US3543756A

US3543756A - Disposable diaper

Info

Publication number: US3543756A
Application number: US671078A
Authority: US
Inventors: James A Murphy; Charles A Lee
Original assignee: International Paper Co
Current assignee: International Paper Co
Priority date: 1967-09-27
Filing date: 1967-09-27
Publication date: 1970-12-01
Anticipated expiration: 1987-12-01
Also published as: JPS5018425B1; SE340256B; DE1785458A1; GB1248774A; FR1585991A

Description

t Y O United States Patent m13,s43,756

['72] Inventors James A. Murphy 3,322,122 5/1967 Daniel 128/284 Toronto, Ontario, Canada; 3,430,629 3/1969 Murphy 128/284 pp No Knoxville Tennessee Primary Examiner-Charles F. Rosenbaum e g Filed Sept. 27 1967 Attorney-Anderson, Luedeka, Fitch, Even and Tabln [45] Patented Dec. 1, 1970 [731 AS81811 lnlmatim' snsmscr: A disposable diaper having an absorbent pad of New g x k b cellulosic material, such as wood flutf or plies of creped tissue, 2 2 t n W or y is disposed within an encompassing wrapper. The latter has a front facing sheet on one side of the pad for engaging a child's skin and a backing sheet on the opposite side of the pad. These [54] DISPOSABLE DIAPER front and back sheets are subject failing as by tearing or 9 shims, 9 Drawing Figs. spllttmg. Lower costs. less material. and unusually good strength and stretchability are provlded when an assemblage 128/284 of bias laid sheets is disposed within the wrapper. The bias laid 1111- 13/16 sheets are preferably formed of abutted strips of creped tissue having a Iine of strength at angle to the Ionzitudina] and trans. 286, 2 290, 296 verse axes of the diaper. These strips add strength and stretchability in both the longitudinal and transverse [56] References CM directions, particularly in the latter direction. A longitudinally UNITED STATES PATENTS extending expansion pleat may be provided in the backing R1526, 1 51 1/ 1967 Duncan et al 128/284 sheet to permit transverse expansion of the backing sheet. The 2,890,700 6/ 1959 Lonberg-Holm 128/284 diaper is preferably made by a unique process to eliminate the 3,21 1,147 10/ 1 965 Pherson et al. 128/284 crossfeeding and laying of sheets.

Patehted Dec. 1, 1970 3,543,756

' Sheet of 3 INVENTORS amen-5 A. 45: UAW/5 A, Amen/ BY (Md/M, 5 W ATTOPNEYS DISPOSABLEDIAPER This-invention relates to absorbent products andmore par- 'ticularly to disposable absorbent products, such as disposable ble diaper must be formed in an economical manner and primarily from a combination of low cost materials such as, for example, wood pulp or fluff, thin plastic films, paper, or creped tissue. i

It is desirable that the disposable diaper have sufficient strength to resist tearing, splitting or rupturing as the wearer, for instance, an active child bends, twists, squats and otherwise stretches and exerts forces on the diaper. Strength heretofore has been obtained by the addition of heavier weight and more expensive materials which provided increased absorptivity above and beyond that needed and which tend to make the diaper more bulky and cumbersome it its fit about the childjAlternatively, some diapers employ an exces- Pat. No. 3,21 1,147. While these diapers have proved generally satisfactory, the increased number of pliesand their cross laid disposition resulted in considerable expense and did not en- 'tirely solve the strength problem as some of these diapers continued to split at the area of the childs buttocks when subjected to unusual stretching or extremely high tensile forces.

As a child moves, hisbody rubs against the inner facing sheet of the diaper which must necessarily be soft or it will irritate the child's skin, and on occasion, this rubbing abrasion causes a local-disintegration of the fibers. Failure of the cover sheet as a result of such abrasion is more likely when the child has wet the facing sheet.

If the interior or facing sheet of the diaper wrapper fails either by splitting or by a local disintegration'of the sheet, the child's skin may then be subjected to the absorbent pad material, which not only may irritate the skin but also adhere to the skin, and thus be objectionable to the child and its mother. When the outer side or backing sheet of the disposable diaper fails, it usually splits at the area of the buttocks or crotch of the child and this allows leakage or seepage of fluids which will soil the child's clothes and bed-clothing, and, in some instanc'es, result in the loss of absorbent material from a pad. Another area of potential tearing is at the overlapped diaper corners which receive safety pins or adhesive tape to secure the diaper about the'waist.

While it has been'found to be relatively easy to obtain the required absorptivity by increasing the amount of cellulosic fibers or sheets in the diaper, those in the art have been perplexed by the problem of how to maintain a smaller and.

adequate number of absorbent fibers and sheets without seriously depleting the strength of an already minimal strength diaper. The attainment of the object of increasedstrength in the prior art diapers has resulted in the missing of the objective of keeping the amount of fibers and sheets to the minimum level needed for absorbency. Indeed, these objects have appeared to be mutually exclusive and have resulted in compromises, which although resulting in an adequate product, have been relatively costly not only from the standpoint of material costs but also from the standpoint of fabrication costs.

