WO1999065436A1

WO1999065436A1 - A method of fastening barrier flaps to an outer sheet for absorbent articles

Info

Publication number: WO1999065436A1
Application number: PCT/SE1999/001092
Authority: WO
Inventors: Anders Gustafsson
Original assignee: Sca Hygiene Products Ab
Priority date: 1998-06-17
Filing date: 1999-06-17
Publication date: 1999-12-23
Also published as: SE511017C2; SE9802166D0; SE9802166L

Abstract

There is provided a method of fastening an endless, elongated elastic band (1, 2) to a sheet of material (12) such that the plane of said band will be inclined relative to the plane of said sheet, and so that the perimeter of the band will include solely straight or outwardly curved parts. The method is characterised by the steps of threading the endless belt (1, 2) in a stretched state onto an anvil (10) that has a free end and whose peripheral surface corresponds to the desired configuration of straight and/or outwardly curved parts, such that one part of the band will project out beyond said free end of the anvil, wherewith the outwardly projecting part of the band contracts and therewith folds said band part inwardly around its perimeter and in against the end surface of the anvil, whereafter said inwardly folded band part is pressed against said sheet (12) and fastened thereto. The invention also relates to an arrangement for carrying out the method and to an outer sheet produced by means of the method.

Description

A METHOD OF FASTENING BARRIER FLAPS TO AN OUTER SHEET FOR

ABSORBENT ARTICLES

FIELD OF INVENTION

The present invention relates to a method and to an arrangement for fastening an endless, elastic elongated band to a sheet of material such that the plane of the band will be inclined relative to the plane of said sheet and such that the band will peripherally have solely straight or outwardly curving parts. The invention also relates to, an outer sheet provided with one such band.

BACKGROUND OF THE INVENTION

It is known, for instance, from EP-B1-0 219 326, to provide a diaper with elastic barriers that project up from the plane of the diaper or are raised from said plane, and which extend longitudinally along the diaper in spaced relationship with the side edges thereof. The purpose of these barrier flaps is to prevent liquid, or fluid, running across the outer sheet or backing sheet of the diaper and up to its side edges. The barrier flaps form together with the central part of the diaper a "container" that is able to store temporarily liquid that is discharged on one and the same occasion and which the absorbent body is unable to handle immediately. The "container" also prevents the lateral dispersion of faeces.

The barrier flaps are normally fastened to the outer sheet of the diaper while lying in the same plane as the outer sheet and will not take a raised position in relation to the outer sheet under the influence of elastic forces until the diaper is curved longitudinally as it is put onto the wearer. This method of providing raised barrier flaps is very effective in the case of longitudinal flaps, since the diaper shall have a relatively large longitudinal curvature when worn, so as to conform to the contours of the wearer's body. However, this barrier flap fastening method is not as effective in respect of transversely extending barrier flaps, since transverse curvature of the diaper is relatively slight in the front and rear diaper parts, where transverse barriers are desirable. Consequently, there is a need of being able to fasten barrier flaps to an outer sheet with the barrier flaps raised or upstanding already at the moment of fastening said flaps. The object of the present invention is to satisfy this requirement and to provide a one-piece barrier flap which extends both longitudinally and transversely on a sheet of material.

SUMMARY OF THE INVENTION

To this end, there is proposed in accordance with the invention a method of fastening an endless, elastic elongated band to a sheet of material such that the plane of the band will be inclined relative to the plane of said sheet and such that the band periphery will have solely straight or outwardly curving parts, said method being characterised by threading the endless band in a stretched state on an anvil or counterpressure means that has a free end and a periphery that has the desired form of straight and/or outwardly curved parts, such that a part of the band will project out beyond the free end of the anvil, wherewith the outwardly projecting part of the band contracts so that this part of the band will be folded in around its perimeter against the end surface of said anvil, and thereafter pressing the band part that has been folded in against the end surface of the anvil against said sheet of material and fastening said part thereto. This procedure enables a barrier flap which in a raised state forms a closed loop on a part of a sheet of material to be obtained in a particularly simple manner. The method is also suitable for fastening barrier flaps to a moving web of material and can therefore be readily integrated in an absorbent article production line without having a disturbing effect on the manufacturing process.

In one preferred embodiment of the invention, the part of the band that has been folded in on the anvil is fastened to said sheet of material by heat welding or ultrasonic welding, or may be glued to said sheet.

