Apparatus and related method for producing an absorbent core for an absorbent article

Abstract

The invention provides a method for producing an absorbent core (4) for an absor- bent article (6), the method comprising the steps of: forming a first core member (14a) from a first absorbent material (12a) with a first forming drum (8a), forming a second core member (14b) from a second absorbent material (12b) with a second forming drum (8b), combining the first core member (14a) and the second core member (14b) to form the absorbent core (4), wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged at least partially side-by-side.

Description

[0001] TERGAU & WALKENHORST page 1

[0002] P240217P

[0003] 4 July 2025

[0004] Description

[0005] Apparatus and related method for producing an absorbent core for an absorbent article

[0006] The invention relates to an apparatus and a related method for producing an absorbent core for an absorbent article.

[0007] Absorbent articles, more specifically hygiene products like diapers, usually comprise an absorbent core wrapped between two sheets, typically nonwoven sheets.

[0008] It is generally advantageous to make absorbent cores comprising one or more channels, i. e. material-free areas. Reasons are:

[0009] • The channels provide or support an improved fluid distribution within the core.

[0010] • There is better core integrity if the upper and lower sheets are bonded along the channels.

[0011] • The channels act as folding guides, thus improving the fit of the absorbent product on the body of the wearer.

[0012] One prior-art solution to provide absorbent cores with such channels is to use drum formers or similar devices with inserts which block the absorbent material during the forming process, leaving free space upon later removal.

[0013] For example, EP 2532329 B1 discloses an apparatus for making an absorbent structure with channels that are free of absorbent material. The channels are formed by longitudinally extending raised strips in the absorbent-layer forming reservoirs. Similarly, EP 3595603 B1 discloses a mold for forming an absorbent core wherein a shaping profile member is engaged with the air-permeable base surface via interlocking elements. Furthermore US 5756039 A discloses an apparatus and method TERGAU & WALKENHORST page 2 for forming a sanitary napkin having a multi-segment core. The core is formed by a mold divided into longitudinal cavity segments.

[0014] Disadvantages of these solutions include:

[0015] • Some absorbent material is left on the inserts. As a result, the channels are not completely free of absorbent material, which makes it difficult to achieve good bonding strength between the core wrap sheets.

[0016] • It is difficult to mount inserts on the porous surface of the pockets. There is a risk of parts becoming loose due to the high rotation speed of the forming drum.

[0017] • It is difficult to make core wrap nonwovens follow the insert contour. It is likely that the core wrap is damaged (due to tearing), especially when using low- grammage materials.

[0018] Another prior-art solution is to remove absorbent material from the intended channel regions.

[0019] In this sense EP 3600190 B1 discloses an apparatus for forming an absorbent pad comprising at least one channel created by an insert. Absorbent material remaining on the core wrap web at the channel is removed by a removal system comprising an air flow. EP 3403627 B1 discloses a method for manufacturing an absorbent article. The absorbent material located above a non-suction zone is removed by means of a rotating brush.

[0020] Disadvantages of these solutions include:

[0021] • The required apparatus can be difficult to adjust (e.g. narrow gap between brush and rotating drum).

[0022] • Frequently, there is no complete removal of the material.

[0023] • The concept supports creation of turbulences which lead to higher variability in the deposition of absorbent material.

[0024] • The core wrap can be damaged by the removal process.

[0025] • Even the absorbent can be damaged. TERGAU & WALKENHORST page 3

[0026] In order to overcome the problems outlined above, there is a need for simple, reliable and cost-efficient apparatus and a related method which are suited to make absorbent cores with channels that are as void or depleted of absorbent material as possible without subsequent removal or cleaning steps, preferably avoiding material-blocking inserts.

[0027] According to the invention, said objective is achieved by a method specified in claim 1.

[0028] Accordingly, the invention suggests a method for producing an absorbent core for an absorbent article, the method comprising the steps of:

[0029] • forming a first core member from a first absorbent material with a first forming drum,

[0030] • forming a second core member from a second absorbent material with a second forming drum,

[0031] • combining the first core member and the second core member to form the absorbent core, wherein the first core member and the second core member are shaped and combined such that in the absorbent core they are arranged at least partially side-by- side.