Accordingly, a general object of the invention is to provide improved strength in an absorbent product with a minimum amount of materials and in a commercially feasible manner.

A further object of the invention is to increase bidimensional stretch, strength and stability of a disposable diaper,

particularly in the crosswise direction, to afford strength characteristics more closely akin to a cloth diaper. A further object of the invention is to-provide increased abrasion resistance for the diaper facing sheet, particularly while it is wet and being rubbed by a childs body.

Another object of the invention is to provide a low cost and economical manner of reinforcing a diaper which increases its transverse strength and stretchability.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is an exploded perspective of a diaper embodying the novel features of the present invention;

FIG. 2 is a reduced-in-size perspective view of the diaper of FIG. 1 when folded and ready for use;

FIG. 3 is an enlarged sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a sectional view similar to FIG. 3 of another embodiment of the invention;

FIG. 5 is a sectional view similar to FIG. 3 of still another embodiment of the invention: 1

FIG. 6 is a partially fragmentary view of bias laid sheets for incorporation in the diaper of FIG I;

FIG. 7 is a partially fragmentary view of bias laid sheets according to another embodiment of the invention;

F IG. 8 is a partially fragmentary view of bias laid sheets accordingtoa still further embodiment of the invention; and

FIG. 9 is a diagrammatic illustration of a process for making the diaper of FIG. 1. I Very broadly, the invention relates to a disposable product such as, for example, a disposable diaper ll of generally rectangular shape having an outer wrapper l3 encompassing an interior absorbent pad 15 which, in this instance, is formed of a cellulosic material such as wood pulp. The pad, however, may be formed from other cellulosic materials such as super imposed layers of creped tissue. The wrapper, illustrated, is in the form of a rectangular, integral sheet of creped tissue havingits machine direction, i.e., the direction in which the sheet extends as it is formed on a papermaking machine, in the longitudinal direction. The wrapper is folded into an envelopelike wrapper with an upper or inner side sheet 17 (FIG. 2), which is adapted to be disposed against the babys skin, superimposed over the pad 15. An outer or back side or sheet 19,

which is the exposed side of the diaper, is disposed beneath the pad. The inner sheet 17 of the diaper is formed by folding the

opposite edge portions

21 and 23 into an overlapped relationship as shown by tliedotted lines of FIG. I. To'complete the enclosing of the pad 15 with the wrapper, its opposite ends 25 and 27 are sealed by embossing the fibers of the cover and back sheets together with the fibers of the pad 15. 1

In accordance with the present invention, a diaper is produced which has unusually good qualities, particularly improved stretchability, resistance to abrasion, and resistance to splitting while permitting a reduction in the amount and cost of the cellulosic fibers to approximate more closely the amount of fibers necessary only for absorbency. The diapers are found to possess unusually good resistance to impacts which heretofore cause the diaper-to split. The combination of improved resiliency and strength is provided, particularly in the crosswise direction, i.e., a direction at right angles to the longitudinal dimension of the diaper, by a reinforcing means comprising at least two, superimposed, contiguous, bias laid strips, sheets'or plies 28 and 29 (FIG. 1) of cellulosic material such as creped tissue. The

sheets

28 and 29 are referred to as being "bias laid" because the sheets have their-directions of maximum'stretchability and lines of strength disposed askew,

that is, at an angle or a slant to both the longitudinal and the transverse dimensions of the diaper. The upper sheet 28 has its lines of creping 30 running at an angle to the longitudinal axis so that its line of strength, sometimes referred to as the machine direction, is also at angle to the longitudinal axis of in either the longitudinal and the transverse directions. in asimilar manner, the lines of creping i l of the lower sheets 29 are disposed at angle to the longitudinal and transverse axes of the diaper. It is preferred. that the sheet 29 have its lines of creping disposed at an angle to the lines of creping of the upper sheet 2.3. creping oi the upper sheet Preferably, the lines of creping in the respective sheets are laid at the same angle to the longitudinal axis and are disposed to cross each other at an angle. Thus, both the sheets may stretch in both the longitw dinal and transverse directions and both have their lines of strength disposed aslcew to the longitudinal axis of the diaper.

