WO2014170795A1

WO2014170795A1 - Unit for making absorbent pads for nappies

Info

Publication number: WO2014170795A1
Application number: PCT/IB2014/060522
Authority: WO
Inventors: Matteo Piantoni; Valerio Soli
Original assignee: Gdm S.P.A.
Priority date: 2013-04-17
Filing date: 2014-04-08
Publication date: 2014-10-23
Also published as: ITBO20130172A1

Abstract

A unit for making absorbent pads for nappies comprises a drum (4) for forming an absorbent pad (2) and having on its peripheral surface (4a) a plurality of suction recesses (5); a hood (6) for feeding a first absorbent material (7) and which is mounted to face a part of predetermined width of the peripheral surface (4a) of the drum (4) and a duct (15) for feeding a charge of superabsorbent material (9) and equipped with a delivery mouth (17) facing the peripheral surface (4a) of the drum (4); the feeding duct (15) comprises valve means (19) equipped with a distributor (25) for feeding the superabsorbent material (9) and which oscillates about its axis of rotation (25a).

Description

DESCRIPTION

UNIT FOR MAKING ABSORBENT PADS FOR NAPPIES

Technical field

This invention relates to a unit for making absorbent pads for nappies. Background art

Typically, nappies comprise an impermeable layer, for example of polyethylene, a layer of non-woven fabric permeable to liquids and an absorbent pad sandwiched therebetween.

Nappies also comprise a liquid acquisition layer interposed between the absorbent pad and the permeable layer of non-woven fabric in order to promote liquid distribution in the absorbent pad.

Absorbent pads are made mainly from natural fibre particles (known as "fluff") uniformly blended with particles of superabsorbent polymer material ("SAP").

In recent years, higher pad absorption capacity has been achieved by absorbent pads comprising one or more discrete absorbent layers made mainly from particles of superabsorbent polymer material ("SAP").

It is known from the prior art that a unit for making absorbent pads for nappies comprises a drum, which rotates about its axis of rotation and which has on its peripheral cylindrical surface a plurality of suction housings or recesses within which respective absorbent pads are formed. The unit also comprises a hood for feeding the particles of fluff mixed with the particles of "SAP" and which is mounted along a stretch of predetermined width above the peripheral cylindrical surface of the drum and the corresponding suction recesses.

The fluff fibre particles and the "SAP" particles of superabsorbent polymer material are pneumatically fed into the hood, where they are mixed together and then fed to the drum where they settle in the suction recesses located under and facing the hood as the drum rotates.

Once a suction recess on the drum has been filled with the mixture of fluff and "SAP" fed by the hood, a respective finished absorbent pad is obtained.

During the formation of the absorbent pads in the respective suction recesses, the feeding duct intermittently feeds the charges of "SAP" to define the above mentioned discrete absorbent layers.

Intermittent valve means are located upstream of the delivery mouth of the feeding duct in order to regulate the intermittent "SAP" feed flow as a function of the spacing of the drum recesses, so that discrete charges of "SAP" are delivered exactly at the moment a suction recess of the drum comes to face the delivery mouth of the duct itself.

In one prior art solution, described in document EP2405877 in the name of the same Applicant as this invention, the valve means comprise a rotating disc having one or more arcuate slots made therein and rotating about its axis of rotation. The "SAP" is fed intermittently by these valve means because, as the disc rotates, the arcuate slots made therein are in communication with the feeding duct only for a predetermined angular interval during which the "SAP" is allowed to pass through the valve means themselves.

The valve means just described have several disadvantages, however. In particular, it has been found that these valve means do not guarantee a uniform distribution of superabsorbent material ("SAP").

Indeed, since the "SAP" is made up of particles of different sizes, the finer particles pass through into the feeding duct more easily than the larger "SAP" particles, thus forming discrete absorbent layers which are not uniform with each other, since they are made up of "SAP" particles of uncontrollably different sizes.