[0032] The solution disclosed here typically includes two drum formers, each providing an endless moving surface. By each of the drum formers an absorbent core member is formed, preferably on a supporting sheet. The two absorbent core members, preferably on their respective supporting sheets, are then combined to provide an absorbent core. Due to the shapes of the two absorbent core members and due to the synchronized combining step, they are arranged in the combined absorbent core at least partially side-by-side, preferably in an interlocking, puzzle like-manner. Furthermore, the combined absorbent core may comprise one or more areas, called channels, between two core members that are substantially free of absorbent material. TERGAU & WALKENHORST page 4

[0033] Typically, the absorbent core is a flat product, having a lateral extension that is larger or even substantially larger than its height. The lateral extension usually coincides with the lateral extension of the carrier sheet or the two wrapping sheets. “Side-by- side” in the previous paragraph preferably refers to the lateral extension, meaning that the two core members are placed side-by-side when viewed from above the top sheet or below the bottom sheet (in contrast to a stacking or layering in height direction).

[0034] In a preferred embodiment the steps of forming the first core member and of forming the second core member happen simultaneously. Preferably, during the combining step the first sheet and the second sheet are aligned parallel to each other with the first core member and the second core member facing each other.

[0035] A first version of a suitable apparatus for producing an absorbent core for an absorbent article comprises:

[0036] • a first endless moving surface, comprising a number of molds typically in the form of first pockets,

[0037] • a second endless moving surface, comprising a number of molds typically in the form of second pockets,

[0038] • transfer means for transferring first and second sheets to said first and second moving endless surfaces,

[0039] • a first feeder for feeding a first absorbent material onto the first sheet at a depositing region on the first moving endless surface, thereby forming a first absorbent core member on the first sheet,

[0040] • a second feeder, alternatively a branch-off from the first feeder, for feeding a second absorbent material onto the second sheet at a depositing region on the second moving endless surface, thereby forming a second absorbent core member on the second sheet,

[0041] • a means for combining the first and second absorbent core members, thereby forming a joint absorbent structure, wherein the first core member and the second core member are shaped and combined such that in the absorbent core they are arranged at least partially side-by- side. TERGAU & WALKENHORST page 5

[0042] For this version, a particularly simple structure and a reliable operation may be achieved when the first forming drum and the second forming drum are separated by a gap which constitutes a combining and compressing region for the first and second sheets with the first and second core members thereon.

[0043] A second version of the apparatus comprises:

[0044] • a first endless moving surface, comprising a number of molds typically in the form of first pockets,

[0045] • a second endless moving surface, comprising a number of molds typically in the form of second pockets,

[0046] • a first feeder for feeding a first absorbent material onto the first endless moving surface at a depositing region, thereby forming a first absorbent core member,

[0047] • a second feeder, alternatively a branch-off from the first feeder, for feeding a second absorbent material onto the second endless moving surface at a depositing region, thereby forming a second absorbent core member,

[0048] • a moving carrier which consecutively passes the first endless moving surface and the second endless moving surface, thereby combining the first and second absorbent core members and forming a joint absorbent structure, wherein the first core member and the second core member are shaped and combined such that in the absorbent core they are arranged at least partially side-by- side.

[0049] Herein and further above, the second absorbent material may be the same material as the first absorbent material, or alternatively a different one.

[0050] Some properties including variation and options of the product manufacturable with the apparatus and the method according to the invention may be summarized as follows. Some of these product features may be considered to be inventive in their own right: TERGAU & WALKENHORST page 6

[0051] 1. The quantity of core members can be 1 , 2 or more. Preferred are 2 or 3 members.

[0052] 2. The members can be in 2D- or 3D-shape, seen in cross-sectional view.

[0053] 3. The members can be in 2D- or 3D-shape, seen in length-sectional view.

[0054] 4. The members can be oriented in product cross-direction or in length-direction or in a combination of both.

[0055] 5. The members can be symmetrical or asymmetrical.

[0056] 6. Each core member can consist of pure fibers A, or a blend of fibers A and superabsorbent material B, or pure superabsorbent material B.

[0057] 7. The absorbent fibers A can be defiberized or short-cut fibers of natural or synthetic origin.

[0058] 8. Superabsorbent material B can be powder or granulate or fibers.

[0059] 9. The grammage of fibers A and / or superabsorbent material B in each core member can be identical or different from the other core members.

[0060] 10. Each core member can be with or without a carrier sheet under the fibers.

[0061] 11 . Each core member can be with or without a cover sheet above the fibers.

[0062] 12. Such carrier and / or cover sheet can be continuous or discontinuous.

[0063] 13. Such carrier and / or cover sheet can be one or a combination of top-sheet, acquisition layer, transfer layer, core-wrap or other material.

[0064] 14. Each core member can be consisting of 1 , 2 or 3 core layers. Difference between the layers is the concentration of fibers A and superabsorber B.

