Disposable diaper

A diaper having front and rear waist regions and a waist-hole, the waist hole having a peripheral edge that is elastically stretchable in a circumferential direction and includes covering zones and elastic zones in the front and rear waist regions, which peripheral edge is adapted to be stretchable beyond lengths of the covering zones in the circumferential direction.

BACKGROUND OF THE INVENTION

This invention relates to a disposable diaper absorbing and containing body wastes.

Disposable diapers utilizing an inelastic or non-stretchable sheet as their topsheet and/or backsheet are well known. It is also well known in such diapers to secure elastic members under tension in circumferential directions along leg-holes and a waist-hole, respectively, to the inner surface of the topsheet and/or the backsheet and thereby to ensure a good fit of the leg-holes and the waist-hole of the wearer's skin.

In the case of such a well known diaper, a waist size of the diaper has sometimes been dimensioned to be substantially larger than an average waist size of the wearer particularly when the diaper is of the pull-on type so that the diaper may be easily put on the wearer's body with the waist-hole being adequately opened. This is true for the leg-holes. However, such dimensioning has necessarily required an amount of cloth that is much more than a sufficient amount of cloth needed to cover the wearer's legs and waist.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a disposable diaper that is designed to be easily put on the a wearer's body without excessive consumption of cloth.

According to this invention, there is provided a disposable diaper having front and rear waist regions and a crotch region extending therebetween, the diaper comprising at least one of the front and rear waist regions having an edge zone extending in a circumferential direction around a waist-hole being elastic over a full length of the edge, wherein:

the waist region comprises a covering zone formed integrally with the crotch region to position a waist region of the wearer and an elastic zone attached along an upper edge of the covering zone and adapted to be elastically stretchable in the circumferential direction and the elastic zone comprises a first member adapted to be elastically stretchable in the circumferential direction to a length beyond a length of the covering zone and a second member covering the first member, the second member being adapted to be inelastically stretchable to a length beyond the length of the covering zone and to be attached to the upper edge of the covering zone.

The disposable diaper according to this invention enables the elastic zones associated with the waist-hole to be stretched to a length substantially larger than a total length of the edges of the covering zones and thereby to open the waist-hole sufficiently to ensure that the diaper can be easily put on a wearer's body, even when the covering zones of the front and rear waist regions have no stretchability in the circumferential direction. With the diaper, it is unnecessary to dimension a circumferential dimension of the covering zones to be substantially larger than a circumferential dimension of the wearer's torso and therefore stock material required to make the diaper can be correspondingly reduced. Particularly when the rubber ribbon constituting the elastic zone is covered with a non-stretchable sheet previously formed with gathers, it is unnecessary to cover the rubber ribbon with a relatively expensive stretchable sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A disposable diaper according to this invention will be described in more details with reference to the accompanying drawings.

The disposable diaper1shown inFIG. 1in a partially cutaway perspective view is of the pull-on or shorts-type and has a front waist region6, a rear waist region7and a crotch region8extending between these two waist regions6,7. The front and rear waist regions6,7are put flat together along their respective pairs of transversely opposite side edges11,12and joined together at joining spots13arranged along the side edges11,12intermittently in a vertical direction as viewed inFIG. 1so as to form a waist-hole16and a pair of leg-holes17. An elastic member18extends circumferentially around the waist-hole16and elastic members19extend circumferentially around respective the leg-holes17. The diaper1comprises a liquid-pervious topsheet2defining the inner side of the diaper1, a liquid-impervious backsheet3defining the outer side of the diaper1and a liquid-absorbent core4disposed between the topsheet2and the backsheet3.

FIG. 2is a partially cutaway perspective view of the diaper ofFIG. 1cut open along the joining spots13and having its front and rear waist regions6,7developed apart in a direction of double-headed arrow A inFIG. 1. The front and rear waist regions6,7respectively comprise front and rear covering zones21,22adapted to cover front and rear waist regions of the wearer and front and rear elastic ones18A,18B identical in shape as well as in size provided along front and rear ends23,24of the respective covering zones21,22extending circumferentially along the waist-hole16. The crotch region8comprises a crotch covering zone26adapted to cover a crotch region of the wearer and a pair of elastic zones19provided along curved edges27of the covering zone26. The front and rear covering zones21,22and the crotch covering zone26are formed by the topsheet2, the backsheet3and the core4which are continuous longitudinally of the diaper1. The core4is hourglass-shaped and portions of the topsheet2and the backsheets3extending outward beyond a peripheral edge of the core4are put flat and joined together by means of hot melt adhesive agent (not shown).