This negatively affects the quality of the absorbent pads because the absorbing power of each pad depends also on the composition of the discrete absorbent layers and, in particular, on the sizes of the "SAP" particles making up these layers.

It has also been found that the "SAP" particles are damaged when they impact the rotating disc of the valve means, thus reducing their joint effectiveness in the absorption and drainage of liquids.

From the above it may be inferred that the valve means described do not allow the production of absorbent pads which are uniform with each other and which have controlled, repeatable quality.

Aim of the invention

The aim of this invention is to provide a unit, as set out in the accompanying claims, for making absorbent pads for nappies, comprising valve means for feeding and metering superabsorbent polymer material ("SAP") and capable of delivering charges of "SAP" which are as uniform as possible with each other, especially in terms of particle size.

Brief description of the drawings

The invention will now be described with reference to the accompanying drawings which illustrate a non-limiting embodiment of it and in which:

- Figure 1 is a schematic front view illustrating a unit for making absorbent pads for nappies according to this invention;

- Figure 2 is a schematic perspective view of valve means forming part of the unit illustrated in Figure 1 ;

- Figure 3 is a scaled-up view of the valve means of Figure 2;

- Figure 4 shows a schematic front view of the valve means of Figure 3 with some parts cut away in order to better illustrate others

- Figure 5 shows a schematic front view of an alternative embodiment of the valve means, with some parts cut away in order to better illustrate others;

- Figure 6 is a scaled-up perspective view of a detail of the valve means of Figure 4;

- Figures 7, 8 and 9 are schematic front views of the valve means in different operating configurations;

- Figure 10 is a schematic perspective view of the valve means in the operating configuration illustrated in Figure 9.

Detailed description of preferred embodiments of the invention

With reference to Figure 1 , the numeral 1 denotes in its entirety a unit for making absorbent pads 2 for nappies.

Generally speaking, a nappy comprises a sheet of permeable material and a sheet of impermeable material having, sandwiched between them, an absorbent pad constituting the part of the nappy whose function is to absorb liquids.

For this purpose, the absorbent pad 2 is made mostly of natural fibre material (fluff) 8 uniformly blended with superabsorbent material ("SAP") 9.

Preferably, the superabsorbent material used is superabsorbent polymer material in granular form.

Also, to increase its absorbing capacity, the pad 2 comprises a discrete absorbent layer made mainly from superabsorbent material ("SAP") 9. The unit 1 comprises a feed line 3 along which the finished absorbent pads 2 are fed.

The unit 1 comprises a forming drum 4 by which the absorbent pads 2 are formed.

The drum 4 is substantially tangent to the feed line 3 at a release station 36.

The drum 4 has a horizontal axis of rotation R perpendicular to the feed line 3.

More specifically, in the embodiment illustrated in Figure 1 , the drum 4 rotates about its axis R in a clockwise direction.

On its peripheral surface 4a, the drum 4 has a plurality of suction recesses 5.

The suction recesses 5 are located on the peripheral surface 4a of the drum 4 at a predetermined spacing P.

As the drum 4 rotates, absorbent pads 2 are gradually formed inside respective suction recesses 5 and, once completed, are released onto the feed line 3 by the drum 4 itself at the release station 36.

The unit 1 comprises a hood 6 for feeding an absorbent material 7 and peripherally facing the drum 4 for at least part of the peripheral surface 4a of the drum 4.

In other words, the drum 4 is interposed between the feed line 3 and the feeding hood 6.

The above mentioned absorbent material 7 comprises natural fibre material (fluff) 8 uniformly blended with superabsorbent material ("SAP") 9.

In an alternative embodiment, the absorbent material 7 comprises only natural fibre material (fluff) 8.

In the preferred embodiment, the hood 6 is located above the drum 4. More specifically, the hood 6 defines a zone 10 for mixing and transporting the natural fibre material (fluff) and the superabsorbent material "SAP".

