Disposable diaper

Abstract: A disposable diaper (1) is provided with a pair of elastic crotch zone cuffs (28) extending in parallel to each other longitudinally across a front zone (8), a crotch zone (10) and a rear zone (9). The cuffs (28) are each bonded along a base (29) thereof and in the proximity of the base (29), as well as at portions of their longitudinally opposite ends (30, 31), to a topsheet (5) inside transversely opposite side edges of a liquid-absorbent core (7) sandwiched between the topsheet (5) and a backsheet (6). The cuffs (28) are collapsed inwardly of said diaper (1) and have free side edges (35) which are folded outwardly onto non-folded portions of the cuffs (28) which have already been collapsed, and longitudinally opposite ends of said free side edges (35) are bonded to the cuffs (28) or to the topsheet (5).

Description: The present invention relates to a disposable diaper and particularly to a disposable diaper with elasticized leg cuffs. It is well known in this field of technology to provide disposable diapers with a pair of cuffs longitudinally extending in parallel to each other and having a tendency to be stood up toward the user's crotch in order that leakage of excretion which otherwise would possibly occur can be effectively avoided. For example, US Patent No. 5,021,051 discloses the technique according to which longitudinally opposite ends of such cuffs collapsed inwardly of a diaper are bonded to a topsheet and, in a crotch zone of the diaper, free side edges of the cuffs are folded outwardly of the diaper with opposed outer surface sections of the same cuff put one on another and partially bonded together so that a relatively wide space may be obtained between the free side edges of the respective cuffs in the crotch zone of the diaper. In this manner, there is no apprehension that unacceptably large areas of the topsheet might be covered by the collapsed cuffs in the crotch zone and consequently the effective area of the topsheet for liquid permeation might be significantly reduced even though the cuffs are dimensioned to be relatively wide in order that relatively high barriers may be formed by the cuffs when they are stood up. For the disposable diaper generally dealing with loose passage of high fluidity, the pair of cuffs having the tendency to be reacted toward the user's crotch may be arranged to define a relatively small space between their base and thereby to effectively restrain a spread of loose passage and therefore to minimize an area of the user's skin possibly stained with loose passage. Additionally, by dimensioning the cuffs to have relatively large width and to form relatively high barriers when they are reacted, leakage of loose passage can be reliably avoided even if the diaper is considerably spaced from the user's crotch, since the cuffs will satisfactorily function as barriers. However, reducing the space between the base of the respective cuffs and dimensioning the cuffs to be relatively wide will be accompanied with a problem that the cuffs may cover unacceptably large areas of the topsheet, thus substantially reducing the effective area of the topsheet for liquid permeation and seriously preventing the excretion from being properly absorbed. While the technique disclosed in US Patent No. 5,021,051 should have been developed to solve this problem, it is really difficult for this technique to achieve the desired end, since the free side edges folded in two of the respective cuffs are bonded together in the crotch zone and consequently the cuffs can not form the desired high barriers. WO 9309739A discloses a disposable diaper having a permeable topsheet, an impermeable backsheet and a liquid-absorbent core sandwiched therebetween. A pair of cuffs extend in parallel to each other longitudinally across a front zone, a crotch zone and a rear zone of the diaper and are each bonded along a base thereof to the topsheet inside transversely opposite side edges of the core. Each cuff is folded on itself whereby the longitudinally opposite ends of the folded portion of the cuff are bonded to the non-folded portion of the cuff and each cuff also has an elastic free side edge which is stood up from the top sheet between the bonded portions. However, these bonded portions do not feel particularly soft when they come into contact with the user's skin. Also, the external appearance of the diaper is not aesthetically appealing. It is an object of the present invention to solve the problems of disposable diapers described above. To this end there is provided a disposable diaper comprising a liquid-permeable topsheet, a liquid-impermeable backsheet and a liquid-absorbent core sandwiched between these two sheets, these components being assembled together so as to form a front zone, a rear zone and a crotch zone extending between said front and rear zones, and further comprising a pair of cuffs extending in parallel to each other longitudinally across said front and rear zones as well as across said crotch zone, each of said cuffs having a base, a free side edge elasticized with an elastic member attached thereto extending in parallel to said base and longitudinally opposite ends, and said cuffs are bonded along said base outer side edges to the topsheet inside transversely opposite side edges of the liquid absorbent core and said cuffs are also bonded at portions of said longitudinally opposite ends in the proximity of said base to the topsheet