U.S. patent number 3,871,378 [Application Number 05/343,774] was granted by the patent office on 1975-03-18 for absorbent bandage.
This patent grant is currently assigned to The Procter & Gamble Company. Invention is credited to Robert C. Duncan, Grace L. Smith.
United States Patent |
3,871,378 |
Duncan , et al. |
March 18, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Absorbent bandage
Abstract
An absorbent bandage or sanitary napkin suitable for use as
either a catamenial or an incontinent device adapted to conform
more effectively to the shape of the body in the area of the female
genitalia whether the wearer is in a standing, sitting or lying
position, said napkin being so constructed as to assume an upwardly
concave conformation in both the transverse and the longitudinal
directions when worn. The absorbent pad of a preferred embodiment
of a sanitary napkin of the present invention is comprised of a
basically hydrophobic, non-woven, needle-punched polyester two
sheet of relatively low density in contiguous association with one
or more absorbent core layers of basically hydrophilic bleached
wood pulp fibers airlaid and compressed into a continuous web of
relatively high density. The interface thus formed between the top
sheet and the absorbent core provides a gradient of diminishing
capillary size between the top sheet which has a relatively large
pore structure and the absorbent core which has a relatively small
pore structure, which gradient promotes rapid transmission of body
fluids into the absorbent core material, thereby minimizing lateral
spreading of body fluids deposited on the top sheet. This permits
more effective utilization of the absorptive capacity of the
absorbent core material, and prevents migration of body fluids
absorbed by the absorbent core material back through the surface of
the topsheet, thereby retaining absorbed body fluids within an
envelope formed by the waterproof backing sheet adjacent its
lowermost surface and the top sheet which overwraps its uppermost
surface and its edge portions.
Inventors: |
Duncan; Robert C. (Wyoming,
OH), Smith; Grace L. (Cincinnati, OH) |
Assignee: |
The Procter & Gamble
Company (Cincinnati, OH)
|
Family
ID: |
23347610 |
Appl.
No.: |
05/343,774 |
Filed: |
March 22, 1973 |
Current U.S.
Class: |
604/372; 604/375;
604/383; 604/379 |
Current CPC
Class: |
A61F
13/51305 (20130101); A61F 13/47245 (20130101); A61F
13/51121 (20130101); A61F 13/64 (20130101); A61F
13/5605 (20130101); A61F 13/513 (20130101); A61F
2013/53445 (20130101); A61F 2013/15365 (20130101); A61F
2013/5694 (20130101); A61F 2013/530802 (20130101); A61F
2013/51078 (20130101); A61F 13/534 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61F 13/64 (20060101); A61F
13/56 (20060101); A61f 013/16 () |
Field of
Search: |
;128/29R,29W,29P,29H,296,284,286,287 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Laudenslager; Lucie H.
Attorney, Agent or Firm: Linman; E. Kelly Braun; Frederick
H. Gorman; John V.
Claims
What is claimed is:
1. An absorbent bandage, comprising:
a. a hydrophilic absorbent core of compressed absorbent material
having a density throughout of from about 0.15 to about 0.30 gm.
per cubic centimeter as measured under a load of 50 gm. per square
inch, a 0.05 - 0.06 in. thick by 1.50 in. wide specimen of said
absorbent core material having a Taber softness between about 1.2
and about 8.7 gram-centimeters;
b. a hydrophobic topsheet having a density substantially less than
that of said absorbent core secured in superposed relation to said
absorbent core, said absorbent core and said topsheet comprising an
absorbent pad for rapidly absorbing and retaining body exudate;
and
c. a bottom sheet underlying and secured to said absorbent pad for
supporting said absorbent pad in-use.
2. The absorbent bandage of claim 1, including a thin, flexible
backsheet of waterproof material underlying and co-extensive with
said absorbent core and located intermediate with said absorbent
core and said bottom sheet, said waterproof backsheet thereby
preventing strike-through of body exudate absorbed by said
absorbent core to the lowermost surface of said bandage.
3. The absorbent bandage of claim 1, wherein the lowermost surface
of said hydrophilic absorbent core is completely overwrapped by the
overlapping portions of said hydrophobic topsheet, thereby
preventing strike-through of body exudate absorbed by said
sbsorbent core to the lowermost surface of said bandage.
4. The absorbent bandage of claim 1, wherein said hydrophilic
absorbent core is comprised of compressed airfelt.
5. The absorbent bandage of claim 4, wherein the exterior surfaces
of the airfelt have been treated with a wet-strengthening agent
prior to initial compression to bond the surface fibers of the
airfelt together at contact points.
6. The absorbent bandage of claim 1, wherein said hydrophobic
topsheet is comprised of non-woven, needle-punched polyester fabric
having a density of from about 0.03 to about 0.13 gm. per cubic
centimeter as measured under a load of 50 gm. per square inch.
7. The absorbent bandage of claim 1, wherein said bottom sheet is
comprised of hydrophobic, spunbonded, low basis weight, non-woven
polyester fabric.
8. An absorbent bandage suitable for use as a catamenial or an
incontinent device, comprising:
a. an absorbent pad having reduced overall width toward its
rearwardmost portion;
b. a bottom sheet underlying and secured to said absorbent pad,
said bottom sheet having forward and rearward extensions projecting
substantially beyond said absorbent pad for supporting said
absorbent pad in-use;
c. longitudinally extending means in said absorbent pad for
imparting an upwardly concave bias to said absorbent pad in the
transverse direction; and
d. a discontinuity in the forward extension of said bottom sheet
proximate to the forward edge of said absorbent pad and
transversely oriented to the longitudinal axis of said absorbent
bandage to concentrate normal in-use tensile forces applied to said
forward and rearward bottom sheet extensions along the lateral edge
portions of said absorbent pad, said concentration of tensile
forces in cooperation with the reduced overall width of the
rearwardmost portion of said absorbent pad and the aforesaid
longitudinally extending means for imparting bias causing said
absorbent pad to assume an upwardly concave conformation in both
the longitudinal and the transverse directions to prevent run-off
and smearing of body exudate deposited on the uppermost surface of
said bandage.
9. The absorbent bandage of claim 8, wherein said longitudinally
extending means for imparting an upwardly concave bias to said
absorbent pad is comprised of a longitudinally extending depression
of relatively narrow width, said depression being centrally-located
in the uppermost surface of said absorbent pad.
10. The absorbent bandage of claim 8, wherein said discontinuity in
the forward extension of said bottom sheet is comprised of a slit
located intermediate the lateral edge portions of said forward
extension, said slit being transversely oriented to the
longitudinal axis of said absorbent bandage.
11. An absorbent bandage suitable for use as a catamenial or an
incontinent device, comprising:
a an absorbent pad having reduced overall width toward its
rearwardmost portion, said absorbent pad being comprised of a
hydrophilic absorbent core of compressed absorbent material having
a density of from about 0.15 to about 0.30 grams per cubic
centimeter as measured under a load of 50 gm. per square inch, a
0.05 - 0.06 in. thick by 1.50 in. wide specimen of said absorbent
core material having a Taber softness between about 1.2 and about
8.7 gram-centimeters, and a hydrophobic topsheet secured in
superposed relation to said absorbent core, said topsheet having a
density of from about 0.03 to about 0.13 gm. per cubic centimeter
as measured under a load of 50 gm. per square inch;
b. a bottom sheet underlying and secured to said absorbent pad,
said bottom sheet having forward and rearward extensions projecting
substantially beyond said absorbent pad for supporting said
absorbent pad in-use;
c. longitudinally extending means in said absorbent pad for
imparting an upwardly concave bias to said absorbent pad in the
transverse direction; and
d. a discontinuity in the forward extension of said bottom sheet
proximate to the forward edge of said absorbent pad, whereby normal
in-use tension on said forward and rearward bottom sheet extensions
in cooperation with the reduced overall width of the rearwardmost
portion of said absorbent pad and the aforesaid longitudinally
extending means for imparting bias causes said absorbent pad to
assume an upwardly concave conformation in both the longitudinal
and the transverse directions to prevent run-off and smearing of
body exudate deposited on the uppermost surface of said
bandage.
