U.S. patent number 3,750,236 [Application Number 05/225,263] was granted by the patent office on 1973-08-07 for method and apparatus (discontinuous imperforate portions on backing means of open sandwich).
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Frank Kalwaites.
United States Patent |
3,750,236 |
Kalwaites |
August 7, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS (DISCONTINUOUS IMPERFORATE PORTIONS ON BACKING
MEANS OF OPEN SANDWICH)
Abstract
A method and apparatus for producing, from a layer of fibrous
material such as a fibrous web, nonwoven fabrics that contain
apertures or holes, or other areas of low fiber density, and have a
plurality of patterns that alternate and extend throughout the
fabric. One form of the method includes the steps of supporting the
starting web upon a backing means that is foraminous except for a
discontinuous pattern of imperforate portions and has protuberances
and troughs alternating across its foraminous portions, then
directing fluid rearranging forces substantially uniformly and
continuously across the surface of the web, causing some of the
fluid streams to strike the imperforate portions of the backing
means, and others to strike the protuberances on the backing means,
to deflect the same, all of the fluid streams ultimately passing
through the foraminous portions of the backing means. Each
discontinuous imperforate portion extends along the surface of the
backing means in each direction a distance at least about twice the
horizontal distance between the bottoms of a pair of immediately
adjacent troughs. Each pair of immediately adjacent discontinuous
imperforate portions spans between them at least one protuberance
and a trough on each side of the protuberance. The imperforate
portions of the backing means may rise above the foraminous
portions. The resulting fabric consists of fibers that have been
rearranged to provide a first pattern of holes or other areas of
low fiber density corresponding to the imperforate portions of the
backing means, and a second pattern corresponding to protuberances
on the foraminous portions of the backing means.
Inventors: |
Kalwaites; Frank (Gladstone,
NJ) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
26695787 |
Appl.
No.: |
05/225,263 |
Filed: |
February 10, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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22313 |
Mar 24, 1970 |
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Current U.S.
Class: |
28/104 |
Current CPC
Class: |
D04H
18/04 (20130101) |
Current International
Class: |
D04H
1/70 (20060101); D04h 011/00 () |
Field of
Search: |
;19/161P ;28/72NW
;162/123,318 ;161/150,169 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Newton; Dorsey
Parent Case Text
This is a continuation application of my co-pending application
Ser. No. 22, 313, filed Mar. 24, 1970, now abandoned.
Claims
I claim:
1. Apparatus for producing a patterned nonwoven fabric having a
plurality of patterns of areas of low fiber density that alternate
and extend throughout said fabric, from a layer of fibrous starting
material whose individual fibers are in mechanical engagement with
one another but are capable of movement under applied fluid forces,
which comprises: backing means for said layer of fibrous starting
material, said means having portions which are imperforate and
portions which are foraminous, said imperforate portions being
discontinuous and said foraminous portions being continuous and
interconnecting the discontinuous imperforate portions, said
continuous foraminous portions comprising at least 10 percent of
the total area of the backing means, said foraminous portions
having a plurality of protuberances and troughs alternating across
the surface thereof in both the longitudinal and transverse
directions, the tops of said protuberances rising above the bottoms
of said troughs by a distance of at least .005 inch, the width of
each trough being at least 0.025 inch, each of said discontinuous
imperforate protions extending along the surface of the backing
means a distance at least about twice the horizontal distance from
the center of one of said troughs to the center of the trough
immediately adjacent and parallel to it, and each pair of
immediately adjacent discontinuous imperforate portions spanning
between them at least one of said protuberances and at least part
of one of said troughs on each side of said one protuberance; means
for moving said backing means, with a layer of fibrous starting
material positioned thereon, through a rearranging zone; means for
projecting streams of rearranging fluid against said fibrous layer
substantially uniformly and continuously across the surface thereof
to pass through said layer, some of said fluid streams striking
said imperforate portions of the backing means and other of said
fluid streams striking said protuberances on the backing means, all
to be deflected thereby in sidewise directions and all of said
fluid streams, together with other streams of fluid that do not
strike the backing means, passing through and beyond said
foraminous portions of the backing means; and means to apply vacuum
on the side of said backing means opposite to said fibrous layer to
assist in moving all said rearranging fluid through the fibrous
layer and in rearranging the fibers of said layer.
2. The apparatus of claim 1 in which each of said discontinuous
imperforate portions of the backing means rises above the plane of
the tops of said foraminous portions of the backing means by a
distance of at least 1/64 inch, with the central portion of said
discontinuous portion rising higher than the edge portions
thereof.
3. The apparatus of claim 1 in which the width of each of said
discontinuous imperforate portions of the backing means, measured
in each direction, is equal to at least about three times the
horizontal distance from the center of one of said troughs to the
center of the trough immediately adjacent and parallel to it.
Description
This invention relates to a method and apparatus for the production
of nonwoven fabrics, and more particularly to a method and
apparatus for the production of nonwoven fabrics from a layer of
fibrous material such as a fibrous web, in which the individual
fiber elements are capable of movement under the influence of
applied fluid forces, to form a fabric that contains rearranged
fibers defining a plurality of patterns of apertures or holes, or
other areas of low fiber density, that alternate and extend
throughout the fabric. Some of the rearranged fibers in the fabric
lie in yarn-like bundles of closely associated and substantially
parallel fiber segments that help to define the apertures (holes)
or other areas of low fiber density contained in the fabric.
BACKGROUND OF THE INVENTION
Various methods and apparatus for manufacturing apertured nonwoven
fabrics involving the rearrangement of fibers in a starting layer
of fibrous material have been known for a number of years. Some of
these methods and apparatus for the manufacture of such fabrics are
shown and described in U.S. Pat. No. 2,862,251, which discloses the
basic method and apparatus of which the present invention is a
specific form, and in U.S. Pat. Nos. 3,081,500 and 3,025,585.
The nonwoven fabrics made by the methods and apparatus disclosed in
the patents just mentioned contain apertures or holes or other
areas of low fiber density, out-lined by interconnected yarn-like
bundles of closely associated and substantially parallel fiber
segments. (The term "areas of low fiber density" is used in this
specification and claims to include both (1) areas in which
relatively few fibers are found in comparison to the rest of the
fabric, and (2) apertures (holes) that are substantially or
entirely free of fibers.)
One of the specific known methods for producing rearranged nonwoven
fabrics is to support a loose fibrous web or layer upon a permeable
backing member that has protuberances or "tapered projections"
spaced across its surface, with troughs or low areas between the
protuberances. Streams of rearranging fluid are applied
substantially uniformly and continuously over the entire surface of
the loose fibrous web or layer, and after the streams pass through
the fibrous material some of them strike the protuberances on the
backing means and are diverted in sidewise directions to cause
fiber segments to move from the area adjacent the high point of
each protuberance into the immediately adjacent troughs. All the
streams then pass through the openings in the permeable backing
means and leave the rearranging zone.
