Technical field

This invention relates to a device for forming an absorbent pad.

Background art

The absorbent pad, also known in the trade as "core", is intended for use in making absorbent sanitary articles such as, for example, nappies for children and adults, to which express reference is hereinafter made without losing in generality, sanitary towels and the like.

Normally, the absorbent pad comprises an absorbent core made of an absorbent material, such as, for example, beads of superabsorbent polymer material (SAP) inside a mixture of containment cellulose pulp (fluff) and absorbent material binder, sandwiched between two layers of non-woven fabric.

It is known that the absorbent core of the pad is made using a forming drum which is rotatable about an axis of rotation and whose peripheral surface confronts a feed hood for feeding the absorbent material. Aim of the invention

The peripheral surface of the drum is provided with one or more pockets for receiving and retaining the absorbent material used to form the absorbent core.

Each retaining pocket has a bottom surface on which the absorbent material settles and side walls for containing the absorbent material fed by the hood. The distance between the peripheral surface of the drum and the surface of the bottom of the pocket defines the thickness of the absorbent core of the pad in a radial direction of extension of the drum.

Recently, there has been an increasing need to improve the absorbent power of the pad and, in this context, a device has been developed for forming an absorbent pad for an absorbent sanitary article which comprises at least an absorbent core of absorbent material.

The device comprises a forming drum rotatable about an axis of rotation and having a peripheral surface provided with at least one forming pocket for forming the absorbent core.

The drum has a suction chamber configured to allow the absorbent material to be retained in the pocket.

The pocket has a bottom surface and a lateral surface for containing the absorbent material, both defining a base layer of the absorbent core.

The distance between the peripheral surface of the drum and the bottom surface of the pocket defines the minimum depth of the pocket.

Each pocket of the drum is provided with a plurality of grooves for accumulating the absorbent material, each of which extends from the bottom surface of the pocket towards the axis of rotation of the drum and has a respective opening made at the bottom surface of the pocket to allow the absorbent material to pass through.

Each groove has a respective bottom surface for depositing the absorbent material and whose distance from the bottom surface of the pocket defines the depth of the groove.

The maximum depth of the pocket is equal to the sum of the minimum depth of the pocket plus the depth of the groove.

Each groove defines a respective zone for accumulating the absorbent core extending from the base layer of the absorbent core itself.

Advantageously, the presence of grooves used to accumulate the absorbent material on top of the customary forming pocket allows creating respective zones capable of holding more absorbent material in order to facilitate absorption of the liquids.

Brief description of the drawings

Further characteristics and advantages of this solution are more apparent in the non-limiting description below, with reference to a preferred but non- exclusive embodiment of an apparatus for forming a pad, as illustrated in the accompanying drawings, in which:

Figure 1 is a schematic front view of an apparatus for forming an absorbent pad according to this invention;

Figure 2 is a schematic perspective view, with some parts cut away in order to better illustrate others, of a detail from Figure 1 , according to a first variant embodiment;

Figure 3 is a schematic perspective view, with some parts cut away in order to better illustrate others, of a detail from Figure 1 , according to a second variant embodiment;

Figure 4 is a schematic perspective view, with some parts cut away in order to better illustrate others, of a detail from Figure 1 , according to a third variant embodiment;

Figure 5 shows a schematic cross section of the detail of Figure 2;

Figure 6 shows a schematic cross section of the detail of Figure 4;

Figure 7 is a schematic top view showing an absorbent pad made by the apparatus of Figure 1 corresponding to the variant of Figure 2;

Figure 8 shows a schematic cross section of the middle part of the pad of Figure 7;

Figure 9 is a schematic top view showing an absorbent pad made by the apparatus of Figure 1 corresponding to the variant of Figure 4;

Figure 10 shows a schematic cross section of the middle part of the pad of Figure 9;

Figure 1 1 shows an absorbent pad made by the apparatus of Figure 1 according to a further variant embodiment.

Detailed description of preferred embodiments of the invention

With reference to Figure 1 , the numeral 1 denotes a device for forming an absorbent pad 100 for an absorbent sanitary article.

The pad 100 comprises an absorbent core 103 interposed between a first layer 101 and a second layer 102. The first and second layers 101 , 102 may be made of permeable, non- woven fabric.

Alternatively, one between the first and the second layer 101 , 102 may be made of impermeable material.

The device 1 comprises a feed hood 2 for feeding absorbent material 3 used to form the absorbent core 103 of the pad 100.

The device 1 comprises a forming drum 4 for forming the absorbent core 103 and which is rotatable about an axis of rotation 4a and has a peripheral surface 5 that at least partly confronts the hood 2.

