U.S. patent number 3,859,156 [Application Number 05/434,340] was granted by the patent office on 1975-01-07 for method for laminating warp and weft of fibrous materials in a wet manner.
This patent grant is currently assigned to Polymer Processing Research Institute Ltd.. Invention is credited to Haruhisa Tani, Setsuya Tsuyama, Masahide Yazawa.
United States Patent |
3,859,156 |
Yazawa , et al. |
January 7, 1975 |
METHOD FOR LAMINATING WARP AND WEFT OF FIBROUS MATERIALS IN A WET
MANNER
Abstract
A laminate of warp and weft is prepared according to an
efficient wet process by putting webs of wefts each consisting of a
number of fibrous materials arranged in order in a flat layer and
in a certain width, and cut to a length corresponding to the width
of a warp web consisting of a number of fibrous materials arranged
in order in a flat layer and in a certain width, on the surface of
a circulating endless belt wetted with water to attach the cut weft
webs onto the surface of the belt one by one with a certain spacing
during the upper circulating course of the belt while maintaining
the original state of the arrangement of the web by the surface
tension of water; and dropping the cut webs one by one from said
endless belt during the lower circulating course of the belt, upon
the warp web, travelling crosswise below the circulating belt with
a small gap, by pushing linear edges which are situated inside the
back-surface of the cut weft web on the carrying belt thereof,
crosswise to the cut weft webs and arranged in a number of rows,
downward from the surface level of the belt, to successively attach
the cut weft webs onto the warp webs and then bonding both the
webs.
Inventors: |
Yazawa; Masahide (Tokyo,
JA), Tani; Haruhisa (Tokyo, JA), Tsuyama;
Setsuya (Tokyo, JA) |
Assignee: |
Polymer Processing Research
Institute Ltd. (Tokyo, JA)
|
Family
ID: |
11684498 |
Appl.
No.: |
05/434,340 |
Filed: |
January 17, 1974 |
Foreign Application Priority Data
|
|
|
|
|
Jan 18, 1973 [JA] |
|
|
48-8123 |
|
Current U.S.
Class: |
156/265; 28/100;
156/519 |
Current CPC
Class: |
B32B
38/0004 (20130101); D04H 3/04 (20130101); B32B
5/26 (20130101); B32B 5/022 (20130101); Y10T
156/133 (20150115); Y10T 156/1077 (20150115); B32B
2305/20 (20130101) |
Current International
Class: |
D04H
3/02 (20060101); D04H 3/04 (20060101); B32b
031/00 () |
Field of
Search: |
;28/1CL ;19/163
;156/264,265,163,300,164,302,176,303,180,309,181,517,521,519,307,281,313,285
;214/6B ;161/55,60 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Drummond; Douglas J.
Assistant Examiner: Gallagher; J. J.
Attorney, Agent or Firm: Armstrong, Nikaido & Wegner
Claims
What is claimed is:
1. In a method for laminating warp and weft webs of elongated
fibrous materials, an improvement in a wet manner, which
comprises,
a. cutting a weft web consisting of a number of elongated fibrous
materials arranged in parallel in a plane of a given width to a
length corresponding to the width of a warp web also consisting of
a number of elongated fibrous materials arranged in parallel in a
plane of a given width, one by one, to give cut weft webs;
b. attaching the resultant cut weft webs onto the surface of an
endless belt wetted with water and circulating along an upper
horizontal course and a lower one at a speed faster than the
feeding speed of the weft web, successively in said upper
circulating course, leaving a predetermined space between each of
said cut weft webs, while maintaining the original arrangement of
said fibrous materials in the weft web through surface tension of
water wetting the surface of the belt;
c. bringing the cut weft webs attached onto the surface of the belt
to said lower circulating course one by one;
d. at the instant whenever one cut weft web comes to a position
overlapped wholly with the warp web after overlaid, which is
travelling horizontally and crosswise below said lower circulating
course of the belt at a distance apart therefrom, pushing off and
simultaneously knocking off the said cut weft web attached onto the
belt, from said belt towards the warp web over the whole length and
width thereof, by rapidly pushing down and returning back a number
of rows of linear edges which are situated behind the cut weft
webs, inside the circulating surface of the cut weft web and
crosswise to the circulating direction of the belt and are
circulated at substantially the same speed as that of the belt, and
thereby successively cross-overlaying the cut weft webs on the warp
web one by one without leaving any gaps therebetween; and
e. bonding the whole into a laminate of warp and weft.
2. A method according to claim 1, wherein the weft web is fed and
cut into cut weft webs, one by one, at a position close to and
above a circulating endless multiple belt consisting of a number of
narrow flat belts arranged in parallel in a width corresponding to
the width of the weft web, all of which narrow flat belts are
guided and circulated by a pair of roller means and made to keep
the center line of circulation thereof by at least one roller means
of the pair consisting of corresponding number of crowned pulleys
of the equal diameter having the same center axis, and the
resultant cut weft webs are fed successively onto said belt wetted
with water from the forward cut end of the webs to attach the cut
weft webs onto the belt and are made to travel together with the
belt leaving a predetermined space between each other, while
maintaining the arrangement of the fibrous materials of the
original weft web and brought to the lower circulation course of
the belt.
3. A method according to claim 1, wherein the weft web is fed onto
a water-wetted lattice endless belt circulating at a speed faster
than the feeding speed of the weft web and consisting of a number
of rigid lattice elements arranged in parallel at predetermined
intervals, each end of which elements is connected to each one of a
pair of circulating chains in parallel, respectively; said lattice
belt has an overall peripheral length corresponding to an integer
times the length of each of cut weft web-carrying sections having a
length longer than that of the cut weft webs, and having at the
rear end of each of said sections, a site accommodating parts of a
weft-cutting means, and the weft web is cut by the weft-cutting
means at the rear end of each of said sections, into cut weft webs
one by one while sliding on said lattice belt wetted with water,
whereby the arrangement of fibrous materials of the original weft
web is kept sufficiently as it was and the resulting cut weft webs
are successively attached onto the belt, travel together with the
lattice belt leaving a predetermined space between each other and
are brought to the lower circulating course of the belt.
4. A method according to claim 1, wherein each one of the cut weft
webs attached on the cut weft web-carrying belt wetted with water
is pushed and knocked off from said belt by a number of rows of
strings as linear edges, in the lower circulating course of the
belt.
5. A method according to claim 1, wherein each one of the cut weft
webs attached on the cut weft web-carrying belt wetted with water
is pushed and knocked off from said belt by a number of rows of
linear tip edges of thin plate as linear edges, in the lower
circulating course of the belt.