The effect of these fluid rearranging forces is to pack groups of
fiber segments into interconnected yarnlike bundles of closely
associated and substantially parallel fiber segments and to
position them in the troughs on the backing means so as to define a
pattern of areas of low fiber density throughout the resulting
nonwoven fabric.
In this prior art method, the backing member is uniformly permeable
throughout its area in order to provide an unimpeded route by which
the streams of rearranging fluid can be quickly carried away after
they have moved fiber segments from the protuberances into the
troughs of the backing means. Care is always taken in any fluid
rearrangement to avoid loss of web identity through "flooding"
(U.S. Pat. No. 2,862,251, col. 2, line 60 to col. 3, line 12), and
with the specific prior art method under discussion it is said to
be essential that the backing member be "permeable to the passage
of fluid from the applied streams, so that the fluid may pass
freely through the backing member and away from the layer of fibers
rather than having some or all of the fluid reflected back in the
same general direction from which it is applied" (U.S. Pat. No.
3,025,585, col. 2, lines 38-48).
The fiber segments rearranged by the prior art method referred to
are moved laterally only as indicated, which is no farther than
from the high point of a protuberance to the low point of an
immediately adjacent trough. This will usually be about one-half
the horizontal distance from the bottom of one trough or low point
to the bottom of the next.
SUMMARY OF INVENTION
I have now discovered that, unexpectedly, one can block off
substantial portions of the otherwise permeable backing or support
member in the prior art method just described, to interrupt and
impede the flow of rearranging fluid through the backing member,
and still not impede satisfactory rearrangement of the fibers of
the fibrous starting material by the protuberances on the backing
means into a nonwoven fabric containing yarn-like bundles of fiber
segments and having well defined apertures in a plurality of
patterns that alternate and extend throughout the fabric. Moreover,
contrary to the prior art method, the fiber segments that are
rearranged into yarn-like bundles of closely associated and
substantially parallel fiber segments are moved laterally for a
distance substantially greater than the distance between the high
point of a protuberance and the bottom of its immediately adjacent
trough or low point.
In the practice of this invention, the starting material is a layer
of fibrous material whose individual fibers are in mechanical
engagement with one another but are capable of movement under
applied fluid forces. The layer of fibrous starting material is
supported in a fiber rearranging zone that has an entry side and an
exit side and in which fiber movement in directions parallel to the
plane of the fibrous material is permitted in response to applied
fluid forces. The fiber rearranging zone is subdivided into barrier
regions that are arranged in a discontinuous pattern, and
deflecting regions that are continuous and lie between and
interconnect the barrier regions.
Streams of rearranging fluid, preferably water, are projected into
the fibrous starting material substantially uniformly and
continuously across its surface, in a direction perpendicular to
the fibrous layer at the entry side of the rearranging zone. The
streams of rearranging fluid are comprised of three categories --
first portions that pass through the deflecting regions of the
rearranging zone, second portions that pass through the barrier
regions, and third portions that pass through the deflection
regions but in a different manner than the first portions.
The first portions of the rearranging fluid are passed through the
initial part of the deflecting regions, as the layer of fibrous
starting material lies in said regions, toward a plurality of
dispersal points in the deflecting regions lying adjacent the exit
side of the rearranging zone. Each of these dispersal points is
surrounded by fiber accumulating zones. At least one dispersal
point and its associated fiber accumulating zones lie between each
barrier region and its adjacent barrier regions at all points
around the perimeter of the first mentioned barrier region.
At each dispersal point, the first portions of rearranging fluid
are deflected diagonally and downwardly away from the perpendicular
direction of their entry into the rearranging zone, and are moved
into the area immediately surrounding the dispersal point. This
movement of the rearranging fluid moves fiber segments lying
adjacent the dispersal point into the area around that point, and
positions them there in yarn-like bundles of closely associated and
substantially parallel fiber segments. Some of these yarn-like
bundles lie in fiber accumulating zones that are located in
peripheral portions of the deflecting regions, and some lie in
accumulating zones that are located between immediately adjacent
dispersal points.
The second portions of rearranging fluid are passed through the
parts of the layer of fibrous starting material that lie in the
barrier regions of the fiber rearranging zone, and cause movement
of at least some segments of the fibers in those regions transverse
to the direction of travel of the projected streams. At the exit
side of the rearranging zone, the passage of these second portions
of rearranging fluid out of the parts of the fibrous layer that lie
in the barrier regions is blocked, and the fluid is deflected
sidewise into the deflecting regions of the rearranging zone. This
movement of the rearranging fluid moves fiber segments that lie in
the barrier regions into at least some of the yarn-like bundles of
closely associated and substantially parallel fiber segments
mentioned above.
The first and second portions of the rearranging fluid that have
been deflected as described are then actively mingled, and the
intermingled fluid is passed out of the fiber rearranging zone
through spaced exits in the deflecting regions at the exit side of
the rearranging zone. At the same time, third portions of fluid are
intermingled with the first and second portions, to be passed out
of the same exits. The third portions of fluid are projected into
the fibrous starting material and are moved to the exits referred
to without passing through a dispersal point or a barrier
region.
To assist in moving all the rearranging fluid through the layer of
fibrous starting material and in rearranging the fiber segments of
that layer, a vacuum is applied at the exit side of the fiber
rearranging zone.
The result of application of the fluid rearranging forces just
described is to form a nonwoven fabric having yarn-like bundles of
fiber segments that define a first pattern of areas of low fiber
density arranged in accordance with the pattern of arrangement of
the barrier regions of the rearranging zone, and a second pattern
of areas of low fiber density arranged in accordance with the
pattern of arrangement of the dispersal points in the deflecting
regions of the fiber rearranging zone.
In one form of the method and apparatus of this invention, the
fibrous starting layer is supported on backing means having
imperforate portions arranged in a discontinuous pattern, with
continuous foraminous portions lying between and interconnecting
the imperforate portions. The continuous foraminous portions of the
backing means have protuberances and troughs alternating across the
surface of such portions in both the longitudinal and transverse
directions.
Each discontinuous imperforate portion extends along the surface of
the backing means in each direction for a distance at least about
twice the horizontal distance from the bottom of one of said
troughs in the foraminous portion of the backing means to the
bottom of the trough immediately adjacent and parallel to it. This
doubles the average distance fiber segments must be moved laterally
to bring them into yarn-like bundles in adjacent troughs of the
backing means. By the same token, it multiplies by four times the
quantity of fluid that must be disposed of in any area lying
between adjacent troughs, while increasing by only two times the
perimeter of that area out of which the fluid flows in order to
leave the rearranging zone.
