U.S. patent number 3,846,871 [Application Number 05/237,963] was granted by the patent office on 1974-11-12 for apparatus for forming fibrous pads.
This patent grant is currently assigned to Scott Paper Company. Invention is credited to Charles G. Kolbach.
United States Patent |
3,846,871 |
Kolbach |
November 12, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
APPARATUS FOR FORMING FIBROUS PADS
Abstract
Apparatus for forming fibrous pads include a pad-formation
assembly having spaced, three-dimensional pad-receiving
compartments; adjacent compartments being separated by
air-impermeable regions. Each compartment has the shape of a
fibrous pad to be formed therein and is defined by a lower
air-permeable surface and air-impermeable sidewalls extending
outwardly from the air-permeable surface. Sidewall sections are
movable relative to the lower surface to aid in releasing formed
pads from each of the compartments. In one preferred embodiment,
sidewall sections are also moveable relative to each other to
enhance the releasibility of the formed pads from the compartments.
Drive means moves the pad-formation assembly to direct a
substantially linear forming run of the assembly through a pad
forming region. The pad forming region includes a fiberizing means
for forming an air suspension of fibers, and a vacuum means
disposed behind the forming run for creating a partial vacuum to
direct the air suspension of fibers into the compartments whereat
the air is pulled through the lower surface, and the fibers are
deposited within the confines of the pad-receiving compartments.
Air-impervious masking means can be disposed between the vacuum
means and the forming run for selectively masking different
predetermined sections of the compartments to the passage of air
generated by the vacuum means to thereby form discrete fibrous
pads, each of which has a predetermined region with a weight of
fibers per unit area therein which is different than the weight of
fibers per unit area in another predetermined region of the pad. A
method for forming discrete fibrous pads, each of which has a
predetermined region with a weight of fibers per unit area therein
which is different than the weight of fibers per unit area in
another predetermined region of the pad. Fibers are entrained in
air to form an air suspension of fibers, and the air suspension of
fibers is directed selectively into the different predetermined
sections of the pad-receiving compartments to form the fibrous
pads. Preferably, the air suspension of fibers is directed into the
different predetermined sections of the pad-receiving compartments
at different, non-overlapping times to substantially completely
form a predetermined region of each pad having a given weight of
fibers per unit area therein substantially independently of the
formation of another and different predetermined region having a
different weight of fibers per unit area therein.
Inventors: |
Kolbach; Charles G. (Media,
PA) |
Assignee: |
Scott Paper Company (Delaware
County, PA)
|
Family
ID: |
26748345 |
Appl.
No.: |
05/237,963 |
Filed: |
March 24, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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67862 |
Aug 28, 1970 |
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Current U.S.
Class: |
19/148; 19/301;
19/306 |
Current CPC
Class: |
A61F
13/15634 (20130101); A61F 13/532 (20130101); A61F
13/15626 (20130101); A61F 2013/5326 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); D01g 025/00 () |
Field of
Search: |
;19/155,156.3,156.4,144,148,145 ;156/62.2 ;65/4 ;18/43,58 ;425/80
;162/217,353,367,382,410 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Newton; Dorsey
Attorney, Agent or Firm: Faigus; Martin L. Foley; William
J.
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part of abandoned U.S. Pat.
application Ser. No. 67,862, filed Aug. 28, 1970, and assigned to
Scott Paper Company.
Claims
What is claimed is:
1. An apparatus for forming discrete fibrous pads, said apparatus
comprising:
A. a pad-formation assembly having spaced, three-dimensional
pad-receiving compartments, said compartments being separated from
each other by air-impermeable regions; each pad-receiving
compartment having a configuration of a fibrous pad to be formed
therein and being defined by a bottom air-permeable surface and
sidewall means extending outwardly from one side of said bottom
surface; sections of said sidewall means being movable relative to
each other and to said bottom surface to aid in releasing a formed
pad from each of said pad-receiving compartments; said
pad-formation assembly including;
1. a flexible substrate adhered to a conveyor means;
2. said conveyor means providing said bottom air-impermeable
surfaces, and said flexible substrate including surfaces disposed
contiguous to the periphery of said air-permeable surfaces for
providing said sidewall means;
B. drive means for moving said pad-formation assembly along a
predetermined path including a pad-formation run directed through a
pad-forming region;
C. means for forming a gaseous suspension of fibers in said
pad-forming region; and
D. vacuum means for pulling the gas of said suspension through the
bottom air-permeable surfaces of said pad-receiving compartments
from said one side of said air-permeable surfaces to said in
depositing the fibers of said suspension on said bottom
air-permeable surfaces as said air-permeable surfaces pass through
said pad-forming region.
2. The apparatus according to claim 1, wherein said flexible
substrate has a thickness in the range of from about 1/4 inch to
about 1 inch.
3. The apparatus according to claim 1, wherein said flexible
substrate defines said air-impermeable regions to separate adjacent
pad-receiving compartments.
4. The apparatus according to claim 1, including profiling masking
means disposed between the pad-formation assembly and said vacuum
means in the pad-formation run for cooperating with said vacuum
means in creating a different effective volumetric air-flow through
different predetermined regions of the pad-receiving compartments
for forming discrete pads with a weight of fibers per unit area in
one of said different predetermined regions which is different than
the weight of fibers per unit area in another of said different
predetermined regions.
5. The apparatus according to claim 4, wherein said one of said
different predetermined regions and said another of said different
predetermined regions are non-overlapping.
6. The apparatus according to claim 1, wherein said pad-formation
run is substantially linear.
7. The apparatus according to claim 6, wherein said drive means
moves said pad-formation assembly through a substantially linear
pad-transfer run opposed to the substantially linear pad-formation
run of the pad-formation assembly, including a transfer conveyor
means, and drive means for moving said transfer conveyor means
through a substantially linear pad-receiving run closely adjacent
the pad-transfer run of said pad-formation assembly, and means for
transferring allegience of the fibrous pads from the pad-transfer
run of the pad-formation assembly to the pad-receiving run of the
transfer conveyor means.
8. The apparatus according to claim 7, wherein said pad-transfer
run and said pad-receiving run are spaced to prevent substantial
movement of said formed fibrous pads during the transfer of
allegience of said formed fibrous pads from the pad-formation
assembly to the transfer conveyor means.
9. The apparatus according to claim 7, wherein said transfer
conveyor means is air-pervious, and said means for transferring
allegience of said pads from the pad-transfer run to the
pad-receiving run includes a vacuum means disposed adjacent the
pad-receiving run for creating a partial vacuum therethrough.
10. The apparatus according to claim 9, including means for
directing an air-permeable fibrous web adjacent to an exposed
surface of said flexible substrate to define a closure for said
pad-receiving compartments, and means for directing said fibrous
web between the pad-transfer run of the pad-formation assembly and
the pad-receiving run of said transfer conveyor means, said vacuum
means being operable to pull said vacuum through said air-permeable
fibrous web and the pad-receiving run of said transfer conveyor
means to thereby transfer allegience of the formed fibrous pads
from the pad-formation assembly to said air-permeable fibrous
web.
11. An apparatus for forming discrete fibrous pads, said apparatus
comprising:
A. a conveyor means having spaced air-permeable regions which have
configurations of fibrous pads to be formed therein, said conveyor
means having other regions which are impermeable to air;
B. a movable masking frame assembly disposed adjacent to, and on
one side of said conveyor means and including frame members
defining spaced openings having configurations of pads to be
formed; said openings being spaced substantially the same distance
as the spacing between the air-permeable regions of said conveyor
means;
C. drive means for moving said conveyor means and said movable
masking frame assembly through a pad-forming region in synchronism
such that openings defined by said frame members are in overlying
relationship with air-permeable regions of said conveyor means;
D. means for forming a gaseous suspension of fibers in said
pad-forming region;
E. vacuum means for pulling the gas of said suspension through the
spaced air-permeable regions and accumulating the fibers of said
suspension in said spaced air-permeable regions to thereby form
fibrous pads of the desired configuration.
12. The apparatus according to claim 11, wherein said masking frame
assembly and said conveyor means both have substantially linear
runs disposed in sealing engagement with each other within said pad
forming region.
13. The apparatus according to claim 11, including sealing means on
said frame members for contacting said conveyor means in sealing
engagement as said conveyor means and masking frame assembly are
moved in overlying relationship through said pad forming
region.
14. The apparatus according to claim 12, wherein said drive means
moves said conveyor means and masking frame assembly in sealing
engagement with each other along a substantially linear run through
the pad forming region and separtes said masking frame assembly and
conveyor means at the end of said region, said vacuum means being
disposed for pulling air through the air-permeable surfaces of said
conveyor means during the separation of said conveyor means from
said masking frame assembly to retain formed pads on said conveyor
means.