The diaper1is assembled by putting the traversely opposite side edges11,12of the front and rear waist regions6,7flat together, then joining them together at the joining spots13and thereby an annular elastic zone18is formed by the front and rear elastic zones18A,18B. Of the front and rear elastic zones18A,18B, the rear elastic zone18B is illustrated in a state before elastic zone18B is attached to the rear covering zone22. The rear elastic zone18B comprises a rubber ribbon31which can be elastically stretched by at least 1.3 times, preferably by 2.0 times, more preferably by at least 3.0 times of a length L of the rear waist region7and a covering sheet32adapted to cover the rubber ribbon31, which covering sheet32is longer than the dimension L and stretchable at least at the stretchability of the rubber ribbon31. The number of the rubber ribbons31and their shape as well as the dimension of their cross-section are not specified. Raw material for the rubber ribbon31also is not specified and may be selected from a group including natural rubber, synthetic rubber, synthetic resin elastomer, synthetic resin elastic threads and a woven fabric made of such elastic threads, However, it is important that the front and rear elastic zones18A,18B each comprising an assembly of the rubber ribbon31and the covering sheet32should have their circumferential stretch stress preferably when they are stretched by 3˜20% lower than a stretch stress exhibited by portions of the front and rear covering zones21,22extending along the elastic zones18A,18B having the same widths as the elastic zones18A,18B. Generally, the covering sheet32is longer than the dimension L and inelastically or elastically stretched as the rubber ribbon31is elastically stretched. For example, a non-stretchable sheet longer than the dimension L is formed with gathers33undulating in the circumferential direction along the waist-hole to make this sheet substantially stretchable and this covering sheet32is attached to the rear covering zone22. Alternatively, the covering sheet32can comprise an inelastically stretchable sheet attached to the rear covering zone22so that the sheet may be stretched as the rubber ribbon31is stretched and form gathers as the rubber ribbon31contracts. It is also possible to use a covering sheet32adapted to be elastically stretched together with the rubber ribbon31.

The rubber ribbon31may be covered with a pair of covering sheets32in a sandwich fashion or covered with a covering sheet32that is cylindrically shaped adapted to receive the rubber ribbon31therein. In any case, the rubber ribbon31is secured to the covering sheet(s)32at least at longitudinally opposite ends of the rubber ribbon31or, if desired, a length of the rubber ribbon31defined between the opposite ends is intermittently or continuously bonded to the covering sheet(s)32. In a specific embodiment shown inFIG. 2, three to five pieces of synthetic rubber ribbon31each having a thickness of 0.3 mm, a width of 2.1 mm and a length of 171 mm are stretched to 400 mm and intermittently bonded to a pair of non-stretchable covering sheets32made of a spunbond nonwoven fabric and having a length of 400 mm by means of a hot melt adhesive agent (not shown) so as to cover the rubber ribbons31with the covering sheets32in sandwich fashion and thereby to obtain the rear elastic zone18B. The rubber ribbons31are relaxed so as to contract and thereby cause the sheets32to form gathers33. The rear elastic zone18B contracted to a length of 240 mm in this manner is attached to the rear covering zone22having the length L of 240 mm as measured along the waist line by suitable means such as adhesion, heat-sealing or stitching.

With the diaper1, the elastic zone18associated with the waist-hole16is stretched as indicated by the imaginary lines inFIG. 1and said waist-hole16is adequately opened so that the diaper1can be easily put on the wearer's body even when the front and rear covering zones21,22have no stretchability in the circumferential direction.

With this diaper1, in a manner similar to the elastic zone18associated with the waist-hole16, each of the elastic zones19associated with the leg-holes17should be elastically stretchable to a dimension longer than, at least by 1.3 times, preferably at least by 2 times and more preferably at least by 3 times of an actual dimension as measured along the length surrounding edge27of the crotch covering zone26. Such elastic zone19may comprise elastically stretchable rubber ribbon and a stretchable covering sheet.

As will be apparent from the foregoing description made with reference to the accompanying drawings, either both the longitudinal ends of the front and rear waist regions6,7or any one of these ends may be provided with an elastic stretchability in accordance with this invention. It is possible without departing from the scope of this invention to adjust the stretch stresses of the elastic zones18A,18B associated with the front and rear waist regions6,7to be different from each other. Well known stock materials may be used to form the topsheet2and the backsheet3and the core4. Bonding of the respective members may be performed using suitable means such as adhesions, heat-sealing or stitching.