GB2296467A

GB2296467A - Composite outer sheet and absorbent sheet for absorbent articles

Info

Publication number: GB2296467A
Application number: GB9525199A
Authority: GB
Inventors: Bengt Lindquist; Stefan Areskoug
Original assignee: Molnlycke Vafveri AB
Current assignee: Essity Hygiene and Health AB
Priority date: 1994-12-30
Filing date: 1995-12-07
Publication date: 1996-07-03
Also published as: TR199501717A1; CO4520223A1; TNSN95144A1; GB9525199D0; SE9404580L; SE9404580D0; AU4403996A; SE508406C2; WO1996020672A1; ZA9510627B

Abstract

Shape-stable, perforated recesses are produced in a web (12) of casing material and an adjacent web (14) of absorbent material by perforating the web (12) of the casing material by a large number of discrete cuts on a matrix cylinder (16), and the web (14) of absorbent material comprised of separate lengths (30) is combined with the perforated web (12) of casing material and is pressed partially together with the web (12) of casing material into hollows or depressions (34, 36) in the matrix cylinder (16). The matrix cylinder (16) includes a large number of circumferential rows of raised plateaus (26) which are separated in the circumferential direction. The apparatus also includes a cutting cylinder (18) which coacts with the matrix cylinder (16), and a press cylinder (20). Alternatively webs (12) and (14) may be first combined prior to the perforation and deformation steps. <IMAGE>

Description

Casing material and a method and apparatus for its manufacture The present invention relates to a method and to apparatus for use in the manufacture of absorbent articles, such as sanitary napkins, diapers and like articles, and particularly for producing shape-stable perforated recesses in a web of casing material. The inwardly facing perforated outer or casing sheet of absorbent articles normally includes a liquid-impermeable material, such as plastic film, wherein the holes formed by the perforations are very large in number so as to enable liquid, or fluid, to flow satisfactorily into the absorbent body of the article that lies inwardly of the outer casing sheet.

In the case of outer casing sheets of this kind it is also desirable to obtain a relatively small area of contact of the casing sheet with the wearer's body, so as to produce an inwardly facing casing sheet which will be felt to be more airy, drier and less plastic-like by the wearer. This is achieved by forming recesses in the web from which the outer sheet is produced, wherein the holes are preferably orientated in planes which lie generally perpendicular to the plane of the outer sheet. Providing that the outer sheet is comprised of opaque material, this orientation of the holes also affords the advantage that the body liquid absorbed by the absorption body will be less visible.

SE-B-44 9 298 (corresponding to US-A-4 626 254) describes and illustrates an inner outer sheet for absorbent articles in which perforated recesses are formed in the outer sheet, wherein the recesses include openings or holes which are orientated in planes that lie generally perpendicular to the plane of the outer sheet.

Our patent application SE-A-9404579-6, filed on the same date as the present invention, describes a method and an apparatus for facilitating controlled, more uniform and well-defined forming of the recesses and the holes made therein.

When such perforated outer casing material is used together with relatively hard and smooth absorbent body materials it may be difficult to achieve good contact between the casing material and the absorbent material, thereby making it difficult for the liquid that shall be led into the absorbent material through the holes in the recesses formed in the outer sheet material to penetrate into or be drawn by suction into the absorbent material in the manner desired. This may be because the recesses in the casing sheet material are subjected to pressure and therewith flattened in the process of laminating the casing sheet with the absorbent material and/or during use of the finished article, so as to completely or partially close the holes in the recesses.

One object of the present invention is to provide a method and apparatus which eliminate the risk of the holes becoming blocked and which will create close contact between the absorbent material and the open holes in the casing sheet material and therewith stiffen the recesses so as to facilitate penetration of liquid into the absorbent material.

To this end, the inventive method is characterized in that a web of material intended for forming the inner casing sheet of the article that is intended to lie proximal to the wearer in use, is perforated with a large number of mutually discrete cuts on a matrix cylinder or drum as the web is advanced; and in that a web of absorbent material is combined with the perforated casing material web on the side thereof remote from the matrix cylinder and is pressed at least partially together with the web of casing material into hollows or indentations in the matrix cylinder and form a composite web of casing and absorbent material which includes shape-stable, perforated recesses.

