U.S. patent number 3,772,739 [Application Number 05/108,547] was granted by the patent office on 1973-11-20 for web forming apparatus.
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Ernest G. Lovgren.
United States Patent |
3,772,739 |
Lovgren |
November 20, 1973 |
WEB FORMING APPARATUS
Abstract
An apparatus for forming an air-laid non-woven web wherein a
pair of parallel lickerins are positioned adjacent one another with
the lickerins being rotated in opposite directions, so that when a
first supply of fibrous material is fed to one lickerin and a
second supply of fibrous material is fed to the other lickerin,
separate supplies of individualized fibers are produced that are
entrained in separate air streams impelled toward one another and
toward a mixing zone between the lickerins. The individualized
fibers are doffed from lickerins by the separate air streams and
centrifugal force, and the doffed fibers are given an initial
trajectory, whereby the inertia of the fibers is sufficient to
allow at least a portion of the fibers from each supply to become
homogeneously blended as the air streams are impelled against one
another. A suction actuated fiber condensing means is positioned in
communication with the mixing zone, and the separate air streams
are combined into a common air stream that directs the fibers
through the mixing zone and toward the condensing means where the
fibers are deposited to produce a web comprised of randomly
oriented fibers. When the material fed to the first lickerin
includes relatively long fibers, such as textile length fibers, and
the material fed to the second lickerin contains relatively short
fibers, such as papermaking fibers, a web of randomly arranged
fibers can be produced having a dispersion of different length
fibers in more or less uniform intermixtures, to create a web
having desired properties.
Inventors: |
Lovgren; Ernest G. (Palos Park,
IL) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
26806009 |
Appl.
No.: |
05/108,547 |
Filed: |
January 21, 1971 |
Current U.S.
Class: |
425/81.1; 19/302;
19/307; 19/145.5; 19/306; 425/82.1 |
Current CPC
Class: |
D21H
5/2628 (20130101); D21H 11/00 (20130101); D21H
13/28 (20130101) |
Current International
Class: |
D01G
25/00 (20060101); D01G 9/00 (20060101); D01G
23/00 (20060101); D04H 1/48 (20060101); D04H
1/72 (20060101); D04H 1/70 (20060101); D04H
5/00 (20060101); D04H 1/16 (20060101); D04H
5/08 (20060101); D04H 1/00 (20060101); D21F
11/14 (20060101); D21F 11/00 (20060101); D01g
025/00 () |
Field of
Search: |
;19/155,156,156.4,205,88,89,105 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Newton; Dorsey
Claims
What is claimed is:
1. Web forming apparatus for forming a nonwoven web of fibers from
at least two sources of fibers, one of said sources being a source
of at least partially pre-opened textile length fibers and the
other of said sources being a source of short fibers, said
apparatus comprising: a pair of lickerins, one having a different
tooth profile than the other; means rotatably mounting said
lickerins in spaced parallel relationship, said one lickerin being
located adjacent the source of textile length fibers and said other
lickerin being located adjacent the source of short fibers, and the
converging facing surfaces of said lickerins downstream of said
fiber sources defining a first portion of a duct means that is
funnel shaped in cross section and which communicates with said
sources of fibers, said duct means having a second portion below
the center lines of said lickerins, communicating with said first
portion for carrying fibers to a fiber deposition zone; means for
rotating said one lickerin in a given direction and at a given
speed; means for rotating said other lickerin in an opposite
direction and at a greater speed than said one lickerin; means for
guiding each source of fibers into contact with its respective
lickerin at a location thereon at which the tangential velocity of
said lickerins has a component toward one another whereby each
lickerin individualizes fibers from its respective source; fiber
collecting means communicating with the second portion of the duct
means and including a movable foraminous member at said depositing
zone to collect said fibers and form a web of nonwoven fibers, and
means for applying a suction to said foraminous member for
providing separate gaseous streams flowing along a path extending
about the periphery of said lickerins for a major portion of the
distance between said contact location and through the first
portion of said duct means to (a) doff at least some of the
individualized fibers from each lickerin, (b) entrain the
individualized fibers in their respective gaseous streams, and (c)
convey said entrained fibers in said separate gaseous streams
through said duct means along flow paths at least initially
directed toward one another, said duct means guiding said gaseous
streams whereby at least a portion of said gaseous streams are
combined to intermix at least a portion of the fibers in one
gaseous stream with at least a portion of the fibers in the other
gaseous stream after which said blended fibers are collected on
said foraminous member.
2. Web forming apparatus as set forth in claim 1 in which each
fiber source guiding means includes a material supporting surface
adjacent each source of fibers, each lickerin-supporting surface
relationship being selected to establish optimum conditions for
substantially completely opening said textile fiber and short fiber
materials.
3. Web forming apparatus as set forth in claim 2 including means
for adjusting the relative location of each lickerin and its
supporting surface.
4. Web forming apparatus as set forth in claim 1 wherein the second
portion of said duct means is defined by a deflector plate mounted
beneath each lickerin, each deflector plate having an upper end
positioned adjacent one lickerin and a lower end positioned
adjacent the fiber collecting means.
5. Web forming apparatus as set forth in claim 1 including means
for adjusting the position of said foraminous member relative to
said lickerins.
6. Web forming apparatus as set forth in claim 5 wherein said means
for adjusting said foraminous member incudes means for varying the
position of said suction applying means relative to said fiber
receiving station.
7. Web forming apparatus as set forth in claim 1 wherein said
lickerins are spaced closely to one another to form a narrow gap
therebetween.
8. Web forming apparatus as set forth in claim 1 wherein said
foraminous member is positioned generally centrally below said
lickerins.
Description
This invention relates generally to air-laid nonwoven materials,
and more particularly to air-laid monwoven webs consisting of a
more or less uniform intermixture of randomly oriented fibers.
Preferably, the web comprises a substantially homogeneous blend of
long and short fibers; i.e., textile length and papermaking
fibers.
Fibers are usually classified according to length, with relatively
long or textile length fibers being longer than about one-fourth
inch and generally between one-half and two and one-half inches in
length. The term "long fibers" as used herein, refers to textile
fibers having a length greater than one-fourth inch, and the fibers
may be of natural or synthetic origin. The term "short fibers," as
used herein, refers to papermaking fibers, such as wood pulp fibers
or cotton linters having a length less than about one-fourth inch.
While it is recognized that short fibers are usually substantially
less costly than long fibers, it is also recognized in many
instances that it is desirable to strengthen a short fiber product
by including a blend of long fibers therein.
In the recent past, nonwoven fabrics have met with increasing
commercial acceptance because such fabrics can be made with
physical properties, and appearance, more or less comparable with
the more expensive woven fabrics. In general, these fabrics are
structures consisting of a random assemblage or web of fibers which
are joined together with a binder to provide the desired
strength.
It is well known to produce nonwoven webs of textile length fibers
by a conventional carding process, and this results in an
anisotropic web wherein the fibers are aligned predominantly in the
machine direction. It is also known to produce a nonwoven web by a
garnetting process, and while webs produced by this technique have
less fiber orientation than carded webs, the garnetted webs are
generally of unsatisfactory uniformity and also are limited to
textile length fibers. Furthermore, the rate at which webs can be
produced by either of these techniques is limited, and these
techniques do not lend themselves for use in making the very low
cost nonwoven fabrics, especially those embodying the use of the
relatively low cost wood pulp fibers.
It is also known to eliminate directionality in carded or garnetted
webs by replacing the doffing cylinder used in these processes with
an air duct leading to an air condenser. In one arrangement, known
as the "Duo-Form" technique, a carding lickerin individualizes
fibers from pre-opened textile length stock, and an intermediate
doffing and transfer cylinder feeds the opened fibers to a second
lickerin for further opening. The fibers removed from the second
lickerin are carried by an air stream and deposited on a screen
cage where the web is formed. The "Duo-Form" process is limited to
the production of a web having textile length fibers, and the
successful operation of the process requires thorough pre-opening
of the fibrous stock.
Another machine that has been proposed for eliminating
directionality in carded or garnetted webs consists of two
traveling flat cards having doffers which confront one another.
Rapidly rotating needle cylinders remove the fibers from the card
doffers and transport them in an essentially inverted J-shaped path
through the converging upper branches of a generally Y-shaped duct
system. The lower branch of the duct system is traversed by a
horizontally moving screen upon which the fibers are condensed.
This latter apparatus is, of course, limited to textile length
materials, and even though the output of two cards is combined, the
total production rate is still unsatisfactory.
The velocities of the air streams flowing through the converging
branches of the generally Y-shaped duct system of the machine just
referred to is, of necessity, quite limited. These low velocities
are required to avoid upsetting the web on the doffing cylinders of
the cards prior to removal of the fibers by the rotating needle
cylinders. Also, while this machine ultimately combines the output
of two cards into a single duct, because of the necessity of having
low air velocities and thus eliminating the possibility of
turbulent flow conditions, in the event that two different textile
length fibers were fed into the converging branches of the duct
system of the machine, little or no blending of the different
fibers would take place, and instead a web of an essentially
laminar arrangement of fibers would result with a marked interface
between the layers of fibers.
Nonwoven webs have also been produced by feeding filamentary
material downwardly between oppositely rotating beater blades which
break up or rupture the filaments to form long fibers as the
filaments are fed between the beater blades. The thus formed fibers
are subsequently deposited on a screen or other condenser to form a
web, and while such webs may have the textile length fibers
randomly arranged, the process is limited to use with tow or other
continuous filament material as the source of the fibers.
A further process for producing a random web of textile length
fibers is known as the "Rando-Webber" process, and is practiced
upon apparatus available from the Curlator Corporation of East
Rochester, New York. In this process, pre-opened textile length
fibrous material is fed to a supply device, which further opens and
delivers the fibrous material as a loose mat to a web forming unit.
The mat is compressed and fed over a nose bar where it is brought
into contact with a lickerin, and the teeth of the lickerin remove
fibers from the mat and introduce them into a high velocity, low
pressure air stream in the reduced cross section throat of a duct.
The fibers are subsequently deposited in random fashion on a
condensing screen to produce a substantially isotropic web. While
this process and apparatus have functioned generally staisfactorily
to produce a relatively uniform random web of textile length
fibers, it is generally not suitable for use with short fibers nor
with blends of short and long fibers. Furthermore, throughputs with
this type of apparatus are limited.
