MX2008003253A - A unit and a method for forming absorbent pads used in nappies/diapers - Google Patents

Abstract

Multilayer absorbent pads for nappy/diaper pants are manufactured on a unit (1) comprising a first device (3a) and a second device (3b) by which respective first and second layers (4a, 4b) of absorbent material (5) are taken up from two infeed stations, shaped, and transferred to two release stations. The devices (3a, 3b) are synchronized in operation, and associated by way of a transfer station (8) at which the first layer (4a) of absorbent material is joined directly to the second layer (4b) , positioned selectively and with the second layer still retained by suction on the second device (3b);the two layers are thereupon compressed simultaneously to form an absorbent pad (2) that emerges from the unit as a stable, one-piece core.

Description

A UNIT AND METHOD FOR FORMING ABSORBENT PADS USED IN DISPOSABLE SHOES / DIAPERS TECHNICAL FIELD The present invention relates to a unit and method for forming multi-layer absorbent pads as used in sanitary articles. In particular, the present invention relates to a unit of the type in question, such as that which can be usefully used to make absorbent pads for disposable pants / baby diapers.

TECHNICAL BACKGROUND A typical disposable diaper or diaper currently comprises an absorbent pad normally sandwiched between a permeable inner layer of spunbonded fabric and an impermeable outer layer of polyethylene. Responding to market demand, manufacturers of disposable underpants / diapers now offer an anatomically delineated product, preferably with pads formed to conform to a selected anatomical shape. The method commonly adopted in this instance is one for forming the individual pads in a drum having a plurality of peripheral suction cavities, each formed to coincide with the required anatomical shape, and fed at a point on the periphery with a current of absorbent material. The absorbent material deposited in the cavities of the drum is compacted by a roller, at a point downstream. The stream of absorbent material is a mixture of cellulose pulp, or fluff pulp, wherein the granules of the superabsorbent polymer material (SAP) are introduced either with or against the flow, homogeneously to a greater or lesser degree, in accordance with the requirements. The most recent disposable diapers / diapers also have a double thickness of absorbent pad: a smaller, first, upper layer placed in a second, larger, lower layer. In certain cases, the first layer also needs to be placed further forward in the second layer by a greater or lesser distance in order to reinforce the selected areas, depending on the gender or age of the baby or other factors In addition, to improve the drainage of absorbed liquid and simultaneously reduce production costs, manufacturers are opting for absorbent pads of which the composition is based on an increasing amount of SAP granules and a correspondingly smaller amount of fluff pulp. Adopting this new formulation, the need also arises for the absorbent pad to be compacted more effectively, since with a higher proportion of an SAP material, which usually has a consistency similar to sand, the structure tends to be less cohesive To meet the requirement for the two pad layers, the aforementioned drums have a suction cavity with a greater depth area, delineated to match the shape of the finished pad. In this example, however, a special drum is necessary for each relative position of the two layers, so that machines having only one drum offer little versatility. The absorbent material however can be successfully compacted using a drum of the type in question, creating a one-piece core that is easily handled or processed. In an alternative solution, use is made of a first drum with peripheral suction cavities delineated to match the shape of the largest layer of the pad, and a second drum adjacent to the first, a given distance away, with suction cavities delineated to match the shape of the smallest top layer. Located below the drums is a conveyor belt, where layers of absorbent material are released. The individual layers are compacted by respective rollers operating between each drum and the conveyor. The largest layer is fed by the conveyor in the space below the second drum, from which the smallest layer in the same largest layer is released in a selected position. The time of the two drums can be controlled in such a way as to vary the position in which the second layer is released in the first layer. One drawback with this second solution, which contemplates a first compression of only the first layer and a second compression of the second when placed in pairs with the first, is that the two layers can not be compacted in such a way that they form a nucleus of a single piece, since the compression is applied in two successive stages, rather than simultaneously in a single step immediately before the absorbent pad is assembled with the other parts of the disposable pants / diapers. The object of the present invention is to provide a unit for forming multi-layer absorbent pads used in disposable diapers / diapers, which offer greater versatility than the prior art units, and a method for forming said pads. A further object of the invention is to provide a unit and method for forming multi-layer absorbent pads used in disposable underpants / diapers so that at least two layers of the absorbent material can be suitably placed and compacted simultaneously to produce a core of an absorbent material. single piece, before the absorbent pad is assembled with the disposable pant / diaper.