Each imperforate portion of the backing means may, if desired, rise
above the plane of the tops of the foraminous portions of the
backing means, with the central portions of the imperforate member
rising higher than the edge portions thereof. However, it is not
necessary that the imperforate portions constitute "tapered
projections" as in the prior art method mentioned above, and if
desired they may even be flush with the tops of the foraminous
portions of the backing means and fiber arrangement is still
achieved.
In the practice of this invention, streams of rearranging fluid,
preferably water, are applied substantially uniformly and
continuously across the surface of the layer of fibrous starting
material as it is supported on the backing means just described.
The streams pass through the fibrous layer and strike the backing
or support means, some striking the imperforate portions of the
backing means and others striking the protuberances on the
foraminous portions of the backing means. In either case, the
streams are deflected in sidewise directions and join other streams
of rearranging fluid that pass through the openings of the
continuous foraminous portions of the backing means without
striking the backing means.
To assist in moving the rearranging fluid through the layer of
fibrous starting material and in rearranging the fibers of that
layer, a vacuum is applied on the opposite side of the backing
means from the fibrous starting material.
As the various streams of rearranging fluid follow their courses
described, they cause fiber segments that overlie the protuberances
on the foraminous portions of the backing means to move into
troughs lying between those protuberances, and to be positioned
there in yarn-like bundles of closely associated and substantially
parallel fiber segments. At the same time, other streams of
rearranging fluid cause fiber segments that overlie the
discontinuous imperforate portions of the backing means to be moved
into surrounding areas of the fibrous layer, where they are also
consolidated into yarn-like bundles of fiber segments, in troughs
located in peripheral portions of the foraminous portions of the
backing means.
The resulting nonwoven fabric has a first pattern of areas of low
fiber density, defined by yarn-like bundles of fiber segments, that
corresponds to the pattern of the discontinuous imperforate
portions of the backing means. In addition, the fabric has a second
pattern of areas of low fiber density, defined by yarn-like bundles
of fiber segments positioned in the troughs between adjacent
protuberances on the foraminous portions of the backing means, that
corresponds to the pattern of the protuberances on those foraminous
portions of the backing means.
The fibrous starting material used with the method and apparatus of
this invention is comprised of closely intertwined and
interentangled fibers arranged (depending on the degree of fiber
orientation in the layer) in a more or less helter-skelter fashion.
When streams of rearranging fluid are projected against such a
fibrous material supported on partially imperforate backing means
of the kind employed in this invention, one would expect that the
streams would simply mat the interentangled fibers down against the
imperforate portions of the backing means, so that there would be
no fiber rearrangement produced there at all. This effect would be
expected to be even more pronounced when each discontinuous
imperforate portion of the backing means is of such a size that it
extends in each direction along the surface of the backing means
for a distance at least twice the horizontal distance between
immediately adjacent troughs on that surface, for in that situation
the streams of rearranging fluid would strike an even greater
obstacle to a rapid exit from the fiber rearranging zone.
Surprisingly, it has been found that obstructing the flow of fluid
rearranging streams away from the rearranging zone by providing
discontinuous imperforate portions of substantial size in the
backing means does not have any undesirable result, nor prevent the
production of excellent apertured rearranged nonwoven fabrics
having a plurality of patterns extending throughout the fabric.
FURTHER DESCRIPTION OF INVENTION
The basic method and apparatus of this invention are shown and
described fully in my U.S. Pat. No. 2,862,251, issued Dec. 2, 1958.
Full particulars of the basic invention as disclosed in that patent
are incorporated in this application by reference, although some of
those particulars are repeated here. In addition, the specific
feature peculiar to the method and apparatus of the present
invention -- which is the provision of discontinuous barrier
regions (defined, for example, by spaced imperforate members on a
backing means) to block and deflect portions of the streams of
rearranging fluid at the exit side of a fiber rearranging zone the
remainder of which is comprised of continuous deflecting regions
including dispersal points surrounded by fiber accumulating zones
(for example, foraminous portions of a backing means having
alternating protuberances and troughs) -- is described in detail in
this application.
Starting material. The starting material used with the method or
apparatus of this invention may be any of the standard fibrous webs
such as oriented card webs, isowebs, air-laid webs, or webs formed
by liquid deposition. The webs may be formed in a single layer, or
by laminating a plurality of the webs together. The fibers in the
web may be arranged in a random manner or may be more or less
oriented as in a card web. The individual fibers may be relatively
straight or slightly bent. The fibers intersect at various angles
to one another such that, generally speaking, the adjacent fibers
come into contact only at the points where they cross. The fibers
are capable of movement under forces applied by fluids such as
water, air, etc.
To produce a fabric having the characteristic hand and drape of a
textile fabric, the layer of starting material used with the method
or apparatus of this invention may comprise natural fibers such as
cotton, flax, etc.; mineral fibers such as glass; artificial fibers
such as viscose rayon, cellulose acetate, etc.; or synthetic fibers
such as the polyanides, the polyesters, the acrylics, the
polyolefins, etc., alone or in combination with one another. The
fibers used are those commonly considered textile fibers; that is,
generally fibers having a length from about 1/4 inch to about 2 to
21/2 inches.
Satisfactory products may be produced in accordance with this
invention from starting webs weighing between 80 grains per square
yard to 2,000 grains per square yard or higher. With heavier web
weights, as discussed below, the difference in elevation between
the dispersal points and the fiber accumulating zones in the
deflecting region of a fiber rearranging zone (for example, the
protuberances and troughs, respectively, on the foraminous portions
of a backing means) must be more pronounced in order to achieve the
bundling that is a necessary part of this invention.
Continuous foraminous portions of backing means. As already
indicated, in one form of this invention a backing means is
employed that has imperforate portions arranged in a discontinuous
pattern to provide barrier regions in the fiber rearranging zone,
with continuous foraminous portions lying therebetween. The
continuous foraminous portions of the backing means are provided
throughout their surfaces with a plurality of protuberances and
troughs alternating across those surfaces, and thus comprise
deflecting regions containing dispersal points each of which is
surrounded by fiber accumulating zones.
As illustrated in the drawings below, for improved results the tops
of the protuberances on the foraminous portions of the backing
means rise above the bottoms of the immediately adjacent troughs by
a distance equal to at least about three times the average diameter
of the fibers in the layer of fibrous starting material or at least
0.005 inch. Preferably, the distance is equal to about ten times
the average diameter of those fibers, especially when the web
weight of the fibrous starting material is of the order of 800
grains per square yard or higher. It also becomes more important to
have prominent protuberances on the continuous foraminous portions
of the backing means the greater is the area of the discontinuous
imperforate portions of the backing means, since a large
imperforate portion increases the number of loose fiber ends that
will be washed off those imperforate portions to be added to the
fibrous web already lying above the foraminous portions of the
backing means.
