There is today a variety of absorbent articles, such as sanitary napkins, panty liners, diapers, bed protections and incontinence guards, having different shapes and dimensions on the market. Such an absorbent article usually comprises an absorbent structure formed to absorb body fluids under a short period of time and to distribute and store body fluids. This means that the absorbent structure usually comprises several different layers having different characteristics in relation to each other. The absorbent structure often comprises at least a liquid acquisition layer, a liquid storage layer and a liquid distribution layer.
As a liquid acquisition layer is usually used a porous material having a high momentaneous liquid receiving capacity. Examples of such materials are cellulosic fluff pulp of thermomechanic or chemothermomechanic (CTMP) type, chemically stiffened cellulosic fibres, synthetic fiber structures of different types and porous foam materials etc.
As a storage layer is usually cellulosic fluff pulp mixed with so called superabsorbents used, or superabsorbent polymer particles (SAP), i.e. crosslinked polymers having the ability to absorb several times their own weight (10 times or more).
As distribution layer may cellulosic fluff pulp, tissue layer, foam, synthetic fibers and the like having high liquid distribution capacity be used. It is also possible to combine two or more of the functions acquisition, storage and distribution in one and the same layer.
Since superabsorbent particles are more expensive than natural or synthetic fibermaterials, it is advantageous to reduce the amount of superabsorbent particles in the absorbent structure. Rather than reduce the amount of such particles throughout the entire structure, it is desirable to distribute the particles in the structure in a pre-determined manner such that the particles are where it is most efficient to receive and store body fluids.
In order to be able to apply the superabsorbent particles on pre-determined areas of the absorbent structure, commonly airborne superabsorbent particles are directed through a valve, where the supplying of particles to the absorbent structure is controlled by means of a valve vane. Such an apparatus for applying particles on an absorbent structure is shown in FIG. 1. When a valve vane arranged in the valve is in a first position, the airborne particles are directed through the valve to a nozzle supplying the particles to the absorbent structure. When the valve vane is in a second position, the airborne particles are directed through the valve to a collecting container for recycling of the particles. This kind of valve is shown in more detail with the valve vane in the first position in FIG. 2a and in the second position in FIG. 2b.
Such a valve is previously known through U.S. Pat. No. 5,279,854, which displays an apparatus for applying superabsorbent particles on pre-determined areas of a fibrous material. Air-entrained absorbent particles are directed through a valve which alternately is directing the particles to a first and a second nozzle supplying the particles to the absorbent structure, which allows the particles to de deposited on the absorbent structure on pre-determined areas.
However, it has turned out that when a valve of the kind described above is in its second position, the particles that are in the outlet conduit when the valve is switched to the second position will be dispensed on the fibrous material forming a “tail” to the pre-determined area, a so called tailing effect. It is desirable to get rid of this “tail” and obtain a distinct ending of the particle provided areas of the absorbent structure, in order to reduce the consumption of particles and at the same time make an aesthetically attractive effect. Further, particles in the “tail” may even end up outside the absorbent structure, e.g. directly between a surface material and a back layer. Since superabsorbent particles often form sharp granules, it may in this case cause discomfort at use of the article, which is yet another reason for desiring to avoid the forming of a tail of particles.