U.S. patent number 3,748,693 [Application Number 05/128,460] was granted by the patent office on 1973-07-31 for apparatus for making nonwoven fibrous webs.
This patent grant is currently assigned to Georgia-Pacific Corporation. Invention is credited to Paul W. Jespersen.
United States Patent |
3,748,693 |
Jespersen |
July 31, 1973 |
APPARATUS FOR MAKING NONWOVEN FIBROUS WEBS
Abstract
An apparatus wherein a plurality of fibers are transported to
and deposited on a foraminous conveyor by a flow of gas to form a
nonwoven fibrous web. The passage of the flow through the conveyor
is regulated by two independently operable, superposed means for
selectively restricting such passage to control the deposition of
the fibers on the conveyor and thereby control the thickness of the
web.
Inventors: |
Jespersen; Paul W. (Stamford,
CT) |
Assignee: |
Georgia-Pacific Corporation
(Portland, OR)
|
Family
ID: |
22435484 |
Appl.
No.: |
05/128,460 |
Filed: |
March 26, 1971 |
Current U.S.
Class: |
425/82.1;
19/306 |
Current CPC
Class: |
D04H
1/732 (20130101); D21H 11/00 (20130101); D01G
25/00 (20130101) |
Current International
Class: |
D01G
25/00 (20060101); D01g 025/00 () |
Field of
Search: |
;19/88,89,205,155,156,156.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Newton; Dorsey
Claims
I claim:
1. An apparatus for making non-woven fibrous webs having transverse
variations in thickness comprising:
a chamber;
a foraminous conveyor having a portion extending through said
chamber;
means for generating a flow of gas through said chamber, said
chamber being operable to direct said flow through said conveyor
portion;
means for feeding a plurality of fibers into said flow so that the
fibers are transported to and deposited on said conveyor portion by
said flow to thereby form a non-woven web;
first means for restricting the passage of said gas flow through
said conveyor portion comprising a plate positioned adjacent said
conveyor portion on the downflow side thereof and having a
generally diagonally extending opening thereacross for the passage
of the gas flow therethrough, said diagonal opening is narrower at
the ends thereof than the central portion thereof, thereby
permitting a greater volume of gas to pass through the central
portion of the opening than the ends thereof and
second means for restricting the passage of said gas flow through
said conveyor portion comprising a plurality of movably mounted
vanes superposed with respect to said plate.
2. An apparatus as recited in claim 1, wherein each of said vanes
is mounted for pivotal movement about an axis extending
transversely of said conveyor portion, whereby the fiber deposition
pattern may be further regulated by differentially adjusting the
vanes.
3. An apparatus as recited in claim 1, wherein said conveyor
comprises a wire mesh belt.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods and apparatus for making nonwoven
webs, and particularly to a method and apparatus for making a
nonwoven fibrous web wherein the thickness of the web is accurately
controlled, including desired transverse variations in
thickness.
2. Description of the Prior Art
Various methods and apparatus are known for making nonwoven fibrous
webs, including webs adapted to be used as absorbent pads.
Exemplary of the prior art methods and apparatus of this general
type are those disclosed in Bertolet U.S. Pat. No. 2,581,069,
Anderberg et al., U.S. Pat. No. 3,032,836, Labino U.S. Pat. No.
3,114,939 and Nordstrand U.S. Pat. No. 3,423,796. The apparatus
disclosed in these patents include means for pneumatically
depositing a plurality of fibers on a foraminous conveyor and means
for controlling the deposition of the fibers, such as a plurality
of pivotally mounted vanes positioned adjacent the conveyor. While
such vanes are useful for controlling the thickness of the webs,
they do not provide sufficient control over the pneumatic
deposition means to permit the formation of webs having desired
transverse variations in thickness.
For some uses of nonwoven fibrous webs, it is desirable that the
webs have transverse variations in thickness. For example, a web
having a central portion of greater thickness than the marginal
portions, is ideally suited for use as an absorbent pad in a
disposable diaper.
SUMMARY OF THE INVENTION
The method and apparatus of the present invention provide an
effective and efficient solution to the above-mentioned deficiency
of the prior art methods and apparatus, and are ideally suited for
making nonwoven fibrous webs adapted for use as absorbent pads.
