Note: Descriptions are shown in the official language in which they were submitted.
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AIR LAYING FORMING STATION WITH BAFFLE MEMBER
FOR PRODUCING NONWOVEN MATERIALS
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to air laying forming stations and, more particularly,
to
air laying forming stations for producing nonwoven materials from first and
second
materials having a difference in characteristic or composition and including a
baffle
member for directing the flow of the second material by gravity and
independently of
the first material.
2. Discussion
Conventional air laying forming stations (ALFS) use one air stream to
transport
and distribute blends of materials which are different in characteristic or
composition,
for example high absorbency materials (HAM) and fibrous materials (FM). As
2o differences between the materials (such as size, shape, and density)
increase, the
materials behave differently in the common air stream and undesirable and
uncontrollable separation of the blend occurs. Separation problems increase as
the
flow distance increases and as the width of the ALFS and the nonwoven material
increase in the cross machine direction (CD). Such increasing distances,
widths and
behavioral differences of the materials in the air stream result in highly
variable basis
weights in the machine direction (MD) and the CD. Conventional ALFS have
typically been unable to provide uniform and controlled distribution of HAM in
nonwoven materials, especially as CD widths approach and exceed 1 meter.
Additionally, conventional ALFS have been unable to uniformly and controllably
3o distribute HAM in nonwoven materials as mass concentrations of HAM approach
and exceed 15-20% by weight.
As a result of transporting the blend of materials in a single air stream, the
conventional ALFS generally produce only nearly homogenous blends of HAM and
FM and cannot produce nonwoven materials having multiple zones of HAM and FM
concentrations in the Z-axis (orthogonal to the MD and CD). Thus, a single
conventional ALFS cannot produce a nonwoven material with nearly HAM-free or
reduced-HAM dusting zones in order to better contain the HAM within the
nonwoven material during further processing and consumer use. Benefits of
providing multiple HAM concentration zones along the Z-axis are well
recognized
4o within the art for various applications, including diapers, feminine
hygiene products,
etc. The art generally focuses on two key benefits of variable HAM
concentration
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2
zones. The first is an improvement to HAM efficiency and effectiveness, and
the
second is improved containment of HAM within the structure.
Transporting the HAM and FM to form absorbent bodies using separate air
streams has been proposed, for example in U.S. Patent No. 4,927,582 to Bryson.
In
Bryson, blower 48 propels HAM 28 via one or more pipeline conduits 20 into
io forming chamber 10. Vacuum source 32 creates an air flow, indicated by
arrows 36,
which draws FM 14 against forming screen 30. Baffles 34 are attached to
opposing
sidewalk (e.g. in a CD) and are used to regulate the cross-directional
distribution of
HAM across web 41.
In use, however, air injection to propel HAM 28 into forming chamber 10
is disrupts the flow of FM 14 onto forming screen 30 adversely affecting
uniform
distribution of FM 14. Use of one or more pipeline conduits 20 provides poor
CD
control of the basis weight of HAM 28 deposited onto forming screen 30,
particularly for wide machines (in the CD). In addition, the use and
positioning of
baffles 34 disrupts FM 14 formation on forming screen 30.
2o In Bryson, HAM and FM are introduced separately, however CD basis weight
profiling of HAM 28 is accomplished after HAM 28 mixes with FM 14 using
baffles
34. Profiling HAM 28 using baffles 34 as disclosed in Bryson also changes the
CD
basis weight profile of FM 14. Thus, independent CD basis weight profiling of
FM 14
and HAM 28 is not achieved.
25 Therefore, an ALFS which forms a nonwoven material with reduced MD and
CD variability of a second material, (for example HAM) within a first material
(for
example FM) which has a significant difference in characteristic or
composition is
desirable. Additionally, an ALFS which forms a nonwoven material by providing
control of the Z-axis placement of a second material (for example HAM) within
a
3o first material (for example FM) which has a significant difference in
characteristic or
composition is desirable.
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3
SUMMARY OF THE INVENTION
An air laying forming station (ALFS) according to the invention, forms a
nonwoven
material from a first material and a second material having at least one
characteristic different
from said first material. The ALFS includes a forming chamber and a forming
screen moving
relative to said forming chamber, for receiving deposit of said first and
second materials. A
first material distributor or distributors distributes said first material. A
flow device provides
an air flow which deposits said first material onto said forming screen. A
second material
distributor distributes said second material, independently from said first
material, by gravity,
between said first material distributor and said forming screen.
According to one feature of the invention, the second material distributor
employs a
baffle member along which said second material is transported in order to
direct the flow of
said second material by gravity.
