AU727282B2 - Disposable diaper - Google Patents

Description

1 .5 P/00/011 28/5/91 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: DISPOSABLE DIAPER The following statement is a full description of this invention, including the best method of performing it known to us DISPOSABLE DIAPER BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a disposable diaper having an absorbent part, a pair of ear parts projecting in opposite directions from the side edges of one longitudinal end portion of the absorbent part, and two fastening means provided on the side edges of the ear parts, respectively, and capable of effectively distributing tensile forces applied to the absorbent part by the fastening means around the waist and around the legs to prevent the leakage of liquid excrements through spaces between the edges of the disposable diaper and the wearer's waist and legs and of giving comfort to the wearer.

Description of the Related Art A generally known disposable diaper comprises an absorbent part for covering the wearer's crotch, formed by sandwiching an absorbent core between a top sheet and a back sheet, a pair of ear parts projecting in opposite directions from the side edges of one longitudinal end portion of the absorbent part so as to lap around the wearer's waist, and two fastening means provided on the side edges of the ear parts, respectively. When using this disposable diaper, the disposable diaper is put on the 0: wearer in an ordinary manner, and then the fastening means are attached to por tions of the absorbent part lapping around the waist, on the opposite sides of the fastening means, respectively, to hold the disposable diaper on the wearer. When thus put on the o wearer, the disposable diaper must fit to the wearer's waist and legs so that any spaces through which liquid excrements will leak may not be formed between the disposable diaper and the wearer's waist and legs. V/hen putting the dispos able diaper provided with the fatstening means provided on the side edges of the ear parts, respectively, on the weare, it is difficult to concentrate the tensile forces applied to the absorbent part by the fastening means effec tively on portions of the absorbent part lapped around the wearer's waist and legs; that is, spaces are formed around the weares legs and liquid excrements leak outside through the spaces around the legs if the disposable diaper is fitted to the wearer's waist, or spaces are formed around the weaers waist and the disposable diaper cannot lap fitly around the weares waist and liquid excrements leak outside through the spaces around the waist if the dispos able diaper is fitted to the wearer's legs.

Various improvements have been proposed to solve such problems and to improve the fit of a disposable diaper to the wearer'swaist and legs. Techniques for

U'

improving the fit of a disposable diaper to both the waist and the legs are disclosed in U.S. Pat. No. 4,680,030 to Aled, et al., U.S. Pat. No. 4,826,499 to Ahr and U.S. Pat.

No. 4,937,887 to Schreiner, which use two pairs of fastening means at tached to a pair of ear parts projecting in opposite direc tions from a portion of the disposable diaper to be lapped around the waist, respectively. These prior art disposable diapers, however, require troublesome work for handling the tow pairs of fastening means and there is room for improve ment in those prior art disposable diapers.

Techniques eliminated such a disadvantage are disclosed in U.S. Pat. No. 4,911,702 to O'Leary and U.S. Pat. No. 4,857067 to Wood, which use two fastening means attached to two ear parts, respectively, and capable of effectively concentrating the .tensile forces applied thereto on portions of the absorbent part lapped around the waist and the legs. However, these techniques mention nothing about the posi tions of the two fastening means to distribute the tensile forces applied to the two fastening means effectively and directly around the waist and the legs and about the posi tions of the two fastening means to distribute the tensile forces applied to the two fastening means around the waist and the legs at an intentionally determined distribution ratio.

SUMMARY OF THE INVENTION -Accordingly, it is a first object of the present invention to provide a disposable .diaper having an absorbent part provided with fastening means positioned so that tensile forces applied thereto are distributed at a desired distribution ratio to a waist .:..lapping section of the absor bent part lapped around the waist and to leg lapping sec tions of the same lapped around the legs.

A second object of the present invention is to provide a disposable diaper having an .absorbent part having leg lapping sections to be lapped around the legs, provided with :elastic leg fastening members, respectively, and fastening means disposed so that the tensile forces applied thereto may be effectively and directly concentrated on a waist lapping section of the absorbent part lapped around the waist and on the elastic leg .fastening members.

A third object of the present invention is to provide a disposable diaper having an.absorbent part having a waist lapping section provided with elastic waist fastening members, and leg lapping sections provided with elastic leg fastening members and fastening means positioned so that the tensile forces applied thereto may be effectively and directly concentrated on the elastic leg fastening members and the elastic waist fastening members.

The present invention relates to a disposable diaper having a first waist lapping section having an upper edge, a crotch lapping section, a second waist lapping section having a lower edge, a longitudinal center axis and a traverse center axis. The disposable diaper includes an absorbent part which has two side edges and is formed by sandwiching an absorbent core between a top sheet and a back sheet so that the absorbent core may correspond to the wearer's crotch when the disposable diaper is put on the wearer.

The disposable diaper also includes a pair of ear parts each projecting outwardly from one of the side edges of the absorbent part in the first waist lapping section near the upper edge. Each ear part has a stress relaxing structure in the inner portion excluding the peripheral portion of the ear part, wherein when a tensile force is applied to the ear part, the tensile stress induced in the stress relaxing structure is smaller than the tensile stress induced in the peripheral portion of the ear part. Each ear part also has a side edge, each side edge of the ear part having a first side edge section and a second side edge section. The first side edge section of said side edge of said ear part extends on the side of the upper edge of the disposable diaper from the intersection point of the side edge of the ear part and a first boundary line extending from a point on the upper edge of the disposable diaper so as to be tangent to a point on the 20 stress relaxing structure on the side of the upper edge. The second side edge section of said side edge of said ear part extends on the side of the transverse center axis of the disposable diaper from the intersection point of the side edge S- of the ear part and a second boundary line extending from a point on the side edge of the absorbent part at which the lower end of the ear part joins to the absorbent part so as to be tangent to a point on the stress relaxing structure on the side of the transverse center axis.

