4, a moving
fluid 9, e.g., air, is directed away from the side edges 5 to generate a
force applied to the side edges. The force causes the side edges 5 of
the web to move towards the sheet edge region 16, which is a strip of
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the flat bottom surface 17 of the stabilizer adjacent the desired location
of the side edges 5 of the web. The force results from the movement of
the fluid, e.g., an air flow 9, away from the web edges 5 and along or
adjacent the sheet edge 16 of the bottom of the stabilizer. The term "air"
is used to refer to a moving fluid that is preferably pressurized
atmospheric air but may be other gases and liquids and includes using
a vacuum or other devices to impart a positive or negative pressure as
compared to atmospheric air pressure.
[0025] The air may flow through a gap 2 between an air movement or air
direction device 3, e.g., a hollow beam that may have air nozzles, that is
adjacent the sheet edge and slightly beyond the side edges of the web.
There may be an air movement or direction device 3 attached to the
bottom surface of the stabilizer such that an air gap 2 is formed
between the beam and bottom surface 17 of the stabilizer.
[0026] The moving fluid 9 is directed away from the edges 5 of the web 4
in a direction that is preferably perpendicular to the web movement. The
fluid may flow in other directions 11, such as shown in Figures 4A and
4B. The air flows generally directed away from the sheet edge region
16 and the side edges 5 of the web. The preferred method is directing
the fluid in a direction that is perpendicular or substantially
perpendicular to the path of web travel and away from the web. The
fluid movement 9 creates a low pressure region between the web edges
and the sheet edge region 16 of the stabilizer. The low pressure
region draws the edge 5 of the web towards the sheet.
[0027] The air movement and direction device 3 and the movement of
the fluid 9 blocks air currents from outside the machine from entering
the area near the side edges 5 of the web and the sheet edge region 16
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of the bottom 17 of the stabilizer. As such, the air movement device 3
and air movement 9 prevent outside air flows from disturbing the side
edges 5 of the web 4.
[0028] The air movement and direction device 3 may be a row of one or
more air knives, pipes, beams or bars with internal air passages and air
nozzles formed by drilled holes or slots along the length of the device 3.
The air movement and direction devices 3 are preferably mounted on or
in the vicinity of a bottom surface of the stabilizer 1 and, particularly, at
or outside the sheet edge region 16 of the bottom surface 17.
Alternatively, the stabilizer 1 may be positioned below the web and have
an upper surface adjacent the web, where the air movement device is
mounted on top of the upper surface. The bottom surface 17 of the
stabilizer adjacent the web may be flat, arched, contoured or have other
shape which faces the web.
[0029] A gap 2 may be formed between the region 16 of the substantially
planar bottom surface 17 of the stabilizer and the air movement or
direction device 3 to provide a gap 2 for the air movement that forces
the side edges 5 of the web 4 towards the sheet edge region 16 of the
planar surface. The gap 2 may be adjacent the air movement or
direction device 3, integrated into the stabilizer 1, or integrated into both
the air movement device 3 and the stabilizer 1.
[0030] The air movement or direction device(s) 3 may cause air
movement across the side edges regions 16 of the stabilizer and
through the gap 2 between the side edge regions 16 and the devices 3.
The air movement is at a velocity sufficient to influence the position and
orientation of the web edges 5 and cause a reduced pressure that
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moves the web edges into alignment, e.g., the same plane, as the
center portion of the web 4.
[0031] The gap 2 may also be between a solid bar gap forming device
3a, which is a type of air direction device, and the sheet edge region 16
of the stabilizer. The gap is adjacent a source 20 of a vacuum that
draws air through the gap. The source is next to the stabilizer, as
shown in Figure 3. The gap forming device 3a may not be a fluid
moving device and forms an obstruction directing air flow through the
gap. The gap forming device 3a may be a solid bar having a cross-
section shape of a rectangle, circle, oval, airfoil, wing or other shape.
Preferably, the cross-sectional shape of the gap forming device 3a
promotes the flow of air through the gap between the stabilizer and gap
forming device. The source of air, such as vacuum source 20 moving
through the gap may be pressurized air from the stabilizer, or a
separate fluid moving device, e.g., a vacuum 20, that moves air through
the gap.
[0032] The bottom surface 17 of the stabilizer 1 adjacent the web may
be smooth or rough, a bottom (or top) surface and a planar surface. The
sheet edge regions 16 of the bottom surface 17 of the stabilizer 1 are
aligned with the web edges 5 and may extend past the web edges 5 (as
shown in Figures 1, 2, 3, 4a, 5, 6a, 6b, 7a and 7b) or end at the web
edges (as shown in Figure 4b).
