An apparatus and method for forming air-laid absorbent cores

TECHNICAL FIELD [0001] The present invention relates to a device for forming an air-deposited absorbent body, comprising a first and a second mat forming wheel, each of the mat forming wheels having at least one mold on its peripheral surface, air applying means for supplying material fibrous entrained in the stream of air into the molds on each mat forming wheel, suction means holding the molded insert elements in the respective molds on a part of the mold path on the respective mat forming wheel and means for superimposing the insert element on the first mat forming wheel and the insert element on the second mat forming wheel and how to use such device.

BACKGROUND ART [0002] Devices of the type described above are used to produce multi-layer absorbent pads in which at least one layer contains separate particles of highly absorbent material, preferably so-called super absorbent material (SAP, superabsorbent material) that can absorb liquid in an amount several times its own weight. The fibers in the layers are preferably cellulose and produced in the process of pulp defibrillation. In addition, other types of fiber may be added. The fibers in different layers can be the same or different.

[0003] The devices of the present invention should be placed in a production line for the production of absorbent articles, such as disposable diapers, sanitary napkins, urological pads and the like sanitary products. It is therefore important that such devices do not take up much space, especially in the length direction of such a production line. At present, the efficiency of such production lines is high, about 600 cartridges per minute, and the present invention aims to enable even higher efficiency. At such high speeds, centrifugal forces acting on separate particles in the formed elements of the cartridges are quite large and there is a problem of preventing these particles from falling out of such elements of the cartridges. In addition to the costs of losing expensive particulate material, there is a risk that lost particles will fall on parts or devices in the production line and adversely affect their functions and the environment. Lost particles need to be handled somehow. There is therefore a need to keep such particle loss as low as possible.

[0004] Another problem is to ensure that the elements of the cartridges formed on a suitable wheel for forming the mat of the device, of the type described in the introduction, are superimposed in a desired arrangement with respect to each other. For example, if the front edges of the applied elements of the cartridges are to be aligned, there will be no such alignment

EP 2 043 576 B1 very visible and also adversely affect the function of the article being manufactured. For example, if the manufactured article contains holes etc. in complex cartridges that should coincide or be in a fixed relationship with each other in the folded position of the cartridge components, the lack of overlap of these holes will have an adverse effect on the functioning of the manufactured article.

[0005] Another problem with the device described in the introduction is that there is a risk that separate particles applied by air to the mold will damage or block or clog some of the holes in the mold. Such blockage or clogging leads to an uneven distribution of the air-applied material in the mold and, as a consequence, will negatively affect the absorbent properties of the manufactured article.

[0006] EP-B1-0 958 801 discloses a device in which a fabric is wound on a mat-forming wheel and attracted to the mold walls on a circumferential surface of the wheel. Then, a layer of separate particles is air-laid in the mold, and fibers entrained in the air stream are attracted to this layer of separate particles to mix with the separate particles. In Figure 3 of this document, such a device is disclosed comprising two mat forming wheels. The air-applied bodies are supplied from each of the wheels to form a fabric mat, and then the two tissue paper and attached bodies are folded together. The bodies attached to the fabrics move quite long distances without being affected by the suction means and there is a high risk that the particles fall out of the bodies during the movement. In addition, with such a construction, it appears that it is difficult to achieve high accuracy in the mutual arrangement of bodies attached to fabrics when they are folded together.

[0007] EP-B1-1 082 081 discloses a device according to the preamble to claim 1. In such a device, only fiber material is air-applied on the first mat forming wheel to form the body onto which from the second mat forming wheel a second body consisting of a mixture of fibrous material and separate SAP particles is transferred while the body is still in shape. A third layer of fibrous material is then applied by air to the first two bodies assembly. When transferring the second body to the first body, part of the second body is always in free air exposing both sides. There is therefore a great risk that SAP particles will fall out of these exposed parts of the second body, especially if their concentration in the second body is high and the speed of the mat forming wheels is also high. After transferring the second body to the first body, the third air-applied layer will prevent SAP particles from falling out of the second body. Although the position accuracy of the folding bodies is improved by the fact that the first body is kept in its form when moving the second body onto it, the second body must move in free air before being applied to the first body, which reduces accuracy. In addition, there is no mat in the second wheel

EP 2 043 576 B1 means to prevent blocking or clogging the openings in the bottom of these molds by separate particles applied by air to the molds.

