Device and method for producing an absorbent core

Abstract

Main claim: The invention relates to a device for producing an absorbent core having a plurality of material layers for an absorbent product, comprising: - a core forming drum (10), which rotates during operation, or a screening-belt structure, which is moved linearly, - a flock box (16) for feeding pulp to the core forming drum (10) or to the screening-belt structure, - one or more insertion lances (32), which can be variably positioned with respect to the core forming drum (10) or the screening-belt structure and each have a spray nozzle (34) for superabsorber, wherein - each insertion lance (32) is assigned an individually controllable flow-regulating device (80), in particular a disc valve (30), for a continuous or intermittent supply of superabsorber, - each spray nozzle (34) generates, during operation, a spray cone (48) having an impact region (46) on the core forming drum (10) or on the screening-belt structure, wherein, when viewed in the circumferential direction of the core forming drum (10) or in the longitudinal direction of the screening-belt structure, the impact regions (46) can be variably positioned as adjacent, overlapping or at a distance from one another, in order to allow targeted structuring of the material layers, - there is a control unit (50), which synchronizes the rotational movement of the core forming drum (10) or the linear movement of the screening-belt structure and the switching position of the flow-regulating devices (80), such that the core to be produced has a plurality of material layers, wherein, when viewed in the circumferential direction of the core forming drum (10) or in the longitudinal direction of the screening-belt structure, each of the material layers is variably composed of a number of sections which each consist of pure pulp (Fluff), of pure superabsorber (SAP) or of a mixture of cellulose and superabsorber (Fluff & SAP).

Description

[0001] TERGAU & WALKENHORST Page 1 P250100P

[0002] February 5, 2026

[0003] Description

[0004] Device and method for producing an absorbing core

[0005] The invention relates to a device and a method for producing an absorbent core, in particular for applications in the hygiene industry, in which superabsorbent polymer (SAP) is applied to a fibrous web or cellulose layer.

[0006] Absorbent polymer (AMP) is frequently used in products such as diapers, sanitary napkins, or incontinence products, where the uniform or structured distribution and precise dosage of AMP play a crucial role in the absorption properties. In such applications, a high degree of variability in product structure and precise control of material quantities are required to achieve the desired performance characteristics.

[0007] The object of the invention is to provide an improved method for the flexible, precise, and cost-effective production of an absorbent core material (KEM) comprising one or more SAP-containing layers with variable properties. The aim is to achieve high product variability while simultaneously reducing the effort required to adapt the manufacturing process. In particular, the SAP application on the pulp web is to be controlled in such a way that the amount of SAP and its distribution in the different areas of the layers are variable and adaptable to the specific requirements of the final product. Furthermore, the invention is intended to offer high flexibility with regard to the number of spraying processes and their control, in order to enable a wide range of product configurations. A suitable apparatus and method for this purpose are to be described.

[0008] With regard to the device, the problem is solved by the features of claim 1. An associated manufacturing method is specified in claim 16. TERGAU & WALKENHORST Page 2

[0009] Accordingly, the invention comprises a device for producing an absorbent core with multiple material layers for an absorbent product, comprising:

[0010] • a drum former wheel that rotates during operation,

[0011] • a flaking box for feeding cellulose to the drum former wheel, • one or more, preferably at least two, feed lances variably positionable relative to the drum former wheel, each with a spray nozzle for superabsorbent polymer,

[0012] where

[0013] • Each injection lance is assigned an individually controllable flow control device, in particular a disc valve, for a continuous or intermittent supply of superabsorbent,

[0014] • Each spray nozzle in operation generates a spray cone with an impact area on the drum former wheel, whereby the impact areas, viewed in the circumferential direction of the drum former wheel, can be variably positioned as adjacent, overlapping or spaced apart from each other in order to enable targeted structuring of the material layers,

[0015] • a control unit is present which synchronizes the rotary movement of the drum former wheel and a switching position of the flow control devices, in particular the disc valves, so that the core to be produced has several layers of material, each of which, viewed in the circumferential direction of the drum former wheel, is variably composed of a number of sections, each consisting of either pure cellulose, pure superabsorbent or a mixture of cellulose and superabsorbent.

[0016] In extreme cases, the respective layer can consist of a single section. TERGAU & WALKENHORST Page 3 In other words, the invention implies the use of a device with multiple spray nozzles, each having an adjustable supply line and an individually controllable flow regulator, in particular a disc valve. Each flow regulator controls the amount of sprayed superabsorbent polymer (SAP) and enables precise dosing. Particularly in the case of disc valves, the spray time and the associated amount of SAP can be specifically controlled by rotating the valve discs. The control can be either continuous or intermittent, which makes it possible to restrict the SAP application to specific parts of the pulp web.In particular, this opens up the possibility of intermittent spraying processes, in which the SAP spray flow is limited to specific areas or sections of the drum former wheel's circumference. This results in a structured layering of the plies, where different areas can contain more or less SAP. In this way, plies with varying SAP concentrations and pulp content can be produced precisely according to product requirements.

[0017] The present patent application relates to a method and an apparatus for producing an absorbent core characterized by the targeted dosing and preferably intermittent application of superabsorbent polymers (SAPs) onto cellulose webs or layers. To better understand the concept, it is helpful to discuss preferred embodiments of some key terms:

[0018] Pulp is a material consisting primarily of cellulose fibers. It is typically used as the base for fibrous webs or layers in products such as diapers or sanitary napkins. Pulp has the ability to absorb liquid and thus forms the basis for absorbent products.

[0019] Superabsorbent polymers (SAPs) are materials capable of absorbing and binding many times their own weight in liquid. SAPs are available in powder or granule form, particularly as a spray-like particle or particle aggregate, and are frequently used in hygiene products to ensure high liquid absorption. During the absorption process (TERGAU & WALKENHORST, page 4), the material swells and transforms into a gel-like substance that securely encapsulates the liquid, preventing leakage. This gelling material plays a crucial role in the functionality of the products, as it binds the liquid even under pressure, ensuring dry surfaces and maximum wearing comfort. SAPs are therefore also referred to as gelling agents.

[0020] The absorbent core is the central layer of a product primarily responsible for liquid absorption. This core typically consists of a mixture of cellulose and SAP and is structured to effectively absorb liquids.

[0021] An absorbent product is a product designed to absorb liquids. This includes, among other things, diapers, sanitary napkins, and incontinence products, where the ability to absorb liquids is crucial.

[0022] Absorbent products are widely used in many areas of daily life and industry. Their primary function is to efficiently absorb and retain liquids or moisture. Among the most well-known applications are hygiene products such as baby diapers, adult incontinence products, sanitary napkins, and panty liners, all specifically designed to absorb bodily fluids like urine or menstrual blood and keep the user dry. Products like training pants, used for toddlers during potty training, and wipes, used for personal hygiene or cleaning purposes, also fall into this category.

[0023] Absorbent products also find diverse applications in industry. For example, cat litter is used to absorb urine and odors in litter boxes, while absorbent mats in hospitals and care facilities serve to absorb liquids from patient beds or floors. In the food industry, there are absorbent mats that help contain liquids during food transport, thus ensuring a hygienic environment. Products such as paper towels or sponges are also of great importance in cleaning technology for removing spills and keeping surfaces dry.

[0024] Furthermore, there are numerous technical applications where absorbent products absorb liquids such as oil, chemicals, or other substances from machinery and industrial environments. Moisture-proof mats protect furniture and floors from moisture damage, and special absorbent mattress pads prevent liquids from penetrating the underlying materials. In all these cases, absorbent products play a vital role in maintaining hygiene and preventing damage.

[0025] A drum former wheel is a rotating, cylindrical component used in the production of absorbent cores, such as those found in diapers or hygiene products. Its function is to evenly distribute a fibrous web or a mixture of fiber and superabsorbent material and apply it to a rotating drum surface. The surface of the drum former wheel can be perforated or textured to create a desired material structure. This structure ensures that the materials are processed into a cohesive layer as the drum rotates.

