Hollow Foam Tampons From Flat Blanks

Abstract

Making a hollow deformable tampon by forming a tampon blank having a slit or separation between its top and bottom laminae, said laminae being attached around a substantial portion of their periphery leaving a large edge unattached. The blank can then be inverted, i.e., turned inside out, if required to bend the laminae to form an essentially circular tampon having a tensile stress on its exterior and a compressive stress on its interior.

Parent Case Text

This is a division of application Ser. No. 172,790, filed Aug. 18, 1971 and now abandoned.

Description

FIELD OF THE INVENTION

This invention relates generally to catamenial receptors intended to be worn within the vagina while receiving discharges and to a method for making this catamenial receptor.

DESCRIPTION OF THE PRIOR ART

Anatomy references teach that the vaginal passage is a pocket irregular in shape, rather than a cylindrical tube. It is about 3 to 4 inches long, shorter on its anterior wall and longer on the posterior wall. It is collapsed to form a slit sideways of the body, i.e., being wide but with little height. Distended, it forms a gourd-shape or pear-shape balloon, wider at the top and possibly lopsided because of the greater size of one lateral pocket or fornix.

The anterior wall generally is greater than 3 inches long and the posterior wall generally is greater than 4 inches long. These lengths are measured from the hymen to the rearmost wall of the vagina. The width at the rearmost or upper end ranges from about 11/2 inches to 3 inches and the circumference at that point is about 8 inches.

Menstrual fluid enters the vagina through the cervix which is located where the vagina is most distensible and therefore has its maximum potential cross sectional area. The vagina is least distensible near the introitus and therefore the potential cross section is reduced. The introital region of the vagina is more sensitive to outwardly directed pressures than the remainder of the vagina.

During the menstural period an increased mucosal secretion is released by the vaginal walls and vaginal cervix surface. In the high-menstrual-flow woman, some discharge of whole blood mixed with menses is evidenced. These natural secretions, i.e., the mucoprotein and mucopolysaccharide solutions in vaginal mucus secretions and the clottable whole blood, frequently block the surface of current highly compressed textile tampons and hinder menses sorption. A tampon product having a greater surface area, cell size, and porosity will form a coarse filter medium which is not readily blocked and which absorbs or entraps clots and mucus while continuing to absorb menses.

Methods of collecting the recurring menses which flow periodically from females during their child bearing years are many and varied and are generally well known to those skilled in the art. Internal absorptive devices generally in use are fibrous assemblies which are highly compressed into 11/2 inches to 2 inches long cylinders and approximately 1/2 inch in diameter. These products do not expand in a cross sectional direction until contacted with body fluids. Prior art insertion techniques are designed to achieve placement of the tampon deep (21/4 inches - 21/2 inches) in the vagina near the point of fluid entrance, i.e., near the cervix, and thereby avoid placement near the introitus to avoid wearing discomfort.

Deep insertion, i.e., to a position where the collapsed vaginal vault contains many folds and convolutions, coupled with the small cross sectional area of the compressed tampon frequently results in bypass failures, i.e., the menses discharged from the cervix travels the length of the vagina without contacting the tampon and thereby bypasses the tampon without being absorbed. Bypass failures occur because the deeply inserted, compressed tampon cannot block the many folds and convolutions of the vagina in that deep region, but the menses can and does flow down through these folds and convolutions and ultimately through the introitus to soil the woman's clothing.

An intravaginal device, for proper function per se, must satisfy mutually contradictory criteria, as indicated by the following anatomical facts. (1) The entrance (introitus) to the vagina is provided with a functional sphincter comprised of several muscles which form the main closure of the vagina. These muscles resist distension of the vaginal vestibule, hence, entry to and exit from the vagina proper. Consequently, the diameter of any intravaginal device should be small for easy, comfortable, and safe insertion. (2) Beyond this sphincter, the vagina per se is a flaccid organ, the walls of which are normally collapsed about a horizontal plane, touching one another, to give a cross section of roughly H-shape -- capable of relatively great lateral distension without appreciable resistance.

Therefore, an ideal catamenial tampon should be (1) capable of being easily made small enough in diameter to facilitate insertion into, and removal from the vaginal cavity; (2) thereafter, with minimum effort, being changed to a shape which is large enough in diameter to permit the tampon to substantially fill and conform to the cross section of the vagina; and (3) great enough in absorptive capacity to permit the tampon to be worn for an extended period of time during which it will accumulate the menses released and hold it without leakage. These contradictory requirements are difficult to reconcile.

Catamenial tampons are subject to four distinct kinds of failure: bypass, partitioning, compression, and exceeding saturation capacity. Bypass failure occurs when the menses travels the length of the vagina without contacting the tampon, i.e., the tampon fails to intercept the flowing menses. This generally occurs because the tampon does not fill the cross section of the vagina. Partitioning failure occurs when the menses flow rate past a particular area of the tampon is greater than the absorption rate into the tampon in that area. Thus, although some of the menses is absorbed, that flow which is greater than the absorption rate into the tampon proceeds past the tampon and out the introitus. This partitioning occurs many times because the tampon surface is blocked by mucus secretions, clotted blood, or endometrial debris. Compressive failure occurs when the user inadvertently brings pressure to bear on a tampon which has absorbed menses, and this pressure is great enough to "squeeze" the menses from the tampon. Exceeding the saturated capacity occurs when the tampon has absorbed all the fluid it can, and for every drop added thereafter, another drop must leave the tampon.