The invention also relates to arrangement for fastening an endless, elastic elongated band to a sheet of material such that the plane of the band will be inclined relative to the plane of the sheet and such that the band perimeter will have solely straight or outwardly curved parts. The arrangement is characterised by an anvil or counterpressure means that has a free end and a peripheral surface that includes the desired configuration of straight and/or outwardly curved parts; means for threading the band in a stretched state onto the free end of the anvil so that a part of the band will project outwardly beyond said free end, wherewith the outwardly projecting part of the band contracts so as to fold this part of the band around its periphery against the end surface of the anvil; means for pressing a sheet of material against that part of the band that has been folded inwardly on the end surface of the anvil; and means for fastening to said sheet that part of the band that has been pressed thereagainst.

In one preferred embodiment of the invention, that part of the band which pressed against said sheet is fastened thereto with the aid of heat welding or ultrasonic welding means, although it may alternatively be glued thereto. The devices for threading, or passing, the band over the anvil comprise two flat collector plates which have a width corresponding to the greatest width of the anvil and which, when the planar sides of the plates face towards each other, are spaced apart at a distance which is greater than the length of said anvil. The arrangement also includes means for advancing two elongated, stretched elastic webs of material in mutually superimposed and mutually spaced relationship; means for joining the webs together along transverse join lines; means for inserting the collector plates in between the two webs of material and between two transverse join lines with the plates disposed in a first position in which their planar sides lie in mutually the same plane; means for cutting the webs on both sides of the transverse join lines between which the plates are disposed in their first position; means for turning the plates between said first position to a second position in which their planar sides face towards each other, and vice versa; and means for moving the collector plates and the elastic band supported thereon across the anvil.

The invention also relates to a diaper outer sheet, an incontinence protector or a sanitary napkin which is characterised in that it includes an endless elastic band having two opposing edges and fastened to the outer sheet at one edge part and extending around a part of said outer sheet with a peripheral configuration that includes solely straight and/or outwardly curving parts.

In one preferred embodiment, the elastic band is comprised of an endless strip of flexible material that includes a pre-stretched elastic element along each of said mutually opposing edges.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings, in which

Fig. 1 illustrates two elastic bands included in an arrangement for fastening a barrier flap to a sheet of material in accordance with one preferred embodiment of the invention;

Fig. 2 is a highly schematic view from above of a first part of an arrangement according to a preferred embodiment of the invention;

Fig. 3 illustrates from above collector plates included in the arrangement shown in Figure 2;

Fig. 4 illustrates a second part of the arrangement that coacts with the first part shown in Figure 2;

Fig. 5 is a cross-sectional view taken on the line V-N in Figure 4;

Fig. 6 is a cross-sectional view taken on the line NI-NI in Figure 4;

Fig. 7 is a view similar to the view of Figure 3 and illustrates a second embodiment of collector plates; and

Figs- 8-10 illustrates from above diapers that include different barrier flaps.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 shows two flexible bands 1 and 2, e.g. bands of plastic film. Stretched elastic threads 3, 3' are fastened to respective opposing edges of respective bands.

Figure 2 is a schematic illustration of part of an arrangement for providing an outer sheet with barrier flaps. The bands 1 and 2 run through the Figure 1 arrangement in the arrowed direction. The bands 1, 2 are advanced whilst being spaced slightly apart, as shown in Figure 1. The bands first pass a joining device 4, e.g. an ultrasonic welding device, in which the bands 1, 2 are mutually joined by means of separate pairs of transverse welds 5. Rectangular collector plates 6, 7 are then inserted between the bands 1, 2 and between two mutually sequential pairs of transverse welds 5. After being inserted between the bands, the collector plates 6, 7 are moved in the same direction and at the same speed as the bands. The arrangement includes several pairs of collector pairs 6, 7, of which two pairs are shown in Figure 2. It will be seen from Figure 2 that the bands 1, 2 are cut transversely between the two weld seams 5 in each pair of welds immediately after the upstream collector plate 6, as seen in the feed direction, has passed a cutting tool 8 of some suitable kind, e.g. a punch. There is thus formed an endless elastic band from the two cut portions of the bands 1, 2. Immediately after cutting the bands, the two collector plats 6, 7 are turned through 90° from the insertion position, in which their broad sides lay in the same plane, so as to cause said broad sides to face towards each other. The sides of the endless band consisting of portions of the bands 1, 2 are thereby distanced from one another, as will be evident from Figure 3 which shows from above the right-hand pair of collector plates 6, 7 in Figure 2. This rotation of the collector plates is achieved by connecting the plates to suitable turning devices, such as the output shafts of stepping motors, for instance.