6. A method according to claim 1, wherein the warp web is made to
travel while being attached onto a warp web-carrying belt means
which is wetted with water and traels at substantially the same
speed as the feeding speed of the warp web, thereby to absorb the
impulsive force of the falling cut weft webs and to prevent the
warp web and cut weft webs from disturbing the arrangement of
fibrous materials thereof.
Description
DESCRIPTION OF THE INVENTION
This invention relates to an effective method for a high speed
production of non-woven fabrics of laminated warp and weft webs.
More particularly, it relates to a wet process for laminating warp
and weft fibrous materials which comprises putting cut weft webs
consisting of several hundreds or more of elongated fibrous
materials arranged in a broad width, cut into a required weft
length and attached on a wet belt, circulating along an upper and a
lower horizontal circulating courses at a speed faster than the
feeding speed of the weft web, upon a travelling warp web which
consists of several hundreds or more of elongated fibrous materials
arranged in a certain width e.g., 1 m, by means of pushing down a
number of parallel linear edges positioned crosswise to the cut
weft web, from the backside thereof, to knock said web off the belt
over the whole length and width of the cut weft web towards the
warp web, and if necessary while utilizing a suction force from the
back-side of the warp web, thereby to overlay each of the cut weft
webs one by one crosswise upon the warp web without forming any gap
between each of the cut weft webs on the warp web and
BONDING BOTH THE WEBS, USING ADHESIVES, IN THE MANNER DIFFERENT
FROM THAT OF ORDINARY WOVEN FABRICS IN WHICH CASE EACH YARN FOR
WEFT IS FILLED BY A SHUTTLE ONE BY ONE.
In the specification of the present invention, a thin, flat layer
material composed of several hundreds or more of elongated fibrous
materials substantially arranged in parallel in a certain broad
width, say 1 meter wide, is denoted for simplicity as "a web;" a
web used as a warp-side component is denoted as "warp web" and that
used as a weft-side component as "weft web;" that of a weft web cut
into a required weft length is denoted as a "cut weft web;" and a
product obtained by crossoverlaying weft webs on a warp web and
bonding both the webs in one sheet of a laminate, is denoted as
"laminate of warp and weft" or "non-woven fabrics of warp and weft"
case by case.
We proposed once a dry laminating process of non-woven fabrics of
warp and weft in which a weft web is gripped at its forward tip end
by a gripping means, transported over a warp web, cut at the
backward end thereof at the position being wholly overlapped with
the warp web and made to fall upon the warp web by a suction force
from back side of the warp web to be laminated, but this process
had such a drawback that the arrangement of fibers is liable to be
disturbed due to the static electricity and turbulence of
environmental air at the time of cross-overlaying.
According to the present invention, since the cut weft web adheres
to a wet belt, maintaining the arrangement of fibers at the time of
feeding by the surface tension of water, and since the warp web
also in most cases holds its arranged state by another wetted belt
as explained later, there is no disadvantage of disturbance of
fiber arrangement caused by static electricity and turbulence of
surrounding air at the time of cross-overlaying as often
encountered in the dry laminating process, and thus it is a notable
feature of the present invention that such a high production rate
of non-woven fabrics of warp and weft as about 100 m.sup.2 /min.
can be easily attained with a high accuracy of fiber
arrangement.
As a means for knocking cut weft webs off the weft-carrying belt
onto warp web, there are provided a number of linear edges which
are situated crosswise to the weft web, on the back side of wet cut
weft web adhering to the belt and inside the course of circulation
of said cut weft web, and circulated at a speed same with that of
said belt. The linear edges are pushed down and drawn back over the
entire length and entire width of the cut weft web whenever the cut
weft web comes to the position exactly crosswise overlapped with
the warp web after overlaid.
Several effective examples of feeding method of cut weft webs and
kind and fixing manner of linear edges which are varied according
to the kind of belt, as explained later, are also the features of
the present invention.
The fibrous materials useful in the method of the present invention
include spun yarns, filament yarns, bristles, stretched tapes,
split yarns, uniaxially stretched films of a broad width, split
webs which are composed of narrow tapes or fibers of reticular
structure obtained by splitting uniaxially stretched films of a
broad width, or webs of spread split webs into several times the
original width, fine metal filament yarns, glass fiber yarns,
carbon fiber yarns, carded webs having continuity and some extent
of orientation of fibers, etc. made of natural or artificial
materials of organic or inorganic origins.
Further these fibrous materials are used as one kind of material or
as a combination of more than one kind.
When the fiber arrangement of a cross-overlaid product is fixed for
uses as non-woven fabrics, they are processed according to several
different ways. Namely, fibrous materials for warp and weft webs
are sized in advance and subjected to cross-overlaying or adhesive
films are placed between warp and weft in the cross-overlaying step
and then fixing of fiber arrangement thereof is carried out by
heat-pressing adhesion, or warp and weft webs are sized and dried
after cross-overlaying and then fixing of fiber arrangement is
carried out by heat-pressing adhesion.
When non-woven fabrics of laminates of warp and weft are sized,
scattering of a small amount of (2-6g/m.sup.2) of pulp fibers
having a length of 1-3 mm or natural or aritifical short fibers
having a length less than 5 mm onto the non-woven fabrics before
winding-up can completely prevent blocking between wound-up layers
in case where a soft and tacky sizing agent is used, and at the
same time, the non-woven fabrics are strengthened by such scattered
and attached short fibers. If carded staple fiber webs of slightly
longer fibers are attached, the open spaces of crossed fiber
materials of warp and weft layers are subdivided further by short
fibers to give non-woven fabrics which do not permit small granular
material or powder to come out therethrough.
For attaching fibrous materials of a warp or weft web onto a belt,
a liquid, though it does not matter what kind of liquid may be
used, generally water or a liquid obtained by adding a surfactant
to water to improve the spreading or wetting property of water is
used. It goes without saying that water which contains a sizing
agent or the like as a viscidity-promoting agent is useful under
certain circumstances.
The point is, however, that a web of fibrous materials is attached
onto a belt by the surface tension of water to keep the arranged
state thereof at the time of feeding on the belt, and in case of a
cut weft web, in particular, it would be good if the surface of the
belt is wetted with thin water film to get such an extent of
adhesion that when a cut weft web placed upon the travelling belt
in the upper circulating course, is brought to the lower
circulating course, the cut weft web attached to the belt is kept
without falling down upon the travelling warp web by its own weight
till the attached weft web is peeled off from the belt by the
pushing down action of the linear edges which are supposed to knock
off the cut weft web from the belt and made to drop upon the
travelling warp web.
