Note: Descriptions are shown in the official language in which they were submitted.
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ABSORBENT ARTICLE INCLUDING A COMPONENT
LAYER HAVING A HINDRANCE TO FLUID FLOW ACROSS THE LAYER
FIELD OF THE INVENTION
The present invention relates to sanitary absorbent articles such as feminine
sanitary
napkins, adult incontinence pads, infant diapers, underarm absorbent pads, and
medical
bandages.
BACKGROUND OF THE INVENTION
Sanitary absorbent articles are articles of manufacture that generally are
used to
absorb and retain bodily exudates; they have both medical and non-medical
uses.
Conventional sanitary absorbent articles generally comprise several different
layers of
material joined together to form a laminate. Each of these layers is referred
to as a
"component layer" and serves a specific function within the article. Each
layer is thus
usually fabricated from a material different than that of the others, and has
different
physical properties and characteristics.
The uppermost layer of material, i. e, that which faces the body of the wearer
of the
article is conventionally termed the "cover layer" or "top sheet". As the
layer of the article
which comes into physical contact with the human body, the cover layer must be
relatively
soft to the touch so as to avoid discomfort and prevent abrasions to the human
tissue below
during the time which the article is worn. The cover layer must be fluid
permeable so as to
permit the ingress of the bodily exudate into the article to be absorbed and
retained. At the
same time however, it should remain dry to prevent moisture from accumulating
against
the skin of the wearer that could cause irritations. In order to meet these
desired
characteristics, conventional cover layers are manufactured from a woven
hydrophobic
material or a synthetic plastic material having a large number of relatively
small apertures
per unit surface area.
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The difficulty with cover layers of this construction is that a bodily exudate
to be
absorbed may accumulate on the surface of the cover layer for a small period
of time
before the entire volume of the exudate is actually absorbed into the layer
and the layers)
below. Depending on the orientation of the article with respect to the wearer
and to
S gravitational forces, the accumulated exudate may begin to flow across the
surface of the
cover layer before being absorbed. In some instances this may not be a problem
in that the
exudate will simply be absorbed at a point a distance away from its point of
impact on the
surface of the article. In others, however, the exudate may eventually flow
off the article
itself and onto the garments of the wearer, presenting an extremely
undesirable situation.
As an example, where the article is a sanitary napkin, it will be appreciated
that
when in use by a woman, the napkin assumes a generally curved shape with
respect to her
body. When she is sitting or standing, any menstrual fluid not immediately
absorbed by
the article may flow across the surface thereof to the lowest point along the
curve.
Generally, such flow is longitudinal and the curvature of the cup itself will
then prevent the
liquid from flowing any further. However, when the wearer is lying down (e.g.
during
periods of sleep or rest) the conformation of the napkin itself will not form
an obstruction
preventing any fluid from flowing longitudinally off the edge of the article.
Thus the
undergarments of the wearer may become soiled.
This phenomenon is not unique to cover layers as, to a lesser extent, it has
been
observed on some of the other component layers (e.g. the transfer layer and
the absorbent
layer) of an absorbent article as well. In certain instances, exudate may flow
along the
surface of one of these other layers and egress the article instead of being
absorbed and
retained thereby.
It would be desirable therefore to have a component layer of an article to
include a
hindrance to fluid flow across the layer.
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OBJECT AND STATEMENT OF THE INVENTION
It is thus an object of an aspect of the present invention to provide a
component
layer of material suitable for use in a laminate sanitary absorbent having an
increased
ability to hinder the flow of a fluid across the surface thereof.
It is a further object of an aspect of the present invention to provide a
sanitary
absorbent article including a component layer having an increased ability to
hinder the flow
of a fluid across the surface thereof.
As embodied and broadly described herein, the present invention provides a
component layer suitable for use in a sanitary absorbent article, the
component layer
including:
(A) a substantially planar first portion; and
(B} a substantially planar second portion overlapping said first portion;
said overlapping portions forming a vertical hindrance to the flow of a fluid
across the
component layer.
Component layers suitable for use in an absorbent article in accordance with
the
present invention are generally formed of relatively thin, flexible and
lightweight material.
Preferably, a component layer of the present invention is rectangular or dog-
bone in shape,
having two relatively shorter opposing transverse sides and two relatively
longer opposing
longitudinal sides. It should be understood, however, that no particular shape
is essential to
the invention, and, for example, component layers of the present invention may
be any
shape, including oval or circular. From each longitudinal side of the
component layer there
may project a flap, preferably trapezoidal in shape. Neither the presence of
such flaps, nor
their particular shape, is essential to the present invention. The component
layer is usually
symmetric about an imaginary longitudinal centre-line running through its
centre point and
generally parallel to the longitudinal sides, and about an imaginary
transverse centre-line
running through its centre-point and generally parallel to the transverse
sides.