BRIEF DESCRIPTION OF THE INVENTION The stated objective is duly performed in accordance with the present invention in a unit and method for forming multi-layer absorbent pads in disposable diapers / diapers, as claimed in claims 1 and 15 or in any of the subsequent individual claims a and dependently. directly or indirectly of claims 1 and 15. The invention will now be described in detail, by way of example, with the help of the accompanying drawings, in which: Figure 1 shows a preferred embodiment of a unit for forming absorbent pads of layers multiple used in disposable pants / diapers, observed schematically in a frontal elevation; Figures 2a, 2b and 2c are three plan views showing an absorbent pad comprising two superimposed layers of absorbent material occupying three possible positions one relative to the other; Figures 2d, 2e and 2f are three side elevation views showing an absorbent pad comprising two superposed layers of absorbent material occupying three possible positions one relative to the other; Figures 3a and 4a show a first element of the unit as in Figure 1, which are illustrated in the two alternative embodiments and are viewed in perspective; Figures 3b and 4b show a second element of the unit as in Figure 1, which is illustrated in two alternative embodiments and are viewed in perspective. With reference to Figure 1, the number 1 denotes a unit, in its entirety, by means of which the absorbent multiple layer pads 2 (Figures 2a-2f) for disposable pants / baby diapers are formed. In a more non-exclusive preferred configuration, the unit 1 has an upper section comprising a first device 3a and a second device 3b of which the function is to collect, form and transfer a first layer 4a and a second layer 4b, respectively, of an absorbent material denoted by the number 5. The first device 3a and the second device 3b appear respectively as a first drum 6a and a second drum 6b located side by side and counter-rotating around the respective parallel axes 7a and 7b. The peripheral surfaces of the first and second drums 6a and 6b rotate tangentially towards one another in a transfer section denoted by the number 8.

Numbers 9a and 9b denote conventional internal feeding stations from which the relative streams of absorbent material 5 are directed in an outer peripheral portion 10 of each drum 6a and 6b. The absorbent material 5 is placed in suitable suction holes 11, which in a first embodiment take the form of a continuous circular channel 12 extending circumferentially around the peripheral portion 10 (Figures 4a and 4b). Alternatively, the recesses 11 may consist of a plurality of discrete cavities 13 aligned and spaced apart circumferentially around the peripheral portion 10 (3a and 3b). In both solutions, the recesses 11 are formed to match the shape of the absorbent pad 2 being manufactured, and are capable of retaining the absorbent material in advance 5 by suction. In particular, the function of the first drum 6a is to collect, form and transfer the first smaller layer 4a of the absorbent material 5, while that of the second drum 6b is to collect, form and transfer the second larger layer 4b of the absorbent material 5. In practice, the absorbent pads 2 for disposable pants / diapers can be formed by a unit 1 presented with both drums 6a and 6b having the recesses 11 of the same geometry (both with continuous channels 12, or both with discrete cavities 13), or with the first drum 6a presenting discrete cavities 13 and the second drum 6b presenting a continuous channel 12. In a preferred embodiment, according to the present invention, the recess 11 of the first drum 6a will have discrete cavities 13, in such a way that the first layer 4a can be placed in a selected position relative to the second layer 4b. The absorbent material 5 is transferred by means of two rotating drums 6a and 6b of the respective internal feed stations 9a to the respective release stations 14a and 14b. The release station 14a of the first drum 6a coincides with the transfer station 8 where the first layer 4a joins the second layer 4b. More precisely, it is in the transfer station 8 that the drums 6a and 6b interface and interact, causing the first layer 4a carried by the first drum 4a to be placed directly on the second layer 4a carried by the second drum 6b. The relative positioning of the two layers 4a and 4b can vary as required, by coordinating the rotation of the drums 6a and 6b. Both layers 4a and 4b are therefore retained in the second drum 6b by suction until the relative release station 14b, after which the two same assembled layers 4a and 4b that make up the absorbent pad, are directed as one in one. compression station 15 and are compacted to form a single core. The compression station 15, located in this way downstream of the second drum 6b, includes a transport roller 16 positioned tangentially to the drum itself 6b in the release station 14b. The roller 16 will consequently turn in the opposite direction to the drum 6b. The compression station 15 further comprises at least one compression element 17, positioned along a peripheral portion of the transport roller 16 and operating in conjunction with the roller 16, by means of which the first and second layers 4a and 4b of the absorbent material 5 are compacted together to form a one-piece core. The compression element 17 consists of a pressure roller 19 of smaller diameter, combined with the outer surface of the transport roller 16 to create a cavity (not shown) that can be delineated to match the shape of the absorbent pad 2 that is pressed , or alternatively, lacking any particular geometry and presented flat contact surfaces. When the rollers 19 and 16 are combined to create a formed cavity, a uniform compression force can be applied to the complete pad 2. The pressure roller 19 can usefully have a surface delineated to match the shape of the pad 2. , and the transport roller 16 can be flat, thus allowing the smaller roller 19 to be replaced as necessary with another of different geometry, more easily than the larger roller 16. Alternatively, the surface of the transport roller 16 can be delineated , and the pressure roller 19 left flat.