[0026] As an alternative to a rotating drum former wheel, a sieve belt structure that moves linearly, at least in sections, can be used, upon which the layers of the absorbent core are stacked. Similar to the drum former wheel, the sieve belt structure can have pockets or the like that define the outline of the core and are connected to a vacuum suction on the underside of the belt. In a preferred embodiment, the sieve belt is guided linearly past a flake box that conforms to the sieve belt and into which several feed lances for superabsorbent material project. The spray nozzles of the feed lances are arranged one behind the other in the longitudinal direction (direction of movement of the sieve belt) to create the desired multilayer structure of the core. In other words, at all points in this description (TERGAU & WALKENHORST, page 6) where a drum former wheel is mentioned, such a sieve belt structure can alternatively be used.

[0027] A flaking box is a component used in the production of absorbent cores. It serves as a container or channel for feeding fibrous materials (such as cellulose) to the drum former wheel. The flaking box controls the flow of cellulose, ensuring that it is applied evenly and in a controlled manner to the drum former wheel. Additionally, the flaking box can also be used to uniformly mix cellulose with superabsorbent polymers or other components to achieve the desired material properties for the absorbent core.

[0028] A feed lance is a tubular component in the production line of absorbent cores, used for the precise feeding of materials such as superabsorbents onto the rotating drum former wheel. The feed lance is connected to a spray nozzle that distributes the superabsorbent onto the material as a fine mist or droplets. The shape and size of the mist or droplets can be controlled by adjusting the nozzle, such as the spray angle or flow rate. Advantageously, the nozzle's spray cone can be adjusted to different widths, allowing for flexible and precise control of the material distribution.

[0029] A flow control device within the meaning of this application is understood to be a device that selectively influences the mass or volume flow of the superabsorbent (in particular, an airborne particle stream) towards the respective spray nozzle. The flow control device can, in particular, be switchable between an enabling position (material flow to the spray nozzle), a blocking position (no material flow to the spray nozzle), and, optionally, intermediate positions (reduced or partial material flow to the spray nozzle). Likewise, the flow control device can be configured to alternatively or additionally divert the material flow into a return line and / or a bypass line in order to prevent or reduce spray application without stopping the upstream metering process.The flow control device can be operated continuously or intermittently and can be used in particular for the generation of defined application windows in the longitudinal direction of the product (TERGAU & WALKENHORST page 7).

[0030] Besides the preferred disc valve, mechanical switching and throttling devices suitable for particle-laden gas flows are particularly suitable as flow control devices. Examples include slide valves, butterfly valves, ball valves, conical or plug-type slide valves, rotary valves, iris diaphragms, or other adjustable cross-sectional devices, as well as multi-way valves for switching between the spray line and the return line. Metering and discharge devices such as a rotary valve or a conveying device with an adjustable flow rate (e.g., a screw conveyor) can also function as flow control devices, provided that the necessary temporal modulation of the SAP (sealable gas) input for product structuring is achieved. In all cases, it is advantageous for the flow control device to have the shortest possible dead volume or residence time to allow for sharp edges of the application windows (start / stop) along the longitudinal direction.

[0031] Flow regulation can be achieved in various ways. In a first basic variant, the SAP flow is modulated binary (on / off), creating sections without SAP (pure pulp) and sections with SAP (pure SAP or SAP-pulp mixture) in each position. In a second variant, the SAP flow is modulated continuously or in steps, for example, by varying the cross-sectional opening, thereby generating defined gradients or step profiles of the SAP quantity along the longitudinal direction. In a third variant, the SAP flow is modulated by redirection (bypass / return), whereby the upstream pneumatic transport continues to operate stably, and only the proportion to the spray nozzle is varied. This allows for reproducible switching operations with low mechanical stress, particularly at high production speeds.

[0032] The flow control device can be passively actuated (e.g., spring-loaded, pressure-controlled) or, preferably, actively, for example, by means of a servo drive, stepper motor, pneumatic cylinder, magnetic drive, or a combination thereof. The control unit (TERGAU & WALKENHORST, page 8) can specify control variables such as valve stroke, flap angle, slide position, rotation angle, or speed. A clock signal or an angle or displacement signal (e.g., encoder on the drum former or the conveyor belt drive) can be used for synchronization with the product position. In intermittent operation, modulation can be particularly clock-synchronous, angle-displacement dependent, or cyclically with varying pulse width (PWM-like) to achieve the desired SAP distribution in the core.

[0033] Since superabsorbents are typically present as a particle stream, preferably pneumatically conveyed, it is advantageous for the flow control device to be abrasion-resistant, have low dead space, and be self-cleaning to prevent deposits or bridging. In a preferred embodiment, the flow control device features flow-optimized deflection geometries, wear-resistant linings (e.g., ceramic, hard metal, or coated metal-polymer surfaces), and purge air connections. Furthermore, monitoring of pressure, differential pressure, air mass flow, or valve position can be provided to detect blockages and adjust the control accordingly.

[0034] Insofar as a disc valve is described in the exemplary embodiments, it is understood that this represents only a particularly advantageous implementation of the flow control device. The effect essential to the invention—namely, individually controllable influencing of the SAP flow per injection lance, synchronized with the product position, to generate multilayered, longitudinally and Z or laterally structured core structures—can also be achieved with other flow control devices suitable for particulate flows. Corresponding variants are encompassed by the general concept of the invention, provided they enable sufficiently fast, reproducible, and positionally accurate modulation of the SAP application.

[0035] A disc valve, as the preferred implementation of a flow control device, is a mechanical component used for the precise control of the flow or supply of liquids or powders. It typically consists of one or more rotating discs, each with an opening or a series of openings. These discs are arranged to control the flow of materials, such as superabsorbents, by either releasing or blocking them.

[0036] In this case, longitudinal direction refers to the direction along the circumference of the drum former wheel, which in practice corresponds to the length of the (unwound) product. The longitudinal direction of a diaper (a preferred application) refers to the orientation along the body axis of the wearer, i.e., from back to front (or vice versa). This direction runs along the length of the diaper, with the rear part of the diaper positioned against the wearer's back and the front part on their front.

[0037] The transverse direction (or lateral direction) is the direction perpendicular to the longitudinal direction and corresponds to the width of the product.

[0038] Intermittent means that a process is repeated or interrupted at regular intervals. In relation to spray technology, this term specifically refers to the fact that SAP is not applied continuously, but in periodic cycles.

[0039] Preferred embodiments are the subject of the dependent claims and the following detailed description.

[0040] Advantageously, the arrangement and / or orientation of each injection lance relative to the drum former wheel is adjustable. This flexibility allows for precise control of the spraying process. The variable position of the lances enables targeted adjustment of the superabsorbent's distribution, resulting in an optimized material structure and uniform distribution.

[0041] In a preferred embodiment, the spray nozzle's exit angle and / or distance to the drum former wheel is adjustable. This adjustment allows for targeted control of the spray cone shape, thus enabling precise control of the superabsorbent's distribution (TERGAU & WALKENHORST, page 10). A variable distance is particularly advantageous for influencing the superabsorbent's mixing and, if necessary, adapting the superabsorbent's application to different types or quantities of pulp.

[0042] Advantageously, the spray cone of the nozzle is adjustable. This feature allows the spray area to be enlarged or narrowed as needed, enabling precise dosing of the superabsorbent. An adjustable nozzle ensures targeted control of the material distribution and an exact structure of the absorbent core.

