WO2021152531A1

WO2021152531A1 - Control unit and method for controlling a group of smoking articles

Info

Publication number: WO2021152531A1
Application number: PCT/IB2021/050722
Authority: WO
Inventors: Marco FRASSON; Massimo Fortini; Giuliano Gamberini
Original assignee: G.D Societa' Per Azioni
Priority date: 2020-01-31
Filing date: 2021-01-29
Publication date: 2021-08-05
Also published as: IT202000001870A1; KR20220133276A; EP4096445A1

Abstract

A control unit (17) and method for controlling a group (2) of smoking articles (3), each comprising a portion (5) containing metal material. There are provided: a sensor (18) arranged along a path followed by the group (2) of smoking articles (3), which is electromagnetic and sensitive to the presence of the metal material contained in the portion (5) of the smoking articles (3); and a processing device (19), which is coupled to the sensor (18) and configured to establish whether, depending on the signals provided by the sensor (18), the group (2) of smoking articles (3) moving along the path has or has not all the smoking articles (3) with a same longitudinal orientation.

Description

“Control unit and method for controlling a group of smoking articles.”

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no. 102020000001870 filed on 31/01/2020., the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a unit and a method for controlling a group of smoking articles, in particular, each comprising a portion containing metal material.

PRIOR ART

A cigarette packing machine comprises a unit for forming groups of cigarettes, which receives as input a mass of cigarettes fed along a feed channel, and supplies as output a succession of orderly groups of cigarettes fed to a subsequent wrapping line.

A unit for forming groups of cigarettes (for example, as described in patent EP0764582B 1 or in patent EP1195323A1) comprises a vertical hopper, which has an upper input portion connected to the feed channel feeding the mass of cigarettes, and a lower portion provided with a plurality of output mouths. Each output mouth comprises a number of vertical tiny channels (or vertical veins), along each of which a row of cigarettes descends by gravity, and is cyclically engaged by a respective pushing element which extracts a group of cigarettes from the bottom of the hopper and feeds the group of cigarettes to a pocket of a forming conveyor that is stationary in front of the output mouth. Each pushing element is shaped like a comb and has a number of teeth which transversely cross the tiny channels of the output mouth in order to push a group of cigarettes out of the tiny channels and feed the group of cigarettes to the pocket of the forming conveyor.

Along the forming conveyor and downstream of the hopper output mouths there normally is an optical control station which acquires one or more images of the ends of all the cigarettes making up each group of cigarettes inserted in a pocket of the forming conveyor; the image of the ends of all the cigarettes is then processed both to verify the correct filling of the cigarette tips (that is, the ends of the cigarettes opposite the filter where the tobacco is “visible”) and to verify the correct longitudinal orientation of the cigarettes (i.e., to verify that all cigarettes have the same longitudinal orientation so that all tips are on the same side and, consequently, all filters are on the other side).

However, for aesthetic reasons (that is, to give the packet of cigarettes, once opened, a particular look differing from the custom), filters have recently been presented whose visible end is printed (coloured) and therefore can be confused with a tip during the above described optical control; consequently, for this type of cigarettes, the optical control is not always able to identify a failed group of cigarettes in which (at least) one cigarette has an undesired longitudinal orientation (i.e., opposite to the other cigarettes).

Patent applications US2019133178A1 and US2019261677A1 describe a device for identifying physical parameters of cylindrical articles of the tobacco industry during axial transfer thereof; the device comprises a radiation emitter, which emits radiations that pass through the articles, and a sensor, which is arranged on the opposite side of the emitter, is sensitive to the radiations, and is designed to detect the attenuation experienced by the radiations after passing through the articles.

DESCRIPTION OF THE INVENTION

It is an object of the present invention to provide a control unit and method for controlling a group of smoking articles, each comprising a portion containing metal material, which control unit and method allow the correct longitudinal orientation of the individual cigarettes in a group of cigarettes to be verified effectively and efficiently independently of the external appearance of the cigarettes (i.e., without using cameras or similar optical sensors) and are, at the same time, easy and inexpensive to produce.