It has recently been proposed to produce a random fiber web
consisting entirely of short fibers, and one such process is known
as the "Texpa" process that is practiced upon apparatus also
available from the Curlator Corporation of East Rochester, New
York. This apparatus consists essentially of two adjacent,
generally vertically disposed foraminous belts that converge
downwardly and that are positioned in communication with a duct
carrying short fibers. A pair of oppositely rotating opening
cylinders are positioned in close adjacency to one another beneath
the converging belts, and a suction actuated fiber condensing means
is positioned below the opening cylinders. Suction is applied to
the foraminous belts to withdraw fibers from the conveying duct
thereabove, and the belts convey the fibers downwardly where they
are compressed into a single mat at the point of convergence of the
two belts. The single mat is fed downwardly to the opening
cylinders, one of which is rotating at a faster speed than the
other. The cylinders have oppositely disposed teeth, so that as the
mat is fed downwardly between the cylinders, the downwardly facing
teeth of one cylinder carry the fiber through the nip between the
cylinders, while the upward facing teeth of the other cylinder hold
the fibers back. This action tears the mat into individual fibers
which are then carried by an air stream onto a condenser belt to
form a random web. The "Texpa" process is generally not suitable
for use with long fibers, or blends of long and short fibers, and
the throughputs obtained with this process are limited.
The desirability of, and need for, a web comprised of a mixture of
long and short fibers is well understood by those skilled in the
art. In general, the desired characteristics of the nonwoven end
product as well as its utility dictate the type of fibers and the
relative proportions of long and short fibers to be used. Thus, for
example, the product may require one or more characteristics such
as tear resistance, abrasion resistance, washability and
stretchability, burst strength, absorption or nonabsorption to
different liquids, heat sealability, ability to resist
delamination, etc., all of which will influence the type of fiber
or mixture of fibers to be used. Thus, by way of specific example,
absorbent products requiring strength characteristics may be a
combination of two or more different fibers such as wood pulp
fibers and rayon or similar fibers in varying percentages.
Likewise, again depending on the nature of the product desired, the
product may have to possess substantially random characteristics as
opposed to oriented fiber characteristics in order to provide for
balanced properties in both the machine and cross direction for
most uses. For example, in the case of products intended for
surgical or similar uses requiring absorbency characteristics, such
as a sanitary napkin or a portion thereof, absorbent surgical
drapes, etc., mixtures of randomly oriented short and long fibers
are required to provide improved mechanical characteristics; while
in the case of nonwoven materials suitable for use as disposable
items in the field of diapers, short fibers are generally
employed.
Typical of the short fibers are wood pulp fibers from various types
of woods, cotton linters, asbestos fibers, glass fibers and the
like; with wood pulp fibers being those which find most frequent
use in a large variety of products due to their ready availability
and economical attributes. Typical of the long or staple length
fibers are synthetic fibers such as cellulose acetate fibers, vinyl
chloride-vinyl acetate fibers (e.g. the product marketed under the
trademark "VINYON"), polyamide fibers such as NYLON 6, NYLON 66,
etc., viscose staple rayon, cupra-ammonium rayon or other
regenerated cellulose fibers including saponified ester fibers,
cellulose ester fibers such as cellulose acetate and cellulose
triacetate, acrylic fibers, polyester fibers, polyvinyl chloride
fibers, polyolefin fibers such as polyethylene and polypropylene,
fluorocarbon fibers such as "TEFLON" and natural fibers such as
cotton, flax, jute, wool, silk, ramie or "rag," or protein fibers
such as "VICARA" Combinations of any of the short and staple or
long fibers may be employed in this invention. The denier of the
fibers used may vary over a wide range and may be from one-half to
100 depending on the type of fiber employed and the requirements of
the nonwoven material. Commonly, when using staple fibers such as
rayon, the denier will vary from 0.75 to 5 or 6 denier.
Conventionally, the shorter type of fibers such as wood pulp fibers
are commerically available for air-laying processes in the form of
pulp boards, which are compressed sheets of fibers in intimate
contact with each other. The pulp boards come in varying
thicknesses and lengths, typical thicknesses being from
one-sixteenth of an inch to three-sixteenths of an inch, and
sometimes more. If desired, the starting material such as pulp
boards may be comprised of a mixture of two or more different
fibers, preferably of approximately the same length. Thus, by way
of example, in place of utilizing a conventional wood pulp board, a
board may be of a mixture of wood pulp fibers and cotton linters,
asbestos fibers, glass fibers, etc. Thus, different properties may
be imparted to the product by employing various combinations of
fibers.
In the case of staple or longer length fibers, such as rayon, for
example, they are normally commerically available in bale form in
various fiber lengths; and for use in the present invention, they
are generally employed in a pre-opened oriented condition, termed a
"carded web" or "carded batt" in the art. To this end, baled rayon
can be formed into a carded lap according to conventional
techniques known to those skilled in the art, which, briefly
summarized, first involves formation of a picker lap wherein the
fibers are formed into a uniform batt of generally constant weight,
whereafter they are carded to orient and open and comb the fibers,
and thus form the "carded batt." If desired, in place of using a
carded batt of only rayon, a mixture of rayon and other fiber or
fibers, or for that matter a mixture of any two or more different
long fibers can be employed, thereby providing a product having
different fibers and with them the different properties they impart
to the ultimate nonwoven fabric. It is not necessary that the
staple length fibers be used in the form of a carded batt but these
fibers may be presented to the machine of the present invention by
other means well known to those skilled in the art, such as chute
feeding, CMC even feed, or directly from a card, for example.
Those skilled in the art have recognized the long felt need for
providing a process and apparatus for producing a web of
homogeneously blended short and long fibers, as described above,
with substantially all of the fibers being randomly disposed.
Various systems have been proposed in the past, but none have met
with wide commercial success because of the failure to either get
satisfactory randomnization, satisfactoy homogenization, or a
satisfactory production rate.
For example, it has been proposed to individualize short fibers by
a milling device, such as a hammer mill or a fitz mill, and to
entrain the individualized short fibers in an air stream into which
individualized long fibers are fed. In one known technique, the
individualized short fibers are transported in a horizontal duct,
with a lickerin rotating at a narrowed throat portion of the duct
and combing individual fibers from a long fiber web or mat and
introducing them into the short fiber air stream traveling
therebelow. It has been proposed to form a web by depositing the
airborne fibers on a foraminous condenser that intersects the duct,
or by allowing the duct to feed fibers into a gravity settling box,
where they settle by gravity on a foraminous conveyor. In either
technique, because the long fibers are introduced into the air
stream above the short fibers, the resulting webs have a tendency
toward stratification, with the long fibers predominating at the
top of the web, and the short fibers predominating at the bottom of
the web. This lack of complete homoginization has made such
processes generally unsatisfactory.
Webs of blended short and long fibers that have been produced by
such prior art techniques have not only exhibited a marked
different in properties from one side to the other, but also have
shown a definite tendency to strip or separate at the line of
demarcation between the layers. While such webs have been
satisfactory for certain products, particularly where the web is an
internal layer that is not visible to the consumer, such webs have
not been completely satisfactory for other products, particularly
where strength is required and, also, where the web is exposed to
view by the consumer.
One of the major problems in connection with blended fibrous webs
formed by prior art techniques is in the proper opening of the
fibrous materials at high speeds to substantially completely
individualize the fibers without damaging them. For example, a
single lickerin has been used to simultaneously open both long and
short fiber materials, and it has been found that lickerin speeds
that are suitable to open the short fiber material in a high speed
commercial operation have caused excessive damage to the fibers of
the long fiber material.
In webs produced by prior art techniques, it is common to find a
relatively large percentage of incompletely opened clumps of fibers
and it is also common to find a relatively large percentage of
"salt" - like hardened particles that are formed by compressing
individual fibers during the fiberizing step. Such webs have not
been visually acceptable and suitable for use as an exposed layer
in an end product, since they are not uniform in appearance.
Furthermore, in webs having clumps of fibers, or hardened particles
of broken and/or compacted fibers, the functional characteristics
of the web are not uniform. For example, the presence of clumps of
fibers or compacted fibers causes the web to be of variable weight,
strength, cohesiveness, fluid absorbtiveness and uneven in color
when dye is used. Webs having a high percentage of salt-like
particles, are completely unsatisfactory for many uses, such as
surgical towels and dressings, because of the tendency of these
particles to flake off the web.
To obviate such problems, it has been necessary to rotate the
lickerin at a compromise speed, which is not suitable for
commercial production. Other techniques that have been proposed in
the past have the same or similar problems.
In accordance with the process and apparatus of the present
invention, a nonwoven web of substantially completely open fibers,
preferably randomly oriented, is produced wherein at least a
portion of the web consists of a homogeneous blend of fibers from
two separate and distinct supplies of fibers. The present invention
utilizes a pair of parallel lickerins that are rotated in opposite
directions to individualize fibers from each supply. When the web
is to include a blend of long and short fibers, the lickerin for
the short fibers is rotated at a faster speed than the lickerin for
the long fibers. A backing member is provided for each fibrous
source adjacent its respective lickerin, and different and optimum
opening relationships may be established between each lickerin and
the nose bar portion of its associated backing member.
The fibers are doffed from the lickerins substantially immediately
after individualization by separate gaseous streams flowing
adjacent each lickerin, and by centrifugal force, which tends to
throw the fibers into their respective gaseous streams. The
supplies of indivualized fibers are entrained in the separate
gaseous streams, and the streams are impelled toward one another
and toward a generally centrally disposed mixing zone, where the
fibers intermix.
The supplies of individualized fibers are combined in a common
gaseous stream flowing downwardly through the mixing zone, in an
exemplary form of the invention. The common air stream may be
produced by the cooperative action of a suction actuated fiber
condensing means at the terminal end of the mixing zone and by the
air generated by the rotary action of the oppositely rotating
lickerins.
In the process of the present invention, the fibers entrained in
the separate gaseous streams have a trajectory including a
component directed toward one another, as well as a component
directed toward the mixing zone. Although the fibers are
transported by the separate gaseous streams through the mixing
zone, the fibers have sufficient kinetic energy by virtue of their
mass and velocity that the fibers continue to travel generally in
the direction of their initial trajectory because of their inertia.
The component of motion of the fibers toward one another causes
them to combine in an intimate mixture of fibers as the gaseous
streams are impelled against one another and combined into the
common stream. The combined stream transport the mixed and blended
fibers through the mixing zone to a condensing means where the
fibers are deposited to build up a web of the desired
thickness.