12. The absorbent bandage of claim 11, wherein said longitudinally
extending means for imparting an upwardly concave bias to said
absorbent pad is comprised of a centrally-located, longitudinally
extending slit in the lowermost surface of said absorbent core.
13. An absorbent bandage suitable for use as a catamenial or an
incontinent device, comprising an absorbent pad having a main body
portion and a forward extension, said forward extension being of
lesser bulk than said main body portion, and a bottom sheet having
forward and rearward extensions projecting substantially beyond
said absorbent pad underlying and secured to said main body portion
but not to said forward extension, the forward extension of said
absorbent pad being free to bend relative to said bottom sheet and
to the main body portion of said absorbent pad, whereby normal
in-use tension on said forwardand forward and bottom sheet
extensions causes the forward extension of said absorbent pad to
bend upwardly relative to the main body portion to provide a dam
for restraining excessive forward flow of body exudate.
14. And absorbent bandage suitable for use as a catamenial or an
incontinent device, comprising an absorbent pad having a main body
portion and a forward extension, the main body portion of said
absorbent pad having reduced overall width toward its rearwardmost
end, and a bottom sheet having forward and rearward extensions
projecting substantially beyond said absorbent pad underlying and
secured to said main body portion, the forward extension of said
absorbent pad being free to bend relative to said bottom sheet and
to the main body portion of said absorbent pad, whereby normal
in-use tension on said forward and rearward bottom sheet extensions
causes the forward extension of said absorbent pad to bend upwardly
relative to the main body portion to provide a dam for restraining
excessive forward flow of body exudate, said absorbent bandage
including longitudinally extending means in said absorbent pad for
imparting an upwardly concave bias to said absorbent pad in the
transverse direction, and a transversely oriented discontinuity in
the forward extension of said bottom sheet proximate to the forward
edge of the main body portion of said absorbent pad, whereby normal
in-use tension on said forward and rearward bottom sheet extensions
in cooperation with the reduced overall width toward the
rearwardmost end of said absorbent pad and the aforesaid
longitudinally extending means for imparting bias causes said
absorbent pad to assume an upwardly concave conformation in both
the longitudinal and the transverse directions, thereby forming, in
cooperation with the forward extension of said absorbent pad, a
close-sided, cupped receptacle about the vulva for the collection
and retention of body exudate.
15. The absorbent bandage of claim 14, wherein said absorbent pad
has a maximum width of between about 2 inches and about 3 inches,
said width tapering to between about 1/2 inch and about 1 inch at
the rearwardmost end of the main body portion of said absorbent pad
and to between about 1/2 inch and about 1-1/2 inches at the
forwardmost end of the forward extension of said absorbent pad,
said absorbent pad having an overall length, including said forward
extension, of between about 6-1/2 inches and about 8-1/2
inches.
16. The absorbent bandage of claim 14, wherein said absorbent pad
is comprised of a hydrophilic absorbent core layer of compressed
absorbent material having a density throughout of from about 0.22
to about 0.26 gm. per cubic centimeter as measured under a load of
50 gm. per square inch, a 0.05 - 0.06 in. thick by 1.50 in. wide
specimen of said absorbent core material having a Taber softness
between about 1.2 and about 8.7 gram-centimeters, and a hydrophobic
topsheet secured in superposed relation to said absorbent core
layer, said topsheet having a density of from about 0.03 to about
0.08 gm. per cubic centimeter as measured under a load of 50 gm.
per square inch, said absorbent core layer and said topsheet
comprising both the main body portion and the forward extension of
said absorbent pad.
17. The absorbent bandage of claim 16, including a thin, flexible
backsheet of waterproof material underlying and coextensive with
said absorbent core layer, said backsheet being located
intermediate said absorbent core layer and said bottom sheet in the
area of the main body portion of said absorbent pad and
intermediate said absorbent core layer and the overlapping portions
of said topsheet in the area of the forward extension of said
absorbent pad, said waterproof backsheet thereby preventing
strike-through of body exudate absorbed by said absorbent core
layer to the lowermost surface of said bandage.
18. The absorbent bandage of claim 16, wherein said hydrophilic
absorbent core layer is comprised of compressed airfelt, said
hydrophobic topsheet is comprised of non-woven, needle-punched
polyester fabric, and said bottom sheet is comprised of
hydrophobic, spunbonded, low basis weight, non-woven, polyester
fabric.
Description
FIELD OF THE INVENTION
This invention relates to absorbent bandages, particularly sanitary
napkins, and more particularly to sanitary napkins or other
structures suitable for use either as a catamenial or an
incontinent device. In a preferred embodiment, the napkin will
assume an upwardly concave conformation when worn. In another
preferred embodiment, the napkin includes a forward extension of
the absorbent pad which is unrestrained and is hence free to bend
relative to the main body of the absorbent pad to form a seal
against the frontal portions of the body. In addition, this
invention has particular relation to absorbent bandages,
particularly sanitary napkins, wherein the absorbent core is
comprised preferably of a multiplicity of layers of relatively
dense, basically hydrophilic, compressed airfelt in contiguous
association with a waterproof backing sheet on its lowermost
surface and overwrapped on its uppermost surface and edge portions
by a top sheet of basically hydrophobic, non-woven, relatively low
density material to produce a favorable density gradient between
the top sheet and the absorbent core material. This in turn
promotes rapid transmission of menses or other discharged body
exudate into the absorbent core material, minimizes lateral
spreading of such body fluids on the topsheet, utilizes more
effectively the absorptive capacity of the absorbent core material,
and retains body fluids absorbed by the absorbent core material
within an envelope formed by the waterproof backing sheet and the
top sheet.
BACKGROUND OF THE INVENTION
Absorbent pads, and especially sanitary napkins, have been made in
a variety of shapes and have incorporated numerous structural
features in attempts to provide an article of such nature which
fulfills its absorbing function and which is also comfortable and
non-chafing when worn.
Sanitary napkins which are in common use generally have the shape
of a rectangular parallelepiped which is enclosed by a fluid
permeable cover which is elongated at both ends of the napkin to
provide attachment tabs intended to be attached to the clasps of a
sanitary belt at the front and rear of the wearer. Tensional forces
induced uniformly along the leading edge of the absorbent core by
attachment of such a napkin to a sanitary belt bend the ends of the
sanitary napkin upwardly in the longitudinal direction, while
lateral compressional forces in conjunction with the uniformly
induced tensional forces, particularly in the region rearward of
the vulva between the buttocks, bend the sides of the napkin
downwardly so that it forms a downwardly concave or an inverted
U-shape in order to conform to the contours of the female pubic
arch. Thus, body fluids deposited on the upper surface of the
downwardly concave transverse section have a natural tendency, due
to the shape of the structure, to run downwardly toward the lateral
edges of the pad, thereby promoting run-off and soiling of
undergarments. Such external forces applied to the napkin also tend
to produce irregular surfaces in the napkin, particularly along the
uppermost portions of its lateral edges, which generally take the
form of troughs, folds, triangles ridges, flutes, etc., thereby
preventing intimate contact between the napkin and the body of the
wearer in the area of the vulva where snug fit is most
important.
