Title:
PRESHAPED FEMININE NAPKIN
United States Patent 3805790
Abstract:
A feminine napkin of predetermined shape, dimensioned to conform particularly well to the perineal area of the female body over a wide range of anatomical sizes. The defined shape and dimensions enables the napkin to automatically position itself properly with respect to the body when worn while at the same time providing improved comfort. In addition, the napkin is substantially non-discernible to the casual observer, even when worn in combination with tight-fitting garments. The napkin is also adapted for adhesive attachment to supporting garments.
US Patent References:
Preformed, arcuate sanitary napkins
Johnson, Jr. et al. - December 1960 - 2964039
Sanitary napkin and suspensory device therefor
Atkinson - October 1962 - 3059644
Diaper with film enclosed absorbent
Arnold et al. - October 1967 - 3344789
DIAPER RETAINING GARMENT
McConnell et al. - August 1969 - 3461872
DISPOSABLE PANTY SHIELD
Hendricks - August 1969 - 3463154
Preformed, arcuate sanitary napkins
Johnson, Jr. et al. - December 1960 - 2964039
Sanitary napkin and suspensory device therefor
Atkinson - October 1962 - 3059644
Diaper with film enclosed absorbent
Arnold et al. - October 1967 - 3344789
DIAPER RETAINING GARMENT
McConnell et al. - August 1969 - 3461872
DISPOSABLE PANTY SHIELD
Hendricks - August 1969 - 3463154
Inventors:
Kaczmarzyk, Leonard M. (Neenah, WI)
Skora, Robert F. (Neenah, WI)
Skora, Robert F. (Neenah, WI)
Application Number:
05/252599
Publication Date:
04/23/1974
Filing Date:
05/12/1972
View Patent Images:
Export Citation:
Assignee:
Kimberly-Clark Corporation (Neenah, WI)
Primary Class:
Other Classes:
604/378, D24/125, 604/370, 604/377, 604/387
International Classes:
A61F13/15; A61F13/56; A61F13/16
Field of Search:
128/284,285,286,287,290,296
US Patent References:
Primary Examiner:
Rosenbaum, Charles F.
Attorney, Agent or Firm:
Hanlon Jr., Daniel Herrick William Miller Raymond J. D. J.
Claims:
What is claimed is
1. An anatomy-conforming feminine napkin of predetermined shape and comprising a preshaped absorbent pad member, a fluid-pervious cover member, and a preformed fluid-impervious backing member; said preshaped pad member when viewed in plan comprising an elongate generally biconcave pad having a major and a minor axis, the sides of said pad flanking said major axis being generally and symmetrically concave, and said minor axis being disposed perpendicular to said major axis at the narrowest point of biconcavity; the dimension of said minor axis being in the range of about 1 1/4 inches to about 1 3/4 inches; said concave sides being defined by a curve the segments of which have a radius of curvature of no less than 2 inches and no more than 4 inches, said curve being perpendicular to said minor axis at its intersection therewith, and the length of the chord which subtends said curve being from about 2 1/2 inches to 5 inches; said impervious backing member comprising a preformed shallow basin into which said preshaped pad member is nested; the fluid pervious cover member being of the same contoured outline in plan view as said pad member to overlie the entire top surface of said pad member; said cover member being substantially planar; the peripheral edges of said cover member extending slightly beyond the edges of said pad member and being secured to the top periphery of the walls defining the shallow basin formed by said backing member.
2. The feminine napkin of claim 1 wherein said concave curve is the arc of a circle.
3. The feminine napkin of claim 1 wherein said concave curve is elliptical.
4. The feminine napkin of claim 1 wherein the end portions of said pad member disposed on either side of said minor axis are of unequal width and length, the narrower and shorter of said end portions defining the rear end of the pad as worn, and wherein said pad member is thickest at said minor axis tapering to thinner portions at each end, being feathered at one end while being about one-half of the minor axis thickness at the other end, said latter end being the rear of said pad as worn, and said feathered end being the front of said pad as worn.