Several embodiments of the method of the present invention will be
described by referring to attached schematic drawings.
FIG. 1 is a schematic view of the vertical cross-section of the
apparatus useful for putting one embodiment of the present
invention into practice.
FIG. 2 a is a schematic view of the cross-section of a web-carrying
multiple belt composed of a number of narrow belts when it is
running in the direction perpendicular to the plane of paper.
FIGS. 2b, 2c and 2d are schematic views showing the progress of
relative positions of knocking off of water-adhering cut weft web
from the belt toward and upon warp web by strings as linear
edges.
FIGS. 3a and 3b are the vertical cross-sectional views of one end
part of a lattice element including a device for pushing down and
drawing back a string as one of linear edges for knocking off a cut
weft web when a belt for carrying cut weft webs is a lattice
belt.
FIGS. 3c, 3d and 3e are the vertical cross-sectional views showing
the relative positions of knocking off a cut weft web from the belt
by the movement of strings as linear edges in case of a lattice
belt.
FIG. 4a is a vertical cross-sectional view of a lattice belt
including pinch rollers, a weft web cutter and a ski edge in the
present invention.
FIG. 4b is a vertical cross-sectional view of a knife type weft web
cutter working upon weft web.
FIG. 4c is a vertical cross-sectional view of a melt type weft web
cutter working upon weft web.
FIG. 5a is a vertical cross-sectional view of one lattice element
of a lattice belt and edges of U-form thin plate during the upper
circulating course of a belt. FIG. 5b is a vertical cross-sectional
view of the lattice element of FIG. 5a during the upper circulating
course of a belt viewed from the direction perpendicular to the
section shown in FIG. 5a.
FIG. 5c is a vertical cross-sectional view of one lattice element
of a lattice belt and edges of U-form thin plate during the lower
circulating course of a belt.
FIG. 5d is a vertical cross-sectional view of the lattice element
of FIG. 5c during the lower circulating course of a belt viewed
from the direction perpendicular to the section shown in FIG.
5c.
FIG. 6 is a vertical cross-sectional view of the apparatus useful
for an embodiment of the present invention in which cut weft webs
are dropped upon an adhesive foil.
In FIG. 1 showing one embodiment of the present invention, belt 2
is situated above warp web which is arranged in a certain width and
moving horizontally in the direction perpendicular to the surface
of paper, and is circulated along an upper circulating horizontal
course and a lower one through guide rollers 3 and 3' in the wefts
direction which is crossing the warps horizontally and mostly at
right angle.
The surface of this belt is coated with a uniform thin water layer
in an appropriate amount transferred from the bristles of brush
roller 6, contacting with revolving roller 5, the lower half of
which dips in surfactant-containing water vessel 4.
Weft web which is arranged in a width similar to that of the warp
web is continuously fed, through pinch rollers 7 and 7' and a
cutting means, onto the belt at a position in the upper circulating
course thereof, which belt is circulating under the feeding course
of the weft web at a speed faster than the feeding speed of the
weft web.
After passing through the cutting means, at first the forward tip
ends of the weft web and then successive parts thereof are caught
onto the belt surface by surface tension of the water coating the
belt while being slided on the belt. Whenever the weft web passes
through the cutting means by the length corresponding to the width
of the warp web, the cutting means acts to cut the weft web into a
cut weft web so that the fiber arrangement of the weft web at the
time of feeding is practically maintained as it was in the cut weft
web on the belt. After being cut, the cut weft web is attached onto
the belt and travels together with it, leaving a space
corresponding to the difference between feeding speed of the weft
web and circulating peripheral speed of the belt, between each
other.
The cutting means shown in FIG. 1 illustrates one example of such
cutting means. It is constructed with a combination of lattice belt
9 having a peripheral length equal to that of cut weft web and
another lattice belt 10 whch is circulating in engagement with
lattice belt 9, as shown in the drawing. If it is so arranged that
one of the lattice elements forming lattice belt 9 is replaced by a
melt cutter, that is, heated rod 12 heated by electric current sent
through leading wire 11 from a source, the weft web supplied
continuously by roller 7 and 7' into the part between lattice belts
9 and 10 are cut to a unit length of cut weft web per one
revolution of belt 9 and transferred onto belt 2 travelling in the
vicinity below belt 9.
Inside the surface of the circulation course of cut weft web 13
attached onto the belt 2, strings 15 under tension as an embodiment
of linear edges of the present invention, spaced apart by a fixed
distance of 20 - 50 mm from each other and further contacting with
the belt are circulated at a circulation velocity same with that of
the belt and in this embodiment, cut-weft web adheres not only to
these strings, but to the belt by means of water.
When the circulating belt is a lattice belt in which a number of
lattice elements are arranged in parallel and in the direction
perpendicular to the circulation direction of the belt as in case
of the embodiments of the present invention which are described in
detail later, strings as linear edges can be installed in the gaps
between the lattice elements inside the top surface of the lattice
elements, and inside the back side of the cut weft webs and
slightly apart therefrom. Accordingly, in the former case, unless
extremely fine wire materials such as piano wire, bristle or the
like is used, in other words if a thick string is used, the
horizontal adhesion of cut weft webs to the belt surface is
prevented, but, as in the latter case where linear edges are
arranged in the gaps between lattice elements, the use of thick
wire materials, rubber cords, thin plate edges or the like does not
influence the adhesion of cut weft webs onto the belt surface.
Whenever weft web 13 on belt 2 is brought to the position where the
web is wholly overlapped with the warp web after overlaid during
the lower circulating course of the belt, ski edges 14 which
perform a reciprocating movement off and to the belt passage for
pushing tensioned strings forming one kind of the above-mentioned
linear edges are suddenly lowered at an appropriate time interval
by way of cam-motion associated with the circulating belt. Then a
number of parallel tensioned strings 15 are pushed downwards, and
the cut weft web adhering onto the belt is knocked down upon warp
web to be overlaid on the warp web. Meanwhile, the warp web is
moving continuously, and if its speed is so controlled that a
subsequent cut weft web falls just when the warp web has advanced
by the distance corresponding to the width of the fallen cut weft
web, the cut weft webs are laid side by side over the warp web
without forming any gaps or overlappings.
If the fiber density at the edge parts of weft web is made one half
of that at other parts thereof at the time of fiber-arrangement,
the fiber density at overlapped edge parts can be equalized to that
at other parts on the product, when these edge parts of cut weft
webs (i.e., forward end and backward end on the warp web) are
overlapped with each other. By using this method, the gaps between
the forward and backward ends of the cut weft web on the warp web
can be made null.