Diapers made in accordance with the invention have extrerncly good resistance to splitting, particularly to impact forces, as compared to conventional diapers. This increased resistance is thought to be the result of the combined increase in strength and stretchability which allows absorption of energy when the sheets stretch. More specifically, transversely directed forces applied to the diaper by a child bending or squatting, have in some prior art diapers, rapidly exceeded the maximum tensile strength of the diaper cover sheet in the transverse direction because there was little or no transverse stretch permitted by the splitting sheet. On the other hand, the bias laid sheets elongate with transverse stretching of the creping and are able to provide relatively high energy absorption or worlt (force distance) before failure. Thus, the bias laid sheets are able to elongate and withstand transversely directed tensile forces which would split a nonbias laid sheet. Such in creased resistance to splitting is particularly noticeable when bias laid sheets are incorporated in the illustrated diaper in which the cover wrapper i3 is formed with its lines of creping 32 (FIG. 1) running parallel to the transverse direction with both strength and stretchability being reduced in this cross machine direction of the cover wrapper. Although disposable diapers which have a nonwoven front sheet and/or plastic backing sheet have some inherent stretching capability in the crosswise direction, there is a need for increasing their strength as these diapers also fail, in some instances, by splitting even though they employ relative thick pads of creped tissue to increase their strength.

The overall and increased strength of the diaper embodying the bias laid sheets appears to be the result of the combined increased strengths of the various materials as these strengths interplay with one another, particularly as the child moves and causes the sheets to twist and become tightly engaged so that the lines of creping in the various sheets are frictionally acting against each other. The full import of the strength, both real and apparent, is not fully discernible by considering the bias laid sheets by themselves and outside of their actual working environment.

Because of the curvature of the childs buttocks, the outer backing sheet 19 becomes more taut and is more likely to split than the front sheet 17. Moreover, folds or creases in the front side of the diaper allow for some expansion in the cross direction. Accordingly, another important aspect of the invention is to allow additional transverse stretch or movement of the outer back sheet 19 of the diaper to allow the reinforcement to take up the tensile forces in the transverse direction without rupturing the backing sheet, and in this instance, this is accomplished by a longitudinal pleat ill FlGS. 1 3) which allows its folds to separate with exertion of sufiicicnt transverse tensile lorces. This pleat will be described in greater detail hereinaiter.

To provide a balanced diaper which will increase the strength of both the upper side adjacent the skin of the child and the outer back side of the diaper, the preferred ernbcdl ment illustrated in FlG. l, employs two bias laid assemblages or structures 33 and 3 (MG. ll) disposed on opposite sides of the absorbent pndllfi and adjacent the respective inner and F backing sheets. The assemblages are identical in construction and in function and the description of top assemblage comprising the sheets 223 and 29 provides an understanding of the lower assemblage which has identically laid sheets and 2%.

' of the web in this instance, the upper s iformed with a plurality of parallelogram shaped strips of creped tissue each having side edges 1% abutted and. dis osed parallel to each other. The side edges 3-53 are also used at the same angle to the longitudinal axis of the diaper. The lines of creping in each strip are generally perpendicular to side 33 5 or" the strips because the machine direction of the web (not shown), from which the strips formed, is parallel to 1' e edges and perpendicular to the lines of creping in a similar manner, the lower sheet 2% is formed with a plurality or" abutting strips 37 each having parallel side edges disposed at the some, but reversed, anr c oi inclination to the longitudinal dimension of the diape lines o? crcping ill in the lower strips run pcrpendicul. o the side edges so that the line of strength of the lower sheet is also at an to the iongitudinal dimension of the diaper. Thus, the creping of the strips permit stretch in both the transverse longitudinal directions. This is in contrast to the front and back sheets which have their lines of crcping extending generally transverscly of the diaper length and therefore allow relatively little stretch in the crosswise direction.

The exemplary diaper ill. is when completed. as shown in HQ. 2, formed with a pair of opposed, folded side pleats 45 and 4'7 F168. 2 3) extending longitudinally along the side edges of the diaper to provide a seal around the legs of the child and to prevent body fluids from passing outwardly of the diaper in the vicinity of the legs. in this instance, each pleat is formed by folding side edge portions of the pad l5 inwardly toward the center of the diaper, and then back upon themselves to provide two folds 49 and El (FIG. 3) in each pleat overlying the marginal edges of a central portion Sll of the pad H5. The side edge portions are folded at an innerfold line which is in a plane generally coextensive with the side edges of a thicker center portion 5b of the pad. l'lerein, the inner folds Sill are secured to the underlying center portion by embossed spots or areas {Fit 2) located generally centrally or" the fold, Le. medially of both the longitudinal and transverse dimensions of the fold. The spot embossures are made with sufficient pressure to glassine the cellulose, thereby holding the inner fold 5i in place.

in this embodiment, the reinforcing

sheets

23 and 29 extend into and constitute a part of the pleats, and the sheets are thus anchored and held against sliding or shifting longitudinally relative to the pad 15 or the wrapper i3. Also, the spot embossures peg the reinforcing sheets to the pad and the wrapper backing sheet in nonfoldsd diapers, the reinforcing sheets may, if desired, be held by other means to prevent shifting of the reinforcing sheets relative to the pad and wrapper sheets.

Considering now the individual elements of the diaper in greater detail, the strips and 37 forming the bias laid sheets are satisfactorily formed of high wet strength, creped tissue of 12 pound basis weight having a 40 percent stretch and having at least three times the strength in a first direction, i.e., in the machine direction, as in the other direction, this latter direction being perpendicular to the lines of ere-ping. Other creped tissues having different basis weights, stretch or strengths may be employed and fall within the purview of the invention.