Figure 4 is a schematic illustration of a second part of the arrangement. A row of mutually separated pairs of collector plates 6, 7 carrying endless bands 1, 2 are advanced in the upper part of the second part of the arrangement shown in the Figure, in the arrowed direction. The rows of collector plate pairs 6, 7 pass a rotating anvil roll 9 that has six anvils 10 projecting out from its periphery. These anvils penetrate sequentially in between the sides of the endless belts 1, 2 carried by the collector plate pairs 6, 7. As an anvil 10 penetrates between two collector plates 6, 7, the free sides of the band carried by said plates is pressed firmly against the sides of the anvil, for instance by means of clamps not shown, and the collector plates 6, 7 are drawn upwards with the aid of the same mechanism as that which previously inserted said plates in between the bands 1, 2 shown in Figure 2. The endless band 1, 2 will therewith be transferred to the anvil 10. The clamps are loosened immediately the collector plates have been withdrawn. The collector plates and the means for rotating and displacing said plates are conveniently mounted on an endless conveyor so that said means can take-up a further endless belt after said band has been transferred to said anvils, in the same manner as that described above with reference to Figure 2. The anvils 10 are designed so as not to reach the upper edge of the band 1, 2 carried by the collector plate 6, 7, but so that the band will project out beyond the end surface of the anvil 10 upon completion of the band transfer. This allows the elastic thread 3 provided along the free band edge to contract from its stretched state. This contraction is made possible, by folding the free edge-part of the band 1, 2 in over the upper side of the anvil 10, as will best be seen from Figure 5. In order to ensure that the elastic thread 3 is unable to draw band material from the side surfaces of the anvil to its end surface, the tensioning force in the threads 3' will be equal to or greater than the tensioning force in the threads 3. The threads 3 will conveniently have relatively low tension, so that said thread will be able to contract as the free edge-part of the band 1, 2 is folded-in, principally in a relaxed state. This will prevent the thread from loading the sheet of material to any appreciable extent subsequent to fastening the band to said sheet. It is also possible to "kill" the elasticity of the thread when heat welding or ultrasonic welding the inwardly folded edge part of the band. It is, of course, also possible to give the threads 3 a relatively high tension, so that its residual tension will load the sheet of material subsequent to fastening the band thereto and therewith pucker sheet and cause an underlying absorbent body to curve. The anvils 10 are intended to coact with an ultrasonic horn 11 included in an ultrasonic welding unit not shown. A web of material 12 is advanced between said horn 11 and the anvil roll 9 in the arrowed direction. When the anvil 10 carrying the band 1, 2 has reached the position in which the anvil coacts with the ultrasonic horn 11, the ultrasonic welding unit is activated and the inwardly folded edge of the elastic band carried by the anvil is welded firmly to said sheet of material. Because the direction in which said sheet is advanced differs from the direction in which the anvil moves, the anvil will then be drawn out of the band fastened to said sheet. When the anvil has left the band 1, 2, the threads 3' will contract and therewith cause the sides of the band to slope towards each other and define an acute angle with the plane of said sheet, as will best be seen from Figure 6. This procedure results in a sheet of material that includes barrier flaps.

The barrier-flap carrying sheet 12 is then passed to a production line for the manufacture of absorbent articles, such as diapers, incontinence protectors or sanitary napkins. Because the aforedescribed barrier flap fastening method enables the barrier flaps to be fastened to a moving web of material, the method can be readily incorporated in such a production line without interfering with remaining parts of the manufacturing process. The geometry of the barrier flaps produced by the described method is determined entirely by the geometry of the anvil. Any geometric configuration that includes solely straight and/or outwardly curved parts can be achieved, for instance rectangular shapes, square shapes, hexagonal shapes, circular shapes, oval shapes, etc. The method is thus extremely flexible and the described arrangement can be readily modified to shift between different shapes of the barrier flaps produced. All that is required is to change the anvil roll.

Figure 7 is a view similar to that of Figure 3 and illustrates collector plates 6', T which differ from the earlier described plates 6, 7 by virtue of having curved planar surfaces. Such a design can be desirable in some instances in order to adapt the geometric figure formed by the band carried by the plates to the shape of the anvil.