5. The feminine napkin of claim 1 wherein said cover member comprises a non-woven web of hydrophobic fibers.
6. The feminine napkin of claim 5 wherein said cover member is provided with spaced perforations.
7. The feminine napkin of claim 1 wherein said preformed fluid impervious backing member comprises a thin plastic film.
8. The feminine napkin of claim 1 wherein said preformed fluid impervious backing member comprises a thin plastic foam.
9. The feminine napkin of claim 8 wherein at least the bottom surface of said foam is a closed skin.
10. The feminine napkin of claim 1 wherein said napkin is adapted to be removably attached to a supporting garment by having pressure sensitive adhesive means disposed on said fluid-impervious backing member.
1. An anatomy-conforming feminine napkin of predetermined shape and comprising a preshaped absorbent pad member, a fluid-pervious cover member, and a preformed fluid-impervious backing member; said preshaped pad member when viewed in plan comprising an elongate generally biconcave pad having a major and a minor axis, the sides of said pad flanking said major axis being generally and symmetrically concave, and said minor axis being disposed perpendicular to said major axis at the narrowest point of biconcavity; the dimension of said minor axis being in the range of about 1 1/4 inches to about 1 3/4 inches; said concave sides being defined by a curve the segments of which have a radius of curvature of no less than 2 inches and no more than 4 inches, said curve being perpendicular to said minor axis at its intersection therewith, and the length of the chord which subtends said curve being from about 2 1/2 inches to 5 inches; said impervious backing member comprising a preformed shallow basin into which said preshaped pad member is nested; the fluid pervious cover member being of the same contoured outline in plan view as said pad member to overlie the entire top surface of said pad member; said cover member being substantially planar; the peripheral edges of said cover member extending slightly beyond the edges of said pad member and being secured to the top periphery of the walls defining the shallow basin formed by said backing member.
2. The feminine napkin of claim 1 wherein said concave curve is the arc of a circle.
3. The feminine napkin of claim 1 wherein said concave curve is elliptical.
4. The feminine napkin of claim 1 wherein the end portions of said pad member disposed on either side of said minor axis are of unequal width and length, the narrower and shorter of said end portions defining the rear end of the pad as worn, and wherein said pad member is thickest at said minor axis tapering to thinner portions at each end, being feathered at one end while being about one-half of the minor axis thickness at the other end, said latter end being the rear of said pad as worn, and said feathered end being the front of said pad as worn.
5. The feminine napkin of claim 1 wherein said cover member comprises a non-woven web of hydrophobic fibers.
6. The feminine napkin of claim 5 wherein said cover member is provided with spaced perforations.
7. The feminine napkin of claim 1 wherein said preformed fluid impervious backing member comprises a thin plastic film.
8. The feminine napkin of claim 1 wherein said preformed fluid impervious backing member comprises a thin plastic foam.
9. The feminine napkin of claim 8 wherein at least the bottom surface of said foam is a closed skin.
10. The feminine napkin of claim 1 wherein said napkin is adapted to be removably attached to a supporting garment by having pressure sensitive adhesive means disposed on said fluid-impervious backing member.
Description:
BACKGROUND OF THE INVENTION
Feminine napkins presently used for catamenial protection comprise absorbent pad structures which for the most part are of elongate and substantially rectangular configuration. The market is provided with a large variety of such napkins in different lengths, widths, and thicknesses, each of which is designated as being suitable for a particular body size or shape, for heavy or light flows, or for different age needs. In addition to the more common rectangular form, there exists a limited selection of other geometric configurations also designed to meet particular body shapes or sizes.
As the result of an extensive anatomical study of the perineal area of subjects who fall in the various size groups it has now been found, rather surprisingly, that the dimensions of the female body in the area where catamenial protection devices are worn does not vary as much between groups as had been suspected. As a result it has been found possible to design an anatomy-conforming absorbent pad which, within certain critical dimensions, provides satisfactory absorptive protection for practically all body shapes and sizes. In addition, the improved pad was found to provide decreased bulk, and improved comfort and secrecy when worn, as compared to more conventional pads. The present invention is directed to an improved feminine napkin structure which provides the desirable characteristics enumerated above.