According to one alternative embodiment of the inventive method, however, the web from which the casing sheet is produced is first combined with the web of absorbent material and the webs are perforated together after having been combined and prior to the thus formed laminate being deformed transversely to its plane so as to form a composite casing and absorbent material web which includes shape-stable, perforated recesses.

The inventive apparatus is mainly characterized in that it includes a matrix drum which includes a large number of discrete, raised plateaus which extend circumferentially in rows: a cutting drum or cylinder which includes circumferentially disposed knife-edges which are disposed so as to generally touch respective plateaus on the matrix drum, such as to cut intermittently the web of casing material advanced in the nip between the knife-edges and the plateaus, and a press cylinder which is mounted downstream of the cutting cylinder and which functions to press the web of casing material and the web of absorbent material at least partially into the hollows in the matrix drum, these hollows being formed by circumferentially extending grooves between the rows of plateaus.

The present invention also relates to a combined casing sheet and absorbent sheet for absorbent articles such as sanitary napkins, diapers and like articles, where the casing sheet is intended to lie proximal to the wearer's body in use, wherein the combined casing sheet and absorbent sheet laminate is characterized in that common recesses are formed in the casing sheet and in the absorbent sheet, wherein the recesses in the casing sheet are provided with holes in at least one side wall orientated generally perpendicular to the plane of the composite sheet.By combining the casing sheet with the absorbent sheet and providing common recesses in said sheets, the stiffer absorbent material may, among other things, be used to shape-stabilize the recesses and the holes in the casing sheet, so that these recesses and holes will be less likely to deform when pressure is exerted in a direction perpendicular to the plane of the composite sheet. The close contact achieved between the casing material and the absorbent material in the regions surrounding the recesses and the holes also enables the casing sheet material and absorbent material to be held together without the aid of glue.

Suitable embodiments of the inventive method and apparatus will now be described in more detail together with further features thereof with reference to the accompanying drawings, in which Figure 1 is a schematic, perspective view of inventive apparatus for perforating a web of casing material and for integrating said web with a web of absorbent material, and also shows the matrix drum and cutting cylinder of the apparatus in fragmentary enlarged views; Figure la is a fragmentary perspective view of a modification to the positioning of the cog-like pegs on the matrix drum; Figure 2 is a schematic side view of the cylinder arrangement in the apparatus of Figure 1; Figure 3 is a fragmentary cross-sectional view which illustrates cutting of a web of casing material in a nip between the matrix cylinder and the cutting cylinder; ; Figure 4 is a fragmentary cross-sectional view which illustrates partial pressing of the absorbent-material web and the perforated casing web into hollows in the matrix cylinder in a nip between the latter and a press cylinder, wherein the plane of the web of casing material is displaced and perforated recesses are formed by plastic deformation across the pegs on the matrix cylinder; Figure 5 is a view similar to Figure 4 and illustrates an alternative design of the pegs on the matrix cylinder and also shows the web of absorbent material and the perforated web of casing material pressed into the nip between the matrix cylinder and the press cylinder; Figure 6 is a schematic side view of an alternative embodiment of the inventive apparatus, in which the absorbent material is co-perforated with the web of casing material;; Figure 7 illustrates a sector-shaped mantle part and a fragmentary part of the ribs of a modified embodiment of the matrix cylinder; Figure 8 is a fragmentary view of a row of perforated recesses in a hammock-like configuration and produced by means of the apparatus of the embodiment illustrated in Figures 1-4; Figure 9 is a fragmentary view of a row of perforated recesses of eyelid-like configuration, produced by means of matrix cylinder having pegs according to the Figure 5 embodiment; Figure 10 illustrates elongated channel-like or groove-like recesses in a composite web consisting of casing sheet material and absorbent material and formed by a matrix cylinder in accordance with the Figure 7 embodiment;; Figure 11 illustrates elongated channel-like or groove-like recesses in a composite comprised of casing sheet material and absorbent material and formed by a matrix cylinder similar to the cylinder in Figure 7 but with matrix ribs whose crosssectional shapes correspond to the cross-sectional shapes of the pegs in Figure 5; and Figure 12 is a fragmentary cross-sectional view taken through an integrated casing sheet web and absorbent-material web having perforated recesses of the kind illustrated in Figure 9 and produced by means of matrix pegs having the form shown in Figure 5.