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The component layer also has two faces designated by the general direction in
which they are oriented when an article into which the component layer is
incorporated is
being correctly worn by a user. A "body-facing face" which faces the body of
the wearer
of the article, and a "garment-facing face" which is the opposite face and
which faces the
wearer's environment, which, although depending on which part of the body the
article is
being employed, is usually a garment. The thickness of the component layer at
any
particular point is the distance between the body-facing face and the garment-
facing face
measured along the line perpendicular to the plane defined by the longitudinal
and
transverse centre-lines when the layer is laid flat.
Particularly with respect to a component layer which when incorporated into a
sanitary absorbent article will contact the skin of the wearer thereof, but
also true to a lesser
extent of other component layers of the article, the layer should be smooth
enough to
ensure her/his physical comfort and prevent abrasion. In this respect, it is
required that
both the first portion and the second portion of a component layer of the
present invention
be substantially planar so that the user of an article into which the
component layer is
incorporated will not perceive the presence of these portions as a result
their overlap, nor
be caused irritation thereby. As used in the context of the present
specification, the term
"substantially planar" is meant to include surfaces having gentile undulations
(i.e. of a
relatively minor amplitude) but not those having large wrinkles or sharp
creases, ridges or
the like. Furthermore, two portions should be considered to be overlapping
when they, at
least partially, lie one on top of the other when the component layer is laid
flat. The
overlapping portions may be in complete contact with one another, in partial
contact, or
generally in a spaced apart relationship. No particular state in this respect
is required nor is
essential, neither when the article is laid flat nor when it is in use.
When the two portions are in an overlapping relationship as previously
described
they will form a vertical hindrance to fluid-flow across the component layer.
One
important cause of this hindrance will be the contact of the liquid with the
edge of the
second (i.e. closer to the wearer) portion of the overlapping portions. It is
not necessary,
however, that this edge be at any particular angle with respect to the plane
formed by the
component layer when laid flat. Edges having a variety of angles will
accomplish this task
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(i. e. of hindering) although some angles may present a greater hindrance than
others. The
word "vertical" in the context of the present specification should not
therefore be
interpreted as requiring any such angle, as it is used herein simply to
indicate a hindrance is
in the path of the fluid-flow desired to be hindered. It is not necessary that
such a
5 hindrance completely, or even partially, arrest the flow of the fluid
desired to be so
hindered. In order to constitute a hindrance within the present context, it is
merely required
that the flow rate of at least a part of the fluid to be hindered is reduced
by contact with the
hindrance. The direction of flow to be hindered is that "across" the body-
facing face of
component layer as opposed to through the thickness of the layer itself.
Advantageously, the overlapping portions are capable of accepting the fluid
thereinbetween. In such instances some of the fluid flowing across the
component layer
may, when encountering the edge of the second portion, may be directed and
caused to
flow between the portions. Such fluid may be detained within the overlapping
portions
increasing the hindrance presented thereby.
More preferably, the overlapping portions are separable, i.e. capable of being
separated, meaning that the pocket formed thereby is expandable. (The term
'pocket'
should be understood in the present context as signifying a compartment formed
in the
material that comprises the cover layer having a single opening, excluding any
pores
present in the material itself.) As such, as fluid accumulates between the
portions in the
pocket formed thereby, the distance between the portions will increase as the
pocket
expands. It is more likely then that additional fluid flowing across the layer
will become
entrapped within the pocket; separable overlapping portions thus form a
greater hindrance
to fluid flow. The portions may be caused to be capable of separating through
a variety of
methods. Such will be the case, for example, where the material of which the
component
layer is formed is extensible, where either portion itself contains pleats or
folds permitting
this effect, where there is a slight excess of material forming the second
portion, or simply
where the sides of the layer are capable of being drawn in. Preferably, the
article is
constructed such that the pocket will return to its original (i.e. unexpanded)
state once all of
the fluid entrapped therein has been absorbed into the article.
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A simple embodiment of the present invention is a component layer formed of a
single piece of material and having a pleat, i.e. a flattened fold therein
doubled over upon
itself, or a plurality of such pleats. The pleat will thus consist of three
layers of material
and a cross-section thereof would be Z-shaped. The pleat would define two
pockets, one
with an opening accessible from the body-facing face of the component layer,
the other
with an opening accessible from the garment-facing face of the component
layer. For
present purposes, it is only the pocket having an opening accessible from the
body-facing
face that is relevant.
The pleats should be formed and/or positioned such that the opening in the
pocket
faces in the direction from which it is likely that the fluid to be absorbed
will flow. Thus,
where the article is a sanitary napkin, the pleats will most likely lie
parallel to the
transverse centre-line at some distance therefrom, i.e. closer to the
longitudinal ends of the
article than the transverse centre-line, and have a body-facing face opening
facing in the
direction of the transverse centre-line. In this manner, when fluid flowing
across the body-
facing face of the component layer encounters the opening in the pocket
defined by the
overlapping portions its progress is hindered somewhat thereby, increasing the
chances that
the fluid will be absorbed within the article.