The diaper also includes two fastening means each attached to one of S:"I the side edges of the ear parts. Each fastening means is attached to the ear part in a pulling section of the side edge of the ear part, overlapping at least part of the first side edge section and part of the second side edge section on the side edge of the ear part.

Preferably the point on the upper edge of the disposable diaper from which the first boundary line extends corresponds to the intersection point of the longitudinal center axis of the disposable diaper and the upper edge of the disposable diaper.

Alternatively the point on the upper edge of the disposable diaper from which the first boundary line extends corresponds to the intersection point of a line parallel to the longitudinal center axis of the disposable diaper and the upper edge of the disposable diaper.

As a further alternative the point on the upper edge of the disposable diaper from which the first boundary line extends corresponds to one end of the upper edge opposite to the ear part where the first boundary line ends.

It is also preferred that the disposable diaper has the peripheral portion of the ear part being unstretchable and the stress relaxing structure being stretchable.

It is also preferably for the disposable diaper to have each of the ear parts formed of an unstretchable material, the stress relaxing structure being formed by processing an unstretchable material so as to be stretchable when tensioned and for the stress relaxing structure not to cause the peripheral portion of the ear part to shrink.

oo a a a The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompa nying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. I is a development of a disposable diaper in accordance with the present invention; Fig. 2 is a fragmentary sectional view of a absorbent part of a disposable diaper in accordance with the present invention; Fig. 3 is a fragmentary sectional view of a ear part; Fig. 4 is a plan view of a stress relaxing structure in a first example included in a disposable diaper in accor dance with the present invention; Fig. 5 is a stress relaxing structure in a second example included in a disposable diaper in accordance with the present invention; Fig. 6 is a stress relaxing structure in a third example included in a disposable diaper in accordance with the present invention; Fig. 7 is a stress relaxing structure in a fourth example included in a disposable diaper in accordance with the present invention; Fig. 8 is a typical side view of assistance in explain ing a stress relaxing structure forming device; Fig. 9 is a plan view of a forming plate of the stress relaxing structure forming device; Fig. 10 is a fragmentary perspective view of a stress relaxing structure formed by the stress relaxing structure forming device of Fig. 8; Fig. 11 is a fragmentary perspective view of a formed intermediate film shown in Fig. 10, in a half stretched state; Fig. 12 is a fragmentary perspective view of the formed intermediate film shown in Fig. 10 in a fully stretched state; Fig. 13 is a fragmentary development of a disposable diaper in accordance with the present invention, of assis tance in explaining the substantially equal distribution of a tensile force applied to a fastener to a waist lapping section and a leg lapping section; 0 -6- Fig. 14 is a fragmentary development of a disposable diaper in accordance with the present invention, of assis tance in explaining the distribution of a major part and a minor part of a tensile force applied to a fastener to a waist lapping section and a leg lapping section, respective ly, of the disposable diaper; Fig. 15 is a fragmentary development of a disposable diaper in accordance with the present invention, ofassis tance in explaining the distribution of a minor part and a major part of a tensile force applied to a fastener to a waist lapping section and a leg lapping section, respective ly, of the disposable diaper, Fig. 16 is a fragmentary development of assistance in explaining a first side edge section a and a second side edge section b; Fig. 17 is a fragmentary development of assistance in explaining the distribution of a tensile force applied to the fastening means; Fig. 18 is a fragmentary development of assistance in explaining a method of determining a first side edge sec tion; Fig. 19 is a fragmentary development of assistance in explaining another method of determining a first side edge section; Fig. 20 is a fragmentary development showing a fasten ing means attached to an ear part in a pulling section equally overlapping a first side edge section a and a second side edge section b; Fig. 21 is a fragmentary development showing a fasten ing means attached to an oe* ar part in a pulling section with its longitudinal axis aligned with the bisector of the angle between a first boundary line and a second boundary line;; Fig. 22 is a fragmentary development showing a fasten ing means attached to an ear part in a pulling section having a minor portion overlapping a second side edge section b and a major portion overlapping a first side edge section a Fig. 23 is a fragmentary development showing a fastening member attached to an ear part in a pulling section having a major portion overlapping a second side edge section b and a minor portion overlapping a first side edge section a; Fig. 24 is a fragmentary development of assistance in explaining the relation between a stress relaxing structure, and a first side edge section a and a second side edge section b; Fig. 25 is a fragmentary development of assistance in explaining the relation between a stress relaxing structure, and a first side edge section a and a second side edge section b Fig. 26 is fragmentary development of a disposable diaper in accordance with the present invention showing a modification of the ear part, and a first side edge section a and a second side edge section b on the ear part; -7- Fig. 27 is a fragmentary development of a disposable diaper in an embodiment according to the present invention provided with a fastening means extended obliquely upward from a position corresponding to that of the fastening means shown in Fig. Fig. 28 is a fragmentry development of a disposable diaper in an embodiment according to the present invention provided with a fastening means extended obliquely upward from a position corresponding to that of the fastening means shown in Fig. 23; Fig. 29 is a fragmentary development of a disposable diaper in an embodiment according to the present invention provided with a fastening means extended obliquely downward from a position corresponding to that of the fastening means shown in Fig.

Fig. 30 is a fragmentary development of a disposable diaper in an embodiment according to the present invention provided with a fastening means etended obliquely downward from a position corresponding to that of the fastening means shown in Fig.