Figure 1 illustrates inventive apparatus, generally referenced 10, for producing an integrated casing sheet web 12 and an absorbent-material web 14 for the manufacture of absorbent articles, such as sanitary napkins, diapers and like articles, wherein the casing sheet web 12 is intended to form on the finished article the outer casing sheet that lies proximal to the wearer's body in use, whereas the absorbent-material web 14 is intended to form the whole of or at least a part of the absorbent body or core of the finished article. The web 12 may, for instance, consist of plastic film or a plastic film and nonwoven laminate, in which latter case the plastic layer or sheet will form the surface that is in contact with the wearer of the article.The apparatus 10 is constructed to perforate the web 12 with a large number of discrete cuts which are orientated essentially in the longitudinal direction of the web, and thereafter to form in both the casing material and the absorbent material recesses which include holes formed in a plane which lies generally perpendicular to the casing sheet. To this end, the apparatus 10 includes a matrix cylinder or drum 16, a cutting cylinder or drum 18 and a press cylinder 20, these cylinders being rotatably mounted in a stand 22 and capable of being adjusted mutually for adequate alignment relative to one another.In the embodiment according to Figure 1, the matrix cylinder 16 includes a large number of peripherally extending, axially separated rows of generally cog-like pegs 24 which have curved top surfaces and which form raised plateaus 26 against which the circular knife-edges 28 of the cutting cylinder 18 are intended to lie or generally touch, so as to form a large number of cuts in the longitudinal direction of the web 12 as said web passes through the nip defined between the matrix cylinder 16 and the cutting cylinder 18, as shown more clearly in Figure 3. In this case, the knife-edges 28 on the cutting cylinder 18 are intended to cut the web 12 at side-edge parts of the pegs plateaus 26 and therefore has twice the number of knife-edges 28 as the number of rows of pegs 24.

Figure la illustrates a modified embodiment of the matrix cylinder 16 in which the pegs 24 in adjacent rows of pegs are mutually offset in the circumferential or row direction, thereby enabling the elastic properties of the later impressed or imprinted and combined web of material to be varied (increased) in an appropriate manner as desired.

The web 14 of absorbent material is comprised of discrete, separate lengths 30 of absorbent material of a known kind, having a width which is preferably smaller than the width of the web 12 of casing material. These lengths 30 are fed to the apparatus 10 on an endless conveyer belt 32 and are introduced into the nip defined between the matrix cylinder 16 and the press cylinder 20 on the side of the cut web 12 that lies distal from the matrix cylinder 16, as shown more clearly in Figure 2.

In the illustrated case, the press cylinder 20 has a smooth cylindrical mantle surface (Figures 4 and 5) and functions to press parts of the advanced absorbent material 30 and the casing sheet material 12 into hollows or indentations in the matrix cylinder 16. These hollows are formed by the grooves 34 between the rows of pegs 24 and of the peg interspaces 36.

As the web of casing material 12 and the absorbent material 30 pass together through the nip defined by the matrix cylinder 16 and the press cylinder 20, as shown in Figure 4, shape-stable imprints or impressions are obtained in the form of recesses 38 in the casing sheet material and absorbent material, wherein the casing sheet material obtains in the embodiment of Figures 1-4 a hammock-like shape with two mutually opposing hole openings 40 located in a plane generally perpendicular to the plane of the casing sheet, as shown in Figure 8. As a result of this simultaneous imprinting of the casing sheet material and the absorbent material, extremely good contact is obtained between the two materials, which ensures good shape-stability of the perforated recesses 38, which are able to take-up pressure loads without being deformed and closed.

Figure 5 illustrates an alternative embodiment of the matrix pegs, here referenced 24', where one side wall 42 of the pegs - seen in an axial cross-section through the matrix cylinder - is curved convexly to form a ridge-like formation 44 at the opposite side edge of the peg 24'. When this embodiment is used to cut the web 12, only one knife-edge 28 is required for each peg 24'. The recesses 38' formed when pressing casing sheet material and absorbent material into the recesses in the matrix cylinder 16 by means of the press cylinder 20 there is obtained an eyebrow-like shape with only one hole opening 40 orientated generally perpendicular to the integrated webs 12, 30, as shown in Figures 9 and 11. Although recesses 38' of this configuration will result in a smaller total hole area of the casing sheet material, the shapestability of the recesses is improved.