The peripheral surface 5 is provided with at least one forming pocket 6 for forming the absorbent core 103 and which has a bottom surface 7, on which the absorbent material 3 fed by the hood 2 settles, and a lateral surface 8) for containing the absorbent material 3.

The lateral surface 8 of the pocket 3 comprises a first and a second longitudinal edge 8a, 8b and a first and a second transverse edge 8c, 8d, with reference to the extension of the pocket 6 on the peripheral surface of the drum 5.

The lateral surface 8 of the pocket 6 defines the perimeter edge of the absorbent core 103.

The perimeter shape of the absorbent core 103 is a function of the perimeter shape of the pocket 6, or of the shape of the lateral surface 8.

The bottom surface 7 and the lateral surface 8 of the pocket 6 define a base layer 104 of the absorbent core 103.

The distance between the peripheral surface 5 of the drum 4 and the bottom surface 7 of the pocket 6 defines the minimum depth“p1” of the pocket 6. The minimum depth“p1” defines a minimum thickness "s1 " of the absorbent core 103, determined at least at the base layer 104.

Preferably, the drum 4 has a plurality of separate pockets 6 disposed along the peripheral surface 5 of the drum 4.

Alternatively, the pockets 6 extend uninterruptedly along the peripheral surface 5 of the drum 4. According to this invention, the pocket 6 of the drum 4 is provided with a plurality of grooves 10 for accumulating the absorbent material 3.

Each groove 10 extends from the bottom surface 7 of the pocket 6 towards the axis of rotation 4a of the drum 4.

In other words, the grooves 10 are disposed under the respective pocket 6, with reference to a direction of radial extension of the drum 4.

Each groove 10 defines a respective zone 105 for accumulating the absorbent material 3 of the absorbent pad 100.

Each zone 105 for accumulating the absorbent material 3 is disposed above the base layer 104 of the pad (see Figures 8 and 10). Each groove 10 is in communication with the bottom surface 7 of the respective pocket 6 through a respective opening 1 1 made at the bottom surface 7 of the pocket 6 to allow the absorbent material 3 to pass through.

In short, the bottom surface 7 of the pocket 6 is alternated with the openings 1 1 for the passage of the absorbent material 3.

Looking at the arrangement of the grooves 10 in the pocket 6, it is noted that the pocket 6 is provided with at least a first end groove 14 and a second end groove 15 at the ends of the peripheral surface 5 of the drum with reference to the transverse extension thereof (see Figures 5 and 6).

The opening 14a giving access to the first end groove 14 is formed in the bottom surface 7 of the pocket 6 at a respective distance from the first longitudinal edge 8a.

The opening 15a giving access to the second end groove 15 is disposed on the bottom surface 7 of the pocket 6 at a respective distance from the second longitudinal edge 8b.

The distance between the access opening 14a, 15a of the first and the second end groove 14 and 15 and the respective first and second longitudinal edge 8a, 8b determines the distance of the respective zones 105 for accumulating the absorbent material 3 on the base layer 104 from the perimeter edge of the base layer 104 itself.

In other words, the first end groove 14 and the second end groove 15 of the pocket 6 define a respective first and second accumulation zone 1 14, 1 15 of the absorbent core 103.

The distance between the access opening 14a, 15a of the first and the second end groove 14 and 15 and the respective first and second longitudinal edge 8a, 8b determines the distance 1 14a, 1 15a of the respective first and second accumulation zone 1 14, 1 15 from the perimeter edge of the base layer 104 of the absorbent core 103.

Advantageously, the resulting absorbent core 103, where the first and the second end grooves 14 and 15 thus spaced from the respective longitudinal edge 8a, 8b, has a minimum thickness in proximity to the perimeter edge, thus facilitating joining the first and the second layer 101 , 102 to each other (see Figures 8 and 10).

With reference to the mutual positioning of the grooves 10, the access openings 1 1 are formed in the bottom surfaces 7 of the pockets 6 at a defined distance from each other starting from the first or the second end groove 14, 15.

The mutual positioning of the grooves 10 defines the mutual positioning of the zones 105 for accumulating the absorbent material 3 of the absorbent core 103.

Each groove 10 has a bottom surface 21 on which the absorbent material 3 settles.

At each groove 10, the distance between the bottom surface 7 of the pocket 6 and the bottom surface 21 of the groove 10 defines the depth "p2" of the groove 10.

At each groove 10, the distance between the peripheral surface 5 of the drum 4 and the bottom surface 21 of the groove 10 defines a maximum depth "p3" of the pocket 6.

The maximum depth "p3" of the pocket 6 is equal to the sum of the minimum depth "p1 " plus the depth "p2" of the groove 10.

The maximum depth "p3" is greater than the minimum depth "p1 ".

The maximum depth "p3" defines a maximum thickness "s3" of the absorbent core 103, greater than the minimum thickness "s1 ".