[0008] Sanitary absorbent articles, such as diapers, are often supplied in various sizes. When different insert sizes for the same absorbent article to be produced are to be produced on the same device as in the device described in the introduction, the molds in the mat forming wheels should be replaced. It is a time-consuming operation, which also includes storage of various forms not used for the production of the current size, which reduces the economic efficiency of the production process, especially with short production runs.

[0009] For such articles, it is preferred that they contain cartridge elements with a large amount of SAP particles (greater than 50%) mixed with the fibrous material. The problem with so many SAP particles in the cartridge element is to reduce the strength of the cartridge element. The risk of losing SAP particles during forming and transferring such elements is of course increased.

[0010] Due to the above-mentioned risk of loss of SAP particles and the risk of damage to formed cartridges during handling and manipulation due to the reduced strength of the cartridge element with a high content of SAP particles, devices for forming such cartridges, such as mat forming wheels, are placed in a production line for the production of sanitary articles, so that the transfer distance of a cartridge element manufactured on wheels, between forming and further processing the insert is very small. Since the mat forming wheels are large elements, it would be beneficial if these elements could be placed at a distance from other elements in the production line, so that the available space could be used most efficiently.

[0011] The object of the present invention is to increase the accuracy of transferring one cartridge element to another in the device described in the introduction, to prevent damage and / or clogging of the molds by separate air-applied particles, and to prevent excessive loss of separate particles from the formed element components. Furthermore, it is an object of the present invention to limit the need to change molds when different sizes of the same product are to be manufactured. It is also an object of the present invention to allow high concentrations of SAP particles in cartridge elements and to reinforce formed cartridges so that they are capable of displacement without the risk of loss of SAP particles or damage due to displacement. Also, it is an object of the present invention to achieve these goals without significantly increasing the space required for the device in the production line for the production of sanitary absorbent articles.

SUMMARY OF THE INVENTION

[0012] These objectives are achieved by a device for forming air-absorbent absorbent bodies according to claim 1.

[0013] In a preferred embodiment, means are provided for compressing together parts of the three fabrics that are outside the contour of the insert element comprising the first and second insert elements after passing through the grip. Means may be provided to pass the assembly consisting of superimposed first and second elements of the insert, middle third fabric and first and second fabric through a pair of rollers after passing grip between the first and second mat forming wheels. Said rollers are preferably profiled and positioned in the area between the first and second mat forming wheels near the nip between the wheels.

[0014] Alternatively, means are provided for moving one of the first and second fabrics from one of the first and second wheels to form the mat to the remaining wheel, after passing grip between said wheels, and means are provided for moving the assembly consisting of three fabrics and applied on each other the elements of the cartridge moved together on the first or second mat forming wheel for the pressing device.

[0015] The molds on the mat forming wheels may have different sizes, at least in the circumferential direction of the mat forming wheel and the molds on the first wheel may be larger than the molds on the second mat forming wheel.

[0016] The invention also relates to a method of forming air-applied absorbent bodies, comprising the steps of: forming the first and second elements of the insert by air applying the fibrous material entrained in the air stream to the molds on the first and second mat forming wheels, each of said mat forming wheels having at least one mold on its peripheral surface, applying the insert element to the first mat forming wheel and refill element on the other mat forming wheel on each other, characterized by the application of the first and second fabric of the covering material to the peripheral surface of the first and second mat forming wheels, respectively, prior to air application of a mixture of fibrous material entrained in the air stream and separate particles into the mold, passing a third fabric of the covering material covered on at least one side with a covering adhesive by grip between the first and second wheels to form the mat, positioning the mat-forming wheels in such a way that the molded input elements on the respective first and second mat-forming wheels adhere to the third fabric during the grip transition between the first and second mat-forming wheels, so that the air-deposited elements of the insert will be at least partially surrounded by the material jacketing.

[0017] In a preferred embodiment, means are provided for pressing parts of the three fabrics outside of the contour of the cartridge element, including

EP 2 043 576 B1 first and second components of the cartridge. In one alternative, means are provided for passing the assembly consisting of superimposed first and second elements of the insert, middle third fabric and first and second fabric through a pair of rollers after passing grip between the first and second mat forming wheels, thereby providing the elements of the insert they are removed from their respective forms immediately after the grip. Preferably, profiled rollers are provided in the area between the first and second mat forming wheels near the nip between the wheels.