Such downwardly concave curvature also promotes slippage of such a
napkin and smearing. Slippage is relative movement between the
napkin and the trunk of the body of the wearer; smearing is the
soiling of parts of the body of the wearer adjacent the labia
majora, usually as a result of slippage.
Since most prior art sanitary napkins have absorbent pads which are
of uniform cross section at any point along their longitudinal
axis, greater tensional forces are required to cause such a pad to
assume an upwardly concave configuration in the longitudinal
direction to conform to the female anatomy, thereby producing
greater discomfort to the wearer. This is primarily due to
deformation of the external female organs coming in contact with
the uppermost surface of the pad. Such rectangular style napkins
are also uncomfortable to the wearer from the standpoint of
chafing, due to the fact that the lateral edges of the napkin
contact the inner portions of the thighs at a point where
considerable movement occurs relative to the trunk of the body, and
hence movement also occurs relative to the lateral edge portions of
the napkin. Movement of the thighs relative to the lateral edges of
the napkin causes irritating frictional forces to be exerted
against the inner portions of the thighs, and at the same time
tends to promote run-off from the lateral edge portions of the
napkin due to the fact that a seal is not maintained along such
lateral edge portions of the napkin in the area of the body where
body fluids are usually deposited.
In an attempt to eliminate the above problems, sanitary napkins
have been made from conventional overwrap and core materials with
rearward portions of reduced size to conform more nearly to the
configuration of the female anatomy in the area of the buttocks.
Such a reduction in size has usually been accomplished by reducing
the amount of absorbent material contained in the rearward end of
the napkin either by cutting away portions of the napkin along the
sides of the rearward portion or by forming the napkin initially
with less absorbent material in the rearward portion. Such
procedures have generally been satisfactory from the standpoint of
improved comfort. However, considerable sacrifice is made with
respect to providing an effective absorbing medium for the overall
performance of such a sanitary napkin due to the fact that very
poor fluid transfer characteristics are inherent in prior art
sanitary napkins, regardless of shape or size. This is due to the
fact that the fluid pervious overwrap material used in such napkins
is typically more dense than the core material, thus providing a
gradient of increasing capillary size in the direction of the core
material which tends to inhibit fluid transfer from the top sheet
to the absorbent core material.
An alternative approach to forming a sanitary napkin with a reduced
size in its rearward portion has been to provide a sanitary napkin
having a preformed arcuate configuration in the longitudinal
direction, thereby eliminating or at least greatly reducing the
tensional forces required to bend an initially flat sanitary napkin
into the desired in use configuration. Preforming a sanitary napkin
into an arcuate configuration eliminates the transverse ridges and
troughs which are normally formed in the uppermost surface when a
normally flat sanitary napkin is subjected to tension to force it
to conform to the female anatomy by attachment to a sanitary belt.
Elimination of these ridges and troughs is important because they
encourage the flow of body fluids deposited on the top sheet to the
sides of the napkin. This results in the soiling of undergarments
and consequent in-use failure of the napkin substantially before
the full utilization of its absorptive capacity. However, for a
sanitary napkin to obtain a preformed, arcuate configuration, it
has usually been necessary to build in stabilizing forces within
the napkin, itself. This is normally done by providing shrinkable
elements strategically placed within the sanitary napkin or by
having thermoplastic or thermosetting moldable elements
strategically distributed throughout the napkin which, upon
activation by heat or chemical treatment, are effective to draw the
sanitary napkin into the desired arcuate configuration, or which,
by placement into suitable molding forms, are effective to mold the
sanitary napkin into its desired configuration. Such processes,
however, are usually expensive, and sometimes have the effect of
substantially reducing the effective absorption characteristics of
the absorbent core, particularly where such napkins employ water
insoluble binders. Lack of absorptive capacity reduces potential
wearing time and increases the possibility of in-use failure. In
addition, such products are usually stiff and, therefore, must be
shaped precisely to fit the body to be comfortable.
In absorbent bandages, and particularly in sanitary napkins, it is
extremely desirable that the construction be such that any
discharged body fluids which strike the surface thereof be carried
to the interior of the pad as rapidly as possible to be distributed
evenly throughout the interior absorbent portion and retained
therein. If this is accomplished effectively, excessive spreading
of the fluid on the surface and eventually over the edges of the
pad is avoided.
In prior art sanitary napkins, the absorbent core material is
usually overwrapped by an outer pervious covering which may be
comprised from gauze, non-woven threads, non-woven fabric, or the
like. Because the absorbent core material in prior art napkins is
usually of considerably lower density than the top sheet material,
fluid deposited on the top sheet will not be rapidly transmitted
into the core, but rather will tend to spread laterally on the
surface of the top sheet, thereby producing an objectionable
appearance and feel, causing discomfort and promoting run-off and
soiling of undergarments. In addition, fluid absorbed in the core
material will tend to migrate back to the surface of the top sheet
due to the unfavorable density gradient existing between the top
sheet and the absorbent core material, thereby causing the top
sheet to feel moist.
OBJECTS OF THE INVENTION
It is an object of the present invention to obviate the above
problems.
It is a further object of the present invention to provide a low
density, basically hydrophobic top sheet in contiguous association
with a high density, basically hydrophilic absorbent core material
to promote more rapid transmission of fluids deposited on the top
sheet into the absorbent core material and to retain such absorbed
fluids in the absorbent core material due to the favorable
capillary size and liquid contact angle gradients which exist
between the top sheet and the absorbent core material, regardless
of whether the absorbent core material is in a dry or a moist
state.
It is a further object of the present invention to provide a
sanitary napkin which is more comfortable to wear due not only to
improvements in softness of the relatively dense absorbent core
material, but also to an overall reduction in size, particularly
toward the rearward portion of the absorbent pad, and to the
tendency of the absorbent pad to assume an upwardly concave or "U"
configuration in both the transverse and the longitudinal
directions when worn.
It is a further object of the present invention to provide a
forward extension of the absorbent pad which is capable of bending
relative to the main body of the absorbent pad so as to better
conform to the frontal portions of the female body, and thereby
form a dam over which body exudate cannot flow.
It is a further object of the present invention to prevent
strike-through of body exudate from the lowermost side of a
sanitary napkin of the present invention by providing a waterproof
backing sheet essentially coextensive with the lowermost layer of
absorbent core material.
SUMMARY OF THE INVENTION
According to the present invention, an absorbent bandage is
provided, preferably in the form of a sanitary napkin, which
utilizes more effectively the available absorbent core material
provided in the napkin by providing a favorable density gradient
between the top sheet and the absorbent core material. This in turn
results in corresponding gradients of capillary size and liquid
contact angle which cause exuded body fluids to preferentially pass
to and accumulate in the absorbent core of the napkin. A non-woven
hydrophobic top sheet material having a density range of from
approximately 0.03 to approximately 0.13 gm. per cubic centimeter
as measured under a load of 50 gm. per square inch and a
hydrophilic compressed absorbent core having a density range of
from approximately 0.15 to approximately 0.30 gm. per cubic
centimeter as measured under a load of 50 gm. per square inch is
contemplated in the present invention. Thus, fluid deposited on the
surface of the basically hydrophobic top sheet will transfer at a
considerably more rapid rate to the more dense compressed absorbent
core than is the case with prior art sanitary napkins. Since the
absorbent core in a preferred embodiment is basically hydrophilic,
it will absorb the moisture transmitted from the top sheet, while
the top sheet remains relatively dry.