It should be understood, however, that no particular placement of the pleats
with
respect to the transverse centre-line is required, and thus pleats may be
located at any
distance away therefrom. In addition, no particular number of pleats, nor any
particular
size nor spacing, is required, and thus these qualities/quantities may all
vary within the
scope of the present invention.
An alternative embodiment of the invention would have two different sheets of
material of the appropriate size and shape to form a cover layer overlap in
over a portion of
each. The overlapping portions thus formed would be similar to that described
above
except that they would form a two-ply sleeve instead of a three-ply pocket.
(The term
'sleeve' should be understood in the present context as signifying a
compartment formed in
the material that comprises the cover layer having two openings, excluding any
pores
present in the material itself.) The sleeve so formed would have two openings,
one
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accessible from the body-facing face of the component layer, the other
accessible from the
garment-facing face. The sheets should be constructed such that the opening in
the body-
facing face of the sleeve faces in the direction from which it is likely that
the fluid to be
absorbed will flow. In this manner, when fluid flowing across the body-facing
face of the
component layer encounters the opening in the sleeve defined by the
overlapping portions
its progress is hindered somewhat thereby, increasing the chances that the
fluid will be
absorbed within the article. Additionally, fluid flowing between the portions
would be
directed thereby through the sleeve and be deposited on the underlying
component layer.
This embodiment of the invention is not limited to an article having a single
sleeve
in a component layer; component layers constructed of multiple sheets having a
plurality of
sleeves are also included. Moreover, it is not necessary that each of the
sheets of a
component layer of this embodiment of the present invention be of the same
material, as
component layers having sheets of different material are also within its
scope.
A third embodiment of the invention would encompass the simple placement of
additional material on the cover layer to form a "sleeve-like" overlapping
portion and act as
a hindrance to fluid flow. Alternatively, this material could be sealed to the
cover layer in
various configurations to form a "pocket-like" structure to entrap the fluid
in addition to
acting as a simple hindrance.
In another aspect, as embodied and broadly described herein, in accordance
with the
present invention there is provided a laminate sanitary absorbent article
comprising a
plurality of component layers, wherein one of said component layers includes:
(A) a substantially planar first portion;
(B) a substantially planar second portion overlapping the first portion;
the overlapping portions of one of said component layers forming a vertical
hindrance to
the flow of a fluid across the one of said component layers. Preferably, the
overlapping
portions are capable of accepting the fluid thereinbetween.
Typically, the component layers of a laminate absorbent article of the present
invention will include a fluid-permeable body-facing layer, a fluid-impervious
garment-
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facing layer, and an absorbent layer between the body-facing layer and the
garment-facing
layer. Additionally, a fluid-permeable intermediate layer (also termed a
'transfer layer')
may be included between the body-facing layer and the absorbent layer. Any one
(or more
than one, or even all) of the body-facing layer, the intermediate layer (if
present), and the
absorbent layer may include overlapping portions in accordance with the
present invention
as previously described.
Preferably, there is further provided a laminate sanitary absorbent article
having an
absorbent layer of the present invention wherein the second portion of the
absorbent layer
has a substantially-impermeable first-portion-facing face. No particular means
for causing
the first-portion facing face of the second portion to be substantially-
impermeable are
essential to the present invention. Hence, within the scope of this aspect of
the invention
are a variety of conventional techniques for causing same, including the
application of
chemicals or films to the second portion, and even at the limit the
interposition of a
material between the first portion and the second portion. Where the latter is
the case, it is
not necessary that such material be affixed to the first-portion-facing-face
of the second
portion.
The advantage of such a construction is the reduction of the possibility of
"wet-
back". Wet-back is a condition familiar to those skilled in the art wherein,
because of
pressure exerted on the absorbent napkin, some of the fluid entrapped therein
is released
(generally along the reverse of the pathway through which it was absorbed}. By
constructing the first-portion-facing face of the second portion in this
manner, any fluid
released by pressure on the napkin will not have a pathway of escape (or will
have a
reduced chance of encountering an escape pathway) and will thus remain
entrapped within
the napkin, despite the pressure.
Of further advantage, there is provided a laminate sanitary absorbent article
having
an absorbent layer of the present invention further comprising a spacer member
between
the first portion and the second portion of said absorbent layer, said spacer
member having
a higher void volume per unit volume than the first portion and the second
portion.