The fibrous starting material used with the method and apparatus of
this invention is comprised of closely intertwined and
interentangled fibers arranged (depending upon the degree of fiber
orientation in the layer) in a more or less helter-skelter fashion.
Some of the fibers of the starting material will by random chance
lie generally parallel to the troughs on the continuous foraminous
portions of the backing means over which they lie, but the great
majority of the fibers will lie at an angle to the longitudinal
axes of the troughs, and a substantial number of these will lie at
angles of 45.degree. or more to such an axis.
In the practice of this invention, the movement of fiber segments
into closer association and substantial parallelism with each other
in yarn-like bundles in the troughs on the continuous foraminous
portions of the backing means is more likely to occur with those
fiber segments in the starting material that already lie only a
relatively few degrees away from a position parallel to the
longitudinal axis of a trough. To put it the other way, this type
of movement is more difficult the greater the angle between a given
fiber segment and the axis of the trough, and when fiber segments
lie at too great an angle to the longitudinal axis of a trough,
they simply continue to lie at that angle, matted down against the
backing means by the force of the rearranging fluid. For the
greater the angle between the fiber segment and the trough axis,
the shorter is the portion of the fiber that bridges the trough,
and the more difficult it is for the rearranging fluid forces to
get a "purchase" on the fiber segment to turn it around into a
position parallel with the trough axis.
Likewise, the narrower the troughs are on the foraminous portions
of the backing means, the more difficult it is for the rearranging
fluid forces to get a "purchase" on the short portion of the fiber
segment that bridges the trough, to swing that segment around into
a position parallel to the axis of the trough, to be consolidated
there to form a yarn-like bundle with other similarly positioned
fiber segments. The force of the vacuum assist employed with this
invention is of course added to the force of the other rearranging
fluid. with the use of a vacuum assist, the distance between
immediately adjacent protuberances on the backing means, which
determines the width of a trough from the top of one side to the
other, is ordinarily equal to at least about 15 times the average
diameter of the fibers of the fibrous starting material. or at
least 0.025.
The minimum spacing of protuberances just mentioned, which affects
the width of the troughs lying between immediately adjacent
protuberances, also assists in providing good visual resolution
between various yarn-like bundles of fiber segments in the fabric
resulting from the practice of this invention. For if the
protuberances are too closely spaced and the troughs between them
are too narrow, yarn-like bundles of fiber segments may be
accumulated in the troughs but will not be discernible one from the
other, because each one merges into the next adjacent similar
bundle of fiber segments. If the web weight of the fibrous starting
material is high, the distance between immediately adjacent
protuberances on the foraminous portions of the backing means
should be increased, or otherwise the yarn-like bundles of fiber
segments will be masked out by the same merging phenomenon just
mentioned.
The continuous foraminous portions of the backing means are
sufficiently wide that, with the appropriate web weight in the
starting material, good formation of yarn-like bundles of fiber
segments can be effected above those foraminous portions. Thus,
each continuous foraminous portion has a width at its narrowest
part sufficient to include at least one protuberance and a trough
on each side of the protuberance. This minimum width for each
continuous foraminous portion of the backing means produces a
minimum of one well defined hole or other area of low fiber density
corresponding to the protuberance on the backing means, with
yarn-like bundles of fiber segments positioned in the troughs
surrounding the protuberance.
There is no maximum limit on the width of the foraminous portions
of the backing means. That dimension is determined only by the
pattern desired in the nonwoven fabric to be produced. Thus, the
width of a continuous foraminous portion may be as much as five or
10 times the horizontal distance between adjacent troughs, or even
more.
The foraminous portions of the backing means used in this invention
are of sufficient size to occupy together at least about 10
percent, and preferably about 30 percent or more, of the total area
of the backing means.
Discontinuous imperforate portions of backing means. In plan view,
the discontinuous imperforate portions of the backing means may
have any shape desired i.e., circular, oval, diamond, square,
crescent, half moon, lace-like, free form, etc.
Each discontinuous imperforate portion of the backing means extends
along the surface of the backing means a distance equal to at least
about two times, and preferably three times, the horizontal
distance from the center of one of the troughs on the backing means
(i.e., a fiber accumulating zone) to the center of the trough
immediately adjacent and parallel to it. If desired, this dimension
of a discontinuous imperforate portion may be as much as five times
the horizontal distance between the center of adjacent troughs, or
even more.
The maximum dimension of each discontinuous portion may be greater
than the average length of the fibers in the fibrous starting
material, and all the fibers may still be moved off those
imperforate portions into surrounding areas of the fibrous layer.
However, the larger the dimensions of the discontinuous imperforate
portions of the backing means, the more likely it is that some
fiber segments will not be moved off those imperforate portions
during fiber rearrangement but will remain there to lie in areas of
low fiber density in the resulting fabric that correspond to the
discontinuous imperforate portions of the backing means. Control of
fiber movement is thus more effective if the maximum dimension of
each discontinuous imperforate portion is substantially less than
the average fiber length, for example, not more than 1 inch maximum
dimension, and preferably not more than 1/8 inch to 1/2 inch
maximum dimension, when fibers having an inch-and-a-half staple
length are employed.
If one dimension of a discontinuous imperforate portion of the
backing means is made smaller, the other may be increased. If the
imperforate portion is longer than it is wide, and the longer
dimension extends in the direction of fiber orientation in the
layer of fibrous starting material, fiber segments will be moved
off the imperforate portion more readily. On the other hand, if the
larger dimension of such an imperforate portion of the backing
means extends perpendicular to the direction of fiber orientation,
there will be more tendency for bridging of fibers across the
imperforate portion of the backing means to occur.
Improved results are obtained if each discontinuous imperforate
portion of the backing means, whatever its precise shape may be, is
a fairly compact area having a maximum dimension not much greater
than its smallest dimension. Thus, improved results are produced if
the maximum dimension of each discontinuous imperforate portion is
no greater than about four times its minimum dimension and still
further improvement is produced if the maximum dimension is no more
than about one-and-a-half times the minimum dimension of each such
portion.
In any event and regardless of all other factors, all loose ends of
fibers in the layer of fibrous starting material that are
positioned above the imperforate portions of the backing means will
be washed off those imperforate portions by the fluid rearranging
forces applied to the fibrous material.
The discontinuous imperforate portions of the backing means may be
flush with the plane of the top surfaces of the foraminous portions
of the backing means, but for improved results they rise at least
by about one sixty-fourth inch above the plane of that surface, and
preferably by about one thirty-second inch or one-sixteenth inch
for starting fibrous webs having web weights in the range of from
about 100 to about 1,000 grains per square yard. The height of the
imperforate portions may be even greater without interfering with
fiber rearrangement, but too great a height for these members may
interfere with removal of the rearranged fabrics.
