Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF FORMING AND BONDING
FLUFF PADS FOR DIAPERS AND THE LIKE
BACKGROUND AND SUMMARY OF INVENTION
This invention relates to a method of forming
and bonding fluff pads for diapers and the like, and
more particularly, to a method employing an annular
drum which achieves both pad formation and thermal
bonding on one vacuum drum.
Fluff forming drums have been known for a
considerable time -- see, for example, co-owned patent
3,599,293. Further, both the processes of pad
formation and thermal bonding are existing art, yet no
one has performed both on a single drum.
A significant product advantage accrues from
the invention which performs both of these processes
on a single drum -- as compared to the separate
processes. This advantage resides in retaining the
shape of the pad. Diaper producers have expended much
effort in developing pad shapes to achieve optimum
performance in the take-up of excreta. Yet, the very
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step of removing the pad from the forming drum
distorts the shape. Thus, the bonding step introduces
more distortions into the now-unconfirmed pad.
A significant operational advantage resides
in the better control of air flows (both forming and
bonding) because these can be segmented on the drum.
More particularly, these advantages (and others) can
be tabulated as follows:
1. Removal of the pad -- because of the
increased bonding possible with the synthetic fluff
mixture, the ~ads may be removed from the forming
molds more cleanly.
2. Integrity of the pad -- because the pads
are bonded in the forming mold, the initial formation
has not been disturbed by handling. This provides the
largest amount of fiber entanglement possible and,
hence, the greatest bonded fiber areas. It will be
appreciated that handling such as bending or
extension/compression of the pad tends to dislodge the
fiber bonds established in the forming process.
3. Simplicity of mechanism -- one drum may
be used for both processes thereby eliminating
intermediate transfer mechanisms.
4. Cost savings -- with the inventive method
it is possible to eliminate the tissue overwrap
usually present to assist in transporting the pad to
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the point of insertion into the final product, i.e.,
disposable diaper, sanitary pad, etc.
The basic process includes first converting
wood pulp or other fibrous materials and the bonding
polyol~fin into fibers suspended in air via a
hammermill or other fiberizer. These suspended
fibers, called fluff blend, are then collected on a
screen surface which allows the air to pass through
while retaining the fluff blend.
The screen consists of woven or other
formaminous material which has a significantly open
area (to air flow) and is formed in the shape of the
desired pad. These screen areas or pocket means are
supported on a rotating drum through which the air is
exhausted.
Pad formation may take place in several steps
consisting of fluff blend deposits, additive deposits
such as super-absorbents, and scarfing. Scarfing
refers to the process of brushing the outside surface
of the newly formed pad with a rotating brush roll or
similar aggressive surface. These steps may be
repeated to form multiple layers of materials in the
pad.
The formed pads then continue rotating on the
drum into an area where hot air is directed through
the pads and exhausted from the drum interior. At
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least a portion of the pad contains synthetic fibers,
i.e., the polyolefin fibers of a melting point lower
than the natural (wood) fibers which constitute the
majority of the pad. By heating the pad to the
melting point of the synthetic fibers but below the
wood fibers, the synthetic fibers can be made to melt
and "wick" to the wood fibers. Once heated to the
bonding temperature, the pads are cooled causing the
molten materials to solidify and bond the fiber
structure together to achieve the advantages outlined
above. The concurrent forming and bonding on a
forming drum to provide an undistorted diaper pad is
not taught by the prior art, viz., Patents 2,544,019;
2,714,081; 3,201,499; 3,051,369; 3,619,322; 3,939,240;
4,592,708 and 4,666,647.
Other advantages and objects of the invention
may be seen in the details of the ensuing
specification.
BRIEF DESCRIPTION OF THE DRAWINGS:
The invention is described in conjunction
with an illustrative embodiment, in which --
FIG. 1 is a fragmentary side elevational
view, essentially schematic, drum apparatus
constructed according to the teachings of this
invention;
FIG. 2 is an enlarged longitudinal sectional
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view, also somewhat schematic, of one of the diaper
pads of FIG. l;
FIG. 3 is a fragmentary end elevational view
of the apparatus of FIG. l; and
FIG. 4 is a perspective, exploded view,
partially schematic of the forming drum of the
apparatus.
DETAILED DESCRIPTION:
In the illustration given and with reference
to first to FIG. 1, the numeral 10 designates
generally the pad forming drum which is seen to
support a plurality of circumferentially spaced
pockets 11 in the outer peripheral surface thereof.
Normally, the drum has a diameter of 8 to 10 feet
(2.5-3 meters). In the illustration given, the drum,
for simplicity, is illustrated only "one wide".
However, it will be appreciated that a number of
pockets may be disposed in axially aligned relation.
The drum 10, along one side is equipped with a spider
12 to provide means for connecting a drive generally
designated 13 and which rotates the drum (See FIG.
3).
Referring again to FIG. 1, a pulp blend of
wood fiber and polyolefin is introduced as at 14 into
a hammermill generally designated 15. The hammermill
15 is rotated by means of a motor 16 through a drive
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generally designated 17. The fiberized fluff blend
designated by the arrow 18 is forced through ducts 19,
20 into sector-defining plenums 21, 22 which extend
partially circumferentially around the drum 10.