SUMMARY OF THE INVENTION
The improved feminine napkin of this invention comprises an absorbent pad of a predetermined, anatomy-conforming shape adapted to be removably attached to a supporting garment by adhesive means. The napkin is made of conventional materials, i.e., a highly absorbent core of fibrous material or the like, a fluid-pervious cover member, and a fluid-impervious pre-shaped backing member, preferably of thin plastic film, with pressure sensitive attachment means disposed thereon. The invention lies primarily in the anatomy-conforming shape of the pad and backing member, as well as the manner in which the component members are assembled. The shape of the anatomy-conforming pad when viewed in plan comprises an elongate, biconcave pad body in which the biconcavity lies along its major axis. The minor axis of the pad lies perpendicular to the major axis at the narrowest point of mutual concavity. The dimension of the minor axis and the concave curvature of the side edges are critical. The minor axis dimension is preferably 1/2, but may fall in the range of about 1 1/4 to about 1 3/4.
The dimensions of the curvature which provide the concavity of the pad body are also critical. These latter dimensions may be variable within a certain range but can be specifically defined in mathematical terms. A preferred shape for each of the concave arcs making up the side edges of the pad is a circular arc of about 3 1/4 radius, but may fall within a range of about 2 to 4. A preferred length of the chord which subtends the circular arc of the preferred radius is about 3 3/4, but may have a length of from about 2 1/2 to 5. Variations of these parameters within a range specified are permitted as further specified in the detailed description.
The length of the napkin is not critical, but preferably is from about 6 to 8. Larger sizes are not needed for the majority of users because, if larger, the utilization of the available absorbent capacity is grossly inefficient and is therefore wasteful and uneconomical. A pad dimensioned as described will automatically seat itself over the perineal area within the inner curvature of the wearer's thighs.
The ends of the pad body may be generally parallel and of equal width while being equally spaced from the minor axis. In the preferred form, the rear end portion of the pad is shorter and narrower than the front end portion. The pad is preferably thickest in section at the minor axis, and is tapered down toward each end. In the preferred form, the thickness of the rear end portion tapers less than the front end portion, and retains substantial thickness for improved absorption in that area.
In another important structural feature, the fluid-impervious backing member comprises a preformed shallow basin into which the preshaped pad body is snugly nested. The peripheral walls of the shallow basin thus are in contact with and extend around, the entire outer periphery of the pad body to provide an impervious fluid-holding container. The fluid-pervious cover member is of the same contour in plan view as the pad body to overlie the entire top surface of the pad body. The peripheral edges of the cover member are secured to the top edge of the backing member wall around the entire periphery thereof. The bottom face of the impervious backing member may have pressure sensitive adhesive means applied thereto and is covered by a protective strip. When this strip is removed, the adhesive serves as the means to attach the napkin to a suitable supporting garment.
Other features, objects and advantages will become apparent by reference to the detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective top view partly in section of a feminine napkin in accordance with one embodiment of the invention.
FIG. 2 is a plan view of a feminine napkin generally similar to the FIG. 1 embodiment.
FIG. 3 is a longitudinal section taken at line 3--3 of FIG. 2.
FIG. 4 is a bottom view of a feminine napkin in accordance with the FIG. 1 embodiment.
FIG. 5 is a perspective top view partly in section, and generally similar to FIG. 1, of another embodiment of the feminine napkin of the invention.
FIG. 6 schematically illustrates in plan the critical dimensions of a feminine napkin in accordance with the invention.
FIG. 7 schematically illustrates the parameters of the curves defining the concave sides of the napkin.
DETAILED DESCRIPTION OF THE INVENTION
In the preferred embodiments of the invention as shown in the accompanying drawings reference is made first to FIGS. 1-4 wherein there is shown an elongate feminine napkin 10 with symmetrically concave side edges 12 and 14. The biconcave napkin 10 is comprised of an absorbent pad body 16, enclosed within a preformed fluid-impervious backing member or baffle 18 which is formed into the shape of a shallow continuous-walled basin, and covered by a fluid pervious cover member 20.
Cover member 20, in plan view, is of the same biconcave contour as absorbent pad body 16. As shown, the edges of cover member 20 extend slightly beyond the entire periphery of pad body 16 and are secured to backing member 18 along the entire periphery of the backing member walls as indicated at 22.