The blending action may be regulated by controlling certain machine
parameters, such as the rate of fiber input, the volume and/or
velocity of the air flowing through the machine, the speeds of the
lickerins, type of lickerin teeth and the winding of the clothing,
and the geometry of the ducting system. For example, at relatively
low air volumes, when producing a web comprised of homogeneously
blended short and long fibers, since the short fiber lickerin is
rotating at a higher speed than the long fiber lickerin, a
differential velocity is created in the common gaseous stream, with
the portion of the gaseous stream on the short fiber side of the
machine having a greater velocity (and hence a lower pressure) than
the portion of the gaseous stream on the long fiber side of the
machine. Therefore, the individualized long fibers are accelerated
and drawn into the faster moving zone of air, and the acceleration
of the individualized long fibers keeps them under tension
substantially until they are deposited on the fiber condensing
means. The suction or drawing action created by the faster rotating
short fiber lickerin enhances the intimate admixure of the long
fibers with the individualized short fibers.
Also, by having relatively higher gas volumes, with an
appropriately shaped ducting system, the gas passing through the
machine can be retained in a turbulent condition, which also
enhances the degree of blending of the long and short fibers.
In one embodiment of the invention a variable nose bar-lickerin
relationship is provided for each supply of fibrous material, so
that these realtionships can be individually adjusted and
controlled for different materials to produce a lickerin action
that will substantially completely open the respective fibrous
materials.
The relationship of the fiber condensing means to the fiber mixing
zone is also adjustable in an illustrative embodiment of the
invention, so that by establishing a desired relationship between
the mixing zone and condensing means, the directioning of the
individual fibers of the resulting web can be varied and controlled
between a completely randomized orientation, and an orientation
wherein a majority of the fibers extend either lengthwise or
crosswise of the web.
The process and apparatus of the present invention produces a web
having at least a portion comprised of a homogeneous admixture of
long and short fibers; and in webs where all of the fibers are
homogeneously blended, such webs are not only uniform in external
appearance, but also have uniform functional characteristics
including weight, thickness, etc.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view, partly in section, of a web
forming apparatus constructed in accordance with the present
invention;
FIG. 2 is a side elevational view, partly in section and partly
broken away, of the apparatus illustrated in FIG. 1;
FIG. 3 is an enlarged sectional view taken generally along line
3--3 of FIG. 2;
FIGS. 4--12 are enlarged, fragmentary sectional views of modified
configurations for the mixing zone of the apparatus illustrated in
FIGS. 1--3;
FIG. 13 is a central sectional view through a further embodiment of
the web forming apparatus, and FIG. 13 is taken generally along
line 13--13 of FIG. 14;
FIG. 14 is a front elevational view of the apparatus illustrated in
FIG. 13;
FIG. 15 is a fragmentary perspective view illustrating details of
the condensing screen of the embodiment of FIGS. 13 and 14;
FIG. 16 is an enlarged sectional view taken generally along line
16--16 of FIG. 15;
FIGS. 17-19 are schematic representations of the apparatus
illustrated in FIGS. 13-16, and illustrate the baffle in different
positions;
FIGS. 20-23 illustrate in cross section various webs that can be
produced by the apparatus of FIGS. 13-16 and
FIG. 24 is an enlarged schematic view illustrating the profile of
the lickerin teeth used in the apparatus of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
While this invention is susceptible of embodiment in many different
forms, there is shown in the drawings and will herein be described
in detail only preferred embodiments of the invention and
modifications thereof, with the understanding that the present
invention is to be considered as an exemplification of the
principles of the invention and is not intended to limit the
invention to the embodiments illustrated. The scope of the
invention will be pointed out in the appended claims.
Referring now to the drawings in detail, and particularly to FIGS.
1-3, an exemplary embodiment of the apparatus of the present
invention is indicated generally at 20, and the apparatus 20
includes frame means 22 supporting first and second fiberizing
means 24 and 26 adjacent the upper end thereof, and supporting a
suction actuated fiber receiving means 28 therebelow, as will
hereinafter be described in detail. Fiberizing means 24 and 26 are
operative on separate sources of fibrous material to substantially
completely open the material and create separate supplies of
individualized fibers that are entrained and conveyed in separate
gaseous streams directed toward each other and toward a common
mixing zone 25 therebetween. The individual fibers are doffed from
the fiberizing means 24 and 26 by centrifugal force and by the
separate gaseous streams moving relative to the fiberizing means.
The separate gaseous streams are impelled against one another, and
are combined into a common high speed gaseous stream flowing
through the mixing zone 25 toward the fiber receiving means 28. The
fibers are given an initial trajectory in the doffing direction,
and the kinetic energy imparted to the fibers by virtue of their
mass and velocity enables them to have substantial inertia and
continue to have a significant component of motion toward the other
supply of fibers. This allows at least a portion of the fibers of
each supply to become homogeneously blended and further mixing can
take place in the mixing zone 25 by adjusting certain machine
conditions, as is hereafter explained. The entrained fibers are
then directed to, and deposited upon, receiving means 28 by the
common air stream to build up a web W. A doffing roll 27 is
supported upon frame means 22 adjacent receiving means 28 for
removing web W therefrom and transferring it to a conveyor 29
therebelow.
The apparatus of the present invention includes frame means 22
defined in part by upright members 30 that are connected to one
another by upper crossrails 32 and lower crossrails 34. A subframe
36 is mounted upon upper crossrails 32, and subframe 36 includes a
pair of spaced side plates 38 that are stabilized by transversely
extending tie rods 40. Fiberizing means 24 and 26 are supported
between side plates 38 at first and second fiberizing stations,
respectively.
In order to be able to change the characteristics of web W, as by
varying the direction and pattern in which the individualized
fibers are deposited on the fiber receiving means 28, in the
embodiment illustrated in FIGS. 1-3, the position of the fiber
receiving means 28 relative to the mixing zone 25 can be varied,
and for this purpose, a pair of transversely extending frame
members 42 are adjustably connected to uprights 30. A vertical
adjustment means is provided by plates 44 that are fixed to
opposite ends of each frame member 42, with the plates 44 each
including spaced, vertical slots 46. Locking bolts 48 impale slots
46 and are threaded into internally threaded openings in uprights
30, so that the frame members 42 can be moved vertically when the
locking bolts 48 are loosened, and positively retained in the
desired position relative to mixing zone 25 when locking bolts 48
are tightened.
Fiber receiving means 28 includes side plates 50 at opposite ends
thereof, and horizontally or lateral adjustment of the fiber
receiving means 28 is effected by mounting bolts 52 that are
slidably mounted in elongate slots 54 in the upper flange 56 of
frame member 42. As can be seen in FIG. 1, bolts 52 extend through
openings in mounting feet 58 that extend laterally from the lower
ends of side plates 50, and nuts 60 are threaded upon bolts 52 to
retain the fiber receiving means 28 in the desired position of
lateral adjustment relative to mixing zone 25. While the position
of the fiber receiving means 28 is variable in the illustrated
embodiment of the invention, it should be understood, that the
adjustability feature is not critical to the present invention,
when, in use, a given type of web is to be continuously produced on
the machine.
A mass of long or textile length fibers 62 of the type described
above, is fed to fiberizing means 24 by a cylindrical feed roll 64.
The opposite ends of feed roll 64 are rotatably supported upon
mounting plates 38, and the feed roll 64 is positively rotated by
conventional means, not shown, to control the rate and amount of
long fiber material that is fed to the fiberizing means 24.
The present invention includes adjustment means 66 for varying the
position of the feed roll 64 relative to a nose bar assembly 68 for
accommodating different thicknesses of long fiber material. The
adjustment means 66 includes a mounting block 70 adjacent each side
plate 38, and each block 70 is generally T-shaped in cross section
with an offset portion being slidably mounted in an inclined slot
72 in the adjacent mounting plate 38. Each block 70 includes a
recess 74 that positions a further mounting block 76 for movement
perpendicularly to slots 72. Mounting blocks 76 include a boss 78
having the ends of the feed roll 64 rotatably mounted therein, and
elongate slots 80 at each side of blocks 76 are impaled by clamping
bolts 82 that are threaded into blocks 70 to allow the blocks 76 to
be adjusted at right angles to slots 72. In this manner, the
clearance between the feed roll 64 and nose bar assembly 68 can be
set at an optimum gap for the particular type and thickness of the
fibrous source 62.
Feed roll 64 is retained in a positive material feeding
relationship with the nose bar assembly 68, and to this end, feed
roll 64 is urged toward the nose bar assembly 68 by springs 84 that
act between a recess in one end of each block 70 and an aligned
recess in an abutment plate 86 that is secured to each side plate
38. Elongate guide slots 88 are provided in each corner of blocks
70, and clamping bolts 90 impale slots 88 and are threaded into
openings in side plates 38. The ends of slots 88 limit the movement
of feed roll 64 toward the nose bar assembly 68 and provide a
minimum clearance therebetween, it being understood that the bolts
90 can be tightened to positively secure the feed roll 64 in a
selected position of adjustment. By virtue of the above-described
adjustment means 66, it will be appreciated that feed roll 64 can
be located in any of a plurality of locations relative to the nose
bar assembly 68. However, in a situation where the fibrous source
62 will always be substantially the same, it should be understood
that the adjustment means 66 can be eliminated or greatly
simplified.
In order to provide a first supply of individualized fibers, a
material opening cylinder 92 is mounted for rotation in a clockwise
direction between side plates 38 below feed roll 64, and opening
cylinder 92 preferably takes the form of a lickerin having spirally
wound toothed clothing 94 thereon. The teeth of the rayon lickerin
usually have a lower tooth height and pitch than the pulp lickerin.
The pitch and height of the teeth used on the lickerin for the
rayon may vary, ggod results being obtained with a tooth pitch of
about one-eighth inch to about one-fourth inch and a tooth height
of about one-eighth inch to about one-fourth inch. The angle of the
teeth of the lickerin for the rayon may also vary, generally within
the limits of about -10.degree. to about +20.degree.. The teeth 96
may have only a slight positive rake, or even a slight negative
rake, to facilitate doffing of the short fibers from the lickerin
92.
Adjustment means 98 is provided for varying the position of the
nose bar assembly 68 relative to the lickerin 92, so as to provide
optimum conditions for substantially fully opening the long fiber
material 62 without damaging the fibers thereof. The nose bar
assembly 68 includes a holder 100 that extends between side plates
38, and holder 100 supports a nose bar 102 thereon that has a
curved material supporting surface facing feed roll 64. Holder 100
is mounted for movement toward and away from lickerin 92 in
inclined slots 104 in side plates 38, and the position of holder
100 is adjusted by screws 106 that are threaded into holder 100,
with screws 106 reacting against saddle members 108 that are
secured to side plates 38. A support block 110 is secured to each
side plate 38, and clamping plates 112 fixed to holder 100 are
tightened against support blocks 110 by screws 114 to positively
retain holder 100 in the selected positions of adjustment, it being
understood that clearance slots 116 are provided in blocks 110 to
allow the holder 100 to move relative thereto. Should it be desired
to always include substantially the same type of long fibers in the
end product, the aforementioned adjustment means 98 may become
unnecessary.