23; Fig. 31 is a fagmentay development of a disposable diaper, of assistance in explaining a method of defining a second edge section; Fig. 32 is a fagmentary development of a disposable diaper, of istance in explaining a method ofdefining a first side edge section;o Fig. 33 is a fragmentary development of a disposable diaper in accordance with the present invention rovided with a fastening means in a modification obliquely attached to an ear partn; and S* Fig 34 is a fragmentay development of a disposable diaper in accordance S: with the present invention provided with a fastening means in a modification obliquely attached to an ear part.

-o enotnexpressing In the following description te pressing positions, directions and the like indicate those as viewed in the drawings.

Referring to Fig. 1 a disposable diaper I in a first embodiment according to the resent invention has a first waist lapping section 2a, a crotch lapping section 2b and second waist lapping section 2c, and comprises an absorbent part formed substantially in a rectangular shape, an hour glass shape, a T-shape, an asymmetric hape or such, side flaps 4 formed in the opposite side portions of the absor bent panrt 3, respetively, elastic leg fastening members 5 longitudially extended in the flaps 4 to provide the flaps 4 with elasticity, a pair of ear parts 6 projecting in opposite directions from the opposite side edges of the upper end portion of the first waist -8lapping section 2a of the absorbing part 3, respectively, and two fasteners 7 attached to the side edges 6a of the ear parts 6, respectively.

Referring to Fig. 2 showing a sectional view taken on line A-A in Fig. 1, the absorbent part 3 is formed by sandwiching an absorbent core 9 between a liquidpermeable top sheet 8 and a liquid-impermeable back sheet 10. The top sheet 8 and the back sheet 10 have a length and a width greater than those of the absorbent core 9. At least portions of the top sheet 8 and the back sheet 10, corre sponding to the crotch lapping section 2b and extending outward beyond each longitudinal side edge of the absorbent core 9 form a side flap 4, and elastic leg fastening members 5 are extended longitudinally in the side flap 4 to provide the side flap with elasticity. The absorbent core 9 is unirritative to the skin and capable of absorbing and holding liquid excrements including urine. Generally, the absorbent core 9 is formed of crushed wood pulp generally cold cotton pulp. The absorbent core 9 nay be formed in any suitable shape and construction as occasion demands. The total absorption of the absorbent core 9 must correspond to a design charge and a desired use. The size and the absorb ing ability of the absorbent core 9 are dependent on the wearer's age.

The back sheet 10 prevents wetting an article, such as a bed sheet or underwear, that comes into contact with the disposable diaper 1 with excrements absorbed and held by the absorbent core 9. The back sheet 10 is a film of a thermoplastic polymer, such as a polyethylene film, a polypropylene film or the like, or a film of a composite 'e material, such as film-coated nonwoven fabric. Preferably, the back sheet 10 is an embossed thermoplastic film simulat ing fabric. The top sheet 8 is is a porous foam sheet, a meshed foam sheet, a perforated plastic film or a woven or nonwoven fabric of a natural textile material, such as wood fibers or cotton fibers, a synthetic textile material, such as polyester fibers or polypropylene fibers, or a blended textile material, such as a blend of a natural textile material (or natural textile materials) and a synthetic textile material (or synthetic textile materials). Prefera bly, the top sheet 8 is formed of a hydrophobic material to separate the liquid absorbed by the absorbent core 9 from the wearer's skin.

The ear parts 6 having a substantially trapezoidal shape are joined to the opposite side edges of the first waist lapping section 2a of the rectangular absorbent part 3, respectively, by a known method, such as heat-sealing or adhesive bonding.

The ear parts 6 may be formed integrally with the absorbent part 3 by projecting the respective upper side portions of the top sheet 8 and the back sheet 10 outward in lugs having the shape of the ear parts 6, and directly joining together the projecting lugs of the top sheet 8 and the back sheet 10. The absorbent part 3 and the ear parts 6 may be formed in an integral structure by.cutting a laminated sheet formed by sandwiching a -9sheet between the top sheet 8and the back sheet 10 in desired dimensions. Preferably, the ear parts 6 are formed by laminating a nonWOven fabric 11 of natural fibers, synthetic fibers or a blend of natural fibers and synthetic fibers, a thermoplastic film 13 of polyethylene or polypropylene and a porous film 12 formed by a known process and sandwiched between the nonwoven fabric 11 and the thrmoplac film 13 by adhesive layers 14 and 15 as shown in Fig. 3. When each of the ear parts 6 is formed of an extension of the top sheet 8 and an extension of the back sheet 10, the nonwoven fabric 11 and the thermoplastic film 13 correspond to the extension of the top sheet 8 and the extension of the back sheet 10, respectively. The porous film 12 sandwiched between the nonwoven fabric and the thermoplastic film 13 provides the ear parts 6 with firmness, which facilitates handling the ear pas 6 when putting the diposable diaper I on the wearer.