OBJECTS OF THE INVENTION

It is an object of this invention to provide a method of making hollow catamenial tampons from flat stock.

A more specific objective of this invention is to provide a method of making hollow, conical catamenial tampons from flat stock.

It is also an object of this invention to provide a method of making hollow catamenial tampons from flat stock with a minimum of scrap.

A further object of this invention is to provide a tampon which effectively provides bypass control.

A more specific object of this invention is to provide a foam tampon with improved absorption and wicking properties.

A further object of this invention is to provide a tampon having superior capacity properties.

A further object of this invention is to provide a tampon which distends laterally when it is deformed by the vertical force exerted thereon by the vagina.

Another object of this invention is to provide a tampon which is easy and comfortable to remove.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a method of making tampons having a cavity therewithin, the method comprising making essentially unstressed blanks of flexible, resilient, elastic, absorbent material and bending one or more of the blanks about the longitudinal axis of the tampon to be formed to form an essentially circular cross sectional tampon with the lateral edges of the blanks lying essentially in a plane with the longitudinal axis. The bending imparts a tensile stress on the exterior surface and a compressive stress on the interior surface thus formed. Then the lateral edges are attached to maintain the blanks in a bent, essentially circular configuration.

In accordance with another aspect of the present invention, there is provided a tampon comprising a flexible, resilient, elastic, absorbent body which has an internal discontinuity which forms an interior surface. The interior surface of the body has and maintains therein a circumferential compressive stress, and the exterior surface of the body has and maintains therein a circumferential tensile stress.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following descriptions taken in connection with the accompanying drawings, in which the thickness of some of the materials is exaggerated for clarity and in which:

FIG. 1 is a plan view of superposed webs of material showing the layout for nested trapezoidal laminae on the web;

FIG. 2 is a perspective of one embodiment wherein trapezoidal laminae are superposed coextensively and attached to form a laminate blank;

FIG. 3 is a perspective view of the finished tampon resulting from inverting, i.e., turning inside out the laminate blank of FIG. 2;

FIG. 4 is a perspective view of a slab wherein an interior slit is made to form a laminate blank having an interior surface;

FIG. 5 is a perspective view of the tampon resulting from inverting the laminate blank of FIG. 4;

FIG. 6 is a perspective view of a flat blank in the form of the segment of a circle;

FIG. 7 is a perspective view of a tampon formed from the flat blank of FIG. 6;

FIG. 8 is a perspective view of a tampon resulting from inverting the tampon shown in FIG. 7; and

FIG. 9 is a perspective view of a tampon formed from the flat blank of FIG. 6 wherein the edges formed by the radii are overlapped and attached.

DETAILED DESCRIPTION OF THE INVENTION

The tampon of this invention has an internal discontinuity, usually an interior cavity, and is made from one or more unstressed blank pieces, which usually are flat i.e., of uniform thickness, of flexible, resilient, dry-expanding, elastic, absorbent material. The internal discontinuity is an internal relief whereby diametrically opposed walls of the tampon have no interconnection across the diameter, thus little or no diametrical tensile strength remains to resist lateral spread when a force transverse the tampon's longitudinal axis is exerted on the tampon. Dry-expanding as used herein means a spreading from a compacted configuration, e.g., as when within an inserter, without relying on the actions of fluids to release compression set which may have taken place within the absorbent body while it was compacted. The exterior surface of the tampon is in tension and its interior surface is in compression. It tends to have a capillary extending from the exterior surface to the interior surface which is larger in diameter at the exterior surface than at the interior surface.

In a preferred embodiment of this tampon as shown in FIGS. 3, 5, 8 and 9, the tampon is conically shaped in addition to being hollow, but alternates to the conical shape would also be acceptable, for example, hollow round cylindrical, hollow square cylindrical, any hollow polygonal cylinder, and pyramidal.

These tampons may also have at least one line of discontinuity in the wall of the tampon. The wall discontinuity if present occurs where the lateral edges of the laminae in a laminate blank, as shown in FIGS. 2 and 4, are attached or at the point of overlap where the lateral edges of a flat blank are attached as shown in FIGS. 7 and 9. As used herein, the words "attaching," "attachment," and the like include any of the methods well known to those of ordinary skill in the art, for example, integrally united as in FIG. 4, sewed, glued, ultrasonically welded.

A preferred embodiment of the tampon of this invention has a generally conical exterior and an interior cavity which is also generally conical. The cavity is coaxial with the exterior of the tampon. The tampon has an exterior height of about 2.0 inches and an external base diameter of about 2.1 inches. The wall thickness is preferably about 0.40 inch, which leaves the interior cavity with a base diameter of about 1.5 inches. The height of the interior cavity is also about 1.5 inches.