15. The apparatus according to claim 11, wherein said masking frame
assembly includes support members, said frame members being
removably secured to said support members whereby frame members
having surfaces of various configurations can be connected to said
support members for varying the configuration of the openings
defined by the surfaces of said frame members, said support members
being interconnected in spaced relationship by support links.
16. The apparatus according to claim 15, wherein adjacent links
have aligned openings therein, and pins extending from a chain
extend through said aligned openings to connect said links
together.
17. The apparatus according to claim 16, wherein at least some of
said openings are elongate to permit relative linear movement
between links.
18. The apparatus according to claim 11, wherein frame members
defining adjacent spaced openings are interconnected by support
links, and means for connecting said support links together for
permitting relative linear and rotational movement between
links.
19. The apparatus according to claim 18, wherein adjacent links
have aligned openings therein, and pins extending from a chain
extend through said aligned openings to connect said links together
and to connect said links to said chain, said drive means driving
said chain to thereby control the movement of said links and said
masking frame assembly.
20. The apparatus according to claim 19, wherein at least some of
said openings in said links are elongate to permit relative linear
movement between links.
21. The apparatus according to claim 20, including at least a pair
of rotatably mounted, spaced sprocket wheels, said chain being
endlessly trained about said sprocket wheels, said drive means
rotating at least one of said sprocket wheels.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to apparatus and methods for forming fibrous
pads, and more specifically to apparatus and methods for forming
discrete pads of a desired shape and profile.
Reference to "shape" throughout this application, including the
claims, in describing the structure of a fibrous pad, refers to the
configuration of the pad in plan view.
Reference to "profile," as used throughout this application,
including the claims, in describing the structure of a fibrous pad,
refers to a varying weight distribution of fibers in the pad such
that the pad has a predetermined region with a weight of fibers per
unit area therein which is different than the weight of fibers per
unit area in at least one other predetermined region of the
pad.
2. Description of the Prior Art
Many sanitary products, such as disposable diapers, sanitary
napkins and the like, utilize an absorbent fibrous pad as one
component thereof. This pad, in many instances, must have a
specific shape which can be reproduced in an economical mass
production operation. One prior art apparatus for producing
discrete fibrous pads is disclosed in U.S. Pat. No. 2,940,133,
issued to Heritage. This patent discloses an apparatus employing a
drum-type condenser upon which fibrous pads are formed. The
condenser is masked to define air-permeable surfaces defining the
shape of fibrous pads to be formed. The air-permeable surfaces are
separated by air-impermeable surfaces which are disposed
substantially in the same plane as the air-permeable surfaces. It
is difficult to form fibrous pads having the specific shape of the
air-permeable surfaces in a repeatable fashion by utilizing an
apparatus such as is disclosed in the Heritage patent. One major
reason for this difficulty is that air-suspended fibers which are
initially directed toward the masked, air-impermeable surfaces of
the condenser are deflected to the perimeter of the unmasked,
air-permeable surfaces by a vacuum applied from within said
condenser. The air suspension of fibers impinges on the boundaries
of the air-permeable surfaces at various angles to cause random
deposits of fibers adjacent the perimeters of the unmasked surfaces
of the condenser. These random deposits cause distortions in the
shape of the formed fibrous pads.
Other prior-art apparatus for forming fibrous pads have employed
drum-type condensers with three-dimensional pad-receiving
compartments extending inwardly from a peripheral surface thereof.
Such prior-art apparatus are exemplified in U.S. Pat. No.
3,518,726, issued to Banks; and in U.S. Pat. No. 1,950,765, issued
to Winter. These drum-type condensers, as well as the drum-type
condenser disclosed in the Heritage patent, have several
deficiencies. In order to obtain controlled pad formation, an air
suspension of fibers should be directed either tangent or
perpendicular to the forming run of a pad-formation assembly. When
the air suspension of fibers is directed tangent to the forming run
a cloud of air-suspended fibers is established above the forming
run. This cloud can be directed in a controlled manner into the
pad-receiving compartments by a partial vacuum created through a
vacuum source disposed below said forming run. When the air
suspension of fibers is directed perpendicular to the forming run
the fibers also are easily diverted into the pad-receiving
compartments in a controlled manner to establish controlled
pad-formation. When the air suspension of fibers is directed toward
the pad-formation assembly at orientations other than tangent or
perpendicular to the forming run, uncontrolled, non-uniform fiber
distribution occurs at either the trailing or leading edge of each
compartment, depending upon the specific orientation of the stream
of air suspended fibers relative to the compartments.
Theoretically, no complete pad-receiving compartment or discrete
pad-receiving area of a drum-type condenser is oriented either
perpendicular or tangent to a stream of air suspended fibers at any
given time during the pad forming operation. Practically, only
about 90.degree. of the periphery of a drum-type condenser at any
given time during the pad forming operation is so oriented with
respect to a stream of air suspended fibers that adequate control
of pad formation can be achieved.
Apparatus employing drum-type condensers are speed limited by the
fact that a major portion of the condenser surface, at any given
time, is not properly oriented to be utilized in forming shaped
pads in a controllable manner. To increase the pad output in
apparatus employing a drum-type condenser, the condenser must be
operated at extremely high speeds, and/or the drum-type condenser
must have an extremely large diameter such that 90.degree. of the
periphery of the condenser represents a large surface upon which
several discrete pads can be formed. Operating a drum-type
condenser at extremely high speeds will cause the fibers to be
thrown off the condenser by centrifugal force, and thereby cause
uncontrollable variations in the formed pads. Large drum-type
condensers are cumbersome to handle, and difficult to assemble on a
mounting axle. When such a condenser has to be changed; for
example, when a fibrous pad having a different shape is to be
formed; heavy equipment, such as a crane, normally must be
employed. If the drum-type condenser is made in segments, changing
the condenser will not require the use of heavy equipment; however,
assemblying a segmented condenser is time consuming, and involves
the additional problem of establishing effective seals between the
segments.
In the Banks, U.S. Pat. No. 3,518,726, each pad-receiving
compartment has a varying thickness in a circumferential direction
resulting from the formation of each compartment by arcuate side
plates and a substantially flat perforated bottom plate. In this
construction the pad-receiving compartments are thicker in the
center than at opposed ends, and the pads formed in such
compartments will assume the profile of the compartments. The
Banks' drum-type condenser lacks versatility since a pad having
only one specific profile can be formed therein, i.e., a pad having
a greater weight of fibers per unit area in the center region than
in adjacent end regions. To form fibrous pads with a different
profile, the drum-type condenser must be replaced by one having
surfaces therein defining a compartment having a profile
corresponding to that of the pad to be formed. This change of
condensers can be a cumbersome, difficult to achieve task, as
explained earlier in this application. Furthermore, the specific
configuration of surfaces defining compartments of different
profiles may be fairly intricate and difficult to form in drum-type
condensers.
In many applications it is desirable to form a fibrous pad which is
profiled in the cross-machine-direction, i.e., a fibrous pad
wherein different predetermined regions having different weights of
fibers per unit area therein are spaced from each other in the
cross-machine-direction. The apparatus disclosed in Banks is
designed only for forming fibrous pads which are profiled in the
machine-direction. Banks does not suggest an apparatus for forming
fibrous pads profiled in the cross-machine-direction.
In the Banks apparatus, the pads can be somewhat easily removed
from the drum-type condenser because of the tab connection between
adjacent pads. To further explain, if one of the pads is removed
from a compartment it will tend to lift adjacent pads out of their
respective compartments as a result of the force transmitted to
these adjacent pads through the tab connections. However, when
fibrous pads are formed as discrete, separate members, a problem
exists in removing such pads from three-dimensional compartments in
drum-type condensers. In order to remove discrete pads from the
compartments, the vacuum applied through the lower surface of the
compartments must be cut off. When the vacuum is cut off air is
permitted to become entrapped between fibers in the pads to expand
the pads into engagement with the peripheral sidewalls defining the
compartments. This expansion of fibers creates frictional drag
against the sidewalls, and prevents easy removal of the pads from
the compartments.
Apparatus employing a pad-formation assembly having a substantially
linear forming run, and allegedly operable to form pads of a
particular shape in a repeatable fashion is disclosed in U.S. Pat.
