WO2019111166A1

WO2019111166A1 - Machine for the production of a continuous rod of the tobacco industry

Info

Publication number: WO2019111166A1
Application number: PCT/IB2018/059655
Authority: WO
Inventors: Ivan Eusepi; Eura Trivisonno; Fausto Mengoli; Eros Stivani; Massimo Sartoni; Luca Federici
Original assignee: G.D S.P.A.
Priority date: 2017-12-06
Filing date: 2018-12-05
Publication date: 2019-06-13
Also published as: PL3720304T3; EP3720304A1; EP3720304B1

Abstract

This invention relates to a machine for the production of a continuous rod (C) of the tobacco industry, comprising a forming station (2), adapted to receive a web of wrapping material (I) and a semi-finished product (P) of the tobacco industry. The station (2) comprises a forming beam (4), on which the semi-finished product (P) is disposed on top of the web (I), and is configured to progressively wrap the web (I) round the semi-finished product (P) to define a continuous rod (C). The machine also comprises a detecting station (3) located downstream of the forming beam (4) and comprising at least one electromagnetic detector (5) to detect one or more properties of the semi-finished product (P). The electromagnetic detector (5) is disposed in proximity to a stretch of the rod forming beam (4) upstream of the point where the web of wrapping material is completely wrapped round the semi-finished product (P) so that the electromagnetic detector (5) faces a surface of the semi-finished product (P) which is not yet wrapped completely in the web (I).

Description

MACHINE FOR THE PRODUCTION OF A CONTINUOUS ROD OF THE TOBACCO INDUSTRY

Technical field

This invention relates to a machine for making a continuous rod of the tobacco industry.

In particular, the object of this invention is to make one or more continuous rods from a semi-finished product of the tobacco industry wrapped in a tube of wrapping material. The continuous rod or rods are then cut into rod segments by a specific cutting device in proximity to an outfeed end of the machine.

Background art

In many different situations in the tobacco industry, it is necessary to wrap a suitable semi-finished product in a wrapping material to make a continuous rod which, at later stages in the production process, is divided into separate segments to form the finished product to be made.

A strongly felt need in the industry is that of being able to efficiently check some of the properties of the semi-finished product, such as weight or density, so as to ensure that the production process of the rod, and ultimately of the finished product, complies with one or more quality parameters associated with the properties measured.

This need is normally satisfied by taking measurements of the rod after the rod has been formed; that is to say, when the semi-finished product has been wrapped completely in a web of wrapping material, in order to check that it has been filled correctly.

Measuring is performed by non-invasive measuring means such as sensors which use electromagnetic waves that are capable of passing through the continuous rod to measure one or more properties of the semi-finished product.

This solution is not, however, applicable in some production contexts: for example, if the web of wrapping material has metallic or at least partly metallized portions, these interfere with the measuring process by screening or distorting the radiation and thus preventing measurements from being taken correctly through the thickness of the semi-finished product.

This problem is all the more evident in the following non-limiting example of machines for the production of continuous rods of tobacco.

Generally speaking, machines for making continuous rods of tobacco involve the use of a substantially vertical duct which is fed from below with a continuous flow of tobacco particles and at the top end of which there is a suction belt on which a continuous mass of tobacco is formed.

The suction belt is adapted to feed the semi-finished, continuous mass of tobacco along a predetermined path defined by the suction belt itself to a preforming device, which produces a continuous stream, and then to a station for forming a continuous tobacco rod where a web of wrapping material is wrapped around the continuous tobacco stream to form a continuous rod or cylinder of the tobacco industry, such as a cigarette rod, which is then cut into segments by a suitable cutting device.

More specifically, before being sent into the forming channel of the forming beam, the continuous stream of tobacco is suitably preformed and progressively compacted by the preforming device.

In this context, to ensure that the articles resulting from this production process have the right amount of tobacco in them, it is essential to measure the quantity of tobacco that is transferred into the infeed end of the forming channel.

It is obvious that the properties of the semi-finished product cannot be measured in the manner mentioned above if the paper used to wrap it comprises metal particles.

In this specific context, machines are known in the prior art in which the detecting station is disposed along the suction belt.

This feature guarantees that the continuous mass of tobacco can be measured without interference from metallic components applied to the web of wrapping material.

The Applicant has found, however, that this solution has considerable operational disadvantages which make it very inefficient in the performance of its functions.