The material comprising the absorbent body of this tampon can be any of those materials having acceptable absorbency, resiliency and elasticity properties. The polymeric foams are such a material and are disclosed in detail in the concurrently filed, co-pending, commonly owned application entitled, "Compliant Conformable Tampon", by Bernard A. Dulle, Ser. No. 172,694, said application being incorporated herein by reference. A flexible, resilient polyurethane foam may be used as the absobent body of this tampon. The preparation of flexible, resilient polyurethane foams is disclosed in general and in detail in the text entitled, Polyurethanes: Chemistry and Technology, Vol. XVI (in two parts) of the series entitled High Polymers, by J. H. Saunders and K. C. Frisch, copyrighted in 1962 and published by Interscience Publishers, said work being incorporated herein by reference. A similar disclosure of polyurethane technology can be found in Polyurethane Technology, edited by Paul F. Bruins, copyrighted in 1969 and published by Interscience Publishers, this work also being incorporated herein by reference.

Other disclosures of polyurethane foams can be found in the following patents, all of which are incorporated herein by reference: William J. Considine, et al, U.S. Pat. No. 3,391,091, patented July 2, 1968; William E. Erner, U.S. Pat. No. 3,376,236, patented Apr. 2, 1968; George T. Gmitter, et al, U.S. Pat. No. 3,341,482, patented Sept. 12, 1967; Robert A. Volz, U.S. Pat. No. 3,171,820, patented Mar. 2, 1965; Harlan B. Freyermuth, U.S. Pat. No. 3,148,163, patented Sept. 8, 1964; Robert P. Kane, U.S. Pat. No. 2,955,091, patented Oct. 4, 1960; Rudolf Bick, et al, U.S. Pat. No. 2,938,005, patented May 24, 1960; Newell R. Bender, et al, U.S. Pat. No. 2,888,409, patented May 26, 1959; and Andrew Mitchell III, U.S. Pat. No. 2,850,464, patented Sept. 2, 1958.

The absorbent material for the tampon of this invention should be mensesphilic, i.e., have surface characteristics such that the menstrual fluid tends to spread readily or spontaneously on the surface and in the capillaries. This spreading tendency is primarily a function of (1) the nature and packing of atoms or groups of atoms in the surface layer of the molecules of the absorbent body and (2) the affinity of the outermost groups of atoms comprising these molecules for the molecules of the fluid. Secondary factors which modify the spreading tendency include roughness of the surface and the affinity for the menstrual fluid of the layers of atom groups just below the surface atoms.

Since the menstrual fluid is primarily an aqueous solution, materials onto and into which it spreads readily could be loosely described as hydrophilic. However, the state of the art respecting wetting of materials allows a more precise description in terms of contact angles and surface tensions of the fluids and solids involved. This description is disclosed in detail in the American Chemical Society publication entitled Contact Angle, Wettability and Adhesion, edited by Robert F. Gould, and copyrighted in 1964; said publication being incorporated herein by reference.

The contact angle is defined as the angle formed between two planes as measured in the liquid, i.e., the plane tangent to the liquid-air interface at the point of liquid-air-solid mutual contact and the plane of liquid-solid contact at the liquid-air-solid mutual contact. The smaller this angle is, the less is the force required to spread the liquid and at a contact angle of zero. the fluid tends to spread spontaneously and without limit on the surface of the solid. In general, materials having a contact angle between them of less than 90.degree. can be described as -philic (attractive toward each other) and those having angles greater than 90.degree. between them as -phobic (repellent toward each other). Therefore, a mensesphilic material can be definitely but broadly defined as one with which menstrual fluid makes a contact angle of less than 90.degree..

The contact angle between a fluid and a solid, and consequently the philicity or phobicity of the solid for the liquid, is related to the ratio between the surface tension of the fluid and the solid. In practice, the method for determining surface tension of the solid is to compare contact characteristics of the solid against various liquids. This method is more completely described on p. 12 et seq. of the above mentioned publication. The value derived from this method is usually called the critical surface tension of the solid. If the ratio is greater than 1:1, i.e., the surface tension of the fluid is greater, the solid is -phobic. If the ratio is less than 1:1, i.e., the surface tension of the solid is greater, the solid is -philic. As the ratio becomes smaller, the solid is more and more -philic.

Menstrual fluid has a surface tension range of about 35 to 60 dynes per centimeter. It will have a contact angle of less than 90.degree. and will tend to spread spontaneously on a solid which has a critical surface tension value greater than its surface tension.

Water has a high surface tension which is about 72 dynes per centimeter and would be apt to spread spontaneously only on solids with critical surface tensions higher than 72 dynes per centimeter unless the solid's surface has changed through an interaction with the water. Therefore, hydrophilicity is not a precise definition with respect to the affinity of a solid for menstrual fluid. The contact angle between menstrual fluid and a solid or the ratio between the surface tension of the menstrual fluid and the critical surface tension of the solid is definitive of their mutual affinity and tendency toward spontaneous wetting. Since the surface tension of water is higher than that of menstrual fluid, any solid which is hydrophilic is also usually mensesphilic.

