WO2023161784A1

WO2023161784A1 - Method and unit for refining a layer in a reconstituted material

Info

Publication number: WO2023161784A1
Application number: PCT/IB2023/051535
Authority: WO
Inventors: Alessandro Granzotto
Original assignee: Comas Costruzioni Macchine Speciali S.P.A.
Priority date: 2022-02-24
Filing date: 2023-02-20
Publication date: 2023-08-31

Abstract

A unit for refining a continuous layer of reconstituted material, comprises feed means (100, 200, 300) for feeding a continuous flow (F) of a mixture containing the reconstituted material, and a refining unit (1) located downstream of the feed means (100, 200, 300) for receiving and processing the continuous flow (F) by a continuous process. The refining unit (1) comprises at least one refining stage (10, 20, 30) equipped with a pair of rollers (40, 50) that delimit a niche for accumulating and mixing the mixture fed to it by the feed means (100, 200, 300), the niche terminating in a through slot defined between the two rollers to produce a continuous layer (C) of predetermined thickness so that the mixture, by passing through the rollers (40, 50), undergoes a continuous mixing and compressing process such as to reduce the particle size of the mixture.

Description

DESCRIPTION

METHOD AND UNIT FOR REFINING A LAYER IN A RECONSTITUTED MATERIAL

Technical field

This invention relates to a method and a unit for refining a layer in reconstituted material, preferably but not necessarily, tobacco, specifically for making traditional or HNB smoking articles.

Background art

Known in the prior art is the production of a web of tobacco from a highly fluid mixture (or "slurry"), hence having a high water content, as described in the introductory section of patent application W02020/058814 in the name of the present Applicant. The method, as described in that document, has the disadvantage of requiring large installations involving high energy consumption, especially at the oven drying stage. Moreover, the need to start with material having a very small particle size also means complex machinery and large factory floor spaces to accommodate the necessary machinery and equipment.

The same patent application also describes a method and a plant for the production of a tobacco web, characterized by the preparation of a mixture of tobacco particles and water, with extremely fine particles and a lower water content than in slurry technology, and wherein the mixture is divided into predetermined portions and then subjected to a succession of distinct laminating steps to obtain the web of tobacco which is then dried.

The Applicant has noticed that although this technology is satisfactorily practicable, it can be further improved, especially in terms of simplifying the plant. In effect, it was noticed that a particularly critical aspect regarded the complexity of the plant needed for initially comminuting the tobacco into extremely fine particles, as well as the aspect of dividing the mixture into portions and then subjecting it to multiple laminating processes. Further, the method and the machine are optimized for a specific web format (particle size, thickness, etc) and adapting to different formats involves onerous procedures.

Moreover, the method requires the use of a plurality of comminuting mills installed at the beginning of the plant to finely shred the material. Shredding is performed with the material in a dry state and creates large quantities of dust. This not only gives rise to the need to contain and/or remove the dust but also creates a fire hazard which in turn means providing flame prevention systems in accordance with the stringent fire regulations currently in force.

Aim of the invention

The aim of this invention is, therefore, to provide a method and a unit for refining a layer in reconstituted material and constituting a technically simpler solution compared to prior art solutions.

A further aim of the invention is to provide a method and a unit for refining a layer in reconstituted material to allow increasing the operational safety of the plant.

A further aim of the invention is to provide a method and a unit for refining a layer in reconstituted material, having high operational flexibility and which, in particular, can be used to obtain webs in different formats and to different specifications.

The aims specified are substantially achieved by a method and a unit in accordance with the features set out in the accompanying claims 1 and 1 1 , respectively, and/or in one or more of the claims dependent thereon.

Brief description of the drawings

Further features and advantages of this invention are more apparent in the exemplary, hence non-limiting description of a preferred, but non-exclusive, embodiment of a method and a unit for refining a layer in reconstituted material, as illustrated in the accompanying drawings, in which:

- Figure 1 is a schematic view of the refining unit according to the invention;

- Figures 2-4 are enlargements of specific portions of the view of Figure 1.

Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, the numeral 1 denotes in its entirety a unit for refining reconstituted tobacco or a material based on reconstituted tobacco according to this invention. By "reconstituted tobacco" is meant a type of tobacco which, at raw material level, is made from the solid waste remaining after the processing of tobacco leaves, and such as, for example, stems and leaf ribs, as well as very small parts of lamina and tobacco dust.

It is, however, specified that the same unit can be used to make layers or webs of generic reconstituted material (in particular of plant origin), not necessarily tobacco, in line with the generic nature of the invention (for example, hemp, aromatic leaves or others still).

In the context of this invention, the tobacco (or reconstituted material) is fed to the refining unit 1 in the form of a continuous flow F of mixture which, in the context of this invention, adopts a continuous layer configuration. This may be obtained by a pair of rollers 100 located downstream of a container 200 of the mixture.

Preferably, the mixture has a liquid content (by weight) of between 20% and 60%, preferably between 30% and 50% and, still more preferably, between 35% and 40%. In other words, the mixture has a liquid content that is lower than that of a slurry but nevertheless such as to make the mixture compact enough to make it suitable for subsequent processes that give it its shape. Preferably, the continuous flow F of mixture is released onto a feed conveyor 300, preferably a belt conveyor, intended to support and move the flow F along a feed direction. Preferably, the continuous flow F placed on the feed conveyor 300 has a layer configuration with substantially uniform thickness.

Preferably, also, the continuous flow F of mixture placed on the feed conveyor 300 has a thickness of between 1 and 10 mm and, more preferably, between 2 and 5 mm.

The refining unit 1 , which receives the continuous flow F of mixture, preferably constant in thickness, is located downstream of the feed conveyor 300.

Although the refining unit 1 is preferably a multi-stage unit, in a possible embodiment, not illustrated but falling within the scope of the same inventive concept, it may comprise one stage only.

In particular, the refining unit 1 comprises a plurality of refining stages 10, 20, 30, specifically three in the embodiment illustrated but whose number may vary from two to more than three, depending on operational requirements. The refining stages 10, 20, 30 each operate on the continuous flow (layer) F of mixture to remix it and compress it in such a way as to reduce the particle size of the mixture at each stage.

Each refining stage 10, 20, 30 comprises a pair of counter-rotating rollers 40, 50, superposed on each other and defining between them a calibrated passage for compressing and forming the mixture material into a continuous layer C with constant thickness. Preferably, the rollers 40, 50 of each pair are substantially identical in diameter.

The two rollers 40, 50 of each stage define, just upstream of them, a niche for accumulating the mixture material which tends to form a mass having the shape of the niche itself, hence deformed and/or pre-mixed compared to the continuous flow or layer arriving at the rollers 40, 50. The mixture material is then progressively "drawn" under the action of the rotating rollers 40, 50 and compressed until obtaining the aforementioned continuous layer C.

Thus, each stage 10, 20, 30 processes the mixture material by flattening it. In the context of this invention, the term "flattening" is used to denote a process that includes steps of accumulating the material in the niche defined between the surfaces of the two rollers (Figures 2-4) and compressing it between the two rollers to form the continuous, constant-thickness layer. Thanks to this process, the mixture material is subjected to a step of mixing in the accumulation zone (niche) which, in combination with the subsequent step of compressing the material between the two rollers and with the specific liquid content of the material, further grinds the particles of the mixture, thereby reducing the particle size. The higher the number stages, therefore, the more the size of the particles can be reduced. The rollers 40, 50 of each flattening stage 10, 20, 30 thus form the actual continuous layer C from the non-planar, shapeless mixture material which has been accumulated in the niche.

Preferably, the rollers 40, 50 of each flattening stage 10, 20, 30 are both motor driven.

Preferably, the speed of rotation at which one of the rollers 40 50 of each pair of rollers is driven is different from that of the other roller. More specifically, the lower roller 50 is driven in rotation at a higher speed than the upper roller 40. Thanks to the higher rotation speed of the roller 50, the continuous layer C leaving the pair of rollers 40, 50 is kept adherent to the roller 50, and for this reason, a scraping member 51 is provided to scrape the continuous layer C off the roller 50. The continuous layer C moving away from the pair of rollers 40, 50 and remaining adherent to the roller 50 which is rotating faster, preferably has a thickness of between 30 pm and 90 pm, more preferably a thickness of between 40 pm and 75 pm and, still more preferably, a thickness of between 50 pm and 60 pm.