[0065] 15. Carrier and / or cover sheet(s) can be bonded to one or more core segments, or not.

[0066] 16. Carrier and cover sheets can be bonded to each other or not.

[0067] 17. For male and female product users (“boys & girls”), the distribution of fibers A and / or superabsorber B, and the design of the core members, can be identical or different.

[0068] 18. The core members can be placed with or without a same or different distance to each other at one or more sides.

[0069] 19. The core members can be placed with or without overlapping of each other. Such overlap creates zone(s) of different concentration of absorbent fiber A and / or superabsorbent material B. TERGAU & WALKENHORST page 7

[0070] Regarding point 6 of the enumeration it is noted that the fibers A & B could in turn be made of different fiber types (e.g. cellulose from pine fibers and from eucalyptus fibers) and / or the superabsorber material could consist or comprise of different types (e.g. a fast-absorbing superabsorber that does not have particularly good values for absorption under pressure and a slow-absorbing superabsorber that has very good values for absorption under pressure (AuP)).

[0071] Some properties including variation and options of the process (method) may be summarized as follows. Some of these process steps may be considered to be inventive in their own right:

[0072] 1 . The forming process can be supplied by one, two or more defiberizing systems for absorbent material A.

[0073] 2. The forming process can be supplied by one, two or more dosing and feeding systems for superabsorbent material B.

[0074] 3. The core segments can be formed in continuous or discrete manner.

[0075] 4. In the event of discrete formation, the forming drum can be with or without an integrated function to change the distance between the formed segments before transferring them to the next process step.

[0076] 5. Bonding can be made by adhesive and pressure, or by mechanical welding (e.g. ultrasonic, thermo-sealing, cold-pressure embossing, needling, stitching, hydrobonding).

[0077] 6. Free areas between core members can be pressed or not.

[0078] In summary, the advantages achieved with the invention include in particular a simple and reliable production of absorbent cores with material-free channels, whereby a high product variety can be achieved. The equipment-related effort required to implement the process is comparatively low and is based on tried and tested individual components that are combined in surprising new ways.

[0079] Various embodiments of the invention are subsequently described with reference to the accompanying drawings. TERGAU & WALKENHORST page 8

[0080] FIG. 1 shows a highly schematic illustration of an apparatus for forming an absorbent core for an absorbent article.

[0081] FIG. 2 to FIG. 8 show various examples of absorbent cores, wherein:

[0082] FIG. 2 shows cores shapes without overlap composed of two core members.

[0083] FIG. 3 shows cores shapes without overlap composed of two core members.

[0084] FIG. 4 shows cores shapes without overlap composed of two core members.

[0085] FIG. 5 shows cores shapes without overlap composed of three core members.

[0086] FIG. 6 shows cores shapes with overlap composed of two core members.

[0087] FIG. 7 shows cores shapes with overlap composed of two core members.

[0088] FIG. 8 shows cores shapes with overlap composed of three core members.

[0089] FIG. 9 shows another apparatus for forming an absorbent core for an absorbent article.

[0090] FIG. 10 shows yet another apparatus for forming an absorbent core for an absorbent article.

[0091] FIG. 11 shows a variation of the apparatus of FIG. 1 .

[0092] FIG. 12 shows an absorbent article in the shape of a diaper with an absorbent core.

[0093] Similar or likewise elements are marked with the same reference numerals throughout the figures.

[0094] In the subsequent description “absorbent material” refers to a material or mixture of materials that can absorb and retain bodily fluids such as urine, blood, vaginal discharges, breast milk, sweat and fecal matter. More specifically, this may be an absorbent or superabsorbent material (superabsorbent being a subset of absorbent), in particular based on a polymer material and / or fibers and / or a blend of fibers. In one preferred embodiment a particulate material may be used, so as to be flowable in the dry state, such as a powder or granulate of fibers or other absorbent material. TERGAU & WALKENHORST page 9

[0095] "Absorbent article" refers to a device or an article that absorbs and contains body exudates or fluids, and, more specifically, refers to devices that are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Absorbent articles may include adult and infant diapers, including pants, such as infant training pants and adult incontinence undergarments, and feminine hygiene products, such as sanitary napkins and panty-liners and adult incontinent pads, and breast pads, care mats, bibs, wound dressing products, and the like. Absorbent articles may further include floor cleaning articles, food industry articles, and the like.

[0096] A “sheet” may be made, for example, of textile and / or non-woven and / or cellulose- based material and can preferably be unrolled from a supply roll.