In accordance with the present invention, a unit and a method are provided for controlling a group of smoking articles, each comprising a portion containing metal material, as claimed in the appended claims.

The claims describe embodiments of the present invention forming an integral part of the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting embodiments thereof, in which:

• Figure 1 is a perspective view of a rigid, hinged-lid cigarette packet housing a group of cigarettes;

• Figure 2 is a schematic view of a single cigarette contained in the packet of cigarettes of Figure 1;

• Figure 3 is a schematic front view of a packing machine which manufactures the packet of cigarettes of Figure 1 ;

• Figure 4 is a schematic perspective view of a unit of the packing machine of Figure 1 for forming groups of cigarettes;

• Figure 5 is a schematic plan view of the forming unit of Figure 4;

• Figure 6 is a schematic perspective view of a feed duct of the forming unit in Figure 4 provided with an electromagnetic inductive sensor;

• Figures 7 and 8 are plan views of a group of cigarettes in which all the cigarettes have the correct orientation and of a group of cigarettes in which one cigarette has the wrong orientation, respectively;

• Figure 9 is a graph illustrating the time course of a signal generated by the electromagnetic sensor of Figure 6 during the passage of the group of cigarettes of Figure 7 and during the passage of the group of cigarettes of Figure 8;

• Figure 10 is a schematic cross-sectional view of a forming conveyor of the forming unit of Figure 4 provided with a different type of electromagnetic sensor;

• Figures 11 and 12 are schematic, longitudinal and cross-sectional views of the forming conveyor of the forming unit of Figure 4 provided with another type of electromagnetic sensor; and

• Figure 13 is a schematic cross-sectional view of the forming conveyor of the forming unit of Figure 4 provided with a further type of electromagnetic sensor.

PREFERRED EMBODIMENTS OF THE INVENTION

Number 1 in Figure 1 indicates, as a whole, a rigid, hinged-lid cigarette packet comprising a group 2 of cigarettes 3 consisting of twenty cigarettes 3 arranged in three rows (of seven- six- seven cigarettes 3 each, respectively).

As shown in Figure 2, each cigarette 3 comprises a length of tobacco 4 wrapped in a respective tubular paper wrapping and a filter 5 which is stably connected to the length of tobacco 4 by means of a strap. Metal material is contained in the filter 5 (as for example described in patent application W02005020723A1). Alternatively, as described, for example, in patent application US4715389, the metal material could also be contained in the length of tobacco 4.

In any case, that is, whether the metal material is contained in the filter 5 or in the length of tobacco 4, this metal material may have different shapes. For example, this metal material can be granular, and therefore be dispersed in a more or less extended portion of the filter 5 or of the length of tobacco 4, or it can be a linear or reticular element of elongated, tubular or cylindrical shape, or it can be shaped as a plurality of metal elements dispersed or aligned in the filter 5 or in the length of tobacco 4.

Figure 3 shows a packing machine 7 which makes the packet 1 of cigarettes and comprises a forming unit 8 in which the groups 2 of cigarettes 3 are formed, a wrapping unit 9 in which a sheet of wrapping material is wrapped around each group 2 of cigarettes 3 to form an inner wrapping, and a wrapping unit 10 in which a blank is folded around each inner wrapping to form an outer container provided with a hinged lid, and thus complete the making of a packet 1 of cigarettes.

As shown in Figures 4 and 5, the forming unit 8 comprises a forming conveyor belt 11, which supports a plurality of pockets 12, each designed to receive and move a corresponding group 2 of cigarettes 3. The forming conveyor 11 moves stepwise to feed each pocket 12 along an annular forming path PI.