The mixing and transporting zone 10 has a feeding outlet 1 1 located to face the peripheral surface 4a of the drum 4.

The hood 6 has an inlet opening 13 located at one of its ends, on the side opposite the feeding outlet 1 1 .

The cross-sectional structure of the zone 10 is divergent in shape from the inlet opening 13 to the feeding outlet 1 1 . The hood 6 comprises a blower 12 for supplying the fluff fibre material 8 under pressure.

The blower 12 is located at the inlet opening 13 and is in fluid communication therewith.

The unit 1 comprises a first system 14 for metering and feeding "SAP" 9. The first system 14 feeds predetermined quantities of superabsorbent material 9 into the hood 6, in particular into the mixing and transporting zone 10.

The charges of "SAP" 9 fed by the first system 14 into the hood 6 are proportional to the quantity of natural fibre material (fluff) 8 which it is mixed with inside the hood 6.

Since both the fluff and the "SAP" are fed in the proximity of the inlet opening 13, their mixing, and the consequent formation of the absorbent material 7, occurs while they are being conveyed towards the feeding outlet 1 1 .

The feeding outlet 1 1 delivers the absorbent material 7, which settles in the suction recesses 5 of the drum 4 filling them gradually for as long as they are positioned to face the hood 6 following rotation of the drum 4. With reference to the direction of rotation of the drum 4, once the peripheral surface 4a of the drum 4 facing the hood 6 moves out of the zone of action of the feeding outlet 1 1 of the hood 6, the suction recesses 5 house respective finished absorbent pads 2 which are released by the drum 4 to the feed line 3 at the release station 36.

In order to make in the absorbent pad 2 the above mentioned discrete absorbent layers, consisting of superabsorbent material "SAP", the unit 1 comprises a duct 15 for feeding discrete charges of "SAP".

The duct 15 leads to the hood 6.

By "leads to" is meant that the duct 15 preferably terminates at at least one of the walls of the hood 6 without extending further into the hood 6 itself. In an embodiment, not illustrated, the duct 15 extends at least partly into the hood 6.

The outlet 1 1 thus feeds into the suction recesses 5 the absorbent material 7 and the superabsorbent material "SAP" 9 coming out of the feeding duct 15.

More precisely, the duct 15 has a delivery mouth 17 leading to the hood 6. The unit 1 comprises a second system 18 for metering and feeding superabsorbent material ("SAP") 9.

The second system 18 comprises the duct 15 for feeding superabsorbent material 9 used to make the discrete absorbent layers in the pads 2.

It should be noted that in the embodiment described, the superabsorbent material 9 metered and fed by the first and second systems 14 and 18 is the same.

Alternatively, the superabsorbent material 9 metered and fed by the first system 14 is different from that metered and fed by the second system 18. The feeding duct 15 comprises valve means 19.

The valve means 19 are located upstream of the delivery mouth 17 along a stretch T of the feeding duct 15.

More specifically, the valve means 19 define a first stretch T1 of the duct 15 upstream of the valve means 19 and a second stretch T2 of the duct 15 downstream of them.

As illustrated in Figures 3 and 4, the valve means 19 comprise a main body 20 having at least one first inlet mouth 21 and at least one first outlet mouth 22.

The first inlet mouth 21 and the first outlet mouth 22 are in fluid communication with the feeding duct 15.

More precisely, the first stretch T1 of the feeding duct 15 is connected to the first inlet mouth 21 and the second stretch T2 of the feeding duct 15 is connected to the first outlet mouth 22.

The main body 20 is substantially a box-shaped body and the first outlet mouth 22 is located on the opposite side relative to the first inlet mouth 21 .

The main body 20 has a second outlet mouth 23.

The unit 1 comprises a system 24 for recycling the superabsorbent material "SAP" coming out of the valve means 19.

More specifically, a recycling duct 34 connects the recycling system 24 to the second outlet mouth 23 of the valve means 19.