No. 2,949,646. The apparatus disclosed in this patent utilizes a
three-dimensional masking frame assembly having individual masking
elements with openings therein which define the shape of the pads
to be formed. A conveyor system movable in synchronism with the
masking frame assembly is disposed beneath the three-dimensional
masking frame assembly, and this conveyor system is foraminous
along its entire extent, i.e., the conveyor system is not provided
with masked, air-impermeable regions and unmasked, air-permeable
regions. Each masking element has a pad-defining opening, and the
regions outside of this opening are foraminous. The fibers carried
in an air stream are directed toward the conveyor and masking
elements from above the masking elements. The fibers directed into
the openings of the masking element deposit on the conveyor to form
pads generally having the shape of the opening. The remaining
fibers are deposited on the foraminous regions of the masking
elements, and therefore are not utilized to form pads. The fibers
deposited on the foraminous regions of the masking elements should
be recycled back into the process to achieve optimum utilization of
fibers. Equipment for recycling the fibers increases the complexity
and cost of the apparatus.
The apparatus disclosed in U.S. Pat. No. 2,949,646, does not
utilize a vacuum source to hold the formed pads on the conveyor at
the point of separation between the conveyor and the
three-dimensional masking frame assembly. Therefore, some
distortion or destruction of the pads may occur because of a
stronger affinity of the fibers for the masking frame assembly,
than for the underlying conveyor.
Air directed through regions of the conveyor underlying the
foraminous portions of the masking elements may cause fibers to
displace from the region defined by openings in the masking
elements to become trapped between the conveyor and the foraminous
portions of the masking elements. The displacement of fibers occurs
because the regions of the conveyor underlying the foraminous
portions of the masking elements are not masked to the passage of
air. These trapped fibers can adhere to the pads which are formed
and thereby cause distortions in the finished pad. This prevents
the repeatable reproduction of fibrous pads of a required
shape.
U.S. Pat. No. 3,501,813, issued to Lee et al., discloses an
apparatus for making a continuous, profiled fibrous web having a
longitudinally extending medial region with a greater weight of
fibers per unit area therein than longitudinally extending flanking
side regions. The Lee et al. apparatus requires the use of baffles
to engage an air-suspension of fibers within a conveying duct to
deflect the fibers into overlying relationship with a medial region
of a foraminous conveyor upon which the web is to be formed. This
deflection increases the volumetric flow rate of the deflected
portion of the air suspension of fibers. Lee et al allegedly
compensates for this increased flow rate by regulating valve
openings in a vacuum box disposed behind the foraminous conveyor to
permit the region of the vacuum box underlying the medial region of
the foraminous conveyor to accommodate the increased air flow.
The Lee et al. apparatus has several deficiencies. First, the use
of baffles to deflect the air suspension of fibers results in a
more complex apparatus than one in which deflecting baffles are not
used. Second, when it is desired to form continuous fibrous webs
with different profiles, the baffles must be rearranged within the
duct through which the air suspension of fibers is directed. This
rearrangement of baffles can be a difficult and a time consuming
task. In some instances the baffles may not be relocatable to a
required position to permit formation of a continuous fibrous web
having a required profile. Therefore, the Lee et al. apparatus
lacks the desired degree of versatility to easily permit its use
for forming continuous fibrous webs having many different
profiles.
U.S. Pat. No. 3,598,680, issued to Lee, discloses an apparatus for
forming continuous fibrous webs having a longitudinally extending
medial region with a greater weright of fibers per unit area
therein than in flanking side regions. This apparatus is described
an an improvement over the Lee et al. apparatus discussed above,
and employs separate fiberizing devices, and separate formation
chambers to form the continuous, profiled fibrous web. This
apparatus lacks versatility in permitting the formation of
continuous fibrous webs having many different types of profiles. In
order to vary the profile of a continuous fibrous web, extensive
modifications to the equipment are required. For example, the
formation chambers at various locations would have to be reoriented
to overlie different sections of the foraminous conveyor upon which
the web is to be formed. This requires considerable machine
reconstruction, and therefore is highly undesirable.
The apparatus and method disclosed in both the Lee et al. and the
Lee patents relate to the formation of continuous profiled webs,
and in no way suggest a method and/or apparatus for forming
discrete fibrous pads having a desired shape and profile, which can
be varied in a simple and reliable manner.
The method of continuous web formation disclosed in both the Lee et
al and Lee patents requires the formation of separate fibrous
strips which overlap each other in certain regions to define a
thickened region, i.e., a region having a greater weight of fibers
per unit area therein than in non-overlapped regions of the strips.
Stating this another way, the method disclosed in both the Lee et
al. and the Lee patent requires the formation of at least a portion
of a thickened region simultaneously with the formation of a
different region having a lesser weight of fibers per unit area
therein than in the thickened region. Therefore, certain stages of
the web forming operation disclosed in both the Lee et al. patent
and the Lee patent depend upon the masking effect, i.e., resistance
effect, of a portion of the web formed in a specific predetermined
region during a previous stage of the web forming operation. In a
later stage of the web forming operation the fibers will be
deposited initially in an unformed region of the web since the
resistance to air flow in such unformed region is considerably less
than the resistance through a partially formed region of the web.
As the web forming operation proceeds, the resistance to air flow
increases in what was the unformed region of the web as a result of
the build up of fibers in said region, and the air suspension of
fibers tends to divide to deposit fibers in different predetermined
regions. This division of the air suspension of fibers is not
controllable, since the changing resistance characteristics
resulting from the build up of fibers in different predetermined
regions cannot be determined or controlled easily during the web
forming operation. Furthermore, as the weight of fibers per unit
area in one predetermined region approaches the weight of fibers in
a different predetermined region a self-leveling effect occurs
which tends to destroy the profile of the web and thereby create an
unprofiled web having a substantially uniform weight of fibers per
unit area throughout. Therefore, the methods of web formation
disclosed in both the Lee and the Lee et al patents preclude the
controlled formation of profiled pads in which the weight of fibers
in different predetermined regions are different but quite close to
each other, and makes difficult to varying degrees all profiles
except those in which the differences in the weight of fibers per
unit area in different predetermined regions are extreme.
SUMMARY OF THE INVENTION
Apparatus of this invention for forming fibrous pads include a
pad-formation assembly having spaced, three-dimensional
pad-receiving compartments; adjacent compartments being separated
by air-impermeable regions. Each compartment has the shape of a
fibrous pad to be formed therein and is defined by a lower
air-permeable surface and air-impermeable sidewalls extending
outwardly from the air-permeable surface and disposed contiguous to
said air-permeable surface. The sidewalls provide positive control
for the shape of fibrous pads to be formed, and thereby eliminate
distortions at the perimeter of the formed pads. Sidewall sections
defining each compartment are movable relative to the lower
air-permeable surface to aid in releasing formed pads from said
compartments.
The apparatus of this invention includes drive means for moving a
substantially linear forming run of the pad-formation assembly
through a pad forming region. By employing a substantially linear
forming run the apparatus of this invention can be run at high
speeds without encountering the adverse effects of centrifugal
force which are encountered in apparatus employing drum-type
condensers.
The pad forming region includes a fiberizing means for
individualizing fibers from a feed matt and for forming an air
suspension of said individualized fibers. The pad forming region
further includes vacuum means disposed behind the forming run for
creating a partial vacuum to direct said air suspension of fibers
into the pad-receiving compartments whereat the air of said
suspension is pulled through the lower surface, and the fibers of
said suspension are deposited within the confines of said
compartments to form fibrous pads of a desired shape. Since the
pad-receiving compartments in the pad-formation assembly of this
invention are separated from each other by air-impermeable regions,
the vacuum means disposed behind the forming run is effective to
pull the air-suspension of fibers only into the pad-receiving
compartments, and not into the air-impermeable regions. Therefore,
fibers directed into the pad-receiving compartments will not tend
to be displaced laterally to cause distortions in the shape of the
completed fibrous pads. Furthermore, the quantity of fibers which
does deposit on the air-impermeable regions of the pad-formation
assembly is not so great as to require fiber recycling
equipment.
In a first specific embodiment of the apparatus of this invention
the pad-formation assembly includes an endlessly mounted masking
frame assembly and an endlessly mounted masked conveyor. The
masking frame assembly includes frame members having side surfaces
defining spaced openings which have the general shape of fibrous
pads to be formed, said side surfaces defining the side walls of
the pad-receiving compartments. The masked conveyor includes
spaced, air-permeable surfaces having the general configuration, or
shape, of a fibrous pad to be formed. The air-permeable surfaces
define the lower surface of the pad-receiving compartments, and are
separated from each other by air-impermeable regions. The masking
frame assembly is moved in synchronism with the masked conveyor to
define a linearly extending pad forming run which is directed
through the pad-forming region with the spaced openings defined by
the side surfaces of the frame members disposed in overlying
relationship with the air-permeable surfaces of the masked
conveyor. A sealing means is provided on the bottom surface of the
frame members for engaging the conveyor as the conveyor and masking
frame assembly pass through the pad-forming region to insure that
fibers do not become trapped between the frame members of the
masking frame assembly and the masked conveyor.