Figure 6 illustrates an alternative embodiment of the inventive apparatus, in which the web 14 of absorbent material is advanced on a conveyer 45 and combined with the casing sheet web 12 upstream of the nip between the matrix cylinder 16 and the cutting cylinder 18, wherein both webs 12, 14 are perforated together. This may be suitable when, for instance, the web of absorbent material is relatively thin and may later be laminated with further layers or sheets of absorbent material downstream of the apparatus 10.

Figure 7 illustrates part of a further embodiment of an inventive matrix cylinder 16'. Distinct from the pegs 24, 24' of the embodiments illustrated in Figures 1-5, the matrix cylinder 16' has circumferentially extending ribs 46 which when seen in axial cross-section through the matrix cylinder have a configuration corresponding to the pegs 24 of the Figure 4 embodiment. Located along the cylindrical mantle surface of the ribs 46 are a number of circumferentially spaced, raised plateaus 26' which correspond to the tops of the pegs 24. However, the mutually adjacent plateaus 26' are not separated in the circumferential direction by peg interspaces as in the case of the pegs 24.As a result, those hollows that are formed in the integrated webs 12, 30 as the pressure cylinder 20 presses against the matrix 16' will have an elongated channel-like groove configuration 38", as shown in Figure 10 with an increased hole area and a smaller contact surface against the wearer's body. The grooves 38" are delimited by two mutually opposing side walls 39a, in which the holes 40 are formed, and a bottom wall 39b. The groove configuration of the recess 38" shown i Figure 11 is obtained when the cross-sectional shape of the matrix ribs 46 corresponds to the cross-sectional shape of the pegs 24' of the Figure 5 embodiment. In this case, the grooves 30''' are delimited by a side wall 39a' and a sloping bottom wall 39b'.

The matrix cylinder 16' may include continuous circumferential ribs as shown in Figure 7, or ribs 46 which include pegspacing interruptions or hollows 48 which give each rib 46 the form of a sector having a plurality of plateaus 26'. One such sector having twenty plateaus 26' is shown in Figure 7, this sector constituting one tenth of the circumference of the complete matrix cylinder 16'.

As a result of the interruptions 48 in the ribs 46 the finished perforated and recessed composite material web 12, 30 will include cross-bars 50 (Figures 10 and 11) which stabilize the finished material so that said material will have a suitable stretch resistance transversely to the formed groove-like recesses. These cross-bars 50 prevent the side walls of the grooves from being parted or brought together, which is an undesirable occurrence.

It is also possible within the scope of the present invention to use a press cylinder which, similar to the embodiment according to Figure 3 and 4 of our above mentioned patent application filed on the same date as the present application, presents some appropriate form of press ribs which facilitate pressing of parts of the absorption material into the recesses in the matrix cylinder.

In the case of the embodiment illustrated in Figures 1-5, it is also possible to fix the lengths 30 of absorption material on a web of casing-sheet, liquid-impermeable material (not shown) prior to being combined with the web of casing material 12, wherein edge sealing and cutting of finished articles can be carried out immediately after imprinting the perforated recesses. Good edge sealing is achieved when the casing web 12 is perforated solely over a width which corresponds approximately to the width of the web of absorption material 14.

Claims

1. A method in the manufacture of absorbent articles, such as sanitary napkins, diapers and like articles, characterized in that a web of material (12) which is intended to form an inner article-casing sheet which lies proximal to the wearer in use is perforated with a large number of discrete cuts on a matrix cylinder (16; 16') as the web is advanced; and in that a web (14, 30) of absorbent material is combined with the perforated web of casing material (12) on the side thereof that lies distal to the matrix cylinder (16; 16') and is pressed at least partially together with the web of casing material (12) into hollows (34, 36) in the matrix cylinder so as to form an integrated casing-material and absorption-material web which includes shape-stable perforated recesses (38; 38'; 38").