In one preferred embodiment of the present invention, a sanitary
napkin is provided having reduced size, particularly toward the
rearward portion thereof, and which, when worn, assumes an upwardly
concave or U-configuration in both the transverse and the
longitudinal directions. This avoids deformation of the natural
contours of the body portions adjacent thereto. The lateral edges
portions of the absorbent pad of a sanitary napkin of the present
invention are accommodated in the vaults formed by the jointure of
each thigh and the adjacent labium majora, while the central
portion of the absorbent pad moves downwardly.
The absorbent pad, in one preferred embodiment, is constructed so
that it readily assumes an upwardly concave configuration in the
transverse direction. This is achieved by providing a longitudinal
depression along the central portion of the top surface of the
absorbent pad which tends to bias the pad into an upwardly concave
or "U" shape. Additionally, a transverse slit is provided
intermediate the lateral edges of the bottom sheet material at a
point in vertical alignment with the forwardmost edge of the main
body of the absorbent pad, i.e., that portion of the pad not
including the forwardmost extension thereof, thereby relieving the
central portion of the absorbent pad of stress when worn, and
concentrating the tensile stress induced by application of the
napkin to a sanitary belt along the lateral edge portions of the
absorbent pad.
In another embodiment, a structure is provided which prevents the
flow of discharged fluids over the leading edge of the napkin while
simultaneously providing better conformance of the frontal portions
of the napkin to the female body. This is provided by structuring
the lowermost layer of absorbent core material and the waterproof
backing sheet with forward projections extending beyond the main
body of the absorbent pad. The aforementioned projections are
overwrapped only by top sheet material. The front extension thus
formed is free to bend relative to the main body of the absorbent
pad, and allows the napkin to conform more readily to individual
body shape, thereby effectively forming a dam against the body.
The unique features described above when combined in a preferred
embodiment of the present invention result in a sanitary napkin
which is more comfortable to the wearer both in terms of fit and
dryness, which gives the wearer a greater feeling of security
against smearing, run-off and strike-through, and which can be worn
for longer periods of time due to more effective utilization of the
absorbent core material.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing
out and distinctly claiming the subject matter which is regarded as
the present invention, it is believed that the invention will be
better understood from the following description taken in
connection with the accompanying drawings, in which:
FIG. 1 is an exploded perspective view of a sanitary napkin which
is one preferred embodiment of the present invention, wherein the
individual components are depicted in their unassembled
relation;
FIG. 2 is a perspective view showing partial assembly of the
components illustrated in FIG. 1, and further depicting the manner
in which the top sheet is folded about the other assembled
components;
FIG. 3 is a perspective view of one preferred embodiment of a
completely assembled sanitary napkin made in accordance with the
present invention prior to use by a consumer;
FIG. 4 is a perspective view of one preferred embodiment of a
completely assembled sanitary napkin of the present invention shown
in its in-use configuration when attached to the clasps of a
sanitary belt or holder;
FIG. 5 is an enlarged transverse sectional view of one preferred
embodiment of a sanitary napkin of the present invention when
placed in use by a consumer, such sectional view being taken at
approximately the same point as section line 6--6 in FIG. 3;
and
FIG. 6 is an enlarged transverse sectional view of one preferred
embodiment of a completely assembled sanitary napkin of the present
invention taken along section line 6--6 in FIG. 3, showing the
napkin in its configuration prior to use.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, there is shown an exploded view of the
individual components of one embodiment of the absorbent bandage of
the present invention. It will become apparent as the description
proceeds that a sanitary napkin is a most preferred embodiment,
although it will be understood that other similar equivalent
articles, e.g., disposable diapers, incontinent pads and the like,
are within the broad scope of the invention. The components in FIG.
1 are shown in the same relative position in which they are
ultimately assembled.
The preferred construction of a sanitary napkin includes a top
sheet 1 which comes in contact with the user's skin. The top sheet
1 is preferably a non-woven material. Very good results have been
obtained in using a non-woven, needle-punched polyester material
having a density in the range of from about 0.03 to about 0.13 gm.
per cubic centimeter as measured under a load of 50 gm. per square
inch, preferably between approximately 0.03 and 0.08 gm. per cubic
centimeter. One such material which has proven highly satisfactory
in this service is a non-woven, 3 denier, 21/4 oz. per square yard,
needle-punched polyester fabric having a caliper of approximately
0.09 in. and a density of approximately 0.03 gm. per cubic
centimeter, such as is available from Troy Mills, Troy, New
Hampshire. While the above mentioned needle-punched polyester
material is preferred, the invention can also be practiced with
similarly good results by the use of similar or equivalent
materials such as: a non-woven, 6 denier, needle-punched polyester
fabric having a caliper of approximately 0.11 in. and a density of
about 0.04 gm. per cubic centimeter, such as Troy Mills code No.
3001-007500 also available from Troy Mills, Troy, New Hampshire; a
non-woven, 6 denier, needle-punched Type 209 polyester fabric
having a caliper of either 0.08 in. or 0.09 in. and a density of
about 0.04 gm. per cubic centimeter, such as Stearns & Foster
grade "O" or grade "K" material available from The Stearns &
Foster Company, Lockland, Ohio; or a resin-bonded polyester fabric
having a caliper of approximately 0.014 in. and a density of about
0.13 gm. per cubic centimeter, such as Stearns & Foster grade
No. 2552 available from The Stearns & Foster Company, Lockland,
Ohio. The top sheet material exhibits hydrophobic properties in
that it does not readily absorb moisture which comes in contact
with it, but rather transmits it to the hydrophilic core layers 2
and 3 which absorb and distribute the moisture. The top sheet 1 has
front and rear extensions 6 and 13 and lateral extensions 7, 8, 9,
10, 11 and 12. A detailed description of how these extensions are
utilized to join the top sheet to the other components of the
sanitary napkin will be given following a more complete description
of the individual components.
The absorbent core is preferably comprised of a multiplicity of
layers of airfelt or equivalent materials, e.g., cellulose wadding,
rayon mat, etc. Preferably three layers of airfelt are utilized,
ordinarily two upper layers of basically hydrophilic compressed
airfelt 2, and a lowermost layer 3, the latter being of similar
configuration to the layers 2 except for the addition of a
trapezoidal extension 3a at its leading edge, i.e., its forward
portion 3a as shown in FIGS. 1 and 2. By compressing the airfelt in
this particular application, the density of the core material can
be increased from approximately 0.04 gm. per cubic centimeter as
measured under a load of 50 gm. per square inch to something in the
range of approximately 0.15 to approximately 0.30 gm. per cubic
centimeter as measured under the same load, preferably between
approximately 0.22 and 0.26 gm. per cubic centimeter, thus
producing a very favorable density gradient with respect to the low
density top sheet 1.
Immediately following dry compression, the densified airfelt in a
preferred embodiment may be subjected to any one of a number of
processes designed to provide acceptable lateral softness in the
finished product, e.g., mechanical microcreping carried out between
differentially loaded rubber belts and/or a differentially loaded
rubber belt and a hard surface. Such a process imparts softness and
compliance to the airfelt, which would not otherwise result if only
dry compression were utilized. A test designed to measure the
flexual rigidity or stiffness of paperboard, which utilizes a Taber
V-5 Stiffness Tester, Model 150 B, as manufactured by the Taber
Instrument Corporation of North Tonawanda, New York, can also be
used to measure the flexural rigidity or stiffness of the absorbent
core material, in this case compressed airfelt, by determining the
bending moment in gram-centimeters necessary to deflect the free
end of a 3.81 cm. (1.5 in.) wide vertically clamped specimen of
compressed airfelt having an overall length of 6.99 cm. (2.75 in.)