In a preferred embodiment, feminine napkin 10 may have located on the bottom of backing member 18 a strip of pressure sensitive adhesive 24, or the like, covered by a protective release sheet 26. Sheet 26 may be removed to expose adhesive 24 for attachment to a suitable supporting garment. In instances where a tight-fitting undergarment is worn, of course, there is no need for the adhesive, since the close fit of the garment itself will hold the napkin tightly against the body, while the anatomical shape of the napkin, as shown, will be sufficient to maintain the preshaped feminine napkin in proper position longitudinally with respect to the perineal area.
As indicated earlier, the elements which make up feminine napkin 10 may consist of known conventional materials. Pervious cover member 20 may consist of a non-woven thread web, a bonded carded web of absorbent of non-absorbent staple fibers, or an autogeneously or otherwise bonded web of continuous filament synthetic fibers. Many variations of such materials are well known in the art. A preferred cover material is comprised of a hydrophobic, but fluid-permeable, autogeneously bonded web which, due to its hydrophobicity and one-way permeability when in contact with an absorbent pad body, helps provide the napkin with a desirable dry-feeling surface when in use. One embodiment of a preferred cover material is illustrated in FIG. 2 at 20a. As shown there, it is provided with a multiplicity of spaced perforations 21 to aid in rapid fluid penetration by menstrual exudate.
Absorbent pad body 16 may comprise natural absorbent cellulosic fibers such as wood pulp fluff, cotton, cotton linters, multi-layered cellulose wadding, or combinations thereof. It may also include regenerated cellulose fibers or sponge, staple rayon fibers, and various mixtures of absorbency-aiding materials, such as natural or synthetic gums, modified cellulose materials and the like.
While the absorbent pad body 16 may be of substantially uniform thickness throughout, it has been found that more efficient use per unit weight of the absorbent capacity is obtained by strategically locating the bulk of the absorbent material at the center and near the rear end portion of the pad. A preferred embodiment of such an arrangement is illustrated in the longitudinal section of FIG. 3. As noted by reference to that figure, the pad body is thickest in area 16 which is coincident with the transverse minor axis of the pad body. The absorbent material tapers down to about one-half this thickness at the rear end of the pad designated 17, and tapers down to a feathered edge at the front end of the pad 19. Most of the fluid absorbed in use is retained in the central and rear end portions of the pad. The feathered front end serves to preserve secrecy because of its inconspicuity when worn.
Fluid impervious backing member 18 is preferably a thin plastic film such as polyethylene or polypropylene of about 1/2 to 3 mils in thickness. Other thin flexible films such as polyvinyl chloride, polyvinylidene chloride, natural rubber, etc. may be employed. Another useful material is a thin polyurethane foam which may be of open or close-celled construction on the interior, and may be absorbent or nonabsorbent, but which should have a closed fluid-impervious skin or at least the bottom surface. An illustration of one embodiment of such foam is shown at 28 in FIG. 5.
As indicated in the summary of the invention, the anatomy-conforming shape of the feminine napkin and several of its key dimensions are particularly critical. FIGS. 6 and 7 schematically illustrate these dimensions.
The typical profile of a feminine napkin in accordance with this invention as represented by FIG. 6, has a rear end portion 31 and a front end portion 32. Line A--A is drawn through the longitudinal or major axis of the pad body. Line B--B is disposed at the narrowest point of biconcavity perpendicular to line A--A, and is drawn through the transverse or minor axis of the pad body. The dimension C on minor axis Line B--B indicates the narrowest area of biconcavity, and should have a dimension in the range of from 1 1/4 to 1 3/4, with 1 1/2 being preferred.
The preferred parameters for the curvature of the concave edges of the pad will now be described with reference to FIGS. 6 and 7.
The pad edges may be described as being minor-symmetrical about the major axis A--A. That is, given the shape of the pad edge on one side of the axis, the shape of the other pad edge may be obtained by folding or reflection about axis A--A. With this in mind, it will be sufficient to specify the edge of the pad on one side of A--A.