inside transversely opposite side edges of the liquid-absorbent core so that said free side edges have a tendency in said crotch zone to be stood up from said topsheet, and so that the cuffs are collapsed inwardly of said diaper and are each folded along a folding line that is parallel to the base and the free side edge, in an outward direction, onto the non-folded portion of the collapsed cuff, longitudinally opposite ends of the folded portions of each cuff being bonded to said non-folded portion; characterized in that:- a cover sheet which is centrally formed with a longitudinally long circular opening and which has substantially the same external shape as said diaper is laid on said topsheet which includes said pair of cuffs provided thereon, the cover sheet being bonded at least along its outer periphery to said topsheet; said opening has a width in said crotch zone larger than the distance between said bases of said cuffs so that said cuffs are stood up in the opening; said elasticized free side edge of each of said cuffs extends under the cover sheet in the vicinity of the longitudinally opposite ends of the opening; and said free side edge at said longitudinally opposite ends of said folded portion of each cuff is spaced apart inwardly of an outer edge of said base of said cuff. With such an arrangement, the base of the cuffs are bonded to the topsheet inside the transversely opposite side edges of the liquid-absorbent core in order that the space between the base of the respective cuffs can be reduced. The free side edges of the respective cuffs having already been collapsed inwardly of the diaper are then folded outwardly of the diaper and bonded at their longitudinally opposite ends to the cuffs themselves or to the topsheet so that the cuffs do not cover unacceptably large areas of the topsheet and may form the desired high barriers when they are stood up. A disposable diaper according to the invention will be described in more detail with respect to the accompanying drawings, in which: Fig. 1 is a plan view of a diaper, according to one embodiment of the invention, as partially broken away; Fig. 2 is a partial perspective view of the diaper as taken along a line 2 - 2 in Fig. 1; Fig. 3 is a partial perspective view of the diaper as taken along a line 3 - 3 in Fig. 1; Fig. 4 is a view similar to Fig. 3; and Fig. 5 is a plan view exemplarily showing another feature of the embodiment. Referring to Fig. 1, a diaper 1 comprises a liquid-permeable topsheet 5, a liquid-impermeable backsheet 6 and a liquid-absorbent core 7 sandwiched between these two sheets 5, 6. These components 5, 6, 7 are assembled together so as to form a front zone 8, a rear zone 9 and a crotch zone 10 extending between these zones 8, 9. Portions of the top- and backsheets 5, 6 extending outward from transversely opposite side edges of the liquid-absorbent core 7 are bonded together to define first cuffs 12 destined to surround respective legs and portions of the top- and backsheets 5, 6 extending outward from longitudinally opposite edges 15, 16 of the liquid-absorbent core 7 define longitudinally opposite ends 17, 18 of the front and rear zones 8, 9, respectively. The first cuffs 12 have notches 20 destined to define respective leg-openings and elastic members 21 are bonded under stretched condition to the respective first cuffs 12 along the notches 20 for fitness around the respective legs. Elastic members 22, 23 are bonded under transversely stretched condition to the ends 17, 18 for fitness around the waist. Tape fasteners 25 extend outward from transversely opposite side edges of the rear zone 9. In the diaper 1, a pair of narrow second cuffs 28 for the crotch zone extend in parallel to each other longitudinally across the front and rear zones 8, 9. The second cuffs 28 have their base or outer side edges 29 bonded to the topsheet 5 at locations inside the respective side edges 11 of the liquid-absorbent core 7 so as to be collapsed inwardly of the diaper 1 and have portions of their longitudinally opposite ends 30, 31 adjacent the respective base or outer side edges 29 also bonded to the topsheet 5. Oblique lines 32 extending left-and-downward indicate the portions of the second cuffs 28 bonded to the topsheet 5. The second cuffs 28 have their free side edges 35 extending in parallel to the base or outer side edges 29 and folded back outwardly of the diaper 1, as will be described later with reference to Figs. 2 and 3. Longitudinally opposite ends 36, 37 of the respective free side edges 35 are bonded to the portions of the second cuffs 28 which have already been collapsed but not folded, as indicated by oblique lines 38 extending right-and-downward. Elastic members 13 are bonded under their longitudinally stretched condition to the respective free side edges 35 so as to extend between the opposite ends 36, 37 of the respective free side edges 35, and the respective free side edges 35 of the second cuffs 28 are folded back by narrow extents thereof to cover the respective elastic members 13. Referring to Fig. 2, the second cuff 28 is bonded along its base or outer side edge 29 and in the proximity thereof to the upper surface of the topsheet 5 by hot melt adhesive 40, then the free side edges 35 and a portion in proximity thereof are folded outwardly of the diaper 1 and bonded to the already collapsed second cuff 28 by hot melt adhesive 41. Referring to Fig. 3, each second cuff 28 has its base or outer side