According to another feature of the invention, the baffle member of said
second
material distributor introduces said second material into the forming chamber
of the ALFS.
According to still another feature of the invention, the baffle member
includes upper
and lower planar sections defining an angle therebetween.
According to still another feature of the invention, the baffle member
includes an
arcuate section or sections.
According to yet another feature of the invention, a cover is provided for
said baffle
member to reduce the disruption of said second material as it is being
distributed and directed
by said baffle member.
Still other features will be readily apparent.
According to one embodiment of the present invention, an air laying forming
station
(ALFS) for forming a nonwoven substrate from a first material and a second
material having
at least one physical characteristic substantially different from the first
material comprises:
a forming chamber;
forming means, moving relative to the forming chamber, for receiving deposit
of the
first and second materials;
first distributing means for supplying the first material;
flow means for providing an air flow which deposits the first material onto
the
forming means; and
second distributing means for delivering the second material, independently
from the
first material between the first distributing means and the forming means, by
gravity along a
baffle member.
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3a
According to another embodiment of the present invention, in an air laying
forming
station (ALFS) for forming an nonwoven substrate from a first material and a
second material
having at least one physical characteristic substantially different from the
first material, the
ALFS including a forming chamber, forming means for receiving deposit of the
first and
second materials, first distributing means for supplying the first material,
and flow means for
providing an air flow which deposits the first material onto the forming
means, an
improvement comprises:
second distributing means for delivering the material, independently from the
first
material between delivery of the first material and the forming means, by
gravity along a
baffle member.
According to another embodiment of the present invention, a method of forming
a
substrate in an air laying forming station from first and second materials,
wherein at least one
physical characteristic of the second material is substantially different from
the first material,
and wherein the ALFS includes a forming chamber, forming means, moving
relative to the
forming chamber, for receiving deposit of the first and second materials,
first distributing
means for supplying the first material, and flow means for providing an air
flow which
deposits the first material onto the forming means, comprises the steps of
feeding the second
material, independently from the first material between delivery of the first
material and the
forming means, by gravity along a baffle member.
BRIEF DESCRIPTION OF THE DRAWINGS
The various advantages of the present invention will become apparent to
skilled
artisans after studying the following specification and by reference to the
drawings in which:
Figure 1 is a side view of an air laying forming station according to a first
embodiment of the present invention;
Figure 2 is a cross-sectional view of a nonwoven material taken along line 2-2
in
Figure 1;
Figure 3A is a side view of an air laying forming station a6cording to a
second
embodiment of the present invention;
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Figure 3B is a side view of an air laying forming station similar to Figure 3A
but with a dual exit baffle member according to a third embodiment of the
present
invention;
Figure 4 is a side view of an air laying forming station according to a fourth
embodiment of the present invention;
1o Figure 5 is a side view of an air laying forming station according to the
invention illustrating parameters ai~ecting the distribution of materials I
and 2 within
the nonwoven material;
Figure 6 is a simplified side view of an air laying forming station according
to
the invention illustrating example bai~le member set-up parameters and the
resultant
nonwoven material structures;
Figure 7 is a cross-sectional view of an illustrative nonwoven material taken
along section 3-3 of Figure 6.
DESCRIPTION OF THE PREFERRED EMBODIMENT
2o While the background discussion was primarily limited to discussions of
problems with air laying forming stations (ALFS) for producing absorbent
bodies,
including high absorbency materials (HAM) and fibrous materials (FM), skilled
artisans will appreciate that the foregoing description applies to nonwoven
materials
incorporating other materials.
Figure 1 illustrates a side cross-sectional view of ALFS 10. Skilled artisans
can
appreciate that ALFS 10 can accommodate variable widths in the CD. The length
and height of ALFS 10 in the MD and Z-axis directions, respectively, can also
be
varied as desired. In Figure 2, the Y-axis indicates the MD, the X-axis
indicates the
cross-machine direction (CD), and the Z-axis indicates the thickness of the
nonwoven
3o material. The Z-axis is orthogonal to the X and Y-axis. ALFS 10 according
to the
-invention produces nonwoven material 14 with Z-axis zones of controlled
concentrations of first material 26 and a second material 34. For example,
ALFS 10
according to the invention produces nonwoven material 14 which includes
dusting
zones 18 and 22, each containing predominantly and preferably only first
material 26
surrounding a middle zone 30 which is a nearly homogenous mix of first
material 26
and second material 34. Outer dusting zones 18 and 22 provide surfaces with
significantly reduced concentrations (preferably free) of second material 34,
that act
as barriers, to reduce the loss of second material 34 during further
processing and
consumer use. Outer dusting layers 18 and 22 are described in further detail
in
4o commonly assigned U.S. Patent Nos. 4,904,440, entitled "Apparatus for and
Methods of Airlaying Fibrous Webs Having Discrete Particles Therein" and
CA 02205903 1999-08-26
4,908,175, entitled "Apparatus for and Methods of Forming Airlaid Fibrous Webs
having a
Multiplicity of Components".