In particular, this solution is not capable of providing an accurate measurement of the quantity/weight of the mass of tobacco which is transferred to subsequent production steps because some of the tobacco measured continues to be held by suction on the suction belt and falls off the belt by gravity or on account of the mechanical vibrations before being actually transferred to the processes downstream.

For this reason, even a measurement that indicates a correct amount of tobacco might result in a finished product that is not properly filled.

The material held by the suction belt is, in effect, a "suspended" mass and produces a level of uncertainty which negatively affects measurement precision.

Generally speaking, this problem also affects other tobacco industry production processes in which a continuous rod is formed by wrapping a semi-finished product, such as a mass of tobacco fibre, a stream of filter material, a uniform or non-uniform succession of segments of semi-finished products for making cigarettes or aerosols, for example of filter material or materials containing flavouring substances, in a web of wrapping material when the wrapping material comprises metallic particles.

Disclosure of the invention

In this context, the technical purpose which forms the basis of this invention is to overcome the above mentioned drawbacks of the prior art by proposing a machine for making at least one continuous rod of material for the tobacco industry. In particular, this invention has for an aim to provide a machine for the production of a continuous rod of the tobacco industry, capable of allowing optimum and accurate checking of the properties of the semi-finished product using an electromagnetic wave detector even when the rods made are wrapped in material which is at least partly metallized or which contains metallic parts.

The technical purpose indicated and the aims specified are substantially achieved by a machine for making at least one continuous rod of the tobacco industry, comprising the technical features set out in one or more of the accompanying claims.

This invention discloses a machine for the production of at least one continuous rod of the tobacco industry, comprising a forming station, adapted to receive a web of wrapping material from means for feeding the web and a semi-finished product of the tobacco industry from means for feeding the semi-finished product, where the station comprises a forming beam on which the semi-finished product is placed on top of the web, specifically in such a way that it rests thereon.

The forming station is configured to progressively wrap the web round the semi-finished product to define a continuous rod wrapped in a tube of wrapping material.

The machine also comprises a detecting station located in the proximity of the forming beam and comprising at least one electromagnetic detector to detect one or more properties of the semi-finished product.

The electromagnetic detector is disposed in the proximity of a stretch of the rod forming beam upstream of the point where the web of wrapping material is completely wrapped round the semi-finished product so that the electromagnetic detector faces a surface of the semi-finished product which is not yet wrapped completely in the web. Preferably, the electromagnetic detector directly faces the top surface of the semi-finished product.

Advantageously, the special structure of the machine for making a continuous rod of the tobacco industry according to this invention allows precisely measuring at least one property of the semi-finished product, even if the rod being made has a cover which is at least partly metallized or contains metallic particles, specifically by taking a measurement before the rod is completely formed and, at the same time, after or during the transfer of the semi-finished product to the machine from a processing station preceding it.

This measurement can therefore be performed correctly irrespective of the properties of the material used for wrapping and of possible loss of part of the semi-finished product fed in: for example, part of the continuous mass of tobacco during its transfer from one production step to the next.

The dependent claims, which are incorporated herein by reference, correspond to different embodiments of the invention.

Brief description of the drawings

Further features of the invention and its advantages are more apparent in the non-limiting description below, with reference to preferred but non exclusive embodiments of a machine for the production of a continuous rod of the tobacco industry, as illustrated in the accompanying drawings, in which:

- Figure 1 shows a first possible embodiment of the machine according to this invention;

- Figure 2 shows a detail of the machine of Figure 1 ;

- Figure 3 shows another possible embodiment of the machine according to this invention;

- Figure 4 shows a detail of the machine of Figure 3;

- Figure 5 shows a further possible embodiment of the machine according to this invention;

- Figure 6 shows a detail of the machine of Figure 1 ;

- Figure 7 shows a further possible embodiment of the machine according to this invention; - Figure 8 shows a further possible embodiment of the machine according to this invention.

Detailed description of preferred embodiments of the invention

The numeral 1 in the accompanying drawings denotes in its entirety a machine for making at least one continuous rod of the tobacco industry.

In proximity to its outfeed end, the machine comprises a cutting device, of known type not illustrated, used for subsequently cutting the continuous rod into rod segments.

The machine 1 comprises a forming station 2 and a detecting station 3. The forming station 2 is adapted to receive a web of wrapping material Ύ from means for feeding the web of wrapping material Ύ and a semi-finished product“P” of the tobacco industry from means for feeding the semi-finished product“P” and is configured to progressively wrap the web of wrapping material T round the semi-finished product“P” to form a continuous rod“C” of the tobacco industry, comprising a continuous rod of a semi-finished product“P” wrapped in a tube of wrapping material T.