[0097] FIG. 1 shows a schematic cross section of a first embodiment of an apparatus 2 for forming an absorbent core 4 for an absorbent article 6 (also see FIG. 2 - 8 and FIG. 12). The apparatus 2 comprises a first forming drum 8a and a second forming drum 8b arranged side by side, such that their respective axes of rotation are aligned essentially horizontally and parallel to each other. Each of the forming drums 8a, 8b provides an endless moving (rotating) surface 28a, 28b at its circumference.

[0098] The leftmost forming drum in FIG. 1 , called the first forming drum 8a, is designed to rotate in clockwise direction, thereby guiding a first “endless” web or sheet 10a fed tangentially from the left side along a section of its circumference (on the endless moving surface 28a). During operation, the first sheet 10a preferably passes an upper section including the highest point of the first forming drum 8a and follows its circumferential contour to finally leave the first forming drum 8a tangentially, preferably downwardly in essentially vertical direction.

[0099] The first forming drum 8a comprises a drum cylinder which preferably comprises a number of molds, typically in the form of first pockets 30a, around its circumference which are designed to hold a first absorbent material 12a deposited of the outer surface (facing away from the drum cylinder) of the first sheet 10a. Each pocket 30a TERGAU & WALKENHORST page 10 of the first forming drum 8a defines the outline or lateral contour of a first absorbent core member 14a thus deposited and shaped on the first sheet 10a.

[0100] The first absorbent material 12a is preferably fed with the help of a first feeder 16a arranged above the first forming drum 8a. That is, the material deposition on the passing first sheet 10a preferably happens in the upper section of the first forming drum 8a when the corresponding pocket 30a of the drum cylinder is in an appropriate position.

[0101] To support the accumulation and retention of the first absorbent material 12a on the first sheet 10a in the region of the respective pocket 30a (and preferably only there) the drum cylinder of the first forming drum 8a preferably comprises a plurality of suction holes in the region of each pocket 30a, preferably spread over the pocket area (realizing an aperture plate). These suction holes are coupled to a vacuum system inside the drum cylinder, such that during operation an inwards suction stream of air through the air-permeable first sheet 10a is established.

[0102] The previous description analogously applies to the rightmost forming drum in FIG. 1 , called the second forming drum 8b. However, the second forming drum 8b is designed to rotate in anti-clockwise direction, thereby guiding a second “endless” web or sheet 10b fed tangentially from the right side along a section of its circumference (on the endless moving surface 28b). During operation, the second sheet 10b preferably passes an upper section including the highest point of the second forming drum 8b and follows its circumferential contour to finally leave the first forming drum 8b tangentially, preferably downwardly in essentially vertical direction.

[0103] The second forming drum 8b comprises a drum cylinder which preferably comprises a number of molds, typically in the form of second pockets 30b, around its circumference which are designed to hold a second absorbent material 12b deposited on the outer surface (facing away from the drum cylinder) of the second sheet 10b. Each pocket 30b of the second forming drum 8b defines the outline or lateral contour of a second core member 14b thus deposited and shaped of the second sheet 10b. TERGAU & WALKENHORST page 1 1

[0104] The second absorbent material 12a is preferably fed with the help of a second feeder 16b arranged above the second forming drum 8b. That is, the material deposition on the passing second sheet 10b preferably happens in the upper section of the second forming drum 8b when the corresponding pocket 30b of the drum cylinder is in an appropriate position.

[0105] To support the accumulation and retention of the second absorbent material 12b on the second sheet 10b in the region of the respective pocket 30b (and preferably only there) the drum cylinder of the second forming drum 8b preferably comprises a plurality of suction holes in the region of each pocket 30b, preferably spread over the pocket area. These suction holes are coupled to a vacuum system inside the drum cylinder, such that during operation an inwards suction stream of air through the air- permeable second sheet 10b is established.

[0106] Therefore, a first absorbent core member 14a with a well-defined lateral shape and contour and a given height or height profile is produced on the first sheet 10a when passing the first feeder 16a, and a second absorbent core member 14b with a well- defined lateral shape and contour and a given height or height profile is produced on the second sheet 10b when passing the second feeder 16b. This preferably happens simultaneously in a synchronized manner such that the first absorbent core member 14a and the second absorbent core member 14b, facing each other, meet in the gap between the two drum cylinders.