If the cross-overlaying operation is so slow as 10 m.sup.2 /min. or
less, there is no need of using a higher falling velocity and hence
the vibration of fibrous materials of warp and weft webs, due to
impact of falling cut weft webs is slight and disturbance of
arrangement of fibrous materials does not take place. As the
velocity of cross-overlaying operation becomes greater, that is, at
such a high speed as 30.fwdarw. 50 .fwdarw. 100 m.sup.2 /min., more
rapid falling of the cut weft web becomes necessary; the energy
possessed by falling cut weft webs becomes larger and fibrous
materials in the warp web jump and leap due to the impulse at the
time of cross-overlaying and the cut weft web is apt to show
bouncing, resulting in fiber-disorder in warp and weft webs. The
vibration amplitude of the warp web will be reduced if piano wires
are stretched and fixed under the warp web at a pitch of about 10
cm so as to touch and cross the warp web at right angle. However if
the spaces between the fibrous materials of warp web are large,
some parts of fallen weft web on the travelling warp web are
disturbed by contacting with the piano wires through these large
free spaces between warp fibrous materials.
To overcome this trouble, method hereunder described, showing
another embodiment of the present invention, is very effective.
Namely if the warp web to be cross-overlaid is arranged to adhere
onto a wet belt means travelling at the same speed as that of the
warp web, the impact energy of falling cut weft web is absorbed by
the belt of a heavy weight and moreover since the belt is wetted
with water, the fallen cut weft webs are caught by the surface
tension of water on the belt, eliminating the impulsive vibration
of fibrous materials at the time of cross-overlaying. Thus
cross-overlaying operation of ordered arrangement of fibers becomes
possible even at a high speed operation without disturbing the
ordered state of fibrous materials of both the warp and weft webs.
Particularly notable effectiveness can be attained by laying warp
web on a wet belt in case of cross-overlaying fibrous materials of
large count having a heavy weight, especially, glass fibers or thin
metal wire having a large specific gravity. Namely, laying warp web
upon a wet belt is not a necessary condition for a low speed
operation but it is necessary for a high speed operation.
Further, constructions of circulating belts carrying cut weft web
adhering thereon are described hereunder. As for belt, so long as
it has a sufficient width for laying wefts thereupon, and so long
as it does not allow cut weft web to become partially apart and
dangle therefrom or to fall, their material and construction are
not a problem even when there is a rough part or gaps on the belt
surface to which some parts of a cut weft web do not adhere.
However, when a belt is of a thin cloth or one sheet of an
elastomer, broader width i.e., width broader than 1 m does not give
preferable result because a belt under tension is apt to be
creased, making the adhesion of weft web not uniform or a belt is
apt to meander, making the travelling central line indefinite.
With regard to this point, as shown in FIB. 2a, a multiple belt
consisting of a number of narrow belts arranged over the width of
wefts and each running at the same speed and guided by two sets of
crowned pulleys, each set having the same center of axis is used.
By this method the central line of each belt is maintained and no
crease is formed even when belts of a thin material are used.
When a multiple belt of this kind carries a split web having
fibrous materials of reticulate structure, there would be no
obstacle with a multiple belt consisting of a number of narrow
belts each having a width of 15 to 20 mm, but when weft web having
an ordered arrangement of yarns is used, it may be dangerous to
load yarns on the parts close to the selvedges of each narrow belt
unless (1) a multiple belt consisting of several belts of broader
width, e.g., 150 - 300 mm is used and further unless (2) weft web
is in such a thin arrangement that the pitch of arranged yarns of
the web is greater than 5 mm and about 10 mm and the uniformity of
yarn density as a whole is not lost even when yarns can be arranged
in order, avoiding the selvedges of the individual belts.
However, in case of lattice belt which is referred to hereinafter,
as another embodiment of the present invention, any density of
arrangement can be taken irrespective of kinds of fibrous material
which are reticulate webs or usual yarns or tapes etc. The
advantage of applying such a multiple belt as stated before lies in
the simplicity and cheapness of belt construction. However, strings
as a number or linear edges on the multiple belt contacting
therewith must be fixed to the chains circulating at the same speed
as that of the belt on both the sides of the belt. When strong
tension is applied to the strings and the strings are pushed out
from the belt surface to drop a cut weft web, by lowering merely
two ski-edges each onto the parts of the strings close to both
sides of the multiple belt, the difference of time of fall between
parts of a cut weft web, namely parts close to ski-edges and
central parts can hardly be made equal. However, if the tension of
strings is made too strong, the chains on both the sides are drawn
from each other toward the center of the belt, causing obstacle to
the circulation of the chains. If the tension of strings is
weakened on this account and ski-edges are lowered only on both the
sides of the multiple belt, there is a fear of causing a difference
of time between parts close to ski-edges and the central part of
multiple belt at the time of separation of the cut weft web wetted
with water from the belt surface, and since the cut weft web does
not fall and arrive on the warp web surface at the same time, this
becomes a cause of disturbance of weft web.
Even in such cases, the pushing out and drawing back of strings can
be made uniform throughout the whole surface by allowing a number
of sets of ski-edges to descend through gaps between narrow belts
constituting the multiple belt at an appropriate distance between
each other e.g., a pitch of 150 - 200 mm.
In this regard, in case of lattice belt hereinafter described,
ski-edges for pushing out and drawing back strings cannot be
provided in the middle part of the belt. Hence it is so arranged
that if strings are used for linear edges, string-supporting
devices are provided at several positions of the entire width of
lattice belt in such a way that adhesion of wefts is not thereby
disturbed and the backs of this devices are equally beaten by
ski-edges provided for them.
FIG. 2a shows one example of the above-mentioned multiple belt. The
belt composed of a parallel arrangement of 6 narrow belts 2', each
of which is made to circulate as shown in FIG. 1, belt 2 by crowned
pulleys 21 fixed to a common axis 22 driven by pulley 23 and
pulleys on the other side with a common axis (not shown). Strings
28 are laid on this multiple belt in contact therewith under
tension via springs 26 and 27 which are connected to circulating
chains 24 and 25, respectively. The strings are kept always in
contact with the surface of the multiple belt and circulate at
substantially the same speed with that of the belt surface. At the
point where a cut weft web is wholly overlapped with the warp web
after overlaid, ski edges 29 and 29' provided one in each space
between the side of the belt and the chain, if necessary, together
with a number of ski edges provided between each narrow belts
(though not shown in the drawing) are made to fall suddenly. Then
the strings descend to a distance very close to the warp web,
reverse the course to return rapidly to the belt surface and
circulate together with the belt, whereby the strings are separated
from the belt surface and cause the cut weft web attached onto the
belt surface to drop on the warp web. FIGS. 2b, 2c and 2d show that
cut weft web 30 is pushed off from the belt surface 2 together with
strings 28, by sudden fall of ski edges 29 and 29', and the strings
reverse their course at a distance very close to the warp web, and
return to their original positions, while the cut weft web is
separated from the strings and cross-overlaid upon warp web 31.