Where the rollers 19 and 16 combine to create a cavity of no different geometry, with flat surfaces, the compressive force is applied non-selectively to the pad 2, the result being that the pad 2 can not be compacted uniformly. Before being compressed simultaneously, the two assembled layers 4a and 4b of absorbent material 5 can be wrapped, to favor, in a protective tissue wrapper 20 which will help to ensure a more stable cohesion of the superabsorbent granular material and the fluff pulp. Preferably, the layers of the core are sandwiched between the two layers of the fabric wrap 20, namely a first fabric wrap 20a covering the top of the pad 2, and a second fabric wrap 20b covering the bottom. The first fabric wrap 20a is unwound from the rollers (not shown) which are directed over the guide elements 21 and are applied immediately downstream of the transfer station 8, just after the first layer 4a has been joined to the second one. layer 4b, in the upper part of the pad 2 facing away from the second drum 6b. The second fabric wrap 20b, likewise unrolled from the rolls (not shown), is applied to the underside of the pad 2 that faces away the transport roller 16 when it is rotating, at a point that coincides with the station. of compression 15 and marginally preceding the pressure roller 19. Current below the compression station 15, the unit comprises a sealing and cutting station 22 of the familiar type, widely used in other devices. In the case of the second drum 6b having a gap 1 1 with discrete cavities 13, the pads 2 will be divided into individual pieces, and the sealing unit 22 will simply be secured to the four edges of the tissue wrap 20. Where the second drum 6b presents a continuous channel 12, on the other hand, the fabric wrap 20 will be sealed only along the two longitudinal edges of the pad 2. Where the absorbent pad 2 is formed as a continuous mesh, it must be cut and Divide into individual pieces. Also, the area 22a where the sealing step is carried out is immediately followed by an area 22b where the continuous strip of the pad 2 is divided into discrete portions. If the pad 2 is already divided into discrete portions, on the other hand, then only the tissue wrap 20 needs to be cut. If the first drum 6a and the second drum 6b are formed with cavities 13, preferably they will be closely spaced from each other to minimize the waste of fabric wrap 20.

Downstream of the sealing and cutting station 22, the unit comprises a separation mechanism 23 of the familiar type by means of which the individual pads 2, formed, cut and facing the tissue wrap 20, are placed at a given distance. next to each other on a conveyor belt 24 which will direct them to the processing stations under the unit 1. The separation mechanism 23 comprising a plurality of carriers 25 rotates around a circular path and is controlled by cams 26. carriers 25 are able to delay the passage of the pads 2 between the sealing and cutting station 22 and the conveyor 24, so that they will be further separated in the band. The carriers 23 are then accelerated through the second half of the circular path to remain correctly in time with the sealing and cutting station 22 and pick up an additional pad 2. The drawbacks of the prior art are overcome in accordance with the present invention , and the established objectives are carried out in this way. First, it will be noted that a unit 1 for forming absorbent pads used in disposable diapers / diapers as described and illustrated, combines all the advantages of existing units. The method according to the invention is likewise effective for forming absorbent pads for disposable underpants / diapers, so as to provide optimal placement and perfect compression of the two layers that combine to form a one-piece absorbent core. Also, great versatility is produced by the unit to form absorbent pads in accordance with the invention than with conventional machines in wide use. By using an individual article of equipment, in effect, the assembled layers of absorbent material can be correctly positioned one relative to the other and simultaneously subjected to an initial compression action.

Claims (21)

NOVELTY OF THE INVENTION CLAIMS

1. - A unit for forming multi-layer absorbent pads used in disposable diapers / diapers, comprising a first device (3a) and a second device (3b) by means of which the respective first layer (4a) and the second layer (4b) of the absorbent material (5) is collected from respective indoor feeding stations (9a, 9b), formed and transferred to release stations (14a, 14b), and a compression station (15) placed downstream of the second device ( 3b), characterized in that the absorbent material (5) is collected, formed and transferred by the first and second devices (3a, 3b) related and operating in conjunction with each other in such a way that it transfers the first layer (4a) directly to the second layer (4b) in a predetermined position that coincides with a transfer station (8).

2. The unit according to claim 1, further characterized in that the absorbent material (5) is collected, formed and transferred by a first device (3a) and a second device (3b) consisting respectively of a first drum (6a) ) and a second drum (6b) placed one along the other, counter-rotating around two parallel axes (7a, 7b) and peripherally tangential to each other in the transfer station (8).