Heated air is introduced through sector-defining
plenums 23, 24 and the formed pads P are withdrawn
from the drum under vacuum applied by the vacuum box
25 onto a conveyor 26. Thereafter, the pads P are
enveloped between webs of non-woven and polyethylene
~o as at 27 and 28.
After the pads have been removed, the
now-empty pockets 11 are cleaned by virtue of air
being drawn radially outward as at 29 in the vacuum
hood 30. A pipe 31 is connected to a vacuum source
(not shown). Immediately thereafter a release powder
is applied through a plenum 32 to the still-empty
pockets 11.
It is believed that a specific example of the
operation of the invention will be helpful in the
understanding thereof.
EXAMPLE
The web 14 (see the left hand portion of FIG.
1) in this example is a pulp blend consisting of 85%
wood fiber and 15% olefin and is introduced in the
amount of 2,400 pounds per hour. A suitable pulp
blend is available from Hercules, Inc. under the
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designation PULPEX E-338. Air at room temperature,
viz., 70F., is also drawn in to the hammermill 15 in
the amount of 3,000 CFM which is illustrated
schematically as at 33.
The first layer of material laid down in the
pockets 11 is the fluff release agent from the
sector-defining plenum 32 and this layer is designated
schematically in FIG. 2 by the numeral 34. Next, the
fluff blend being transported in the duct 19 to ^he
sector-defining plenum 21 is laid down to form a layer
35 with the a.r exiting through an exhaust port 36.
This first layer 35 is subjected to scarfing as at
37.
Bonding of the first layer 35 is achieved by
heated air entering the second sector-defining plenum
23 as at 38 in the amount of about 1,000 CFM at about
320F. This air exits through port 39 at about
210F. Next, a layer of super absorbent powder
schematically represented in FIG. 2 by the numeral 40
is laid down in the area occupied by the plenum 41.
A second fluff blend layer 42 (see FIG. 2) is
laid down through the plenum 22 with the air exiting
through the port 43. Thereafter, bonding occurs with
the heated air in the plenum 24 entering as at 44 in
the amount of 1,000 CFM at 350F. and exiting through
the port 45 at a temperature of about 250F.
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Cooling air is introduced to the last sector
46 of the forming drum 10 and exhausts through the
port 47.
FORMING DRUM STRUCTURE
Referring to FIG. 3, it will be seen that the
forming drum 10 is supported upon a frame generally
designated 48. The frame 48 has releasably clamped
thereto a translation tube 49 which rotatably carries
a shaft 50 to which a spider 12 is attached. For
greater details on the construction of the drum 10
reference can be made to co-pending, co-owned Patent
No. 4,995,141.
The spider 12 carries a ring 51, a plurality
of pad forms 52 (which define the pockets 11?, and
through the pad forms, a second ring 53 -- see also
FIG. 4. Thus, the inboard ring 53 is connected only
to the ring 51 via the arcuately shaped pad forms 52.
The pad forms 52 are equipped on both sides with
clamps as at 54 (see the central left hand portion of
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Pitted within the drum 10 -- more
particularly, the axially spaced rings 51, 53 is a
stationary plenum generally designated 55 (see FIG.
4). This is fixedly mounted on the frame 48 and is
sealingly related to the drum rings 51, 53.
More particularly, the inner plenum 55
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includes a generally cylindrical structure defined by
rings 56 and 57 which are integrated together by means
of transverse and radially extending members as at 58,
59 and 60. Fitted within the rings as at 61 are
annular plates closing the plenum and which are
advantageously constructed of transparent material
such as plexiglass. Further, sector-forming plates as
at 62 are provided within the radially extending
members 59, 60 and the axially extending member 58.
Now referring to FIG. 1, it will be seen that
a number of sector-forming plates are provided as at
62. Thus, a sector-shaped chamber is provided for
each one of the outer plenums 21-24, 29 and 32. No
plenum is necessary for reducing the cooling air 46
which is at room temperature and which is drawn in
under the influence of the exhaust port 47.
SUMMARY OF OPERATION
A web 14 which advantageously includes both
wood pulp and polyolefin is introduced into the
hammermill 15. Room temperature air is also drawn
into the hammermill as at 33 with the fluff blend
being delivered simultaneously to the plenums 21 and
22. The fibers are deposited in pockets 11 (see FIG.
4) with the air flowing radially inwardly under the
plenum 21 and being exhausted through port 36.
Next, heated air to provide the bonding
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function is introduced through the plenum 23 and
exhausted through the port 39. Super absorbent powder
may be added at this stage at the station 41 to
provide the layer 40 -- see FIG. 2.
Another layer of fluff blend 42 is developed
by the fibers issuing from the plenum 22 and exiting
through the exhaust port 43. Bonding of these fibers
is achieved by heated air flowing radially inwardly
from the plenum 24. Thereafter, the pad is cooled by
air as at 46, removed onto the conveyor 26 under the
influence of vacuum as at 25 for further processing as
with the polyethylene and non-woven webs 27, 28. The
pockets 11 are then cleaned by air flowing radially
outwardly into the plenum 29 under the influence of
vacuum as at 31. The still empty pockets 11 are then
coated with a release material 34 (see FIG. 2) by
virtue of the plenum 32.
While in the foregoing specification, a
detailed description of an embodiment of the invention
has been set down for the purpose of illustration,
many variations in the details herein given may be
made by those skilled in the art without departing
from the spirit and scope of the invention.