Creped tissue is the preferred material for the reinforcing means as it is a low cost product and can be easily disposed of, as for example, by flushing down a toilet. Moreover, it is absorbent and stretches in at least one direction to allow bending and movement of the child. As will be explained hereinafter, the as emblage is in the form of continuous web (FlG. to afford an economical method of manufacture in which the cross laying of sheets may be eliminated.

in the preferred embodiment, the web 53 has a width of about 12 inches, which is the width oi the unfolded pad l5, and the web is severed r being unwounril'rorn a supply roll 64 (FlG. ll) iufolcngllir ut 14 inches, which is the length of the diaper between the ends and 27. Ercicrahly, the strips and 32? have a width in excess of 8 inches between their respective 3-3n and Bil-3L and are slightly longer than 15 inches in length as they run at angle across the width To hold the abutted strips together and to hold the upper and

lower sheets

28 and 29 together when they are being untogether in a suitable mannen'lhe width of the

strips

35 and 37 may be varied considerably and instead of several strips, a 14-inch width may be used, and in this case, only a small portion of a second strip is provided in each diaper.

The creped tissue sheet forming the wrapper 13 consists of a single ply,'lO pound basis weight, high wet strength creped tissue having about 25 percent stretch and about three times the strength in a direction extending longitudinally of the diaper as transversely. The high wet strength is attained by incorporating .sufficient melamine resin or another suitable wet strength agent in the furnish. Preferably, the web has a strength when wet equal to about 25 percent of its strength when dry, as determined by the testing methods set forth in Standard D.l0 of the Physical and Chemical Standards Committee, Technical Section, Canadian Pulp & Paper Association. This wet strength particularly in a direction extending longitudinally of the diaper, renders it particularly capable of supporting the weight of the diaper and the weight of a substantial quantity of bodily waste contained within the diaper, in spite of the normal continuing activity of the child. The bias laid reinforcement sheets afford additional strength in both the longitudinal transverse directions, to aid the wrapper in its resistance to tearing.

It will be recalled that in the exemplary embodiment, the central portion of the wrapper web 13 affording the back side 19 of the diaper is provided with the longitudinally extending pleat all. As shown, the pleat is box-shaped with a pair of inner folds 58 (FIG. 3) covered by an outer flat central area 59 which herein ranges between one-quarter and three-eighths inches in width. The pleat is made in a known manner by forcing' inwardly portions of the tissue and then compressing the central area 59 over the folds to hold the pleat flat. The pleat will remain flat until sufficient transverse tensileforces are exerted to cause the folds to expand and open thereby allowing a portion of the tissue web to slide transversely relativeto the pad. Although the bias laid reinforcements provide increased strengthand toughness to the diaper, with or without the pleat 41, it is preferred topro'vide this pleat to allow the back sheet 19 of the assembled diaper to give, i.e., to slide relative to the pad so that transversely directed tensile forces in the transverse direction may be' taken up directly by the bias laid assemblages without splitting the tissue of the wrapper. Such pleats are particularly effective to prevent the wrapper from becoming taut and then splitting when a child bends at the waist as during sitting or crouching. Other forms of pleats, such as a simple fold or an inverted box pleat may be used in lieu of the box pleat to accomplish the desired end of allowing the bias laid reinforcements to become more effective in receiving and taking up transverse tensile forces.

Preferably, the wrapper web 13 after receiving the pleat, is slightly less than three times the width of the pad 15 so that the web may be folded around the pad while leaving the side edges of the overlapping portions of the, web spaced inwardly from the side edges of the enclosed pad. Although the pleat 41 may be preformed on the back sheet, it is preferred to form the pleat on the wrapper web 13 after it is stripped from the supply roll, as will be explained hereinafter.

The pad 15 is deposited on the lower reinforcing assemblage 34 preferably directly by an air-laying process and. in the preferredform, seen best in FIGS. 1 and 3, is defined by a single layer of sulfite, sulfate or other purified wood pulp which has been disintegrated into loose fibers and reformed into an elongated batt. The pad is integral, that is, there are no internal boundaries, as in multilayered pads, along which various portions thereof might be displaced relative to each other or whichmight become separated or spaced from each other in a manner which would hinder a continuous desirable distribution of body fluids through the diaper. The absence of internal boundaries also insures a uniform flow of fluids in all directions within the pad. in addition, a single layer pad possesses fiber to fiber contact throughout, thus providing better wicking action. I

To enhance an'efficient reception and retention of body fluids, the pad 15 in the exemplary embodiment is provided with a nonuniform cross-sectional configuration having the longitudinally extending portion 50 of greater thickness than an adjacent portion extending in the same direction, and the longitudinally extending central portion is of greater thickness than flanking side portions. For example, the central portion 50 is approximately one-quarter inch in thickness while the outer portions are approximately one-eighth inch in thickness. Thus, the central portion has an increased fluid retaining capacity as compared to the central portion of a pad of uniform cross-sectional configuration and, generally speaking, fluid will flow to the side edges of the diaper only when this capacity is exceeded. The central portion has a width approximating the width of a pleated or folded diaper, the flanking side portions thereby defining the upper two layers of the

pleats

49 and 51.