[0043] In a preferred embodiment, the insertion lances and / or spray nozzles are adjusted by one or more actuators, preferably electric motors. The use of an actuator enables fast, precise, and automated adjustment of the lance position and nozzle setting. This leads to greater efficiency in the production process and ensures that the lances and nozzles are positioned exactly where they are needed. Manually operated adjustment mechanisms cannot offer the same flexibility and precision and involve more manual intervention, although this may be sufficient for some applications.

[0044] In one possible configuration, the feed lance extends at least partially into the flake box. This arrangement ensures that the lances come into direct contact with the pulp, promoting uniform and precise dosing of the superabsorbent and, if desired, mixing with the pulp. The closer the feed lance or its spray nozzle is positioned to the drum former wheel, the smaller the superabsorbent feed cone. This may be necessary or desirable, especially for short application lengths, or when a pure SAP layer is required. In other cases, however, it may be desirable and advantageous for the feed lance not to extend into the flake box, or only to a minimal extent, so that the feed lance does not, or only minimally, disrupt the flake flow.TERGAU & WALKENHORST Page 11 In a preferred embodiment, the feed lance is so narrow in cross-section that, when the spray nozzle is deactivated, it only imperceptibly affects the supply of pulp to the drum former wheel. This design ensures that the lances do not negatively affect the pulp supply when they are not active.

[0045] Advantageously, a dosing unit is provided that supplies each injection lance with an individually adjustable mass flow of superabsorbent. This feature enables precise control of the superabsorbent supply to each individual lance. As a result, the material structure of the absorbing core can be precisely adapted to the desired properties.

[0046] In a preferred embodiment, the dosing unit is based on the principle of a gravimetric differential dosing balance. This technology ensures precise and constant dosing of the superabsorbent, resulting in a uniform material distribution and an optimized structure of the absorbent core.

[0047] Advantageously, a single dosing unit is provided for all injection lances. This simplifies the production process and reduces the need for multiple separate dosing systems.

[0048] In a preferred embodiment, a disc valve used as a flow control device comprises a switching disc with a through-hole, actuated by a servo drive. This design enables fast and precise control of the flow, which is particularly advantageous in the production of cores with different material layers.

[0049] In a particularly advantageous variant, the disc valve comprises two counter-rotating discs. This design enables even more precise flow control and a faster response to changes in production control.

[0050] In a preferred embodiment, several units of injection lances with spray nozzles are arranged side by side in the axial direction of the drum former wheel (STERGAU & WALKENHORST, page 12) to form a lateral structure. This arrangement enables the individual formation of adjacent stripes in the absorbing core.

[0051] The invention further relates to a method for producing an absorbent core with multiple material layers for an absorbent product, comprising the steps:

[0052] • Feeding pulp through a flaking box to a rotating drum former wheel,

[0053] • Generating the application of superabsorbent via several injection lances with spray nozzles that can be positioned variably relative to the drum former wheel, • Controlling the application of superabsorbent by means of individually controllable flow control devices, in particular disc valves, which enable continuous or intermittent application,

[0054] • Synchronization of the rotary movement of the drum former wheel with the activation of the spray nozzles by controlling the flow control devices, in particular disc valves,

[0055] wherein several layers of material are produced on the drum former wheel, and wherein each of the layers of material is variably composed of a number of sections in the circumferential direction of the drum former wheel, each consisting of either pure cellulose, pure superabsorber or a mixture of cellulose and superabsorber.

[0056] Advantageously, the aforementioned steps of the process are carried out simultaneously. This simultaneous execution ensures efficient and time-saving production, as several process steps are performed at the same time without delays or interruptions. This simultaneous execution maximizes overall production efficiency and minimizes the time required.

[0057] In a preferred embodiment, the application of superabsorbent to at least one of the spray nozzles is intermittent. Intermittent application allows for precise control of the superabsorbent dosage, thus creating a precise material structure. This is particularly advantageous when different areas of the absorbent core require different amounts of superabsorbent.

[0058] Advantageously, at least one layer of material is formed in the longitudinal direction of the manufactured core, comprising a central section with superabsorbent material and an initial and final section of pure cellulose. The central superabsorbent section offers high absorption capacity, while the cellulose sections at the ends improve the stability and handling of the core.

[0059] In a preferred embodiment, the switching times of at least one of the disc valves are adjusted by a variable rotational speed of a switching disc, preferably even cyclically during a revolution, in order to control the spray time of the associated spray nozzle. By varying the rotational speed of the switching disc, the amount of superabsorbent at different points in the core can be controlled, resulting in better control over the structure and properties of the final product.

[0060] Advantageously, a gravimetric dosing unit is used to individually control the mass flow rate of the superabsorbent for each injection lance. A gravimetric dosing unit offers precise control over the amount of superabsorbent supplied, as the dosage is measured directly by the weight of the superabsorbent. This ensures a uniform and accurate distribution of the material, allowing for optimal adjustment of the quality and structure of the absorbent core.

[0061] In a preferred embodiment, the core is provided with a lower backsheet and / or a topsheet during the aforementioned steps or in a subsequent step. The addition of these backsheets to the absorbent core improves its stability, handling, and functionality. The topsheet ensures that liquids are quickly absorbed into the core, while the backsheet stabilizes the product and prevents leakage. The integration of these layers can be performed directly during the manufacturing process or as a subsequent step, depending on the requirements of the final product.

[0062] The advantages achieved with the invention lie particularly in the fact that the flexible control of the spray nozzles by means of flow control devices, especially disc valves, enables a high degree of variability in the product structure. In particular, different SAP proportions can be placed in different areas of the product, leading to a targeted improvement of the absorption properties. A further advantage lies in the ability to finely adjust the switching times and angles of the valves, thus enabling more precise control of the material distribution on the pulp web. The flexible adjustment of the spray parameters allows the process to be adapted to different product requirements, resulting in a wide range of product possibilities.This makes the process particularly suitable for the production of absorbent cores in applications with varying performance requirements, such as in diapers or other hygiene products, without significantly increasing the manufacturing effort.

[0063] In summary, the process and the device offer a number of advantages that significantly improve the efficiency and quality of the manufactured absorbent products:

[0064] Precise control of the superabsorbent material application significantly reduces its consumption, as the superabsorbent is only applied where it is actually needed. This is considerably more efficient than the usual application of a uniform layer across the entire surface. Furthermore, it prevents superabsorbent material from being applied to the cut edge between two articles, thus avoiding material waste and potential contamination. TERGAU & WALKENHORST Page 15. Another advantage lies in the targeted use of cellulose as a separating layer between a pure cellulose layer and a SAP or SAP blend layer. This separating layer promotes efficient liquid distribution within the core and prevents the formation of so-called "pinholes"—localized damage in the backsheet or topsheet. Such damage could lead to the release of gel-like particles, which would impair product quality and hygiene.

[0065] Furthermore, the device allows for a differentiated distribution of the superabsorbent, for example, with increased amounts on the product sides to improve the functionality of the upstanding cuffs. Simultaneously, the amount of superabsorbent on the sides can be reduced to minimize chafing and increase wearing comfort. This flexibility in material distribution not only ensures higher product quality but also better adaptation to user needs.

[0066] In a particularly advantageous embodiment, the device according to the invention comprises:

[0067] • a high-speed camera for capturing particle track images of a spray cone generated by at least one of the spray nozzles,

[0068] • an evaluation unit connected to or integrated into the high-speed camera and a control unit, wherein the evaluation unit is configured to determine velocity vectors of the sprayed particles from the recorded particle track images and to analyze a flow profile of the spray cone, and wherein the control unit, based on this analysis, readjusts the switching times of the respective flow control device, in particular the disc valve, in real time to ensure a precise adaptation of the spraying behavior of the spray nozzle to a target specification.

[0069] This design corresponds to an operating procedure in which the spray behavior of the respective spray nozzle is monitored and adjusted in real time by a high-speed camera and a computer-aided analysis of the visualized particle movement (TERGAU & WALKENHORST, page 16) in order to continuously adapt the spray behavior by adjusting the switching times of the flow control device, in particular the disc valve. A machine learning system is preferably used to eliminate image artifacts and to precisely determine the flow characteristics.