[0033] The air movement or direction device(s) 3, 3a may be mounted
near one or both of the sheet edge regions 16 of the stabilizer. The
device(s) 3, 3a may cause air movement starting at or outside of the
web edges 5 and cause the air movement to flow away from the web
edges, such as shown in Figures 4a and 4b, 5 and 6a. The devices 3,
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3a may also be located between the stabilizer and the web edges .5,
such as shown in Figure 6b. In Figure 6B, the air movement devices
include grooves or slots in the sheet edge region 16 of the stabilizer,
wherein the grooves or slots have air apertures to inject air out of the
stabilizer or draw air into the stabilizer. The air movement devices 3, 3a
may extend part way or full length of the stabilizer 1 and be fixed to or
moveable with respect to the stabilizer.
[0034] The air flowing from the air movement device 3 need not impinge
directly on the edges 5 of the web, as shown in Figures 2 and 4. While
the direct impingement of air on the edges 5 may force the edges
towards the stabilizer, the direct impingement of air may create stresses
and stretching of the web. Directing the air flow away from the web
edges without direct impingement of the air on the edges can create a
suction between the curled web edges 5 and the sheet edge region 16
of the stabilizer. This suction draws the web edges to the surface of the
stabilizer. As shown in Figures 3, 4a, 4b, 5, 6a, 6b, 7a, and 7b, air can
be directed through the gap 2 without impinging the air directly on the
web edges 5.
[0035] The air (see arrows 9) may be introduced along an inside surface
6 (Fig. 1) of the air movement device 3 facing the edges 5 of the web.
When introduced along the inside surface 6 of the device, a Coanda
effect that results in the air 9 moving along to the upper surface 7 of the
air movement device 3, which surface faces the gap 2, as illustrated in
Figure 7a or up to the surface 16 of the stabilizer as shown in Figure 9.
[0036] FIGURE 5 shows a stabilizer 1 having a recess (or protruding)
strip(s) 13 (or slots, gaps or grooves) in the sheet edge region 16 of the
bottom surface 17 of the stabilizer. The recess strip 13 provides a
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passage for the air movement away from the web edge 5. The
movement of air 9 along the strip 13 of the stabilizer 1 forms a low
pressure region between the web edge 5 and the sheet edge region 16
to cause the web edges 5 to move towards sheet edge region of the
stabilizer 1. The surface 13 may be parallel with, recessed into or
slightly protruding from the bottom surface of the stabilizer
[0037] FIGURES 6A and 6B show a stabilizer 1 in which the air
movement device 3 is an array of air openings, nozzles, air pipes, air
slots or air channels (collectively air directors 14) that directs an air flow
12 along the bottom surface of the stabilizer and away from the web
edges 5. The array of air directors 14 may be arranged continuously or
at regular or irregular intervals, preferably short intervals, along the
sheet edge region 16 of the bottom surface 17 of the stabilizer. The air
directors 14 may inject air into the sheet edge region 16 from either just
outside of the web edges 5 (as shown in Figure 6A) or inward of the
web edges 5 (as shown in Figure 6B). The air directors 14 may receive
pressurized air (27 in Fig. 8) through conduits internal to the stabilizer or
may be connected to suction devices that draw air through the directors.
The air directors 14 may be embedded in the stabilizer 1, or in an air
movement device 3 to provide an actual or effective gap 2 for air
movement. The movement of air 9 through gap 2 causes the web edges
to move 8 towards the stabilizer 1 and thereby eliminates or reduces
curl in the web edges 5.
[0038] FIGURE 8 is a schematic diagram showing the location of an air
movement device, an air knife 19, being positioned adjacent to the
sheet edge region 16 of the bottom planar surface 17 of a stabilizer.
The gap 10 between the air movement device 3, e.g., a conduit for air,
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and the web edge 5 is preferably in a range of zero to four inches, but
may be as much as two feet. A gap 2 is formed between the air
movement device 3 and the sheet edge region. The gap is preferably
less than one inch (e.g., 25 millimeters) and may be less than one-
quarter inch (e.g., 6 millimeters) in a vertical direction.
[0039] The air knife 19 and the air movement device 3 may be hollow
and coupled end to end to other knives or devices. The assembly of
knives or devices is connected to a source of pressurized air 27. The
pressurized air flows through the assembly of air knives (or devices 3)
and flows out air slots in the air knife arranged on an inside wall 6. As
the air flows from a slot in the air knife 19 follows the surface of the knife
and the air flows through the gap 2.
[0040] FIGURE 9 shows in cross-section an air knife 19, as an air
movement device 3, adjacent a sheet edge region 16 of a stabilizer 1
and a web 4. Air 23, e.g., pressurized air, is discharged from an air slot
22 in the air knife. The air slot 22 is arranged on an inside surface 6 of
the knife that generally faces the web 4. The air slot 22 may be near a
corner 24 on the knife between the inside surface 6 and a surface 25 of
the knife facing the gap 2.
[0041] Pressurized air 23 is discharged from the slot 22 at a higher
velocity than the moving air near the sheet edge region and web edge
5. The air discharged by the air knife flows from a conduit 28 in the air
knife that is supplied by a source of pressurized air external to the knife.
From the conduit 28, air flows into the slot 22 that is formed by the main
body 19 of the knife and a plate 30.