Although flexible polyurethane foams in general can be used, there are drastic differences in tampon performance between tampons prepared from conventional mensesphobic flexible polyurethane foams and mensesphilic flexible polyurethane foams. The differences are sufficiently great that mensesphilic polyurethane foams are highly preferred. Even within mensesphilic polyurethane foams there is a wide variation in performance; and it is most preferred to use mensesphilic polyurethane foams having good wet swell properties since the total volume of menstrual fluids which can be contained by a tampon is related to its eventual size and yet one prefers to have a tampon of minimal size for ease of insertion. Minimal size is especially important where one uses an inserter of the type that requires the tampon to be pushed out through a cylindrical portion of the inserter. Another desirable quality is low compression set when radially compressed within an inserter since dry expansion after insertion provides better bypass control. It is, of course, desirable to use foams having a minimum content of extraneous soluble materials since the product may be retained in the body for a considerable period of time and retained soluble extraneous materials could cause a safety hazard if they are toxic.

In general, the flexible polyurethane foams used in the preferred embodiment of this invention will be prepared from a reaction mix comprising a polyhydroxy compound which will be, at least in part, a polyether but which may be also, in part, a polyester, and mixtures of polyester and polyether compounds. The following patents, all of which are incorporated herein by reference, disclose mensesphilic polyurethane foams which are especially desirable. Joerg Sambeth, et al, U.S. Pat. No. 3,586,648, patented June 22, 1971; Alexis Archipoff, et al, U.S. Pat. No. 3,573,234, patented Mar. 30, 1971; Joerg Sambeth, et al, U.S. Pat. No. 3,560,416, patented Feb. 2, 1971; Charles H. Hofrichter, et al, U.S. Pat. No. 3,463,745, patented Aug. 26, 1969; Stanley I. Cohen, et al, U.S. Pat. No. 3,457,203, patented July 22, 1969; Joerg Sambeth, et al, U.S. Pat. No. 3,451,954, patented June 24, 1969; Joerg Sambeth, et al, U.S. Pat. No. 3,451,953, patented June 24, 1969; Joerg Sambeth, et al, U.S. Pat. No. 3,432,448, patented Mar. 11, 1969; Rudolf Merten, et al, U.S. Pat. No. 3,388,081, patented June 11, 1968; Bernard Rabussier, U.S. Pat. No. 3,385,803, patented May 28, 1968; James A. Calamari, U.S. Pat. No. 3,164,565, patented Jan. 5, 1965; Morris V. Shelanski, et al, U.S. Pat. No. 3,098,048, patented July 16, 1963; Carl V. Strandskov, U.S. Pat. No. 3,042,631, patented July 3, 1962; Fritz Schmidt, et al, U.S. Pat. No. 3,007,883, patented Nov. 7, 1961; Harold L. Elkin, U.S. Pat. No. 2,965,584, patented Dec. 20, 1960; Erwin Windemuth, et al, U.S. Pat. No. 2,948,691, patented Aug. 9, 1960; Elekal, British Pat. No. 1,180,316, patented Feb. 4, 1970; Vereinigt Papierwerke Schickedanz & Co., French Pat. No. 1,350,709, patented Dec. 23, 1963.

Other mensesphilic polyurethane foams can also be used, including the foams disclosed in the following patents which are also incorporated herein by reference. George Shkapenko, et al, U.S. Pat. No. 3,535,143, patented Oct. 29, 1970; John G. Simon, et al, U.S. Pat. No. 3,508,953, patented Apr. 28, 1970; Whitney R. Adams, et al, U.S. Pat. No. 3,458,338 patented July 29, 1969; John R. Caldwell, et al, U.S. Pat. No. 3,418,066, patented Dec. 24, 1968; Joerg Sambeth et al, U.S. Pat. No. 3,413,245, patented Nov. 26, 1968; Lyle W. Colburn, U.S. Pat. No. 3,404,095, patented Oct. 1, 1968; Fred W. Meisel, et al, U.S. Pat. No. 3,382,090, patented May 7, 1968; Yvan Landler, et al, U.S. Pat. No. 3,326,823, patented June 20, 1967; Ming Chih Chen, U.S. Pat. No. 3,249,465, patented May 3, 1966; Sotirios S. Beicos, U.S. Pat. No. 3,149,000, patented Sept. 15, 1964; John Bugosh, et al, U.S. Pat. No. 3,094,433, patented June 18, 1963; Karl Goldann, U.S. Pat. No. 2,998,295, patented Aug. 29, 1961; Marvin J. Hurwitz, et al, U.S. Pat. No. 2,990,378, patented June 27, 1961; John Bugosh, U.S. Pat. No. 2,920,983, patented Jan. 12, 1960; and William R. Powers, et al, U.S. Pat. No. 2,900,278, patented Aug. 18, 1959.

In general, it is preferred to have mensesphilic foam which is at least partially mensesphilic by virtue of the reactants; but it is also desirable in many instances to add additional mensesphilic materials to the foam to increase either the mensesphilicity of the foam or the ability of the foam to hold liquid and resist compressive failure, i.e., squeeze out. A mensesphilic, polyurethane foam used should have a critical surface tension of at least about 60 dynes per centimeter and preferably greater than about 72 dynes per centimeter.

The foam used as the absorbent body should have a dry modulus of compressibility as defined in ASTM Test D1564, Compression Load Deflection Test (Suffix D), of from about 0.2 pounds per square inch to about 0.6 pounds per square inch, preferably about 0.4 pounds per square inch, and a wet modulus of compressibility to attain 75 percent of the original dry thickness ranging from about 0.1 to 0.3 psi, preferably about 0.2 psi. The ASTM Compression Load Deflection Test consists of measuring the load necessary to produce a 25 percent compression over the entire top area of the foam specimen.