As chains 24 and 25 between which the strings are tensioned, are
pulled each other toward the inside by the tension of the strings,
guide rails 32 and 33 are provided in order that strings
circulating in parallel are always kept tensioned under a constant
tension.
Description concerning lattice belts employed as circulating
endless belts will be given by referring to FIGS. 3a - 3e, FIGS. 4a
- 4c and FIGS. 5a - 5d.
If the width of weft web is 1 m, the length of lattice elements
will be 1,100 to 1,200 mm. The width of individual lattice element
41 is generally about 5 - 30 mm, and as shown in FIG. 3a, both its
ends, right and left, are connected to circulating chain 42 and
another chain (not shown), circulating in parallel to chain 42,
respectively, and a circulating lattice belt is formed with a
number of lattice element spaced apart from each other by 5-10 mm.
Near to each end of the lattice element spaced apart by an
appropriate distance, spring arm 43 is fixed to a lattice element
at fixing point 44 which is positioned toward the central part of
the lattice element, the tip of the arm takes usually a form rising
from the surface of the end of lattice element toward the inside of
circulation path, and to each tip of the arm, a string-supporting
device 45 is fixed. In the lower circulating course of the belt,
lower part 46 of string-supporting device as shown in FIG. 3a
usually contacts with the surface of the lattice element and sets
the moving range of spring arms from the surface. String-supporting
point 47 of the string-supporting device is so constructed that
string 48 under tension lies inside the circulating course of belt
surface and in the gaps of lattice elements (at first in the lower
circulating course of the belt as shown in FIG. 3a), and when cut
weft web 50 comes to a position where it is overlapped wholly with
warp web 31 after overlaid, ski-edge 49 rapidly descends on and
knocks the rising end of spring arm 43 of the string-supporting
device in the direction in which the spring arm comes in contact
with the lattice as shown in FIG. 3b. Then, tensioned string 48 is
lowered by lowering of string-supporting point 47, and cut weft web
adhering on the lattice belt is knocked off through the course of
FIG. 3c .BECAUSE. FIG. 3d .BECAUSE. FIG. 3e. The string descends
down to a very close distance to the warp web as shown in FIG. 3d,
and reverses its course to the original position, and in the upper
circulating course, the lattice element takes a form standing
upside down to that of FIG. 3 a, i.e., the spring arm takes form
projecting downwards from the lattice surface.
The characteristic feature of the use of this lattice belt lies in
the points that sufficient tension can be applied to strings,
because ech string is supported by stiff lattice element; when
falling of the central part of string is, nevertheless, liable to
be delayed, the falling of cut weft webs over the whole width can
be made uniform and horizontal through falling of ski edges by
providing string-supporting points with combined spring arm and ski
edge, respectively, at several points in the middle part of lattice
element with such an arrangement that string-supporting device does
not project out above the lattice belt surface and pushing down of
string can be made horizontal over its whole length, and that since
there is no gap in the direction of width of lattice belt, the
method of the present invention is useful not only in case of
reticulate webs but also in case of common yarns wherein the pitch
of arrangement of yarns i.e., density of yarns can be optionally
selected.
As another embodiment of linear edges, in place of the
above-mentioned tensioned strings for knocking off cut weft web
from a weft-carrying lattice belt, a construction of one lattice
element which constitutes the belt where thin plate edges are
pushed down and returned to the original position, is shown in
FIGS. 5a, 5b, 5c and 5d. FIG. 5a is a figure of a cross-section of
one lattice element to which there is attached a linear edge
capable of knocking down and returning to the original position,
and travelling in the upper circulating course of weft-carrying
lattice. FIG. 5b is an elevation showing that one end of lattice
element is fixed to a chain. The other end, though not shown, is
connected to another chain circulating in parallel to the chain.
Cut weft web 71 is transported by square lattice elements 72, onto
the surface of which the web is attached with water. During the
upper circulating course, thin plate 76 which surrounds the lattice
element in U-form is supported by coil spring 75 inserted around
stud bolt 74 set on lattice element 72, the one end of which is
connected to chain 73, thereby to position the tip of linear edge
77 inside the surface of the lattice belt and in the gap between
two adjacent (front or rear) lattice elements. Whenever cut weft
web is brought to a position where the web wholly overlaps with
warp web after overlaid during the lower circulating course of the
belt, ski edge 78 rapidly descends as shown in FIGS. 5c and 5d to
knock down the backside of U-form thin plate whereby linear edges
77 of the tip of thin plate are pushed down from the lattice
surface and cut weft web 71 adhering to the lattice surface is
knocked down onto warp web (not shown).
This method for knocking wefts off by linear edges of the tips of
thin plate does not cause time-lag of falling at the middle part of
wefts which is liable to occur in case where strings are used as
linear edges. Accordingly this linear edge gives even in case of
broad wefts, a good result in the point that a uniform and
simultaneous falling of wefts can be attained and no disturbance of
fibers occurs. When fiber density of weft web is higher, a good
result can be obtained especially by employing this method for
dropping cut weft webs by way of thin plate linear edges, because
overall force of adhesion due to surface tension of water becomes
larger.
When a weft-cutting apparatus which utilizes the engaging two sets
of lattice belt as shown in FIG. 1 is used, the front half part of
a cut weft web can hold the state of arrangement of fibers at the
time of feed by the pull of surface tension of water on the surface
of circulating belt, but the rear end part of cut weft web is
liable to fall freely on the circulating belt immediately after
being cut.
Even when the circulating course of lattice belt 9 is arranged to
come as close to circulating belt 2 as possible, the rear end part
of the cut weft web still have some tendency of disturbance of
fiber arrangement. This drawback can be completely overcome by the
method described hereunder, showing the another weft-feeding method
of the present invention.