The critical area for the shape of the concave curvature lies between lines D--D and E--E. Line D--D is shown as being spaced distance a forward of minor axis B--B, and line E--E is shown as being spaced distance b rearward of B--B. The sum a+b also defines the length of the chord of the arc segment for the concave edge lying between D--D and E--E. Distances a and b are preferably each 1 7/8 in. However, the sum of a+b may range from 2 1/2 in. to 5 in.
Within this range, the preferred shape for the pad edge H--H (see FIG. 7) is a circular arc of radius 3 1/4in. It is noted that the reflected arc for H--H, G--G and F--F in FIG. 7 are indicated by a "prime" symbol. The center of curvature in this figure is of course fixed on axis B--B, at a distance 3 1/4 in. outward from the pad edge.
However, the inner aspect of the female thigh adjacent the perineal body is not a perfect arc, but an irregular curve which changes with body attitude and movement. Accordingly, it has been found that the concave edge H--H of FIG. 7 may be satisfactorily described by any smooth curve, always concave outward, whose radius of curvature is between 2 in. and 4 in. at every significant segment of the curve and which is perpendicular to the minor axis B--B at its intersection with B--B. Thus the center of curvature may shift as one moves along the curve. Where the curve intersects B--B, the center of curvature must lie on B--B, in order to make the curve perpendicular to B--B at that point; elsewhere on the curve, the center of curvature may shift continuously but smoothly, so that both the curve and its shape are continuous.
Thus, for example, a half-ellipse of major diameter 6.35 in., minor diameter 5.04 in., halved along its minor diameter and placed with its major diameter along B--B, would satisfy the criteria for the case where a and b are each less than 2.52 in. At its intersection with B--B, the ellipse would have its sharpest curvature with a radius of (2.52) 2 /3.175, or 2.0 in. The curvature of the ellipse gradually decreases as one moves away from B--B, but at the farthest conceivable reach, a distance 2.52 in. from B--B, the radius of curvature is (3.175) 2 /2.52 or 4.0 in.
The boundaries of all allowable curves will be the circular arc of radius 2 in., shown as F--F in FIG. 7, and the circular arc of radius 4 in., shown as G--G. The allowable curves, while not necessarily circles themselves, cannot turn outward any more rapidly than F--F nor any more slowly than G--G, since their radius at every point are between these limits.
It may be noted that these limits also prohibit any straight-line segments (radius of inifinity) and any sharp corners (radius = 0).
It is understood that C which defines the minor axis of the pad may have a dimension in the range of from about 1 1/4 inches to 1 3/4 inches and that the explanation of the relative curvature applies to any crotch structure within these preferred dimensions.
When various feminine napkins constructed within the ranges of the above-defined dimensions were tested in use, they were found to provide a desirable indexing function. That is, because the concave dimensions and narrow pad width at the minor axis conform so closely to average body measurements, when the pad is worn the narrow portion and associated curvature automatically maintain the pad in a properly indexed position with respect to the longitudinal axis, through all normal body movements.
In this respect, the feminine napkin, as described herein was found by the subjects who tested the pads to be superior in comfort and placement, when compared with the conventionally shaped pads described in the background section of this specification.
It was also found that because conventionally shaped pads tend to form longitudinal folds and to bunch together transversely when in contact with the narrow crotch area of the body, they were a source of some discomfort and early leakage. The latter characteristics were judged by subjects who tested various types of napkins to be minimized by the improved napkins described herein.
Another undesirable characteristic of conventionally shaped pads is the tendency for such pads to move forward or backward while being worn. As indicated above, this type of movement is largely overcome by the automatic indexing or positioning characteristics of the anatomically shaped napkin of the present invention.
Feminine napkins presently used for catamenial protection comprise absorbent pad structures which for the most part are of elongate and substantially rectangular configuration. The market is provided with a large variety of such napkins in different lengths, widths, and thicknesses, each of which is designated as being suitable for a particular body size or shape, for heavy or light flows, or for different age needs. In addition to the more common rectangular form, there exists a limited selection of other geometric configurations also designed to meet particular body shapes or sizes.