The pad 15 is preferably approximately one-third the width of the wrapper l3 and is preferably laid centrally thereof so that, after it has been formed, the

edge portions

21 and 23 of the wrapper may be folded around it so as to enclose it. in the preferred method, this is accomplished by means of a folding shoe (not shown) which first folds the left-hand side portion over the pad, as viewed in the direction of travel, and then folds the right-hand portion over the left.

in the preferred diaper 11, the childs skin is protected against chafing or abrasion by the wood pulp pad 15 not only by the inner cover sheet 11, but also by the upper bias laid assemblage 32. The cover sheet 11 also resists disintegration due to abrasion when the diaper is reinforced by bias laid sheets. Also, assemblage 3d protects against the loss of fluid and absorbent pad material in the event that the backing sheet 19 should fail. As large quantities of fluids are received over a short period to time, they rapidly penetrate the upper assemblage and are absorbed and spread by the pad 15. The

pleats

45 and 47 form effective seals about the child's legs and thereby prevent the escape of fluid from about the childs legsv The lower assemblage also assists in preventing the fluids from "striking through the diaper. Because of the increased strength provided by the bias laid sheets, particularly in the transverse direction, the ends 25 and 27 of the diaper may be fastened relatively tightly and securely about the baby's waist by fasteners (not shown) and, even when wet, the bias laid

assemblages

33 and 34 protect against failures which reduce the I effective absorptive capacity of the diapers. Thus, by assuring against failures, the amount of absorbency can be closely approximated and it is possibleto eliminate excessive fibers or plies of material heretofore added to increase the diaper strength.

- diagrammatically illustrated a web 60, which when cut into sheets forms the lower bins laid reinforcing assemblages 34. The web 60 is stripped from a supply roll 63 and moved inn horizontal plane forwardly (to the right as viewed in HQ. 9) along a given path to and through an air-laying device til which air lays wood fluff to form the pad 15 on the web 60. The pad 15 has approximately the same width as that of the web and is laid on the web so and carried forwardly to join the web 53 which is stripped from a supply roll as and superimposed on the pad 15 downstream from the fluff laying device.

The pad and webs53 and 60 travelforwardly, i.e.., to the right in FIG. 9, at the same rate of speed to a station in which the wrapper 13 is folded about them. The wrapper 13 is stripped from the supply roll 7 1, FIG. 9, and is provided with the-centrally located,1longitudinally extending pleat 41- by a forming plow 73.-Herein, the pleat is inthe form of a box .pleat, although other shapes of pleats could be formed. The

now pleated webl3 travels forwardly to meet the webs and the pad, and the

side edge portions

21 and 23 of the wrapper web 13 are folded around the pad in a known manner to complete the envelope for the pad. Preferably, the longitudinally extending edge of the uppermost wrap of the web'13 lies in the crease of the diaper pleats 47 and prevents this edge from cutting or irritating the childs skin. The box pleat 41 is disposed centrally of the diaper pad 15 and permits transverse stretching of the back sheet 19 to allow tensile forces to act directly upon the bias lai reinforcing sheets. Alternatively, the web 13 may be preformed with a pleat such as the box pleat prior'to being wound in the roll, or the pleat could be formed at another downstream station.

The enveloped pad 15 is then embossed transversely of its length approximately centrally of each of the end areas and 27 to secure the pad 15 to the envelope 13. To this end, an upper anvil roll73 is disposed for rotation about a horizontal axis spaced abovethepad 15 and carries a pair-of circumferentially spaced embossing bars 74 into alignment with similar embossing bars 75 disposed on the underside of the web 60. The fibers of the cover wrapper 13, pad 15 and bias laid assemblages are thus interlocked to each other to form end seals. Diapers employing the bias'laid sheets have been found to achieve a stronger and more durable end embossures than have diapers without such bias laid sheets. Therefore, the transverse end seals'retain theloose fluff within the pad and hold the respective plies together.

equal portions, which can be flushed down a toilet or otherwise'disposed of somewhat-more easily than can the entire diaper. The provision of the slits is optional and not an essential feature of the'invention or'necessary to an advantageous utilization thereof. I l