2. A method according to Claim 1, characterized in that the web (14) of absorbent material is formed from separate lengths (30) of absorption material.

3. A method according to Claim 1 or Claim 2, characterized in that the web (12) of inner casing material is broader than the web (14) of absorbent material and is perforated over a width which corresponds generally to the full width of the web (14) of absorption material while leaving imperforate side-parts on the web (12) of casing material.

4. A method according to any one of Claims 1-3, characterized in that the absorption material (10) is fastened to a web of liquid-impermeable, casing material on the side thereof which lies distal to the web (12) of inner casing material prior to the absorption material being combined and integrated with the inner perforated web of casing material.

5. A method according to any one of Claims 1-3, characterized in that the webs (12, 14) are so pressed in the matrix cylinder (16; 16') that the holes (40) in the recesses (38; 38'; 38") will be orientated in planes which lie generally perpendicular to the plane of the webs.

6. A method in the manufacture of absorbent articles such as sanitary napkins, diapers and like articles, characterized in that a web of material (12) which is intended to form an inner article casing sheet which faces inwardly towards the wearer in use and a web (14, 30) of absorbent material are combined and perforated with a large number of discrete cuts on a matrix cylinder (16); and in that the thus combined webs are deformed transversely to their planes at least at parts which border on the sides of each cut, by pressing parts of the webs (12, 14, 30) into hollows (34, 36) in the matrix cylinder (16) so as to form an integrated casing-web and absorption-material web which has shape-stable, perforated recesses (38; 38'; 38").

7. A method according to Claim 6, characterized in that the web (14) of absorbent material is formed from separate lengths (30) of absorbent material.

8. A method according to Claim 6 or Claim 7, characterized in that the web (12) of inner casing material is broader than the web (14) of absorbent material; and in that the webs are perforated over a width which corresponds generally to the full width of the web (14) of absorbent material, while leaving imperforate side parts on the web of casing material.

9. A method according to any one of Claims 6-8, characterized in that the absorbent material (30) is fastened to a web of liquid-impermeable casing material on the side thereof that lies distal to the inner casing-material web (12) subsequent to having perforated the webs of inner casing material and absorbent material.

10. A method according to any one of Claims 6-9, characterized in that the material webs (12, 14) are so pressed into the matrix cylinder (16) that the holes (40) in the recesses will be orientated in planes which lie generally perpendicular to the planes of the webs.

11. Apparatus for producing shape-stable, perforated recesses (38; 38'; 38") in a web (12) of casing material and an adjacent web (14) of absorbent material, characterized in that the apparatus includes a matrix cylinder (16; 16') which includes a large number of circumferentially extending rows of raised peripherally separated plateaus (26, 26') ; a cutting cylinder (18) which includes circumferentially extending knife-edges (28) which are intended essentially to touch respective plateaus (26; 26') on the matrix cylinder (16; 16') so as to cut intermittently the web (12) of casing material advanced in the nip between the knife-edges and the plateaus; a press cylinder (20) which is located downstream of the cutting cylinder (18) and which functions to press parts of the casing material web (12) and the absorption material web (14) into hollows (34, 36) in the matrix cylinder (16; 16'), these hollows comprising circumferential grooves (34) between the rows of plateaus (26; 26').

12. Apparatus according to Claim 11, characterized by means (32) for combining the web (14) of absorbent material with the web (12) of casing material on the upstream side of a nip defined between the matrix cylinder (16; 16') and the press cylinder (20).

13. Apparatus according to Claim 11 or Claim 12, characterized by means (45) for combining the web (14) of absorbent material with the web (12) of casing material on the upstream side of the nip defined between the matrix cylinder (16) and the cutting cylinder (18).

14. Apparatus according to any one of Claims 11-13, characterized in that the raised plateaus (26) are formed on the tops of generally cog-like pegs (24).

15. Apparatus according to Claim 14, characterized in that the plateaus are formed by a ridge-like formation (44) along one side edge of the peripheral surface of respective pegs (24').

16. Apparatus according to Claim 15, characterized in that one side (42) of each peg (24') has a convex curved shape when seen in axial cross-section through the matrix cylinder.