In this embodiment, the recycling system 24 is connected to the first system 14 for metering and feeding "SAP" 9.

Alternatively, in an embodiment not illustrated, the recycling system 24 is connected to the second system 18 for metering and feeding "SAP" 9.

Thus, the recycling system 24 conveys the "SAP" coming out of the valve means 19 through the second outlet mouth 23 to the first system 14 which feeds the mixing and transporting zone 10 of the hood 6.

The charges of "SAP" granules are delivered through the first outlet mouth

22, and consequently through the delivery mouth 17 of the feeding duct

15, intermittently because the "SAP" granules settle in a suction recess 5 of the drum 4 each time the recess comes to face the delivery mouth 17.

According to the invention, the valve means 19 comprise a distributor 25 which oscillates, in particular about its axis of rotation 25a, to be positioned alternately at a first feed position at the first outlet mouth 22 and a second shutoff position of the first outlet mouth 22 where feed is interrupted.

The main body 20 is hollow and has inside it a chamber 20a which houses the distributor 25.

The axis of rotation 25a of the distributor 25 is oriented along a direction parallel to the axis of rotation 4a of the drum 4.

More precisely, the axis of rotation 25a of the distributor 25 is oriented along a substantially horizontal direction.

More specifically, the distributor 25 oscillating about its axis 25a as a function of the spacing P of the suction recesses 5 of the drum 4 in order to intermittently feed the granules of superabsorbent material 9 through the first outlet mouth 22.

Since feeding of the second system 18 is continuous, as soon as delivery through the first outlet mouth 22 is interrupted, the flow of "SAP" 9 is diverted into the second outlet mouth 23, as illustrated in Figures 9 and 10.

As may be observed in Figures 8 to 10, the distributor 25, by oscillating about its axis 25a, selectively feeds the first outlet mouth 22, Figure 7, and the second outlet mouth 23, Figure 9, passing through the centre line of the two mouths 22 and 23, Figure 8.

The oscillating motion of the distributor 25 is accomplished by means of actuator means 37 in phase with the rotation of the drum 4.

The actuator means 37 comprise a motor 38 for driving the distributor 25 and a mechanical oscillator 39 interposed between the drive motor 38 and the distributor 25 and connected to both.

The mechanical oscillator 39 is driven by the motor 38 and converts the continuous rotating motion of the motor 38 into continuous oscillating motion.

Preferably, a transmission element 40 is interposed between the drive motor 38 and the oscillator 39.

The distributor 25 is a hollow body having an inlet section 26 in fluid communication with the first inlet mouth 21 of the main body 20, and an outlet section 27 which communicates with the first outlet mouth and the second 22 and 23 alternately.

The distributor 25 comprises a pair of side walls 28, facing each other and extending parallel to the axis of rotation 25a, and a pair of front walls 29, facing each other and extending at right angles to the axis of rotation 25a and each connecting the two side walls 28 to each other, as shown in particular in Figure 6. The distributor 25 defines a pipe union which is convergent in shape from the inlet section 26 to the outlet section 27.

An infeed duct 30 connects the first inlet mouth 21 of the main body 20 to the distributor 25, in particular at its inlet section 26.

The inlet section 26 of the distributor 25 at least partly receives the infeed duct 30.

The infeed duct 30 is fixed relative to the axis of rotation 25a of the distributor 25.

The infeed duct 30 has an infeed and outfeed end portion 30a and 31 b connecting the first inlet mouth 21 of the main body 20 to the distributor 25.

The infeed duct 30 is at least partly inserted in the inlet section 26 of the distributor 25, in particular at the outlet end portion 31 b.

Advantageously, the inlet section 26 of the distributor 25 is flared so that during its oscillating movement the outfeed end portion 31 b of the infeed duct 30 remains within the inlet section 26.

The flared inlet section 26 of the distributor 25 is divergent according to a respective angle of inclination relative to the side walls 28 of the distributor 25.