In this method, as a weft-carrying circulating belt, a lattice belt
is used as shown in FIG. 4a. The whole peripheral length of this
belt is adjusted to an integer times of a unit section length which
is slightly longer than the length of a cut weft web (four unit
sections in FIG. 4a). Weft web 52 fed continuously through pinch
rollers 51 and 51' is caught on a belt by the surface tension of
water, and rub-slided on the surface of the belt circulating at a
speed slightly faster than the feeding speed of weft web thereby to
maintain the fiber arrangement at the time of feed by drawing force
of the belt due to surface tension of water wetting the belt. When
the length of the weft web reaches a predetermined length of the
cut weft web in each section, it is cut repeatedly into a cut weft
web by a weft cutter 53, the cutting edge of which circulates
around its own axis at substantially the same speed with that of a
belt, and is engaged with the weft web fed at the position at the
rear end of each section. The peripheral length of the circulating
course of the cutting edge is so adjusted as to have a length
substantially equal to that of a cut weft web. Front ends of each
cut weft web 54 and 54', hitted by the cutter, are made to travel
behind the rear part of each preceding section by the distance
corresponding to the difference between the feeding velocity of
weft web and that of circulating belt; the rear ends travel just at
the parts hitted by the cutter on each section. As cut weft webs
adhere to the belt by the surface tension of water, thereafter the
webs are transferred at the velocity of the belt to the part above
warp web positioned in the lower circulating course. On coming to a
position where weft web overlaps wholly with the warp web after
overlaid, ski edge 55 is rapidly lowered by the method shown in
FIGS. 3d- 3e. Namely if cut weft web 54' is knocked off
successively onto the warp web 56 at predetermined intervals by
pushing a number of linear edges downward over the whole surface of
weft web, while holding the arranged state at the time of feed
without causing disturbance thereof, and the warp web is also moved
by being carried on another wet belt means (not shown), moving at
the same or about 1 percent faster velocity than that of feeding of
the warp web, it is possible to obtain laminates of warp and weft
with a highest grade of accuracy of arrangement.
FIG. 4b shows that in case where fibrous materials are glass yarns,
one lattice element 58, on which rubber plate 59 is attached, is
provided at the rear end of each section and revolving knife edge
57 is made to hit the plate. In this case, glass yarns are cut at
the instant when they come to be nipped between the sharp edge of
the knife and the rubber plate.
If fibrous materials are organic fibers, as shown in FIG. 4c there
is provided lattice belt 61 which is circulated at the same speed
with weft-carrying circulating belt 60 through a triangular or
circular course, and one lattice element of lattice belt 61 is
replaced by heated rod 62 capable of sending electric current
thereto, and if necessary, at the time when the rod is engaged with
the circulating belt, this heated rod is forcibly pushed out toward
inside belt 60, whereby wet fibrous materials are at first dried
and immediately thereafter melt-cut. Different from the case of the
method of FIG. 1 where the wefts are cut by a weft cutter at a
position apart from the circulating belt, by the method
above-mentioned, the fiber-arrangement at the time of feed of the
fibrous material for weft web is transferred onto a wet belt and
cut while holding its arrangement, as it is. Thus a high accuracy
of arrangement can be maintained.
The length of each section is slightly longer than the length of
cut weft web, and this percentage of difference corresponds to the
difference between the feeding velocity of weft web and the
velocity of circulating belt. Within the time of the circulation of
the belt by the length corresponding to the part on which no wefts
are attached, pushing down and drawing back motion of ski edge
i.e., linear edge must be completed. Accordingly, the faster the
pushing off and drawing back motion of ski edge is, the smaller the
above-mentioned percentage. Usually it is preferable to make the
length of each section by 10-20 percent longer relative to the
length of cut weft web.
Although cut weft webs adhere onto a belt surface by the surface
tension of water, in the method of the present invention, yarns
having a high Young's modulus such as glass fiber yarn, thin metal
wire yarn, etc., or those yarns of usual organic fibers, spun yarns
or filament yarns, having been heavily twisted are liable to show
natural twisting back in a free state under no tension. Even in
case of hydrophilic fibers whose wet Young's modulus is
considerably reduced by soaking, highly twisted yarns are liable to
show natural twisting back. If heat-set is applied to them, degree
of natural twisting back is reduced especially in case of synthetic
fibers, but highly-twisted yarns are still liable to leave some
degree of natural twisting back property. When such yarns are used
as weft web in the method of the present invention, it is
preferable to put one end of S- and one end of Z-twisted yarns
together side by side with water and handle as one yarn. The
resultant doubled yarns, even when they are not further twisted,
are embraced with each other under the influence of the surface
tension of water, and properties of natural twisting back of S- and
Z-twisted yarns are mutually cancelled, whereby the
fiber-arrangement at the time of feed can be maintained without
disturbance of cut weft webs. This has been confirmed by the actual
experimentation of the present inventor.
Since the warp web is moved under tension between front and back
rollers, there is no natural twisting back and hence both S-twisted
and Z-twisted yarns can be used separately, but in case where
twisted yarns having natural twisting back property are fed as cut
weft webs in the cut state, it is necessary to double two kinds of
twisted yarns (S- and Z-twist) side by side.
Non-woven fabrics obtained by laminating warp and weft according to
the present invention, are presented for actual use in most cases
through the steps of removing water with two pressing rollers after
cross-overlaying of cut weft webs on the warp web, pasting, drying
and fixation of arrangement of fibers of warp and weft. In place of
the above-mentioned processing course, it is, of course, possible
to use raw fibrous materials, for warp or weft web, or both webs
which have been pasted in advance, for subjecting them to
cross-overlaying, removing water, drying and heat pressing.
With regard to pasting agents, a suitable one can be selected, but
if unstretched and quenched foils of polymers belonging to the same
type with the polymer of fibrous materials are used as a pasting
material, it is possible to bond the stretched fibrous materials
without reducing the strength of the stretched fibrous materials,
because the softening point of the former is lower than that of the
latter.
For example, when a high density polyethylene stretched material is
used as fibrous material for the lamination of warp and weft, use
of a low density, preferably quenched polyethylene foil, a foil of
ethylene-vinyl acetate copolymer, or the like between warp and weft
webs gives preferable result due to the function of the latter as a
hot-melt adhesive to the former as well as a function of laminated
film without the danger of blocking between each layer when wound
into a roll. The same effect can be attained between stretched
materials of polypropylene and unstretched quenched polypropylene
foil.
Such adhesive foils can not only be used as an intermediate layer
of warp and weft webs but also if further additional unstretched
quenched foils are fixed onto both the sides, it is possible to
prevent fluffing of fibrous materials and also to impart a
water-proof effect and reinforcing effect to the resulting
products. Moreover this lamination step of foil can be directly
connected to the cross-overlaying step of warp and weft webs.
Especially when an adhesive foil is placed upon warp web and wet
cut weft webs are arranged to fall on and adhere to the foil
according to the weft-feeding method of the present invention, the
shock of falling of cut weft webs is absorbed by the foil, and the
disturbance of falling cut weft web can be prevented due to the
same effect as stated before. In this regard, this method can be
regarded as a modification application of the method as stated
before. This will be explained by referring to FIG. 6.