15.degree. from its center line when the load is applied 5
centimeters away from the clamp. Compressed airfelt having a
caliper of between 0.127 and 0.152 cm. (0.05 and 0.06 in.) such as
is used in the absorbent core of a preferred embodiment of the
present invention typically exhibits a softness range between 1.2
and 8.7 gram-centimeters, whereas compressed airfelt of equivalent
caliper which has not been subjected to any type of process to
impart softness after dry compression typically exhibits a softness
range between 10 and 18 gram-centimeters. The use of compressed
airfelt in this particular application allows the pad size to be
kept to a minimum, i.e, the caliper of a layer of uncompressed
airfelt is typically reduced from approximately 0.35 in. as
measured under a load of 50 gm. per square inch to approximately
0.09 in. to 0.10 in. under the same load after dry compression and
trimming to the preferred size, thereby permitting maximum use of
absorbent material. In addition, pre-compressing the airfelt prior
to assembly of a napkin of the present invention provides a
mechanism by which the airfelt is able to absorb greater quantities
of fluid, since the airfelt will tend to expand back toward its
original uncompressed state when it absorbs liquid. While in a
preferred structure the absorbent core comprises three layers,
e.g., the layers 2, 2 and 3, it will be understood that it is
possible to make the absorbent core from any number of layers,
i.e., one or more layers, depending upon the desired construction
of the finished product.
The waterproof backing sheet 4 can be of any pliable waterproof
material. One such material which has proven satisfactory in this
service is embossed hard polyethylene having an embossed caliper of
approximately 2.3 mils, such as is available from Visqueen Division
of Ethyl Corporation, Terre Haute, Indiana. The waterproof backing
sheet 4 is essentially coextensive with the lowermost layer of
absorbent core material 3. The primary purpose of the waterproof
backing sheet 4 is to prevent strike-through of absorbed body
fluids from the absorbent core of the pad to the lowermost surfaces
of the napkin. In one alternate embodiment of a sanitary napkin of
the present invention, the waterproof backing sheet 4 might be
perforated by a series of apertures designed to permit air
circulation through the lower portions of the pad to the interior
surfaces which are in contiguous association with the wearer's
skin. In yet another alternate embodiment of a sanitary napkin of
the present invention, the waterproof backing sheet 4 might be
eliminated altogether. However, in the event waterproof backing
sheet 4 is either perforated or entirely eliminated, it would be
necessary to extend top sheet lateral extensions 9, 10, 11 and 12
to overlap each other on the lower side of the napkin so as to
preclude strike-through of body exudate from the top sheet 1,
through the absorbent core layers 2 and 3, and ultimately through
the bottom of the napkin.
The bottom sheet 5 is preferably formed from two superposed
rectangular strips of material having approximate dimensions of 3
in. wide by 18 in. long in one preferred embodiment of the present
invention. Reemay, a basically hydrophobic, spunbonded, low basis
weight, non-woven, polyester fabric having a measured weight of
about 0.4 oz. per square yard, such as is available from E. I. Du
Pont De Nemours & Co., Inc., Wilmington, Delaware, has been
found to produce very satisfactory results in this service. Two
sheets of the above described Reemay are used in a preferred
embodiment to provide sufficient tensile strength. However, a
single sheet of heavier Reemay or other similar material having a
higher degree of tensile strength might also be used for this
purpose. Other materials having equivalent porosity, weight and
strength and could also be employed to produce comparable results.
Some specific examples include: Cerex, a spunbonded, non-woven
nylon available from Monsanto Company, St. Louis, Missouri; Typar,
a spunbonded, non-woven polypropylene available from E. I. Du Pont
De Nemours & Co., Inc., Wilmington, Delaware; Tyvek, a
spunbonded, non-woven polyethylene available from E. I. Du Pont De
Nemours & Co., Inc., Wilmington, Delaware; and an acrylic,
resin-bonded, carded, non-woven polyester such as Stearns &
Foster grade No. 2551 available from The Stearns & Foster
Company, Lockland, Ohio. As will be pointed out, this material is
not used as an overwrap in the true sense. Its purpose is to
provide a carrier means for the absorbent core layers 2 and 3, the
waterproof backing sheet 4, and the top sheet 1. The end extensions
of the bottom sheet 5 provide tab material as a means of attachment
to a sanitary belt such that the napkin is caused to assume an
upwardly concave conformation in both the longitudinal and the
transverse directions, thus providing better conformance to the
female anatomy in the area of the vulva.
Referring now to FIG. 2, the method of assembly of the components
depicted in FIG. 1 is more clearly illustrated. The absorbent core
member is formed by superposing the lowermost layer of absorbent
core material 3 over the waterproof backing sheet 4, and then
superposing the remaining layers of absorbent core material 2 on
top of the lowermost absorbent core layer 3 in such a manner that
the rearward portions (the right end as viewed in FIG. 2) of all
the absorbent core layers and the waterproof backing sheet 4 are in
vertical alignment.
The bottom sheet 5 is prefolded upwardly by means of heat and
pressure which tends to bond the superposed sheets together and to
form lateral tabs 15 and 16 at the leading edge of the napkin,
lateral tabs 17 and 18 adjacent the parallel lateral edges of
absorbent core layers 2 and 3, and lateral tabs 19 and 20 adjacent
the tapered lateral edges at the rearward portion of absorbent core
layers 2 and 3.
In order to provide a means of attachment at the rear of a sanitary
napkin of the present invention, two slits 21 are made extending
from the lateral edge portions of tabs 19 and 20 of the bottom
sheet 5, substantially perpendicular to the longitudinal axis of
the napkin. Each slit 21 penetrates the bottom panel 22 of the
bottom sheet material 5 to a distance within approximately 1/4 in.
to 1/2 in. of the longitudinal axis of the napkin. From the
position of those portions of tabs 19 and 20 which form the
extension rearward of slits 21, as illustrated in FIG. 2, one
additional fold is made from each side of the said rearward
extension. Each additional fold line (designated 29 in FIG. 2) runs
from the inwardmost edge of each lateral slit 21 to a point
approximately one-third of the way in from the corresponding
lateral edge as measured at the rearwardmost edge of the rearward
extension illustrated in FIG. 2. The result of these two additional
folds is a tab 24 which tapers in width from front to back from
approximately 1 in. to 1/2 in. at a point corresponding with slits
21 to approximately 1/2 in. to 1/4 in. at its rearwardmost portion,
as shown in FIG. 3. Heat and pressure are applied to bond the
series of overlapping folds forming the rearward attachment tab 24
together.
The transverse slits 21 in one preferred embodiment of the present
invention are in vertical alignment with a point approximately 1/2
in. to 11/2 in. from the rearwardmost edge of the tapered segment
of the absorbent core material. Although the exact location of
slits 21 is not critical, it is preferably forward from the
rearwardmost edge of the absorbent core material, since
overwrapping the juncture between the folded rearward tab 24 and
the unfolded portions of bottom panel 22 of the bottom sheet 5 with
overlapping tabs 11 and 12 of top sheet 1 imparts additional
strength to the rearward attachment tab 24.
With tabs 15, 16, 17, 18, and those portions of tabs 19 and 20
forward of slits 21 prefolded to assume an upwardly concave or
U-configuration in the transverse direction, the assemblage
comprised of the waterproof backing sheet 4, the lowermost layer of
absorbent core material 3, and preferably two layers of absorbent
core material 2, is placed within the trough-like structure formed
by the bottom sheet 5 such that the leading edges of absorbent core
layers 2 are in vertical alignment with a transverse slit 14 which
is made intermediate the lateral edge portions of bottom panel 22
of the bottom sheet 5 prior to insertion of the absorbent
material.