The pleats '45 and 47 provided at the side edges of the diaper, serve to provide a seal around the legs of the child and prevent body fluids fromjpassing outwardly of the diaper in the vicinity of the legs. In a preferred form of the diaper, each pleat is approximately-1% inches in width and is formed by folding the side edge portions of the diaper inwardly, i.e., toward the center of the diaper, and then back upon themselves to'provide each pleat with two folds 49 and S1 overlying the marginal edge portion of the central portion of the pad. In the illustrated method, the sideedge portions are first folded inwardly to and along a line generally coextensive with the side edges of the thicker central portion of the pad 15 and are spot-embossed, as at 54, with sufficient pressure to glassine the cellulose, thereby holding the first fold 51 in place. Herein, the spot-embossing is provided by an upper embossing roll 83 carrying a pair of axially spaced sets of dies 85 carrying a pair of axially spaced sets of dies 85 for embossing six closely spaced prongs or areas at each of the spot-embossures 54. These six pronged embossures at each embossure area also serve to anchor the bias laid sheets against shifting relative to the other sheets in the diaper. The second fold 49 which is innermost and will be disposed nearest the skin when the diaper is worn, is made subsequently, covering the embosses spots 54 to prevent them from causing any possible discomfort. The pleats insure a close fitaround the legs of the child; the spotembossing locks the fold to the edge portion while the unsecured fold of the pleat can unfold or expand into contact with the leg.

After the enveloped embossed pad is pleated and before it is separated into individual diapers by a saw as, it is calendered, i.e., the enveloped embossed pleated pad, which constitutes in effect a plurality of unseparated diapers in stripform and will hereinafter be referred to as diapers, is subjected {to a high compressive flattening pressure for a brief period of time. in the illustrated embodiment, this is accomplished by the set of calendering rolls 87 and 89 which are urged toward each other under pressure while the diapers pass between them.

Although calender rolls subject the diapers to extensive compressive forces over their entire surface, the greatest degree of compression, both temporary and permanent, is sustained by the

pleats

45 and 47 while only slight temporary and little or no permanent compression is sustained by the portions of the diapers intermediate the pleats. This is due to the fact that the diapers are much thicker at the pleats and, hence, the areas intermediate the pleats are not subjected to compressive forces until the pleats have been compressed a significant amount. Since the absorptive capacity of the fluff pad 15 is reduced by compression, calendaring the diapers after they are pleated prevents the portion of the pad intermediate. the pleats from being compressed and, hence, prevents reduction of the absorptive capacity of that portion. This is an important feature of the diaper since it is this unpleated portion which receives the initial flood of body fluid, as previously mentioned and, hence, ideally possesses the greatest absorptive capacity. The calendering of the pleats also serves to adhere together fibers in the folded edge portions of the bias laid reinforcing

assemblages

33 and 34 with fibers in the folded portions of the pad 15 and wrapper 13. Thus, the bias laid sheets are interlocked with the fibers of the pad, front sheet and back sheet and can more effectively take up tensile forces applied to them. Furthermore, fiber interlocking is also provided by the embossing at ends 25 and 27 and by the spot embossures 54.

The use of a rotating circular saw 86 for severance is preferred over other forms of cutting, particularly a chopping form of cut, since it provides a relatively loose fluffy edge which is less irritating to the tender skin of the child. The severance of the enclosed pad' is preferably centrally through the embossed area, thereby forming an embossed end edge portion 25 for each of successive diapers. The transversely embossed area has, preferably, a width on l inch. The web 53 and 60 are simultaneously severed into the

respective sheets

28, 29, 28a and 29a by the sawing operation. In addition to maintaining the envelope 13 in the closed condition, the embossing provides a convenient stiff durable area at the ends of the diaper for receiving safety pins or similar fasteners, as previously mentioned.

In use, the diaper 11 is disposed with the portion of the central section intermediate the

pleats

45 and 47 extending between the legs of the child and upwardly both forwardly and rearwardly to cover the lower abdomen and buttocks respectively. This portion of the diaper is thus positioned so as to receive the initial flood of body fluids from the child. However, since it is uncompressed and of greater thickness, it has the highest absorptive capacity of any portion of the diaper and thus is most capable of retaining the fluids.

Some fluid will flow from the area intermediate the pleats to the pleats as the intermediate area becomes saturated. This flow is received principally by the margins of the thicker central portion 50 of the pad, which margins underlie the pleat folds 49. Since these margins are of greater thickness than the pleat folds, theyv have a greater absorptive capacity and, hence, a greater resistance to strike through than the

folds

45 and 47. They are thus more capable of receiving overflow than the folds. Furthermore, since all portions of the pleats are in a partially compressed state, they all provide some wicking ac tion and there is therefore a tendency for the fluid to be drawn upwardly through the pleats for dispersion throughout the upper portions of the uncompressed pad, as well as throughout the pleats themselves, thereby further minimizing the likelihood of strike through at the pleats.

Those portions of the

pleats

45 and 47 midway between the embossed end portions 25 and 27 of the diaper encircle the legs of the child, serving as a seal which retards the flow of body fluids outwardly along the legs. In this regard, it will be noted that the unpeggedinner fold 49 of each pleat expands into contact with the leg of the child, thereby enhancing the sealing ability of the pleats.

The portions of the pleats adjacent the ends of the diaper are unfolded to permit the embossed end portions to fully encircle the waist of the wearer and to provide a location for safety pins or other fasteners.