The long fiber material 62 is presented to the teeth of the rapidly
rotating lickerin 92 at approximately 11 o'clock position, and the
lickerin teeth comb out and individualize the long fibers as the
teeth move past the nose bar 102.
In order to be abe to vary and control the mixing characteristics
of the long and short fibers as their individual carrier streams
are combined, as will hereinafter appear, the width of the throat
of the mixing zone 25, i.e., the distance between the fiberizing
means 24 and 26, can be varied, and adjustment means 118 is
provided for moving lickerin 92 in and out in a horizontal plane.
The axle 122 of lickerin 92 is mounted in slide members 124 that
ride in horizontal slots 120 in side plates 38, and adjustment
means 118 is provided by adjusting screws 126 that are threaded
into slide members 124 for varying the position of lickerin 92.
Adjusting screws 126 react against plates 128 that are secured to
side plates 38.
Lickerin 92 is rotated in a clockwise direction, as shown by the
directional arrow in FIG. 3, and to this end, the output shaft 132
(FIG. 1) of a motor 130 is connected to lickerin 92 by a belt drive
system including a sheave 134 on shaft 132, a sheave 136 on axle
122, and an endless belt 138 trained over sheaves 134 and 136.
Motor 132 can be bolted to an upright 30 of a main frame, as
illustrated, or it can be mounted on the floor, and the motor
mounting means may be adjustable, so that the position of the motor
130 can be changed when the position of the lickerin 92 is changed.
Motor 130 rotates lickerin 92 at a high speed that allows the teeth
96 to comb out and individualize the long fibers from supply 62 at
a rapid rate, and for purposes of illustration, a rotational speed
of 2,400 rpm has been found to be satisfactory to produce a desired
quantity of individualized rayon fibers from picker lap fiber
source without damage to the fibers. Lickerin 92 can be rotated at
higher speeds for greater throughput, if desired.
The rotation of lickerin 92 generates a stream of gas, e.g., air,
as indicated by the directional arrow 139 in FIG. 3, that flows
under the nose bar assembly 68, to initiate a fiber doffing action,
in cooperation with the centrifugal forces acting on the fibers,
substantially immediately after the fibers are combed from source
62. Since doffing is initiated substantially immediately following
fiber individualization, i.e. at about the 12 O'clock position, a
large number of the fibers are given an initial trajectory having a
significant component of motion toward the oncoming fibers from
fiberizing means 26. As the fibers are accelerated and entrained in
the stream 139 they possess substantial kinetic energy because of
their mass and velocity, and the inertia of the fibers tends to
keep them moving along a path generally in the direction of their
initial trajectory.
A further gas stresm, represented by the directional arrow 140 in
FIG. 3, flows generally vertically downwardly through the mixing
zone 25 toward the fiber collecting means 28 adjacent the periphery
of lickerin 92, and any undoffed fibers are removed from the
lickerins by the stream 140. Stream 140 serves as a common carrier
stream for the fibers doffed from both lickerins as will
hereinafter appear. The gas stream 140 can be generated in part
from a separate source 142, such as a commercially available air
knife, or the gas stream can be generated by the combined action of
the separate carrier streams and the suction actuated condenser
means 28, as will hereinafter be explained. In any event, the
common stream 140 receives the oncoming fibers and partially, but
not completely (as will hereafter appear), overcomes their inertia
to change their trajectory and direct them to the condensing means
28.
In the event that an air knife is used, adjustment means 144 (FIG.
1) may be provided for positioning the air knife in an optimum
position relative to the mixing zone 25 to get the desired type of
directionalized air flow. Adjustment means 144 is arranged to move
the air knife 142 both vertically and angularly, if desired. To
this end, the air knife 42 includes laterally extending support
portions 146 at each end thereof having internally threaded
vertically extending openings therein. Frame members 148 are
secured to side plates 38, and adjusting screws 150 adjacent each
side plate 38 extend through the threaded openings in support
portions 146 and through aligned bores in frame members 148 so that
the air knife 142 can be vertically adjusted. A worm wheel 152 is
provided at each end of air knife 142, and angular adjustment of
the air knife is accomplished by worm gears 154 on adjusting screws
156 that are mounted for horizontal movement in horizontal bores in
frame members 148. By appropriate adjustment of adjusting screws
150 and 156 the direction of the air stream emanating from the
orifice at the lower end of the air knife can be varied and
controlled.
A mass of short fibers 162, such as pulpboard or linters board in
sheet form, is fed to fiberizing means 26 by a cylindrical feed
roll 164, which is positively rotated by conventional means, not
shown, to control the rate and amount of short fiber material that
is fed to the fiberizing means 26. The opposite ends of feed roll
164 are rotatably mounted in support arms 166 that are pivotally
connected between side plates 38 by pivot members 167. Feed roll
164 is biased towards a nose bar assembly 168 by springs 169 that
bear against support arms 166, and springs 169 urge the support
arms in a counterclockwise direction about pivots 167. Springs 169
react between support arms 166 and a nut 170 on spring retention
members 172 that are pivotally connected to side plates 138, it
being understood that the members 172 pass through clearance
openings in the support arms 166. Spring holding members 172
include a stop surface 174 for limiting the pivotal movement of the
support arms 166, thereby establishing a minimum clearance between
the mass 162 of short fibers and the nose bar assembly 168.
A material opening cylinder 176 is mounted for rotation in a
counterclockwise direction between side plates 38 below feed roll
164, and opening cylinder 176 preferably takes the form of a
lickerin having spirally wound toothed clothing 178 thereon. As is
evident from FIGS. 1 and 3, lickerins 92 and 176 are positioned in
parallelism with one another and are preferably of the same
diameter. In an exemplary embodiment of the invention, lickerins 92
and 176 have an outer diameter of approximately 9 1/2 and a length
of approximately 40 inches. The individual teeth 180 of clothing
178 are selected to optimize the opening or grinding conditions for
the short fiber material 162. The pitch and height of the teeth
used on the lickerin for the pulpboard may vary, good results being
obtained with a tooth pitch or about three thirty-second inch to
about one-half inch and a tooth height of about three thirty-second
inch to about one-half inch. The rake angle of the individual teeth
180 of clothing 176 is selected to give the optimum opening
characteristics for the specific material being fed to the
lickerin. The angle of the teeth of the lickerin for the pulpboard
may also vary, generally within the limits of about -10.degree. to
about +10.degree.. To facilitate doffing the teeth may preferably
have a negative rake.
Optimum conditions for substantially completely opening the short
fiber material 162 may be further established by virtue of an
adjustment means 182 which varies the position of the nose bar
assembly 168 relative to the lickerin 176. The nose bar assembly
168 includes a holder 184 having a nose bar 186 at the lower end
thereof that faces feed roll 164. The nose bar 186 preferably has a
straight or flat material engaging surface for supporting the short
fiber pulp material 162 in position to have the material combed and
the fibers individualized by lickerin 176. Plates 188 (FIG. 1) are
secured to opposite ends of the holder 184, and plates 188 are
generally T-shaped in cross section, with the offset portion of
each plate 188 riding in an inclined slot 190 in one side plate 38.
The adjustment means 182 is provided by adjusting screws 192 that
are threaded into openings in plates 188, with the screws 192
reacting against saddle members 194 that are fixed to the side
plates 38. Plates 188 include a plurlaity of elongate slots 196
(FIG. 1) therein, and clamping bolts 198 that are threaded into
side plates 38 impale slots 196, it being understood that the bolts
198 are tightened to positively retain the holder 184 in the
selected position of adjustment relative to lickerin 176.
The nose bar holder 184 can also be adjusted angularly relative to
the feed roll 164 and the teeth on lickerin 176, and to this end, a
block 200 on one side of the holder 184 is pivotally mounted on a
shaft 202 that the extends transversely between plates 188. Further
clamping plates 204 are affixed to the ends of shaft 202, and
arcuate slots 206 in clamping plates 204 are impaled by clamping
bolts 198, that are tightened to positively retain the holder 184
in the selected position of angular adjustment. If should be
understood that the adjustment means for either or both of the nose
bar assemblies is not critical to the process of the present
invention, and fixed lickerin-nose bar relationships may be
established for both supplies of fibers, particularly if each
lickerin and nose bar is to always open material having
substantially the same characteristics, but the adjustability
feature adds flexibility to the machine making capable of use with
materials having different characteristics.
As is mentioned briefly above in connection with lickerin 92 a
preselected spacing between the lickerins 92 and 176 can be
established by virtue of an adjustment means 210 for varying the
position of lickerin 176 relative to the mixing zone 25 and
lickerin 92 acting in combination with the adjustment means 118 for
lickerin 92. To this end, the axle 212 of lickerin 176 is mounted
in slide members 214 that ride in horizontal slots 216 in side
plates 38. Lickerin 176 is moved in and out by adjusting screws 218
that are threaded into slide members 214, with screws 218 reacting
against plates 220 that are secured to the side plates 38. By
virtue of the adjustment means 118 and 210, the width of the throat
portion of the mixing zone 25 between the lickerins 92 and 176 can
be varied and controlled. The distance between the lickerins will,
to a certain extent, be determinative of the volume of fibers that
are entrained in gas stream 140 and ultimately deposited upon
receiving means 28. A spacing of approximately .25 inches has been
found to give excellent results although smaller gaps, and larger
gaps up to 1.5 inches have also given satisfactory results.
Lickerin 176 is rotated in a counterclockwise direction, as shown
by the directional arrow in FIG. 3, and to this end, the output
shaft 222 (FIG. 1) of a motor 224 is connected to lickerin 176 by a
belt drive system including a sheave 226 on shaft 222, a sheave 228
on axle 212, and an endless belt 230 trained over sheaves 226 and
228. Lickerin 176 may be rotated at a speed substantially faster
than the rotational speed of lickerin 92 when lickerin 176 is
opening short fiber material and lickerin 92 is opening long fiber
material. For purposes of example, a rotational speed of 4,000 rpm
has been found satisfactory to produce a desired quantity of high
quality individualized pulp fibers from a pulpboard. Faster
rotational speeds for lickerin 175 can be used if greater
throughput is desired. Like motor 130, motor 224 is illustrated as
being secured to an upright 30 of the main frame, although it may
be mounted on the floor, and the mounting for motor 224 may also be
adjustable.