Tabs 17 and 18 of the bottom sheet 5 are folded over the absorbent
core assemblage so as to overlap by approximately 1/4 in. to 1/2
in. the parallel lateral edges of the uppermost layer of absorbent
core material 2. In similar fashion, those portions of tabs 19 and
20 forward of slits 21 overlap the uppermost layer of absorbent
core material 2 along its rearward lateral edges which are not
parallel to each other in such a manner that tabs 19 and 20 overlap
each other toward the rearward portion of the absorbent core. This
is illustrated in FIG. 2. Tabs 15 and 16 at the leading edge of the
bottom sheet 5 are folded inwardly, and heat and pressure are
applied so as to bond the overlapping tabs together to form a
forward extension 27, as shown in FIGS. 3 and 4, which serves as a
means of attachment to the front of a sanitary belt or holder.
The fold lines shown on the top sheet 1 in FIGS. 1 and 2 define a
shape identical to that of the lowermost absorbent core layer 3 and
the waterproof backing sheet 4. The top sheet 1 is joined to the
balance of the structure in such a manner that the shape defined by
the fold lines is in vertical alignment with the lowermost
absorbent core layer 3 and the waterproof backing sheet 4. Tabs 9
and 10 of the top sheet 1 are adjacent the parallel lateral edges
of absorbent core layers 2 and 3, while tabs 11 and 12 are adjacent
the non-parallel rearward lateral edges of absorbent core layers 2
and 3. Those portions of tabs 9, 10, 11 and 12 which overlap by
approximately 1/2 in.-3/4 in. the bottom panel 22 of the bottom
sheet material 5 are attached to the bottom surface thereof by
means of beads of glue 28, as shown in FIGS. 5 and 6. The
rearwardmost tab 13 of the top sheet 1 overlaps by approximately
1/2 in.-3/4 in. the rearwardmost end of absorbent core layers 2 and
3 and the lowermost surface of the waterproof backing sheet 4, and
is secured thereto by means of glue. Thus, the main body of the
absorbent core, i.e., absorbent core layers 2 and 3, excluding the
forward extension 3a of the lowermost absorbent core layer 3, is
secured to the bottom sheet material 5.
Triangular tabs 7 and 8 and rectangular tab 6 of top sheet 1 are
folded so as to totally enclose the forwardmost extension 3a of the
lowermost layer of absorbent core material 3 and the forwardmost
extension of the waterproof backing sheet 4. Rectangular tab 6 is
folded and glued to the waterproof backing sheet 4, followed by
triangular tabs 7 and 8 which are folded and glued to both the
rectangular tab 6 and those portions of waterproof backing sheet 4
which are exposed.
One glue which has proven satisfactory for use in assembling a
sanitary napkin of the present invention is ELVACE 1873, which is a
water-resistant glue available from E. I. Du Pont De Nemours &
Co., Inc., Wilmington, Delaware. Other water resistant glues having
similar properties could also be utilized.
Addition of the top sheet 1 as described above results in a
structure which places the top sheet in contiguous association not
only with the uppermost surface of the uppermost absorbent core
layer 2, but also with the uppermost surface of the forward
extension 3a of the lowermost absorbent core layer 3. Thus,
absorbent core layers 2 and 3 are totally enclosed either by top
sheet 1 or waterproof backing sheet 4.
In order to impart a bias to a napkin of the present invention to
assume an upwardly concave configuration in the transverse
direction when worn, a longitudinally extending depression 25 of
relatively narrow width is pressed into the central portion of the
main body of the absorbent pad 26 at the uppermost surface of the
top sheet 1 (see FIG. 3). This is done by placing a steel rod
approximately 31/2 inches long and 1/4 inch in diameter along the
horizontal axis of the napkin, and applying a force of
approximately 4,000 lb. uniformly along the length of the rod. The
central depression 25 in a preferred embodiment of the present
invention is essentially co-extensive with the lateral parallel
edges of absorbent core layers 2 and 3, as illustrated in FIG. 3.
However, said central depression 25 could be considerably shorter
than is illustrated in FIG. 3 or could extend nearly all the way
across the entire upper surface of the top sheet 1 in a
longitudinal direction.
In the alternative, an interrupted central depression or a series
of depressions parallel to the longitudinal axis of the napkin
could be used to accomplish the same result. Other means may also
be provided to impart the desired bias to the napkin such that it
will tend to assume an upwardly concave configuration. For example,
in place of the preferred depression 25, the upper core layer 2 may
be formed such that its longitudinal central area is of lesser
thickness. In still another form, the same advantages may be
imparted to the napkin by providing a longitudinal central slit in
the core layer 3, or in both the core layer 3 and the lowermost
core layer 2. These and other means for providing this function
will be apparent to those skilled in the art.
FIG. 3 represents a preferred embodiment of a completely assembled
sanitary napkin of the present invention prior to use. The bias to
assume an upwardly concave configuration in the transverse
direction prior to use due to the longitudinal central depression
is clearly illustrated in FIG. 6, which is a transverse sectional
view taken along section line 6--6 of FIG. 3. The central
depression 25 also has the effect of densifying the absorbent core
material in the immediate vicinity of the depression, thereby
making the density gradient most favorable in the area where body
fluids are most likely to be initially deposited.
FIG. 6 illustrates the manner in which the various components of a
preferred embodiment of the instant invention are held in
contiguous association. The absorbent core layers 2 and 3 and the
waterproof backing sheet 4 are merely stacked one upon the other.
The bottom sheet material 5 is provided with tabs 17 and 18 at its
lateral edges at this particular transverse section, the outermost
portions of which overlap the uppermost surface of the uppermost
layer of absorbent core material 2. With the exception of a few
drops of glue which may be applied to hold the bottom sheet
material 5 in place while the top sheet 1 is being added, the
overlapping portions of tabs 17 and 18 and the overlapping portions
of tabs 19 and 20 forward of transverse slits 21 are held in place
merely by a sandwiching effect between the top sheet 1 and the
uppermost layer of absorbent core material 2.
A sanitary napkin of the present invention exhibits improvements
not only in terms of comfort to the wearer, but also in terms of
the efficiency with which the napkin is able to retain and absorb
body exudate, while at the same time preventing strike-through, and
minimizing the possibility of run-off, slippage and smearing. A
sanitary napkin of the present invention has a width at its widest
point ranging from approximately 2 to 3 inches, most desirably
approximately 2-1/4 inches. The rearward portion of such a napkin
is generally tapered from the maximum width to a dimension ranging
from approximately 1/2 to 1-1/2 inches, most desirable
approximately 1 inch. The forward extension 23 of the absorbent pad
of a napkin of the present invention tapers from the maximum width
to a dimension ranging between 1/2 and 1-1/2 inches, most desirably
approximately 1 inch. The overall length of the napkin along its
longitudinal axis, exclusive of its attachment tabs, typically
ranges between approximately 6-1/2 and 8-1/2 inches, most desirably
approximately 7-1/2 inches. The longitudinal distance over which
the rearward taper of the absorbent pad 26 occurs ranges between
approximately 3 and 4 inches, most desirably approximately 3-1/2
inches. The longitudinal distance over which the forward taper of
the forward extension 23 of the absorbent pad occurs is in the
range of approximately 1/2 to 1-1/2 inches, most desirably
approximately 1 inch. The forward attachment tab 27 typically
ranges between approximately 3-1/2 and 5-1/2 inches in length, most
desirably about 4-1/2 inches as measured from the leading edge of
the main body of the absorbent pad 26, i.e., that portion of the
absorbent pad not including the forwardmost extension 23 thereof.