[0018] In another alternative solution, one of the first and second fabrics of one of the first and second mat forming wheels is moved to the remaining wheels after passing the grip between said wheels and a set consisting of three fabrics and superimposed contribution elements moved together on the first or second mat forming wheel is moved to the pressing device.

[0019] The forms of the mat forming wheels may be given various sizes, at least in the circumferential direction of the mat forming wheels and the molds on the first mat forming wheel may be given a larger size than the mold size on the second mat forming wheel. A mixture of fibrous material entrained in the air stream and separate particles can be supplied to the molds of both the first and second mat forming wheels, and nonwoven material is selected for the three fabric wrapping material.

BRIEF DESCRIPTION OF THE DRAWINGS [0020] The invention will now be described with reference to the attached Figures, of which:

Fig. 1 schematically shows a side view of the apparatus for forming air-absorbent absorbent bodies according to a preferred embodiment of the invention, and

Fig. 2 schematically shows a view similar to that of Figure 1, of the second embodiment.

DESCRIPTION OF EMBODIMENTS [0021] In Figure 1, a first embodiment of a device for forming an air-absorbent absorbent body is schematically disclosed. The apparatus comprises two forming drums or mat forming wheels, first wheel 1 and second wheel 2, each containing a series of molds on its peripheral surface. The bottom or grid of the mold can be made of wire mesh or perforated steel sheet. Related to the peripheral surfaces of the two mat forming wheels 1, 2 is the forming chamber or channel 3, 4. Opposite the channel 3 of the first mat forming wheel, a suction box 5 is placed inside the wheel 1 to attract pulp entrained in the air stream or mass mix fibrous and

EP 2 043 576 B1 of the SAP particles to the mold moving between the channel 3 and the box 5. Similarly, the suction box cooperating with the channel 4 of the second mat forming wheel 2 is located inside the wheel 2. The apparatus also includes a mill, e.g. a hammer mill, for fiberising. pulp, ducts used to move fibers or fibers with SAP particles and a blower to move fibers or fibers with SAP particles to the appropriate channel 3, 4. These elements are conventional and well known to those skilled in the art and will not be further described. To understand the present invention, it is sufficient to say that a homogeneous mix of air, fibers and potentially SAP particles is present in the channels when the device is used. As stated above, each channel 3, 4 interacts with a separate suction box 5, 6, respectively, which is stationary and located inside the respective wheel for forming the mat. When the molds on the peripheral surface of each wheel pass between the channel and the associated suction box during the rotation of the wheel, material entrained in the airflow in the channel will be attracted to the mold and deposited therein. Suction boxes 7, 8 are respectively present in the mat forming wheels 1, 2 to hold the insert elements formed in their respective forms and to maintain the shape of the formed insert elements.

[0022] Fabric 9, 10 of the covering material, for example non-woven, is applied to the peripheral surface of each mat forming wheel 1, 2 in front of the respective channel 3, 4, looking in the direction of rotation of the respective mat forming wheel 1, 2, as indicated by arrows A1 , A2. When such a fabric passes over the appropriate suction box 5, 6, the suction forces draw the fabric into the mold and force the fabric to adhere to its bottom.

[0023] The wheels for forming the mats 1, 2 are placed next to each other, the grip between them is at least 6 mm. The term "grip" means the point at which the circumferences of wheels 1, 2 are closest to each other.

[0024] The third fabric 11 of the covering material is passed through the nip between the wheels 1, 2. This fabric, by the appropriate means schematically indicated in Figure 1, is covered with an adhesive coating on one or both sides. The binder is preferably sprayed onto the fabric over its entire surface, so that less than 10% of the fabric surface is covered.

[0025] Of course, it is also possible to apply the adhesive in other ways, for example, the fabric may be pre-coated with a binder which is activated by water, or a binder that is not sticky at room temperature and heat activated.

[0026] In the apparatus of Figure 1, the second element of the insert formed on the second mat forming wheel 2 is moved together with the second fabric 10 onto the first element of the insert formed on the first mat forming wheel 1 and held thereon by the fabric as it will be discussed in detail below until a composite cartridge containing imposed on

The first and second elements of the cartridge are each supplied to the biasing device 12 consisting of two rollers 14, 15 cooperating with the transfer roller 13.

[0027] After pressing, the composite insert passes through the cutting device 16 and is then moved to the accelerator device 17 before it is delivered to the absorbent article production line, of which the device according to the invention is part.

[0028] The method of using the device shown in Figure 1 will now be described.