The side surfaces of the frame members which define the sidewall
sections of the pad-receiving compartments are moved relative to
the lower, air-permeable surface of the masked conveyor by
separating the masking frame assembly from the masked conveyor at
the downstream end of the pad forming run. In this manner, the
formed pads are retained only on a substantially flat surface of
the masked conveyor and can be transferred easily to a take-off
conveyor positioned downstream of the pad-forming region of the
apparatus.
A vacuum means is disposed behind the masked conveyor for
continuously pulling a partial vacuum through the air-permeable
surfaces of the masked conveyor at the downstream end of the
pad-forming region whereat the masking frame assembly is separated
from the masked conveyor. The application of a vacuum during
separation of the masking frame assembly from the masked conveyor
assures that the pad is retained on the conveyor, as opposed to the
masking frame assembly, and assures that this retention occurs
without distorting the formed fibrous pads.
A unique masking frame assembly and a drive and connection system
for said assembly forms a part of this invention. The masking frame
assembly is comprised of frame members which are removably secured
to support members. The frame members can be changed to define
openings of different shapes in the event that fibrous pads of
different shapes are to be formed. The support members are
interconnected in a desired spaced relationship by a plurality of
links, and adjacent links are interconnected by pins extending from
a chain into aligned openings of said adjacent links. The links are
interconnected to permit relative rotational and linear movement
between links to permit a change in cord length of the drive and
connection system as said system turns about spaced rolls at the
upstream and downstream end of the linear pad-forming run.
A second preferred embodiment of an apparatus of this invention has
a pad-formation assembly provided by a relatively thick, i.e., 1/4
inch to about 1 inch, flexible substrate directly adhered to an
endless conveyor. The flexible substrate replaces the masking frame
assembly employed in the first embodiment of this invention, and
has sections removed therefrom to expose air-permeable surfaces of
the conveyor which define the lower, air-permeable surfaces of the
pad-receiving compartments. Surfaces of the flexible substrate
which are formed by the removal of sections therefrom define the
sidewalls of the pad-receiving compartments, and adjacent
compartments are separated from each other by air-impermeable
regions. The air-impermeable regions can be defined by the flexible
substrate, or in the event the flexible substrate is air-permeable,
the surface of the conveyor underlying the flexible substrate can
be coated with a suitable air-impermeable material, such as
neoprene. The pad-formation assembly is mounted in an endless
fashion about spaced rolls to define a substantially linear forming
run to overcome the deficiencies of prior-art apparatus employing
drum-type condensers. A vacuum means is disposed below the
pad-forming run for directing the air-suspension of fibers into the
pad-receiving compartments in the same manner as in the first
embodiment of this invention.
The pad-formation assembly includes a linear pad-transfer run
opposed to the linear pad-forming run, and formed pads are
transferred from this transfer run to a second, pad-receiving
conveyor. The flexible substrate expands as the pad-transfer run
turns, at its downstream end, about one of the spaced rolls to
enter the upstream end of the pad-forming run. This expansion
causes sidewall sections defining the pad-receiving compartments to
move relative to each other and to the lower surfaces of said
pad-receiving compartments to aid in releasing the formed fibrous
pads from the compartments of the transfer run to permit relatively
easy transfer of the formed pads to the pad-receiving conveyor.
Applicant has discovered that this movement of the sidewall
sections is extremely desirable in enhancing pad removal from the
pad-formation assembly.
This invention further relates to apparatus and method for forming
discrete, shaped, profiled pads. Such apparatus is substantially
identical to the first and second embodiments of this invention,
and further includes profiling masking means disposed between the
vacuum means and the pad-forming run of the pad-formation assembly.
The profiling masking means prevents the establishment of a partial
vacuum through different predetermined sections of the
pad-receiving compartments during different stages of pad formation
to thereby establish a different "effective volumetric air flow"
through the different predetermined sections. In this manner a
weight of fibers per unit area is deposited in one predetermined
section which is different from the weight of fibers per unit area
which is deposited in a second predetermined section.
Reference to "effective volumetric air flow" throughout this
application, including the claims, refers to the total volumetric
flow of air through a predetermined section of each pad-receiving
compartment to provide a desired weight of fibers per unit area in
said predetermined section. A different effective volumetric air
flow can be established through different predetermined sections of
the pad-receiving compartments by any one of the following
means:
1. establishing the same volumetric demand for air per unit time
through a vacuum means for different lengths of time through
different predetermined sections of the pad-receiving compartments;
or
2. establishing a different volumetric demand for air per unit time
through a vacuum means for the same or different lengths of time
through different predetermined sections of the pad-receiving
compartments.
A further aspect of this invention relates to a unique method for
forming discrete, profiled fibrous pads wherein the weight of
fibers per unit area in different predetermined regions can be
established to be different than, but quite close to each other.
Applicant has discovered that the formation of a profiled fibrous
pad cannot be controlled within close tolerances by establishing a
different amount of open area through which air can be drawn by a
vacuum box through different predetermined regions underlying the
different predetermined sections of the pad-receiving compartment
in which different weights of fibers per unit area are to be
deposited. In the prior art methods for forming profiled webs, a
different amount of open area through which air can be directed by
a source of a vacuum has been established by varying the
concentration of open area in a foraminous member disposed over the
source of vacuum and also by regulating valve openings associated
with the source of vacuum.
Applicant has discovered that, except for extremely low basis
weight fiber deposits, resistance to air flow through a
pad-receiving compartment is greatly influenced by the basis weight
of a partially formed web deposited in said compartment during the
pad forming operation; and that the effect on fiber distribution
which is achieved by varying the amount of open area through which
air can be directed by a vacuum source is not as significant as the
effect of a partially formed fibrous web. Based on this discovery,
applicant recognized that the only effective means for establishing
different weights of fiber per unit area in different predetermined
regions of a fibrous pad, while maintaining close tolerances, is to
completely form each predetermined region with a specific weight of
fibers per unit area therein substantially independently of the
formation of every other predetermined region having a different
weight of fibers per unit area therein. Applicant's unique method
of this invention includes completely masking off a source of
vacuum to all sections of each pad-receiving compartment except the
section in which a region of a fibrous pad having a particular
weight of fibers per unit area is to be formed. After this region
has been completely formed, the vacuum source underlying the formed
region is completely masked to the passage of air, and a second
section of each pad-receiving compartment is exposed to vacuum to
form a predetermined region of the pad having a different weight of
fibers per unit area therein. The weight of fibers per unit area
deposited within a predetermined section of each compartment can be
controlled by selecting the time of exposure of said predetermined
section to a vacuum and controlling the volumetric air demand per
unit time of the source of vacuum. Since, at any given time, a
partial vacuum only is established through the sections of each
pad-receiving compartment which are to receive the same weight of
fibers per unit area therein, the weight of fibers per unit area
deposited in each predetermined region of the fibrous pad can be
controlled accurately by controlling the volumetric air demand of
the vacuum source and the predetermined time of exposure to said
partial vacuum of each predetermined section of each
compartment.
The volumetric air demand of the vacuum source and the time of
exposure to vacuum can be set within wide limits, depending upon
the weight of fibers per unit area which is to be deposited in a
predetermined section of the pad-receiving compartments. However,
the volumetric air demand per unit time of the vacuum source should
not be so great as to cause a fiber layer to excessively felt or
compact to a level which will prevent air from being drawn through
said fiber layer before complete formation thereof.
It is an object of this invention to form shaped fibrous pads in a
simple, reliable and repeatable fashion.
It is a further object of this invention to form shaped fibrous
pads in which the shape easily can be varied for different end uses
of said fibrous pad.
It is a further object of this invention to form shaped pads which
easily are transferable from pad-forming equipment to subsequent
converting equipment.
It is a further object of this invention to form shaped, profiled
fibrous pads in a simple, reliable and repeatable fashion.
It is a further object of this invention to form shaped, profiled
fibrous pads in which close tolerances in the weight of fibers per
unit area can be maintained in a repeatable fashion in
predetermined regions of said fibrous pad.