First material 26 has at least one characteristic different than second
material
34. For example, first material 26 can have a blend ratio, composition, size,
shape, density,
hydrophilicity, absorbency, chemistry. function, etc. which is different than
one or more
corresponding characteristics of second material 34. First material 26 and
second material 34
can be blends of or pure cellulose or wood pulp fibers which can be natural,
or chemically,
mechanically, or thermally modified, stiffened, or cross-linked; synthetic
fibers such as staple
or matrix fibers (polyester for example) or bonding fibers
(polyethylene/polypropylene
bicomponent for example); super absorbent fibers, particles, powders, or
foams; odor control
particles or powders; adhesive or bonding particles or powders; etc. Still
other types of
materials will be apparent to skilled artisans.
ALFS 10 of Figure 1 produces nonwoven material 14 on a forming screen 38 which
preferably moves relative to ALFS 10. For example, forming screen 38 can be in
the form of
an endless belt mounted on support rollers 42 and 44. A suitable driving
means, for example
an electric motor 46, rotates at least one of the support rollers 42 or 44 in
a direction indicated
by arrows "A" at a selected speed. As a result, forming screen 38 moves in a
machine
direction (MD) indicated by arrow "B".
Forming screen 38 can be provided in other forms, for example in the form of a
circular drum which can be rotated using a motor as disclosed in Bryson U.S.
Patent No.
4,927,582. Alternately, ALFS 10 can move relative to stationary forming screen
38, or both
ALFS 10 and forming screen 38 can move relative to each other. Preferably
forming screen
38 is made of plastic, however, metal such as bronze is also an acceptable
material for
forming screen 38. Forming screen 38 can be an Electrotech 4 distributed by
Albany
International located in Portland, Tennessee. As can be appreciated by skilled
artisans, other
forming screens 38 can be employed.
ALFS 10 further includes a forming chamber 50 with downstream and upstream
endwalls 54 and 56, respectively. Sidewalk 60, connecting opposing ends of
downstream and
upstream endwalls 54 and 56, respectively, are also provided. ALFS 10 employs
first material
distributors 66 and 68 which provide the desired distribution of first
material 26 inside
forming chamber 50 across the desired width in the CD. Preferably, first
material distributors
66 and 68 are rotating cylindrical distributing screens. Such distributing
screens are disclosed
in detail in U.S. Patent No. 4,640,810 entitled "System for Producing an Air
Laid Web". First
material 26 is fed into the interior of first material distributing screens 66
and 68. As first
material distributing screens 66 and 68 rotate,
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first material 26 is delivered uniformly through the rotating cylindrical
screens. While
first material distributing screens 66 and 68 are disclosed, one or more other
suitable
distributors are contemplated and can be employed.
ALFS 10 may also include a vacuum source 70, such as a conventional blower,
for creating a selected pressure differential through forming chamber 50 to
draw first
to material 26 out of distributors 66 and 68 against forming screen 38. Seal
rollers 71
and 72 reduce vacuum loss between forming chamber 50 and forming screen 38.
Preferably, vacuum source 70 is a blower connected to vacuum box 72 which is
located underneath forming chamber 50 and forming screen 38. Vacuum source 70
creates an airflow, indicated by arrows "C" in Figure 1, through forming
chamber 50
and forming screen 3 8 into vacuum box 72. Vacuum box 72 can include seal
deckles
74 and 75 which directly contact forming screen 38 approximately below seal
rollers
71 and 72. Air flow "C" causes and directs the deposit of first material 26
and, to a
lesser extent, the deposit of second material 34 on forming screen 38.
A bai~le member 76 directs second material 34 supplied by a second material
2o distributor 80 into forming chamber 50, underneath first material
distributors 66 and
68 and onto forming screen 38. Preferably, second material distributor 80
distributes
second material 34 across a desired width, in a desired pattern, in the CD,
and second
material 34 is conveyed primarily by gravity.
