Disposable diaper

[0002] This invention relates to disposable diapers for absorption and containment of urine and other body exudates.

[0003] Japanese Patent Application Disclosure (Kokai) No. Hei7-289584 discloses a disposable diaper including leak preventing cuffs normally biased to rise up on an inner surface of the diaper. These cuffs are composed of substantially crescent-shaped elastic sheets which extend longitudinally of the diaper and are bonded under tension along their arc-shaped edges to the inner surface of the diaper. Such an arrangement makes it possible to form the cuffs having their heights gradually decreasing from the maximal dimension in the crotch region to the minimal dimension in the proximity of the waist-opening. The diaper provided with such cuffs is not bulky in the proximity of the waist-opening and therefore convenient for wearing it.

[0004] With this known diaper, a main body of the diaper must be previously curved in order to bond the crescent-shaped cuffs to the main body. A step of bonding the cuffs to the main body previously curved in the corresponding shape inevitably obstructs a desired speed-up of production. In addition, use of an elastic sheet as material for these cuffs necessarily increases the material cost.

[0005] An object of the invention is to solve the problems encountered by the conventional diaper provided with the foregoing leakage proofing cuffs.

[0006] According to the invention, there is provided a disposable diaper comprising a main body serving for absorption of body fluids, the main body comprising, in turn, a liquid-permeable topsheet, a liquid-impermeable backsheet and a liquid-absorbent core disposed therebetween, and a pair of elastically stretchable/contractile leakage proofing cuffs formed along transversely opposite side edges of the main body, the leak preventing cuffs extending longitudinally of the diaper and being collapsed inwardly of the main body onto an inner surface thereof under an elastic bias to rise up the leakage proofing cuffs on the inner surface, wherein the core is defined by front and rear ends and opposite side edges, the side edges being curved inwardly of the core at least along longitudinally middle parts of the side edges, and each of the leakage proofing cuffs at least partially is formed by portions of the topsheet and the backsheet extending outward beyond transversely opposite side edges of the core and includes a lower portion extending in a region defined between the curved side edge of the core and a straight folding line extending longitudinally outside the curved side edge and an upper portion formed by folding an extension of the lower directed transversely of the main body along the straight folding line onto the inner surface of the main body, wherein elastically stretchable/contractile members are secured under appropriate tension to the leak preventing cuffs at least in the proximity of the folding line and in the proximity of an inner side edge of the upper portion extending in parallel to the folding line.

[0007] FIG. 1 is a plan view depicting a part cutaway diaper according to the invention;

[0008] FIG. 2 is a sectional view taken along a line II—II in FIG. 1;

[0009] FIG. 3 is a sectional view taken along a line III—III in FIG. 1; and

[0010] FIG. 4 is a perspective view depicting the diaper as being curved.

[0011] Details of a disposable diaper according to the invention will be more fully understood from the description given hereunder with reference to the accompanying drawings.

[0012] Referring to FIGS. 1, 2 and 3, a diaper 1 includes a main body 2 lying in the middle transversely thereof and a pair of side flaps 3 extending outward from transversely opposite side edges of the main body 2.

[0013] The main body 2 is composed of a liquid-permeable topsheet 6, a liquid-impermeable backsheet 7 and a liquid-absorbent core 8 disposed between these two sheets 6, 7. In FIG. 1, most of the core 8 is depicted with its outline by a broken line. As will be apparent from FIG. 1, the core 8 is defined by longitudinally opposite ends 11, 12 and transversely opposite side edges 13, 13 which are curved inwardly of the core 8. A distance between an imaginary straight line connecting longitudinally opposite ends 16, 17 of each side edge 13 and this side edge 13 is preferably dimensioned to be 5˜40 mm at the middle of this side edge 13.

[0014] The topsheet 6 and the backsheet 7 extend outward beyond the ends 11, 12 and the side edges 13 of the core 8 and are put flat and bonded together by means of hot melt adhesive (not shown) along their extensions. The extensions of the topsheet 6 and the backsheet 7 bonded together in this manner are folded back along respective folding lines 18 defined by the foresaid imaginary lines connecting the longitudinally opposite ends 16, 17 of the respective side edges 13, 13 so that these extensions are collapsed toward an inner side of the main body 2 with the topsheet 6 lying inside. Thus a pair of leak preventing cuffs 25 are formed at transversely opposite side edges of the main body 2. Specifically, portions of these topsheet 6 and the backsheet 7 extending between the respective side edges 13 and the associated folding lines 18 define a pair of lower portions 21 of the leak preventing cuffs 25. Portions of the topsheet 6 and the backsheet 7 collapsed toward the main body 2 define upper portions 22 of the leak preventing cuffs 25. These lower and upper portions 21, 22 of the leak preventing cuffs 25 form together the pair of leak preventing cuffs 25 extending along longitudinally opposite side edges of the main body 2, respectively. Each of the upper portions 22 has its front and rear ends 23, 24 extending outward beyond the longitudinally opposite ends 11, 12 of the core 8 and bonded to the inner side of the main body 2 by means of suitable adhesive (not shown). The upper portions 22 have their inner side edges 26, 26 longitudinally extending in parallel to the respective folding lines 18.