[0070] In a further preferred embodiment, a device according to the invention has a sensor unit comprising a microwave transmitter and a microwave receiver, which detects a density or height profile of a material application of cellulose and / or superabsorbent on a web, wherein the sensor unit is connected to a control unit on the data input side, and wherein the control unit sets or readjusts the switching times of the respective flow control device, in particular the disc valve, in order to ensure a precise adaptation of the spray behavior of the spray nozzle to a target specification.

[0071] In other words, the density profile of the web after the drum former is preferably captured using a microwave sensor. The density profile allows the location of the SAP (seed pressure) in the product to be determined. Based on this data, the electrical cam of the respective SAP metering disc (switching disc of the disc valve) can be adjusted. For example, all nozzles are adjusted sequentially in this way for the initial commissioning of a product (initial calibration). Furthermore, dynamic readjustment during ongoing operation is also possible (quality control).

[0072] As already mentioned, the present invention enables product variants that are considered to be independently novel and inventive. In this sense, the invention also includes an absorbent core for an absorbent product, having a longitudinal direction and a lateral direction, comprising at least one longitudinally oriented strip with at least two material layers, namely:

[0073] • a first material layer made entirely of cellulose, TERGAU & WALKENHORST page 17 • a second material layer with, viewed in the longitudinal direction, a central section of superabsorbent or of a mixture of cellulose and superabsorbent, and with two edge sections of cellulose,

[0074] • optionally a third material layer made entirely of superabsorbent polymer or a mixture of cellulose and superabsorbent polymer,

[0075] • optionally, a number of additional material layers.

[0076] In a further variant, which is considered to be independently novel and inventive, the invention relates to an absorbing core for an absorbing product, having a longitudinal direction and a lateral direction, comprising at least one longitudinally oriented strip with nine material layers, namely:

[0077] • a first, third, fifth, seventh and ninth layer of material made entirely of cellulose,

[0078] • in between each of these are a second, fourth, sixth and eighth layer of material, each having at least one section of superabsorbent or of a mixture of cellulose and superabsorbent, optionally with at least one further section of cellulose, in particular with two edge sections of cellulose.

[0079] Finally, the invention provides an absorbent product, in particular a diaper, incontinence pad or feminine hygiene product, comprising:

[0080] • a top sheet,

[0081] • a bottom cover layer (backsheet),

[0082] • an absorbing core arranged between the cover layers according to the above-mentioned type.

[0083] Several embodiments of the invention are explained in more detail below with reference to the accompanying, highly schematic drawings. TERGAU & WALKENHORST Page 18 FIG. 1 gives an overview of a system for producing an absorbent core for an absorbent product.

[0084] FIGS. 2 to 4 show variations of a nozzle system for the plant from FIG. 1.

[0085] FIG. 5 contains a legend for the following figures.

[0086] FIGS. 6 to 11 show different variants of the longitudinal product structure in longitudinal section for an absorbent product produced with the system according to FIG. 1.

[0087] FIGS. 12 to 17 show different variants of the lateral (or transverse) product structure in cross-section for an absorbent product produced with the system according to FIG. 1.

[0088] FIG. 18 shows a section through a disc valve and the surrounding piping system for use in the plant according to FIG. 1.

[0089] FIG. 19 shows an extension of the system according to FIG. 1 with a microwave sensor to provide a sensor signal for system control.

[0090] The apparatus 2, schematically depicted in FIG. 1, is used to produce an absorbent core for an absorbent product. As described in detail below, the absorbent core produced thus comprises several layers, each layer of which can in turn have segments or sections consisting of either cellulose, superabsorbent, or a cellulose-superabsorbent mixture. In at least one direction of the product, preferably longitudinally, different sections of this kind can be arranged consecutively within a layer. The apparatus 2 is designed to enable this with high reliability and great variability of the product, particularly with regard to the core structure.TERGAU & WALKENHORST Page 19 The material application, i.e., the layering of the individual layers, is carried out in a proven manner using a rotating drum, known as a drum former 10 or simply a drum former. Advantageously, one or more pockets 12 are located on the circumference of the drum former 10, each forming the outer edge of the core to be produced. Each pocket 10 comprises a suction or sieve structure (e.g., a perforated aperture) which is in flow communication with a vacuum suction inlet inside the drum former 10, so that the material to be deposited from the outside is advantageously actively drawn in and thus "held" against the drum circumference. Instead of several individual pockets 12, a continuous pocket 12 extending over the entire circumference can also be used to produce a core assembly, which is subsequently separated into several cores.

[0091] For the supply of pulp and superabsorbent to the drum former wheel 10, a pulp process and a superabsorbent process are implemented in the system 2, which are explained below in an exemplary manner.

[0092] First, the pulping process is considered in an exemplary implementation:

[0093] Raw pulp material is typically delivered in the form of rolls. The pulp is unwound from the rolls on a winding unit, which is typically not driven. The unwound pulp web is then fed to a hammer mill via a pulp feeder, which is typically integrated into the mill. Inside the hammer mill, the pulp undergoes defibration (fiber removal). For this process, the pulp is fed into the mill, which contains a rotating rotor with numerous teeth on its outer surface. The mechanical interaction with these teeth breaks down the incoming pulp web into individual pulp flakes (similar to chopping or shredding).

[0094] The details of the defibration process are not relevant here. In connection with system 2 according to FIG. 1, it is only important that a supply or flow of fiber flakes or cellulose flakes (fluff) is provided in a suitable manner (TERGAU & WALKENHORST, page 20). The cellulose flakes are fed to the drum former 10 via a fluff channel 14, which widens in the direction of flow to form a fluff box 16 that at least partially surrounds the drum former 10. The feed is advantageously supported or accomplished by an airflow generated by a blower in the direction of the drum former 10. Within the circumferential area limited by the fluff box 16, the fed cellulose flakes are deposited onto the rotating drum former 10, as already mentioned.

[0095] Let us now turn to the superabsorber process in an exemplary implementation:

[0096] Particulate superabsorbent polymer (also known as SAP) is typically delivered in large bags or sacks, so-called big bags. The big bags are emptied at an unloading station, and the superabsorbent polymer trickles into a hopper under its own weight. The superabsorbent polymer flowing from the hopper is then conveyed in batches into a separator tank using pneumatic or screw conveyors. This separator tank is typically located above a weighing hopper. The weighing hopper is continuously emptied. As soon as its fill level falls below a minimum (refill limit), a flap located between the separator tank and the weighing hopper opens, and the weighing hopper is filled with superabsorbent polymer. The weighing hopper is continuously weighed; this determines the weight loss or gain (delta mass over time).

[0097] The weighing container is open at the bottom and connected to a horizontal base plate with 1 to 20, typically 1 to 4, arcuate or crescent-shaped openings (feed openings) through which the superabsorbent material can flow. Immediately below this base plate, a gear-shaped metering disc of predetermined thickness rotates around the same central axis as the arcuate openings. The open space between the tooth flanks has the same radius to the central axis as the arcuate openings. At the same height and with approximately the same thickness as the metering disc, a spacer plate serves as an outer rim. This spacer plate has a cylindrical bore with a radius equal to the outer radius of the metering disc plus a small gap.

[0098] The dosing disc is driven by a speed-controlled electric motor. During rotation, the space between the tooth flanks is filled with superabsorbent material as soon as it is positioned below the corresponding feed opening. The rotation of the dosing disc then propels the superabsorbent material in a circular arc – while the upper feed opening is closed – and thus conveys it further below the closed base plate of the weighing container.