Generally, the material of which an absorbent layer is constructed is selected
in view of its
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capability and capacity to absorb and retain a fluid as opposed to the rate in
which such
fluid is absorbed and retained. Thus it is probable to have a very high-
volume, yet slow-
rate, absorbent material. The spacer member, however, having a relatively
large void
volume per unit volume will be able to rapidly, albeit temporarily, store a
large volume of
fluid. Thus, fluid flowing across the surface of the absorbent layer will
encounter the
vertical hindrance formed by the overlapping portions and will enter the space
member and
be temporarily stored pending its absorption by the absorbent layer.
Advantageously, there is further provided a laminate sanitary absorbent
article
having an absorbent layer of the present invention wherein the first portion
of said
absorbent layer has areas of reduced average pore size as compared with the
overall
average pore size of said absorbent layer, to provide for increased wicking.
It is known in
the art that the absorptive force exerted by a material is inversely related
to the size of the
pores in the material into which the fluid to be absorbed will be drawn. Thus,
the areas of
reduced pore size will tend to be more absorptive then the rest of the first
portion or of the
layer and will have a wicking effect. In this manner, more of the fluid
contacting the
vertical hindrance will be directed within the areas of reduced pore size and
drawn in
between the overlapping portions, reducing the likelihood that any fluid will
escape the
napkin and soil the wearer's garments.
Similarly, it would also be possible to form a transfer layer of the present
invention
having such areas of reduced pore size.
Other objects and features of the invention will become apparent by reference
to the
following description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of preferred embodiments of the present invention is
provided hereinbelow with reference to the following drawings, in which:
Figure 1 is a perspective view of a laminate sanitary absorbent article
including a
cover layer of present invention;
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Figure 2 is a top plan view of the article (body-facing face) of Figure 1;
Figure 3 is a cross-sectional view of the article along the line 3--3 in
Figure 2;
Figure 4 is a cross-sectional view of a second embodiment similar to that of
Figure
5 3;
Figure 4a is an expanded view of the cross-section in Figure 4;
Figure 5 is a cross-sectional view of the article of Figure 1 while in use by
a wearer
in a standing position;
Figure 6 is a cross-sectional view similar to that in Figure 5 while the
wearer is
10 lying in a prone position;
Figure 7 is an expanded view of the cross-section in Figure 6;
Figure 8 is a cross-sectional view of a third embodiment similar to that of
Figure 3
including a cover layer of the present invention;
Figure 9 is a cross-sectional view of a fifth embodiment including a transfer
layer of
the present invention;
Figure 10 is a cross-sectional view of a sixth embodiment including a transfer
layer
of the present invention;
Figure 11 is a cross-sectional view of a seventh embodiment including a cover
layer
and a transfer layer of the present invention;
Figure 12 is a cross-sectional view of an eighth embodiment including a cover
layer
and a transfer layer of the present invention;
Figure 13 is a cross-sectional view of a ninth embodiment including an
absorbent
layer of the present invention;
Figure 14 is a cross-sectional view of a tenth embodiment including an
absorbent
layer of the present invention;
Figure 15 is a cross-sectional view of an eleventh embodiment including an
absorbent layer of the present invention; and
Figure 16 is a perspective view of a twelfth embodiment of an absorbent layer
of
the present invention.
In the drawings, preferred embodiments of the invention are illustrated by way
of
example. It is to be expressly understood that the description and drawings
are only for
SUBSTITUTE SHEET (RULE 26)
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purposes of illustration and as aid to understanding, and are not intended to
be a definition
of the limits of the invention.
S DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Figure 1 & 2 there is illustrated a preferred embodiment of a
laminate
sanitary absorbent article of the present invention, a feminine sanitary
napkin 20. The
napkin 20 is of a dog-bone shape and has four sides: two longer curved
opposing
longitudinal sides 22, 24 and two shorter rounded opposing transverse sides
26, 28. An
isosceles-trapezoidal-shaped flap 30, 32 projects from each of the
longitudinal sides 22, 24.
The napkin 20 is symmetric about two perpendicular imaginary centre-lines: a
longitudinal
centre-line 34 running down the length of the napkin 20 through its centre-
point and
equidistant from the longitudinal sides 22, 24; and a transverse centre-line
36 running
across the width of the napkin 20 through its centre-point and equidistant
from the
transverse sides 26, 28. The napkin 20 has two faces, a body-facing face 38
and an
opposing garment-facing face (not shown). Each component layer thereof has a
similar
physical description.
In this embodiment, the length of the napkin 20 along the longitudinal centre-
line
34 is 24 cm, while that along the transverse centre-line 36 is 8.1 cm not
including the flaps
30, 32, and 14.5 cm including the flaps 30, 32. The length of the napkin 20 as
measured
along a line parallel to the transverse centre-line 36 stretching across the
widest portion of
the "dog-bone" is 11.0 cm. The flaps 30,32 themselves are in the shape of an
isosceles
trapezoid and have a base measurement (i.e. the parallel side which joins the
longitudinal
edge of the napkin) of 5.0 cm, and a top measurement (i.e. the opposing
parallel side) of
3.0 cm.