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[0042] As air 23 is discharged from the slot 22, the air flows along the
surfaces 6, 24 and 25 of the air knife and through the gap 2. The air
flows along the surfaces due to the coanda effect in which fluid flows
tend to attach to a curved surface, such as corner 24.
[0043] The movement of high velocity air 23 passing through the gap 2
creates a reduced pressure area in the gap 2 that sucks air 26 from near the
web edge 5 and sheet edge region 16. The suction of air 26 also applies a
force 31 to the web edge 5 that tends to uncurl the edge and maintain the web
edge 5 in the same plane as the remainder of the web.
[0044] Exemplary descriptions of reference numbers used in the
drawings:
1. Web Stabilizer
2. gap (gap to be greater than zero up to four inches, with the
preferred embodiment 0.001 inch to one inch)
3. Air movement or direction device 3 creating the gap 2 with
stabilizer 1, which device 3 may be, for example:
= An air knife or hollow channel with one or more apertures to
pass air;
= A separate component can be used to create a gap, such
as a solid bar or plate 3a. A source of pressurized air or
vacuum may be used to cause air movement through the
gap 2 with the same or air movement device 3 used to form
the gap.
The gap 2 creating apparatus may be an integral part of the
stabilizer 1
= The gap created by the device may be in the gap creating
air movement device 3 (making the bar or plate with a slot,
series of openings and so on) so the device 3 contacts the
stabilizer 1, but the gap 2 exists as an integral part of the
air movement device 3.
= The air movement device 3 may comprise one or more
pieces assembled to create the gap 2
3a. Gap forming device (also referred to as an air direction device)
4. Web
5. Web Side Edge (also called Web End)
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6. Inside surface of air movement or direction device facing web
edge.
7. surface of air movement or direction device facing stabilizer
8. direction of uncurling of web edge
9. Air or fluid movement direction
10. gap between web edge and air movement or direction device
in the direction of air movement
11. range of air movement directions
12. recessed or protruding area of stabilizer
13. air discharge opening(s) on, in or near stabilizer serving an air
movement device (Figures 6a, 6b)
14. air directors
15. coanda air flow
16. Sheet edge region at bottom surface of stabilizer
17. bottom surface of stabilizer
18. compressed air outlets and nozzles
19. Air knife
20. vacuum source
21. controller
22. slot in air knife to discharge air
23. air discharged by knife
24. corner on air knife
25. surface on air knife facing stabilizer
27. Pressurized air source
28. Air conduit in knife
30. Plate of knife.
31. Force applied to web edge
[0045] The apparatus and method disclosed herein may be used to
uncurl a web edge 5 or prevent curl by moving a fluid away from the
edge to create a force that draws the edge towards the surface of a
stabilizer. The apparatus may be an air movement device 3
incorporated in the stabilizer (see Fig. 6a and 6b) or an air movement
device 3 adjacent the stabilizer and spaced a horizontal distance from
the web edge of preferably no more than four inches. The air
movement device 3 may inject air from a source of pressurized air, such
as a compressor or blower, or a source of sub-atmospheric air such as
a vacuum. The air movement or direction device 3 may comprise a first
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device, e.g., a bar, which forms a gap 2 through with air is drawn and a
second device providing a source of air, such as a vacuum or
compressed air. These devices may be separate, such as shown in
Figures 3, 7A and 7B or integrated such as shown in Figures 4B, 6A
and 6B. The air may be applied at an elevation between the web and
the stabilizer (Fig. 6A), recessed within the stabilizer (Figs. 5 and 6B), at
the same elevation as the web (Fig. 6A) or at an elevation below both
the web and stabilizer (Figs. 3, 4B, 7A and 7B).
[0046] Further, the air from the air movement device may be introduced
beyond the edge 5 in a horizontal dimension, such in a range of zero to
four inches from the web edge. The air may be introduced such that the
air flows 15 along the surface of the stabilizer or air movement device 3
pursuant to the coanda effect. The air flows away from edge 5 of the
web in a direction substantially parallel to the surface of the stabilizer.
The apparatus may use the coanda effect to cause air to move away
from web through a gap 2.
[0047] In addition, a controller 21 (Fig. 4B), e.g., computer or manual
controls, may have an ability to adjust the air pressure or vacuum level
from the air movement device 3, the rate of air flow through the gap 2,
and the distance of the width of the gap and the horizontal distance
between the gap and edge of the web. For example, the air pressure,
vacuum level, air flow rate through the gap and dimensions gap may be
adjusted manually based on: observed curl in the web or by a curl
sensor, e.g., a light beam and light sensor, detecting excessive curl;
web speed, web tension or web crepe; and pressure sensors in the gap
or in the sheet edge region 16 of the stabilizer.
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[0048] While the invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be limited
to the disclosed embodiment, but on the contrary, is intended to cover
various modifications and equivalent arrangements included within the
spirit and scope of the appended claims.
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