In other words, the forming station 2 is fed simultaneously with the web of wrapping material Ύ and the semi-finished product“P” by suitable feed means, adapted to move the web of wrapping material Ύ or the semi- finished product“P” and to progressively form them into the required shape by enclosing the semi-finished product“P” in the web of wrapping material

More specifically, the feed means feed the respective web of wrapping material T or semi-finished product“P” in such a way that the semi-finished product“P” is placed on top of the web of wrapping material Ύ, preferably resting on the web of wrapping material Ύ.

The web of wrapping material Ύ is a web of material, such as paper for example, which is at least partly metallic or metallized: that is to say, the web of wrapping material Ύ comprises metallic particles.

The semi-finished product“P” may be any material used in the tobacco industry as a filling for the components of a smoking article: for example, a mass of tobacco fibre, a stream of filter material, a uniform or non-uniform succession of segments of semi-finished products for making cigarettes or aerosols, for example of filter material or materials containing flavouring substances.

Operatively, the forming station 2 comprises a forming beam 4 on which the semi-finished product“P” is disposed on top of the web of wrapping material T, preferably resting thereon, and along which it is moved in order to obtain the continuous rod“C”.

The detecting station 3 is located in proximity to the forming beam 4 and comprises at least one electromagnetic detector 5 to detect one or more properties of the semi-finished product“P”.

By "property" is meant one or more features of interest, depending on the type of filling material being measured.

These properties may comprise, for example, those in the following, non- exhaustive list: weight, density, humidity, inclusion of additional elements, correct sequence of parts of the semi-finished product “P” or their presence/absence, integrity, even partial, or position in relation to the subsequent processing steps, such as for example, a cutting device for severing the continuous rod.

More in detail, again by way of example, if the semi-finished product“P” is a stream of filter material, it might be necessary to detect the position or structural integrity of flavouring capsules inserted in the stream, for example by measuring the degree of humidity of the part of the stream containing the capsule.

The term "electromagnetic detector" 5 is used to denote any detector capable of performing a non destructive measurement through the thickness of the semi-finished product“P” using electromagnetic waves, specifically electromagnetic waves whose frequency is such as to be susceptible of interference from, or to be masked/distorted by, interaction with metallic particles.

For example, the electromagnetic detector 5 is an electromagnetic wave detector operating at a wavelength of between 10⁹ and 10¹³ Hz. More specifically, the detector is a detector in the field of microwaves.

The electromagnetic detector 5 is disposed in proximity to a stretch of the rod forming beam 4 upstream of the point where the web of wrapping material is completely wrapped round the semi-finished product P so that it faces a surface of the semi-finished product“P” which is not yet wrapped completely in the web of wrapping material Ύ.

The electromagnetic detector 5 is thus located at a position where it can perform a measurement relating to the properties of the semi-finished product“P” without interference from metallic components, if any, in the web of wrapping material Ύ because it directly faces the semi-finished product "P" before the latter has been completely wrapped.

Preferably, the electromagnetic detector is disposed above the forming beam 4, advantageously the entire detecting station 2 can be positioned above the forming beam 4 and the electromagnetic detector 5 directly faces the top surface of the semi-finished product“P”.

To allow correct movement of the semi-finished product“P” supported by the web of wrapping material Ύ, the forming station 2 comprises a conveyor belt 6 configured to move them both along a processing direction“X”.

The conveyor belt 6 has an initial stretch which receives the semi-finished product P resting on the web of wrapping material Ύ and the web of wrapping material Ύ is planar.

More specifically, the web of wrapping material Ύ and the conveyor belt 6 are both planar in the initial stretch.

In a first embodiment, shown for example in Figures 1 -4 and in Figures 7-8, the electromagnetic detector 5 is located in proximity to, or preferably at, the initial stretch.

In other words, in this embodiment, the electromagnetic detector 5 is located downstream of the feed means and upstream of the point where the web of wrapping material Ύ starts being wrapped round the semi-finished product

“P”

That means the electromagnetic detector 5 begins detecting in order to measure at least one property of the semi-finished product“P” when the web of wrapping material T is still lying flat and cannot therefore be interposed between the semi-finished product“P” and the electromagnetic detector 5.