As the result of an extensive anatomical study of the perineal area of subjects who fall in the various size groups it has now been found, rather surprisingly, that the dimensions of the female body in the area where catamenial protection devices are worn does not vary as much between groups as had been suspected. As a result it has been found possible to design an anatomy-conforming absorbent pad which, within certain critical dimensions, provides satisfactory absorptive protection for practically all body shapes and sizes. In addition, the improved pad was found to provide decreased bulk, and improved comfort and secrecy when worn, as compared to more conventional pads. The present invention is directed to an improved feminine napkin structure which provides the desirable characteristics enumerated above.
SUMMARY OF THE INVENTION
The improved feminine napkin of this invention comprises an absorbent pad of a predetermined, anatomy-conforming shape adapted to be removably attached to a supporting garment by adhesive means. The napkin is made of conventional materials, i.e., a highly absorbent core of fibrous material or the like, a fluid-pervious cover member, and a fluid-impervious pre-shaped backing member, preferably of thin plastic film, with pressure sensitive attachment means disposed thereon. The invention lies primarily in the anatomy-conforming shape of the pad and backing member, as well as the manner in which the component members are assembled. The shape of the anatomy-conforming pad when viewed in plan comprises an elongate, biconcave pad body in which the biconcavity lies along its major axis. The minor axis of the pad lies perpendicular to the major axis at the narrowest point of mutual concavity. The dimension of the minor axis and the concave curvature of the side edges are critical. The minor axis dimension is preferably 1/2, but may fall in the range of about 1 1/4 to about 1 3/4.
The dimensions of the curvature which provide the concavity of the pad body are also critical. These latter dimensions may be variable within a certain range but can be specifically defined in mathematical terms. A preferred shape for each of the concave arcs making up the side edges of the pad is a circular arc of about 3 1/4 radius, but may fall within a range of about 2 to 4. A preferred length of the chord which subtends the circular arc of the preferred radius is about 3 3/4, but may have a length of from about 2 1/2 to 5. Variations of these parameters within a range specified are permitted as further specified in the detailed description.
The length of the napkin is not critical, but preferably is from about 6 to 8. Larger sizes are not needed for the majority of users because, if larger, the utilization of the available absorbent capacity is grossly inefficient and is therefore wasteful and uneconomical. A pad dimensioned as described will automatically seat itself over the perineal area within the inner curvature of the wearer's thighs.
The ends of the pad body may be generally parallel and of equal width while being equally spaced from the minor axis. In the preferred form, the rear end portion of the pad is shorter and narrower than the front end portion. The pad is preferably thickest in section at the minor axis, and is tapered down toward each end. In the preferred form, the thickness of the rear end portion tapers less than the front end portion, and retains substantial thickness for improved absorption in that area.
In another important structural feature, the fluid-impervious backing member comprises a preformed shallow basin into which the preshaped pad body is snugly nested. The peripheral walls of the shallow basin thus are in contact with and extend around, the entire outer periphery of the pad body to provide an impervious fluid-holding container. The fluid-pervious cover member is of the same contour in plan view as the pad body to overlie the entire top surface of the pad body. The peripheral edges of the cover member are secured to the top edge of the backing member wall around the entire periphery thereof. The bottom face of the impervious backing member may have pressure sensitive adhesive means applied thereto and is covered by a protective strip. When this strip is removed, the adhesive serves as the means to attach the napkin to a suitable supporting garment.
Other features, objects and advantages will become apparent by reference to the detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective top view partly in section of a feminine napkin in accordance with one embodiment of the invention.
FIG. 2 is a plan view of a feminine napkin generally similar to the FIG. 1 embodiment.
FIG. 3 is a longitudinal section taken at line 3--3 of FIG. 2.
FIG. 4 is a bottom view of a feminine napkin in accordance with the FIG. 1 embodiment.
FIG. 5 is a perspective top view partly in section, and generally similar to FIG. 1, of another embodiment of the feminine napkin of the invention.
FIG. 6 schematically illustrates in plan the critical dimensions of a feminine napkin in accordance with the invention.
FIG. 7 schematically illustrates the parameters of the curves defining the concave sides of the napkin.