In order to improve the opening action of lickerins, an arcuate
cover plate 233 (shown only for lickerin 92) may be positioned over
the portion of the lickerin between the nose bar and the upper end
of the mixing zone. The end of cover plate 233 is spaced from the
nose bar 102, so that the rotation of the lickerin 92 will draw in
a stream of gas, e.g. air, between the cover plate 233 and nose bar
102 that will force the fibers against the lickerin 92, while at
the same time force the fibers cooling the cover plate and helping
to convey fibers. A gap of one-half inch between the cover plate
233 and nose bar 102 has proven to be effective in providing a
stream that forces the upper layer of fibers into the teeth of
lickerin 92 for additional working.
Because of the relatively high rotational speeds of lickerins 92
and 176, each lickerin creates a zone of gas, e.g. air, moving
circumferentially therearound. As is mentioned above, lickerin 92
generates gas stream 139 that initiates doffing of the
individualized fibers from lickerin 92. Likewise, lickerin 176
generates a gas stream, represented by directional arrow 231, that
passes under nose bar assembly 168 and in conjunction with
centrifugal force and tooth configuration initiates a fiber doffing
action substantially immediately after the fibers have been combed
from source 162. As is evident from FIG. 3, the short fiber
material is presented to the teeth on lickerin 175 at approximately
a 1 o'clock position. Since a large number of the fibers are doffed
from lickerin 176 substantially immediately following
individualization, i.e. at about a 12 o'clock position, the fibers
are given an initial trajectory having a significant component of
motion toward the oncoming fibers from lickerin 92. As the fibers
are accelerated into stream 231, because of their inertia, they
will tend to continue to move in their initial direction.
Since the lickerins 92 and 176 are rotating in opposite directions,
the zones of air generated thereby cooperate to produce at least a
portion of the common high speed stream 140 that is directed
downwardly between the lickerins through the mixing zone 25 toward
the fiber receiving means 28. It is has been found that with
rotational speeds of the aforementioned magnitude, i.e., 2,400 rpm
for lickerin 92 and 4,000 rpm for lickerin 176, and with the
tooth-to-tooth spacing of the lickerins being in the aforementioned
range, the lickerins can produce a substantial portion of the
velocity of stream 140, depending of course on the presence or
absence of air knife 142 and the magnitude of the suction drawn by
fiber receiving means 28.
It has been found that at the lickerin rotational speeds mentioned
above and with condensing means 28 pulling approximately 400 cfm,
the combined air stream 140 has an average volumetric flow rate of
approximately 500 cfm. This flow rate gives the individual streams
139 and 231 and the common stream 140 sufficient velocity to effect
the desired fiber doffing and blending, so that a separate gas
source, such as air knife 142 is not necessary.
As has been mentioned above, the fibers entrained in gaseous
streams 139 and 231 posess substantial kinetic energy, and their
inertia tends to keep them moving in the initial doffing direction.
As the separate gaseous streams 139 and 231 merge into the common
gaseous stream 140, the combined forces of gravity and the suction
applied by the fiber receiving means tend to cause the fibers to
assume a more downward trajectory, but the momentum of the fibers
is such that as the streams 139 and 231 are impelled against one
another, a substantial portion of the long and short fibers become
intermixed. The position at which the streams 139 and 231 are
brought together, and the degree of blending of the long and short
fibres can be controlled by varying certain machine parameters such
as the volume and/or velocity of gas flowing through the machine,
the speed of the lickerins, the rate of fiber input, the geometry
of the ducting system, and the position of the fiber receiving
means.
In one mode of operation, at relatively low gas volumes, in forming
a web of blended long and short fibers, since lickerin 176 is
rotating at a substantially greater speed than lickerin 92, a zone
of lower pressure is created in the common high speed stream 140 in
mixing zone 25 between and below the lickerins 92 and 176. The
individualized long fibers from the lickerin 92 are accelerated
toward the zone of low pressure and retained substantially under
tension until the fibers are deposited upon the fiber receiving
means 28. The drawing of the long fibers into the zone of low
pressure and the aforementioned inertial impelling of the fibers
together, cause the long and short fibres to be homogeneously
blended in the mixing zone 25.
Also, as is explained in detail in the commonly assigned,
concurrently filed application Ser. No. 108,545 of A. Farrington,
the geometry of the ducting of the machine, may be configured to
insure that the gaseous streams will have turbulent flow
characteristics from the point of doffing to the point of deposit
of the fibers. This, together with the interposition of a baffle
between the separate gaseous streams can result in the production
of various different webs, including a web comprised of
homogeneously blended long and short fibers. Furthermore, as is
explained in the commonly assigned, concurrently filed Ruffo et al.
application Ser. No. 108,546, at increased gas-to-fiber volume
ratios, various high quality webs can be produced at high
production rates.
The lower portion of the mixing zone 25, i.e., the portion between
the lickerins 92 and 176 and the fiber receiving means 28 is
preferably closed by deflector plates 232 and 234 that are secured
between side plates 38. Because the lower portion of the mixing
zone 25 is wider than the throat portion between the lickerins 92
and 176, the stream 140 having the intimate admixture of long and
short fibers therein tends to decelerate as it approaches the fiber
receiving means 28, and hence it is desirable that the fiber
receiving means 28 be positioned sufficiently closely to the
lickerins 92 and 176 that deceleration of the rayon fibers in the
stream is minimized. While the receiving means 28 is illustrated
substantially immediately below lickerins 92 and 176 in FIG. 3, the
present invention does not require that the fiber receiving means
be positioned this close to the lickerins, and satisfactory webs
have been produced withh the distance between the center line to
center line spacing between the lickerins and receiving means being
as much as 16 inches.
The fiber receiving means 28 is defined by a suction actuated fiber
condensing drum 236 having a foraminous fiber supporting surface
formed by a radially open honeycomb network 238 (FIG. 3) that has
at least one fine mesch screen 240 thereover. In an exemplary
embodiment of the invention, drum 236 has an outer diameter of
approximately 12 inches. Drum 236 is rotated (clockwise in the
illustrated embodiment as indicated by the directional arrow in
FIG. 3) by a motor 242 through a chain drive (FIG. 1) including a
sprocket 244 fixed to the output shaft 246 of the motor 242, a
sprocket 248 fixed to the drum 236, and an endless chain 250. The
fiber receiving means 28 further includes a stationary central
portion 252 having flanges 254 that extend radially outwardly into
sealing engagement with the drum 236. In the embodiment of FIGS.
1-3, one flange 254 is positioned in substantial alignment with
deflector plate 232, while the other flange 254 is
circumferentially beyond deflector plate 234. A conduit 256 (FIG.
2) is connected to stationary portion 252 and to a suitable source
of negative pressure for applying a suction to drum 236 between the
flanges 254. It will be appreciated that the suction of the fiber
receiving means 28 cooperates with the air streams created by the
oppositely rotating lickerins 92 and 176 to provide a pressure
gradient across the mixing zone 25 which draws the individualized
and homogeneously blended long and short fibers onto the drum 236
to build a web. The stream 140 that is produced by the conjoint
action of lickerins 92 and 176 and the negative pressure of the
fiber receiving means 28 is retained at a large enough velocity
that a sufficient means interstitial spacing between the fibers is
maintained in the mixing zone which allows the fibers to remain
intermixed without agglomeration prior to deposition on the fiber
receiving means.
In a typical example of the practice of the invention disclosed
herein, lickerins 92 and 176 of the size set forth above were
rotated at the above mentioned speeds, and 555 pounds of fibers per
hour were fed to the lickerins, with 75 percent of the fibers being
pulp fibers, and 25 percent of the fibers being rayon fibers. The
tooth-to-tooth spacing between the lickerins was 0.25 inches, and
deflector plates 232 and 234 were parallel with one another and
spaced by .625 inches. The air stream 140 had an average volumetric
flow rate of 500 cubic feet per minute (2,250 pounds per hour), and
there was a feed ratio of about 4.05 pounds of air per pound of
fiber. The average volume ratio of air to fiber was approximately
5,000 to 1. Pitot readings were taken at various positions between
deflector plates 232 and 234, and these readings indicated that
stream 140 had a high velocity zone adjacent deflector plate 234.
Visual observations confirmed that a large number of fibers were
entrained in the high velocity portion stream 140, and that a
majority of the fibers were condensed on the screen adjacent
deflector plate 234. With the conveyor 29 operating at a web take
away speed of 200 feet per minute, it was found that an extremely
satisfactory web W was produced having an average weight of about
900 grains per square yard.
It will be understood, of course, that conveyor 29 is intended to
transport the web W to a further processing zone, such as a bonding
zone where a bonding agent may be applied to the web.
The nonwoven webs obtained by the process of the present invention
may be post-treated by any suitable conventional technique, to bond
the web and provide the required strength and coherency
characteristics for a given product. The particular type of bonding
technique chosen will depend on various factors well-known to those
skilled in the art, e.g., the type of fibers, the particular use of
the products, etc. To this end, typical of the conventional
techinques are web saturation bonding, suction bonding, foam
bonding, print bonding, fiber bonding, fiber interlocking, spring
bonding, solvent bonding, scrim bonding, viscose bonding,
mercerization, etc.
In the case of web saturation bonding, the nonwoven web is
generally soaked with a solution or emulsion binder, and
thereafter, the excess fluid is removed usually by mechanical means
(e.g. squeeze rollers and/or vacuum), followed by evaporation. In
the case of suction bonding, a web is treated with a suitable
binder by soaking and the excess removed by means of a vacuum
apparatus. In foam bonding, which is a variation of saturation
bonding and is particularly useful for products requiring good bulk
and through-bonding, a foam binder is employed. In print bonding,
generally employed where softness and absorbency is required, a
bonding agent will be printed onto the web by, e.g. gravure type
rolls. The web can be wet or dry when printed and generally the
binder is a water, solvent or plastisol based one.
In fiber bonding techniques, employed where a percentage of the
fibers in the web are semi-soluble in certain solvents, e.g. hot
water, the web may be bonded by adhesive or by treating the web
with a suitable solvent -- e.g. polyvinyl alcohol. In a variation
of this procedure, if the web includes thermoplastic fibers such as
polypropylene, "VINYON" or low melting polyester, hot roll
embossing calendars may be employed. Still further, in other case,
a low melting spun bonded web may be placed between higher melting
fiber webs and hot calendered. Thermoplastic powders may also be
used in this technique.
In the case of mechanical interlocking bonding techniques, needle
looms are employed in bonding soft fiber webs. Boards of needles
with barbs downwardly pointed perforate the web and entangle the
layers. A variation of this type of bonding technique is stitch
bonding with yarn, as may be accomplished by using an "ARACHNE"
apparatus or with the fibers of the web itself.
As the name implies, spray bonding techniques spray a binder onto
the web which is subsequently passed into a drying chamber. This
type of bonding is particularly useful where high loft is required
in products, e.g. which are suitable for use as air filters.