A feed station S is arranged along the forming path PI, in which four groups 2 of cigarettes 3 are simultaneously inserted (by moving along an insertion path P2 perpendicular to the forming path PI) into respective pockets 12 which are stationary. A hopper 13 is arranged in the feed station S, the former containing a mass of cigarettes 3 and having four twin output mouths 14 at the bottom, through each of which a group 2 of cigarettes 3 is extracted and inserted into a corresponding pocket 12 which is stationary in front of the output mouth 14. Each output mouth 14 is associated with a corresponding pushing element 15, which makes a linear reciprocating movement along the insertion path P2 to cyclically cross the output mouth 14 and axially push a group 2 of cigarettes 3 towards a corresponding pocket 12 which is stationary in front of the output mouth 14. As shown in Figure 5, the forming unit 11 comprises four tubular guide ducts 16, each of which is arranged in front of a corresponding output mouth 14 and guides the forward movement of a group 3 of cigarettes which, once it exits the output mouth 14 of the hopper 13, must reach a stationary pocket 12; that is, each guide duct 16 connects an output mouth 14 to a stationary pocket 12. As shown in Figure 6, each guide duct 16 has an internal passage channel having a substantially rectangular cross section which reproduces (with a small clearance) a cross section of the groups 2 of cigarettes 3; the passage channel of each guide duct 16 may also comprise ribs which reproduce the circular shape of the cigarettes.

As shown in Figure 6, the packing machine 7 comprises a (at least one) control unit 17 which allows the correct longitudinal orientation of the individual cigarettes 3 in each group 2 of cigarettes 3 to be verified effectively and efficiently independently of the external appearance of the cigarettes 3; in other words, the control unit 17 makes it possible to verify that all cigarettes 3 in each group 2 of cigarettes 3 have the same longitudinal orientation (as shown in Figure 7), that is, the control unit 17 makes it possible to verify that in each group 2 of cigarettes 3 there are no cigarettes 3 oriented longitudinally in a different way than (opposite to) the other cigarettes 3 (as shown in Figure 8).

In the embodiment shown in Figure 5, four twin control units 17 are provided, each of which is coupled to a corresponding guide duct 16 and is arranged along the corresponding insertion path P2.

As shown in Figure 6, each control unit 17 comprises a sensor 18, which is arranged in a fixed position along the insertion path P2 followed by the groups 2 of cigarettes 3, and a processing device 19, which is coupled to the sensor 18 and is configured to establish whether, depending on the signals provided by the sensor 18, the group 2 of cigarettes 3 moving along the insertion path P2 has or has not all the cigarettes 3 with a same longitudinal orientation. In each control unit 17, the sensor 18 is an electromagnetic sensor and is sensitive to the presence of the metal material contained in the cigarettes 3. In the embodiment shown in Figure 6, in each control unit 17 the processing device 19 reads the sensor 18 when a group 2 of cigarettes 3 is moving near (in proximity to) the sensor 18, that is, when the group 2 of cigarettes 3 is moving (along the insertion path P2) with respect to the sensor 18. According to an alternative embodiment, in each control unit 17 the processing device 19 reads the sensor 18 when a group 2 of cigarettes 3 is stationary near (in proximity to) the sensor 18.

Preferably and as shown in Figure 9, in each control unit 17 the processing device 19 is configured to: detect a time development x(t) of a parameter x when the sensor 18 is in proximity to a group 2 of cigarettes 3 (which may be moving or stationary with respect to the sensor 18); compare the detected time development x(t) with a sample time development corresponding to a sample group 2 of cigarettes 3 in which all the cigarettes 3 have a same longitudinal orientation; and establish whether the group 2 of cigarettes 3 has or has not all the cigarettes 3 with a same longitudinal orientation depending on the result of the comparison. In other words, if the detected time development x(t) is sufficiently similar to (i.e., not too different from) the sample development, then all the cigarettes 3 of the group 2 of cigarettes 3 have the same longitudinal orientation, whereas if the detected time development x(t) is sufficiently different from the sample development (i.e., not sufficiently similar to the sample development) at least one cigarette 3 of the group 2 of cigarettes 3 has a different longitudinal orientation (an incorrect orientation, i.e., opposite to the other cigarettes 3).