Basically described, the apparatus of the invention comprises; a
chamber; a foraminous conveyor having a portion extending through
the chamber; means for generating a flow of gas through the
chamber, said chamber being operable to direct the flow through
said conveyor portion; means for feeding a plurality of fibers into
the flow so that the fibers are transported to and deposited on
said conveyor portion by the flow to thereby form a web; and first
and second independently operable, superposed means for adjustably
restricting the passage of the flow through said conveyor portion
to control the deposition of the fibers on said portion and thereby
control the thickness of the web.
Generally described, the method of the invention comprises;
directing a flow of gas through a foraminous conveyor; feeding a
plurality of fibers into the flow so that the fibers are
transported to and deposited on the conveyor by the flow to thereby
form a web; and regulating the passage of the flow through the
conveyor to control the deposition of the fibers thereon and
thereby control the thickness of the web, said regulating including
adjusting two independently operable, superposed means for
restricting the passage of the flow through the conveyor.
One of the independently operable passage restricting means
preferably comprises a plate positioned adjacent the conveyor and
having an opening therein. The other independently operable passage
restricting means preferably comprises a plurality of movably
mounted vanes also positioned adjacent the conveyor. The size and
shape of the opening in the plate and the attitude of the vanes may
be adjusted independently to produce a web having accurately
controlled thickness variations transversely of the web.
The conveyor preferably includes a wire mesh belt, and the gas flow
generating means preferably comprises a conventional blower. The
blower preferably is connected to a suction box and the conveyor
and passage restricting means preferably extend across the upper
end of such box.
The fiber feeding means preferably comprises a pin mill adapted to
abrade a sheet of wood pulp. The pin mill preferably is mounted
above the suction box so that the pin mill and suction box form a
chamber through which an air flow generated by the blower passes.
The chamber thus directs the flow through the conveyor and passage
restricting means so that the wood fibers are transported to and
deposited on the conveyor by the flow.
With the foregoing in mind, it is an object of the present
invention to provide an improved method and apparatus for making
nonwoven fibrous webs.
It is also an object of the invention to provide a method and
apparatus for making nonwoven fibrous webs having controlled
transverse variations in the thickness thereof.
It is an additional object of the invention to provide a method and
apparatus for making nonwoven fibrous webs in which a plurality of
fibers are deposited on a foraminous conveyor by a flow of gas and
in which the thickness of the web formed by such deposition is
controlled by two independently operable, superposed means for
restricting the passage of the flow through the conveyor.
These and other objects of the invention will be apparent upon a
consideration of the following detailed description of the
preferred embodiments thereof given in connection with the
following drawings, wherein like reference numerals identify like
elements throughout.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an elevational view, partially in section, of the
apparatus of the invention;
FIG. 2 is a sectional view taken on line 2--2 of FIG. 1; and
FIG. 3 is a sectional view taken on line 3--3 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the apparatus of the invention is shown
in the drawing, as designated by reference numeral 10. Apparatus 10
includes a pin mill 12 comprising a housing 14, and disposed within
the housing, a pair of rotatably mounted feed rolls 16, a rotatably
mounted attrition roller 18 and a nose bar 20 positioned between
the feed rolls and attrition roller. Feed rolls 16 and attrition
roller 18 are rotatably driven by conventional drive mechanisms
(not shown). A feed slot 22 is formed in the side of housing 14
adjacent feed rolls 16. Also, a pair of openings 24 are formed in
the side of the housing to permit air to enter the housing for a
purpose described below, and a pair of windows 26 are mounted on
opposite sides of the lower portion of the housing through which
the operation of mill 12 may be observed.
A conveyor 28 is mounted below mill 12 and includes a foraminous
wire mesh belt 30 and a plurality of rotatably mounted guide rolls
32 about which belt 30 is trained. One of rolls 32 is rotatably
driven by a conventional drive mechanism (not shown). The upper run
of belt 30 extends across the open lower end of housing 14.
A suction box 34 also is mounted below mill 12. The upper run of
belt 30 extends across the open upper end of suction box 34, and
the lower end of housing 14 is connected to the upper end of box 34
along the sides of the upper run of belt 30 so that the housing and
suction box form a chamber 35 through which the upper run of the
belt extends. If desired, a pair of resilient surfaced rollers 36
may be rotatably mounted on the lower end of housing 14 directly
above and contacting belt 30 adjacent the entrance and egress of
the belt to and from chamber 35. Rollers 36 minimize the flow of
air into chamber 35 through the openings provided therein at the
juncture of the lower end of housing 14 and upper end of box 34
through which belt 30 extends, for reasons which will become
apparent below.