As shown in Fig. I, the ear parts 6 have each a stress relaxing structure 20 of a shape similar to that of the ear part 6 in their inner portions excluding the peripheral Portions. As shown in Fi th portions excluding the peripheral portions. As shown in Fig. I, the stress relaxing structure 20 may be formed in a trapezoidal shape similar to and smaller than that of the ear part 6. The stress relaxing structure 20 may be formed in a substantiay trapezoidal .ha having longitudinga gaps 20a as shown in Fi. 4 or in a substantially trapeodal shape having ltranserse gaps 20b as shown in Fi L t'rp-zoda- shape having transverse gaps 20b as shapewn in Fio t 5 he z tess relaxing structure 20 may be formed in any uitable shape other than a trapezoidal shape, such as a triangular shape, a rectangular shape, a shape of a part of an ellipse or a shape ofa part ofa circle, provided that the ***stress relaxing structure 20 has a fnc to p t of cir e pr o i e that the 20 of rein structure a a f tion t o relax stress. The stress relaxing structure o t ear may aggregate of a plurality of longtudinal ts 21 in the laminated thee forming the ear part 6 as sho n: lr 2av pan 6 as shown in Fig 6. The stress relaxing struc ture 20 may be a single 2 provded that the singl e s t a is pable of nterceptin the transmission of a tensile force applied to the ear part 6 to the aborent part 3. As shown in Fig. 7, the ear p 6 may be formed in an elastic attachd to a eripher al portion of the elastic structure excluding a r trapeoidal elastic portion corresponding tohe stress relaxin structure 20 to use the inner trapezoidal elastic portion as the stress relaxing structure When a tensile force is applied to the ear part 6, a tensile stress induced in the ::tr stress rlaxing structure 20 is smaller than that which is induced in the peripheral portion of the ear part 6 surrounding the stress relaxing structure 20. Tensile stress is a resistive force developed by a material bearing a tensile load. Therefore, "a struc ture having a small tensile stress" is a structure yielding to and easily stretchable by a comparatively small tensile force. Structures expressed by the term "stress relaxing 10 4 structure" include a vacancy formed in the ear part 6 and virtually serving as a stress relaxing structure Preferably, the stress relaxing structure 20 is formed by the following method.

As shown in Fig. 8, a sheet 21 to form the ear part 6 is compressed between a plate 22 provid ed with a plurality of ridges 22a in an area of the inner surface thereof corresponding to the stress relaxing struc ture 20, and a plate 23 provided with a plurality of ridges 23a in an area of the inner surface thereof corresponding to the stress relaxing structure 20. As shown in Fig. 9, narrow grooves 25a are formed across the plurality of ridges 23a of the plate 23. The plurality of ridges 22a of the plate 22 are continuous and not interrupted. As shown in Fig. 10, the stress relaxing structure formed by thus compressing the sheet 21 between the plates 22 and 23 has a plurality ofundeformed sections 25, a plurality of perma nently deformed sections 26, and transitional sections 27 between the undeformed sections 25 and the permanently deformed sections 26. Ridges 28 are formed in the perma nently deformed sections 26.

The undeformed sections 25 are defined by the narrow grooves 25a of the plate 23 and the corresponding portions of the ridges 22a of the plate 22, and the permanently deformed sections 26 are defined by the respective ridges 22a and 23a of the plate 22 and the plate 23.

When the ear part 6 is tensioned by forces acting in the directions of the arrows E as shown in Fig. 10, the undeformed sections 25 are plastically stretched to some extent as shown in Fig. 11 and, as the undeformed sections 25 are further 0 stretched, the ridges 28 of the permanently deformed sections 26 are flattened as shown in Fig. 12 and the ear part 6 cannot be stretched any further. When the sheet 21 having such characteristics is a laminated sheet, at least one of the component layer of the sheet 21 is formed of a stretchable film, such as a polyolefin film, a lowdensity linear polyethylene film, a low-density polyeth ylene film, a high-density polyethylene film or a polypropylene film.

The stress relaxing structure 20 that can be stretched by a small tensile force is a. thus formed in the sheet 21 forming the ear part 6. Since the periphery of the sheet 21 surrounding the stress relaxing structure 20 is unprocessed, the periphery of the sheet 21 does not yield to tension when the sheet 21 is tensioned or the periphery is harder to stretch than the stress relaxing structure 20. When tensioned, the stress relaxing structure 20 yields to the tensile force to absorb the tensile force and does not cause the peripheral portion of the ear part 6 to shrink.

The sheet 21 forming the ear part 6 may be formed of a somewhat stretchable material. When formed of such a somewhat stretchable material, the stress relaxing structure 20 can be formed in the sheet 21 by the aforesaid process. In either case, the 11 stress relaxing structure 20 can be stretched by a tensile force smaller than that necessary for stretching the peripheral portion of the ear part 6.

As shown in Fig. 13, when a tensile force D is applied to the fastener 7 in a direction perpendicular to the side edge 6a of the ear part 6, the stress relaxing structure 20 of the ear part 6 serves to divide the tensile force D into a component tensile force DI acting on the waist lapping portion and a component tensile force D acting on the leg lapping portion. That is, since a tensile force greater than that necessary for stretching the stress relaxing structure 20 must be applied to the peripheral portions of the ear pan 6 to stretch the periphera portion, most pa of the tensile force D applied to the fastener 7 is divided into the component tensie forces D I and D2, and the compo nent tensile forces D and D2 act directly on regions X and Z of the absorbent part 3, respectively. Even if par of the tensie force D acts on the stress relaxing structure 20, the stress relaxing structure 20 is not stretched in a extreme state as shown in Fig. 12 because the stress relax ing structure 20 can be stretched by a comparatively small tensile force and the peripheral portion surrounding the stress relaxing structure 20 cannot be virtualy stretched. Thus, the stretchable strss relaxing structure 20 absorbs the tensile force that acts thereon and, consequently, any tensile force is not transmited directly to a region of the absorth pe 3. Thu the i force D l *d d t o Y of the absorbent par 3. Thus the tensile force D applied to the fastener 7 is divided into the component tensile force D 1 acting on the waist lapping portion of the absorbent part 3 and the component tensile force D2 acting on the leg lapping portion of the absorbent part 3 to fasten the absorbent part 3 around the waist and the leg.