Solvent bonding employs a solvent which is applied to the web to
soften the fiber surface and render it adhesive. Typical solvent
bonding employs the use of chloral hydrate of DMSO
(dimethylsulfoxide).
In scrim bonding, a scrim layer or yarn layer act as carriers for a
wet or thermoplastic adhesive used to laminate the nonwoven webs to
one or more layers of a substrate, e.g. tissue. In viscose bonding,
which is a special case of print or saturation bonding, cellulose
xanthate is regenerated to pure cellulose on the inner sections of
the fibers forming the nonwoven web. In a like manner, acid
solutions of nylon may be regenerated in situ.
In mercerization bonding techniques, nonwoven webs are bonded using
the uncurling manner of caustic solutions, e.g. caustic soda on
all-cotton nonwoven webs. The fibers unwind to entangle each other
and, thereafter, the resulting product is thoroughly washed.
The above list of bonding techniques is not intended to be
exhaustive as others known to those skilled in the art may be
employed, e.g. bonding with the use of high pressure streams of
water or other fluids directed onto the nonwoven web to cause the
fibers to interlace; or still further, using ultrasonic waves and
laser beams.
In any of the above "dry" bonding techniques, the binder areas may
be of any suitable shape and size and may be continuous or
discontinuous straight, sinuous, curved, or wavy lines; rows of
polygons, circles, annuli, or other regular or irregularly shaped
geometric figures; all of which normally extend across the width of
the nonwoven fabric at various angles to the long direction
thereof. Specific examples of such binder areas are noted in U.S.
Pats. Nos. 2,705,688, 2,705,687, 2,705,498 and 3,009,822.
The amount of binder employed will depend on the type of bonding
technique used and depend on the type and quality of product
desired -- i.e. the amount of binder add-on to the nonwoven web may
be varied according to the technique employed and will vary within
relatively wide ranges, depending to a large extent upon the
intended use of the nonwoven fabric, upon its type, weight and
thickness, as well as upon the specific binder employed. Typically,
the binder areas should not exceed a substantial amount of the
total surface of the nonwoven fabric, if a soft hand, drape and
other textile-like properties and characteristics are desired or
required. In cases where a somewhat different hand and drape is
acceptable, increased binder coverages of up to almost any value,
say 50 percent or even 75 percent, are useful. For some binders, as
low as from about 2 percent to about 20 percent by weight has been
found sufficient; for others, as high as from about 40 percent to
about 70 percent or more by weight has been found preferable.
Within the more commercial aspects of the present invention,
however, binder add-ons of from about 3 percent to about 40 percent
by weight are known in the art to be satisfactory.
The particular type of binder used may be selected from a large
group of binders now known in the industry for such purposes.
Non-migratory binders, such as hydroxyethyl cellulose and
regenerated cellulose, are preferred inasmuch as they yield sharp
and clear boundaries of bonded areas and unbonded areas.
Water-insoluble or water-insensitive binders, such as
melamine-formal-dehyde, urea formaldehyde, or the acrylic resins,
notably the self-cross-linking acrylic ester resin, are also
preferred inasmuch as they are capable of completely resisting a
subsequent aqueous reararanging treatment. Other binders, however,
are also of use and would include polyvinyl acetate, polyvinyl
chloride, copolymers thereof, polyvinyl acrylate, acrylate,
polyethyl methacrylate, polyvinyl butyral, cellulose acetate, ethyl
cellulose, carboxymethyl cellulose, etc.
Following bonding, the nonwoven webs may be treated again according
to conventional procedures for any further desired purpose, such as
for decorative reasons.
Still further, the nonwoven webs may be treated with various types
of resinous coatings according to conventional techniques, or
alternatively by bonding the nonwoven web to various substrates to
provide laminates.
The products obtained by the process of the present invention,
following bonding, find use in various and diverse fields.
Moreover, the random nonwoven webs will now have greater utility
because of their greater availability, and may be used to replace
oriented nonwoven webs where improved machine and cross direction
strength ratios are required. Typical of the uses to which the
products can be put include limited-wear garments such as dresses,
medical and industrial apparel, caps, hospital uses such as for
surgical products, e.g. bandages, alcohol preparation, towelling,
surgical pad covers, sanitary products such as napkins, absorbent
products such as diapers and diaper facings, polishing and buffing
cloths, wash cloths, wiping cloths, etc., consumer products such as
table cloths and place mats, serviettes, book jackets, labels and
tags, mop covers, cosmetic pads, filtration uses such as air
filtration media as well as liquid filtration media in the chemical
and food industries, etc. This is not exhaustive and many different
uses are well known to those skilled in the art.
It should also be understood that while the persons and apparatus
of the present invention have been described in terms of producing
a web that has at least a portion that consists of homogeneously
blended long and short fibers, the present invention comprehends
that the web may be formed entirely either of short fibers or long
fibers. Furthermore, while adjustment means have been illustrated
for varying the positions of the lickerins, the nose bars, the
fiber receiving means, and the feed rolls, these mechanisms may
also be positioned at fixed locations, on the frame in instances
where the apparatus will continuously be operating upon fibrous
materials having the same characteristics.
Also, the web formation characteristics and the dry strength of the
resulting web can be improved by selecting both machine and fiber
materials which produce an appropriate electrostatic attraction
and/or repulsion of one fiber to another and their relationship to
the machine itself. During transport of the fibers through the
mixing zone to the condensing screen, it is desirable to maintain
the voltages between the fibers to reduce coalescence. This can be
accomplished by selecting fibers and machine components that
produce fibers with like charges so as to eletrostatically repel
one another when they are transported in the common air stream. In
some instances, to optimize the buildup of web W on the condensing
screen, fibers can be chosen that will be electrostatically
attracted to one another, and this phenomenon can be especially
important in retaining the air laid web as a unitary mass during
transport from the condensing screen to a further processing
station wherein a binder is applied to the web. It is also a factor
in how the fibers line up relative to one another.
Instead of merely having outwardly diverging deflector plates, such
as 232 and 234, at the lower end of the mixing zone 25, many
different arrangements can be utilized, and several of these are
illustrated in FIGS. 4-12. It will be understood that with the
various arrangements illustrated in FIGS. 4-12, the air flow
patterns at the lower end of the mixing zone can be modified to
control the manner in which the airborne fibers are accumulated on
drum 236. While several different arragements have been
illustrated, these arrangements have been selected for purpose of
example only, and in no way should they be construed as limiting
the invention as defined in the appended claims.
In the embodiment of FIG. 4, deflector plates 260 and 261 at the
lower end of the mixing zone 25 are arranged so that the
intermediate portion of the mixing zone is a narrow channel.
Deflector plate 261 may have rounded portions 261a and 261b at the
upper and lower ends thereof, respectively, to guide the large
number of fibers traveling in the high velocity portion of stream
140, assuming that low gas volumes are flowing through the machine,
as described above. A sealing roll 262 is carried upon an arm 263
that is pivotally mounted to the frame of the machine, and sealing
roll 262 is driven by conventional means, not shown, with the
sealing roll being positioned in alignment with one flange 254 of
the internal portion 252 of drum 236. A baffle 264 is positioned
below deflector plate 260, and includes an inclined portion 265
that extends tangentially with respect to the periphery of drum
236. An extension plate 267 is pivotally connected to the lower end
of deflector plate 260, and the lower end of plate 267 is spaced
from the periphery of drum 236 between the flanges 254.
With the arrangement of FIG. 4, the fibers are deposited on drum
236 essentially between roll 262 and plate 267, with the fibers
being guided around the rounded portion 261b of deflector plate
261. A generally triangularly shaped blocking element B may be
positioned above lickerins 96 and 176 to prevent any dense
particles that are thrown off the lickerins by centrifugal force
from entering the mixing zone. The dense particles collected on
blocking element B preferably are continuously removed from the
machine by means, not shown, such as an air stream, or a screw
conveyor or other means.
In many instances it is desired to concentrate the highest portion
of the suction from the condensing means over a relatively narrow
area in the fiber accumulating zone, and several arrangements for
accomplishing this are illustrated in FIGS. 5-9. In the embodiment
of FIG. 5, the internal portion 252 of the fiber receiving means is
angularly adjustable, and the sealing flanges 254 are spaced apart
by an angle slightly in excess of 90.degree.. A pair of flanges 266
extend inwardly of the internal portion 252 of drum 236, and
baffles 267 are fixed thereto. Baffles 267 includes parallel
portions 268 that extend vertically upwards toward the mixing zone,
so that the fibers are deposited on the drum 236 in a relatively
narrow area with high velocity as determined by the distance
between the baffle portions 268. The thus laid fibers are retained
on the screen by the low velocity and low suction areas outwardly
of baffle portions 268 to firmly hold the web on the screen as it
moves out of the fiber condensing zone. The lower portion of the
mixing zone 25 in the embodiment of FIG. 5 includes deflector
plates 260 and 261 similar to those illustrated in FIG. 4; and a
plate 267a, similar to plate 267 in FIG. 4, is pivotally connected
to the lower end of deflector plate 260, with plate 267a extending
vertically downwardly into engagement with drum 236. As is evident
from FIG. 5, the internal baffles 268 on drum 236 are positioned in
alignment with plate 267a and sealing roll 262. With the
arrangement of FIG. 5, even though the sealing flanges 254 on drum
236 may be positioned more than 90.degree. from one another, the
fibers are deposited on the drum in an extremely narrow zone
determined by the spacing between baffles 268.
In the embodiment of FIGS. 6 and 7, the sealing flanges 254 of the
condensing drum 236 are positioned relatively closely to one
another, and a narrow area of suction application is obtained by a
straight baffle member 271 that is positioned in close proximity to
one of the sealing flanges 254. In the embodiment of FIG. 6, a
stationary tube 272 extends transversely across the frame of the
machine below deflector plate 260, and in alignment with one
sealing flange 254. In the arrangement of FIG 7, the condensing
drum 236 is offset laterally (to the left) relative to lickerins 92
and 176. A plate 273 is pivotally connected to the lower end of
deflector plate 260, and bears against the periphery of drum 236 in
alignment with one flange 254, while sealing roll 262 is positioned
in alignment with the other flange 254. As is evident from FIG 6,
the internal baffle 271 on drum 236 is substantially parallel to
the deflector plates 260 and 261, while in the embodiment of FIG.
7, the baffle 271 is positioned at an angle with respect to the
deflector plates 260 and 261.