Other objects and advantages of this invention will become apparent
upon referring to the detailed description which follows taken in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional side elevation view of an apparatus of this
invention taken along line 1--1 of FIG. 2;
FIG. 2 is a sectional front elevation view of an apparatus of this
invention taken along line 2--2 of FIG. 1;
FIG. 3 is a sectional view of an apparatus of this invention taken
along line 3--3 of FIG. 2;
FIG. 4 is an enlarged view of the blocked portion of the apparatus
shown in FIG. 1;
FIG. 5 is an exploded isometric view of a pad-formation assembly,
including a masking frame assembly and a masked conveyor, employed
in an apparatus of this invention;
FIG. 6 is an enlarged view showing details of the separation of the
masking frame assembly from the masked conveyor in an apparatus of
this invention;
FIG. 7 is an isometric view of one product which can be produced by
an apparatus of this invention;
FIG. 8 is a schematic view of the drive means for moving the masked
conveyor and masking frame assembly in synchronization;
FIG. 9 is a schematic view of an apparatus according to a second
preferred embodiment of this invention;
FIG. 10 is an enlarged view of the blocked portion of FIG. 9
identified as "10;"
FIG. 11 is an enlarged view of the blocked portion of FIG. 9
identified as "11;"
FIG. 12 is an isometric view of a fibrous pad which can be
manufactured by the apparatus of FIG. 9;
FIG. 13 is an exploded isometric view of portions of the apparatus
shown in FIG. 9, and utilized for forming the fibrous pad shown in
FIG. 12;
FIGS. 14A, 14B and 14C show the cross sectional profile of the
fibrous pad shown in FIG. 12 during sequential stages of formation
according to the preferred method of this invention;
FIG. 15 is an isometric view of a different fibrous pad which can
be manufactured by the apparatus of FIG. 9;
FIG. 16 is an exploded isometric view of portions of the apparatus
of FIG. 9 utilized to manufacture the fibrous pad shown in FIG. 15;
and
FIGS. 17A, 17B and 17C show the cross-sectional profile of the
fibrous pad shown in FIG. 15, during sequential stages of formation
according to the preferred method of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a first embodiment of a pad forming apparatus
10 of this invention comprises a fiberizing means 12 for separating
fibers of a pulp lap and for forming an air suspension of said
fibers within a pad forming chamber 14. A vacuum box 16 is disposed
behind a pad-forming run 18 of a masked conveyor 20 which, along
with a masking frame assembly 22 forms a unique pad-formation
assembly of this invention. The vacuum box 16 is operative to pull
airborne fibers which are in chamber 14 onto the masked conveyor 20
whereby fibrous pads (e.g., 134, FIG. 7) are formed on the conveyor
and carried thereby to other converting equipment.
The unique pad-formation assembly of this invention is most clearly
illustrated in FIGS. 1-5, and, as stated above, includes the masked
conveyor 20 and the masking frame assembly 22. The masked conveyor
20 has air-impermeable regions 28. The air-impermeable regions
generally define a configuration, or shape of the air-permeable
surfaces 26 corresponding to the configuration, or shape of fibrous
pads which are to be formed. The masked conveyor 20 is formed from
a mesh screen of fiberglass in which the air-impermeable regions 28
are formed by a semi-conductive Teflon coating which is
substantially flush with the surfaces of the mesh screen. The
Teflon coating dissipates static charges which build up on the
fibers during the fiberizing operation. Coatings other than Teflon
can be utilized; however, it is preferred, but not required, that
such coatings be capable of dissipating static charges on the
fibers.
Referring to FIG. 5, the masking frame assembly 22 is comprised of
a plurality of frame members, and the frame members are disposed in
sets such that side surfaces of the frame members in each set
define an opening 30 having the shape of a pad to be formed. Each
set of frame members is comprised of vertical frame members 32 and
transversely extending frame members 34. The vertical frame members
32 and transversely extending frame members 34 are connected to
vertically spaced, horizontal support members 36 by screws 38 and
40, respectively. Each transversely extending frame member 34 has
an arcuate protuberance 42 which is either formed integrally
therewith, or is removably connected thereto by suitable fastening
means (not shown).
The vertically spaced, horizontal support members 36 of each set of
frame members are bifurcated to define spaced legs 45 which
straddle the upper and lower ends, respectively, of a frame support
and positioning link 46 (FIG. 5). The lower surface of each leg 45
is supported on shoulders 47, 49 at the upper and lower ends,
respectively, of each link 46.
In the preferred embodiment of the invention, adjacent sets of
frame members are interconnected in spaced relationship to each
other by a series of frame support and positioning links
46-48-50-52. As can readily be observed in FIG. 5, the links are
interconnected to each other by pins 60 which extend through
aligned openings 62 and 64 at the upper and lower ends of each
link. As can be seen in FIG. 3, the pins 60 which interconnect the
various links together are connected to, and extend from driven
chains 66. Each driven chain 66 is trained in an endless fashion
about a driven sprocket wheel 68 and a freely rotatable idler
sprocket wheel 70 (FIGS. 1 and 2). The opening 64 in each link is
elongate to permit relative linear movement between respective
links. The relative linear movement between links is required to
permit a change in cord length as the links reverse direction about
the sprocket wheels 68 and 70.
The driven sprocket wheels 68 are fixedly secured to a driven shaft
72 which is mounted for rotation in bearing blocks 74-76 (FIG. 2).
The end of the driven shaft 72 extending through the bearing block
76 has a sprocket wheel 78 fixedly secured thereto (FIG. 2 and FIG.
8), and it is through sprocket wheel 78 that the shaft 72 is driven
by a drive system to be described later. The idler sprocket wheels
70 are fixedly secured to an idler shaft 80 mounted for rotation in
bearing blocks 82-84 (FIG. 2).
The masked conveyor 20 is mounted in an endless fashion about a
roll 86 fixed to a driven shaft 88 (FIGS. 1 and 8), and about a
pair of idler rolls 90-92 (FIG. 1). The masked conveyor 20 is
provided with a row of openings 94 extending along each marginal
edge thereof for engagement with upwardly extending pins 96 which
are connected to the driven roll 86 (FIG. 2). The number and
arrangement of sprocket wheels and rolls over which the masked
conveyor 20 and masking frame assembly 22 are trained, and the
details of the drive are not critical to this invention and may be
varied.
Referring now to FIG. 8, the details of operation of the drive
control mechanism for synchronizing the movement of the masked
conveyor 20 and the masking frame assembly 22 will be described. A
power source, such as a motor (not shown), drives a sprocket wheel
98. A chain 100 is trained about the sprocket wheel 98 and a
sprocket wheel 102 which is fixedly connected to the driven shaft
88 to thereby rotate said shaft. As described above, the driven
roll 86 for rotating the masked conveyor 20 is also fixedly
connected to the shaft 88; therefore, rotation of shaft 88 drives
the roll 86 to drive the masked conveyor 20. A gear 104 is also
fixedly connected to the shaft 88 and is driven by rotation of said
shaft to rotate a gear 106 which is in meshing engagement
therewith. A sprocket wheel 108 is fixed with the gear 106 to
rotate therewith, and a chain 110 is trained about the sprocket
wheel 108 and a sprocket wheel 112 to thereby rotate said sprocket
wheel 112. The sprocket wheel 112 feeds into a differential gear
box 113 to drive an output sprocket wheel 114 at a rotational
velocity which is synchronized with the input velocity of the
sprocket wheel 112.
The output sprocket wheel 114 drives a chain 116 which is connected
to sprocket wheel 78 (FIGS. 2 and 8). The sprocket wheel 78 is
fixedly connected to the driven shaft 72 (FIGS. 2 and 8) to thereby
drive the shaft 72 and the driven sprocket wheels 68 connected
thereto. The differential gear box 113 permits phase adjustments to
be made between shaft 72 and shaft 88 when the air permeable
surfaces 26 of masked conveyor 20 move out of alignment with the
openings 30 defined by the frame members of the masking frame
assembly 22. Some slight misalignment may occur after a period of
operation of the apparatus as a result of tolerance variations in
the various components of the pad-formation assembly 24. By
energizing the differential gear box 113 when a misalignment
occurs, the pad-formation assembly 24 is controlled to insure that
the openings 30 defined by the frame members 24, 26 will remain in
overlying relationship with the porous, air permeable surfaces 26
(FIG. 2) as the masked conveyor 20 and masking frame assembly 22
pass through the pad forming chamber 14 (FIGS. 1 and 3) of the
apparatus 10.
The masked conveyor 20 and masking frame assembly 22 cooperate to
define three-dimensional pad-receiving compartments to eliminate
undesirable peripheral edge effects in the formed pads which are
otherwise encountered when pads are formed on substantially planar
surfaces without sidewall boundaries. Furthermore, the
three-dimensional pad-receiving compartments move along a
substantially linear forming run 18 along the pad forming chamber
14 to eliminate the problems encountered with the use of drum-type
condensers, all as has been set forth earlier in this
application.
As shown in FIGS. 3 and 4, suitable elastic seals 118 are
integrally connected to the lower surfaces of the vertical and
horizontal frame members 32, 34, respectively. The seals 118 engage
with the surface of the masked conveyor 20 to provide intimate
sealing engagement between the frame members of the masking frame
assembly and masked conveyor. This sealing arrangement has been
found highly desirable in preventing fibers from becoming entrapped
between the frame members of the masking frame assembly and masked
conveyor. If fibers became entrapped, they cause undesirable
distortions in the configuration, or shape of the finished pad.