Baffle member 76 can be adjacent to upstream endwall 56, as shown in Figure
1. Alternately, baffle member 76 can be adjacent to downstream endwall 54 or
both
upstream and downstream endwalls 56 and 54, respectively. The baffle member 76
may extend from a midsection of the endwalls 56 and 54, as shown. Alternately,
as
illustrated in Figures 3A and 3B, a baffle member 90 can be located between
first
material distributors 66 and 68. Additionally, as illustrated in Figure 3B, a
baffle
member 92 may have multiple exits 94 and 96. Baffle member 76, 90 and 92 can
be
an arcuate section as illustrated in Figure 1. Alternately, baffle member 76
can
consist of a single flat section, or preferably at least two flat sections
connected at
angles relative to each other, as will be described in conjunction with Figure
4. Other
shapes will be readily apparent to skilled artisans. Preferably, baffle member
76 has a
width approximately equal to first material distributors 66 and 68 and the
desired
nonwoven material width in the CD.
In use, motor 46 rotates support rollers 42 and 44 which moves forming screen
38 relative to forming chamber 50. Vacuum source 70 creates air flow "C" which
draws first material 26 supplied by first material distributors 66 and 68 onto
forming
4o screen 38. Second material distributor 80 meters and distributes flow of
second
material 34, independent of first material 26. Second material 34 falls
primarily by
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gravity along baffle member 76 onto forming screen 38. As such, ALFS 10
according to the invention delivers distributed second material 34 by gravity
between
first material distributors 66 and 68 and forming screen 38 and separate and
independent of delivery of first material 26. ALFS 10 provides uniform
delivery of
first material 26 and second material 34 in the MD and CD. In other words,
ALFS
10 according to the invention independently profiles both first material 26
and second
material 34 before mixing the two materials in forming chamber 50. As such,
undesirable and uncontrollable separation of the dissimilar materials within a
common
air stream is avoided, and ALFS 10 according to the invention significantly
reduces
the undesirable variability of second material 34 in X- and Y-axis directions
(e.g. CD and MD) without significantly altering the deposition of first
material 26 on
forming screen 38. Baffle members 76, 90 and 92 are positioned to minimize the
disruption of first material 26 formation. Importantly, ALFS 10 can be
constructed
to various widths in the X-axis direction or CD, and the variability of second
material
34 in the MD and CD is not a function of ALFS 10 width in the X-axis direction
or
2o CD.
Typically, the flow of second material 34 from second material distributor 80
is
constant and uniform in both the MD (i.e. time) and the CD, however, if
nonwoven
material needs dictate, the flow of second material 34 can be patterned in the
MD
and CD by appropriate design modifications to second material distributor 80.
For
example, the baffle member 76 may have grooves or channels, to provide a
striped
effect to the second material 34. This yields a second material 34
distribution which
is cyclic, and repeating in the CD. Such a cyclic repeating pattern of second
material
34 is considered to be substantially uniform in the CD, due to the repeating
nature,
just as a second material 34 distributed without a repeating pattern is
considered
3o substantially uniform hereunder. The basis is that at any CD location, in
either
configuration, the second material 34 distribution substantially matches that
at other
CD locations. In conjunction with the use of the subject baffles, patterned
flow of
second material 34 allows for the production of nonwoven materials with
various and
controlled concentration patterns of second material 34 in the MD, CD, and
thickness of the nonwoven material. Various devices are known in the art which
could be used as second material distributor 80, a preferred device for
dispensing
HAM is a dispensing machine for dusting, seeding, and topping of dry
materials.
w Specifically, model Coat-O-Matic 23.62-DE-S sold by Christy Machine Company
in
Fremont, Ohio.
4o In Figure 4, a presently preferred embodiment, ALFS 100, is illustrated.
For
purposes of clarity, reference numbers from Figures 1 and 2 will be used in
Figure 4
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where appropriate. In addition, details, for example motor 46, vacuum source
70,
etc., have been omitted to simplify Figure 4.
ALFS 100 includes a fixture 102 with a baffle member 104 and a cover 106.
Baflle member 104 preferably includes upper and lower planar sections 108 and
110,
respectively. Upper planar section 108 is attached to upstream endwall 56 in
any
l0 suitable manner, for example glue, solder, bolts, clamps, etc. Other
suitable means of
attaching upper planar section 108 of baffle member 104 to endwall 56 will be
apparent to skilled artisans. Lower planar section 110 forms an angle "T" with
respect to upper planar section 108. Preferably, upper and lower planar
sections 108
and 110, respectively, are formed from a single planar section of material
which has
been bent. LEXAN ~ is a preferred material of construction for fixture 102.