edge 29 bonded to the topsheet 5 and the free side edge 35 and a portion in the proximity thereof folded outwardly of the diaper 1. The second cuff 28 transversely extending from the base or outer side edge 29 to the free side edge 35 includes a zone which is left not bonded to the topsheet 5 and defines a longitudinally narrow portion of the second cuff 28. This narrow portion normally tends to be stood up in a direction indicated by an arrow X, i.e., to be stood up from the upper surface of the topsheet 5 under the contracting effect of the elastic member 13. Fig. 4 shows a condition which is substantially the same as the condition appearing when the diaper 1 is worn. Specifically, as the elastic member 13 contracts between said longitudinally opposite ends of the free side edges 35, the second cuff 28 is stood up from the upper surface of the topsheet 5 on its base or outer side edge 29 so that the free side edge 35 may form a plurality of gathers 47 and bear against the user's crotch (not shown). The stood up second cuff 28 functions as a barrier against excretion of high fluidity such as loose passage and the effectiveness of the second cuff 28 as the barrier becomes further reliable when the free side edge 35 bears against the user's crotch. With the diaper 1 worn, it is well known that a plurality of gathers are formed in said longitudinally opposite ends 17, 18 of the front and rear zones as well as the first cuffs 12 and closely fit around the waist and the legs of the user, respectively, and therefore such aspect will not be described here. Referring to Figs. 1 through 4, the free side edges 35 of the collapsed second cuffs 28 are folded outwardly of the diaper 1 to assure the second cuffs 28 present their width larger than the case in which the second cuffs 28 have no folded portions. Folding of the second cuffs 28 is effective to avoid an apprehension that the second cuffs 28 might cover unacceptably large areas of the topsheet 5 even when the base or outer side edges 29 of the second cuffs 28 are located inside the transversely opposite side edges 11 of the liquid-absorbent core 7. Additionally, even if the second cuffs 28 remain collapsed with the diaper 1 worn, the area of the topsheet 5 available for liquid permeation is never reduced due thereto. In other words if thewidth of each second cuff 28 is dimensioned to form the high barrier when the second cuff 28 is stood up, this will never interfere with the function of the topsheet 5. Furthermore, if a large gap is formed between the user's crotch and the diaper 1, the correspondingly wide second cuffs 28 form adequately wide barriers across such large gap. Referring to Fig. 5, a liquid-permeable or impermeable cover sheet 46 centrally formed with a longitudinally long circular opening 45 and having the substantially same external shape as the diaper 1 is laid on the diaper 1, partially covering the second cuffs 28. The cover sheet 46 is bonded at least along its outer periphery and the peripheral edge of the opening 45 to the topsheet 5 and the second cuffs 28 by hot melt adhesive (not shown). The opening 45 has a width in said crotch zone 10 larger than the distance between the base or outer side edges 29 of the respective second cuffs 28 so that the second cuffs 28 can be stood up inside the opening 45. In this manner, it is also possible to bond the base or outer side edges 29 as well as the free side edges 35 thereof to the topsheet 5 by utilizing the cover sheet 46 laid on the second cuffs 28. According to the invention, the second cuffs 28 may be formed by a liquid-permeable or liquid-impermeable or air-impermeable nonwoven fabric or a plastic film and the other members may be formed by respective materials usually used in this field of technology. To bond the various members together, in addition to well known adhesive or gluing agent, a well known welding technique may be also employed. It should be noted here, though not shown, that the disposable diaper according to the invention may be in the form of briefs type or short pants type in which lateral side edges of the front and rear zones 8, 9 are integrally bonded to each other without employing tape fasteners 25. With the disposable diaper according to the invention, the respective cuffs for the crotch zone have their base or outer side edges bonded to the topsheet inside the transversely opposite side edges of the liquid-absorbent core and their free side edges folded outward, so it is possible to reduce the distance between the base or outer side edges of the respective cuffs sufficiently to restrain a spread of high fluidity excretion such as loose passage and thereby to limit the area of the user's skin possibly stained with such excretion. These cuffs for the crotch zone can be stood up under the contracting effect of the associated elastic members and they can be dimensioned to have a relatively largewidth without apprehension that these cuffs might cover the topsheet over unacceptably large areas and reduce the effective area of the topsheet for liquid permeation. Except the region defined by the opening of the cover sheet, the base or outer side edges as well as the longitudinally opposite ends of the cuffs bonded to the topsheet are preferably covered by the cover sheet. This feature not only contributes to the improvement of the diaper's external appearance but also softens the touch of those bonded portions when they come in contact with the user's skin.