In the embodiment of FIG. 8, like the embodiment of FIG. 7, the
condensing drum 236 is offset to the left relative to the vertical
center line of the mixing zone. Deflector plates 260 and 261 define
a relatively narrow passage at the lower end of the mixing zone 25,
as with the embodiments of FIGS. 4-7. The deflector palte 261 in
the embodiment of FIG. 8 does not include a rounded lower end, as
with the previously described embodiments, and instead, a fiber
guiding extension plate 274 is pivotally connected to the lower end
of deflector plate 261. A flexible sealing element 275 is connected
between the lower end of deflector plate 261 and the upper end of
fiber guiding plate 274 to prevent fibers from passing outwardly
therebetween. A driven roll 276 is positioned in sealing engagement
between drum 236 and an extension 277 of deflector plate 260. In
the embodiment of FIG. 8, the highest suction is applied to a
relatively narrow zone of drum 236, and to this end, baffles 278
are secured to spaced parallel, inwardly extending flanges 279 on
the inner portion 252 of drum 236. Baffles 278 include parallel
outer ends 280 that are positioned at an angle with respect to the
center line of the mixing zone 25. A sealing plate 281, shown in
broken lines in FIG. 8, may be pivotally connected to the lower end
of deflector plate 261 and positioned in sealing alignment with
flange 254.
The embodiment of FIG. 9 is similar to the embodiments of FIGS. 6
and 7 to the extend that a single baffle member 271a is provided on
internal drum portion 252, with baffle 271a cooperating with one
sealing flange 254 of the condensing drum 236 to provide a confined
area of high suction on the condensing drum. Baffle member 271a
includes an inclined outer end 271b that extends toward the left
hand sealing flange 254 to provide an extremely narrow gap through
which the highest suction is applied. A sealing member 282 is
positioned in alignment with the left hand sealing flange 254, and
is connected to the lower portion of deflector plate 260 by a
flexible member 283. A sealing roll 284 is positioned in sealing
engagement with drum 236 between baffle portion 271b and the right
hand sealing flange 254.
The embodiment of FIG. 10 illustrates that fixed deflector plates
290 and 292 may be positioned at different distances from the
central line of the mixing zone 25. The embodiment of FIG. 10 also
illustrates a pivotally mounted deflector 294 directly below the
mixing zone 25 for directing the individualized and blended fibers
onto the screen 236.
In the embodiment of FIG. 11, a pivotally mounted deflector plate
296 is provided directly below the mixing zone while a further
pivotally mounted arcuate deflector plate 298 extends between fixed
deflector plate 300 and sealing roll 292. In the embodiment of FIG.
12, the lower end of the mixing zone 25 diverges in both directions
by virtue of pivotally mounted deflector plates 302.
It will be appreciated that all of the webs produced by the
structures illustrated in FIGS. 4-12 will have slightly different
characteristics, but all of the webs will have at least a portion
consisting of homogeneously blended short and long fibers.
Referring now to FIGS. 13-23, which illustrate an embodiment of the
invention developed by A. Farrington and which is described and
claimed in detail in the above mentioned Farrington application,
pulp is introduced into the system in the form of a pulpboard 310,
which is directed between a plate 311 and a feed roll 312.
Connected to the lower part of plate 311 is a nose bar 313 for
providing an anvil against which the pulpboard is directed during
the individualizing step. The nose bar 313 has a sidewall 314 that
can be made relatively flat, since, due to the integrity of the
pulpboard, it is unnecessary that the plate 311 be designed to more
accurately direct the pulp into intimate contact with the lickerin
317 that is used to individualize the pulpboard into short fibers.
The bottom wall 315 of the nose bar 313 is angularly disposed
relative to the sidewall 314 and is spaced a short distance from
the teeth 316 of the lickerin 317 to define a passage 318 through
which the pulpboard is moved during the individualizing operation.
The pulpboard is individualized into fibers by the teeth 316 of the
lickerin 317 acting on the pulpboard which is directed and retained
thereagainst by the nose bar 313.
Returning to the pulpboard feeding system of FIGS. 13-23, the
pulpboard is fed into the system by a feed roll 312 that is
journalled in a bracket 319 that is eccentrically mounted at 320 to
permit adjustment of the feed roll relative to the pulp lickerin
317 and nose bar 313. The bracket 319 and feed roll 312 are biased
to direct the pulpboard toward the nose bar 313 by a spring 322
that is located between bracket 319 and head 324a of bolt 324 which
extends through a hole in the bracket 319, and is secured in place
in plate 311. The pivotal movement of the bracket 319 is limited by
a set screw 328 that is threaded into and through bracket 319 and
engages plate 311. The spring 322 insures that feed roll 312 will
be maintained in contact with pulpboard 310 to insure that the
pulpboard is into contact with lickerin teeth 31 of lickerin 317.
This design accommodates varying thicknesses of material that can
be used in this system.
The feed roll 312 is secured to a shaft 330 that is suitably
supported for rotation by a variable drive means, a portion of
which is shown schematically in FIG. 14. The speed at which the
feed roll is operated is determined by the rate at which pulp is to
be fed into the system. A number of the mechanisms employed for
supporting the rollers, lickerins, and so forth, are shown
generally in FIG. 14 and they will be referred to when they will
aid in understanding the present invention.
During operation, the pulpboard 310 is fed into contact with the
lickerin teeth 316 adjacent the nose bar 313. The lickerin 317 is
mounted on shaft 331, which is driven at a very high speed (such as
6,000 rpm) by suitable drive means (not shown).
After the fibers are individualized by the lickerin, they are
entrained in an air stream and directed through a duct 332 formed
between the lickerin teeth 316 and a sidewall 333 into a mixing
zone 334. The fibers are then directed onto a condenser 350 where
they form a web. The duct 332 and mixing zone 334 form part of a
flow duct.
Referring now to the rayon fiberizing system which exists on the
right side of FIG. 13, there are shown mechanisms that control the
feeding of the rayon 335, a number of which mechanisms are
substantially identical to those used on the pulp side of the
system. Identical components are given the same numbers as those
applied on the pulp side of the apparatus.
The rayon is positively introduced into the clothing of the rayon
lickerin 338 to insure that the rayon lickerin teeth 339 will pick
the rayon up from the carded lap 335, and to this end, the nose bar
336 is curved at 336A to essentially conform to the adjacent
circumference of the rayon feed roll 337. The rayon fibers that are
thus picked up from the lap are positively maintained in position
relative to the feed roll 337 until the fibers are disposed
immediately adjacent the teeth 339 of the rayon lickerin 338, which
teeth will then serve to comb the fibers from the rayon source.
The individualized rayon fibers that are combed from the rayon
source are then moved into duct 340 located between sidewall 342
and lickerin 338. The duct 340 leads into mixing zone 334 where the
rayon fibers are blended with the pulp fibers.
The doffing of the fibers from the lickerins 317, 338, the air
entrainment of the previously individualized fibers, and the
conveying of the fibers through the ducts 332, 340 and into the
mixing zone 334 are accomplished by high velocity air streams that
are introduced into the system by being pulled in through parallel
passages 344, 346 by a suction fan (not shown) located in the
housing 348. The suction fan is disposed beneath the condenser 350
that is located at the bottom of the air flow duct 352 that
interconnects the mixing zone 334 with the condenser 350. The
parallel flow paths 344, 346 lead to lickerins 317, 338,
respectively, to direct high velocity air against their teeth to
doff any fibers clinging thereto. The air with entrained particles
therein then flows through ducts 332, 340, respectively, into
mixing zone 334 from where it flows through duct 352 and condenser
350. The fiber particles entrained in the air stream are deposited
on the condenser in the form of a web.
The condenser 350 on which the fibers are formed into a web
consists of an endless movable mesh screen conveyor 381 directed
over four pulleys 382, 384, 386 and 388 which conveyor is driven by
suitable drive means (not shown). The conveyor 381 slides over the
housing 348, which contains an aperture 349, through which the air
is sucked into the housing via conduit 389 that leads to the
suction fan (not shown). The position of pulley 388 can be adjusted
to provide suitable tension on the screen. The speed at which the
condenser is moved will determine the thickness of the web being
formed. The condenser leads to another conveyor belt 390 on which
the web is carried to another station for further processing.
In order to help seal off duct 352 and maximize the efficiency of
the suction fan being used, a pair of vertically extending plate
members 366, 368 are employed to define two outer wall portions of
the duct 352 between the lickerins and the condenser. The lower
portion of the duct 352 between the plates 366, 368 and the
condenser 350 are essentially sealed off by rollers 360 that are
rotatably mounted on pivotally mounted arms 370, 372 that are
connected at their upper amrs to a shaft 374. The weight of the
rollers and arms tend to maintain the rollers in a sealing
condition to minimize the introduction of air between the rollers
369 and the plates 366, 368 and condenser 350.
Referring now to FIG. 16, there is illustrated a sealing mechanism
that acts to seal the flow duct 352 along the edges of the web
being formed. In each side, there is provided a floating seal 376
that is biased into contact with the web by a spring 378. The seal
376 is reciprocately mounted in a recess 379 defined in a side
plate 380. This mechanism is duplicated on the opposite side to
prevent introduction of air into the suctiion fan other than down
through the flow duct 352.
The condition and direction of the air flowing through the system
and the ratio of volume of air to volume of fibers has an effect on
the particular webs being formed. For example, it can be
appreciated that the quantities of fibers to be conveyed would to a
certain extent determine the amounts of air that would be directed
against the particular lickerin used for fiberizing a given
material. Thus, when forming a web of 90 percent pulp fibers and 10
percent rayon, it may be desirable to have substantially higher
quantities of air introduced to convey the pulp than to convey the
rayon. In order to control the relative quantities of air directed
to the pulp and rayon lickerins while insuring that the air so
introduced aids in doffing the fibers from the lickerins, the air
passages 344, 346 are appropriately designed and located.
Referring first to air passage 344, it is seen that this air
passage is vertically disposed with the lower end being located
immediately adjacent the teeth 316 of the pulp lickerin 317. In
order to insure constant thickness across the width of the web it
is desirable that the air flow across the axial length of the
lickerin be uniform. Also, the air may improve doffing of the
fibers from the lickerin if it is in a generally turbulent
condition. To provide for turbulence while insuring that the air is
uniformaly distributed across the lickerin there is provided at the
lower end of passage 344 a wedge shaped restrictor 354 that is
suitably secured to plate 356 that forms a side wall of passage
344. The restrictor 354 defines a throat 358 through which the air
pulled through the passage 344 must pass. This throat portion 358
brings about a low pressure drop flowing therepast and raises the
velocity of the air before it contacts the pulp lickerin teeth 316.
The high velocity air aids in doffing the pulp from the lickerin
and insures that the air will be turbulent to aid in the mixing of
the two fibers in the mixing zone 334. The wedge shaped restrictor
354 does not substantially effect the quantity of air being sucked
through the passage and insures a substantially uniform air
distribution across the full width of the orifice to make for a
more uniform web.