A hollow tampon permits a larger exterior surface than a non-hollow tampon while using the same amount of material as in a non-hollow tampon and can give a shape modulus of compression to the tampon, i.e., the unidirectional pounds force required to deform the tampon to its collapsed state which occurs when the interior cavity is substantially eliminated and the interior surface is reduced to line contact between opposing points, so the tampon will assume its collapsed state under the forces exerted within the vagina. The shape modulus should be greater than about 0.05 pounds so the tampon has some tendency to maintain its shape when compressed. For example, a tampon "as limp as a wet dishrag" would not work well because it has essentially no shape modulus. The shape modulus should not be greater than about 1.0 pound because then the tampon becomes too difficult to deform and retains its round cross section which is not as good for tampon performance because the vaginal walls do have some beam strength and do not drape perfectly; therefore, if the vagina is not fully distended by a tampon, a greater percentage of the vaginal wall is in contact with a collapsed, i.e., flattened, tampon than is in contact with an uncollapsed, i.e., round, tampon, due to the vaginal wall contilevering beyond the lateral edges of the tampon. The shape modulus is dependent upon the density and elasticity of the material and the shape of the tampon.

As a hollow tampon is deformed, the radius of curvature at the lateral edges, i.e., at the termini of the major axis of the elipse formed by deforming, is decreased, thereby placing the exterior surface in tension and the interior surface in compression at the lateral edges, the exterior surface and the interior surface of the top and bottom walls, i.e., the walls at the termini of the minor axis of the elipse formed, respectively put in compression and tension.

The exterior surface of the tampon of this invention is in tension while the interior surface is under compression prior to insertion and collapse in the vagina. When the laminae as shown in FIGS. 2 and 4 or the flat blank as shown in FIG. 6, the laminae and the flat blank comprising the absorbent body of the tampon, are made of a foam cellular material, the exterior tension -- interior compression resulting from bending the foam cellular material establishes a capillary gradient between the exterior and interior surfaces. The exterior tension tends to enlarge the diameter of the cells on the exterior surface and the interior compression tends to reduce the diameter of the cells on the interior surface. Therefore, a capillary beginning on the exterior surface and progressing to the interior surface will have a capillary gradient, i.e., a larger diameter at the exterior than at the interior surface. This capillary gradient is advantageous because it promotes good wicking into the interior from the exterior due to the fact that the smaller capillaries near the interior have a greater capillary attraction than the larger ones and thus pull the fluid deep into the tampon leaving the exterior relatively dry to absorb more menses. Any capillary gradient is acceptable; the capillary gradient in the preferred embodiment is probably about linear and is acceptable to provide the increased driving force on a liquid toward the tampon interior.

The capillary gradient is made greater in some areas of the tampon when it is deformed to its collapsed state. The increased capillary gradient provides better protection from failure in that increased wicking potential exists in those areas. When the hollow tampon is deformed to its collapsed state, the radius of curvature of the lateral edges is decreased, thereby putting the exterior surface in tension and the interior surface in compression as stated previously. Since this tampon already has tension on the exterior and compression on the interior, deforming the tampon results in a greater capillary gradient at the lateral edges since the two tensions imposed on the exterior are additive as are the two compressive stresses imposed on the interior. The top and bottom walls are returned to a substantially neutral state during deformation of the tampon because they are returned to a flat state, so there is essentially no capillary gradient therein. Thus upon deforming this tampon, the capillary gradient is increased at the lateral edges and decreased on the top and bottom walls of the tampon.

The pressure between the vagina and the tampon is at its minimum at the interface between the lateral edges of the two. Thus there is little pressure between them to prevent partitioning of the menses and the increased capillary gradient provides a more effective fluid transport mechanism to attract the menses and prevent partitioning. The maximum force exerted by the vagina on the tampon is vertical and thus contact between the vagina and the top and bottom walls of the tampon is good. This good contact between the vagina and the top and bottom walls of the tampon minimizes partitioning at this interface even though the fluid transport mechanism is not enhanced by a capillary gradient in these regions of a deformed tampon.

Directional porosity in a foam can also promote efficient capillarity in that foam. Partitioning failure is reduced by directional porosity. A foam tampon having the direction of highest porosity transverse the longitudinal axis will absorb more menses, i.e., have less partitioning failure, before failure.

Gas blown foams, i.e., those foams formed by the expansion of a gas generated during the foam formation process, have elongated cells which give directional porosity to the foam. The cell dimension in the direction of the foam rise is longer than the cell dimension in the direction transverse the foam rise. Thus partially open-cell foam has greater porosity and a more efficient capillary system in the direction of the foam rise.

The tampon of this invention made from a foam may have the foam cells within its absorbent body oriented in almost any direction desired. One advantageous cell orientation is such that the direction of the foam rise is perpendicular to the tampon exterior surface. Thus, the dimension of the foam cells transverse to the tampon exterior surface is greater than the dimension of the foam cells parallel to the tampon exterior surface. Orienting the cells within the tampon in the above manner promotes fluid transfer from the exterior surface to the interior surface of the tampon. Another orientation which may be advantageous is to orient the cells parallel to the tampon's longitudinal axis.