[0015] Each of the leak preventing cuffs 25 including the lower and upper portions 21, 22 is provided with first and second elastically stretchable/contractile members 27, 28. The first elastically stretchable/contractile member 27 extends along the inner side edge 26 between the front and rear ends 23, 24. The second elastically stretchable/contractile member 28 extends along an intermediate part of the folding line 18 between the front and rear ends 23, 24 and is shorter than the first elastically stretchable/contractile member 27. These first and second elastically stretchable/contractile members 27, 28 are secured under appropriate tension to the inner surface(s) of the topsheet 6 or/and the backsheet 7. The first elastically stretchable/contractile members 27, 27 preferably extend in parallel to the respective inner side edges 26, 26. On the other hand, it is not essential for the second elastically stretchable/contractile members 28 to extend in parallel to the respective folding lines 18. Specifically, the second elastically stretchable/contractile members 28 may be more or less curved or bent so long as they extend substantially along the respective folding lines 18 longitudinally of the leak preventing cuffs 25. It is also possible to form these second elastically stretchable/contractile members 28 by a plurality of elastically stretchable/contractile elements extending in parallel one to another, respectively.

[0016] The pair of side flaps 3 have their inner side edges 31, 31 bonded on their inner surfaces by means of hot melt adhesive 32 to an outer surface of the main body 2 in a region of the respective side flaps 3 defined between the respective side edges 13, 13 of the core 8, so that bonding of these flaps 3 may not restrict movement of the lower portion 21 of the leak preventing cuffs 25, in other words, since each of the lower portions 21 is not bonded to a region of the flaps 3 extending outward of the side edge 13, the lower portions 21 can move with respect to the flaps 3. Each of the flaps 3 are composed, in its remainder portion 33, of front and rear wings 34, 36 adapted to cover the wearer's waist regions and a notch 37 extending between the wings 34, 36 so as to surround the wearer's leg. Each of the rear wings 36 is provided with an elastically stretchable/contractile member 41 extending circumferentially of the wearer's waist regions and each of the notches 37 is provided with an elastically stretchable/contractile member 42 extending circumferentially of the wearer's leg. These elastically stretchable/contractile members 41, 42 are secured to the rear wings 36 and the notches 37, respectively, under appropriate tensions. These elastically stretchable/contractile members 41, 42 are depicted as they are exposed on an inner surface of the flap 3 and intended to come in contact with the wearer's skin. It should be understood, however, that the wearer's skin may be protected from direct contact with these elastically stretchable/contractile members 41, 42 by laminating two sheets to form the flap 3 and securing the members 41, 42 to an inner surface at least one of these two sheets. The rear wings 36 are provided in the proximity of their outer side edges with tape fasteners 38 adapted to be releasably anchored to outer surfaces of the respective front wings 34.

[0017] FIG. 4 is a perspective view depicting the posture the diaper of FIG. 1 takes when it is put on the wearer's body. As depicted, the diaper is curved longitudinally with the topsheet 6 lying inside. As the diaper is curved in this manner, the first and second elastically stretchable/contractile members 27, 28 contract, respectively. Consequently, the lower and upper portions 21, 22 of the leak preventing cuffs 25 rise up on the side edges 13 of the core 8 so as to be spaced from inner surfaces of the respective flaps 3 and the upper portions 22 rise up on the inner surface of the main body 2. In this way, the leak preventing cuffs 25 form relatively large leakage preventing walls each presenting a substantially crescent shape. In this posture, each of the leak preventing cuffs 25 has a height corresponding to a dimension from the associated side edge 13 of the core 8 to the inner side edge 26 of the associated upper portion 22. This dimension is maximum in the longitudinally middle region (crotch region) of the main body and gradually decreases toward the front and rear ends of the core 8. The leak preventing cuffs 25 of such an arrangement can effectively prevent a quantity of body fluids discharged on the diaper from leaking through a gap possibly formed between the wearer's body and the diaper when the diaper slips down along the wearer's body.

[0018] To implement the invention, a nonwoven fabric or a porous plastic sheet may be used to form the topsheet 6 and a plastic sheet may be used to form the backsheet 7. The core 8 may be formed by fluff pulp or a mixture of fluff pulp and polymer powder of high absorptivity. A nonwoven fabric, a plastic sheet or a laminate of them may be used to form the flaps 3. It is not important whether these materials for the flaps 3 is hydrophobic or hydrophilic so far as they are breathable and liquid-permeable. Bonding of the respective members may be achieved not only by using suitable adhesive such as hot melt adhesive but also by using a heat-sealing technique so long as the members to be bonded are of heat-sealable nature.

[0019] The leak preventing cuffs 25 depicted as the laminate of the topsheet 6 and the backsheet 7 may be implemented in the other various manners without departing from the scope of the invention. For example, regions of the respective leak preventing cuffs 25 extending in the proximity of the respective side edges 13, 13 of the core 8 may be formed by the topsheet 6 and the backsheet 7 laminated one upon another and the remainder regions may be formed by the backsheet 7 alone or replaced by waterproof sheets prepared separately of the topsheet 6 and the backsheet 7. Instead of separately preparing the pair of flaps 3 to be bonded to the main body 2 along its transversely opposite side edges, respectively, it is also possible to bond the main body 2 to an inner surface of a single hourglass-shaped sheet in its middle region and thereby to form the pair of flaps 3.

[0020] The disposable diaper includes a pair of leak preventing cuffs adapted to rise up on the inner surface of the diaper along the transversely opposite and inwardly curved side edges of the core. These leak preventing cuffs have their heights which are maximal in the crotch region and gradually decrease in the waist regions. The invention makes it unnecessary to prepare the leak preventing cuffs of such configuration separately of the main body as it has conventionally been the case and, in consequence, a corresponding increase in manufacturing cost due to such separately prepared members can be avoided.