Preferably the LEXAN ~ has a thickness of 0.25 inches
The cover 106 is mounted adjacent to upper planar section 108 of baffle
member 104 using any suitable means which does not significantly interrupt the
flow
of second material 34 passing along upper and lower planar sections 108 and
110,
2o respectively. The cover 106 may also be made of LEXAN~ and has a thickness
of
about 0.25 inches. For example, spacers 114 corresponding to the desired
clearance
between cover 106 and upper planar section 108 of baffle member 104 can be
glued
to the inner surfaces of cover 106 and upper planar section 108 of baffle
member
104. Other suitable means of attaching cover 106 to upper planar section 108
of
baffle member 104 will be apparent to skilled artisans. Clearance between
baffle
member 104 and cover 106 should be as small as possible, but sufficient to
allow a
desired maximum flow of second material 34 to pass there between. A typical
clearance is 0.1875 inch. Upper planar section 124 of cover 106 and upper
planar
section 108 of baffle member 104 can be adapted to support second material
3o distributor 80. Lower planar section 126 and upper planar section 124 of
cover 106
form an angle "S" with respect to each other. Angle "S" should be as great as
possible, but sufficiently small to allow the space between upper planar
section 108
of baffle member 104 and upper planar section 124 of cover 106 to be great
enough
to capture the entire out-put of second material distributor 80. A typical
value for
angle "S" is 140 degrees although higher and lower angles can be~employed.
The lower planar section 126 of cover 106 extends toward angle "T" and
preferably ends at a distance from lower planar section 110 of baffle member
104
such that the clearance between the end of lower planar section 126 of cover
106 and
lower planar section 110 of baffle member 104 is equal to the clearance
between
44 baffle member 104 and cover 106. However, lower planar section 126 of cover
106
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may extend further such that it lies parallel to lower planar section 110 of
baffle
member 104 beyond angle "T".
A sufficient clearance must also be maintained in this case. Thus, lower
planar
section 126 of cover 106 would also have to contain an angle equivalent to
angle
...L...
1o In Figure 5, important design parameters for baffle member 104 of ALFS 100
are illustrated in further detail. For purposes of clarity, reference numbers
from
Figures l, 2, and 4 will be used in Figure 5 where appropriate. In addition,
details,
for example motor 46, vacuum source 70, etc., have been omitted to simplify
Figure
5. Alternately, baffle member 104 including cover 106 can be independent of
endwalls 56 and/or 54 and can introduce second material 34 from either or both
endwalls 56 or 54. These design parameters affect the Z-axis position of
second
material 34 within nonwoven material 14. More specifically, these design
parameters
affect the Z-axis location of second material 34 within nonwoven material 14
by the
specific location of the tip of baffle member 104 and by controlling the
momentum
vector of second material 34 as it leaves bale tip 130 of baffle member 104.
It
should be noted that the basic design principles are discussed in specific
reference to
the ALFS design illustrated in Figure S. These principles can be easily
translated to
other ALFS designs discussed in this disclosure.
The basis weight and thickness of nonwoven material 14 gradually increase as
nonwoven material moves in the machine direction, as indicated by arrow "D",
through forming zone 50. This is illustrated by the thickness difference of
nonwoven
material 14 near upstream endwall 56 as compared to near downstream endwall
54.
The initial elements of first material 26 which fall onto forming wire 3 8
near
upstream endwall 56 form wire-side surface 200 within nonwoven material 14. As
3o forming wire 38 continues to move in the machine direction through forming
zone
S0, additional elements of first material 26 fall onto the building surface of
nonwoven
material 14 continually increasing the basis weight and thickness of nonwoven
material 14 until the final elements of first material 26 fall onto the
surface of
nonwoven material 14 near downstream endwall 54 forming non-wire-side surface
201 within nonwoven material 14. The Z-axis location of any element of first
material 26 depends on where that element falls onto the building surface of
nonwoven material 14 along the machine direction axis within forming zone 50
relative to endwalls 54 and 56. Elements of first material 26 that fall onto
the
building surface of nonwoven material 14 in forming chamber 50, near upstream
4o endwall 56 will have a Z-axis location near wire-side surface 200 within
nonwoven
material 14. Elements of first material 26 that fall onto the building surface
of
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5 nonwoven material 14 in forming chamber 50, near downstream endwall 54 will
have
a Z-axis position near non-wire-side surface 201 within nonwoven material 14.
Elements of first material 26 that fall onto the building surface of nonwoven
material
14 more intermediate between endwalls 54 and 56 will have a Z-axis position
more
intermediate between surfaces 200 and 201 within nonwoven material 14.