When relatively heavy starting webs of fibrous material are
employed, a greater height for the discontinuous imperforate
portions of the backing means produces clearer formation of areas
of low fiber density in the resulting fabric. In other words,
increased height for the discontinuous imperforate portions
produces more pronounced formation of yarn-like bundles of fiber
segments at the periphery of the areas of low fiber density which
are formed in the resulting fabric above the imperforate portions
of the backing means.
The discontinuous imperforate portions of the backing means should
have walls that are vertical or taper out in a downward direction.
The edges are preferably slightly rounded, but not excessively so.
In any case, the top of the discontinuous portions should be
smooth, in order not to interfere with fiber rearrangement.
Rearranging fluid. The rearranging fluid for use with this
invention is preferably water or similar liquid. It may also be
other fluids such as a gas, as described in my U.S. Pat. No.
2,862,251.
Application of vacuum. The vacuum applied to the opposite side of
the backing means simultaneously with the application of fluid
rearranging forces to the fibrous starting layer is of the order of
about 1 inch to about 4 inches of mercury, preferably about 2
inches of mercury.
Additional vacuum may be used to advantage after the rearranged
fabric has moved out of the rearranging zone, in order to help
remove excess liquid from the fabric before the fabric is removed
from tha backing means.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully described in connection with the
accompanying drawing, in which:
FIG. 1 is a diagrammatic showing in elevation of one type of
apparatus that may be employed in the present invention.
FIG. 2 is an enlarged diagrammatic plan view of a portion of a
backing means that can be used in the apparatus of FIG. 1.
FIG. 3 is a cross sectional view taken along the line 3--3 of FIG.
2.
FIG. 4 is an enlarged fragmentary diagrammatic plan view of one of
the foraminous portions of the backing means of FIG. 2.
FIG. 5 is a cross sectional view taken along line 5--5 of FIG.
4.
FIG. 6 is a cross sectional view taken along line 6--6 of FIGS. 4
and 5.
FIG. 7 is a schematic perspective representation of the paths
followed by various streams of rearranging fluid as they pass
through the foraminous member shown in FIGS. 4 through 6.
FIG. 8 is a schematic plan representation of the paths followed by
the streams of rearranging fluid shown in perspective in FIG.
7.
FIG. 9 is a photograph of a nonwoven fabric made in accordance with
the present invention, shown in the original drawing at actual
size.
FIG. 10 is a photomicrograph of the nonwoven fabric of FIG. 9,
shown at an original enlargement of fibe times.
DETAILED DESCRIPTION OF SPECIFIC FORM OF THE INVENTION
FIG. 1 shows one form of apparatus that may be used in accordance
with the present invention.
In this apparatus, horizontal frame members 2 are supported by legs
3 and 4. At the feed end of the machine (on the left hand side of
FIG. 1), a pair of vertical frame members 5 extend upwardly above
horizontal frame members 2, with a pair of wet-out rolls 6 and 7
rotatably mounted between them. Wet-out roll 6 is partially
immersed in a water pan 8, and its shaft 9 is journalled in
bearings (not shown) fixed to vertical frame members 5. Bearings
10, in which shaft 11 of wet-out roll 7 is journalled, are slidably
mounted on vertical frame members 5.
The vertical position of wet-out roll 7 is adjustable, and is
regulated by hydraulic positioning cylinders 13 mounted on the top
of each vertical frame member 5. In this way, the pair of wet-out
rolls 6 and 7 cooperate to control the moisture content of a web or
layer of fibrous material, of a type such as mentioned above as
being a suitable starting material, which is fed through the nip
between the wet-out rolls. Preferably the moisture content of the
layer of fibers as it is moved from the wet-out rolls is in the
neighborhood of from 109 150 to 200 percent. (The term "percent
moisture," when used in this specification, refers to percentage of
moisture by weight of the dry web.)
The layer of fibers moves from the nip of the wetout rolls to the
fiber rearranging zone of the apparatus to effect the rearrangement
of the fibers in the starting web or layer 15, to produce a
rearranged fibrous web or layer 15' having a plurality of patterns
of holes or other areas of low fiber density as described above.
Thus the starting layer of fibers moves from the wet-out rolls to
be supported on a backing means in the form of endless belt 16 (to
be described in detail below), which extends around a pair of
parallel rolls 17, 18 rotatably mounted adjacent opposite ends of
the frame. Each of the rolls 17, 18 is mounted on a shaft 19, the
ends of which are journalled in bearings 20 carried on horizontal
frame members 2. Conventional driving means (not shown) are
connected to either one of shafts 19.
A water pipe 21, mounted in any suitable manner, supports a pair of
headers 22 above the upper reach of endless belt 16. Each header
extends transversely of belt 16, and has a row of jet nozzles 23 to
provide water sprays across the width of that belt.
A pair of suction boxes 24 are mounted on and extend transversely
across frame members 2 between the rolls 17 and 18 which carry
endless belt 16, with one of the boxes located directly beneath
each row of jet nozzles 23. Each suction box is closed on all sides
except for an opening 25 to which a vacuum line 26 is connected,
and a slot or group of perforations 27 which extend across top wall
28 of the suction box. The top wall of each suction box is
positioned adjacent the underside of the upper reach of endless
belt 16.
Nonwoven fabric 15', after rearrangement but before reaching the
position where endless belt 16 starts to track around roll 18, is
lifted off the belt by causing it to pass upwardly and over a
horizontal cylindrical doffing member 29a which extends
transversely of the machine and is supported at its ends in the
side frames. The fabric then passes downwardly and around through
the nip between guide rolls 29b and 29c on its way to a suitable
drying area (not shown). Guide rolls 29b and 29c are parallel to
doffing member 29a, and like it are supported at their ends in the
side frame members of the machine.
Backing means. Endless belt or backing means 16, as shown in FIG.
2, has a continuous pattern of foraminous portions 30 and a
discontinuous pattern of imperforate portions 31. In FIG. 2, the
imperforate portions are round and arranged such that four of them
lie in a square pattern over the surface of the backing means, the
remainder of the member being foraminous. As already indicated
above, the imperforate portions of the backing member may have any
shape desired. They may also be arranged in any discontinuous
pattern over the backing means; i.e., they may be aligned
longitudinally and/or transversely, staggered, etc.
FIG. 3 shows a cross section of the backing means of FIG. 2. As
seen, each discontinuous imperforate portion 31 of backing means 16
has a curved top surface that rises slightly above the top surface
of foraminous portions 30 of the backing means. Because of the
curved top surface, central portion 32 rises above edge portions 33
of discontinuous imperforate portions 31 of the backing means.