[0099] Immediately below the metering disc is a rigid discharge plate, which in turn has arc-shaped openings (discharge openings). The discharge openings are arranged in the same number and around the same central axis and with the same radius as the feed openings of the base plate, but offset from each other by an angle of rotation and never directly vertically below the feed openings. The rotation of the metering disc and the associated conveyance of the superabsorbent beneath the closed base plate inevitably brings the discharge openings into contact with the superabsorbent, causing it to fall out of the open tooth flanks through the discharge openings. Collection funnels are located below the discharge openings, which capture the outflowing superabsorbent and direct it into pipes – specifically, into the supply lines leading to the drum former wheel.

[0100] The result is a gravimetric dosing system (gravimetric differential dosing scale) for superabsorbents, in which the dosing quantity per unit of time, i.e., the dosing mass flow rate (kg / h), is controlled. This is achieved by regulating the speed of the dosing disc, depending on the weight loss of the weighing container.

[0101] In summary, the superabsorbent process is represented by a metering unit 18 (meter) for superabsorbent polymer shown in FIG. 1, with a plurality of outlets 20, each of which simultaneously provides an adjustable or controllable mass flow of superabsorbent polymer. In the present example, four outlets 20 are provided (two of which are shown), whereby the mass flow rate can be set the same for all outlets 20 or, alternatively, can be different depending on the requirements.

[0102] A feed line 24 for the superabsorbent mass flow, leading to the drum former wheel 10, is connected to each outlet 20 via a collecting funnel 22. After the superabsorbent exits the funnel, it is strongly accelerated by means of an injector 26, so that air velocities of preferably approximately 50 to 100 m / min are achieved in the feed line 24. For this purpose, the injector 26 advantageously has a Venturi nozzle, which, by means of a compressed air flow introduced from a blower, accelerates and entrains the injected superabsorbent particles accordingly (Venturi injector).

[0103] Further downstream, a so-called disc valve 30, as a preferred embodiment of a flow control device 80, is connected to the respective supply line 24. Depending on the valve position, this valve either allows the mass flow of superabsorbent to pass through to an injection lance 32 projecting into the flake box 16 with a spray nozzle 34 directed towards the drum former wheel 10, or it diverts the flow into a return line 36, thus preventing it from exiting at the spray nozzle 34 (only one of four return lines is shown here). With a corresponding valve position (intermediate position), partial recirculation with a correspondingly reduced spray quantity at the spray nozzle 34 can also occur.

[0104] For this purpose, the respective disc valve 30 according to FIG. 18 has a rotatably mounted switching disc 52 projecting into a flow channel and having (at least) one through-opening 54. The rotational position of the switching disc 52 about the axis of rotation 56 – and thus the position of the through-opening 54 – can be precisely adjusted by means of a coupled servomotor. When the through-opening 54 is in the open position, the air-carrying superabsorbent mass flow coming from the supply line 24 is allowed to pass essentially unimpeded to the feed lance 32 with the spray nozzle 34. Otherwise, when the through-opening 54 is in the closed position, this flow path is blocked, and the superabsorbent particles are deflected towards the return line 36 upon impact with the switching disc 52. For this purpose, the switching disc 52 is preferably inclined in the flow channel.As mentioned, intermediate positions between open and closed are also possible. The design and operation of the disc valve 30 correspond to those of EP 0 724417 B1, the disclosure of which is hereby incorporated into the present description.

[0105] As shown in FIG. 1, the unsprayed (unused) superabsorbent can be returned to the metering unit 18 or to a storage container upstream of the metering unit 18. The return is via the return line 36, into which a cyclone separator 40 with an exhaust air filter and, downstream, a buffer storage tank 42 with integrated level measurement are advantageously connected. A conveying system (not shown) is responsible for returning the particulate superabsorbent from the buffer storage tank 42 to the metering unit 18.

[0106] If necessary, further acceleration of the superabsorbent spray flow and / or the return flow can be provided downstream of the respective disc valve 30 by means of additional injectors 44, in particular Venturi injectors.

[0107] The respective feed lance 32 penetrates the boundary wall of the flake box 16 and carries a spray nozzle 34 at its end, directed towards the drum former wheel 10. The feed lance 32 is preferably made relatively thin so that, when the superabsorbent spray is switched off or blocked, it has as little influence as possible on the flow pattern of the cellulose flakes flowing in via the flake box 16. In other words, the flow shadow of the feed lance(s) 32 is as inconspicuous as possible in the cellulose flow pattern and in the cellulose deposition profile on the drum former wheel 10. The immersion depth of the respective entry lance 32 into the flake box 16 and / or the distance of the spray nozzle 34 to the drum former wheel 10 are advantageously adjustable or changeable - for example by a manual adjustment mechanism, but preferably TERGAU & WALKENHORST page 24 by an electrically or pneumatically driven adjustment drive.The same advantageously applies to the spray pattern of the spray nozzle(s) 34, which is preferably adjustable - in particular with regard to the longitudinal and / or lateral extent of the spray cone 48 and thus the impact area 46.

[0108] The distance between the spray nozzle 34 and the drum former wheel 10, and the nozzle geometry, define a spray cone 48 of superabsorbent and a corresponding application area or impact area 46 of superabsorbent on the drum former wheel 10. If the distance between the spray nozzle 34 and the drum former wheel 10 is relatively large, the superabsorbent spray mist mixes relatively evenly with the incoming cellulose fluff when the disc valve 30 is open. Accordingly, a cellulose-superabsorbent mixture (fluff & SAP mixture) collects in the impact area 46 and forms a layer. The mixing ratio can be influenced by varying the distance and / or the flow parameters (flow velocity, etc.). However, if the aforementioned distance is relatively small, the impact area 46 lies in the flow shadow of the spray nozzle 34.In this case, with the disc valve 30 open, the superabsorbent spray mist dominates and blocks the inflow of cellulose flakes in the area of ​​the spray cone 48. Accordingly, a layer of nearly pure superabsorbent polymer (SAP) forms in the impact area 46. Regardless of the distance of the spray nozzle 34 to the drum former wheel 10, with the disc valve 30 closed, i.e., when no superabsorbent spray mist is present, a pure cellulose layer (fluff) forms in the corresponding area on the drum former wheel 10.

[0109] In the example shown in FIG. 1 (and similarly enlarged in FIG. 2), four independently controllable spray nozzles 34 are arranged side by side or one behind the other in the flake box 16, circumferentially around the drum former wheel 10, such that their impact areas 46 do not overlap, but are spaced apart from each other, either side by side or one behind the other in the circumferential direction on the drum former wheel 10. Assuming that the distance of all spray nozzles 34 to the drum former wheel 10 is relatively large (see above) and that all disc valves 30 are permanently open, a 9-layer material accumulation forms on the drum former wheel 10, starting with a first (bottom) layer of fluff, then alternating layers of fluff and SAP mixture and fluff (this sequence is repeated four times), so that the last (top) layer is again fluff.Due to the permanently open disc valves 30, which means that all spray nozzles 34 spray continuously, all layers are continuous and uniform in the longitudinal direction of the absorbing core thus formed, provided that – as assumed here – the circumferential direction of the drum former wheel 10 corresponds to the longitudinal direction of the core. The arrangement of the layers from this example is shown in FIG. 6 in the bottom diagram in longitudinal section.

[0110] In one variation, as shown in FIG. 3, all four spray nozzles 34 are located so close to the drum former wheel 10 that pure SAP layers form in the respective impact area 46. This results in a total of 9 layers of material being deposited on the drum former wheel 10, starting with a first (bottom) layer of fluff, then alternating layers of SAP and fluff (four times), so that the last (top) layer is again fluff. Here, too, permanently open disc valves 30 and correspondingly continuous longitudinal spray applications are assumed. The layer structure from this example is shown in FIG.

[0111] Figure 8 is shown in the longitudinal section of the bottom diagram.