[0107] Thereby the two mating absorbent core members 14a, 14b are combined into a single absorbent core 4 wrapped between the two sheets 10a, 10b which are aligned essentially parallelly in the mating region. With a suitably chosen gap between the drum cylinders the thus-produced absorbent core 4 may be compressed between the sheets 10a, 10b, yielding a desired physical consistency and / or density.

[0108] FIG. 2 shows a set of possible absorbent cores 4 made or composed of two mating core members 14a, 14b in the process described above with the help of the described apparatus 2 of FIG. 1 (or alternatively FIG. 9 or FIG. 10). For each of the TERGAU & WALKENHORST page 12 four examples the view is chosen to show a section though the absorbent core 4 in a sectional plane S between the two parallel sheets 10a, 10b and parallel to them, as indicated in FIG. 1. For the sake of simplicity, in these drawings the first and second core members 14a, 14b are simply denoted 1 and 2.

[0109] In each of the four examples of FIG. 2, the two absorbent core members lie next to each other (side by side) and interlock in a puzzle-like or Tetris<™>-like complementary manner, partially interlocked or nested, so that a base area defined by an outer outline (here in the example: rectangular) is filled in approximately or to a large extent. In these examples the two core shapes or core members have no overlap.

[0110] However, in these examples the base area preferably is not 100% filled. While the first and second core members are directly adjacent to each other at some boundary surfaces (contact surfaces, in this case), the first and second core members are separated from each other by a gap in other boundary regions. These material-free gaps in which neither the first nor the second absorbent material is present are also referred to as channels 18. In the examples, the channels 18 are relatively narrow straight, curved, or kinked internal channels, not reaching the outer outline.

[0111] Note that in a variation of the concept (not shown) it is possible to have a 100% filled base area. That is, the two core members are fully complementary, resting side-by- side against each other with no channels in between.

[0112] FIG. 3 shows a set of four further examples of absorbent cores composed of two mating core members. Again, the individual core shapes or core members do not overlap. In contrast to the examples in FIG. 2, the core members are not nested or geometrically interlocked, but lie flat on top of each other. The contact surface between the two core members is interrupted by local internal recesses, gaps, or cavities that form ornamental (here: heart-shaped) decorations. Again, these cavities may be called channels.

[0113] FIG. 4 shows a set of three further examples of absorbent cores composed of two mating, non-overlapping core members with material-free internal channels in TERGAU & WALKENHORST page 13 between. These are basically slight variations or combinations of the geometric forms in the previous figures.

[0114] FIG. 5 shows a generalization of the previous concept with five examples of absorbent cores composed of three mating, non-overlapping core members (denoted 1 , 2, and 3) with material-free internal channels in between. This may be achieved with an apparatus and a process similar to those discussed with reference to FIG. 1 but with an additional third feeder for a third absorbent material and, if necessary, a number of further drum formers, thereby being designed for forming a third core member which is to be combined or mated with two other core members.

[0115] FIG. 6 shows a set of five further examples of absorbent cores composed of two mating core members, most of them having channels in between (but in one case without such channels). In contrast to the previous examples, the individual core shapes or core members do at least partially overlap. That is, that in the overlapping region 20 that first core member is stacked on the second core member or vice versa. Preferably, the height profile of the individual core members is reduced in the overlapping region(s) in comparison to the non-overlapping region(s) in order to maintain a relatively even height of the entire absorbent core over its lateral extension.

[0116] FIG. 7 shows four variations of the examples in FIG. 6, that is absorbent cores composed of two mating core members, with or without channels in between, and with overlapping regions 20 of the two core members.

[0117] Finally, FIG. 8 shows a generalization of the previous concepts, with four examples of an absorbent core composed of three core members, with channels in between (no channels would be an option though), and with overlapping regions where at least (and preferably at most) two of the core members overlap.

[0118] In all the previous and following cases the absorbent core 4 is composed of two or more individually formed core members 14a, 14b, which are combined in order to create the final complete core shape. In particular, by a suitably chosen geometry TERGAU & WALKENHORST page 14 of the induvial core members 14a, 14b and a synchronized joining process it is possible to have channels 18 free of absorbent material in the final product. This does neither require inserts in / on the drum formers 8a, 8b nor removing any temporarily deposited material.

[0119] Summarizing so far, in the embodiment of FIG. 1 each absorbent core member 14a, 14b is deposited and transported on a web or sheet 10a, 10b. Each sheet 10a, 10b acts as a carrier. After deposition of the core members 14a, 14b the sheets 10a, 10b are brought close to each other into parallel alignment with the core members 14a, 14b facing each other in order to combine the two core members 14a, 14b, thereby forming a joint absorbent structure. In the resulting product, the absorbent core 4 is wrapped between the two sheets 10a, 10b (for example, one of them may be regarded a top sheet and the other one a bottom sheet). However, the usage of webs or sheets 10a, 10b on the drum formers 8a, 8b is not essential, as can be seen from the next example.