[0029] When the mat forming wheel 1 rotates in the direction of arrow A1, the molds therein pass sequentially between channel 3 and suction box 5. Channel 3 preferably provides a mixture of pulp fibers and SAP particles that is drawn into the molds at the first mat forming wheel and put away in them. The first element of the contribution is created in these forms. During rotation of the mat forming wheel 2 in the direction of A2, the molds contained therein pass successively between the duct 4 and the suction box 6. During this transition, a mixture of pulp fibers and SAP particles is applied air to the molds on the second wheel 2. Layer of pulp and SAP particles have a thickness of 5 mm. The concentration of SAP particles in this layer is higher, about 50-70% by mass, than the concentration in the first elements of the air applied in the first wheel 1 to form the mat, in which it is about 10-30% by mass. Non-woven layers 9, 10 closest to the bottom of the mold in the first and second wheels perform the function of preventing blocking and clogging of holes in the bottom of the mold, which causes uneven distribution of air leading to uneven distribution of the air-applied material and protection against damage to this bottom. It has been surprisingly found that SAP particles in a mixture of pulp and SAP particles can cause wear of the mold bottom material. These fabrics also perform the function of preventing the SAP particles from falling out of the insert element formed in a suitable form after the first and second insert elements are extracted from their molds as the composite insert is moved from the wheel 1 to the pressing device 12.

[0030] The molds in the wheels 1, 2 are shallower than the insert elements molded in them. After forming the elements of the insert by air application in the appropriate forms, the elements of the insert are held in their respective forms by the respective suction boxes 7, 8 until they reach the nip between the wheels for forming the mat 1, 2.

[0031] The nip preferably has dimensions such that the outer parts of the insert elements, i.e. their sides distant from the respective mold bottoms, adhere to each other in the nip. In other words, the grip is the connection point between the two elements of the insert where they connect. The grip preferably has dimensions such that normally overlapping parts of the cartridge elements are slightly compressed at the connection point. Suction boxes 7, 8 in the respective wheels 1, 2 for forming the mats end at the connection point. In the nip, the fabric 10 leaves the mat forming wheel 2 and is applied to the peripheral surface of the mat forming wheel 1 on top of the elements

EP 2 043 576 B1 moving on this surface. When the fabric leaves the molds in the mat forming wheel 2, it also pulls the insert molded in the mold with each other and thus supports this insert element when moving from the mat forming wheel 2 to the mat forming wheel 1. Due to the setting of the grip and the excessive filling of the forms, all the overlapping points on one of the wheels 1, 2 in the shank will come into contact with the outer part of the insert element on the remaining wheel, when it is still maintained in its form and only then is the imposition on a refill element from the remaining circle. In this way, controlled and accurate overlap of the elements of the cartridge is obtained.

[0032] Due to this high content of SAP particles, there is a risk that the strength of the insert elements molded in the molds in the second mat forming wheel 2 is not sufficient to ensure their integrity during further movement and handling. However, in the device described with reference to Figure 1, the elements of the insert on the second mat forming wheel are reinforced by their adhesive attachment to the third fabric 11 in the nip between the wheels 1, 2. As is evident from Figure 1, this fabric passes between the elements of the insert on the respective wheel and thus will be adhesively attached to both of these elements of the insert when pressed together. The composite insert exiting the grip thus comprises two superimposed elements of the insert, both of which are fully enclosed between two layers of wrapper material, namely three fabrics 9, 10, 11, where the middle third layer 11 is common to both elements of the insert. Thus, both components of the cartridge forming the cartridge are reinforced.

[0033] After the insert element from the second mat forming wheel 2 is transferred to the wheel 1, onto the insert element on the first wheel 1 together with the fabrics 10, 11, these fabrics 10, 11 will also prevent SAP particles from falling out of this insert element during transport.

[0034] The composite insert consisting of two superimposed elements of the insert, two outer fabrics 9, 10 and central fabric 11 are transferred to the peripheral surface of wheel 1 and then transferred to a transfer roller 13 acting as an anvil for two pressure rollers 14, 15 providing two-stage compression of said composite insert. The compressed insert then passes through a rotary cutting device 16 in which individual inserts are cut from a composite assembly consisting of a row of composite inserts held together by three fabrics 9, 10, 11 and the individual inserts are transported to the accelerator 17, which delivers individual inserts to others ingredients in the line for the production of disposable sanitary absorbent articles, for example, providing fabric inserts of liquid permeable material, constituting one of the outer covering layers of such an article.