1o The Z-axis location of second material 34 within nonwoven material 14
follows
a similar pattern. If second material 34 falls onto the building surface of
nonwoven
material 14 near upstream endwall 56, second material 34 will have a Z-axis
location
near wire-side surface 200 within nonwoven material 14. If second material 34
falls
onto the building surface of nonwoven material 14 near downstream endwall 54,
second material 34 will have a Z-axis location near non-wire-side surface 201
within
nonwoven material 14. If second material 34 falls onto the building surface of
nonwoven material 14 more intermediate between endwalls 54 and 56, second
material 34 will have a Z-axis location more intermediate between surfaces 200
and
201 within nonwoven material 14.
2o The momentum vector of second material 34 as it leaves baffle tip 130 of
baffle
member 104 along with the specific location of baffle tip 130 of baffle member
104
determine, to a large extent, where, along the machine direction (Y-axis),
second
material 34 falls onto the building surface of nonwoven material 14 within
forming
chamber 50 and thus the Z-axis location of second material 34 within nonwoven
materia114.
The momentum vector includes both a magnitude and a direction. Both are
important in determining the Z-axis location of second material 34 within
nonwoven
material 14. Both can be affected by the design parameters of baffle member
104.
The magnitude of the momentum vector is a function of mass and velocity, but
3o since mass is fixed for a given second material 34, the magnitude of the
momentum
vector is basically a function of the velocity of second material 34 when it
leaves
baffle tip 130 of bafDe member 104. Second material 34 with a relatively large
momentum vector magnitude will fall closer to upstream endwall 56 and
therefore
have a Z-axis location relatively closer to wire-side surface 200 within
nonwoven
material 14. Conversely, second material 34 with a relatively small momentum
vector magnitude will fall closer to downstream endwall 54 and therefore have
a
Z-axis location relatively closer to non-wire-side surface 201 within nonwoven
material 14. Further, an ALFS according to the invention utilizes gravity to
impart
velocity to second material 34. Design parameters of baffle member 104 control
the
4o effect of gravity on second material 34 control the velocity of second
material 34 in
other words, the design parameters effect the magnitude of the momentum vector
of
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second material 34 and therefore the Z-axis location of second material 34
within
nonwoven material 14. Examples of design parameters which provide this control
are the vertical height H1 of second material distributor 80 above bai~le tip
130 of
baffle member 104, the horizontal distance LI between the second material
distributor 80 and baffle tip 130 of baffle member 104, and the roughness of
upper
to surface 204 of baffle member 104. Relatively high values of second material
distributor height H 1, relatively low values of horizontal distance L I and
relatively
smooth surfaces 204 tend to produce the highest velocities of second material
34 as it
leaves bai~le member 104. Conversely, relatively low vertical distances HI,
relatively
high horizontal distances L 1 and relatively rough surfaces 204 tend to
produce the
lowest velocities of second material 34 as it leaves baffle member 104. Other
design
parameters for controlling the magnitude of the momentum vector will be
obvious to
skilled artisans.
Second material 34 is most often a blend of elements of various sizes and
masses. Since gravity acts on each individual element rather than on second
material
34 as a whole, the momentum vector's magnitude varies from element to element.
The relatively high mass elements have a momentum vector with a relatively
high
magnitude and tend to travel firrther from baffle tip 130 of baffle member 104
within
forming chamber 50 before being deposited on the building surface of nonwoven
material 14. The relatively high mass elements therefore have a Z-axis
location
closer to wire-side surface 200 within nonwoven material 14. The converse
should
be expected for the relatively low mass elements.
With continued specific reference to the ALFS illustrated in Figure 5, the
distribution of the various individual elements composing second material 34
will
tend to be stratified with the higher mass elements located closer to wire-
side surface
200 within nonwoven material 14 and the lower mass elements located closer to
non-wire-side surface 201 within nonwoven material 14. This Z-axis
stratification by
element mass can be advantageous in many product applications, especially
those
where nonwoven material 14 is an absorbent core for a disposable absorbent
article
and second material 34 is a particulate superabsorbent material.
The direction segment of the momentum vector indicated by an angle "a" in
Figure 5, describes the direction in which second material 34 is traveling
when it
leaves baffle tip 130 of baffle member 104. Angle "a" is formed by lower
planar
section 110 of baffle member 104 and a line "L" which is parallel to forming
screen
38. When "a" is small, second material 34 is traveling predominantly in a
horizontal
4o direction when it leaves baffle tip 130 of baffle member 104. When "a" is
large in
value (upward or downward), second material 34 is traveling predominantly in a
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vertical direction when it leaves baffle tip 130 of baffle member 104.