Adhesive quenched foil 83 is fed onto one group of warp web 82
picked up at a regular interval from the whole warps and fed
through pinch rollers 81 and 81' while maintaining the original
spacings between each other, and cut weft webs 85 are successively
dropped from weft-feeding circulating belt 84 provided above the
warp web loading the foil as adhesives thereon, on the foil. As a
presser of the cut weft web on the first group of warp web, the
rest group of warp web 87, also maintaining the original spacings
in the whole original warp web, is applied on the cut weft webs
cross-overlaid on the first group of the warp web carrying the foil
between pinch rollers 86 and 86'. When the resultant product, after
dehydrated, is moved successively on hot rollers 88 and 88' for
drying and then passed through pressing rollers 89 and 89' to
effect heat adhesion under pressing, a complete adhesion of warp
and weft webs to each other can be attained. Though not shown in
the FIGURE, if 2 sheets of quenched foils are separately laminated
on the top and bottom sides of the laminate of warp and weft during
its course of travel on hot drum 88' so as to give the fibrous
material of warp and weft structure sandwiched between the two
foils, a laminate consisting of warp and weft webs, and three
layers of foils can be obtained in which fluffing of the fibrous
material is completely prevented.
In the method of the present invention, cut weft webs are dropped
on an adhesive foil and warp web 82 is travelled together with the
foil in contact therewith from the underside in most cases, but a
warp web is not necessarily passed through under the weft dropping
part. It is possible to arrange to pass only adhesive foil 83
through under the weft dropping part. Namely, after receiving
dropped cut weft webs, said adhesive foil is passed through pinch
rollers 86 and 86' and put between tow upper side and underside
warp webs there. Underside warp web 82' is guided on roller 86 and
put under said adhesive foil and weft-pressing warp web 87 is
guided on roller 86' to give a sandwich structure consisting of
upper warp web, dropped cut weft webs, adhesive foil and lower warp
web in this order. Thus entirely the same effect can be attained as
in case where warp web 82 is passing through under the
weft-dropping part. Both of the above-mentioned cases are intended
to be included in the scope of claim of the present application.
Thus the process of the present invention is irrespective of
feeding position of warp.
The present invention will be further described referring to
non-limitative examples hereinafter.
Example 1
A foil of high density polyethylene having a width of 1,200 mm and
a thickness of 0.06 mm was stretched to nine times the original
length while it is hot, split with a splitting means, spread to
about three times the original width, subjected to pasting with an
emulsion of vinyl acetate-ethylene copolymer and dried to give a
spread web having a width of 1,200 mm, and the resulting web was
used as a fibrous material for both the warp and weft webs.
By using an apparatus of FIG. 1, warp web guided on a wet belt was
moving horizontally at a speed of 72 m/min. Above this course of
the warp web, weft web cut into a length of 1,220 mm and having a
width of 1,200 mm, as cut weft webs, were charged intermittently on
a multiple belt as shown in FIG. 2a, (which was wetted with water
containing a surfactant, circulating above said warp web in the
direction perpendicular to said warp web, consisting of a number of
belts each having rough surface and a width of 150 mm and a gap of
5 mm between each other and an overall width of 1,390 mm) and
brought to the down-side course of its circulation. At the instant
when the cut weft web came to a position overlapped wholly with the
warp web after overlaid, ski edges were pushed to lower a number of
strings arranged in parallel with a pitch of 30 mm, down to the
lowest level corresponding to 10 mm above the warp web and returned
to the original position thereby to give cross-overlaying 60 times
per minute. Thereafter the resultant product was separated from the
warp web-guiding circulating belt and dried after being squeezed to
remove water through pinch rollers. Then while it is running in
free space, short fibers of cotton linter having been scoured,
dried and disentangled, were scattered and attached on it so as to
give a loading amount of 3 - 4 g/m.sup.2, thereby to strengthen the
crossing of the fibers of warp and weft webs, and the resulting
product was subjected to adhesion by pressing on heating. Thus,
strong non-woven fabrics which have an extremely good adhesion of
the fibers of warp and weft to each other at the crossing thereof
and a total fiber density of 17 - 19 g/m.sup.2, and do not show
blocking after wound up, were obtained at a rate of 103 m.sup.2
/min.
Example 2
For warps, two hundred and one ends of glass fiber yarns (long
fibers) of 100 tex. were divided into two groups having 101 and 100
ends, respectively. The first warp web was prepared by arranging
101 ends of yarns in 1 m width with a pitch of 10 mm, mounted on a
circulating wet belt for warp web and moved at a rate of 50 m/min.
S-twisted glass fiber yarns of 50 tex. and Z-twisted glass fiber
yarns of 50 tex. were doubled to one yarn of 100 tex. so as to
cancel their tendency of natural twisting back property. 200 ends
of the resultant yarn were passed through a comb and arranged to
give 200 ends of wefts in 1 m width which were fed on a wet
circulating belt for weft web through pinch rollers 51 and 51' as
shown in FIGS. 4a and 4b, at a rate of 50 m/min. The weft-carrying
belt was installed above the warp-carrying belt in the direction
perpendicular thereto.
The belt for weft web was an endless circulating lattice belt of
1,200 mm wide, having a peripheral length of 6,000 mm and divided
into 5 sections, each having 48 lattice elements made of stainless
steel pipes of 20 mm square, arranged in a 25 mm pitch with gaps of
5 mm between each other. The circulation velocity thereof was 60
m/min. Since the weft web fed on this belt was caught the surface
tension of water wetting the surface of the belt and rub-slided on
the surface of the belt moving faster than the feed velocity of the
fibrous material for weft web, under cancelling of the twisting
back property of S-and Z-yarns, the pitch between arranged yarns on
the belt was as it was at the time of feed, without
disturbance.
When the fed length of weft web became 1 m in each section, the web
was cut with a knife cutter into cut weft webs successively as
shown in FIB. 4b. Thereafter, cut weft web moved at the same speed
as that of the belt while being attached onto the surface of the
belt. Each section had, in the foreward part thereof, a part of 200
mm distance where no wefts were loaded. When a cut weft web came to
a position wholly overlapped with the warp web after overlaid in
the down side course of travel, ski edges were suddenly lowered at
a rate of 50 times per minute to give cross-over-laying of warp and
weft webs without gap. The resulting product was separated from the
wet belt on which the first warp web had been loaded, and the
second set of warp web warped at a pitch of 10 mm was supplied onto
the product during the pass of pinch rollers to be laminated in
such a way that each yarn of the second warp web came to a position
between yarns of the first running side by side.