The division of the tensile force D applied to the fastener 7 into the component R htensile forces DI and D2 cam be adjusted by adjusting the position of a pulling section R.where the fastener 7 is attached to the oblique side edge 6a of the ear panrt 6. When the pulling section R correspond ubstanialy to the dde of the side edge of the StU relaxn structure 20 as shown in Fg. 13, the tensile force D applied to the fa&stener 7 in the direction of the arrow is divided into the component te e force D i the i nt hecmponent tensile force Dl cing around the waist and th tensie force D2 acting around the leg, and the component tensile forces D and D2 are substantially equal to each other. When the sectioing shion i at position shown in Fi. 14 below the position of the pulling Ssection R shown in Fig. 13, the tensile force D applied to the fastener 7 in the direction of the arrow is divided into the component tensile forces DI and D2, the component tensile force DI that acts around the waist is comparatively small and the component tensile force D2 that acts around the leg is comparatively large. When the pulling section R is at a position shown in Fig. 15 above the position of the pulling section

R

shown in Fig. 13, the tensile force D applied to the fstener 7 in the direction of the -12 arrow is divided into the component tensile forces Dl and D2, the component tensile force D that acts around the waist is comparatively large and the component tensile force D2 that acts around the leg is comparatively small.

The position of the pulling section R and the position al relation between the same and other parts to distribute the tensile force applied to the fastener 7 surely to desired portions of the absorbent part 3 will be described below. The position of the pulling section R for the fastener 7 on the oblique side edge 6a is determined by construction shown in Fig. 16. The position of the pulling section R is important for effectively and directly distrib uting a tensile force applied to the fastener 7 to a desired waist lapping portion and a desired leg lapping portion of the disposable diaper 1.

Referring to Fig. 16, a line L-L' indicates the longitudinal center axis of the disposable diaper 1 (absorbent part 3) and a line H-H' indicates the transverse center axis of the disposable diaper 1 (absorbent part 3) perpendicular to the longitudinal center axis L- Indicated at P is the intersection point of the longitudinal center axis L-L' and the upper edge la of the first waist lapping section 2a, at Q is the intersection point of the lower edge 6b of the ear part 6 on the side of the trans verse center axis H-IH and the side flap 4, at LI is a first boundary line extending from the intersection point P so as to be tangent to a point on the stress relaxing structure 20 on the side of the upper edge la, at L2 is a second boundary line extending from the intersection point Q so as to be tangent to a point on the stress relaxing structure 20 on the side of the transverse center axis at A is the intersection point of the first boundary line LI and the side edge 6a, and at B is the intersection point of the second boundary line L2 and the side edge 6a. A first side edge section a extends on the side of the upper edge la from the intersection point A, and a second side edge section b extends on the side of the transverse center axis H-H' from the intersection point B.

A tensile force D applied to the side edge 6a by the fastener 7 is distributed in the ear part 6 as shown in Fig. 17. In Fig. 17, a point M of action of the tensile force "applied to the fastener 7 is in the pulling section R in which the fastener 7 is attached to the side edge 6a and coincides with the intersection point A in this example. When -part of a tensile force applied to the fastener 7 acts on the side edge 6a at the point M of action, the part of the tensile force is decomposed into representative compo nent forces Fl, F2, F3 and F4. The component force FI is directed toward the upper edge Sa and not directly toward the intersection point P. Therefore, the component force F does not act directly on the intersection point P. The direction of the component force F2 is aligned with the first boundary line LI and hence the component force F2 acts directly on the intersection point P. The component force F3 is directed toward the stress relaxing structure 20 and tends to stretch the stress relaxing construction 13 However, since the stress relaxing structure 20 absorbs the force applied thereto, the component force F3 is not trans mitted to the region Y of the absorbent part 3 shown in Fig. 13. The component force F4 is directed toward the intersection point Q and acts directly on the absorbent part 3 at the intersection point Q.

If the point M of action in the pulling section R in which the fastener 7 is attached to the side edge 6a is on the side ofthe transverse center axis H-H' with respect to the intersection point A, at a point M' outside the first side edge ection a (Fig 16), the component force F2 directed om the point M' toward the intersection point P is absorbe by the stress relaxing structure 20 and is ineffective. Therefore, no component force acts directly on the intersection point P if the point M ofation of the tensile force applied to the fastener 7 on the side edge 6a is at the point If the point M action is shifted to a point M" on the side of the upper edge a with respect to the t ction point A shon in F 1 upp d l a with r espect to the intersection point A shown in Fig. 17, if the point M oraction is in the first side edge section a some component force acts directly on the intersection point P.

As is bvious from the foregoing explanation, the first boundary line LI is a boundary line between positions for the point M ofaction that enables the direct action of a component force of the tensle force applied to the fastener 7 on the intersection point P and those for the point M of action that disables the direct action of the component force on the intersection point P. When the point M of action at which the :':tensile force applied to the fastener 7 acts on the ear part 6 is in the first side edge ction at lst pat of the tele force appied to the point M of action is able to act directly on the intersection point P. The second boundary line L2 drawn in connection ith the intersection point Q is a boundary line between positions for the point M of action that enables the direct action of a component force of the tensile force applied the fstener 7 on the intersection point Q When the point M of action at which the tensile force applied to the fastener 7 acts on the ear part 6 is in the second side edge section b, at least part of the tensile force applied to the point M of action is able to act S. directly on the intersect io point Q. Accordingly, part of the tensile force applied to the stI 7 can be applied directly on the desd points P and Q on the absorbent part 3 when th puling section R in which the fastener 7 is attached to the side edge 6a of the ear part 6 overlaps part of the first side edge section a defined by the grst i boundary line L and part of the second side edge section b defined by the second boundary line L2. Since the intersection point P is on the longitudinal center axis L-L' of the disposable diaper 1, the waist lapping portion of the disposable diaper I can be firmly fastened around the waist by applying tensile forces to the two ear parts 6, when par of each of the tensile forces can be applied directly to the intersection point P.