17. Apparatus according to Claim 16, characterized in that the other side of each peg (24') is orientated generally radially.

18. Apparatus according to any one of Claims 11-13, characterized in that the plateaus have the form of raised parts (26') on circumferential ribs (46) on the matrix cylinder (16').

19. Apparatus according to Claim 18, characterized in that both sides of each rib (46) are orientated generally radially, as seen in an axial cross-section through the matrix cylinder (16').

20. Apparatus according to Claim 18, characterized in that one side of each rib has a convex curved shape when seen in an axial cross-section through the matrix cylinder (16').

21. Apparatus according to any one of Claims 18-20, characterized in that the circumferential ribs (46) with raised parts (26') include several discrete circumferential interruptions (48) in the form of hollows, there being formed between two mutually adjacent hollows (48) in the circumferential direction a plateau row sector which includes a plurality of raised parts (26').

22. Apparatus according to Claim 14 or Claim 19, characterized in that the cutting cylinder (18) includes continuously circular knife-edges (28) whose number is twice that of the rows of plateaus (26) on the matrix cylinder (16), wherein each knife-edge essentially touches one side-edge part of each plateau (26).

23. Apparatus according to any one of Claims 15-17 or Claim 20, characterized in that the cutting cylinder (18) includes continuously circular knife-edges whose number corresponds to the number of rows of plateaus (26') on the matrix cylinder.

24. Apparatus according to any one of Claims 11-23, characterized in that the press cylinder (20) is smooth.

25. Apparatus according to any one of Claims 11-24, characterized in that the cylinders (16, 18, 20) are journalled in a common stand (22).

26. Apparatus according to any one of Claims 11-25, characterized in that the matrix cylinder (26) is fixedly journalled, whereas the cutting cylinder (18) and the press cylinder (20) are journalled so as to be radially adjustable in relation to the matrix cylinder (16) in the stand (22).

27. A composite outer sheet and absorbent sheet for absorbent articles such as sanitary napkins, diapers and like articles, in which the outer sheet (12) is intended to lie proximal to the wearer's body in use, characterized in that common recesses (38; 38'; 38"; 38''') are formed in the casing sheet (12) and in the sheet of absorbent material (30), wherein holes (40) are formed in the recesses in the casing sheet in at least one side wall (39a; 39a') orientated generally perpendicular to the plane of the composite sheet.

28. An casing sheet according to Claim 27, characterized in that the recesses have the form of short hollows (38; 38') which lie closely separated across the surface of said sheet.

29. An casing sheet according to Claim 27, characterized in that the recesses have the form of mutually adjacent, longitudinally extending groove-like hollows (38"; 38''').

30. An casing sheet according to Claim 29, characterized in that the groove-like hollows (38''') include a longitudinally extending side wall (39a') which is orientated generally perpendicular to the plane of the composite sheet, and a sloping bottom wall (39b') which adjoins the side wall, stho hn side wall has a large nllohor of holes (405 formed therein.

31. An casing sheet according to Claim 29, characterized in that the groove-like hollows (38") have two mutually opposing and longitudinally extending side walls (39a) which are orientated generally perpendicular to the plane of the composite sheet, and a bottom wall (39b) which joins the side walls, wherein each of the side walls (39a) has a large number of holes (40) formed therein.

32. An casing sheet according to any one of Claims 29-31, characterized in that the groove-like hollows are continuous.

33. An casing sheet according to any one of Claims 29-31, characterized in that the groove-like hollows (38"; 38''') include interruptions (50) which are spaced mutually apart along the grooves and which form cross-bars in the composite casing sheet and delimit the lengths of the grooves, wherein each groove length includes a plurality of holes (40).

34. A method as claimed in claim 1 substantially as hereinbefore described with reference to any one of Figures 1, la, 3, 4, 5, 6 or 7 of the accompanying drawings.

35. Apparatus as claimed in claim 11 substantially as hereinbefore described with reference to and as illustrated in any one of Figures 1, la, 3, 4, 5, 6 or 7 of the accompanying drawings.

36. A casing sheet as claimed in claim 27 substantially as hereinbefore described with reference to and as illustrated in any one of Figures 8, 9, 10, 11 or 12 of the accompanying drawings