The method of forming hollow tampons engendered in this invention is to bend one or more unstressed pieces or blanks of the absorbent material about the longitudinal axis of the tampon to be formed and attach the lateral edges such as 34 in FIG. 1, to maintain the pieces in a bent configuration. It is to be understood that the bending of the unstressed blanks and the attaching of their lateral edges can be done in any order, i.e., the blanks can be attached and then bent or bent and then attached. If the absorbent material is the preferred material, i.e., a foam, the thickness of the unstressed blanks preferably is parallel to the foam rise. The thickness of the unstressed blanks is preferably uniform, but need not necessarily be so. The unstressed blanks are usually flat, but can also be otherwise.

The laminae 31 of FIG. 1 and 21 and 22 of FIG. 2 before attachment, the laminae 25 and 36 of FIG. 4, the sector of a circle of FIG. 6, and cast shapes similar to a hollow cone are all substantially unstressed blanks. The imposition of a bending moment on one or more unstressed blanks gives the tampon the tensile exterior surface and the compressive interior surface which promotes the capillary gradient. Also forming the tampons via this method permits orienting the foam cells with respect to the tampon structure to gain the advantages offered by the elongated cell structure. Forming a hollow tampon by bending a flat piece of absorbent material is faster, more controllable, more efficient, and produces less waste material than cutting a hollow tampon from a solid block of absorbent material.

A tampon of this invention can be formed by a method of attaching the lateral edges 26 of superposed coextensive laminae to form a liminate blank as shown in FIG. 2. The laminae 21 and 22 should preferably be cut from a foam bun so the thickness of the laminae is parallel to the direction of the foam rise. Cutting the laminae in that way orients the foam cells so that any elongation in them due to foam rise will be perpendicular to the exterior surface of the tampon. Triangular or trapezoidal shaped laminae have been found to work well for generally conical or bell shaped tampons.

Trapezoidal laminae which have worked well to form an acceptable tampon each have an altitude of 2.25 inches, a long base of 3.75 inches, a short base of 1.06 inches, and a thickness of 0.4 inch. Flat stock 0.40 inch thick was cut from a foam bun transverse to the direction of rise. Then the similar trapezoidal laminae were cut from that 0.40 inch thick flat stock. Two separately formed laminae were then coextensively superposed and attached together by a zig-zag sewing stitch in an area of attachment 23 along the lateral edges 26 as shown in FIG. 2. The area of attachment can be extended along the short base of the laminae if desired.

A withdrawal string 24 can also be attached within the area of attachment 23 which holds the laminae 21 and 22 together. One way to attach the withdrawal string 24 is to position it within the appropriate area of attachment and then sew it to the laminae at the same time the area of attachment 23 is formed. Although FIGS. 2 and 3 show the withdrawal string 12 depending from the narrow end of the tampon, it is to be understood that the string 12 can also depend from other points of the tampon, e.g., the wide end or base of the tampon. The string 12 can also be attached in ways other than incorporating it into the area of attachment, e.g., tying it to the tampon.

The laminate blank as shown in FIG. 2 is then inverted, i.e., turned inside out whereby the internal surface becomes the external surface, to impose a bending moment upon the laminae which forms the tampon shown in FIG. 3. The tampon of FIG. 3 has a generally conical shape or more specifically a bell shape having essentially a circular cross section and the approximate dimension as follows: altitude of 2.0 inches, exterior base diameter of 2.1 inches, and interior base diameter of 1.2 inches. An essentially circular cross section encompasses all cross sections which are essentially curvilinear, including, for example, the cross section of the shape in FIG. 7. After the laminate blank is inverted, if the withdrawal string 24 was attached as above described, it may be pushed through the apex of the tampon from the interior to the exterior so that it depends from the exterior surface of the tampon.

Inverting a laminate blank imparts a bending moment to the laminae such that the tampon formed has a generally circular periphery in a plane transverse to the tampon's longitudinal axis. This bending moment places the cells on the exterior surface in tension and the cells on the interior surface in compression whereby a capillary size gradient is formed between the exterior and interior surface of the tampon. The average diameter of the capillaries on the exterior surface is larger than the average diameter of the capillaries on the interior surface, and the gradient between the exterior and interior surfaces is substantially linear. It has been determined that the average cell diameter on the exterior surface is approximately 62 percent larger than the average cell diameter on the interior surface of a tampon of the above construction. A tampon having this capillary size gradient promotes good wicking into the tampon from the exterior surface because a fluid will wick deeper as the capillary size decreases.

Laminate blanks formed from more than two laminae can also be formed if it is desirable to make a multilayered tampon. Thus four laminae could be superposed and attached along their lateral edges to form a laminate blank having four layers and three intermediate pockets between the superposed laminae. Special purpose materials such as other absorbents could be placed in the outside pockets thus formed to build different characteristics into the tampon. Also, the laminae could be made of differing materials to develop special absorbency properties within a tampon.