That portion of the diaper which is uppermost and encircles the waist of the child when the diaper is worn is strengthened by the bias laid reinforcing sheets and eliminates need for the cross laid strips of prior art diapers. As the bias laid strips are stretchable across the width of the diaper, they permit a snug fit around the waist while allowing sufficient give to insure the child's comfort.

Depending upon the particular strength and absorbency characteristics desired, a bias laid assemblage may be disposed in various locations. When it is desired that the fluid be quickly absorbed by the pad 15 and that additional strength be provided in the area of the backing sheet, one may use diaper lla (FIG. 4) which is identical to the diaper 11 (FIG. 1) except for the location of the bias laid sheets. In the diaper 11a, four bias laid sheets are disposed beneath the pad 15 and a single layer of creped household towel material 91 having a basis weight between 32 to 39 pounds is laid over the pad and beneath the

side edge portions

21 and 23 of the wrapper 13. The bias laidtop sheet 28 and third sheet 28a are identical to the sheets previously described and identified by the same reference characters. Similarlythe second and

fourth sheets

29 and 29a are identical to the previously described sheets bearing the same reference characters. The second and fourth sheets are disposed with their respective lines of strength at an angle to the respective. lines of strength of the first and third sheets.- Although the invention permits a reduction in the number of sheets and fibers employed in prior art diapers, the present invention is not limited to a particular number or arrangement of bias laid sheets.

When it is desired to provide additional abrasion resistance and protection for the childs skin and to use the bias laidsheets more'effectively for their absorptive capacity as well as their strength, the bias laid sheets mayall be disposed above the 'pad 15 as in diaper 11b illustrated in FIG. 5. In this further embodiment ofthe invention, the wrapper '13, is formed of two plies 13a and 13b (FIG. of creped tissue foldedabout the the top sheet 93 would be at an angle to the longitudinal dimension of the. diaper. A bottom layer 95 (FIG. 7) 7) is a sheet of creped tissue disposed with lines of crepe running transversely of the sheet and its line of strength extending ionside edge portidns 21a, 21b and 3a and 23b of the two layer wrapper overlapped, four plies of wrapper tissue are disposed at the inner side of the diaper overlapping the bias laid sheets;

The latter are disposed with their respective lines of strength at an angle to each otherand' atan angle to the longitudinal dimension of the diaper. Thus, the diaper illustrated in FIG. 5 has eight plies on top of the pad 15, to provide additional absorbency at the area of flooding and to protect against chafing or irritation of the skin by the wood fluff pad 15.

The present invention is not limited to having the bias laid sheets formed and disposed separately, i.e., discretely, from either the pad 15 or the wrapper 13. Thus, it is within the purview of this invention to have the bias laid sheets incorporated into or serving per se as the pad, back sheet or front sheet.

Although the exemplary assemblage has both sheetswith lines of strength at an angle to the longitudinal dimension of the diaper, either one or both of the sheets may have their lines of strength in other directions. For instance, in the assemblage 91 illustrated in FIG.'7, the line of strength of only gitudinally of the diaper.

In FIG. 8, each sheet and 97 is an integral, one-piece sheet. Therefore, it is apparent that the reinforcing bias laid sheets may be made in various'manners such as, for example, including a plurality of strips in each sheet. a plurality of strips in only one sheet or integral sheets (FIG. 8).

From the foregoing, it is seen that disposable absorbent product, such as a pad or diaper, is formed with increased strength and good stretchability permitting a reduction in the amount of material employed and elimination of expensive cross laying operations. Transversely directed tensile forces which heretofore split a diaper may be overcome by the bias laid sheets which may expand in the transverse direction and which are oriented with their machine strengths partially in transverse direction. Thus, the facing sheet resists abrasion and disintegration when the facing sheet is wet.

It will be appreciated that stretchability and strength are provided in the longitudinal direction as well as in the transverse direction by the bias laid sheets. Preferably, the bias laid sheets have their lines of greater strength and of greater stretch intersecting the transverse axis of the diaper at an acute angle and this angle usually ranges between I7 and 45. Thus, a resolution of the line of strength of a sheet into right angle components provides, in most cases, a larger component in the transverse direction than in thelongitudinal direction. The increased strength inthe longitudinal direction, however, is also effective in maintaining a balance between the amount .of fibers needed for absorbency and those used primarily for strength. It will be appreciated that the present invention is not limited to bias laid sheets having any particular bias angle with transverse axis of the diaper.

For the reasons pointed out hereinbefore, the overall in crease in strength is surprising in its effectiveness in preventing failure of the diaper and is thought to be due in part to the interplay between the bias laid sheets and theother components of the diaper as the diaper is wrapped about the child and the various portions of the diaperare twisted and overlapped within and about the crotch of the child. Preferably, the bias laid sheets are disposed symmetrically with respect to each other, i.e., at the same but opposite angle to the transverse axis, and'thereby provide balanced stretchability and strength characteristics to the diaper. An expansion pleat may, if desired, be provided in the diaper backing sheet to extend with stretch of the reinforcing sheets so that the bias laid sheets more effectively take up the forces tending to rupture the diaper.