Advantageously, the detecting station 3 comprises an opposing belt 7 disposed above the conveyor belt 6 and configured to define, in the initial stretch, a channel in which the semi-finished product "P" passes together with the web of wrapping material T, the electromagnetic detector 5 being preferably disposed on the channel.

More specifically, the opposing belt 7 and the conveyor belt 6 are configured to at least partly define, between them, the channel in which the semi finished product “P” passes, where the electromagnetic detector 5 is positioned.

This technical feature guarantees that the semi-finished product“P” is moved correctly when it crosses the zone of the forming beam 4 where the detecting station 3 is located.

Nevertheless, during detection - that is, when the semi-finished product“P” passes near the electromagnetic sensor 5 -, even the presence of the conveyor belt 6 might interfere with measurement.

Therefore, the forming station 2 might have, under the electromagnetic detector 5, a guide device 8 for guiding the conveyor belt 6 and configured to guide the conveyor belt 6 along a diversion path which deviates from the substantially straight processing direction “X” of the web of wrapping material T at least in the zone of the electromagnetic detector 5 so that, under the electromagnetic detector 5, the conveyor belt 6 is spaced from the web of wrapping material T. In an embodiment not illustrated, however, where the material or the size of the conveyor belt 6 is such as not to interfere with measurement, the conveyor belt 6 might also pass through the electromagnetic detector 5.

In other words, the forming station 2 comprises a guide device 8 which moves the conveyor belt 6 away from the web of wrapping material Ύ, hence from the semi-finished product“P” it supports, in proximity to the electromagnetic detector 5, that is, when detection is effectively carried out, so that the conveyor belt 6 cannot in any way interfere with or disturb the measuring process and allows the properties of the semi-finished product “P” to be correctly determined.

In a possible embodiment, shown by way of non-limiting example in Figures 1 and 2, the guide device 8 comprises a fixed diverter 8a configured like a spacing element interposed between the conveyor belt 6 and the web of wrapping material Ύ.

Preferably, the fixed diverter 8a is mainly planar and is oriented horizontally along the processing direction“X”.

In a possible embodiment, shown in more detail in Figures 3 and 4, the guide device 8 comprises one or more diverting rollers 8b which together define the diverting path along the processing direction“X”.

Alternatively, as shown in Figures 5 and 6, the forming station 2 has a pre forming zone where the web is wrapped only partly round the semi-finished product“P”, with the electromagnetic detector 5 being disposed at the pre forming portion.

In this case, too, the electromagnetic detector 5 is disposed in proximity to the forming beam 4, not exactly at the same position but upstream of it.

In the pre-forming zone, the web of wrapping material Ύ starts being gathered and wrapped round the semi-finished product“P”, so that it can subsequently be completely wrapped round the rod, but at the same time affords a zone in which the electromagnetic detector 5 can be efficiently applied because the semi-finished product“P” still has a freely exposed top surface that guarantees its correct interaction with the electromagnetic waves produced by the electromagnetic detector 5.

In a further possible embodiment, not shown in the accompanying drawings, the detecting station is positioned in proximity to, or at, the point where the semi-finished product“P” is transferred to the machine 1 : in other words, the electromagnetic sensor 5 is located in proximity to, or at, the feed means.

More in detail, according to this embodiment, the feed means which feed the semi-finished product“P” extend at least partly in proximity to or over the forming station 2, defining a transfer zone for transferring the semi finished product “P” to the forming station 2, where the semi-finished product“P” is above the web of wrapping material Ύ and preferably, but not necessarily, the semi-finished product“P” is already resting on the web of wrapping material Ύ.

The detecting station 3 is located at this transfer zone, in proximity to or at the feed means - for example in a zone where the semi-finished product“P” has already been transferred at least partly onto the web of wrapping material Ύ and is therefore already on top of, and preferably resting on, the web of wrapping material Ύ.

This invention also has for an object a method for making for making at least one continuous rod of the tobacco industry.

The method starts with a step of feeding a web of wrapping material Ύ and a semi-finished product “P” to a machine 1 for making at least one continuous rod of material for the tobacco industry, the machine 1 being made preferably according to what is described above.

More specifically, the web of wrapping material T and the semi-finished product“P” are fed in such a way that the latter is disposed resting on the former so that subsequent wrapping of the web of wrapping material Ύ round the semi-finished product“P” allows forming a continuous rod of material for the tobacco industry. As mentioned above, the semi-finished product“P” may be any material used in the tobacco industry as a filling for the components of a smoking article: for example, a mass of tobacco fibre, a stream of filter material, a uniform or non-uniform succession of segments of semi-finished products for making cigarettes or aerosols, for example of filter material or materials containing flavouring substances.