In Figure 9, the solid line shows a time development x(t) of the parameter x when the sensor 18 is close to a group 2 of cigarettes 3 in which all the cigarettes 3 of the group 2 of cigarettes 3 have the same longitudinal orientation, whereas the dashed line shows a time development x(t) of the parameter x when the sensor 18 is close to a group 2 of cigarettes 3 in which at least one cigarette 3 of the group 2 of cigarettes 3 has a different longitudinal orientation (an incorrect orientation, i.e., opposite to the other cigarettes 3). In the embodiment shown in Figure 6, each sensor 18 comprises an electric oscillator circuit 20 having at least one quantity which is influenced by a proximity to the metal material contained in the filters 5 of the cigarettes 3, and a power supply 21 which applies a variable electrical voltage to the electric oscillator circuit 20 and is connected to the processing device 19. The electric oscillator circuit 20 comprises an inductor (i.e., an electrical component that generates a magnetic field when an electric current flows therethrough); at least one quantity which is influenced by a proximity to the metal material contained in the filters 5 of the cigarettes 3 is (directly or indirectly), for example, the inductance of the inductor.

In the embodiment shown in Figure 6, in each sensor 18 the inductor consists of a single coil 22 (that is, the electric oscillator circuit 20 comprises a single coil 22), which is directly (galvanically) connected to the power supply 21 and is arranged in a fixed position along the corresponding insertion path P2. In particular, each coil 22 is wound around the corresponding guide duct 16, and thus around the corresponding insertion path P2, so that a group 2 of cigarettes 3 moving along the guide duct 16 and therefore along the insertion path P2 passes inside the coil 22 (that is, it longitudinally crosses the coil). Preferably, each sensor 18 (or each coil 22) is arranged around the corresponding guide duct 16 in the vicinity of the end facing the forming conveyor 11 (and therefore opposite to the end facing the hopper 13); in this way, each sensor 18 (or the coil 22) is arranged in an area of the guide duct 16 which is travelled by the group 2 of cigarettes 3 at a slower forward speed (when the pushing element 15 reaches the end of the guide duct 16 facing the forming conveyor 11, its speed drops to zero and its direction of motion is reverted). It is understood that each sensor 18 (that is, the coil 22) can be arranged in any area of the duct 16.

In this embodiment, the presence and position of the metal material inside each coil 22 (i.e., inside each inductor) is “sensed” by the power supply 21, for example, as a change in the inductance (which involves a consequent change in the reactance, or impedance), a change in the merit factor or a change in the resonance frequency. Accordingly, the parameter x of which the time development x(t) is detected (shown in Figure 9) can be, for example, the inductance of the electric oscillator circuit 20 or the merit factor of the electric oscillator circuit 20.

In the embodiment shown in Figure 6, the coils 22 of the various sensors 18 could influence each other, thus distorting the readings; in order to avoid this drawback, it is possible to differentiate the working frequencies of the electric oscillator circuits 20 of the various sensors 18 (especially of the adjacent electric oscillator circuits 20); that is, the electric oscillator circuits 20 of the various sensors 18 have oscillation frequencies that are different from each other. The embodiment shown in Figure 6 has an extreme reading speed, is only sensitive to the presence of the metal material (that is, it is not affected in any way by the other components of the cigarettes such as tobacco, filters, paper etc.), and is also capable of operating when the metal material is not magnetic (i.e., not ferromagnetic).

In the embodiment shown in Figure 10, a single control unit 17 is provided, which is coupled to the forming conveyor 11 and arranged along the forming path PI (instead of four control units 17 coupled to the respective guide ducts 16).