The rearward attachment tab 24 typically ranges between
approximately 5-1/2 and 7-1/2 inches in length, most desirably
about 6-1/2 inches as measured from the rearwardmost edge of the
main body of the absorbent pad 26.
It is recognized that although only one preferred embodiment of the
present invention has been described above, a sanitary napkin
having an elliptical or any other equivalent configuration of the
same general proportions as those listed above could be utilized to
effect a similar result.
It will be noted from FIG. 4 that a napkin of the present invention
is intended to be worn with its wider portion toward the front of
the body, with the forwardmost extension 23, which is free to bend
relative to the main body of the absorbent pad, to a considerably
higher elevation than the main body of the absorbent pad 26.
A sanitary napkin of the present invention has been found to have
better conformation to the female anatomy. Its tapered rearward
portion is sufficiently narrow to avoid bunching in the anal area,
while its maximum width is such that the lateral edge portions of
the absorbent pad contact the null point of the groin line, i.e.,
where there is virtually no movement of the thighs relative to the
trunk of the body. Each lateral edge portion of the absorbent pad
is accommodated in a vault formed by the juncture of each thigh and
the adjacent labium majora, such that relative motion between the
inner portions of the thigh and each lateral edge portion of the
absorbent pad is essentially non-existent. This is best illustrated
in FIG. 5, which is an enlarged transverse sectional view of such a
napkin when placed in use. Thus, the size and shape of a sanitary
napkin of the present invention acting in conjunction with the
other structural features of the present invention eliminate the
downwardly concave or inverted "U" transverse configuration which
is normally assumed by prior art rectangular style sanitary
napkins, thereby minimizing the possibility of run-off of body
exudate.
It should be noted that the overall reduction in size of the
absorbent pad of a sanitary napkin of the present invention,
particularly toward its rearward portion, would not be practical
without the unique ability of the top sheet 1 and absorbent core
layers 2 and 3 of the present invention to rapidly transmit and
absorb body exudate much more effectively than is possible with
conventional overwrap and core materials due to the favorable
density gradient existing between the top sheet 1 and the absorbent
core layers 2 and 3. The favorable density gradient in turn
provides a diminishing capillary size gradient and a favorable
liquid contact angle gradient, both of which exist regardless of
whether the absorbent core material is in a moist or a dry
state.
In the present invention, stress on the central portion of the main
body of the absorbent pad 26 is relieved by means of a transverse
slit 14 or other similar interruption in the bottom sheet material
5. The transverse discontinuity or slit 14 in the bottom sheet
material 5 is located in bottom panel 22 intermediate the lateral
edges of the forward attaching tab 27, which is shown in FIGS. 3
and 4. The transverse interruption or slit 14 is preferably in
vertical alignment with the leading edge of absorbent core layers
2, i.e., with the leading edge of the main body of the absorbent
pad 26. The slit 14 may also be as much as 1 inch from the
aforesaid vertical alignment to achieve the objects of the
invention. The transverse interruption or slit 14 functions to
transmit stress imposed by tension on the attachment tabs 27 and
24, during wearing, to the lateral edges of the absorbent pad 26.
Selective placement of the tensional stress at the lateral edges of
the absorbent pad tends to form the absorbent pad 26 into a cupped
receptacle for the collection of body exudate, since, as shown in
FIG. 5, the lateral edges of the core are held snugly against the
body in the vaults formed by the juncture of each thigh and the
adjacent labium majora, while the central portion of the absorbent
pad 26 along the longitudinal axis is free to move downwardly,
thereby bridging the labia majora. The longitudinal depression 25
illustrated in FIGS. 3, 5 and 6 imparts a bias to the absorbent pad
26 which, when coupled with the forces induced by the tabs 27 and
24, tends to cause the longitudinal axis of the absorbent pad to
move downwardly. Thus, the cupping of the absorbent pad 26 is
caused principally by the addition of the slit 14 (which causes
selective application of stress from tabs 27 and 24) and is abetted
by the depression 25.
The present invention also discloses a sanitary napkin construction
in which a forward extension 23 of the absorbent pad 26 is formed
from the forwardmost extension 3a of the lowermost layer of
absorbent core material 3, the forwardmost extension of the
waterproof backing sheet 4, and the forwardmost extension of the
top sheet 1 which totally encloses the forwardmost extension 3a of
the lowermost absorbent core layer 3 and the forwardmost extension
of the waterproof backing sheet 4 by means of overlapping
rectangular tab 6 and overlapping triangular tabs 7 and 8. The
forward extension of the absorbent pad thus formed is free to bend
relative to the main body of the absorbent pad 26 along a line
corresponding with the leading edge of absorbent core layers 2.
This is due to the fact that the forward extension 23 is not in any
way confined by tabs 17 and 18 of the bottom sheet material 5, as
is the main body of the absorbent pad 26. In addition, since the
forward extension 23 is comprised of only one layer of absorbent
core material 3, the waterproof backing sheet 4, and the top sheet
1, very little effort is required to bend the forward extension 23
relative to the main body of the absorbent pad 26. The ability of
the forward extension 23 to bend with ease relative to the main
body of the absorbent pad 26 provides both improved fit and
comfort, since it causes the absorbent pad to assume an upwardly
concave or U-shape in the longitudinal direction with the
application of relatively small tensional forces.
The forward extension 23 also provides a capacity advantage when
worn, since it forms a dam to restrain the flow of body exudate
over the front of the napkin. In addition, because of the compliant
nature of the top sheet 1 and the fact that the forward extension
23 has less bulk than the main body of the absorbent pad 26, it is
more pliable and tends to conform to the female body with relative
ease, thereby minimizing the formation of any ridges or troughs
along its lateral edges. Elimination of ridges and troughs along
the lateral edges of a sanitary napkin is desirable because their
presence tends to promote the flow of body exudate toward the
lateral edges of the napkin, and hence increases the possibility of
run-off and consequent soiling of undergarments.
The front dam formed by the forward extension 23, cooperates when
worn with the transverse interruption or slit 14 in the bottom
sheet material 5 and the longitudinal depression 25 such that while
the lateral edges of the main body of the absorbent pad 26 are held
snugly against the body due to the tensional forces induced in the
lateral edge portions of the absorbent pad as a result of the slit,
the forward extension 23 conforms easily and hence forms a snug fit
against the frontal portions of the body, while the central
depression 25 causes the central portion of the main body of the
absorbent pad 26 to move downwardly to bridge the labia majora and
form a receptacle for the collection of menses or other body
exudate. Menses or other body exudate cannot readily escape toward
the rearward portion of the absorbent pad 26 due to the fact that
its rearwardmost edge is so narrow that the tensional forces along
the lateral edges of the main body of the absorbent pad intersect
at its rearwardmost portion, thereby forming a seal against the
body rearward of the vulva.
Thus a triangular shaped dam is formed about the periphery of the
vulva, while the central portion of the napkin is encouraged to
move downwardly, thus allowing it to form a totally enclosed
receptacle for the collection of menses or other body exudate.
Fluid deposited on the top sheet 1 is retained within the totally
enclosed receptacle so formed until it can be transmitted from the
topsheet 1 into the absorbent core layers 2 and 3. Run-off of
menses or other body exudate due to exceptionally heavy flow is
thereby minimized in any given direction.