[0112] In another variation, one or more spray nozzles 34 are arranged relatively close to the drum former wheel 10 and produce pure SAP layers, while one or more spray nozzles 34 are located relatively far from the drum former wheel 10 and produce layers of fluff & SAP mixture.

[0113] In another variation, for example, the impact area 46 of the spray nozzle 34 on the left outer edge extends to the boundary wall of the flake box 16, so that the first (bottom) layer of cellulose is omitted, resulting in a total of 8 layers. Alternatively or additionally, the last (top) layer of cellulose can also be omitted if the impact area 46 of the spray nozzle 34 on the right outer edge extends to the boundary wall of the flake box 16. Alternatively or additionally, the impact areas 46 of adjacent spray nozzles 34 can be directly adjacent to each other (without a gap), so that corresponding intermediate cellulose layers are omitted (as, for example, in the four-day variants according to FIGS. 10 and 11). With four effective and operational spray nozzles 34, it is therefore always possible to produce fewer than 9 layers by appropriately adjusting the impact areas 46, i.e., only 8 layers, 7 layers, ..., down to just one layer - which is of course also possible if one or more spray nozzles 34 are not in operation, i.e., are not spraying (corresponding to the closed position of the associated disc valve 30).

[0114] FIG. 4 shows another variation in which the impact areas 46 of several spray nozzles 34 overlap at least partially, resulting in SAP-containing layers with different SAP concentrations. In this example, a total of 9 layers are formed, including three pure cellulose layers (one as the bottom layer and another as the top layer).

[0115] The number of four spray nozzles 34 is particularly advantageous because it allows for a high degree of product variability with reasonable effort. However, the aforementioned basic principles can, of course, also be implemented with more or fewer than four SAP spray nozzles 34, starting with one, two, three, ... spray nozzles 34 up to five, six, ... spray nozzles 34, etc. (the number is limited by the installation space available in the flake box 16). Advantageously, each spray nozzle 34 has its own supply line 24, which can be supplied with an adjustable SAP mass flow and has an individually controllable disc valve 30. However, coupled control of several disc valves 30 is also possible.

[0116] In the preceding description, it was generally assumed that the respective disc valve 30 is permanently open, and thus the associated spray nozzle 34 sprays continuously. However, the motorized drive of the switching disc 52 by means of a servo drive (comprising a servo motor and a servo controller) also allows for intermittent SAP spray flows, enabling even greater product versatility. TERGAU & WALKENHORST Page 27 In a typical application, for example, the switching disc 52 of the disc valve 30 is rotated periodically, with its rotational speed being matched to the rotational speed of the drum former wheel 10. By selecting a suitable width for the passage opening 54 in the switching disc 52, the SAP spray operation can be restricted to a predetermined angular range or circumferential section relative to the drum former wheel 10.This typically results in the SAP (synthetic solvent) content in the corresponding layer being limited to a portion of the total longitudinal extent of the manufactured absorbent core, while the remaining portions are filled with pure cellulose. In other words, the corresponding layer contains SAP (pure SAP or fluff & SAP mixture) only in a central region, whereas the longitudinal beginning and end regions consist of pure cellulose. The longitudinal extent of the different areas or regions can vary or be the same for different layers. Examples of such a layer structure are shown, among others, in the upper three diagrams of FIGS. 6, 8, and 10, as well as in the longitudinal section diagrams of FIGS. 7, 9, and 11.

[0117] The control unit 50 enables the synchronization and control of various processes. In particular, it ensures that the rotary movement of the drum former wheel 10 and the activation of the spray nozzles 34 by the disc valves 30 are coordinated to guarantee precise and targeted material application. This unit allows the switching position of the disc valves 30 to be controlled synchronously with the rotation of the drum former wheel 10, which is crucial for the desired structuring of the material layers. The control unit 50 can be implemented in various ways, for example, by a central control unit or a networked system that expediently monitors and adjusts all necessary parameters. The control unit 50 acts, in particular, on an actuator 82, specifically a servo drive for the respective disc valve 30 and the drive of the drum former wheel 10 (in FIG.1 illustrated by dashed arrows). In the case of regulation, the control unit 50 receives measured values ​​via suitable sensors, for example regarding the rotational position of the drum former wheel 10 and the switching disc 52 of the respective disc valve 30. TERGAU & WALKENHORST Page 28.

[0118] To control or regulate the switching times of the respective disc valve 30, real-time monitoring of the spray behavior of the associated spray nozzle 34 can be provided. For this purpose, a sequence of images of the spray cone 48 or a section thereof is continuously generated using a digital high-speed camera 60 (see FIG. 1) and evaluated in an evaluation unit 62, which can be part of the control unit 50 and / or communicate with it as an external unit – preferably in real time.

[0119] A high-speed camera (60) is a specialized camera system capable of capturing an extremely high number of images per second (frames per second, FPS), often several thousand or even millions of FPS. It works by controlling the shutter and image sensor to capture light in very short intervals. Modern high-speed cameras utilize digital sensors and high-performance storage media to quickly process and store the vast amount of image data. These cameras are used to visualize rapid movements that are imperceptible to the human eye.

[0120] By precisely setting the defined shutter speed of the high-speed camera 60, the sprayed superabsorbent particles are depicted in each image as a multitude of particle tracks as they travel from the nozzle outlet to the point of impact. This technique shows the movement of the particles over time by recording their positions or trajectories in a sequence of images (particle track image or flow pattern image). The length of each particle track is a measure of the particle's velocity. The direction of flight or flow can be determined from the angular orientation of the track. Taken together, this establishes a velocity vector for each particle.

[0121] Automated image analysis in the evaluation unit 62 determines a velocity vector (tracking) for a large number of sprayed particles, ideally for each one, preferably for each image in the sequence. From this, the flow profile or spray pattern of the spray nozzle 34 – also under the influence of mixing with cellulose flakes and the surrounding airflow – can be determined using suitable mathematical methods, in particular statistical methods. From this, the deposition behavior of superabsorbent particles and, if applicable, cellulose in the impact area on the drum former wheel 10 can be derived and analyzed, for example, with regard to particle density, extent of the spray spot in longitudinal and lateral directions, mixing ratio, etc.

[0122] Through machine learning, especially through the use of artificial intelligence, image artifacts and / or (foreign) particles that are not relevant to the flow characteristics in question can be eliminated or discarded during evaluation.

[0123] The entire evaluation can be performed live, i.e., in real time, using computer-aided processes and fed back into the control of the switching time of the respective disc valve 30, thus preferably implementing a control loop. This allows for a comparison of the current spray or application characteristics with the target specification at any time and for adjustments to be made accordingly, if necessary.

[0124] Regarding the longitudinal cross-sectional views of the product structure, it should be noted that they depict the material layers between an upper and lower cover sheet (top sheet and back sheet). These are, for example, webs of textile material. This so-called "core-wrap" arrangement can be carried out directly on the drum former wheel 10 by feeding corresponding webs for the formation of the cover sheets before and after the described material application. However, it can also be carried out further downstream in the process, for example, if only the "core" of cellulose and SAP is produced on the drum former wheel 10 and then transferred to another system or system section for wrapping between the cover sheets.It is also possible, for example, to form the material application on a nonwoven web or other web or web layer or on a backsheet on the drum former wheel 10TERGAU & WALKENHORST page 30 and to apply (e.g. by laminating) the topsheet in a later process step away from the drum former wheel 10.

[0125] Furthermore, it should be noted that in the cross-sectional views, the longitudinal product length is (arbitrarily) assigned to a total cycle angle of 360° + 30° = 390° and divided into 13 segments of 30° each. This results in the depicted brick-like structure of the layers, whereby each brick or "block" according to the legend in FIG. 5 consists of either pure cellulose (fluff), pure superabsorbent polymer (SAP), or a mixture thereof (fluff & SAP mixture). For example, a cycle angle of 360° corresponds to a full rotation of the switching disc 52 of the respective disc valve 30. It also corresponds to a certain, possibly entirely different, angle of rotation or a length of a circumferential section of the drum former wheel 10.