Figures 8-10 are respective views from above of a diaper provided with different barrier flaps. The diaper is typically comprised of an absorbent body 13 enclosed between a liquid-impermeable outer sheet and a liquid-permeable outer sheet 14. Barrier flaps 15, 16 and 17 have been fastened to the outer sheet 14 of the illustrated diapers by means of the aforedescribed method. The geometric figure formed by the barrier flaps 15 in the Figure 8 illustration consist of two longitudinal straight parts which are interconnected by two transverse, outwardly curved parts. The barrier flaps 16 in the Figure 9 illustration have an oval configuration, while the diaper shown in Figure 10 has two circular barrier flaps 17.

It will be understood that the described and illustrated embodiments can be modified within the scope of the invention, particularly with respect to the design of the anvils and their number. The elastic bands may also be constructed in a manner different to that shown, for instance may be made totally of elastic material. The join lines may be achieved by heat welding or by gluing as an alternative to ultrasonic welding. The invention is therefore only restricted by the contents of the following Claims.

Claims

1. A method of fastening an endless, elongated elastic band (1, 2) to a sheet of material (12) such that the plane of said band will be inclined relative to the plane of said sheet, and so that the perimeter of the band will include solely straight or outwardly curved parts, characterised by the steps of threading the endless belt (1, 2) in a stretched state onto an anvil (10) that has a free end and whose peripheral surface corresponds to the desired configuration of straight and/or outwardly curved parts, such that one part of the band will project out beyond said free end of the anvil, wherewith the outwardly projecting part of the band contracts and therewith folds said band part inwardly around its perimeter and in against the end surface of the anvil, whereafter said inwardly folded band part is pressed against said sheet (12) and fastened thereto.

2. A method according to Claim 1, characterised in that the band part (1, 2) that is folded inwardly on the anvil (10) is heat welded or ultrasonically welded to said sheet (12).

3. A method according to Claim 1, characterised by gluing the band part that is folded inwardly on the anvil to said sheet.

4. An arrangement for fastening an endless, elongated elastic band (1, 2) to a sheet of material (12) such that the plane of the band will be inclined relative to the plane of said sheet and such that the perimeter of said band will have solely straight or outwardly curved parts, characterised in that the arrangement includes an anvil (10) that has a free end and a peripheral surface which has the desired configuration of straight and/or outwardly curved parts; means (6, 7) for threading the band in a stretched state on said free end of the anvil (10) such that a part of the band (1, 2) will project out beyond said end, wherewith the outwardly projecting band part contracts so that the perimeter of said band part will be folded in against the end surface of said anvil; means (11) for pressing a sheet of material (12) against that part of the band which has been folded in on the end surface of the anvil (10); and means (11) for fastening to the sheet of material that part of the band which has been pressed thereagainst.

5. An arrangement according to Claim 4, characterised in that the means (11) for fastening to the sheet (12) that part of the band (1, 2) that has been pressed thereagainst have the form of heat welding or ultrasonic welding devices.

6. An arrangement according to Claim 4, characterised in that the means for fastening to the sheet of material that part of the band which has been pressed thereagainst is comprised of a gluing unit.

7. An arrangement according to any one of Claims 4-6, characterised in that the means for threading the band (1, 2) across the anvil (10) comprises two planar collector plates (6, 7) whose widths correspond to the greatest width of the anvil, said collector plates being spaced apart at a distance that is greater than the length of the anvil when the planar sides of the plates face towards each other.

8. An arrangement according to Claim 7, characterised by means for advancing two elongated and stretched elastic webs of material (1, 2) in mutually superimposed and slightly spaced relationship; means for joining together said two webs along transverse join lines (5); means for inserting the collector plates (6, 7) between said two webs (1, 2) and between two transverse join lines (5) with the plates (6, 7) disposed in a first position in which their planar sides lie in mutually the same plane; means (8) for cutting the webs on both sides of the two transverse join lines (5) between which the plates are disposed in their first position; means for turning the plates between the first position to a second position in which their planar sides face towards each other; and means for moving the collector plates and the elastic band (1, 2) carried thereby over said anvil (10).

9. An outer sheet for a diaper, incontinence protector or a sanitary napkin, characterised by an endless elastic band (15; 16; 17) which has two mutually opposing edges and which is fastened to said outer sheet (14) at one of said parts and which extends around a part of the outer sheet with a peripheral portion that includes solely straight and/or outwardly curving portions.

10. An outer sheet according to Claim 9, characterised in that the elastic band (15; 16; 17) comprises an endless flexible strip (1, 2) that has a pre-tensioned elastic element (3, 3') along each opposing edge.