Referring to Figure 3, the napkin 20 includes a body-facing cover layer 40, a
garment-facing barrier layer 44, an absorbent layer 42 between the cover layer
40 and the
barrier layer 44. As shown in Figures 4 and 4a, such an absorbent napkin most
preferably
includes a transfer layer 46 between the cover layer 40 and the absorbent
layer 44.
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PCT/CA99/00139
Attached to the garment facing surface of the barrier layer 44 are a number of
adhesive
strips 48 for affixing the napkin 20 to the undergarment of the wearer. Each
of these
component layers will now be individually described.
Cover La ~~er
The cover layer 40 may be a relatively low density, bulky, high-loft non-woven
web material. The cover layer 40 may be composed of only one type of fibre,
such as
polyester, or it may be composed of bicomponent or conjugate fibres having a
low melting
point component and a high melting point component. The fibres may be selected
from a
variety of natural and synthetic materials such as nylon, polyester, rayon (in
combination
with other fibres), cotton acrylic fibre and the like and combinations
thereof.
Bicomponent fibres may be made up of a polyester core and a polyethylene
sheath.
The use of appropriate bicomponent materials results in a fusible non-woven
fabric.
Examples of such fusible fabrics are described in U.S. patent 4555430 issued
November
26, 1985 to Mays. Using a fusible fabric increases the ease with which the
cover layer 40
may be mounted to the adjacent transfer layer 46 and/or to the barrier layer
44.
The cover layer 40 preferably has a relatively high degree of wettability,
although
the individual fibres comprising the cover may not be particularly
hydrophilic. The cover
material should also contain a great number of relatively large pores. This is
because the
cover layer 40 is intended to absorb body fluid rapidly and transport it away
from the body
and the point of deposition. Preferably, the fibres which make up the cover
layer 40 should
not loose their physical properties when they are wetted, in other words they
should not
collapse or loose their resiliency when subjected to water or body fluid. The
cover 40 may
be treated to allow fluid to pass through it readily. The cover layer 40 also
functions to
transfer the fluid quickly to the other layers of the absorbent structure.
Thus, the cover 40 is
preferably wettable, hydrophilic and porous. When composed of synthetic
hydrophobic
fibres such as polyester or bicomponent fibres, the cover 40 may be treated
with a
surfactant to impart the desired degree o~wettability.
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PCT/CA99/00139
Most preferably, the cover layer 40 is made of polymer film having large
pores.
Because of such high porosity, the film accomplishes the function of quickly
transferring
body fluid to the inner layers of the absorbent structure. Apertured co-
extruded films such
as RETICULON brand, for example, described in U.S. patent 4,690,679 are useful
as cover
layers in the absorbent structures of this invention.
Transfer Laver
Optionally, adjacent to the cover layer 40 on its inner side and bonded to the
cover
layer 40 is a fluid transfer layer 46 that may form part of the absorbent
system. The transfer
layer 46 provides the means of receiving body fluid from the cover layer 40
and holding it
until the highly-dense absorbent layer 42 has an opportunity to absorb the
fluid.
The transfer layer 46 is, preferably, more dense than and has a larger
proportion of
smaller pores than the cover layer 40. These attributes allow the transfer
layer 46 to contain
body fluid and hold it away from the outer side of the cover layer 40, thereby
preventing
the fluid from re-wetting the cover layer 40 and its surface. However, the
transfer layer 46
is, preferably, not so dense as to prevent the passage of the fluid through
the layer into the
absorbent layer 42.
The transfer layer 46 may be composed of fibrous materials, such as wood pulp,
polyester, rayon, flexible foam, or the like, or combinations thereof. The
transfer layer 46
may also comprise thermoplastic fibres for the purpose of stabilizing the
layer and
maintaining its structural integrity. The transfer layer 46 may be treated
with surfactant on
one or both sides in order to increase its wettability, although generally the
transfer layer 46
is relatively hydrophilic and may not require treatment. The transfer layer 46
is preferably
bonded on both sides to the adjacent layers, i.e. the cover layer 40 and the
absorbent layer
42.