Referring again to FIG. 1, the fiberizing means 12 is connected to
the pad forming chamber 14 through a conduit 120. Any suitable
fiberizing means, such as a Joa fiberizer, Hammermill, etc., can be
utilized in the apparatus 10 of this invention. In the preferred
embodiment of the invention, pulp lap is fed into a Joa fiberizer
having a rotating lickerin roll to separate or individualize fibers
from said lap, and centrifugal force created by rotation of the
lickerin roll directs the fibers in an air stream through the
conduit 120 into the pad forming chamber 14 (FIGS. 1 and 3).
Referring to FIG. 3, the pad forming chamber 14 is sealed by nylon
sealing elements 122 which are connected to sidewalls defining the
chamber 14. These sealing elements abut the links 46-48-50-52
during vertical travel of said links to insure that the chamber 14
is sealed to prevent air-borne fibers from escaping therefrom. The
sealing elements can be formed from any suitable material capable
of functioning in the above described manner.
Channel members 124 are provided for supporting the pad forming
chamber 14 which is separated to provide clearance for the
pad-forming run 18 of the masking frame assembly 22. The driven
chains 66 are disposed outside of the pad forming chamber 14 to
prevent the air borne fibers within said chamber from clogging the
chain 66. Clogging of the chain would impair the operation of the
apparatus.
The vacuum box 16 (FIG. 1) is mounted on the side of the masked
conveyor 20 which is opposite the side that sealingly engages the
masking frame assembly 22, and a vacuum is pulled through a conduit
126 (FIGS. 1 and 2) to thereby pull air through the air permeable
surfaces 26 of said masked conveyor. This vacuum directs the fibers
into the pad-receiving compartments of the pad-formation assembly
24 to thereby form the fibrous pads within said compartments. Since
the vacuum only pulls air through the air permeable surfaces 26,
there is little tendency for fibers to adhere to the
air-impermeable regions 28 of the conveyor. Therefore,
substantially all of the fibers directed into the pad forming
chamber 14 are utilized to form fibrous pads and are not deposited
in a useless fashion on the masked portions of the conveyor 20.
The vacuum box is sealed at its lower edge by a lower wall 128 and
is sealed at its upper end by the driven roller 86. The driven
roller 86 is perforated and provides direct air communication from
the outer periphery of the roller to the vacuum box (FIGS. 1 and
6), whereby a vacuum is constantly pulled through the conveyor 20
as the side surfaces of the frame members are moved relative to the
air-permeable surfaces 26 of the masked conveyor 20 by tangentially
separating the masking frame assembly 22 from said masked conveyor
at the upper vertical end of the pad-forming run 18 (FIG. 6). This
vacuum assist assures that the formed pad will be retained on the
masked conveyor, and will not tend to become distorted or destroyed
because of a greater affinity of the fibrous pad for the masking
frame assembly 22, than for the masked conveyor 20. By separating
the masking frame assembly 22 from the masked conveyor 20 the
formed fibrous pads can be removed easily from the conveyor 20 onto
a takeoff conveyor 129 which directs the pads in their formed
spaced relationship to suitable converting equipment (not shown),
whereat the individual pads can be assembled with other elements to
form a finished product. For example, the pads can be assembled
between suitable cover sheets to form disposable diapers.
A spinnerette or fiber leveling member 130 (FIG. 1) is provided for
leveling the surface of the formed fibrous pads. The spinnerette
includes a plurality of projecting fingers 132 which rotate to skim
the surface of the formed pads to perform the leveling operation.
This structure is conventional equipment in fiber web forming
machines and is well known to those skilled in the art.
Referring to FIG. 7, the masking frame members 32, 34 are utilized
to manufacture a fibrous pad 134 having a reduced width center
region 136, and which is specifically adaptable for use as an
absorbent component in a disposable diaper or the like. The fibrous
pad 134 can be made from 100 percent short cellulosic fibers of a
papermaking length less than 1/4 inch, such as wood pulp fibers and
second cut cotton linters, or from blends of such short fibers, and
longer, reinforcing textile-length fibers.
The various frame members 32, 34 can be removed from their support
members 36 and replaced with different frame members for defining
different shaped openings to manufacture different shaped fibrous
pads. For example, a different shaped fibrous pad may be required
in a diaper which is used by a boy than in a diaper which is used
by a girl. When the frame members are changed to form a different
shaped pad the masked conveyor must also be changed. In the
preferred embodiment of the apparatus, the opening defined by each
set of frame members is identical; however, it is within the scope
of this invention to utilize sets of frame members defining
different shaped openings to form fibrous pads of different
shapes.
The apparatus 10 of this invention can be utilized to manufacture
fibrous pads of various shapes for various uses, and is extremely
beneficial in applications wherein repeatable results are either
desirable or necessary. Also, the apparatus 10 of this invention
can include profiling masking elements between the vacuum box 16
and the pad-forming run 18 of the masking frame assembly 22 to
establish a different effective volumetric air flow through
different predetermined regions of the pad-receiving compartments
to thereby form profiled fibrous pads. The details of the profiling
features of this invention will be explained in conjunction with
the following description of the second preferred embodiment of the
apparatus of this invention, it being understood that such features
can be employed in the apparatus 10 which has been described
above.
Referring to FIG. 9, a second embodiment of an apparatus 200 is
shown for forming shaped, profiled, fibrous pads. The apparatus can
be utilized to form fibrous pads for many different shapes and
profiles; however, the specific apparatus described in this
application is utilized to manufacture shaped, profiled pads for
use in different disposable diapers specifically designed for use
by boy babies and girl babies, respectively. Such diapers are
described in copending application Ser. No. 168,159, filed on Aug.
2, 1971, and assigned to Scott Paper Company. This latter
application also discloses portions of apparatus 200, which are
described hereinafter, and clearly acknowledges that the apparatus
200 is the invention of Charles G. Kolbach, who is the inventor of
all of the subject matter claimed in the instant application.
The apparatus 200 has a fiberizing section 202 which includes a
rotary lickerin roll 204 disposed within a formation chamber 206.
The lickerin roll 204 is of conventional design, and comprises a
plurality of teeth disposed about the outer periphery thereof for
doffing individual fibers from sheets of pulp lap 208 and 210, and
for entraining said fibers in an airstream within the formation
chamber 206. If desired, only one sheet of pulp lap can be fed into
the fiberizing section, or the fiberizing section can be modified
to receive more than two sheets of pulp lap. Also, the fiberizing
section can be utilized to blend different fibers, such as short
fibers of a papermaking length less than 1/4 inch, and longer
reinforcing fibers of textile length.
The formation chamber 206 is closed at its downstream end by a
unique, movable pad-formation assembly 212 which is disposed in an
endless fashion about spaced rolls 214 and 216. At least, one of
the spaced rolls is driven to move the pad-formation assembly 212
in the direction indicated by arrow 218. The endless pad-formation
assembly 212 has an upper linear pad-formation run 220, and a lower
linear pad-transfer run 222. A plurality of pad-forming vacuum
boxes 224, 226 and 228 are disposed under, and in close proximity
to said pad-formation run, and function in conjunction with
profiling masks in a manner which will be fully described
hereinafter.
Referring to FIGS. 9 and 13, the unique pad-formation assembly 212
includes a relatively thin, open mesh conveyor 230 to which is
secured a relatively thick, flexible substrate 232. Preferably the
conveyor 230 is a woven member having apertures which are
sufficiently small to permit retention of fibers on the upper
surface thereof during the pad forming operation, while permitting
the air in which the fibers are entrained to pass through the
conveyor. Other conveyors can be utilized, such as nonwoven
conveyors and perforated, flexible sheet conveyors. The flexible
substrate 232 has a thickness in the range of from about 1/4 to 1
inch, and in the most preferred embodiment of this invention the
substrate has a thickness of from between 1/2 inch to about 3/4
inch. The flexible substrate 232 is adhered to the conveyor 230 by
any suitable glue or adhesive. The flexible substrate 232 must be
sufficiently flexible so that it can stretch as it turns about
spaced rolls 214 and 216 without unduly stressing the conveyor 230.
The imposition of undue stresses in the conveyor can cause said
conveyor to crack and thereby fail.
Preferably the flexible substrate 232 is air-impermeable and has
sections removed therefrom to define three-dimensional
pad-receiving compartments 234. Each pad-receiving compartment 234
is defined by a bottom, air-permeable surface 236 defined by the
conveyor 230, and sidewall segments 238 defined by surfaces of the
flexible substrate 232 provided by removing sections from said
substrate.