Advantageously, the flared inlet section 26 prevents the "SAP" 9 from leaking out during oscillation of the distributor 25 relative to the infeed duct 30, which, as mentioned above, is fixed relative to the distributor 25. The first and second outlet mouths 22 and 23 are positioned relative to each other according to a mutual inclination defining a predetermined angle a.

More specifically, the angle a is equal to the maximum oscillation amplitude of the distributor 25.

The main body 20 has a second inlet mouth 32 connected to a pressurized air source.

The second inlet mouth 32 is located on the opposite side relative to the first and second outlet mouths 22 and 23.

The second inlet mouth 32 is in fluid communication with the chamber 20a of the main body 20 and with first and second outlet mouths 22 and 23. This allows air to be fed under pressure into the stretch T2 of the feeding duct 15 and into the recycling duct 34 connected to the respective outlet mouths 22 and 23.

In other words, when the distributor 25 conveys the "SAP" 9 into one of the two outlet mouths 22 and 23, as illustrated in Figures 9 and 10, the pressurized air flowing out of the second outlet mouth 32 is fed into the other outlet mouth 23, keeping the duct downstream thereof under pressure, as defined by the air source.

Figure 5 shows an alternative embodiment of the valve means 19.

This embodiment differs from the one described above in that the distributor 25 comprises a pair of side panels 33 and 35, facing each other and oscillating in synchrony about respective axes of rotation 33a and 35a, to feed the first and second outlet mouths 22 and 23 alternately and intermittently.

The side panels 33 and 35 extend along a direction parallel to the respective axes of rotation 33a and 35a.

In use, the distributor 25, driven by the mechanical oscillator 39, oscillates in phase with the rotation of the drum 4 and, each time the delivery mouth of the feeding duct 15 comes to face a suction recess 5, the distributor 25 is in communication with the first outlet mouth 22, as illustrated in Figure 7.

In this configuration, the "SAP" 9, fed continuously to the first inlet mouth 21 through the first stretch T1 of the feeding duct 15 travels along the infeed duct 30 and the distributor 25, flowing into the second stretch T2 of the feeding duct 15 by way of the first outlet mouth 22.

It should be noted that the charge of "SAP" 9 fed into the second stretch T2 of the duct 15 is a function of the amplitude of the oscillation of the distributor 25 during which the distributor 25 itself is in communication with the first outlet mouth 22.

In effect, feeding of the "SAP" 9 into the second stretch T2 of the duct 15 is interrupted each time the distributor 25, during its oscillation, comes into communication with the second outlet mouth 23, as illustrated in Figure 10.

In this configuration, the "SAP" 9, fed continuously to the first inlet mouth 21 through the first stretch T1 of the feeding duct 15 travels along the infeed duct 30 and the distributor 25, flowing into the recycling duct 34 by way of the second outlet mouth 23.

It should be noted that feeding of the "SAP" 9 fed into the second stretch T2 of the duct 15 is interrupted for the duration of the amplitude of the oscillation of the distributor 25 during which the distributor 25 itself is in communication with the second outlet mouth 23.

From the foregoing, it may be inferred that intermittent feeding of a charge of "SAP" 9 by means of the feeding duct 15 is a function of the oscillation of the distributor 25.

Advantageously, the oscillating distributor 25 overcomes the above mentioned disadvantages of the prior art because it allows constant feeding of superabsorbent material granule charges which are uniform with each other, with reference in particular to the size of the superabsorbent material granules, since the structure of the distributor 25 neither hinders nor prevents the passage of the superabsorbent material granules, whatever the size of the granules of the "SAP" 9.

Also, the law of oscillatory motion of the distributor 25 makes it possible to achieve intermittent feed which is more controlled and precise than the rotating disc valve means described in the prior art.