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14
Absorbent aver
PCT/CA99/00139
Immediately adjacent to and bonded to the transfer layer 46 is the absorbent
layer
42. The absorbent layer 42 is preferably a highly dense layer having a fine
porosity. It has a
large liquid holding capacity and it is extremely retentive. Most preferably,
the absorbent
layer 42 is composed of compressed sphagnum moss material. More specifically,
the
sphagnum moss is formed as a board by air or wet laying and calendering to
obtain a
relatively thin, i.e. from about 0.01 to 0.10 inch thick, relatively dense,
i.e. from about 0.2
to 1.0 g/cm3, sheet like structure. It is then tenderized, reducing the
density to between
0.05 and 0.1 g/cm'. The structure may include a layer of Kraft tissue
laminated on one or
both surfaces of the sphagnum moss layer. Preferably, a fibrous component is
admixed
with the sphagnum moss material. The fibrous component is suitably a natural
or synthetic
textile fibre such as rayon, polyester, nylon, acrylic or the like, having a
length of from
about 0.25 to 1.5 inches and a denier of from about 1.0 to 5. The fibrous
component may
be present in an amount from about 2 to 20% by weight, most preferably from 4
to $%.
The absorbent layer 42 may also comprise other components such as wood pulp,
synthetic
wood pulp, thermomecanical pulp, mechanically ground pulp, polymers,
surfactants, super-
absorbents and the like.
In an alternative embodiment, the absorbent system includes a single layer of
pulp
fluff material (the transfer layer is omitted). The absorbent layer 42
preferably comprises a
pulp fluff material and may optionally include other absorbent materials or
non-absorbent
materials which aid in stabilizing the absorbent structure such as conjugate
fibres, fusible
fibres, binders, sphagnum peat moss particles, super-absorbents, and the like
and
combinations thereof, and may optionally include other absorbent materials or
non-
absorbent materials which aid in stabilizing the absorbent structure such as
conjugate
fibres, fusible fibres, binders, sphagnum peat moss particles, super-
absorbents, and the like
and combinations thereof.
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Barrier Leer
Underlying the absorbent system is a barrier layer 44 comprising liquid-
impervious
film material so as to prevent liquid that is entrapped in the absorbent layer
42 from
5 egressing the sanitary napkin and staining the wearer's undergarment. Most
preferably, the
barrier layer 44 is made of polymeric film, such as polyethylene which is both
inexpensive
and readily available. The polyethylene is capable of fully blocking the
passage of liquid or
gas that may emanate from the absorbent system. In a variant, breathable films
may be
used that allow passage of gases while blocking liquid.
The cover layer 40 and the barrier layer 44 are joined along their marginal
portions
so as to form an enclosure that maintains the absorbent system captive. The
joint may be
made by means of adhesives, heat-bonding, ultrasonic bonding, radio frequency
sealing,
mechanical crimping, and the like and combinations thereof. The peripheral
seal line is
shown in Figure 2 by the reference numeral 52.
Adhesive Structures
In order to fiuther enhance the stability of the sanitary napkin 20, the
napkin may be
provided with adhesives 48, such as hot-melt adhesives capable of establishing
a temporary
bond with the undergarment material. These adhesives 48 may be applied to the
bottom
(garment-facing face) of the barrier layer 44 in various patterns, including
complete
adhesive coverage, parallel longitudinal lines, a line of adhesive following
the perimeter of
the structure, transverse lines of adhesive or the like. Alternatively, the
sanitary napkin of
this invention may be attached to a belt that encircles the waist of the
wearer.
Physical Description
As shown in Figures 1 to 4a, the cover layer 40 of the napkin 20 has a series
of
overlapping portions SOa, SOb, SOc, SOd; two on either side of the transverse
centre-line 36.
These overlapping portions SOa, SOb, SOc, SOd each stretch transversely across
the width
of the cover layer 40 generally parallel to the transverse centre-line 36 and
to one another.
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16
Each of the overlapping portions SOa, SOb, SOc, SOd is formed by a pleat in
the material of
which the cover layer 40 is composed. These pleats are simply flattened folds
in the cover
layer 40 which when viewed along a longitudinal cross section of the napkin
(as in Figures
3, 4, and 4a) are of a flattened Z-shaped. The overlapping portions SOa, SOb,
SOc, SOd thus
comprise a first portion 52a, 52b, 52c, 52d and an overlapping second portion
54a, 54b,
54c, 54d.
The edge 56b of the second portion 54b of the second SOb of the series of
overlapping portions fonms a line parallel to the transverse centre-line 36 of
the napkin at
distance 6.1 cm therefrom. Similarly, the edge 58b of the first portion 52b of
the second
SOb of the series of overlapping portions forms a line parallel to the
transverse centre-line
36 at a distance 6.8 cm therefrom. Thus the width (i.e. distance between the
edge 56b of
the second portion 54b and the edge 58b of the first portion 52b) of the
overlapping
portions 52b, 54b of the second SOb of the series of overlapping portions is
0.? cm. In a
similar fashion, the edges 56a, 58a of both the second portion 54a and the
first portion 52a
of the first 50a of the series of overlapping portions form lines parallel to
the transverse
centre-line. The distance finm the edge 56a of the second portion 54a to the
transverse
centro-line 36 is 7.3 cm, and from the edge 58a of the first portion 54a is
8.0 cm. Thus, the
width of the first SOa of the series of overlapping portions is 0.7 cm. As the
napkin 20 is
symmetric about the transverse centre-line 36 these distances and measurements
are valid
for both sides thereof (i.e. the measurements with respect to SOd are the same
as those for
SOa and those of SOc are the same as those of SOb). It should be understood
that none of
these distances is critical to the invention and thus a wide variety of
overlapping portion
configurations is possible. Furthermore, while overlapping portions that are
parallel to the
transverse centre-line 36 are highly preferred, it would still be possible
within the scope of
the present invention to have such portions be at an angle thereto.