Relatively low
values of "a" will tend to deposit second material 34 on the building surface
of
nonwoven material 14 relatively close to upstream endwall 56 within forming
chamber 50 and therefore second material 34 will have a Z-axis location
relatively
close to wire-side surface 200 within nonwoven material 14. Conversely,
relatively
to high values of "a." will tend to deposit second material 34 on the building
surface of
nonwoven material 14 relatively close to downstream endwall 54 within forming
chamber 50 and therefore second material 34 will have a Z-axis location
relatively
close to non-wire-side surface 201 within nonwoven material 14.
The specific location of bafhle tip 130 of bale member 104 is also critical to
the Z-axis location of second material 34 within nonwoven material 14. The
critical
aspects of location are vertical height H2 of bafl7e tip 130 above forming
wire 38 and
horizontal distance L2 between baffle tip 130 and upstream endwall 56. Larger
values of vertical height H2 allow second material 34 to travel further in the
horizontal plane and thus be deposited on the building surface of nonwoven
material
2o 14 closer to upstream endwall 56 and, therefore, second material 34 will
have a
Z-axis location closer to wire-side surface 200 within nonwoven material 14.
Larger
values of horizontal distance L2 cause second material 34 to be deposited on
the
building surface of nonwoven material 14 fiuther from upstream endwall 56 and,
therefore, second material 34 will have a Z-axis location closer to non-wire-
side
surface 201 within nonwoven material 14.
The following are examples of nonwoven material compositions which can be
produced using ALFS 100:
First material 26 is a blend of 85% cellulose wood pulp (Weyerhaeuser NB416.
for example) and 15% polyethylene/polypropylene bicomponent bonding fiber
(Danaklon ES-C 1.7 dtex X 6 mm, for example). Second material 34 is a super
absorbent particle (Nalco 1180, for example). The mass ratio of first material
26 to
second material 34 is approximately 1:1.
First material 26 is a blend of 70% cellulose wood pulp (Weyerhaeuser NB416,
for example) and 20% polyethylene/polypropylene bicomponent bonding fiber
(Danaklon ES-C 1.7 dtex X 6 mm, for example) and 10% super absorbent particle
(Nalco 1180, for example). Second material 34 is a super absorbent particle
(Nalco
1180 for example). The mass ratio of first material 26 to second material 34
is
approximately 2:1.
First material 26 is a blend of 50% NB416 and 50% polyester staple/matrix
4o fiber (Hoechst Celanese T183 15 dpf X 0.5 inch, for example). Second
material 34 is
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WO 96117986 PCT/US95/09270
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an odor control agent (Activated Charcoal, PCB by Calgon, for example). The
mass
ratio of first material 26 to second material 34 is approximately 5:1.
First material 26 is a blend of 85% cellulose wood pulp (Weyerhaeuser NB416,
for example) and 15% polyethylene/polypropylene bicomponent bonding fiber
(Danaklon ES-C 1.7 dtex X 6 mm, for example). Second material 34 is a
to polyethylene powder bond agent (Veraplast Vertene Neutro 200, for example).
The
mass ratio of first material 26 to second material 34 is approximately 6:1.
First material 26 is a blend of 75% cellulose wood pulp (Weyerhaeuser NB416,
for example) and 25% super absorbent fiber (Fibersorb Type 1700 produced by
Arco
Chemical for example). Second material 34 is a blend of 75% grass seed and 25%
dry fertilizer. The mass ratio of first material 26 to second material 34 is
approximately 1:2. Other nonwoven material compositions will be readily
apparent
to skilled artisans.
Figure 6 illustrates example set-up parameters and Figure 7 illustrates the
resultant nonwoven material 14 structures created thereby. The ALFS of Figure
6
(excluding elements of the invention) is a Dan Web Lab Former as supplied by
Dan-Webforming Int. LTD. of Aarhus, Denmark, and which has a machine direction
E. First material distributor 80 is a model Coat-O-Matic 23.62-DE-S dispensing
machine sold by Christy Machine Company of Fremont, Ohio. In these examples,
first material 26 is blend of 67% (by mass) Flint River Southern Softwood
Kraft pulp
and 33% (by mass) Danaklon ES-C 1.7 dtex X 6 mm Bicomponent Bonding Fiber,
second material 34 is Nalco 1180 High Absorbency Material. First material 26
and
second material 34 were distributed by first material distributors 66 and 68
and
second material distributor 80, respectively, at rates such that the resultant
nonwoven
material 14 consists of 71.7% (by mass) first material 26 and 28.3% (by mass)
3o second material 34. The Flint River Southern Softwood Kraft pulp was
prepared by
_defibrating dry lap of the same material with a Dan Web Defibrator Model
Number
140. Since individual nonwoven material 14 structures have unique benefits
relative
to a given final application need, a single preferred set of set-up parameters
cannot be
identified. As such, Tables 1 - 3 gives examples of set-up parameters relative
to
Figure 6 and a description of the resultant nonwoven material 14.