According to a preferable aspect, the speed of at least one of the two rollers 40, 50, specifically the (lower) faster roller 50 can be set in such a way that the optimal speed difference between the two rollers 40, 50 is selected each time, as required.

Preferably, just downstream of the pair of rollers 40, 50, each refining stage 10, 20, 30 also comprises a belt conveyor 60 onto which the continuous layer C leaving the pair of rollers 40, 50 is laid after being scraped off by the scraping member 51. Preferably, the continuous layer C is laid on the conveyor with an undulatory motion (giving it a "bellows-like" shape) defining an alternating succession of ridges and recesses along the feed direction of the continuous layer C (Figures 2-4). This undulatory motion optimizes the process of mixing the material in the accumulation niche of the next pair of rollers 40, 50.

The undulatory motion is obtained by driving the belt conveyor 60 downstream of the pair of rollers 40, 50 at a feed speed lower than the speed of the rollers 40, 50 (and in particular, lower than the tangential speed of the faster roller 50) so that the continuous layer C is progressively accumulated. Preferably, the feed speed of the belt conveyor 60 is adjustable so that the unit 1 can be adapted to different operating modes.

Preferably, also, the undulatory motion is obtained downstream of all the stages but not downstream of the last stage, where the motion of the continuous layer C is preferably planar.

Alternatively, only some of the intermediate refining stages may provide the undulatory motion, while the others produce a planar continuous layer that lies flat on the next belt conveyor 60.

The refining unit 1 is also configured in such a way that the belt conveyor 60 located downstream of a pair of rollers 40, 50 also defines the conveyor that feeds the continuous layer C to the next pair of rollers 40, 50 of the next stage. In other words, two successive pairs of rollers 40, 50 are connected by a belt conveyor 60 interposed between them. The first pair of rollers 40, 50, on the other hand, is fed by the feed conveyor 300 which carries the continuous flow F to the first stage 10 of the refining unit 1 . Preferably, the feed conveyor 300 connects the aforementioned rollers 100 directly to the pair of rollers 40, 50 of the first refining stage 10.

Preferably, each belt conveyor 60 is inclined upwards along the feed direction of the continuous layer C, thus defining an ascending feed stretch for the continuous layer C. That way, the belt conveyor 60 makes up for the difference in height between its infeed section, located at a height below the blade of the scraping member 51 (which, as mentioned above, preferably operates on the lower roller 50) and its outfeed section, which directly faces the infeed niche of the next pair of rollers 40, 50.

Preferably, the individual refining stages 10, 20, 30 are modular and/or identical so that the refining unit 1 can be made in a configuration with a desired number of stages. Alternatively, each pair of rollers 40, 50 forms part of a respective, distinct module and, in the same way, each belt conveyor 60 also forms part of a respective, distinct module so that a desired combination of stages can be made.

For example, each refining stage 10, 20, 30 comprises a box-shaped frame 80 containing the two rollers 40, 50 and the respective auxiliary parts (motors, supports, etc) and provided with infeed and outfeed openings which are engageable, respectively, by the preceding belt conveyor 60 and the next belt conveyor 60 (which can be partly inserted into the respective infeed or outfeed opening of the box-shaped frame 80). These openings may be disposed at different heights on account of the inclination of the belt conveyors 60 described above.

Preferably, also, the maximum particle size of the material moving out from the refining unit 1 is between 0.1 mm and 0.7 mm, more preferably between 0.2 mm and 0.5 mm and, still more preferably, between 0.3 mm and 0.4 mm, specifically around 0.35 mm.

In an example embodiment, corresponding to the embodiment of Figure 1 , starting from a maximum particle size of between 0.15 mm and 0.5 mm, the first refining stage brings the maximum particle size to a 0.1 -0.42 mm range, the second refining stage brings the maximum particle size to a 0.085-0.39 mm range and the third refining stage brings the maximum particle size to a 0.06-0.35 mm range.