After squeezing out water by pinch rollers, the resulting product
was pasted with a pasting agent of polyvinylalcohol type and
squeezed. Thereafter onto the pasted product, free short single
fibers prepared by fully opening short fiber waste formed in
spinning mills were scattered and loaded at a rate of 5 g/m.sup.2,
and the whole was dried with hot air and then on hot drums, whereby
non-woven fabrics of warp and weft containing glass fibers in an
amount of 40 g/m.sup.2 were produced at a speed of 50 m.sup.2 /min.
without any blocking of wound-up layers due to softening of
adhesive.
In case of non-woven fabrics of laminate of warp and weft
consisting of glass fibers to be used as a reinforcing material for
FRP (fiber-reinforced plastics), if adhering pasting agents or
organic short fibers are not preferable, it is possible to scatter
and load glass short fibers of 3- 5 mm length, as short fiber, and
then to burn out the organic pasting agent.
We noticed in this case that the arrangement of glass fibers of
warp and weft structure was maintained only with glass short fibers
entangled therewith.
Example 3
320 ends of stretched tapes of polypropylene, each having a width
of 6 mm and a denier of 1,000 were used as a fibrous material. The
tapes were arranged in parallel and flat, and split into split
yarns during their course of travel. The resulting yarns were
passed through a comb and thereby the width was narrowed so as to
be able to arrange 320 ends in 1 width. They were guided as a weft
web onto a wet endless lattice belt consisting of five sections in
the total periphery, each having 1.2 m length, during its upper
circulating course as shown in FIG. 4a. Whenever the fed length of
the arranged yarns reached 1 m in each section, the yarns were cut
to form a cut weft web by a melt cutter and the cut weft webs were
one by one brought to the lower circulating course while being
attached onto the belt.
Another 320 ends of polypropylene split yarns for a warp web,
obtained in the same manner as above, were divided into 2 sets,
each consisting of 160 ends and warped in a width of 1 meter.
The first set of warp web was fed in the manner as shown in FIG. 6,
passing between pinch rollers 81 and 81', together with a quenched
foil of polypropylene, having a thickness of 0.02 mm and a width
sufficient to cover the width of the warp web, thereon.
At the time whenever one cut weft web came to a position wholly
overlapped with the first set of warp web after overlaid, linear
edges of thin plate shown in FIGS. 5a-5d were pushed down to drop
the cut weft web on the foil. The second set of warps with 160 ends
in 1 meter was laid upon dropped cut weft webs during the pass
between pinch rollers 86 and 86.degree.. After cut weft webs were
overlaid on the warp web in such a manner that the weft webs were
sandwiched by the warp web of the first and second sets arranged so
that each yarn of the second set might come to a position between
yarns of the first set running side by side, the resulting overlaid
product was dried by squeezing out water and heating on a hot drum
and pressed on heating, whereby a non-woven fabric of laminate
consisting of warp, weft webs and a foil as adhesive therebetween
was obtained at a rate of 50 m/min.
Additionally, two quenched polypropylene foils each having a
thickness of 0.03 mm were supplied onto a heating drum so as to
sandwich the above-mentioned laminate of warp and weft on both the
sides thereof and pressed on heating. The resulting laminate gave a
substitute of water-proof heavy duty cloth having a fiber density
of 70- 75 g/m.sup.2 in both of the warp and weft directions and a
strength of 65- 75 kg/50 mm width in both the warp and weft
directions and containing 75- 80 g/m.sup.2 of the adhesive
foil.
In case where stretched tapes are used as a fibrous material as in
this embodiment, if tapes 6.0- 6.5 mm wide are to be laminated
flatly side by side in both the warp and weft directions in flat
form, an arrangement of more than four ends per inch is
impossible.
Accordingly, in such cases as there are parts where more than two
tapes may be piled up, unless the width of tapes is narrowed by
splitting as in the present embodiment or by creasing followed by
squeezing, each single fibrous material in both the warp and weft
directions is not exposed on adhesion surface of warp web and weft
web and there may occur parts of bad adhesion of both webs.
However, if stretched tapes having an adhesive applied thereon and
dried in advance are used for each of said tapes, tapes in both the
warp and weft directions can be easily bonded firmly as they are in
the state of stretched tapes even when they are not squeezed into
narrower width.
In general, if fibrous materials are laminated in layers of warp
and weft according to the process of the present invention, and
then pasted and bonded by scattering and loading short fibers on
the resulting product, not only peeling off of warp and weft web
from each other can be completely prevented, but also blocking
which often occurs during the time of winding-up of pasted
non-woven fabrics due to softened pasting agent can be
prevented.
Further if carded webs of short fibers which are slightly longer
than the above-mentioned are additionally laminated, free open
spaces of crossed warp and weft fibrous materials are subdivided or
filled with said short fibers, and reinforcement and covering
effect are notably increased.
Since short fibers such as pulp fibers of 1-3 mm length, those
which have sufficient length to be treated with a carding machine,
such as cotton or artificial staple fibers, short fibers for reuse,
recovered from waste fibrous materials, etc. are all inexpensive
raw materials for above-mentioned usage, they can perform very
important roles in the reinforcement of non-woven fabrics of warp
and weft and in expanding the utility and adaptability thereof.
When the density of fiber arrangement of webs in the warp and weft
directions is small, the air existing between the warp web and cut
weft web to be dropped during the falling of cut weft web upon warp
web tends to leak through fibrous materials towards upward and
downward directions and hence cut weft web drops upon the warp web
without disturbance. However, when the density of fiber arrangement
of both warp and weft webs is high, the air is difficult in leaking
and the escape of air layer between warp and weft webs becomes
difficult, resulting in the disturbance of cut weft web at the time
of falling particularly in high speed operation. For solving the
problem of this drawback, it has been proposed in the prior patent
application of the present inventor, to provide a negative pressure
chamber beneath warp web to exert a downward suction force through
fibrous material of warp web thereby to ease the fall of cut weft
web and prevent the disturbance of fiber arrangement thereof.
Particularly when utilization of negative pressure is so arranged
as to draw down the front end of falling cut weft web obliquely
toward forward and the back end thereof obliquely toward backward,
notable effect for prevention of wrinkling and for obtaining
uniformity of fiber arrangement can be attained. In case of high
density of fiber arrangement, even when a wet belt for warp web is
not used, only wetting of warp web can afford the same effect with
that of using of the wet belt and also the suction force can be
effectively exerted from underside the warp web at the time of
falling of the cut weft web.
* * * * *