Referring to Figure 5, when a sanitary napkin 20 of the present invention is
in use
by a female, the napkin adopts a curved shape with respect to her body about
the pudendal
region. Despite the curvature of the napkin, the overlapping portions 52a/54a,
52b/54b,
52cI54c, 52d/54d, preferably remain flush with one another to prevent the
wearer from
being caused discomfort thereby.
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17
Referring to Figure 6, menstrual fluid 60 to be absorbed by the napkin will be
deposited on the cover layer 40 at a point between the first of the series of
overlapping
portions SOa, SOb, SOc, SOd on either side of the transverse centre-line 36.
When the
wearer is lying flat (i.e. on her stomach or back), some of the fluid 60 not
immediately
absorbed by the napkin may begin to flow along the body-facing surface 38 of
the cover
layer 40 in the direction indicated by the arrow in Figure 6.
A portion of the fluid 60 may encounter the second SOb of the series of
pleats,
l0 specifically the edge 56b of the second portion 54b thereof. This edge 56b
constitutes a
vertical hindrance to fluid-flow and should retard the exudate's 60 progress
across the layer
40, giving it more time to absorbed though the cover layer 40. A part of the
exudate will
most likely flow under the second portion 54b separate the second portion 54b
from the
first portion 52b, and enter the pocket 62b, as depicted in Figure 7. Such
exudate 60 will
be temporarily retained within the pocket 62b until absorbed through the cover
layer 40 and
into the layers below. The raised second portion 54b of the now open pocket
62b will thus
constitute an even greater vertical hindrance to fluid flow across the layer
40.
A part of the exudate may flow over top (i.e. along the body-facing surface
38) of
the second portion 54b, as opposed to becoming entrapped within the pocket
62b. In such
case, if not absorbed, it may continue to flow along the body-facing surface
38 of the cover
layer 40 and may eventually encounter the first SOa of the series of pleats.
This pleat is
identical to the second pleat SOb and the interaction of the fluid therewith
is the same as
that described hereinabove in relation thereto.
2:5
In this embodiment, the material forming the cover layer 40 is not extensible,
but is
lightweight and flexible. Thus when fluid separates the first 52b, 52a and
second portions
54b, 54a and opens the pocket 62b, 62a, a portion of the longitudinal side of
the napkin
around where the edge of the pleat is attached will be drawn in. The second
portion 54b,
54a of the pleat is therefore under a minor tension so that when there is no
further exudate
to be absorbed within the pocket 62b, 62a, the second portion 54b, 54a will
return to its
original state and will lie substantially planar over top the first portion
52b, 52a.
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18
In the embodiment illustrated in Figure 8, the overlapping portions 850a,
850b,
850c are not formed by a series of pleats, rather the cover layer 840 of this
embodiment is
formed from a series of discrete segments 864, 866, 868, 870 of material
(others not
shown). The primary segment 870 forms the centre of the layer and stretches a
distance
away from the transverse centre-line on either side thereof. The transverse
edge portions of
the primary segment 870 will form the first portions 852c of the third
overlapping portions
850c on either side of the transverse centre-line (only one side shown). The
secondary
segments 868 have a first transverse edge 856c closer to the transverse centre-
line of the
layer than the transverse edges 858c of the primary segment 870. Thus the
first edge
portion of the secondary segment 868 will form the second portion 854c of the
third
overlapping portion 850c on either side of the transverse centre-line (only
one side shown).
The secondary segments 868 stretch away from their first transverse edges 856c
some
distance past the transverse edge 858c of the first segment 870 to a second
transverse edge
858b. This second transverse edge portion forms the first portion 852b of the
second
overlapping portion 850b on either side of the transverse centre-line (only
one side shown).
The tertiary segments 866 have a first transverse edge 856b closer to the
transverse centre-
line of the layer than the second transverse edges 858b of the secondary
segments 868 but
further than the second transverse edges 858c of the primary segment 870. The
tertiary
segments 866 stretch away from their first transverse edges 856b some distance
past the
second transverse edge 858b of the secondary segment 868 to a second
transverse edge
858b. This second transverse edge portion forms the first portion 852a of the
first
overlapping portion 850a on either side of the transverse centre-line (only
one side shown).