Extreme edge portions 34 are slightly rounded.
Foraminous portions 30, as shown in FIGS. 4 through 6, are formed
of a coarse woven screen, preferably metal. In the embodiment
shown, wires 40 running vertically in FIG. 4 are straight, while
wires 41 running horizontally in that figure weave alternately over
and under wires 40. Protuberances 42 are present throughout
foraminous portion 30 as the topmost part of each "knee" of a given
strand 41 of the screen that is formed as the strand weaves over
and under the strands 40 that lie perpendicular to it.
As a given strand 41 slants downward to pass under a strand 40
perpendicular to it, it crosses two other strands 41 disposed on
either side of it, as those strands slant upward to pass over the
same perpendicular strand that the given strand will pass under.
Each series of such "crossing points" 43 forms a trough, such as
trough 44 in FIGS. 4 and 5, that lies between adjacent
protuberances 42. The effective cross sectional shape of troughs
44, as can be best seen in FIG. 5 (which shows a cross section of
element 30 of which a plan view is given in FIG. 4), is
substantially an inverted triangle.
A series of slightly deeper troughs 45 is formed between adjacent
protuberances 42 extending at right angles to troughs 44. As best
seen in FIG. 6, the bottom of each trough 45 is formed by portions
of straight strands 40, with successive protuberances 42 on each
side of the trough forming the tops of the trough. As seen in FIG.
6, the effective cross sectional shape of troughs 45 may be
characterized as a shallow U-shape.
As shown in FIG. 4, troughs 44 and protuberances 42 alternate in
one direction across the surface of foraminous portion 30 of
backing means 16. FIG. 4 also shows that troughs 45 and
protuberances 42 alternate in a direction perpendicular to troughs
44. Hence a plurality of troughs and a plurality of protuberances
alternate in both the longitudinal and transverse directions across
the surface of foraminous portion 30 of backing means 16.
To produce satisfactory rearrangement of fibers into yarn-like
bundles of closely associated and substantially parallel fiber
segments positioned in troughs 44 and 45, the vertical distance
between the tops of protuberances 42 and the bottoms of the
immediately adjacent troughs should be at least about three times,
generally no more than about 30 times, and preferably about 10
times, the average diameter of the fibers in the layer of fibrous
starting material. For troughs 44, this distance is the vertical
distance indicated in FIG. 5 by the pair of dashed lines that pass,
respectively, through the tops of protuberances 42 and the crossing
points 43 that define the troughs. The vertical distance from the
bottom of each trough 45 to the tops of protuberances 42, on the
other hand, is somewhat larger, being shown by FIGS. 5 and 6 to be
equal to the diameter of a strand 41.
In the embodiment shown, each protuberance 42 has a directional
effect in one direction because of its proximity to other similar
protuberances on foraminous portion 30 of the backing means, and in
the other direction for the same reason and in addition because of
the cross sectional shape of the protuberance. Thus, each
protuberance 42 is effective in both the longitudinal and
transverse directions. As an example, the protuberance 42 to which
the designator line runs in the upper left hand corner of FIG. 4,
through cooperation with the protuberance 42 to which the
designator line runs in the left central part of the bottom of that
same figure, is effective as a protuberance that defines one wall
of trough 44 running vertically down the middle of the figure. At
the same time, the first named protuberance 42, through copperation
with protuberance 42 to which the designator line runs in the upper
right hand part of FIG. 4, is effective as a protuberance that
defines one wall of trough 45 running horizontally across the
middle of the figure. In addition, the cross sectional shape of
each protuberance 42 (as best seen in FIGS. 4 and 6) exerts a
directional effect on the fibers of the fibrous starting material
by its sharper definition of the side walls of each trough
extending horizontally across FIG. 4, i.e., on the side walls of
each trough 45.
At the point of closest spacing of each pair of immediately
adjacent barrier regions or discontinuous imperforate portions 31
of backing means 16, each continuous deflecting region or
interconnecting foraminous portion 30 is wide enough to include at
least one dispersal point or protuberance 42 and a fiber
accumulating zone or trough 44 or 45 on each side thereof. In the
embodiment of FIGS. 2 and 3, each pair of imperforate portions 31
include between them at their point of closest spacing about five
protuberances 42 and their associated troughs or fiber accumulating
zones.
Three portions of rearranging fluid. The directions the projected
streams of rearranging fluid take as they move into and through the
fibrous web determine the types of forces applied to the fibers
and, in turn, the extent or rearrangement of the fibers. Since the
directions the streams of rearranging fluid take as thy move
through the fibrous layer are determined in part by the pattern of
the solid wires that make up foraminous portions 30 of backing
means 16, and in particular the pattern of protuberances and
troughs distributed across the surface of foraminous portions 30,
it follows that the pattern of these areas helps determine the
patterns of holes or other areas of low fiber density in the
resultant fabric.
As is seen from FIG. 4, first portions of the streams of
rearranging fluid that have been projected into the fibrous web
strike the wires of woven screen 30, at protuberances 42 or at
other portions of the wire, and are deflected sidewise before they
pass out of the rearranging zone through openings 46. The streams
of rearranging fluid that strike protuberance 42 in the upper left
hand part of FIG. 4, for example, leave the fiber rearranging zone
through openings 46a, 46b, 46c and 46d in the respective sectors or
quadrants of the area surrounding that protuberance.
FIGS. 2 and 3 show that second portions of the rearranging fluid
projected into the layer of starting material strike discontinuous
imperforate portions 31 of backing means 16, and are deflected
sidewise into the areas above foraminous portions 30, where they
are mingled with the first portions of rearranging fluid and are
passed out of the rearranging zone though openings 46.
Third portions of the rearranging fluid projected into the fibrous
web pass directly through openings 46 in foraminous backing portion
30, without being deflected either by protuberances 42 or
imperforate portions 31.
Flow of first portions of rearranging fluid through deflecting
regions. The dotted lines in FIGS. 5 and 6 give a schematic showing
of the path followed by a stream of rearranging fluid 47 that is
directed into the layer of fibrous starting material, in a
direction perpendicular to that layer, to strike protuberance 42 in
the upper left hand corner of FIG. 4. As is seen, the stream of
fluid is deflected downwardly and outwardly away from its
perpendicular direction of entry into the fiber rearranging zone,
and then moves out of the rearranging zone through the openings
between wires 40 and 41.