[0120] In the embodiment of FIG. 9 an apparatus 2 for forming an absorbent core 4 for an absorbent article 6 comprises a first forming drum 8a and a second forming drum 8b arranged side by side, such that their respective axes of rotation are aligned essentially horizontally and parallel to each other (but unlike in FIG. 1 not necessarily in a small-gap distance, rather in a larger, arbitrary distance). During operation both forming drums 8a, 8b rotate in the same direction, for example counter-clockwise. Below the two forming drums 8a, 8b a web or sheet or a conveyor belt, in brief a moving carrier 22, is arranged and moved accordingly, for example from left to right (the moving carrier 22 is not necessarily “endless” but may have a suitable length instead).

[0121] Each forming drum 8a, 8b is designed to receive an absorbent material 12a, 12b from an associated feeder 16a, 16b, thereby forming an absorbent core member 14a, 14b, and to transfer said core member 14a, 14b to the moving carrier 22 below. The transfer is synchronized such that in the example the first forming drum 8a transfers a first core member 14a on the passing carrier 22, and then the second TERGAU & WALKENHORST page 15 forming drum 8b transfers a second core member 14b, thereby combining both core members 14a, 14b and forming a joint absorbent core 4 or structure.

[0122] To achieve this goal, each forming drum 8a, 8b may comprise a number of molds, typically in the shape of pockets 30a, 30b, along its circumference which may be coupled to a vacuum system via suction holes as described with reference to FIG. 1 . The pockets 30a, 30b shape the deposited material and transport and transfer it to the passing carrier 22 below the respective forming drum 8a, 8b.

[0123] In general, the combining or mating of the two or more core members 14a, 14b may happen at a location different from the drum formers 8a, 8b which shape the individual core members 14a, 14b.

[0124] This is exemplarily visualized in FIG. 10 which shows another embodiment of an apparatus 2 for forming an absorbent core 4 for an absorbent article 6. The apparatus 2 comprises a first drum former 8a for forming a first core member 14a on a passing first sheet 10a and a second drum former 8b for forming a second core member 14b on a passing second sheet 10b based on the same principles as discussed in connection with FIG. 1.

[0125] However, in contrast to said embodiment of FIG. 1 the two drum formers 8a, 8b in FIG. 10 are not positioned directly next to each other. Rather, the first sheet 10a (with the first core member 14a deposited on it) is guided from the outlet of the first drum former 8a via a transfer roller 24 to a mating roller 26 which is positioned in gap-distance to the outlet of the second drum former 8b. The second drum former 8b and the mating roller 26 interact in such a way that the first sheet 10a with the first core member 14a and the second sheet 10b with the second core member 14b are combined (and preferably compressed) in the gap, thereby forming a joint absorbent core 4.

[0126] It goes without saying that the above description only describes the basic kinematics of the absorbent core production and the components required for this. The respective apparatus 2 may also have other useful or advantageous components. These TERGAU & WALKENHORST page 16 include, for example, spray nozzles or other devices for applying adhesive to the core members and / or the sheets, guide rollers, transfer rollers, velocity adjusters, deflection rollers, vacuum systems and / or guidance systems. The apparatus 2 may also comprise feeding devices, separation devices and / or stacking devices.

[0127] The apparatus 2 may also comprise means for bonding the first sheet 10a and the second sheet 10b in the material-free areas, for example by using adhesive application devices and / or compression devices. Additionally or alternatively, mechanical welding, ultrasonic welding, thermo-sealing, hydrobonding, cold pressure embossing, needling and / or stitching may be used to accomplish said task.

[0128] In general, each absorbent core member 14a, 14b can be manufactured with or without a carrier sheet 10a, 10b, as outlined above. In the final absorbent core 4, preferably one carrier sheet is below the core as a bottom sheet and another one is above the core as a cover sheet or top sheet.

[0129] In general, the absorbent core 4 can be formed continuously and separated into individual core pieces or segments afterwards, in particular if drum formers with fully revolving pockets on the circumference are used, or in a discrete manner, in particular if the pockets cover only a partial circumference of the drum forming cylinder. In the event of discrete formation, the forming drum can be with or without an integrated function to change the distance between the formed pieces or segments before transferring them to the next process step.