Claims

1 . A unit for making absorbent pads for nappies comprising a drum (4) for forming an absorbent pad (2) and having on its peripheral surface (4a) a plurality of suction recesses (5); a hood (6) for feeding at least a first absorbent material (7) and which is mounted peripherally of the drum (4) and facing at least part of the peripheral surface (4a) of the drum (4) and a duct (15) for feeding a charge of granules of superabsorbent material (9) and equipped with a delivery mouth (17) leading to the hood (6); the feeding duct (15) comprising valve means (19) located along a stretch (T) of the feeding duct (15), upstream of the delivery mouth (17) and defining a first stretch (T1 ) of the duct (15) upstream of the valve means (19) and a second stretch (T2) of the duct (15) downstream of the valve means (19); the valve means (19) comprising a main body (20) having at least a first inlet mouth (21 ), in fluid communication with the first stretch (T1 ) of the feeding duct (15), and at least a first outlet mouth (22, 23) in communication with the second stretch (T2) of the feeding duct (15); the unit being characterized in that the valve means (19) comprise a distributor (25) which oscillates, in particular about a respective axis of rotation (25a), to be positioned alternately at a first feed position at the first outlet mouth (22) and a second feed shutoff position of the first outlet mouth (22).

2. The unit according to claim 1 , characterized in that the suction recesses (5) are located on the peripheral surface (4a) of the drum (4) at a predetermined spacing (P); the distributor (25) oscillating about its axis (25a) as a function of the spacing (P) of the suction recesses (5) of the drum (4) in order to feed the outlet mouth (22) intermittently.

3. The unit according to claim 1 or 2, characterized in that the axis of rotation (25a) of the distributor (25) is oriented along a direction parallel to the axis of rotation (4a) of the drum (4).

4. The unit according to claim 1 or 2, characterized in that the axis of rotation (25a) of the distributor (25) is oriented along a substantially horizontal direction.

5. The unit according to any one of claims 1 to 4, characterized in that the distributor (25) is a hollow element having an inlet section (26) in fluid communication with the first inlet mouth (21 ) of the main body (20), and an outlet section (27) which communicates alternately with the outlet mouth (22, 23).

6. The unit according to claim 5, characterized in that the distributor (25) defines a pipe union which is convergent in shape from the inlet section (26) to the outlet section (27).

7. The unit according to any one of claims 1 to 6, characterized in that the valve means (19) comprise an infeed duct (30) having an infeed and an outfeed end portion (30a, 31 b) connecting the first inlet mouth (21 ) of the main body (20) to the distributor (25); the infeed duct (30) being fixed relative to the axis of rotation (25a) of the distributor (25).

8. The unit according to claim 7, characterized in that the infeed duct (30) is at least partly received in the inlet section (26) of the distributor (25), in particular at the outlet end portion (31 b).

9. The unit according to claim 7 or 8, characterized in that the inlet section (26) of the distributor (25) is flared so that during its oscillating movement the outfeed end portion (31 b) of the infeed duct (30) remains within the inlet section (26).

10. The unit according to claim 1 or 2, characterized in that the distributor (25) comprises at least a first and a second side panel (33, 35) which face each other; the first and second side panels (33, 35) oscillating in synchrony about respective axes of rotation (33a, 35a).

1 1 . The unit according to any one of claims 1 to 10, characterized in that the main body (20) comprises a first and a second outlet mouth (22, 23); the first outlet mouth (22) being connected to the second stretch (T2) of the feeding duct (15) and the second outlet mouth (23) being connected to a recycling duct (34) for the superabsorbent material; the distributor (25) oscillating about its axis of rotation (25a) to feed the first and second outlet mouths (22, 23) alternately.

12. The unit according to claim 1 1 , characterized in that the distributor (25) has a defined maximum oscillating angle a; the first and second outlet mouths (22, 23) being inclined to each other at an angle equal to the oscillating angle a.

13. The unit according to any one of claims 1 to 12, characterized in that the main body (20) has a second inlet mouth (32) connected to a pressurized air source; the second inlet mouth (32) being in fluid communication with the outlet mouth (22, 23) of the valve means (19).