3. - The unit according to claim 2, further characterized in that each of the first and second drums (6a, 6b) has a suction gap (11) extending along an outer peripheral portion (10) and serving to contain the absorbent material (5), delineated to match the shape of the absorbent pad (2) in production.

4. The unit according to claim 3, further characterized in that the suction gap (11) produced by the first drum (6a) has a transverse dimension smaller than the transverse dimension of the gap (11) that is produced by the second drum (6b), so that the first layer (4a) of the absorbent material is smaller than the second layer (4b).

5. The unit according to claim 4, further characterized in that the suction gap (11) of the first drum (6a) consists of a continuous circular channel (12) extending circumferentially along the peripheral portion (10). ).

6. The unit according to claim 4, further characterized in that the suction gap (11) of the second drum (6b) consists of a continuous circular channel (12) extending circumferentially along the peripheral portion (10). ).

7. The unit according to claim 4, further characterized in that the suction gap (11) of the first drum (6a) consists of a plurality of discrete cavities (13) aligned and distributed uniformly and circumferentially along the portion peripheral (10).

8. The unit according to claim 4, further characterized in that the suction gap (11) of the second drum (6b) consists of a plurality of discrete cavities (13) aligned and distributed uniformly and circumferentially along the the peripheral portion (10).

9. The unit according to claim 2, further characterized in that the compression station (15) comprises a transport roller (16) that contragirates tangentially with the second drum (6b), and at least one compression element (17). ) operates in conjunction with the roller (16) and is positioned along a peripheral portion (18) of the roller itself (16), by means of which the first layer (4a) and the second layer (4b) of the absorbent material (5) forming the pad (2) are compacted simultaneously to form a one-piece core.

10. The unit according to claim 9, further characterized in that the compression element (17) comprises a pressure roller (19) that is combined with the transport roller (16) to create a cavity with contours that match the shape of the absorbent pad (2), in such a way that the uniform compression force is applied to the pad (2).

11. The unit according to claim 9, further characterized in that the compression element (1) comprises a pressure roller (19) with a flat surface, by means of which the non-uniform compression force is applied to the absorbent pad (2).

12. The unit according to claim 1, further characterized in that the first and second layers (4a, 4b) of the absorbent material forming the absorbent pad (2) are wrapped together in at least one sheath of protective fabric (20) .

13. The unit according to claim 1, further characterized in that it comprises a seal and cut station (22) located downstream of the compression station (15).

14. The unit according to claim 13, further characterized in that it comprises a separation mechanism (23) located downstream of the seal and cut station (22), by means of which the individual absorbent pads (2) are collect and place on a conveyor (24).

15. A method for forming multi-layer absorbent pads for disposable pants / drs, which includes the steps of feeding absorbent material (5) to a first device (3a) and a second device (3b) by means of which a first respective layer (4a) and second layer (4b) of the material itself, joining the first layer (4a) of the absorbent material (5) superimposed on the second layer (4b) of the absorbent material (5), and compressing the first layer (4a) and the second layer (4b) of absorbent material (5) simultaneously for compacting the absorbent pad (2), characterized in that the step of joining the first layer (4a) of the absorbent material (5) superimposed on the second layer ( 4b) of the absorbent material (5) includes the step of transferring the first layer (4a) into the second layer (4b) while the second layer (4b) is retained by the second device (4b). (3b)

16. The method according to claim 15, further characterized in that the first layer (4a) and the second layer (4b) are compressed at least once, and only after joining.

17. The method according to claim 15, further characterized in that the step of feeding the absorbent material to the first device (3a) includes the step of directing the material in a continuous channel (12) produced by a peripheral portion (10) of the first device (3a)

18. The method according to claim 15, further characterized in that the step of feeding the absorbent material to the second device (3b) includes the step of directing the material in the continuous channel (12) produced by a peripheral portion (10) of the second device (3b)

19. The method according to claim 15, further characterized in that the step of feeding absorbent material into the first device (3a) includes the step of directing the material in a plurality of discrete cavities (13) evenly distributed to along a peripheral portion (10) of the first device (3a).

20. - The method according to claim 15, further characterized in that the step of feeding absorbent material to the second device (3b) includes the step of directing the material in a plurality of discrete bags (13) evenly distributed along a peripheral portion (10) of the second device (3b).

21. The method according to claim 15, further characterized in that it includes an additional step wherein the absorbent pad (2) formed of the first layer (4a) and the second layer (4b) of the absorbent material (5), is wraps in at least one tissue wrap (20), before the first layer (4a) and the second layer (4b) of the absorbent material (5) are compressed simultaneously.