Claims: A disposable diaper (1) comprising a liquid-permeable topsheet (5), a liquid-impermeable backsheet (6) and a liquid-absorbent core (7) sandwiched between these two sheets (5,6), these components being assembled together so as to form a front zone (8), a rear zone (9) and a crotch zone (10) extending between said front and rear zones (8,9), and further comprising a pair of cuffs (28) extending in parallel to each other longitudinally across said front and rear zones (8,9) as well as across said crotch zone (10), each of said cuffs (28) having a base (29), a free side edge (35) elasticized with an elastic member (13) attached thereto extending in parallel to said base (29) and longitudinally opposite ends, and said cuffs (28) are bonded along said base outer side edges to the topsheet (5) inside transversely opposite side edges of the liquid absorbent core (7) and said cuffs (28) are also bonded at portions of said longitudinally opposite ends in the proximity of said base to the topsheet (5) inside transversely opposite side edges of the liquid-absorbent core (7) so that said free side edges (35) have a tendency in said crotch zone (10) to be stood up from said topsheet (5), and so that the cuffs (28) are collapsed inwardly of said diaper (1) and are each folded along a folding line that is parallel to the base and the free side edge (35), in an outward direction, onto the non-folded portion of the collapsed cuff (28), longitudinally opposite ends of the folded portions of each cuff (28) being bonded to said non-folded portion; characterized in that :- a cover sheet (46) which is centrally formed with a longitudinally long circular opening (45) and which has substantially the same external shape as said diaper (1) is laid on said topsheet (5) which includes said pair of cuffs (28) provided thereon, the cover sheet (46) being bonded at least along its outer periphery to said topsheet (5); said opening (45) has a width in said crotch zone (10) larger than the distance between said bases (29) of said cuffs (28) so that said cuffs (28) are stood up in the opening (45); said elasticized free side edge (35) of each of said cuffs (28) extends under the cover sheet (46) in the vicinity of the longitudinally opposite ends of the opening (45); and said free side edge (35) at said longitudinally opposite ends of said folded portion of each cuff (28) is spaced apart inwardly of an outer edge of said base (29) of said cuff. A disposable diaper as claimed in claim 1, wherein said free side edge (35) of each cuff (28) is folded back on top of the folded portion of the collapsed cuff (28) to cover the respective elastic member (13). A disposable diaper as claimed in claim 1 or 2, wherein portions of the top- and backsheets (5,6) extend outwardly from transversely opposite side edges of the liquid-absorbent core (7) and are bonded together to define further cuffs (12) intended to surround the legs of a wearer. A disposable diaper as claimed in claim 3, wherein the further cuffs (12) have notches (20) to define respective leg-openings and elastic members (21) are bonded under their stretched condition to the respective further cuffs (12) along the notches (20). A disposable diaper as claimed in any preceding claim, wherein portions of the top- and backsheets (5,6) extend outwardly from longitudinally opposite edges (15,16) of the liquid-absorbent core (7) to define longitudinally opposite ends (17,18) of the front and rear zones (8,9). A disposable diaper as claimed in claim 5, wherein elastic members (22,23) are bonded under their transversely stretched condition to the ends (17,18) so as to fit around the waist of a wearer.

Inventors: SUEKANE MAKOTO, TANJI HIROYUKI, SUEKANE, MAKOTO, TANJI, HIROYUKI
Applicants: UNI CHARM CORP, UNI-CHARM CORPORATION
Application year: 1995
Main classification: A61F13
IPC codes: A61F13, A61F5