For purposes of clarity, reference numbers from Figures 1, 2, 4, and 5 will be
used in Figure 6 where appropriate. In addition, details, for example motor
46,
vacuum source 70, etc., have been omitted to simplify Figure 6. As can be
appreciated from Figure 6, cover member 106 can be omitted. Parameters
associated
4o with the specific ALFS under consideration which aid in the illustration of
the
examples are given. Angle "13" is the angle made by endwall 56 with respect to
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forming screen 38. As indicated in Figure 6, "13" is equal to 78 degrees and
is held
constant for all examples given. Vertical distance H3 is the distance between
the
bottom surfaces of first material distributors 66 and 68. As indicated in
Figure 6, H3
is equal to 13.5 inches and is held constant for all examples given.
Horizontal
distance L3 is the distance between seal rolls 71 and 72 along forming screen
38. As
to indicated in Figure 6, L3 is equal to 20 inches and is held constant for
all examples
given. Horizontal distance LS is the diameter of first material distributors
66 and 68.
As indicated in Figure 6, L4 is equal to 11.75 inches and is held constant for
all
examples given.
Figure 7 illustrates the example nonwoven material 14 structures given as
illustrative examples in Tables 1 - 3. The Z-axis or thickness dimension of
nonwoven
material 14 is divided into 9 zones which are numbered 301 through 309,
consecutively, with one surface of zone 301 being wire-side surface 200 of
nonwoven material 14 and one surface of zone 309 being non-wire- side surface
201
of nonwoven material 14.
2o In Tables 1 - 3, with reference to Figures 6-7, examples are offered to
illustrate
the effect of some baffle member 104 set-up parameters on the Z-axis
distribution of
materials 1 and 2 in nonwven material 14.
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a = 18° H 1 = 37.25 inchesH2 = 9 inches L 1 = 5.5 inches L2 = 16.6
inches
Material of Construction is Smooth Lexan
to
Zone First Material Second Material% Second Material
Basis Weight Basis Weieht bar Mass
309 22.2 gsm 2.6 gsm 10.5
308 22.9 gsm 2.4 gsm 9.5
15 307 24.3 gsm 3.0 gsm 11.0
306 30.7 gsm 6.9 gsm 18.4
305 31.5 gsm 9.9 gsm 23.9
304 29.1 gsm 18.2 gsm 34.5
303 26.9 gsm 22.3 gsm 45.3
302 24.5 gsm 16.6 gsm 40.4
301 26.2 gsm 11.9 ;~sm 31.2
Total 238.3 gsm 93.8 gsm 28.3
Table 2
a = 48° Hl = 37.25 inches H2 = 6.75 inches L1 = 2.75 inches L2 = 19.75
inches
Material of Construction is Smooth Lexan
3o Zone First Material Second Material% Second Material
Basis Weight Basis Weight by Mass
309 26.0 gsm 13.3 gsm 33.9
308 30.5 gsm 26.3 gsm 46.3
307 31.4 gsm 28.2 gsm 47.3
306 34.5 gsm 20.6 gsm 37.4
305 36.5 gsm 9.2 gsm 20.0
304 34.0 gsm 6.1 gsm 15.2
303 30.5 gsm 5.0 gsm 14.0
302 28.3 gsm 1.9 gsm 6.3
301 31.7 gsm 1.3 gsm 3 9
Total 283.4 gsm 111.8 gsm 28.3
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Table 3
a= 48° H 1 = 37.25 inches H2 = 9.3 inches L 1 = 4.5 inches L2 = 17.75
inches
Material of Construction is Smooth Lexan
Zone First Material Second Material % Second Material
Basis Weight Basis Weight by Mass
309 23.9 gsm 1.2 gsm 4.7
308 31.3 gsm 3.0 gsm 8.8
307 34.1 gsm 15.6 gsm 31.3
306 33.9 gsm 27.0 gsm 44.4
305 35.4 gsm 29.0 gsm 45.0
304 34.7 gsm 20.8 gsm 37.4
303 31.9 gsm 10.9 gsm 25.5
302 29.4 gsm 4.7 gsm 13.7
301 32.5 gsm 1.2 gsm 3.6
Total 287.2 gsm 113.4 gsm 28.3
The various advantages of the present invention will become apparent to those
skilled in the art after a study of the foregoing specification and following
claims.