[0126] The division into cycle segments of 30° is arbitrary and serves only to illustrate the concept in the diagrams. In reality, depending on the width of the opening 54 and the rotational speed / control of the switching disc 52, all possible switching times or cycle angles (including all possible intermediate values) can be achieved, potentially even differently for each position. Consequently, the brickwork structure shown here as an example is an idealized concept and, as such, may not be directly derived from the actual product.

[0127] A further generalization towards arbitrarily adjustable switching times of the respective disc valve 30 is achieved by varying the rotational speed of the switching disc 52 within one revolution through suitable electronic control or regulation of the servo drive. For example, (preferably with a constant period for one revolution) the opening time of the disc valve 30 can be increased compared to the closing time if the rotational speed is reduced in the open position of the passage opening 54, but increased in the closed position. The process is repeated cyclically with each revolution.This electronic control, which is a counterpart to the mechanical cam drive, thus achieves an effect (TERGAU & WALKENHORST, page 31) that would otherwise only be possible with a substantially constant rotational speed by replacing the switching disc 52 with a new switching disc 52 with a larger or wider opening 54. It can be said that the electronic cam drive, in which the motor speed is regulated depending on the repeating product position, "virtually" enlarges (or alternatively reduces) the opening 54 perceptible to the product flow by means of analogous measures.

[0128] Additionally or alternatively, extended control options for the switching times arise with a disc valve 30 with two counter-rotating (or alternatively co-rotating) switching discs 52 arranged one behind the other, each with at least one through-hole in the disc surface. Since such a valve only allows the product flow to pass through when both through-holes are essentially aligned, the duration for which this is the case can be varied by appropriately adjusting the rotational speeds of the two switching discs 52.

[0129] In the lateral product direction, perpendicular to the longitudinal direction, the layers can also be structured. In the simplest case, if the flake box 16 covers the entire width of the absorbent core to be produced in the lateral (transverse) direction and the spray nozzles 34 also have a correspondingly wide spray cone, all layers extend uniformly and continuously from left to right. However, if the spray cone 48 is set narrower, SAP (synthetically active particle) is only deposited in the corresponding impact area 46, for example, in a lateral central region. On the outside, in the lateral edge regions, there are then pure cellulose areas.

[0130] To achieve even greater variability, the lateral extension can be divided into several adjacent lanes or strips, with each strip having its own independently controllable nozzle system as shown in FIG. 1. This means that the nozzle arrangement from FIG. 1 is essentially duplicated or multiplied according to the number of strips. This allows, in principle, the freedom to define a layer structure for each strip independently and to produce it as described on page 32 of TERGAU & WALKENHORST. In the idealized view of longitudinal and transverse segments, this results in a quasi-3D brickwork structure with freely definable "bricks" (fluff, SAP, or fluff & SAP mixture) that can be realized through suitable rotary control. FIGS. 12 to 17 provide an impression of the variety of possible lateral product structures.

[0131] In summary, this describes in particular a method and a device for producing an absorbent core with several SAP-containing layers, which are applied at least partially intermittently to a fiber web or cellulose layer.

[0132] FIG. 19 shows an extension of the system 2 known from FIG. 1, in which a web 64 of the absorbent product produced on the drum former wheel 10 is guided past or through a sensor unit 68 via an optional deflecting roller 66. The sensor unit 68 can, in particular, comprise a microwave sensor with a microwave transmitter 70 on one side of the web 64 and a microwave receiver 72 on the other side of the web 64. Both are positioned and configured such that the transmission of microwaves through the web 64 is measured, allowing the thickness of the material deposit at the measuring point to be determined from the signal strength or attenuation. This enables the creation of a density profile or thickness profile of the material over the length of the web (corresponding to the rotation angle of the drum former wheel 10), as schematically illustrated in the upper diagram of FIG. 19.This thickness profile correlates with the switching disc control of the disc valve 30, which is also plotted as a function of the running length in the lower diagram of FIG. 19 - here using the example of a single injection lance 32 for superabsorber SAP1.

[0133] As a purely illustrative example, a scenario is presented in which the switching disc 52 is first closed, then opened, and finally closed again along the length of a product, corresponding to an SAP application in a central area of ​​the product (and only there). The cellulose application onto the nonwoven web, on the other hand, occurs over a longer time window, both before, during, and after the SAP application, corresponding to the circumference (angle) covered by the flaking box (TERGAU & WALKENHORST, page 33, 16) on the drum former wheel 10. Accordingly, the height or thickness profile of the material detected by the microwave sensor exhibits three height levels in this example, corresponding to the contribution of the nonwoven web, the cellulose application, and the SAP application (including any mixing areas).A small time delay in the SAP signal between the lower (control) diagram and the upper (measurement) diagram results from the distance between switching disk 52 and drum former wheel 10.

[0134] The details of the measurement and evaluation are variable. For example, instead of microwaves, another type of electromagnetic radiation can be used that allows for the detection of material deposition. It is important that the sensor signal or measurement signal from the sensor unit 68 is received as an input by the control unit 50 in order to adjust, almost instantaneously, parameters of the system 2, such as, in particular, the switching times of the disc valves 30, with regard to a desired target. The target can, in particular, be a specific longitudinal product structure as shown in FIGS. 6 to 11. Even while the current product length is being measured, a deviation of the product structure from the target state can be detected, and this deviation can be counteracted by appropriately adjusting adjustable system parameters for the (immediately or indirectly) subsequent product length. This enables very rapid adjustment with minimal rejection or scraping.TERGAU & WALKENHORST Page 34.

[0135] Reference symbol list

[0136] 2 Annex

[0137] 10 Drumformer wheel

[0138] 12 bags

[0139] 14 Flake Channel

[0140] 16 flake boxes

[0141] 18 dosing units

[0142] 20 outlet

[0143] 22 collecting funnels

[0144] 24 Supply line

[0145] 26 injectors

[0146] 30 disc valve

[0147] 32 Entry lance

[0148] 34 spray nozzle

[0149] 36 Return line

[0150] 40 cyclone separators

[0151] 42 buffer storage tanks

[0152] 44 injectors

[0153] 46 Impact area

[0154] 48 spray cones

[0155] 50 control unit

[0156] 52 Switch disc

[0157] 54 Passage opening

[0158] 56 Rotation axis

[0159] 60 High-speed camera 62 Evaluation unit

[0160] 64 lane

[0161] 66 Pulley

[0162] 68 sensor units

[0163] 70 microwave transmitters

[0164] 72 microwave receivers

[0165] 80 Flow regulator TERGAU & WALKENHORST Page 35

[0166] 82 Actuator

[0167] 84 Particle track image

[0168] 86 Velocity vector 88 Flow profile

Claims

TERGAU & WALKENHORST Page 36 Claims 1. Device for producing an absorbent core with multiple layers of material for an absorbent product, comprising: • a rotating drum former wheel (10) during operation or a linearly moving sieve belt structure, • a flaking box (16) for feeding cellulose to the drum former wheel (10) or to the sieve belt structure, • one or more, preferably at least two, variable-position injection lances (32) relative to the drum former wheel (10) or the sieve belt structure, each with a spray nozzle (34) for superabsorbent, where • each entry lance (32) is assigned an individually controllable flow control device (80), in particular a disc valve (30), for a continuous or intermittent supply of superabsorbent, • Each spray nozzle (34) in operation produces a spray cone (48) with an impact area (46) on the drum former wheel (10) or on the screen belt structure, wherein the impact areas (46) can be variably positioned as adjacent, overlapping or spaced apart in the circumferential direction of the drum former wheel (10) or in the longitudinal direction of the screen belt structure in order to enable targeted structuring of the material layers, • a control unit (50) is provided which synchronizes the rotary movement of the drum former wheel (10) or the linear movement of the sieve belt structure and a switching position of the flow control devices (80), so that the core to be produced has several layers of material, each of which, viewed in the circumferential direction of the drum former wheel (10) or in the longitudinal direction of the sieve belt structure, is variably composed of a number of sections, each consisting of either pure TERGAU & WALKENHORST page 37 cellulose (fluff), pure superabsorbent polymer (SAP), or a mixture of cellulose and superabsorbent polymer (fluff & SAP).