When part of the tensile force applied to each fastener 7 can be directly applied to the 14 intersection point Q, the leg lapping portion of the absorbent part 3 can be firmly fastened around the leg.

In a disposable diaper 1 in a second embodiment accord ing to the present invention, a first boundary line LI may be extended from the intersection point P of the leftward extension of the upper edge la of an absorbent part 3 and the side edge 6a of a left ear part 6 as shown in Fig. 18. A first boundary line LI may be extended from the intersection point P of a line extending along the inner side of a stress relaxing structure 20 in parallel to the longitudinal center axis L-L' of an absorbent part 3 and the upper end edge la of the absorbent part 3 as shown in Fig. 19. In either case, the first boundary line LI is extended from the intersection point P in tangent to an upper point on the stress relaxing structure 20, to determine an inter section point A on the side edge 6a of a right ear part 6.

The respective magnitudes of a component tensile force DI for fastening the waist lapping portion of the absorbent part 3 around the waist and a component tensile force D2 for fastening the leg lapping portion of the absorbent part 3 around the leg are determined by adjusting the ratio of the size of a portion of the pulling section R, in which a fastener 7 is attached to the side edge 6a, overlapping the first side edge section a to the size of the pulling section R, and the ratio of the size of a portion of the pulling section R overlapping the second side edge section b to the size of the pulling section R. The greater the portion of the pulling section R, overlapping the first side edge section a, the greater is the ratio of the component tensile force DI that acts on the intersection point P to the tensile force applied to the fastener 7. An area defined by the first boundary line LI, the upper edge ofthe ear part 6 and a portion of the side edge 6a of the ear part 6 extending upward from the intersection point A is a waist lapping portion fastening component force distributing area 42, and a portion of the side edge 6a associated with the waist lapping portion fastening component force distributing area 42 is a first side edge section a. As long as part of the pulling section R in which the fastener 7 is attached to the side edge 6a overlaps the first side edge section a, a component tensile force of the tensile force applied to the fastener 7 acts directly on the intersection point P. The greater the portion of the pulling section R, overlapping the first side edge section a, the greater is the component tensile force DI distributed to the waist lapping portion fastening component force distributing area 42.

On the other hand, the greater the portion of the pulling section R, overlapping the second side edge section b, the greater is the component tensile force D2 that acts directly on the intersection point Q. An area defined by the second boundary line L2, the lower side edge 6b of the ear part 6 and a portion of the side edge 6a of the ear part 6 extending downward from the intersection point B is a leg lapping portion fastening component force distributing area 43, and a portion of the side edge 6a associated with the leg lapping portion fastening component force distributing area 43 is a second side edge section b. As long as part of the pulling section R overlaps the second side edge section b, a component tensile force of the tensile force applied to the fastener 7 acts directly on the intersection point Q. The greater the portion of the pulling section R, overlap ping the second side edge section b, the greater is the component tensile force D2 distributed to the leg lapping portion fastening component force distributing area 43.

When the pulling section R, in which the fastener 7 is attached to the ear part, includes the intersection points A and B, and the intersection points A and B are at equal distances from the bisector of the pulling section R as shown in Fig. 20, a portion of the pulling section R over lapping the first side edge section a and a portion of the pulling section R overlapping the second side edge section b are substantially equal to each other. Therefore, the component tensile forces Dl and D2 distributed to the waist lapping portion fastening component force distributing area 42 and the leg lapping portion fastening component force distributing area 43 are substantially equal to each other, and hence substantially equal tensile forces are applied to the intersection points P and Q, respectively. When the fastener 7 is attached to the ear part 7 with its longitudi nal axis aligned with the bisector of the angle between the first boundary line LI and the second boundary line L2 as shown in Fig. 21, the tensile force can be further equally distributed to the component force distributing areas 42 and 43.

The ratio between the component tensile force DI distributed to the waist lapping portion fastening component force distributing area 42 and the component tensile force D2 distributed to the leg lapping portion fastening compo nent force distributing area 43 can be adjusted by adjusting the the ratio of the size of a portion of pulling section R, in which a fastener 7 is attached to the side edge 6a, overlapping the first side edge section a to the size of the pulling section R, and the ratio of the size of a portion of the pulling section R overlapping the second side edge section b to the "size of the pulling section R. When the pulling section R overlaps the first side edge section a entirely and overlaps the second side edge section b partly as shown in Fig.

22, a major part of the tensile force applied to the fastener 7 is distributed to the waist lapping portion fastening component force distributing area 42. When the pulling section R overlaps the second side edge section b entirely and overlaps the first side edge section a partly as shown in Fig. 23, a major part of the tensile force applied to the fastener 7 is distributed to the leg lapping portion fastening component force distribut ing area 43. The pulling section R need not necessarily be included in either 16 the first side edge section a or the second side edge section b, provided that pulling section R overlaps the first side edge section a and the second side edge section b at different overlapping ratios, respec tively.