[0035] As stated above, each of the superimposed insert elements leaving the nip between the mat forming wheels 1, 2 is wrapped by two non-woven fabrics

EP 2 043 576 B1 of the material, respectively fabrics 9, 10 and 10, 11. This means that the elements of the cartridge on one of the wheels 1, 2 do not require support of their front part by the part of the cartridge element on the remaining wheel, it is sufficient that the front part is supported between said two fabrics, which in turn are guided during the transfer of the cartridge element from one wheel to the peripheral surface of the other wheel.

[0036] It is therefore possible for the device described above to produce a cartridge consisting of two cartridge elements precisely superimposed. Of course, it is also possible to produce an insert in which the superimposed elements of the insert do not overlap. Such a device enables the production of cartridges of various sizes by changing the overlapping of the cartridge components.

[0037] Such a device must of course include means for controlling the resulting overlap between the elements of the cartridge, i.e. means for changing the synchronization of the mat-forming wheels to control the time at which the front edge of the mold on one of the mat-forming wheels passes through the grip over time. when the front edge of the mold on the remaining mat forming wheel passes through the grip. An easy way to control the overlap is to change the start of rotation of the mat forming wheels, so that one of the mat forming wheels begins to rotate before the other. Another way is of course to manually determine the angular displacement of one wheel relative to the other.

[0038] The device according to an embodiment shown enables the production of absorbent bodies at very high speeds, exceeding even 600 bodies per minute.

[0039] In Figure 2, a second embodiment of the device is schematically illustrated. This embodiment differs from that described with reference to Figure 1 mainly in that the superimposed elements of the cartridge are extracted from their respective molds immediately after they pass through the nip between the two wheels for forming the mat. The device elements in the second embodiment similar to the device elements in Figure 1 have the same reference numerals with the addition of the prim sign.

[0040] As evident from Figure 2, a pair of rollers 18 is present between the wheels 1 ', 2' for forming the mat directly under the nip between the two wheels. The fabrics 9 ', 10', 11 'and the row of superimposed insert elements held between the fabrics 9', 10 'and attached to the central fabric 11' pass through this pair of rollers 18. A pair of rollers 18 acts to securely secure parts of the fabrics 9 ', 10', 11 'protruding beyond the outline of the superimposed elements of the cartridge to each other by pressing the fabrics 9', 10 'to the adhesive covering on opposite sides of the fabric 11'. The rollers can be profiled to avoid squeezing the insert element before the wrap provided by the fabrics is sealed by mutual adhesion of the fabrics. In this way, a row of successive composite cartridges is created, completely and tightly wrapped, the row being

The composite inserts are held together by a central fabric material. Thanks to this arrangement, the composite inserts can be mixed as needed without the risk of damaging the elements of the insert or the risk of falling out of SAP particles. The device according to the second embodiment can therefore be located anywhere in the production line of sanitary absorbent articles and allows optimal use of space in such a line.

[0041] The method of forming composite cartridges with the high particle content SAP cartridges according to the present invention and the device used offer many advantages over known methods and devices. Due to the fact that the grip between the two mat forming wheels leave the composite inserts completely covered, the risk of loss of SAP particles is reduced. The fabrics used for wrapping and transporting the formed composite inlays are also used to extract the inlays from the appropriate molds, eliminating the need for blowing devices commonly used for this purpose, and the fabrics applied to the bottom of the molds also protect the molds from clogging and damage. The middle fabric strengthens the elements of the inserts and reduces the risk of leakage of the binder during pressing because the binder is not applied directly to one of the outer fabrics, but to the middle fabric. Such leaks adversely affect the functioning of the pressing device. As is evident from the second embodiment, a pair of mat forming wheels can be located anywhere relative to other elements in the sanitary absorbent article production line.

[0042] The devices according to the described embodiments can of course be modified in several respects without departing from the scope of the invention. The dimensions of the elements of the cartridges may be different from those described. A different type of wrap material may be used than non-woven and the insert elements on the first mat forming wheel need not contain SAP particles. More than one air application device may be associated with each mat forming wheel. Different fibers may be used in different air application devices, and the cutting device and accelerator for supplying manufactured cartridges to the production line for the production of absorbent articles may be any type of such devices used in such production lines. The invention should therefore only be limited by the statements of the appended claims.

EP 2 043 576 B1