The flexible substrate 232 can be formed from soft rubbers, such as
natural rubber. Although natural rubbers are not semiconductive,
the normal moisture content within the air suspension of fibers
permits the dissipation of static charges from the fibers as they
engage the pad-formation assembly. The flexible substrate 232 can
also be formed from a foam material, such as unreticulated
polyurethane foam sold by Scott Paper Company. This unreticulated
polyurethane foam is air-permeable, and therefore when such a foam
is utilized the regions of the conveyor underlying the foam are
coated with a suitable air-impermeable substance, such as neoprene.
When an air-permeable foam is utilized as the flexible substrate
material, the side walls 238 also are coated with an air-impervious
substance such as neoprene.
The flexible substrate 232 can be adhered to the conveyor 230 by
any suitable adhesive means. In some cases, a surface of the
substrate can be rendered tacky by heat or chemical treatment, and
the tacky surface can provide the securing means for adhering the
substrate to the conveyor. When the flexible polyurethane foam
referred to above is utilized as the substrate material it can be
adhered to the conveyor 230 by a polyurethane adhesive such as
Bostik A and B mix (80/20) sold by Quelcor Adhesive Company of
Swarthmore, Pa. All constructions of the pad-formation assembly 212
include three-dimensional pad-receiving compartments 234 having a
bottom, air-permeable surface 236, and these compartments are
separated from each other by air-impermeable regions which
generally define a perimetrical shape corresponding to the
configuration, or shape of fibrous pads to be formed.
In the preferred embodiment of this invention, the apparatus 200
includes opposed sources of vacuum 235 and 237 disposed adjacent,
and outside of the downstream end of the pad-formation chamber 206.
The upper vacuum source 235 is effective to remove fibers which are
retained on the air-impervious regions of the pad-formation
assembly 212. In these regions the partial vacuum created by the
lower vacuum source 237 will have no effect since the partial
vacuum cannot be established through the air-impervious regions of
the pad-defining assembly. As a pad-receiving compartment 234
passes between the vacuum sources no pressure differential is
created across the fibrous pads since the vacuum established
through both the upper and lower vacuum boxes are substantially
identical, and will cancel each other. If desired, a source of
positive pressure 239 can be disposed outside of the pad-formation
chamber 206 closely adjacent and outside of the upstream end
thereof to blow any fibers out of the pad-receiving compartments
which are retained therein from fibrous pads which previously were
formed in said pad-receiving compartments.
Profiled pads are formed by positioning profiling masks between the
pad-formation run 220 of the pad-formation assembly 212 and vacuum
boxes 224, 226 and 228. These profiling masks prevent the passage
of air through the bottom air-permeable surface 236 of each
pad-receiving compartment 234 in different predetermined sections
thereof along the linear pad-formation run 220 of the pad-formation
assembly 212 to establish a different effective volumetric air flow
in said different predetermined sections to direct different
weights of fibers into said different predetermined sections.
Referring to FIG. 12, a fibrous layer 242 in the form of a shaped,
profiled fibrous pad is shown which can be formed by utilizing the
apparatus of FIG. 9. This fibrous pad has a substantially
hour-glass shape defined by a reduced width middle region 244. A
greater weight of fibers per unit area is disposed in the middle
region 244 than in opposed end regions 246 and 248. The weight of
fibers per unit area in each of the end regions 246 and 248 is
substantially identical. An exemplary fibrous layer 242 has a
middle region 244 with a basis weight of approximately 30
oz/yd.sup.2, and end regions 246 and 248 with a basis weight of
approximately 20 oz/yd.sup.2. This fibrous pad 242 is utilized
specifically in a diaper adapted to be used by a girl baby, as is
more fully described in copending U.S. application Ser. No.
168,159, which was referred to earlier in the instant
application.
Referring to FIG. 13, the fibrous pad 242 is formed by disposing
profiling masks 250, 252 and 254 between the pad-formation run 220
of the pad-formation assembly 212 and the pad forming vacuum boxes
224, 226 and 228, respectively. The profiling mask 250 has an open
mesh, air-permeable elongate center region 256, and air-impermeable
elongate end regions 258 and 260. The profiling mask 252 also has
an open mesh, air-permeable elongate center region 262, and
air-permeable elongate end regions 264 and 266. The profiling mask
254 has an air-impermeable elongate center region 268, and open
mesh, air-permeable elongate end regions 270 and 272.
The pad-forming vacuum boxes 224, 226 and 228 are connected to an
exhaust fan, or similar exhaust device (not shown), through
connecting conduits 274 (only one of which is shown in FIG. 13).
Each connecting conduit 274 can be provided with a valve therein to
control the volume of air which is pulled through its associated
vacuum box by the exhaust device. Alternatively, the valves can be
omitted, and separate exhaust devices can be connected to each of
the vacuum boxes to control independently the volume of air pulled
through each vacuum box. When the volumetric air demand through
each vacuum box is to be the same, a single exhaust device can be
employed, and the valves in conduits 274 can be omitted. However,
for purposes of equipment versatility, each of the connecting
conduits 274 is provided with a regulating valve therein so that
the volumetric air demand through each vacuum box can be
independently controlled.
To form the fibrous pad 242 shown in FIG. 12, the pad-formation
assembly 212 is driven at a substantially constant speed
sequentially over the profiling masks 250, 252 and 254 in the
direction indicated by arrow 218 in FIGS. 9 and 13. Referring to
FIGS. 9, 14A and 14B, the air suspension of fibers is divided
essentially into separate streams 276, 278 and 280 by the
application of a partial vacuum through the pad-receiving
compartments 234 which overlie the vacuum boxes 224, 226 and 228,
respectively. The vacuum boxes 224 and 226 are effective to direct
the fiber streams 276 and 278, respectively, into sustantially only
a middle section 279 of each pad-receiving compartment 234, as each
compartment passes over said vacuum boxes (FIGS. 14A and 14B). The
fiber streams 276 and 278 are directed substantially only into the
middle section 279 of each compartment because the elongate end
regions of the profiling masks 250 and 252 overlie the vacuum boxes
224 and 226 to prevent the fiber streams from being drawn into the
end sections of the pad-receiving compartment 234. Referring to
FIGS. 14A and 14B, some dusting of fibers occurs in the end
sections 281 and 283 of each pad-receiving compartment 234 during
the formation of the middle region 244 of the fibrous pad 242;
however, this dusting of fibers is of an extremely low basis
weight, i.e., less than 1 oz/yd.sup.2, and has relatively little,
if any, effect on the resistance to air flow through the end
sections of the pad-receiving compartment. Therefore this dusting
of fibers does not influence significantly the subsequent formation
of the end regions 246 and 248 of the fibrous pad 242. Therefore,
the middle region 244 of the fibrous pad 242 is formed completely
and substantially independently of the formation of end regions 246
and 248 of the fibrous pad.
Referring to FIGS. 9, 13 and 14C, the fiber stream 280 is directed
substantially only into end sections 281 and 283 of each
pad-receiving compartment 234 as each pad-receiving compartment
passes over the vacuum box 228 to thereby form the end regions 246
and 248 of the fibrous pad 242 completely and substantially
independently of the formation of the middle region 244 of the
fibrous pad. This formation of the end regions 246 and 248 is
effected by masking the vacuum box 228 to the passage of air by the
elongate center region 268 of the profiling mask 254 in a region
directly underlying the center section 279 of the pad-receiving
compartment 234. Some dusting of fibers may occur in the middle
region 244 of the fibrous pad during the passage of each
pad-receiving compartment over the vacuum box 228; however, this
dusting of fibers is substantially inconsequential, and does not
have any significant effect on the basis weight of the previously
formed middle region 244 of the fibrous pad.
Since the middle section 279 of each pad-receiving compartment 234
is exposed to a partial vacuum for a greater length of time than
the end sections 281 and 283, the profiled, fibrous pad 242 having
a greater weight of fibers per unit area in the middle region 244
than in the end regions 246, 248 can be formed by establishing the
same volumetric air demand through all of the vacuum boxes by
either one or more vacuum creating sources connected to said vacuum
boxes. Different effective volumetric air flows can be established
in different predetermined sections of the pad-receiving
compartments by any of the means set forth earlier in this
application to form a fibrous pad having predetermined regions,
each of which has a different weight of fibers per unit area
therein. The specific volumetric air demand through each of the
vacuum boxes, and the time of exposure of different predetermined
sections of a pad-receiving compartment to a partial vacuum can be
varied to form many different profiled, fibrous pads, and these
parameters are easily determinable by a person skilled in the art.
The critical criteria in setting the above parameters is to prevent
excessive compaction of the fibers in a predetermined section of
each pad-receiving compartment which will prevent air from passing
through said predetermined section prior to the complete formation
of the region of the fibrous pad formed in said predetermined
section. If air is prevented from passing through a partially
formed region of the pad, fibers will not be deposited in said
region to complete its formation.