DETAILED DESCRIPTION OF THE INVENTION
In the preferred embodiments of the invention as shown in the accompanying drawings reference is made first to FIGS. 1-4 wherein there is shown an elongate feminine napkin 10 with symmetrically concave side edges 12 and 14. The biconcave napkin 10 is comprised of an absorbent pad body 16, enclosed within a preformed fluid-impervious backing member or baffle 18 which is formed into the shape of a shallow continuous-walled basin, and covered by a fluid pervious cover member 20.
Cover member 20, in plan view, is of the same biconcave contour as absorbent pad body 16. As shown, the edges of cover member 20 extend slightly beyond the entire periphery of pad body 16 and are secured to backing member 18 along the entire periphery of the backing member walls as indicated at 22.
In a preferred embodiment, feminine napkin 10 may have located on the bottom of backing member 18 a strip of pressure sensitive adhesive 24, or the like, covered by a protective release sheet 26. Sheet 26 may be removed to expose adhesive 24 for attachment to a suitable supporting garment. In instances where a tight-fitting undergarment is worn, of course, there is no need for the adhesive, since the close fit of the garment itself will hold the napkin tightly against the body, while the anatomical shape of the napkin, as shown, will be sufficient to maintain the preshaped feminine napkin in proper position longitudinally with respect to the perineal area.
As indicated earlier, the elements which make up feminine napkin 10 may consist of known conventional materials. Pervious cover member 20 may consist of a non-woven thread web, a bonded carded web of absorbent of non-absorbent staple fibers, or an autogeneously or otherwise bonded web of continuous filament synthetic fibers. Many variations of such materials are well known in the art. A preferred cover material is comprised of a hydrophobic, but fluid-permeable, autogeneously bonded web which, due to its hydrophobicity and one-way permeability when in contact with an absorbent pad body, helps provide the napkin with a desirable dry-feeling surface when in use. One embodiment of a preferred cover material is illustrated in FIG. 2 at 20a. As shown there, it is provided with a multiplicity of spaced perforations 21 to aid in rapid fluid penetration by menstrual exudate.
Absorbent pad body 16 may comprise natural absorbent cellulosic fibers such as wood pulp fluff, cotton, cotton linters, multi-layered cellulose wadding, or combinations thereof. It may also include regenerated cellulose fibers or sponge, staple rayon fibers, and various mixtures of absorbency-aiding materials, such as natural or synthetic gums, modified cellulose materials and the like.
While the absorbent pad body 16 may be of substantially uniform thickness throughout, it has been found that more efficient use per unit weight of the absorbent capacity is obtained by strategically locating the bulk of the absorbent material at the center and near the rear end portion of the pad. A preferred embodiment of such an arrangement is illustrated in the longitudinal section of FIG. 3. As noted by reference to that figure, the pad body is thickest in area 16 which is coincident with the transverse minor axis of the pad body. The absorbent material tapers down to about one-half this thickness at the rear end of the pad designated 17, and tapers down to a feathered edge at the front end of the pad 19. Most of the fluid absorbed in use is retained in the central and rear end portions of the pad. The feathered front end serves to preserve secrecy because of its inconspicuity when worn.
Fluid impervious backing member 18 is preferably a thin plastic film such as polyethylene or polypropylene of about 1/2 to 3 mils in thickness. Other thin flexible films such as polyvinyl chloride, polyvinylidene chloride, natural rubber, etc. may be employed. Another useful material is a thin polyurethane foam which may be of open or close-celled construction on the interior, and may be absorbent or nonabsorbent, but which should have a closed fluid-impervious skin or at least the bottom surface. An illustration of one embodiment of such foam is shown at 28 in FIG. 5.
As indicated in the summary of the invention, the anatomy-conforming shape of the feminine napkin and several of its key dimensions are particularly critical. FIGS. 6 and 7 schematically illustrate these dimensions.
The typical profile of a feminine napkin in accordance with this invention as represented by FIG. 6, has a rear end portion 31 and a front end portion 32. Line A--A is drawn through the longitudinal or major axis of the pad body. Line B--B is disposed at the narrowest point of biconcavity perpendicular to line A--A, and is drawn through the transverse or minor axis of the pad body. The dimension C on minor axis Line B--B indicates the narrowest area of biconcavity, and should have a dimension in the range of from 1 1/4 to 1 3/4, with 1 1/2 being preferred.