2. Device according to claim 1, wherein the arrangement and / or orientation of the respective entry lance (32) relative to the drum former wheel (10) or the sieve belt structure is adjustable.

3. Device according to claim 1 or 2, wherein the distance and / or the exit angle of the respective spray nozzle (34) to the drum former wheel (10) or to the sieve belt structure is adjustable.

4. Device according to one of claims 1 to 3, wherein the spray cone (48) of the respective spray nozzle (34) is adjustable.

5. Device according to one of claims 2 to 4, wherein the respective setting is made by an actuator (82).

6. Device according to one of the preceding claims, wherein the respective entry lance (32) projects at least partially into the flake box (16).

7. Device according to one of the preceding claims, wherein the respective feed lance (32) is so narrow in cross-section and / or flow-optimized that, in particular when the spray nozzle (34) is deactivated, it only imperceptibly influences the supply of pulp to the drum former wheel (10) or to the sieve belt structure.

8. Device according to one of the preceding claims, wherein a metering unit (18) is provided which supplies each entry lance (32) with an individually adjustable mass flow of superabsorbent.

9. Device according to claim 8, wherein the dosing unit (18) is based on the principle of a gravimetric differential dosing scale.

10. Device according to claim 8 or 9, wherein a common metering unit (18) is provided for all injection lances (32), wherein the common metering unit (18) preferably generates several identical mass flows of superabsorbent. TERGAU & WALKENHORST Page 38 11. Device according to any one of the preceding claims, wherein the respective flow control device (80) is a disc valve (30) comprising a switching disc (52) actuated by a servo drive with a through-opening (54).

12. Device according to claim 11, wherein the respective disc valve (30) comprises two counter-rotating switching discs (52).

13. Device according to one of the preceding claims, wherein for lateral structure formation several units of entry lances (32) with spray nozzles (34) are arranged next to each other in the axial direction of the drum former wheel (10) or in the transverse direction of the sieve belt structure.

14. Device according to any one of the preceding claims, comprising: • a high-speed camera (60) for capturing particle track images of a spray cone (48) generated by at least one of the spray nozzles (34), • an evaluation unit (62) which is connected to or integrated into the high-speed camera (60) and a control unit (50), wherein the evaluation unit (62) is configured to determine velocity vectors (86) of the sprayed particles from the recorded particle track images (84) and to analyze a flow profile (88) of the spray cone (48), and wherein the control unit (50) adjusts the switching times of the respective flow control device (80) in real time on the basis of this analysis in order to ensure a precise adjustment of the spraying behavior of the spray nozzle (34) to a target specification.

15. Device according to one of the preceding claims with a sensor unit (68) comprising a microwave transmitter (70) and a microwave receiver (71), which detects a density or height profile of a material application of cellulose and / or superabsorbent on a web (64), wherein the sensor unit (68) is connected to a control unit (50) on the data input side, and wherein the control unit (50) readjusts the switching times of the respective flow control device (80) to ensure precise adaptation of the spray behavior of the spray nozzle (34) to a target specification. TERGAU & WALKENHORST Page 39 16. Method for producing an absorbent core with multiple material layers for an absorbent product, comprising the steps: • Feeding pulp through a flaking box (16) to a rotating drum former wheel (10) or a linearly moving sieve belt structure, • Generating an application of superabsorbent by means of several injection lances (32) with spray nozzles (34) which can be positioned variably relative to the drum former wheel (10) or the sieve belt structure, • Control of the application of superabsorbent by means of individually controllable flow control devices (80), in particular disc valves (30), which enable continuous or intermittent application, • Synchronization of the rotary movement of the drum former wheel (10) or the linear movement of the sieve belt structure with the activation of the spray nozzles (34) by controlling the flow control devices (80), wherein several layers of material are produced on the drum former wheel (10) or the sieve belt structure, and wherein each of the layers of material is variably composed of a number of sections, as seen in the circumferential direction of the drum former wheel (10) or in the longitudinal direction of the sieve belt structure, each consisting of either pure cellulose (fluff), pure superabsorbent polymer (SAP), or a mixture of cellulose and superabsorbent polymer (fluff & SAP).

17. The method of claim 16, wherein the aforementioned steps are carried out simultaneously.

18. Method according to claim 16 or 17, wherein the application of superabsorbent to at least one of the spray nozzles (30) is intermittent.

19. Method according to claim 18, wherein in the longitudinal direction of the produced core at least one layer of material is formed with a central section containing proportions of superabsorbent and with a beginning and end section made of pure cellulose.

20. A method according to any one of claims 16 to 19, wherein the flow control devices (80) are formed by disc valves (30), and wherein the switching times of at least one of the disc valves (30) are preferably cyclically adjusted by a variable rotational speed of a switching disc (52) during one revolution in order to control the spray time of the associated spray nozzle (34).

21. A method according to any one of claims 16 to 20, wherein a gravimetric metering unit (18) is used to individually control the mass flow of the superabsorbent for each injection lance (32).

22. Method according to any one of claims 16 to 21, wherein the Kem is provided with a lower cover layer (backsheet) and / or with an upper cover layer (topsheet) during the aforementioned steps or in a subsequent step.

23. Method according to one of claims 16 to 22, wherein real-time monitoring and adjustment of the spray behavior of the respective spray nozzle (34) is carried out by a high-speed camera (60) and a computer-aided analysis of a particle movement visualized therein, in order to continuously adjust the spray behavior by adjusting the switching times of the flow control device (80).

24. Method according to claim 23, wherein a machine learning system is used to eliminate image artifacts and to precisely determine the flow characteristics.

25. Method according to one of claims 16 to 24, wherein the application of cellulose and / or superabsorbent to a web (64) is measured by means of a sensor unit (68), in particular with a microwave sensor, and a resulting measurement signal is used as an input variable in a control unit (50) for controlling the flow control devices (80).

26. Absorbing nucleus for an absorbing product, having a longitudinal direction and a lateral direction, comprising at least one longitudinally oriented strip with at least two material layers, namely: a first material layer made entirely of cellulose (fluff), TERGAU & WALKENHORST page 41 • a second material layer with, viewed in the longitudinal direction, a central section made of superabsorbent polymer (SAP) or of a mixture of cellulose and superabsorbent polymer (fluff & SAP), and with two edge sections made of cellulose (fluff), • optionally a third material layer made entirely of superabsorbent polymer (SAP) or of a mixture of cellulose and superabsorbent polymer (Fluff & SAP), • optionally, a number of additional material layers.

27. Absorbing core for an absorbing product, having a longitudinal direction and a lateral direction, comprising at least one longitudinally oriented strip with nine material layers, namely: • a first, third, fifth, seventh and ninth layer of material made entirely of cellulose (fluff), • in between each of these layers are a second, fourth, sixth and eighth layer of material, each of which has at least one section of superabsorbent polymer (SAP) or of a mixture of cellulose and superabsorbent polymer (Fluff & SAP), optionally with at least one further section of cellulose (Fluff), in particular with two edge sections of cellulose (Fluff).

28. Absorbent product, in particular a diaper, incontinence pad or feminine hygiene product, comprising: • a top sheet, • a bottom cover layer (backsheet), an absorbing keratin arranged between the cover layers according to claim 24 or 25.

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