These tampons can also be made from a slab of absorbent material such as is shown in FIG. 4 wherein the thickness of the slab is twice the thickness of the tampon wall. The shape of the blank is determined by the desired shape for the finished tampon. A shape which has been found to work well in forming a hollow, generally conical tampon such as shown in FIG. 5 is a trapezoid. The slab of FIG. 4 used to make the tampon of FIG. 5 is trapezoidal and has a short base at the top, a long base at the bottom and two lateral sides 27. It is cut to form a slit 28 whereby a laminate blank having an interior surface is formed. Slit 28 is parallel to the top and bottom of the slab and propagates from the long base through the thickness of the material toward the short base to separate the slab into a top laminae 25 and a bottom laminae 36. These two laminae 25 and 36 can be equal in thickness or of different thicknesses. The slit 28 stops short of the lateral side 27 so that the laminae 25 and 36 are attached to each other along their lateral edges via areas of attachment 38. An area of attachment along each edge which has been found to be satisfactory is approximately one-half the thickness of a laminae. Therefore, if the slab were 0.8 inch thick and the slit 28 separated the top laminae 25 and the bottom laminae 36 into equal thickness laminae of 0.4 inch each, the area of attachment 38 at each lateral side 27 would be approximately 0.2 inch.

The slit 28 can extend to the short base of the trapezoidal slab if an open ended tampon is desired. If it is preferable to have a tampon having one end opened and the other end closed, the slit 28 can stop short of the short base of the trapezoid in order to form a closed end tampon.

The slit slab as shown in FIG. 4 is then inverted, i.e., turned inside out to form the tampon as shown in FIG. 5. This forms a substantially smooth exterior surface tampon and the elasticity and resiliency of the absorbent material imparts a bending moment to each of the top laminae 25 and the bottom laminae 36 so as to form a substantially conical hollow tampon wherein the exterior surface is in tension and the interior surface is in compression.

Referring now to FIG. 1, it can be seen that tampons of this invention can be made economically on a production basis in the following manner: Webs 37 of laminae 31, formed from the flexible, resilient, elastic, absorbent material to be used, are superposed to form a stack-up of laminae. The width of the web 37 is wide enough to accommodate the height of a trapezoidal lamina 31, so that a web 37 of nested trapezoidal laminae 31 is at least as wide as the altitude of the laminae 31. These webs can be made from the mensesphilic polyurethane foam absorbent material described above and can be of a length which is convenient and easy to handle. Long lengths of the web can be prepared and wound on spools so that the web can be fed from the spool into a tampon making operation. The thickness of the web can be as desired and depends upon the size and shape of the tampon to be formed. For a tampon of the size and shape described in the above method of making a tampon from superposed trapezoidal laminae, a web thickness of 0.40 inch has been found to produce an acceptable tampon.

The desired number of webs are then superposed so their lateral edges coincide and areas of attachment 35 attaching the superposed webs are formed in a pattern such that the approximate centerlines of the areas of attachment define the lateral edges 34 of the laminae whereby a sequence of laminate blanks are formed. The areas of attachment 35 are a means of attaching the laminae contained in the top web to the laminae contained in webs underlying the top web while leaving the center portion of the laminate blank unattached. As alternates to the sinesodial areas of attachment shown in FIG. 1, the areas of attachment 35 can also be straight, continuous, or intermittent areas which are centered on the lateral edges 34 of the laminae 31. The laminate blanks formed from the laminae 31 are then severed from the adjacent material by cutting along the centerlines of the areas of attachment 35.

As seen in FIG. 1, the laminae 31 can be nested on the webs 37 so that little or no waste results when the laminate blanks are cut free from the adjoining material. Trapezoidal laminae nest well on a continuous web.

The severed laminate blanks are then inverted as described above to form a tampon similar to the one shown in FIG. 3. Again, the inverting of the laminate blank places a bending stress upon each laminae to form a tampon which is generally conical and has a hollow interior whereby the external surface of the tampon is in tension and the internal surface is in compression.

The tampon of this invention can also be made by folding over flat blanks, such as the circular sector shown in FIG. 6 which has lateral edges 29. Again, a thickness of about 0.4 inch has been found to perform satisfactorily and a segment including about 130.degree. has produced a tampon which works well. The flat blank is folded over about one of its radii such that its lateral edges 29 are superposed as shown in FIG. 7. Then an area of attachment 30 is applied to the superposed lateral edges to retain the flat blank in a bent configuration, such as the shape shown in FIG. 7. The bending of a resilient, elastic flat blank imparts a tensile stress to the exterior surface and a compressive stress to the interior surface. The form shown in FIG. 7 could be used as is for a tampon, but to make a tampon which is more aesthetically appealing in that its exterior surface does not have the protruding edge caused by the area of attachment, the tampon of FIG. 7 can be inverted to produce the tampon as shown in FIG. 8 wherein the edge is located on the interior surface of the tampon and the exterior surface becomes the interior surface. Inverting the tampon of FIG. 7 reverses the surface stress such that the exterior surface of the tampon of FIG. 8 is in tension while the interior surface is in compression.

A flat blank in the form of a sector of a circle shown in FIG. 6 can also be bent or folded over to form a tampon with a slightly different configuration than shown in FIG. 8 by folding the flat blank over and superposing the lateral edges 29 in an overlap joint such as is shown in FIG. 9. The overlapped superposed lateral edges are then attached with an area of attachment 40 to form a hollow, generally conical tampon. This tampon need not be inverted for aesthetic or other reasons because it will have substantially the same shape and stresses regardless of which surface is the exterior surface.