[0130] In general, the first absorbent material 12a for forming the first core member 14a can be the same as the second absorbent material 12b for forming the second core member 14b, or alternatively they may be different materials (and analogously for a third, fourth etc. absorbent material, if present). In particular, different (normally) absorbent material types or different superabsorbent material types may be used for each of the absorbent members.

[0131] Accordingly, the first sheet 10a and the second sheet 10b may be made of the same material or of different materials. TERGAU & WALKENHORST page 17

[0132] In general, the absorbent core 4 or absorbent structure may comprise areas where the first and second absorbent core members 14a, 14b are overlapping, and areas where the first and second absorbent core members 14a, 14b are not overlapping. This concept may be used for creating zones of higher and lower concentration of superabsorbent material, if one of the absorbent materials is a superabsorbent material and the other is a simple absorbent material. However, in other cases the absorbent core members 14a, 14b may be arranged to not overlap at all.

[0133] In a (non-shown) variation of the apparatus 2 of FIG. 1 there is a single feeder with a subsequent distribution device or branch-off, distributing the fed absorbent material to the first and second forming drums 8a, 8b. This variation may also apply to the apparatus of FIG. 9 or FIG. 10 or FIG. 11 .

[0134] In a further variation of the apparatus of FIG. 1 , shown in FIG. 11 , an additional separating layer or separating sheet 32 is introduced between the first and second core members 14a, 14b. To this end, the separating sheet 32 is fed from above the drum former arrangement in downward (tangential) direction, along the symmetry plane S, into the gap region between the first and second forming drums 8a, 8b where the mating of the first and second core members 14a, 14b happens. Upstream of the gap region the separating sheet 32 is preferably sprayed or otherwise coated from one side or preferably both sides with an adhesive. This may be achieved, for example, by spray nozzles 34. As before, in the resulting product, which leavers the gap region in downward (tangential) direction, the absorbent material is wrapped or sandwiched between first and second sheets 10a, 10b, but the first and second core members 14a, 14b are now separated by the separating sheet 32. Depending on the course or structure of the interface between the first and second core member 14a, 14b, which are at least partially adjacent (side-by-side) to each other and possibly nested within each other, the separating sheet 32 can assume local deformations or bulges, which is favored by deformability and ductility of the separating sheet material. TERGAU & WALKENHORST page 18

[0135] List of reference numerals

[0136] 2 apparatus

[0137] 4 absorbent core

[0138] 6 absorbent article

[0139] 8a first forming drum

[0140] 8b second forming drum

[0141] 10a first sheet

[0142] 10b second sheet

[0143] 12a first absorbent material

[0144] 12b second absorbent material

[0145] 14a first core member

[0146] 14b second core member

[0147] 16a first feeder

[0148] 16b second feeder

[0149] 18 channel

[0150] 20 overlapping region

[0151] 22 moving carrier

[0152] 24 transfer roller

[0153] 26 mating roller

[0154] 28a first endless moving surface

[0155] 28b second endless moving surface

[0156] 30a first pocket

[0157] 30b second pocket

[0158] 32 separating sheet

[0159] 34 spray nozzles

[0160] 5 sectional plane

Claims

TERGAU & WALKENHORST page 19Claims1 . A method for producing an absorbent core (4) for an absorbent article (6), the method comprising the steps of:• forming a first core member (14a) from a first absorbent material (12a) with a first forming drum (8a),• forming a second core member (14b) from a second absorbent material (12b) with a second forming drum (8b),• combining the first core member (14a) and the second core member (14b) to form the absorbent core (4), wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged at least partially side-by-side, and wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) there are one or more areas, called channels (18), between the two core members (14a, 14b) that are substantially free of absorbent material (12a, 12b).

2. The method according to claim 1 , wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged in a geometrically interlocking, puzzle-like manner.

3. The method according to claim 1 or 2, wherein each of the first core member (14a) and the second core member (14b) comprises or consists of either pure fibers, a blend of fibers and superabsorbent material, or pure superabsorbent material, and wherein the grammage of fibers and / or superabsorbent material in the first core member (14a) is different from that in the other core member (14b).

4. The method according to any one of the preceding claims, wherein the steps of forming the first core member (14a) and of forming the second core member (14b) happen simultaneously.TERGAU & WALKENHORST page 205. The method according to any one of the preceding claims, wherein the first core member (14a) is formed on a first sheet (10a).