In a system where there is a web being formed that is made up of 90
percent pulp fibers and 10 percent rayon fibers there will of
course be substantially less air needed to process the rayon than
the pulp. Assuming that the passage 344, 346 have the same
cross-section, then it will be necessary to provide a substantial
obstacle to the flow of air through the passage 346 to provide for
the desired unbalanced air flow through the system.
In the passage 346 there is a restrictor provided in the form of an
adjustable block 360 which has substantial length and fills up a
major part of passage 346. Between the plate 311 and block 360
there is defined a narrow passage 362. The block 360 results in
setting up a turbulent condition for the air flowing into duct 340
and severely limits the quantity of air flowing thereto, as
compared to the air flowing through the passage 344 and past
restrictor 354. Suitable positioning of the block 360 can be
accomplished by adjusting mechanism 364. Another way that the air
directed to the lickerins can be controlled would be by adjusting
the width of the passageways 344, 346 by the insertion of blocks of
varying widths therein.
The air that is directed downwardly through the passage 344 and
past the restrictor 354 impinges with a high velocity against the
teeth 316 of the lickerin 317 just as the lickerin teeth pass the
nose bar where the pulp fibers have been individualized. The high
velocity air which is moving faster than the lickerin teeth moves
through the duct 332 where it acts to doff the fiber from the
lickerin teeth in conjunction with the centrifugal force imposed on
the fibers due to the high speed of rotation of the lickerin. The
air in duct 332 entrains the fibers therein and conveys them as
previously mentioned. The duct 332 is directed downwardly at
approximately a 45.degree. angle which will lead it into direct
communication with the high velocity air flowing past the rayon
lickerin.
On the rayon side of the system, the high velocity air passing
through passage 362 similarly acts to doff the fibers from the
teeth 339 of the rayon lickerin 338 and entrain the fibers therein.
The air stream is moving at a high velocity at approximately a
45.degree. angle toward the mixing chamber 334 wherein it comes
into impelling relationship with the entrained pulp fibers in the
air stream moving downward through duct 332. These air streams are
moving at a very high rate of speed and the air is in a turbulent
condition with the result that when these two streams intermix the
fibers entrained therein will come into blending relationship and
form a homogeneous mass in which the fibers are randomly oriented.
The blended fibers will then move down through the duct 352 onto
the condenser 350 where a randomly oriented fully homogeneous web
will be formed.
In the illustrated embodiment it will be observed that the
cross-sectional area of the chamber 334 is generally equal to the
sum of the cross-sectional areas of the ducts 332 and 340. However,
it is not essential to the present invention that these
relationships be maintained.
In a particular example, a fully homogeneous web has been formed
when the volume of air to fiber ratio in on the order of 5,000 to
1. However, with this apparatus when the volume to air ratio is
substantially changed, the type of web capable of being obtained
will also change. For example, it has been found that when the
volume of air to fiber ratio flowing through the mixing chamber 334
is on the order of 12,000 to 1 or greater (as is explained in the
Ruffo et al. application mentioned above) a web having a different
construction will be formed. At such a ratio the fibers in the high
velocity air streams will tend to cross each other with the result
that a web will be formed that has a predominance of wood pulp on
one face of the web and a predominance of rayon on the other face
of the web with a transition zone in which the predominance of the
respective fibers diminishing throughout the thickness of the
web.
In addition to being able to provide a completely blended
homogeneous web or a web in which there is a predominance of fiber
on each of the faces and a transition zone therebetween, the
apparatus is desinged so that other types of webs can be formed
when the volume of air to fiber ratio is on the order of 5,000 to 1
and alternatively homogenous webs can be formed when the volume of
air to fiber ratio is on the order of 12,000 or higher.
The various types of webs listed above, as well as others referred
to hereinafter, can be obtained by the introduction of a baffle
into the mixing zone which controls the mixing of the two separate
air streams moving down ducts 332 and 340. The structure of this
baffle will be first described after which the different webs that
are formed depending on the position of the baffle will be gone
into in detail.
The baffle 400 is constructed to extend down the center of the
apparatus into the mixing chamber between the two lickerins and
essentially consists of an elongated flat plate that extends the
full width of the machine. FIG. 13 illustrates the baffle in the
fully withdrawn position, FIG. 17 shows the baffle located
generally in alignment with a plane drawn through the axis of the
lickerins, FIG. 18 shows the baffle extended downwardly below the
lickerins and FIG. 19 shows the baffle disposed immediately
adjacent the condenser.
The positioning of the baffle is accomplished by a pair of gears
402 mounted on a shaft 404 (see FIG. 14) that meshes with racks 406
secured to the baffle 400. Leakage of air past the baffle is
prevented by sealing and guide members 408, 410.
When the baffle is moved down into one of the positions illustrated
in FIGS. 17 or 18, it can be apprecaited that the separate flow
streams containing entrained particles in ducts 332 and 340 are
prevented from intermixing until they pass below the bottom of the
baffle. The particular location of the baffle will determine how
much blending will take place between the streams of fibers in
ducts 332 and 340. As the baffle is moved downwardly into the duct
352 and with the volume of air to fiber ratio on the order of
5,000, a web will be formed in which the bottom layer will be made
up of substantially all wood pulp fibers, the upper layer will be
substantially all rayon fibers and the intermediate layer will be a
homogeneous blend of the two fibers. The web so formed will of
course of made up of fibers that are randomly oriented and thus
isotropic. As the baffle is moved further and further down toward
the condenser, there will be less of an intermediate homogeneous
web portion and the outer sections of the web will be
proportionately thicker. With the baffle all the way down as shown
in FIG. 22, a two layered web of short and long fibers will be
formed with the fibers at the interface being interconnected.
When the volume of air to fiber ratios are increased to something
on the order of 12,000 to 1 or greater and with the baffle in the
position generally as shown in FIG. 17, a fully homogeneous web
will be formed.
As the baffle 400 is moved down to the position shown in FIG. 18
and ratios of 12,000 to 1 or more are maintained, the crossover of
fibers will be somewhat reduced and a web will be formed that has a
predominance of pulp on the bottom and rayon on the top with a
transition zone in between where the quantity of rayon diminishes
toward the pulp side and the quantity of pulp diminishes toward the
rayon side. The fiber as so formed is separate from that which is
formed with these volume to air ratios when the baffle is above the
position shown in FIG. 17. The web so formed during this method of
operation is one in which the bottom layer of the web will be
predominantly rayon and the top layer of the web will be
predominantly pulp with the transition zone therebetween wherein
the quantity of pulp reduces as it approaches the rayon side and
the rayon reduces as it approaches the pulp side.
In the drawings FIGS. 20-23 schematically illustrates some of the
various types of webs that can be formed with the apparatus
illustrated in FIGS. 13-16. FIG. 20 is intended to be a graphic
illustration of a fully homogeneous web W. FIG. 21 shows a
cross-section of a web 412 that is made up of a layer 414 that
contains essentially all staple fibers, layer 416 of pulp fibers
and layer 418 which is a homogeneous blend of staple and pulp
fibers. FIG. 22 shows a cross-section of a web 434 made up of
separate layers of staple fibers 436, and pulp fibers 438 which are
interlaced at their interfaces. FIG. 23 shows a cross-section of a
web 440 in which the upper layer 442 has a predominance of pulp
fibers and the bottom layer 444 has a predominance of staple fibers
and a transition zone therebetween in which the predominance of
staple fibers decreases as it approaches the pulp layer 442 and the
predominance of pulp fibers decreases as it approaches the rayon
layer 444.
The following examples apply to the apparatus illustrated in FIGS.
13-16.
Example 1. A nonwoven web of a homogeneous blend of randomly
oriented short pulp fibers and staple rayon fibers was formed in
which, by weight, 90 percent of the fibers were pulp and 10 percent
of the fibers were rayon.
The short fibers were extracted from pulpboard and the rayon fibers
came from a rayon picker lap in which the average fiber length was
1 9/16 inches, with a denier of 1.5.
Lickerins 317 and 338 were approximately 9 1/2 inches in diameter
and were rotated at about 6,000 and 3,000 rpm, respectively, and
the lickerins were spaced from one another by about 1 1/2 inches.
Lickerins 317 and 338 were spaced from duct walls 333 and 342,
respectively, by about three-fourths inch. Lickerins 317 and 338
were about 18 inches long and a total of 700 pounds per hour of
fibers were fed to the lickerins. Deflector plates 366 and 368 were
spaced from one another by about 4 1/2 inches. The average volume
ratio of air to fiber was approximately 5,000 to 1 in the common
air stream.
With the web take away mechanism operated at a speed of 125 feet
per minute, and with baffle 400 in the withdrawn position, a
homogeneous web of randomly oriented fibers was produced having a
weight of approximately 4,000 grains per square yard.
Example 2. The basic machine parameters of Example 1 were repeated,
with the exception that the fiber feed was controlled to provide a
feed rate of 180 pounds of fibers per hour 50:50 (by weight)
mixture of pulp and rayon fibers, and the process employed a
70,000:1 volume ratio of total gas to total fiber in the combined
stream. Lickerin 317 was rotated at about 5,500 rpm and lickerin
338 was rotated at about 2,800 rpm. The resulting web weighed
aproximately 550 grains per square yard, and was removed from the
condensation zone at approximately 150 feet per minute.
With the above volume ratio, even though the divider plate 400
remained withdrawn, the resulting product was found to consist of a
predominance of rayon fibers at one face of the product and a
predominance of pulp fibers at the opposing face of the product,
with a decreasing amount of pulp and rayon fibers from the faces at
which they predominate, repsectively, to the opposed faces. This
"transition" feature was found to be substantially uniform from
face to face. The existence of this "cross-over" product was
confirmed by high speed movies taken through transparent end plates
of the machine which confirmed that a majority of the fibers from
the individual streams crossed over at the point where the
individual streams were joined to form the common carrier
stream.
Example 3. The machine parameters of Example 3 were essentially the
same as those in Example 2, except that an 80:20 (by weight)
mixture of short pulp fibers and staple rayon fibers were fed to
the respective lickerins. In this regard the pulp feed rate was
approximately 1,000 pounds per hour and the rayon mately 30,000 to
1. The take away mechanism was adjusted to provide a take away
speed of approximately 550 feet per minute, and the resulting web
had a weight of approximately 1,400 grains per square yard.
The resulting web was found to be a homogeneously blended nonwoven
web of randomly oriented fibers. The cross-over product, such as
that obtained in Example 2, was prevented because of the degree of
interference of the baffle 400 with the separate gas streams.
* * * * *