The bias laid sheets employed in the illustrated diapers may be formed in various manners, but the preferred form of bias laid sheets is the subject matter of the invention of copending application of James A. Murphy and Charles A. Lee entitled "Creped Tissue Product" and filed of even date. As disclosed in this copending application, the bias laid ribbon is formed by collapsing a spirally wound tube made with one or more spirally wound webs of creped tissue. The superimposed plies have interlocked fibers at spaced areas after receiving light compression forces which give a textured appearance to the ribbon's surfaces. To further interlock the superimposed plies, spaced embossments are made toglassine together fibers in the respective plies.

While a preferred embodiment has been shown and described, modifications may be made, e.g. as by changing the bias laid materials or angles between the layers of bias laid materials.

We claim:

1., In adisposable diaper of rectangular shape having longitudinal and transverse directions, an absorbent pad of cellulosic material, means defining a wrapper for substantially enclosing said pad and including a reinforcing means having superimposed, contiguous sheets each having expansibility in a direction transverse to said one direction, said lines of greater strength and stretchability of said sheets crossing each other and each line of greater strength of'said sheets being disposed obliquely with respect to the longitudinal and transverse directions.- I

2. A diaper in accordance with claim 1 in which said sheets are formed of creped tissue with the lines of creping of the respective sheets disposed at an angle to each other.

3. A diaper in accordance with claim 2 in which said diaper is provided with longitudinally extending, pleated sides on opposite sides of an unpleated center portion, and in which said reinforcing sheets extend substantially the length of the diaper and transversely across the unpleated portion and into the oppositeside pleats.

4. A diaper in accordance with claim 1 in which at leastone of the reinforcing sheets is formed with a plurality of adjacent strips of creped tissue disposed diagonally relative to said pad, said strips each having their respective lines of strength disposed diagonally of the pad whereby the strips are free to stretch in both longitudinal and transverse directions relative to said pad. i

5. A diaper in accordance with claim 4 in which the reinforcing sheets are forrnedwith a pluralityof adjacent strips of creped tissue-the lines of strength of the strips in one sheet being disposed at the same angle to the longitudinal dimension of the diaper as the strips in the next sheet. 6. A diaper in accordance with claim 1 in which said reinforcing means includes four sheets of creped tissue with alternating sheets having their lines of strength disposed parallel to each other. e v

7. In a disposable diaper having longitudinal and transverse directions, a'rectang'ular'pad of cellulosic material for absorbing fluids and a reinforced wrapper for enclosing said pad having superimposed, contiguous sheets, each sheet having an ex- A I 3,543,756 A pansibility and strength-in one direction greater than its strength and expansibility in another direction, said lines of a greater strength and expansibility of said sheets crossing each other and each line of greater strength of said sheets being disposed obliquely with respect to the longitudinal and transverse directions.

8. In a disposable diaper having a rectangular shape with longitudinal and transverse directions, a pad of absorbent material for absorbing fluids, and an envelope enclosing said pad, the improvement comprising at least two layers of material having a greater strength in one direction than in another direction, each of said two layers having its line of greater strength crossing the line of greater strength of the other layer, each line of greater strength of said two layers being disposed obliquely with respect to the longitudinal and transverse directions, said layers being bonded together and coacting to impart strength to said diaper.

9. A disposable diaper of rectangular shape having longitudinal and transverse directions comprising; a substantially rectangular pad of cellulosic material for absorbing fluids, said pad being folded along longitudinally extending edges thereof to form an inner pleat and outer pleat extending longitudinally along the sides of the diaper, and means enclosing said pad and providing strength and stretchability for said diaper in both the transverse and longitudinal directions, said means comprising at least first and second sheets of creped tissue each having a line strength in one direction greater than its strength in a direction transverse to said one direction and each having'greater stretch in said one direction than in said transverse direction, said lines of greater strength of said first and second sheets crossing each other and each line of greater strength of said first and second sheets being disposed obliquely with respect to the longitudinal and transverse directions.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,543, 756 Dated December 1 n 1970 Inventor) Charles A. Lee and James A. Murphy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 23, change "it" to --in--;

Column 3, line 7, cancel "creping of the upper sheet 28";

Column 7, line 63, cancel "carrying a pair of axially spaced sets of dies 85";

Column 8, line 44, change "on" to --of-- Column 8, line 44, change "web" to --webs-- Column 9, line 57, change "3a" to --23a--;

Column 10, line 2, cancel "7)";

Claim 1, Column 10, line 75, after "expansibility" insert --and strength in one direction greater than its strengt and expansibility--.

SIGN'H) AND SEALED Edward 11. mm In wmmr. 1 Auemng Offi Gomissioner or Patents