A pair of conduits 38 are connected between the ends of suction box
34 and a conventional blower 40. Blower 40 generates a flow of air
through chamber 35 with air being drawn into housing 14 through
openings 24 and out of suction box 34 through conduits 38. As will
be apparent, the flow moves downwardly from housing 14 and into
suction box 34 through the upper run of belt 30.
A rolled sheet 42 of wood pulp is rotatably supported adjacent
housing 14. Sheet 42 is fed into the housing through feed opening
22 and between feed rolls 16. Rolls 16 feed the sheet across nose
bar 20 and against the surface of attrition roller 18. The
attrition roller abrades sheet 42 into individual wood fibers 44
and urges the fibers downwardly into the flow of air through
housing 14. Fibers 44 are transported to the upper run of belt 30
and deposited thereon by the air flow, incident to movement of the
flow from housing 14 into suction box 34. The fibers thus form a
nonwoven fibrous web 46 on the upper run of the belt. Web 46 is
thereafter transported out of chamber 35 by belt 30 and deposited
on the belt of a transfer conveyor 48.
Apparatus 10 includes means for controlling the thickness of web
46, and in particular for varying the thickness of the web
transversely thereof. Such means comprise two independently
operable, superposed means for adjustably restricting the passage
of the air flow through the upper run of belt 30. One of the
passage restricting means comprises a plate 50 positioned beneath
the upper run of the belt and having an opening 52 therein. The
passage of the air flow though the portion of belt 30 adjacent
plate 50 is thus restricted to the area of opening 52.
The other passage restricting means comprises a plurality of
movably mounted vanes 54 positioned below plate 50. Vanes 54
preferably are pivotally mounted in the upper end of suction box 34
and extend transversely of belt 30. Vanes 54 may be individually
pivoted to differentially restrict the passage of the air flow
through the adjacent portion of belt 30.
Plate 50 and vanes 54 permit the thickness of web 46 to be
accurately controlled, including variations in the thickness of the
web transversely thereof. As mentioned above, this latter feature
is particularly advantageous for making webs which are adapted to
be used as absorbent pads.
Opening 52 may be of any desired shape and size to provide the
desired fiber deposition pattern. The deposition pattern may be
further controlled by individually adjusting the attitude of vanes
54.
An example of the combined effects of plate 50 and vanes 54 is
illustrated by the embodiment of the apparatus shown in the
drawing. In this embodiment, opening 52 extends generally
diagonally across plate 50 and is narrower at the ends thereof than
at the central portion thereof. Thus, a greater volume of air is
permitted to pass through the central portion of the opening than
at the ends thereof. Consequently, a greater number of fibers 44
are deposited on the central portion of belt 30 as the belt passes
over plate 50 than on the marginal portions of the belt, and the
resulting web 46 will have a central portion of greater thickness
than the marginal portions. This particular web configuration is
well suited for use as an absorbent pad in a disposable diaper.
The deposition of fibers 44 may be further controlled by
individually adjusting vanes 54. In the embodiment of the apparatus
shown in the drawing, the vanes are all adjusted to the same
attitude so that the vanes do not differentially restrict the
passage of the air flow through belt 30. However, if a further
reduction in the thickness of the marginal portions of web 46 is
desired, the vanes which underlie the narrower portions of opening
52 may be partially closed to thereby further restrict the passage
of the flow through the adjacent portions of belt 30. Thus, a still
greater number of fibers 44 will be deposited on the central
portion of the belt and a lesser number will be deposited on the
marginal portions of the belt. Other variations in the size and
shape of opening 52 and the attitude of vanes 54 may be employed to
provide other transverse variations in the thickness of web 46.
The method of the invention will be apparent from the foregoing
description of the apparatus thereof.
The method and apparatus of the invention are effective and
economical for making nonwoven fibrous webs, and particularly webs
having transverse thickness variations, and thus are ideally suited
for making webs adapted to be used as absorbent pads.
While the foregoing constitutes a detailed description of the
preferred embodiments of the method and apparatus of the invention
it is recognized that various modifications thereof will occur to
those skilled in the art. For example, while the preferred
embodiment of the apparatus includes a pin mill specifically
adapted for feeding a plurality of wood fibers onto belt 30, other
fiber feeding means as appropriate for the particular type of
fibers desired may be employed. Thus, the invention is to be
limited solely by the scope of the appended claims.
* * * * *