The above methods of bending flat stock to form hollow tampons are not limited to conical shaped tampons but also apply to other shapes which can be formed from flat stock such as hollow cylinders having a circular cross section and hollow cylinders having a polygonal cross section.

Thus it is apparent that there has been provided, in accordance with the invention, a tampon that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as follows in the spirit and broad scope of the appended claims.

Claims

What is claimed is:

1. A tampon comprising: a flexible, resilient, elastic, absorbent body, said body being a cellular material having a dry modulus of compressibility of from 0.2 p.s.i. to 0.6 p.s.i., said body having an internal discontinuity forming an interior surface, said material having been deformed subsequent to cell formation so as to provide the interior surface of said body with a circumferential compressive stress and the exterior surface of said body with a circumferential tensile stress so that the exterior surface portion is tensilely strained and the interior surface portion is compressively strained and the cell diameters parallel to and at said exterior surface are thereby made generally larger than the cell diameters parallel to and at said interior surface, thereby establishing a capillary gradient between the exterior and interior surfaces which creates a driving force from the exterior surface toward the interior surface.

2. The article of claim 1 wherein said body is a plurality of blanks of said material arranged so that said blanks encircle the longitudinal axis of the tampon, the lateral edges of each blank being adjacent the lateral edges of adjacent blanks, said adjacent lateral edges of adjacent blanks being attached, thereby forming a continuous wall about the longitudinal axis of the tampon, said body being subsequently inverted to provide and maintain said cellular deformation.

3. The article of claim 1 wherein said material is of substantial thickness and has been inverted subsequent to cellular formation and provision of said internal discontinuity, to interchange and reverse said interior and exterior surfaces and compressively stress the resultant interior surface and tensilely stress the resultant exterior surface.

4. A tampon, comprising: a flexible, resilient, elastic, absorbent body, said body being a material having a dry modulus of compressibility of from 0.2 p.s.i. to 0.6 p.s.i., said body having internal discontinuity forming an interior surface, the interior surface of said body having and maintained therein a circumferential compressive stress and the exterior surface of said body having and maintained therein a circumferential tensile stress wherein said material is an absorbent foam and has elongated cells therein, and the dimension of the foam cells transverse the tampon exterior surface is greater than the dimension of the foam cells parallel to the tampon exterior surface.

5. A tampon, comprising: a flexible, resilient, elastic, absorbent body, said body being a material having a dry modulus of compressibility of from 0.2 p.s.i. to 0.6 p.s.i., said body having internal discontinuity forming an interior surface, the interior surface of said body having and maintained therein a circumferential compressive stress and the exterior surface of said body having and maintained therein a circumferential tensile stress wherein said material is an absorbent foam and the foam cell diameters parallel to and at said exterior surface are generally larger than the foam cell diameters parallel to and at said interior surface, thereby establishing a capillary gradient between the exterior and interior surfaces which creates a driving force from the exterior surface toward the interior surface.

6. The article of claim 1 wherein said modulus is about 0.4 psi.

7. A tampon, comprising: a flexible, resilient, elastic, absorbent body, said body being a material having a dry modulus of compressibility of from 0.2 p.s.i. to 0.6 p.s.i., said body having internal discontinuity forming an interior surface, the interior surface of said body having and maintained therein a circumferential compressive stress and the exterior surface of said body having and maintained therein a circumferential tensile stress, wherein said body is a plurality of blanks of said material arranged so that said blanks encircle the longitudinal axis of the tampon, the lateral edges of each blank being adjacent the lateral edges of adjacent blanks, said adjacent lateral edges of adjacent blanks being attached, thereby forming a continuous wall about the longitudinal axis of the tampon and wherein said material is an absorbent foam and has elongated cells therein, and the dimension of the foam cells transverse the tampon exterior surface is greater than the dimension of the foam cells parallel to the tampon exterior surface.

8. The article of claim 2 wherein said material is an absorbent foam and the foam cell diameters parallel to and at said exterior surface are generally larger than the foam cell diameters parallel to and at said interior surface, thereby establishing a capillary gradient between the exterior and interior surfaces which creates a driving force from the exterior surface toward the interior surface.

9. A tampon, comprising: a flexible, resilient, elastic, absorbent body, said body being a material having a dry modulus of compressibility of from 0.2 psi to 0.6 psi, said body being a plurality of blanks of said material arranged so that said blanks encircle the longitudinal axis of the tampon, the lateral edges of each blank being adjacent the lateral edges of adjacent blanks, said adjacent lateral edges of adjacent blanks being attached, thereby forming a continuous wall about the longitudinal axis of the tampon, said material being an absorbent foam and having elongated cells therein, the dimension of said cells transverse the tampon exterior surface being greater than the dimension of said cells parallel to the tampon exterior surface, and the foam cell diameters parallel to and at said exterior surface being generally larger than the foam cell diameters parallel to and at said interior surface, thereby establishing a capillary gradient between the exterior and interior surfaces which create a driving force from the exterior surface toward the interior surface.