The flow of streams of rearranging fluid after being deflected
sidewise upon striking protuberances 42 of foraminous portions 30
of backing means 16 produces sets of counteracting components of
force that act in the plane of the web until the fluid passes out
through the foramina in portions 30. The counteracting fluid forces
in each of these sets work in conjunction with one another to
rearrange fiber segments into yarn-like bundles positioned in
troughs 44 and 45 of portion 30 of backing means 16. Some of these
yarnlike bundles of fiber segments lie in fiber accumulating zones
in peripheral portions of foraminous portions 30 adjacent
discontinuous imperforate portions 31 of backing means 16, while
some lie in troughs or fiber accumulating zones between one
protuberance 42 and another protuberance that is parallel and
immediately adjacent to it.
When the layer of fibrous starting material is first positioned in
that part of the fiber rearranging zone located above foraminous
portion 30 of backing means 16, and before a rearranging fluid has
been directed into the layer, the fibrous web of course lies upon
the tops of protuberances 42. After fiber arrangement has proceeded
under the impact of the streams of rearranging fluid, the fibers
are moved down the sloping sides of protuberances 42 into troughs
44 and 45. At this juncture, the layer of rearranged fibers that
comprises the nonwoven fabric ordinarily lies largely, if not
altogether, below the tops of protuberances 42.
FIGS. 7 and 8 provide schematic representations of the flow of
streams of rearranging fluid 47 that has been described in
connection with FIGS. 4 through 6. As explained above, in the
practice of this invention the layer of fibrous starting material
is supported in a fiber rearranging zone in which fiber movement in
directions parallel to the plane of the fibrous material is
permitted in response to applied fluid forces. The fiber
rearranging zone has an entry side and an exit side, and is
subdivided into barrier regions 31 arranged in a discontinuous
pattern and deflecting regions 30 that are continuous and lie
between and interconnect the barrier regions. FIGS. 7 and 8 depict
a part of a deflecting region 30.
In FIGS. 7 and 8, the fiber rearranging zone is indicated as being
defined by foraminous portion 30 of backing means 16. Streams of
rearranging fluid are projected into the fibrous layer as thus
supported, in a direction perpendicular to said layer,
substantially uniformly and continuously across the surface of the
layer. In FIGS. 7 and 8, streams 47 represent first portions of
those rearranging streams that take a particular path through the
fiber rearranging zone.
First portions 47 of the rearranging fluid are passed through
initial part 48 of the rearranging zone, as the fibrous layer lies
in the zone. The streams of fluid 47 are passed toward dispersal
points 42 lying adjacent the exit side of the rearranging zone, two
of which dispersal points are shown for illustrative purposes in
FIGS. 7 and 8.
At each dispersal point 42, streams of rearranging fluid 47 are
deflected diagonally and downwardly away from the perpendicular
direction of entry of streams 47 into the fibrous starting
material, into the area immediately surrounding each dispersal
point 42. In FIGS. 7 and 8, fluid stream 47 that is directed toward
dispersal point 42 in the upper left hand portion of FIG. 8 is
directed upon deflection into sectors or quadrants 46a, 46b, 46c
and 46d of the area surrounding that dispersal point.
A few of the fiber segments of the fibrous starting material that
lie in deflecting region 30 of the rearranging zone remain, after
treatment with streams of rearranging fluid, in substantially the
positions they occupied by random chance in the starting layer.
Most of the fiber segments lying in the deflecting region, however,
are moved by the deflection of rearranging fluid just described
into the area surrounding that dispersal point 42 at which each
fluid stream 47 was deflected.
The fiber segments moved by deflected streams of rearranging fluid
47 are positioned in yarn-like bundles of closely associated and
substantially parallel fiber segments in fiber accumulating zones
44 and 45 in the area surrounding each dispersal point 42. As an
example, fiber segments that are moved so that they extend between
areas 46a and 46b of FIG. 8 are positioned there in fiber
accumulating zone 44 which extends vertically in that figure
between the two dispersal points 42, lying adjacent each other,
that are shown in FIG. 8. Likewise, fiber segments that are moved
so that they extend between areas 46b and 46c are positioned in
fiber accumulating zone 45 which extends horizontally in FIG. 8,
and so on. Fiber accumulating zones 44 and 45 correspond to troughs
44 and 45 shown in FIGS. 4 through 6. The yarn-like bundles of
fiber segments positioned in the fiber accumulating zones form a
pattern of yarn-like bundles corresponding to the pattern of the
fiber accumulating zones, which in turn is determined, among other
things, by the position of the various dispersal points 42
throughout the fiber rearranging zone.
The deflected portions of rearranging fluid 47 are then passed out
of the fiber rearranging zone through spaced exits such as 46a
through 46d, and similar exit areas, in FIGS. 7 and 8. At the same
time, other portions of rearranging fluid that were projected into
the layer of fibrous starting material, for example those portions
entering the entry zone in direct registry with exit 46b, are moved
directly to and through the exits on the exit side of the
rearranging zone without passing through a dispersal point 42 to be
deflected from the perpendicular direction at which they entered
the fibrous starting layer.
In the embodiment shown diagrammatically in FIGS. 4 through 6 and
in the schematic representations of FIGS. 7 and 8, the spaced exits
on the exit side of the rearranging zone are located in the fiber
accumulating zones.
Flow of second portions of rearranging fluid through barrier
regions. The directions taken by the second portions of the streams
of rearranging fluid, which are projected into the fibrous starting
material lying in the barrier regions of the fiber rearranging
zone, are of course also important. The directions those portions
of the rearranging fluid take as they move into and through the
fibrous web determine the types of forces applied to the fibers
that lie in the barrier regions, and, in turn, help determine the
extent of rearrangement of the fibers throughout the barrier
regions, and thus help determine the pattern of holes or other
areas of low fiber density in the resultant fabric.
The second portions of the rearranging fluid which are projected
into a barrier region -- for example, each part of the rearranging
zone overlying an area 31 where backing means 16 is imperforate --
are deflected sidewise out of the barrier region into adjacent
deflecting regions. Thus, such streams strike imperforate portions
31 in FIG. 2, to be deflected sidewise and effect movement of fiber
segments transverse to the direction of travel of the projected
streams.
This fluid flow pushes fiber segments off imperforate portions 31
to position the segments in the above mentioned yarn-like bundles
of fiber segments in areas adjacent the periphery of those
imperforate portions, and elsewhere in the deflecting regions
overlying foraminous portions 30 of the backing means. In some
instances, the fluid may push all fiber segments off the
imperforate portions of the backing means, while in other instances
some fiber segments are left to span those portions.
Flow of third portions of rearranging fluid through deflecting
regions. As indicated above, the passage of rearranging fluid
through the fiber rearranging zone and the layer of fibrous
starting material supported therein is completed by the flow of
third portions of the fluid through the deflecting regions of the
rearranging zone.