Referring to FIG. 15, a fibrous layer 282 can be manufactured by
employing the method and apparatus of this invention in which the
pad-formation assembly and the profiling masks are different than
those employed to form the fibrous pad 242 shown in FIG. 12. The
fibrous layer 282 includes a main fibrous pad 284 and a secondary
fibrous pad 286. The main fibrous pad has a forward end region 288
with the greatest weight of fibers per unit area therein, e.g.,
over 30 oz/yd.sup.2. A middle region 290 of the main fibrous pad
has a lesser weight of fibers per unit area therein, e.g., 20
oz/yd.sup.2, than the forward end region, and the secondary fibrous
pad 286 has the same weight of fibers per unit area therein as the
middle region 290. A rearward end region 292 of the main fibrous
pad has the least weight of fibers per unit area therein, e.g., 17
oz/yd.sup.2. The above-described absorbent layer 282 is
specifically adapted for use as an absorbent component in a
disposable diaper designed for boy babies, as is more fully
described in copending U.S. Pat. application Ser. No. 168,159,
which was referred to earlier in this application.
Referring to FIG. 16, a pad-formation assembly 294 for forming the
fibrous layer 282 includes main pad-receiving compartments 296 and
secondary pad-receiving compartments 298 which are in transverse
alignment with the main pad-receiving compartments. Profiling masks
300, 302 and 304 are disposed over the vacuum boxes 224, 226 and
228, respectively; and the pad-formation assembly is directed at a
substantially constant speed sequentially over these masked, vacuum
boxes in the direction indicated by arrow 218. The main fibrous pad
284 is formed in each of the main pad-receiving compartments 296,
and the secondary fibrous pads 286 are formed in each of the
secondary pad-receiving compartments 298. The preferred method of
forming the fibrous layer 282 is identical to the preferred method
of forming the fibrous layer 242 shown in FIG. 12. This preferred
method involves the forming of predetermined regions of the fibrous
pad having the same weight of fibers per unit area therein
completely and substantially independently of the formation of
every other predetermined region having a different weight of
fibers per unit area therein.
Referring to FIGS. 16 and 17A, the secondary fibrous pad 286 and
the middle region 290 of the main fibrous pad are formed as the
transversely aligned main and secondary pad-receiving compartments
pass over the vacuum box 224. The vacuum box 224 is masked to
prevent the passage of air through the forward and rearward end
sections 301 and 303, respectively, of each of the main
pad-receiving compartments 296. Some minor dusting of fibers occurs
in the forward and rearward end sections 301 and 303 of each main
pad-receiving compartment as it passes over the vacuum box 224;
however, as explained earlier in this application, this dusting of
fibers has substantially little, if any, effect on the resistance
to air flow through said forward and rearward end sections of the
pad-receiving compartments during the subsequent formation of said
forward and rearward end regions 288 and 292, respectively, of the
main fibrous pad 284.
Referring to FIGS. 16 and 17B, the middle region 290 of the main
fibrous pad 284 is formed in a middle section 305 of each main
pad-receiving compartment 296, as each of said compartments 296
pass over the vacuum box 226. The vacuum box 226 is masked to
prevent the passage of air through all sections of the main and
secondary pad-receiving compartments except the middle section 305.
Again, some fine dusting of fibers may occur in other sections of
the pad-receiving compartments as said compartments pass over the
vacuum box 226; however, this dusting of fibers is virtually
inconsequential, and does not influence, to any significant extent,
the subsequent formation of other regions of the fibrous layer
282.
Referring to FIGS. 16 and 17C, the rearward end region 292 of the
main fibrous pad 284 is completely formed within a rearward end
section 303 of each main pad-receiving compartment 296, as each of
said compartments passes over the vacuum box 228. The vacuum box
228 is masked to prevent the passage of air therethrough in all
regions except the region underlying the rearward end section 303
of each main pad-receiving compartment 296.
In forming the fibrous layer 282 all sections of the pad-receiving
compartments are exposed to a partial vacuum for the same length of
time. Therefore, a different effective volumetric air flow is
established through sections of the pad-receiving compartments by
creating a different volumetric air demand through each of the
vacuum boxes 224, 226 and 228, respectively. It is within the
purview of this invention to include additional vacuum boxes and
additional masking means, depending upon the specific weight of
fibers per unit area which is to be included in a given region of
the fibrous layer. It is also within the purview of this invention
to establish different effective volumetric air flows by any of the
methods set forth earlier in this application. The criteria which
must be met in forming fibrous pads according to the most preferred
method of this invention is that each region which has a specific
weight of fibers per unit area therein must be formed completely
and substantially independently of the formation of every other
region having a different weight of fibers per unit area therein.
Also, as explained above, the parameters of time exposure to the
partial vacuum, and the specific volumetric air demand established
through the vacuum boxes must be such as to permit the deposition
of the desired weight of fibers per unit area in a given region
without excessively matting the fibers into a dense matt through
which air will not pass prior to the complete formation of said
given region.
Referring to FIGS. 13 and 16, each of the profiling masks is
provided with a handle 306, or other similar grasping means,
adjacent one end thereof to permit easy removal of each mask when
it is desired to substitute a different mask therefor, or when it
is desired to eliminate the masks. By substituting or omitting
profiling masks, the apparatus 200 can be utilized to form many
different profiles of absorbent pads, or to form shaped, unprofiled
pads.
In manufacturing throw-away diapers for use by girl babies and boy
babies, the method and apparatus for positioning the formed
absorbent pads between opposed cover layers is identical.
Therefore, the following description will be limited to the method
and apparatus of positioning the fibrous pad 242 (FIG. 12) between
opposed cover layers for manufacturing disposable diapers
specifically adapted for use by girl babies.
Referring to FIGS. 9 and 10, the fibrous pads 242, in the form of
fluff batts of cellulosic fibers of papermaking length, have an
exposed upper surface which is leveled by the teeth, or bristles of
a rotating spinnerette 308 disposed at the downstream exit end of
the formation chamber 206. The fibrous pads are then directed about
the roll 214 where they are contacted by a cover layer 310 which is
directed against the pad-formation assembly 212 by an idler roll
308. The cover layer 310 cooperates with the pad-formation assembly
to confine the fibrous pads 242 within their respective
pad-receiving compartments. The cover layer 310 is moved in
synchronism with the pad-formation assembly 212 to a position in
engagement with the lower, transfer run 222 thereof. The cover
layer 310 also is supported by an upper pad-receiving run 312 of a
transfer conveyor 314. The cover layer 310 and the overlying
fibrous pads are fed on the transfer conveyor 314 over a transfer
vacuum box 315 disposed directly under the upper, pad-receiving run
312 of said transfer conveyor. A partial vacuum is applied through
the vacuum box 315 to create a pressure differential across the
fibrous pads 242 to transfer allegience of said pads from the
pad-transfer run 222 of the pad-formation assembly 212 to the
pad-receiving run 312 of the transfer conveyor 314. This partial
vacuum is applied through the cover layer 310, which is a fibrous
air-pervious web, and the fibrous pads 242 are relatively thick and
thereby prevent the air drawn through the vacuum box from being
drawn easily through said fibrous pads. In this manner, the
above-described pressure differential is established across the
fibrous pads. This pressure differential is maintained on the
fibrous pads as the pad-formation assembly 212 commences to turn
about the support roll 216 at the downstream end of the transfer
run 222 to thereby separate the transfer run from the pad-receiving
run 312 of the transfer conveyor 314.
Referring to FIG. 11, separation of the fibrous pads 242 from the
pad-formation assembly 212 is enhanced by the movement of a
sidewall section defined by the flexible substrate 232 relative to
the bottom surface 236 and the other sidewall sections as the
pad-formation assembly 212 is stretched about the support roll 216.
The new position of the sidewall section is indicated in FIG. 11 by
the numeral 238' and functions to open the compartment and permit
the fibrous pad to be separated easily from the compartment without
damaging or distorting the shape of said pad. The fibrous pads 242
are disposed on the cover layer 310 as said cover layer is fed off
the transfer conveyor 314. Adhesive is applied to the upper exposed
surface of the cover layer 310 in regions disposed between adjacent
fibrous pads at a suitable adhesive station, indicated
schematically at 316. An opposed cover layer 318, which can be
fluid-pervious or fluid-impervious, is superimposed over the spaced
fibrous pads downstream of the adhesive station to form a composite
structure consisting of the fibrous pads and the opposed cover
layers. The composite structure is then fed to subsequent finishing
stations (not shown) whereat the composite structure is formed into
individual throw-away diapers by severing and folding in any
desired manner, as is well known in the art.
* * * * *