6. The method according to claim 5, wherein the second core member (14a) is formed on a second sheet (10b).

7. The method according to claim 6, wherein during the combining step the first sheet (10a) and the second sheet (10b) are aligned parallel to each other with the first core member (14a) and the second core member (14b) facing each other.

8. The method according to any one of the preceding claims, wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they form an overlapping region (20).

9. The method according to any one of the preceding claims, wherein a third core member is combined with the first core member (14a) and the second core member (14b).

10. An apparatus (2) for producing an absorbent core (4) for an absorbent article (6), the apparatus (2) comprising:• a first endless moving surface (28a), comprising a number of molds typically in the form of first pockets (30a),• a second endless moving surface (28b), comprising a number of molds typically in the form of second pockets (30b),• transfer means for transferring first and second sheets (10a, 10b) to said first and second moving endless surfaces (28a, 28b),• a first feeder (16a) for feeding a first absorbent material (12a) onto the first sheet (10a) at a depositing region on the first moving endless surface (28b), thereby forming a first absorbent core member (14a) on the first sheet (10a),• a second feeder (16b), alternatively a branch-off from the first feeder (16a), for feeding a second absorbent material (12b) onto the second sheet (10b) at a depositing region on the second moving endless surface (28b), thereby forming a second absorbent core member (14b) on the second sheet (10b),TERGAU & WALKENHORST page 21• a means for combining the first and second absorbent core members (14a, 14b), thereby forming a joint absorbent structure, wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged at least partially side-by-side.

11. The apparatus (2) according to claim 10, wherein the first endless moving surface (28a) is at the circumference of a first forming drum (8a).

12. The apparatus (2) according to claim 11 , wherein the second endless moving surface (28b) is at the circumference of a second forming drum (8b).

13. The apparatus (2) according to claim 12 wherein the first forming drum (8a) and the second forming drum (8b) are separated by a gap which constitutes a combining and compressing region for the first and second sheets (10a, 10b) with the first and second core members (14a, 14b) thereon.

14. An apparatus (2) for producing an absorbent core (4) for an absorbent article (6), the apparatus (2) comprising:• a first endless moving surface (28a), comprising a number of molds typically in the form of first pockets (30a),• a second endless moving surface (28b), comprising a number of molds typically in the form of second pockets (30b),• a first feeder (16a) for feeding a first absorbent material (12a) onto the first endless moving surface (28a) at a depositing region, thereby forming a first absorbent core member (14a),• a second feeder (16b), alternatively a branch-off from the first feeder (16a), for feeding a second absorbent material (12b) onto the second endless moving surface (28b) at a depositing region, thereby forming a second absorbent core member (14b),• a moving carrier (22) which consecutively passes the first endless moving surface (28a) and the second endless moving surface (28b), thereby combining the first and second absorbent core members (14a, 14b) and formingTERGAU & WALKENHORST page 22 a joint absorbent structure, wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged at least partially side-by-side.

15. The apparatus (2) according to claim 10 or 14, wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged in a geometrically interlocking, puzzle-like manner.

16. The apparatus (2) according to claim 10 or 14, wherein each of the first core member (14a) and the second core member (14b) comprises or consists of either pure fibers, a blend of fibers and superabsorbent material, or pure superabsorbent material, and wherein the grammage of fibers and / or superabsorbent material in the first core member (14a) is different from that in the other core member (14b).

17. The apparatus (2) according to claim 10 or 14, wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) there are one or more areas, called channels (18), between the two core members (14a, 14b) that are substantially free of absorbent material (12a, 12b).

18. A method for producing an absorbent core (4) for an absorbent article (6), the method comprising the steps of:• forming a first core member (14a) from a first absorbent material (12a) with a first forming drum (8a),• forming a second core member (14b) from a second absorbent material (12b) with a second forming drum (8b),• combining the first core member (14a) and the second core member (14b) to form the absorbent core (4), wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) they are arranged at least partially side-by-side, and wherein each of the first core member (14a) and the second core member (14b) comprises or consists of either pure fibers, a blend of fibers andTERGAU & WALKENHORST page 23 superabsorbent material, or pure superabsorbent material, and wherein the grammage of fibers and / or superabsorbent material in the first core member (14a) is different from that in the other core member (14b).

19. The method according to claim 17, wherein the first core member (14a) and the second core member (14b) are shaped and combined such that in the absorbent core (4) there are one or more areas, called channels (18), between the two core members (14a, 14b) that are substantially free of absorbent material (12a, 12b).

20. An absorbent core (4) for an absorbent article (6) produced by the method according to any one of the claims 1 to 9, 16, or 17.

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