As is seen from FIG. 4, third portions of rearranging fluid that
are projected into the fibrous web in a direction perpendicular to
the plane of the web (i.e., the plane of the drawing in that
figure) pass through the fibrous layer and, after being
intermingled with the first and second portions of fluid discussed
above, pass directly out of the fiber rearranging zone through
spaced exits such as openings 46a, 46b, 46c and 46d. These third
portions of fluid do not strike protuberances 42 to be deflected
sidewise, and thus do not pass through any dispersal points in the
deflecting region. Likewise, since they do not enter the barrier
regions of the fiber rearranging zone, they do not strike
imperforate portions 31 of backing means 16.
The rearranged web or fabric produced by the practice of this
invention may be treated with an adhesive, dye or other
impregnating, printing, or coating material in a conventional
manner. For example, to strengthen the rearranged web, any suitable
adhesive bonding materials or binders may be included in an aqueous
or non-aqueous medium employed as the rearranging fluid. Or an
adhesive binder may, if desired, be printed on the rearranged web
to provide the necessary fabric strength. Thermoplastic binders
may, if desired, be applied to the rearranged web in powder form
before, during or after rearrangement, and then fused to bond the
fibers.
The optimum binder content for a given fabric according to this
invention depends upon a number of factors, including the nature of
the binder material, the size and shape of the binder members and
their arrangement in the fabric, the nature and length of the
fibers, total fiber weight, and the like. In some instances,
because of the strength of the fibers used or the tightness of
their interentanglement in the rearranged web or fabric, or both
factors, no binder at all need be employed to provide a usuable
fabric.
The following is an illustrative example of the use of the method
and apparatus of this invention to produce a patterned nonwoven
fabric:
EXAMPLE
In apparatus as illustrated in FIG. 1, a web 15 of loosely
assembled fibers, such as may be obtained by carding, is fed
between wet-out rolls 6 and 7, and from there onto endless backing
means 16. The web weight is about 400 grains per square yard, and
its fiber orientation ratio approximately 7 to 1 in the direction
of travel. The web contains viscose rayon fibers approximately 1
9/16 inches long, of 11/2 denier.
Foraminous portions 30 of backing means 16 are comprised of a woven
metal screen of approximately 8 .times. 16 mesh or substantially
128 openings per square inch. The top of each protuberance 42 on
the backing means rises above the bottoms of troughs 44 immediately
adjacent to it by approximately 0.018 inch, or about 12 times the
0.0015 inch average diameter of the 11/2 denier fibers of the
starting material. They rise approximately 0.026 inch above the
bottoms of troughs 45, or about 18 times the average fiber
diameter.
The distance measured in one direction across foraminous portions
30 of backing means 16 between the top of one protuberance 42 and
the top of the protuberance immediately adjacent to it is about
0.063 inch, and in the other direction about 0.125 inch. These
distances are equal, respectively, to approximately 42 and 84 times
the average diameter of the fibers of the fibrous starting
material.
Discontinuous imperforate portions 31 of backing means 16 are
smooth round metal members of a diameter of approximately
one-fourth inch and having a cross sectional shape similar to that
shown in FIG. 3. They are distributed over the area of backing
means 16 in a diamond pattern, with a space of approximately
three-sixteenths inch from each portion 31 to the nearest other
portion 31 in a diagonal direction. Central portions 32 of elements
31 rise about 0.012 inch above the plane of the top surface of
continuous foraminous portions 30 of the backing means, and edge
portions 33 rise about 0.010 inch above that plane.
The distances between one fiber accumulating zone or trough and the
zone or trough immediately adjacent and parallel to it are the
same, in the two directions across foraminous portions 30, as the
distances between adjacent protuberances. Hence the 0.25 inch width
of each imperforate portion 31 is between about two and about four
times the distance between trough centers.
In the practice of this invention, water is projected from nozzles
23 against fibrous web 15 in a direction perpendicular to the plane
of the web, to pass through the fibrous layer and through backing
means 16.
After given portions of backing means 16 and fibrous web 15 pass
through the rearranging zone, in which streams of water are
directed against them as just described, the movement of the upper
reach of endless belt 16 (to the right as seen in FIG. 1) brings
the rearranged fabric to doffer roll 29a and guide rolls 29b and
29c, from whence it leaves the apparatus.
With the conditions indicated, good fiber rearrangement and
bundling are obtained, and an excellent nonwoven fabric such as
shown in the photomicrograph of FIG. 9, which has a plurality of
patterns of holes or other areas of low fiber density that
alternate and extend throughout the fabric, is produced.
Nonwoven fabric 50 of FIG. 9 is shown with an original enlargement
of five times in the photomicrograph of FIG. 10. As seen in the
latter figure, fabric 50 contains a first pattern of areas of low
fiber density 51, each of which overlies a discontinuous
imperforate portion 31 of backing means 16. Each area 51 is defined
by yarn-like bundles 52 of closely associated and substantially
parallel fiber segments, which lie in fiber accumulating zones
located in the peripheral portions of the deflecting regions of the
fiber rearranging zones, as for example in the peripheral portions
of each foraminous portion 30 where it abuts the perimeter of
discontinuous imperforate portions 31. Each area of low fiber
density 51 contains a few scattered fiber segments that bridge
across the area.
In addition, nonwoven fabric 50 contains a second pattern of areas
of low fiber density in the form of holes 53, arranged in
accordance with the pattern of arrangement of protuberances 42 of
foraminous portions 30 of backing means 16. Each of these areas 53
is defined by yarn-like bundles 54 of closely associated and
substantially parallel fiber segments, which lie in fiber
accumulating zones located between immediately adjacent dispersal
points, as for example immediately adjacent protuberances 42 in
foraminous portions 30 of backing means 16. In the fabric shown,
each hole 53 is substantially free of any fiber segments.
Each area of low fiber density 51 appears from FIG. 10 to be
approximately 40 times the size of each area of low fiber density
53, or a little bit larger. This is consistent with the relative
size of discontinuous imperforate portions 31 and protuberances 42
of foraminous portions 30 that are included in the apparatus with
which the fabric of FIGS. 9 and 10 was made.
Each pair of immediately adjacent large areas of low fiber density
51 is separated by at least one of the smaller holes, such as those
designated 53' in FIG. 10. To produce this result, the width of
interconnecting foraminous portions 30 of backing means 16 at their
narrowest parts (or, in other words, the closest diagonal spacing
between imperforate portions 31 of the backing means, which is
about 3/16 inch or 0.188 inch) is sufficient to include at all
points around the perimeter of each imperforate portion 30 at least
one protuberance 42 -- and in most parts of the rearranging zone
two protuberances 42 -- with associated fiber accumulating zones or
troughs 44 and 45.
The above detailed description has been given for clearness of
understanding only. No unnecessary limitations should be understood
therefrom, as modifications will be obvious to those skilled in the
art.
* * * * *