According to another aspect of the invention, the refining unit 1 also comprises adjusting means 70 acting on one of the rollers of each pair of rollers 40, 50, specifically on the faster, lower roller 50 to adjust the position and/or the thrust pressure of the roller 50 relative to the other roller 40 so as to vary the compression and/or the thickness of the continuous layer C feeding out from the refining stage 10, 20, 30. This is preferably accomplished by supporting the roller 50 with an adjustable supporting member, preferably a linear actuator 71 .

Preferably, also, each belt conveyor 60 is associated with a respective inspection device 90 configured to detect at least one property - for example, the density and/or the thickness - of the continuous layer C placed on it. The inspection device 90 may be connected to a control unit operating by feedback on one or more of the preceding stages 10, 20, 30 to perform a closed-loop adjustment of the compressive action applied by the rollers 40, 50.

The unit 1 described above thus performs a continuous process on a continuous flow F originally having a first thickness value, which is progressively reduced (in successive refining stages) until obtaining a second thickness value, preferably smaller than the first thickness, and a particles size that is smaller than the original particle size.

The present invention achieves the preset aims, overcoming the disadvantages of the prior art.

In effect, the unit and the method according to the invention allow a reduced operating requirement in terms of starting particle size, suitable for "coarsely" ground material that requires less preparation before the refining process on it is started.

Furthermore, the reduction in the particle size according to the invention is performed with the material at the "wet stage", that is to say, after the liquid has been added, thus greatly reducing the risk of fire due to the circulation of powder.

Furthermore, the unit is very flexible, making it possible to control and adjust different web parameters including, for example, thickness and density, by operating, in particular, on the refining rollers of each stage. Moreover, the modular configuration of the refining unit means it can be configured with a variable number of stages, as needed.

Claims

1 . A method for refining a continuous layer of reconstituted material, comprising the following steps:

- feeding a continuous flow (F) of a mixture containing the reconstituted material to a refining unit (1 );

- subjecting the continuous flow (F), in the refining unit (1 ), to at least one step of mixing and compressing by a continuous process so as to reduce the particle size of the mixture and obtain a continuous layer (C); wherein the step of mixing and/or compressing is carried out by at least one pair of rollers that delimit a niche for accumulating and mixing the mixture, the niche terminating in a through slot defined between the two rollers to produce a continuous layer (C) of predetermined thickness.

2. The method according to claim 1 , wherein the mixture of the continuous flow (F) has a liquid content of between 20% and 60%, preferably between 30% and 50% and, still more preferably, between 35% and 40%.

3. The method according to claim 1 or 2, wherein the step of feeding the continuous flow (F) is accomplished by supporting the continuous flow (F) of mixture by means of a feeding conveyor (300), specifically a belt conveyor.

4. The method according to any one of the preceding claims, wherein the continuous layer (C) feeding out from the pair of rollers (40, 50) is made to remain adherent to one of the two rollers (40, 50), specifically the lower roller (50), and wherein the roller (50) applies a scraping action on the continuous layer (C) by means of a scraping member (51 ) to detach the continuous layer (C) from the roller (50).

5. The method according to any one of the preceding claims, wherein the continuous layer feeding out from the pair of rollers (40, 50), specifically, scraped off by the scraping member (51 ), is released onto a belt conveyor (60) in such a way as to form a wavy shape defined by a succession of alternating ridges and recesses along the feed direction of the continuous layer (C).

6. The method according to claim 5, wherein one of the rollers (50) of the pair of rollers (40, 50), specifically the roller (50) that acts in conjunction with the scraping member (51 ), more specifically, the lower roller (50), is driven in rotation at a higher speed than the other roller (340).

7. The method according to claim 5 or 6, wherein the belt conveyor (60) located downstream of the pair of rollers (40, 50) is driven at a feed speed lower than the rollers (40, 50) of the pair of rollers, specifically, lower than the higher speed roller (50), so as to obtain the wavy shape.

8. The method according to any one of the preceding claims, wherein the refining unit (1 ) comprises a plurality of refining stages (10, 20, 30) disposed in sequence along the mixture feed direction and each comprising a pair of rollers (40, 50), each refining stage (10, 20, 30) performing a step of mixing and compressing the mixture by a continuous process, and wherein each refining stage (10, 20, 30) performs a step of accumulating the mixture in the niche defined between the two respective rollers (40, 50) followed by a compressing action applied by the two rollers (40, 50) to form a continuous layer (C) of constant thickness, preferably the continuous layer feeding out from each pair of rollers (40, 50) being made to remain adherent to one of the two rollers (40, 50), preferably the lower roller (50) and then being scraped off the roller (50) by a corresponding scraping member (51 ).