Next, the web of wrapping material T is wrapped round the semi-finished product“P”.

Lastly, the method comprises a step of detecting at least one property of the at least one portion of the semi-finished product “P” using an electromagnetic detector 5.

The step of detecting is carried out on the semi-finished product“P” resting on top of the web of wrapping material Ύ, upstream of the point where it is completely wrapped round the semi-finished product “P” so that the electromagnetic detector 5 faces a surface of the semi-finished product P which is not yet wrapped completely in the web of wrapping material Ύ. More specifically, the step of wrapping comprises a first sub-step of partly wrapping the web of wrapping material T round the semi-finished product “P” and a subsequent, second sub-step of completely wrapping the web of wrapping material Ύ round the semi-finished product“P”.

That way, in a first step, the semi-finished product“P” is only partly wrapped so that at least an upper portion of the semi-finished product“P”, preferably facing towards the electromagnetic detector 5 remains exposed so that it can be correctly examined, and in a second step, the wrapping process is completed and a continuous rod of semi-finished product“P” wrapped in a tube of wrapping material T is formed.

Preferably, the step of detecting is performed between the first sub-step of partly wrapping and the second step of completely wrapping.

Also, the step of feeding the semi-finished product“P” is accomplished by feed means configured to release the semi-finished product“P” onto the web of wrapping material Ύ.

In other words, the feed means are configured to carry the semi-finished product“P” to the machine 1 and then release it onto web of wrapping material Ύ.

Preferably, the step of detecting is carried out after the step of the feed means releasing the semi-finished product "P" onto the web of wrapping material Ύ, in any case when the semi-finished product“P” is already on top of the web of wrapping material T.

Advantageously, this invention achieves the preset aims, overcoming the disadvantages of the prior art, by providing the user with a machine 1 and method for making at least one continuous rod of the tobacco industry, allowing the properties of the semi-finished product“P” to be correctly and efficiently measured, irrespective of the characteristics of the specific web of wrapping material T used to make the continuous rod.

This measurement is carried out in a step of the production process in which it is possible to guarantee that the semi-finished product“P” measured is effectively the one that will make up the tobacco industry product to be made, because measurement is followed directly by the formation of the rod, without intermediate steps in which the semi-finished product“P” might undergo substantial, unwanted changes that can escape detection.

Advantageously, this invention is applicable not only to machines which make a single continuous rod but also to machines which simultaneously make a plurality of rods: for example, two rods.

This invention is applicable to different type of machines such as, by way of non-limiting example, machines for making cigarette rods, as illustrated in figures 1 to 6, and also, again by way of example, machines for making filters, as illustrated in Figure 7, or combining machines for making smoking articles or aerosol generators, as illustrated in Figure 8.

The invention solves the above mentioned prior-art drawback by providing a machine for the production of a continuous rod of the tobacco industry, capable of allowing optimum and accurate checking of the properties of the semi-finished product using an electromagnetic wave detector even when the rods made are wrapped in material which is at least partly metallized or which contains metallic parts.

This solution is, however, applicable in all production contexts and not only, for example, if the web of wrapping material has metallic or at least partly metallized portions, which interfere with the measuring process by screening or distorting the radiation and thus preventing measurements from being taken correctly through the thickness of the semi-finished product.

On the contrary, this solution is applicable even to the case where the web of wrapping material is made of paper only. In effect, the solution described herein has the advantage of checking only the semi-finished product to be wrapped, without interference caused by the wrapping materials and the materials used to close the wrapping such as, for example, vinyl glues or hot-melt glues.

Claims

1. A machine for making a continuous rod (C) of the tobacco industry, comprising a forming station (2), adapted to receive a web of wrapping material (I) from means for feeding the web of wrapping material (I) and a semi-finished product (P) of the tobacco industry from means for feeding the semi-finished product (P), wherein the station comprises a rod forming beam (4) on which the semi-finished product (P) is placed above the web of wrapping material (I) or resting on top of the web of wrapping material (I), the forming station (2) being configured to progressively wrap the web of wrapping material (I) round the semi-finished product (P) to form a continuous rod (C) of semi-finished product (P) wrapped in a tube of wrapping material;

characterized in that it comprises a detecting station (3) disposed in proximity to the rod forming beam (4) and comprising at least one electromagnetic detector (5) for detecting one or more properties of the semi-finished product (P), the electromagnetic detector (5) being disposed in proximity to a stretch of the rod forming beam (4) upstream of the point where the web of wrapping material is completely wrapped round the semi finished product (P) so that the electromagnetic detector (5) faces a surface of the semi-finished product (P) which is not yet wrapped completely in the web of wrapping material (I).