The quaternary segments 864 have a first transverse edge 856a closer to the
transverse
centre-line of the layer than the second transverse edges 858a of the tertiary
segments 866
but further than the second transverse edges 858b of the secondary segments
866. The
quaternary segments 864 stretch away from their first transverse edges 856a
some distance
to form the transverse edges 826 of the layer itself. This first edge portion
of the
quaternary segment 864 will form the second portion 854a of the second
overlapping
portion 850a on either side of the transverse centre-line (only one side
shown).
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19
In cover layers of this construction, the overlapping portions 850a, 850b,
850c form
sleeves as opposed to pockets. The general interaction with flowing exudate is
similar to
that described hereinabove with respect to pocket-forming overlapping
portions, with an
exception that the sleeves formed by the overlapping portions 850a, 850b, 850c
do not
have the ability to retain liquid therein pending its absorption through the
cover layer,
rather they will act as conduits for the exudate and will deposit it directly
on the layer
underlying the cover layer.
In addition other component layers of a laminate sanitary absorbent napkin may
also be constructed in accordance with the present invention. In Figure 9,
there is
illustrated a napkin having a transfer layer 946 including a plurality of
pleats 950a, 950b
similar to those as described above in relation to the cover layer. Similarly,
in Figure 10,
there is a illustrated a napkin having a transfer layer 1046 including a
series of "sleeve"
overlapping portions 1O50a, and 1O50b formed as described herein above.
The employ of such a transfer layer is generally independent of whether other
component layers of the same napkin have been constructed in accordance with
the present
invention. Thus, it would be possible to have a napkin with a transfer layer
and/or a cover
layer and/or an absorbent layer constructed in accordance with the present
invention.
Where it is desired to have two of such layers, e.g. a cover layer and a
transfer layer, of the
present invention incorporated into a single napkin, alternate embodiments are
again
possible. Referring to Figure 11, in one alternate embodiment a single
overlapping portion
(e.g. 1150a, 1150b) will contain portions of both of the component layers. In
this respect,
the cover layer 1140 and the transfer 1146 layer are laid one on top of the
other and a series
of pleats is formed therein as if the layers were a single layer, thus forming
a composite
layer. In Figure 12, there is another alternative embodiment wherein the
overlapping
portions 1250a, 1250b are sleeves instead of pockets.
Now referring to Figure 13, in another embodiment of the present invention the
absorbent layer 1342 of a sanitary napkin is formed having overlapping
portions 1350a,
1350b as previously described. The napkin depicted in Figure 13 includes an
absorbent
layer 1342 sandwiched between a cover layer 1340 and a barrier layer 1344. It
would be
SUBSTITUTE Sf~fE~ (RULE 26)
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WO 99/42066 PCT/CA99/00139
possible to form such a napkin including a transfer layer (not shown) between
the cover
layer 1340 and the absorbent layer 1342.
Alternative embodiments of absorbent layers of the present invention are also
5 possible. In Figure 14, the face of the second portions 1454x, 1454b of the
overlapping
portions 1450x, 1450b which faces the first portion 1452x, 1452b of the
overlapping
portions 1450x, 1450b of the absorbent layer 1444 is a substantially fluid-
impermeable.
(Shown in the Figure through the interposition of an impermeable layer 1464x,
1464b of a
plastic material between the second portion 1454x, 1454b and the first portion
1452x,
10 1452b. Note that for illustrative purposes, the relationship of the
impermeable layer 1464x,
1464b to the first 1452x, 1452b and second 1454x, 1454b portions is not to
scale.)
Referring to Figure 15, it is also possible to interpose between the first
portion
1552x, 1552b and the second portion 1554x, 1554b of an absorbent layer 1544 of
the
15 present invention a spacer member 1566x, 1566b having void volume per unit
volume
which is greater than that of the material which comprises the absorbent
layer. While there
are a variety of conventional materials that may be used as spacer members,
the preferred
material is bulky, air-laid and non-absorbent such as polyethylene or
polypropylene. (Note
that for illustrative purposes, the relationship of the spacer member 1566x,
1566b to the
20 first 1552x, 1552b and second 1554x, 1554b portions is not to scale.)
Finally, referring to Figure 16, it is possible to form a absorbent layer 1642
wherein
the body-facing face 1638 has areas of reduced average pore size 1668 as
compared with
the overall average pore size of the layer. There are several conventional
methods for
forming such areas, including subjecting the layer to pressure by passing it
through
patterned rollers, as is well known in the art.
The above description of preferred embodiments should not be interpreted in a
limiting manner since other variations, modifications and refinements are
possible within
the spirit and scope of the present invention. The scope of the invention is
defined in the
appended claims and their equivalents.
SUBSTITU T E SNEE~T (RULE 26)