9. The method according to claim 8 when dependent on claim 5 or 6 or 7, wherein the wavy shaped continuous layer (C) is formed upstream of a subsequent refining stage (20, 30) so that the wavy shaped continuous layer (C) is then processed in that subsequent refining stage (20, 30).

10. The method according to any one of the preceding claims, further comprising a step of adjusting the position and/or the thrust pressure of a roller (50) relative to the other roller (40) of the pair of rollers (40, 50) so as to vary the compression and/or the thickness of the continuous layer (C) feeding out from the refining stage (10, 20, 30).

11. A unit for refining a continuous layer of reconstituted material, comprising:

- feed means (100, 200, 300) for feeding a continuous flow (F) of a mixture containing the reconstituted material;

- at least one refining stage (10, 20, 30) equipped with a pair of rollers (40, 50) that delimit a niche for accumulating and mixing the mixture fed to it by the feed means (100, 200, 300), the niche terminating in a through slot defined between the two rollers (40, 50) to produce a continuous layer (C) of predetermined thickness so that the mixture, by passing through the rollers (40, 50), undergoes a continuous mixing and compressing process such as to reduce the particle size of the mixture.

12. The unit according to claim 1 1 , wherein the feed means comprise a feed conveyor (300), specifically a belt conveyor, located just upstream of the at least one refining stage (10, 20, 30) and configured to feed the continuous flow (F) of mixture to the niche of the refining unit (1 ).

13. The unit according to claim 12, wherein the feed conveyor (300) extends as far as the niche and to a distance of between 0.5 and 5 cm, preferably between 1 and 3 cm, from the pair of rollers (40, 50).

14. The unit according to any one of claims 11 to 13, wherein the at least one refining stage (10, 20, 30) comprises a scraping member (51 ), adjacent to one of the rollers (40, 50), specifically the lower roller (50), for detaching the continuous layer (C) from the roller (50).

15. The unit according to claim 14, wherein the roller (50) associated with the scraping member (51 ) is driven in rotation at a speed different from that of the other roller (40), specifically at a higher speed.

16. The unit according to any one of claims 11 to 15, wherein the at least one refining stage (10, 20, 30) comprises, downstream of the pair of rollers (40, 50), a belt conveyor (60) that is disposed and/or configured for receiving the continuous layer (C) feeding out from the two rollers (40, 50), the belt conveyor (60) being preferably inclined upwards along the feed direction of the continuous layer (C).

17. The unit according to claim 16, wherein the belt conveyor (60) is driven at a feed speed lower than the tangential speed of the rollers (40, 50) of the preceding pair of rollers (40, 50), specifically of the higher speed roller, so as to obtain a wavy shape defined by a succession of alternating ridges and recesses along the feed direction of the continuous layer (C).

18. The unit according to any one of claims 1 1 to 17, wherein the refining unit (1 ) comprises a plurality of refining stages (10, 20, 30) disposed in sequence along the mixture feed direction and each comprising a pair of rollers (40, 50), each refining stage (10, 20, 30) being configured to perform a step of mixing and compressing the continuous flow (F) of mixture, and wherein the pair of rollers (40, 50) of each refining stage (10, 20, 30) being preceded by a respective belt conveyor (300, 60) located just upstream of the pair of rollers (40, 50) so as to convey the mixture and accumulate it in the niche defined between the two rollers (40, 50).

19. The unit according to any one of claims 1 1 to 18, further comprising adjusting means acting on one of the rollers (40, 50) of each pair of rollers (40, 50), specifically on the lower roller (50) to adjust the position and/or the thrust pressure of the roller (50) relative to the other roller (40) so as to vary the compression and/or the thickness of the continuous layer (C) feeding out from the refining stage (10, 20, 30).

20. The unit according to claim 18 or 19, wherein the refining stages (10, 20, 30) are modular and/or identical so that the refining unit (1 ) can be made in a configuration with a desired number of stages.