The maximum depth "p3" defines a maximum thickness "s3" of the absorbent core 103 determined at an accumulation zone 105 of the absorbent core 103.

The height of an accumulation zone 105 of the absorbent core 103, the thickness "s2", is determined by the maximum depth of a respective groove 10 - that is, the depth "p2".

It should be noted that these thicknesses“s1”,“s2” and“s3” of the absorbent core are determined along the vertical of the absorbent core 103.

The drum 4 has a suction chamber 9 configured to allow retaining at least in the pocket 6 the absorbent material 3 that passes through the hood 2 during rotation of the drum 4 about the axis 4a.

In order to retain the absorbent material 3 in the pocket 6, the bottom surface 7 of the pocket 6 is permeable to air along its entire extension.

Each groove 10 has a peripheral surface 13 on the outside of the pocket 6 and in fluid communication with the suction chamber 9 of the drum 4.

The outside peripheral surface 13 of each groove 10 is permeable to air along its entire extension.

Advantageously, since the entire outside peripheral surface 13 of each groove 10 is in fluid communication with the suction chamber, the absorbent material 3 attracted though the access opening 1 1 completely fills the space in the groove 10 without leaving any gaps or interstices.

The shape of the accumulation zone 105 is defined by the shape of the peripheral surface 13 of the groove 10.

It should be noted that in the embodiments illustrated, the peripheral surface 13 of the groove 10 has a concave shape that determines a convex shape of the respective accumulation zone 105.

As illustrated in Figures 2 and 4, each groove 10 has a peripheral surface 13 which is curved or arcuate in shape.

As illustrated in Figure 3, each groove 10 has a peripheral surface 13 which is straight, and, specifically, has a rectangular profile. The main longitudinal extension of each groove 10 may be straight or, alternatively, curved or arcuate.

In the variant of Figure 1 1 , the longitudinal extension of each accumulation zone 105 has a zig-zag shape so as to increase the volume of absorbent material 3 in the pad 100 for the same longitudinal extension.

To obtain this shape, the main longitudinal extension of the groove 10 of the pocket 6 is evidently zig-zagged.

With reference to the variant embodiment of Figure 4 and Figure 6, the pocket 6 of the drum 4 comprises one or more inserts 12 which inhibit the action of the suction chamber 9 and prevent absorbent material 3 from being deposited at each insert 12, thus creating a corresponding zone 106 that is free of absorbent material 3 inside the absorbent core 103.

As may be inferred from the corresponding pad 100 of Figure 10, at each zone 106 free of absorbent material 3, the first layer 101 is joined to the second layer 102.

Each insert 12 is disposed between two respective access openings 1 1 of two adjacent grooves 10.

In the preferred embodiment, the pocket 6 comprises two inserts 12 for defining two respective zones 106 free of absorbent material 3 in the absorbent core 103.

As may be inferred from this description, the shape of the absorbent core 103 of the pad 100 is defined by the shape of the pocket 6 and of the respective grooves 10 and by the presence or absence of inserts 12.

In order to make the pad 100, the device 1 comprises a first feed system 17 for feeding to the forming drum 4 a first web NW1 , intended to form the first layer 101 of the pad 100.

The suction chamber 9 causes the absorbent material 3 to be spread on the first web NW1 disposed on the forming drum 4 inside the pocket 6.

The first web NW1 settles in the pocket 6, in contact with the bottom surface 7 of the pocket 6 and the bottom surfaces 21 of the grooves 10.

It should be noted in this regard that the maximum thickness "s3" of the absorbent core 103, determined by the maximum depth "p3" of the pocket 6, includes the absorbent core 103 and the layer 102.

The device 1 comprises a second feed system 18 for feeding to the forming drum 4 a second web NW2, intended to form the second layer 102 of the pad 100.

The second web NW2 is fed to the forming drum 4 downstream of the feed hood 2.

The first web NW1 , the second web NW2 and the absorbent material 3 interposed between the webs NW1 and NW2 to form a succession of absorbent cores 103 define a composite web NW.

The device comprises a joining system 19 for joining the composite web NW and a cutting system 20 for cutting the composite web NW into individual pieces, each defining an absorbent pad 100.

The joining system 19 is configured to join the composite web NW at the first and second webs NW1 , NW2 to define the longitudinal edges and the transverse edges of the pad 100.

If the pad 100 is provided with the zones 106 free of absorbent material 3 in the absorbent core 103, the joining system 19 is configured to join the composite web NW at the first and second webs NW1 , NW2 and in the zones 106 free of absorbent material 3, thus defining respective channels in the pad 100.

The joining system 19 may comprise welding means - for example, ultrasound welding means - or pressing means if an adhesive substance is interposed between the two webs NW1 , NW2 to join them to each other.