2. The machine according to claim 1 , wherein the electromagnetic detector (5) is disposed above the rod forming beam (4) and directly faces the top surface of the semi-finished product (P).

3. The machine according to claim 1 or 2, wherein the forming station (2) comprises a conveyor belt (6) configured to move the web of wrapping material (I) and the semi-finished product (P) along a processing direction (X), the conveyor belt (6) having an initial stretch which receives the semi finished product (P) and wherein the initial stretch of the web of wrapping material (I) is planar; the electromagnetic detector (5) being disposed in proximity to or at the initial stretch.

4. The machine according to claim 3, wherein the detecting station (3) comprises an opposing belt (7) disposed above the conveyor belt (6) and configured to define, in the initial stretch, a channel in which the semi finished product (P) passes together with the web of wrapping material (I), the electromagnetic detector (5) being disposed on the channel.

5. The machine according to claim 3 or 4, wherein the forming station (2) has, under the electromagnetic detector (5), a guide device (8) for guiding the conveyor belt (6) and configured to guide the conveyor belt (6) along a diversion path which deviates from the substantially straight processing direction (X) of the web of wrapping material (I) at least in the zone of the electromagnetic detector (5) so that, under the electromagnetic detector (5), the conveyor belt (6) is spaced from the web of wrapping material (I).

6. The machine according to claim 5, wherein the guide device (8) comprises a fixed diverter (8a) configured like a spacing element interposed between the conveyor belt (6) and the web of wrapping material (I), the fixed diverter (8a) being mainly planar and being oriented horizontally.

7. The machine according to claim 5, wherein the guide device (8) comprises one or more diverting rollers (8b) defining the diversion path.

8. The machine according to claim 1 or 2, wherein the forming station (2) has a pre-forming zone where the web of wrapping material (I) is wrapped only partly round the semi-finished product (P), with the electromagnetic detector (5) being disposed at the pre-forming portion.

9. The machine according to one or more of the preceding claims, wherein the electromagnetic detector (5) is a microwave detector, this electromagnetic wave detector being configured to operate between 10⁹ and 10¹³ Hz, specifically in the microwave field.

10. A method for making at least one continuous rod (C) of the tobacco industry, comprising the following steps: - feeding a web of wrapping material (I) and a semi-finished product (P), disposed above the web of wrapping material (I), to a machine (1 ) for making at least one continuous rod (C) of material for the tobacco industry, specifically a machine (1 ) according to one or more of the preceding claims; - wrapping the web of wrapping material (I) round the semi-finished product (P) to form a continuous rod (C) for the tobacco industry;

characterized in that it comprises a step of detecting, by means of an electromagnetic detector (5), at least one property of at least one portion of the semi-finished product (P), the step of detecting being carried out on the semi-finished product (P) above the web of wrapping material (I) or resting on top of the web of wrapping material (I), upstream of the point where the web of wrapping material is completely wrapped round the semi-finished product (P) so that the electromagnetic detector (5) faces a surface of the semi-finished product (P) which is not yet wrapped completely in the web of wrapping material (I).

11. The method according to claim 10, wherein the step of wrapping the web of wrapping material (I) round the semi-finished product (P) comprises a first sub-step of partly wrapping the web of wrapping material (I) round the semi-finished product (P) in such a way as to leave exposed at least an upper portion of the semi-finished product (P), and a subsequent, second sub-step of completely wrapping the web of wrapping material (I) round the semi-finished product (P), the step of detecting being carried out between the first sub-step of partly wrapping and the second sub-step of completely wrapping.

12. The method according to claim 10 or 1 1 , wherein the step of feeding the semi-finished product (P) is accomplished by feed means configured to release the semi-finished product (P) onto the web of wrapping material (I), the step of detecting being carried out after the step of the feed means releasing the semi-finished product (P) onto the web of wrapping material (I).

13. The method according to one or more of claims 10-12, wherein the semi-finished product (P) is selected from the following: a mass of tobacco fibre, a stream of filter material, a uniform or non-uniform succession of segments of semi-finished products for making cigarettes or aerosols, for example of filter material or materials containing flavouring substances.