Therefore, although a sanitary napkin of the present invention is
more comfortable to the wearer due to its reduced size, its revised
shape and its upwardly concave conformation in both the
longitudinal and the transverse directions to better fit the female
anatomy, it is also considerably more effective in retaining and
absorbing menses or other body exudate than a sanitary napkin of
conventional rectangular design having considerably more surface
area and absorbent core material present. It is also more effective
and more comfortable than sanitary napkins of the prior art having
tapered segments at their rearward portion, due to the unique
interaction of the transverse slit 14 in the bottom sheet material
5, the central longitudinal depression 25 in the main body of the
absorbent pad 26, and the forward extension of the absorbent pad 23
which cause the napkin to assume an upwardly concave conformation
in the area of the labia majora, thereby minimizing contact between
the top sheet 1 and the wearer's skin, and at the same time
minimizing the formation of ridges and troughs which are usually
formed along the lateral edges of a flat sanitary napkin when it is
attached to a sanitary belt or holder.
As has been mentioned earlier in this specification, the overall
reduction in size of the absorbent pad of a sanitary napkin of the
present invention to better fit the female anatomy would not be
practical unless the core material were more effectively utilized
to absorb menses or other body exudate than is the case with prior
art sanitary napkins. In sanitary napkin construction it is
generally desirable for the absorbent structure to immediately
accept body exudate, rapidly transport the exudate away from the
discharge source and effectively contain the exudate within the
confines of the napkin, while the top surface of the napkin is
maintained relatively dry. In addition, the absorbed exudate should
not be allowed to spread to the sides of the napkin, run over the
top edges of the napkin, or soak through the bottom of the napkin,
and this is especially true where the absorptive capacity of the
napkin has not been fully utilized.
As illustrated in FIGS. 1, 2, 5 and 6, a preferred embodiment of
the present invention consists of three layers of absorbent core
material, compressed airfelt in this instance, the lowermost layer
of which has a trapezoidal forward extension. The airfelt is
densified by dry compression and may be subjected to any one of a
number of processes designed to provide acceptable lateral softness
in the finished product, e.g., mechanical micro-creping carried out
between differentially loaded rubber belts and/or a differentially
loaded rubber belt and a hard surface. Dry compression increases
the airfelt's density by reducing its physical thickness, while any
one of the softening processes can be used to impart softness and
compliance which would not otherwise result if only dry compression
were utilized. The stiffness or flexural rigidity of a specimen of
compressed airfelt such as is utilized in a preferred embodiment of
the present invention having an overall width of 3.81 cm. (1.50
in.) and an overall length of 6.99 cm. (2.75 in.) can be measured
by means of a Taber V-5 Stiffness Tester, Model 150 B, as
manufactured by the Taber Instrument Corporation of North
Tonawanda, New York. A procedure identical to that utilized to
measure the stiffness or flexural rigidity of paperboard may be
utilized. The procedure involves determining the required bending
moment in gram-centimeters to deflect the free end of a 3.81 cm.
(1.50 in.) wide vertically clamped specimen as described above
15.degree. from its center line when the load is applied 5 cm. away
from the clamp. Compressed airfelt such as is used in a preferred
embodiment of the present invention having a caliper of between
0.127 and 0.152 cm. (0.05 and 0.06 in.) which has been subjected to
any of the softening processes well known in the art typically
exhibits a softness range between about 1.2 and 8.7
gram-centimeters, whereas compressed airfelt of equivalent caliper
which has not been subjected to any type of softening process
typically exhibits a softness range between 10 and 18
gram-centimeters. It is to be understood that various thicknesses
of compressed airfelt could be utilized in the present invention.
However, the Taber softness range would differ for different
thicknesses of material and, therefore, the preferred Taber
softness range would have to be individually determined for any
given thickness of material.
In a sanitary napkin of the present invention having a total weight
of approximately 10 to 12 gm., the total weight of the absorbent
core material is typically in the range of approximately 7 to 8 gm.
A preferred embodiment of the present invention has the machine
direction of the compressed airfelt aligned transverse to the
longitudinal axis of the napkin. However, there does not appear to
be a discernible difference in the characteristics of the finished
product when the machine direction of the airfelt is aligned
parallel to the longitudinal axis of the napkin.
If desired, a resin spray (e.g., Rohm and Haas HA-8) or other
bonding agent may be applied to the exterior surfaces of absorbent
layers 2 and 3 while they are still at low density, i.e., prior to
compression, to reduce the tendency of the airfelt to shred and
tear when dry and ball up and rope when wet and to improve the
surface dryness. However, since a sanitary napkin of the present
invention experiences virtually no relative movement with respect
to itself or with respect to the trunk of the body or the inner
portions of the thighs, this is not essential to the practice of
the invention.
Such a strength imparting treatment would be of greatest benefit in
absorbent bandages which experience considerable internal movement
and shifting, such as disposable diapers, etc. Bonding of the
exterior surfaces of the absorbent core members to impart both
tensile and cohesive strength could be carried out to impart wet
strength to the airfelt by bonding the surface fibers together at
contact points.
In a preferred embodiment of the present invention, the top sheet 1
is in contiguous association with the uppermost surface of the
uppermost layer of absorbent core material 2 and the uppermost
surface of the forward extension 3a of absorbent core layer 3. All
the absorbent core layers are in contiguous association with each
other, while the lowermost surface of the lowermost absorbent core
layer 3 is in contiguous association with the waterproof backing
sheet 4. Due to the hydrophobic nature and the low density of the
top sheet 1 in a preferred embodiment of the present invention,
fluid deposited on the top sheet migrates rapidly towards the more
dense absorbent core layers 2 and 3 which are basically
hydrophilic, rather than spreading laterally across the surface of
the top sheet 1. The rapid transmission of fluid caused by
capillary attraction keeps the top sheet feeling dry, and,
therefore, more comfortable to the wearer. When the uppermost
absorbent core layer 2 makes contact with the fluid, it begins to
absorb the fluid and its lattice structure begins to expand,
particularly in the area of the longitudinal depression 25. As the
pore size in the wetted portion of the absorbent core increases, it
creates a favorable density gradient between the moist and dry
segments of absorbent core layers 2 and 3. Thus fluid is rapidly
transmitted not only from one layer to the next, but also toward
the lateral edges of each layer of absorbent core material. Because
the density of the top sheet 1 remains basically unchanged due to
its hydrophobic nature, its pore size remains larger than the pore
size of even the moist layers of absorbent core material 2 and 3.
Therefore, fluid which has been absorbed by absorbent core layers 2
and 3 does not tend to migrate back towards the top sheet 1. Since
the absorbent core layers 2 and 3 are covered on their uppermost
and lateral edge portions by the basically hydrophobic top sheet 1,
and since the extensions of the hydrophobic top sheet 1 are bonded
to the lowermost side of either the bottom sheet material 5 or the
waterproof backing sheet 4, absorbed fluid is trapped within a
capsule-like member formed by the top sheet 1 and the waterproof
backing sheet 4. Thus, the top sheet 1 acts as a unidirectional
flow member which permits the flow of fluid only towards the
absorbent core layers 2 and 3 and not in the reverse direction. In
addition, since a sanitary napkin of the present invention is not
subjected to compressional forces by the inner portions of the
thighs of the wearer, there is virtually no tendency to force
absorbed fluids from the absorbent core layers 2 and 3 to the top
sheet 1 due to the application of pressure. This tends to promote
longer wearing times, since the top surface of the pad feels drier
and has a less objectionable appearance. Longer wearing times in
turn permit more effective utilization of the absorptive capacity
of absorbent core layers 2 and 3. The waterproof backing sheet 4,
meanwhile, gives the user confidence to wear the pad for longer
periods of time since she is protected against strike-through.
Many modifications of the above invention may be used and it is not
intended to hereby limit to the particular embodiments shown or
described. The terms used in describing the invention are used in
their descriptive sense and not as terms of limitation, it being
intended that all equivalents thereof be included within the scope
of the appended claims.
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