Figs. 24 and 25 show the dependence of the relation between the first side edge section a and the second side edge section b on the position of a stress relaxing structure 20 in an ear part 6 in a disposable diaper 1 in a third embodiment according to the present invention. Referring to Fig. 24, the stress relaxing structure 20 has a shape resembling a rectangle, which is different from the shape of the stress relaxing structure 20 shown in Fig. 16. In the third embodiment, the first boundary line LI extending from the intersection point P so as to be tangent to the stress relaxing structure 20 and the second boundary line L2 extending from the intersection point Q so as to be tangent to the stress relaxing structure 20 do not intersect each other within the ear part 6. The lines LI and L2 intersect the side edge 6a at intersection points A and B, respec tively. A first side edge section a extends on the side of the upper edge la of an absorbent part 3 from the intersection point A, a second side edge section b extends on the side of the transverse center axis H-H' of the absorbent part 3 from the intersection point B, and a neutral section 33 connected with neither the waist lapping portion fasten ing component force distributing area 42 nor the leg portion fastening e:e: *component force distributing area 43 is formed between the first side edge section a and the second side edge section b. The pulling section R in which a fastener 7 is attached to the side edge 6a must extend across the neutral section 33 and overlap the side edge sections a and b partly to concentrate the component forces of the tensile force applied to the fastener 7 directly on the waist lapping portion and the leg lapping portion; that is, the component forces of the tensile force applied to the fasten er 7 can be directly concentrated on desired portions by determining the position of the pulling section R so that the pulling section R overlap the side edge sections a and b partly.

In a disposable diaper 1 in a fourth embodiment accord ing to the present invention shown in Fig. 25, a first boundary line LI is extended from the intersection point P so as to be tangent to a stress relaxing structure 20 and intersects the side edge 6a of an ear part 6 at an intersec tion point A, and a second boundary line L2 is extended from the intersection point Q so as to be tangent to the stress relaxing structure 20 and intersects an extension of the side edge 6a at an intersection point B.

Since the inter section point B is a virtual point apart from the ear part 6, an actual second side edge section b' is a portion of a second side edge section b, on the side edge 6a. A fastener 7 is attached to the side edge 6a in a pulling section R partially overlapping the first side edge section a and the actual second side edge section b'.

Thus the side edge sections a and b can be defined even if the lines LI and L2 do not -17 intersect the side edge 6a. In this specification, an expression, "a point where the first boundary line L1 (second boundary line L2) intersects the side edge 6a" has an implication that "a point where the first boundary line LI (second boundary line L2) intersects an extension of the side edge 6a".

A disposable diaper I in a fifth embodiment according to the present invention is provided with ear parts 6 each having a lower edge 6b having a lower curved portion S curved in the shape of a circular arc as shown in Fig. 26. A second boundary line L2 is tangent to the lower curved portion S of the lower edge 6b and a stress relaxing struc ture 20 and intersects the side edge 6a of the ear part 6 at an intersection point B.

Therefore, a component tensile force of a tensile force applied to the ear part 6 at th.

intersection point B, acting along the second boundary line L2 can be transmitted to an absorbent part 3. A line 34 extended from the the intersection point of the lower edge 6b of the ear part 6 and a side flap 4 extended along the side edge of an absorbent part 3 so as to be tangent to the stress relaxing structure 20 intersects the side edge 6a at an intersection point The transmission of a component tensile force of a tensile force applied to the ear part 6 at the intersection point B' and transmitted along the line 34 is intercepted at the intersection point of the line 34 and the lower edge 6b. In this embodiment, a first side edge section a extends upward from the intersection point A, and a second side edge section b extends downward from the intersection point B. A pulling section R in which a fastener 7 is attached to the side edge 6a must overlap at least a section c between the intersection points A and B in which the first side edge section a and the second side edge section b overlap each other.

Figs. 27 to 30 are fragmentary developments ofdispos able diapers in a sixth to ninth embodiment according to the present invention, which differ from the disposable diaper shown in Fig. 1 only in the direction of extension of the fastener. In each of the disposable diapers 1 of Figs. 27 and 28, a fastener 7 is attached to the side edge 6a of an ear part 6 so as to extend at an inclination meeting an inequality: 0 45°. In .each of the disposable diapers 1 of Figs. 29 and 30, a fastener 7 is attached to the side edge 6a of an ear part 6 so as to extend at an inclination meeting an inequality: 0 When a tensile force D is applied to the fastener 7 attached to the side edge 6a of the ear part 6 as shown in Fig. 27 in the direction of extension of the fastener 7, a component tensile force Di distributed to the waist lapping portion of an absorbent part 3 is smaller than a component tensile force D2 distributed to the leg lapping portion of the absorbent part 3. Since the fastener 7 is attached to the side edge 6a in a pulling section R overlapping both the first side edge section a and the second side 18 edge section b, the tensile force D is distributed to both the waist lapping portion and the leg lapping portion.

In the disposable diaper 1 of Fig. 28, a portion of the pulling section R partly overlapping the second side edge section b is greater than that of the pulling section R partly overlapping the first side edge section a. There fore, the component tensile force D2 distributed to the leg lapping portion is greater than the component tensile force D2 applied to the leg lapping portion of the disposable diaper shown in Fig. 27.

When a tensile force D is applied to the fastener 7 attached to the side edge 6a of the ear part 6 as shown in Fig. 29 in the direction of extension of the fastener 7, a component tensile force DI distributed to the waist lapping portion of an absorbent part 3 is greater than a component tensile force D2 distributed to the leg lapping portion of the absorbent part 3. Since the pulling section R overlaps both the first side edge section a and the second side edge section b,'the component tensile force D2, though smaller than the component tensile force Dl, can be distributed to the leg lapping portion.