The preferred parameters for the curvature of the concave edges of the pad will now be described with reference to FIGS. 6 and 7.
The pad edges may be described as being minor-symmetrical about the major axis A--A. That is, given the shape of the pad edge on one side of the axis, the shape of the other pad edge may be obtained by folding or reflection about axis A--A. With this in mind, it will be sufficient to specify the edge of the pad on one side of A--A.
The critical area for the shape of the concave curvature lies between lines D--D and E--E. Line D--D is shown as being spaced distance a forward of minor axis B--B, and line E--E is shown as being spaced distance b rearward of B--B. The sum a+b also defines the length of the chord of the arc segment for the concave edge lying between D--D and E--E. Distances a and b are preferably each 1 7/8 in. However, the sum of a+b may range from 2 1/2 in. to 5 in.
Within this range, the preferred shape for the pad edge H--H (see FIG. 7) is a circular arc of radius 3 1/4in. It is noted that the reflected arc for H--H, G--G and F--F in FIG. 7 are indicated by a "prime" symbol. The center of curvature in this figure is of course fixed on axis B--B, at a distance 3 1/4 in. outward from the pad edge.
However, the inner aspect of the female thigh adjacent the perineal body is not a perfect arc, but an irregular curve which changes with body attitude and movement. Accordingly, it has been found that the concave edge H--H of FIG. 7 may be satisfactorily described by any smooth curve, always concave outward, whose radius of curvature is between 2 in. and 4 in. at every significant segment of the curve and which is perpendicular to the minor axis B--B at its intersection with B--B. Thus the center of curvature may shift as one moves along the curve. Where the curve intersects B--B, the center of curvature must lie on B--B, in order to make the curve perpendicular to B--B at that point; elsewhere on the curve, the center of curvature may shift continuously but smoothly, so that both the curve and its shape are continuous.
Thus, for example, a half-ellipse of major diameter 6.35 in., minor diameter 5.04 in., halved along its minor diameter and placed with its major diameter along B--B, would satisfy the criteria for the case where a and b are each less than 2.52 in. At its intersection with B--B, the ellipse would have its sharpest curvature with a radius of (2.52) 2 /3.175, or 2.0 in. The curvature of the ellipse gradually decreases as one moves away from B--B, but at the farthest conceivable reach, a distance 2.52 in. from B--B, the radius of curvature is (3.175) 2 /2.52 or 4.0 in.
The boundaries of all allowable curves will be the circular arc of radius 2 in., shown as F--F in FIG. 7, and the circular arc of radius 4 in., shown as G--G. The allowable curves, while not necessarily circles themselves, cannot turn outward any more rapidly than F--F nor any more slowly than G--G, since their radius at every point are between these limits.
It may be noted that these limits also prohibit any straight-line segments (radius of inifinity) and any sharp corners (radius = 0).
It is understood that C which defines the minor axis of the pad may have a dimension in the range of from about 1 1/4 inches to 1 3/4 inches and that the explanation of the relative curvature applies to any crotch structure within these preferred dimensions.
When various feminine napkins constructed within the ranges of the above-defined dimensions were tested in use, they were found to provide a desirable indexing function. That is, because the concave dimensions and narrow pad width at the minor axis conform so closely to average body measurements, when the pad is worn the narrow portion and associated curvature automatically maintain the pad in a properly indexed position with respect to the longitudinal axis, through all normal body movements.
In this respect, the feminine napkin, as described herein was found by the subjects who tested the pads to be superior in comfort and placement, when compared with the conventionally shaped pads described in the background section of this specification.
It was also found that because conventionally shaped pads tend to form longitudinal folds and to bunch together transversely when in contact with the narrow crotch area of the body, they were a source of some discomfort and early leakage. The latter characteristics were judged by subjects who tested various types of napkins to be minimized by the improved napkins described herein.
Another undesirable characteristic of conventionally shaped pads is the tendency for such pads to move forward or backward while being worn. As indicated above, this type of movement is largely overcome by the automatic indexing or positioning characteristics of the anatomically shaped napkin of the present invention.