In the disposable diaper 1 of Fig. 30, a portion of the pulling section R partly overlapping the first side edge section a is greater than that of the pulling section R partly overlapping the second side edge section b. There fore, the component tensile force Dl distributed to the waist lapping portion is greater than the component tensile force D2 applied to the waist lapping portion of the dispos able diaper shown in Fig.

29.

Figs. 31 and 32 show disposable diapers in a tenth and an eleventh embodiment according to the present invention. The disposable diaper 1 shown in Fig. 31 is similar in construction to that shown in Fig. 16, except that a second boundary line L2 in Fig.

31 for defining a second side edge section b is extended from the upper end 36 of the middle elastic leg fastening member 5 so as to be tangent to a stress relaxing structure and intersects the side edge 6a of an ear part 6 at an intersection point B.

Accordingly, part of a tensile force applied to the ear part 6 at the intersection point B acts directly on the upper end 36 of the middle elastic leg fastening member 5. The second boundary line L2 may be extended from the upper end 37 of the inner elastic leg fastening member 5 or the upper end 38 of the outer elastic leg fastening member The disposable diaper 1 shown in Fig. 32 is similar in construction to that shown in Fig. 16, except that a first boundary line LI in Fig. 32 for defining a first side edge section a is extended from the end 39 of the middle elastic waist fastening member so as to be tangent to a stress relaxing structure 20 and intersects the side edge 6a of an ear part 6 at an intersec tion point A. Accordingly, part of a tensile force applied to the ear part 6 at the intersection point A acts directly on the ends 39 of the middle Sr 19 elastic waist fastening member 35. The first boundary line LI may be extended from the end 40 of the upper elastic waist fastening member 35 or the end 41 of the lower elastic waist fastening member The fastener 7 obliquely attached to the side edge 6a of the ear part 6 may be folded back at the middle thereof as indicated by broken lines as shown in Fig. 33 when packaging the disposable diaper and may project from the side edge 6a when the disposable diaper is unfolded for use. The fastener 7 may be formed in the shape of a fork and may be folded back as indicated by broken lines in Fig. 34. When thus folded back at the middle, no portion of the fastener 7 projects outward from the ear part 6.

The fork-shaped fastener 7 shown in Fig. 34 ensures further reliable distribution of a tensile force applied thereto to the waist lapping portion and the leg lapping portion.

Since the stress relaxing structure 20 is elastic, the stress relaxing structure conforms easily to the shape of the hipbone and the like, which improves the wearing comfort of the wearer.

Although the invention has been described in its preferred forms with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.

a

Claims (6)

1. A disposable diaper having a first waist lapping section having an upper edge, a crotch lapping section, a second waist lapping section having a lower edge, a longitudinal center axis, and a traverse center axis, said disposable diaper including: an absorbent part which has two side edges and is formed by sandwiching an absorbent core between a top sheet and a back sheet so that the absorbent core may correspond to the wearer's crotch when the disposable diaper is put on the wearer; a pair of ear parts each projecting outwardly from one of the side edges of the absorbent part in the first waist lapping section near the upper edge, each ear part having a stress relaxing structure in the inner portion excluding the peripheral portion of the ear part, wherein when a tensile force is applied to the 'ear part, the tensile stress induced in the stress relaxing structure is smaller than the tensile stress induced in the peripheral portion of the ear part, each ear part having a side edge, each side edge of the ear part having a first side edge section and a second side edge section, said first side edge section of said side edge of said ear part extending on the side of the upper edge of the disposable diaper from the intersection point of the side edge of the ear part and a first boundary line extending from a point on the upper edge of the disposable diaper so as to be tangent to a point on the stress relaxing structure on the side of the upper edge, said second side edge section of said side edge of said ear part extending on the side of the transverse center axis of the disposable diaper from the intersection point of the side edge of the ear part and a second boundary line extending from a point on the side edge of the absorbent part at which the lower end of the ear part joins to the absorbent part so as to be tangent to a point on the stress relaxing structure on the side of the transverse center axis; 21 two fastening means each attached to one of the side edges of the ear parts, each fastening means being attached to the ear part in a pulling section of the side edge of the ear part, overlapping at least part of the first side edge section and part of the second side edge section on the side edge of the ear part.

2. The disposable diaper according to claim 1, wherein the point on the upper edge of the disposable diaper from which the first boundary line extends corresponds to the intersection point of the longitudinal center axis of the disposable diaper and the upper edge of the disposable diaper.

3. The disposable diaper according to claim 1, wherein the point on the upper edge of the disposable diaper from which the first boundary line extends corresponds to the intersection point of a line parallel to the longitudinal center axis of the disposable diaper and the upper edge of the disposable diaper. 9 *9•

4. The disposable diaper according to claim 1, wherein the point on the o**o upper edge of the disposable diaper from which the first boundary line extends corresponds to one end of the upper edge opposite to the ear part where the S°first boundary line ends. °99 9 The disposable diaper according to claim 1, wherein the peripheral portion of the ear part is unstretchable and the stress relaxing structure is stretchable.

6. The disposable diaper according to claim 1, wherein each of the ear parts is formed of an unstretchable material, the stress relaxing structure is formed by processing an unstretchable material so as to be stretchable when tensioned, and the stress relaxing structure does not cause the peripheral portion of the ear part to shrink. 22

7. The disposable diaper according to claim 1 substantially as hereinbefore described with reference to the figures. DATED this 16th day of August 1999 THE PROCTER GAMBLE COMPANY WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA VAX D0C028 AU4656896.WPc: LCG/JGO/RES sees