In the embodiment shown in Figure 10, the electric oscillator circuit 20 of the sensor 18 comprises a plurality of coils 23, each of which is galvanically separated from and independent of the power supply 21, is wound around a corresponding pocket 12 which moves the group 2 of cigarettes 3 along the forming path PI, and is preferably short- circuited by a capacitor 24 (so as to form a resonant L/C circuit); furthermore, the electric oscillator circuit 20 of the sensor 18 comprises a single coil 25, which is directly (galvanically) connected to the power supply 21 and arranged in a fixed position along the forming path PI, so as to be electromagnetically coupled to each coil 23 when the corresponding pocket 12 passes near the coil 25.

In this embodiment too, the presence and position of the metal material inside each coil 23 (i.e., inside each inductor) is “sensed” by the power supply 21, for example, as a change in the inductance (which involves a consequent change in the reactance, or impedance) a change in the merit factor or a change in the resonance frequency. Accordingly, the parameter x of which the time development x(t) is detected can be, for example, the inductance of the electric oscillator circuit 20 or the merit factor of the electric oscillator circuit 20. From a practical point of view, the power supply 21 can generate in the coil 25 an electric oscillator signal (even of the impulsive type and which therefore tends to be naturally dampened in time), which undergoes variations (in terms of amplitude, duration, slope, frequency) due to the presence of the metal material carried by the cigarettes 3 inside the coil 23.

In other words, in the embodiment shown in Figure 10, each coil 23 is part of a movable resonant circuit carried by a corresponding pocket 12, whereas the coil 25 is part of an excitation and measurement circuit arranged in a fixed position, for example, alongside the forming conveyor 11.

In the embodiment shown in Figures 11 and 12, a single control unit 17 is provided, which is coupled to the forming conveyor 11 and arranged along the forming path PI (as in the embodiment shown in Figure 10); in this embodiment, the sensor 18 comprises a magnet 26 (permanent or equipped with an excitable solenoid) arranged in a fixed position on one side of the forming path PI (i.e., on one side of the forming conveyor 11) to generate a static magnetic field, and an array of elements 27 sensitive to the magnetic field (magneto resistors, GMRs,...), which are arranged in a fixed position on the opposite side of the forming path PI (i.e., on the opposite side of the forming conveyor 11) and are connected to the processing device 19.

In use, the array of sensitive elements 27 is capable of detecting a change in the intensity of the static magnetic field generated by the magnet 26 due to the presence and position of the metal elements 6 in the cigarettes 3 of the group 2 of cigarettes 3.

As an alternative to what is shown in Figures 11 and 12, the control unit 17 can be arranged in a fixed position along the insertion path P2. Preferably, the magnet 26 and the array of sensitive elements 27 are arranged on opposite sides of the guide duct 16 in the vicinity of the end facing the forming conveyor 11. In this embodiment, the group 2 of cigarettes 3 longitudinally crosses the array of sensitive elements 27, that is, the array of sensitive elements 27 is arranged orthogonal to the forward movement of the group 2 of cigarettes.

In the embodiment shown in Figure 13, a single control unit 17 is provided, which is coupled to the forming conveyor 11 and arranged along the forming path PI (as in the embodiment shown in Figure 10); in this embodiment, the sensor 18 comprises a resonating cavity 28, which is arranged along the forming path PI (i.e., along the forming conveyor 11) to be crossed by the group 2 of cigarettes 3, and a microwave emitter/receiver 29, which is designed to emit and receive microwaves inside the resonating cavity 28 and is connected to the processing device 19.

It should be noted that, if the group 2 of cigarettes crosses the sensor 18 longitudinally, preferably this sensor 18 (i.e., the coil 22) has a smaller width than the length of the portion 5 containing the metal material. In other words, with reference to Figure 6, the coil 22 has a width (that is, an extension in the direction parallel to the insertion path P2) smaller than the length of the filter 5.

It should be noted that, if the group 2 of cigarettes crosses the sensor 18 transversely (Figure 13) or passes near the sensor 18 with a transverse movement (Figure 10 or 11), or if the measurement is static, then the sensor 18 is positioned in the area of the group 2 of cigarettes where no metal material should be contained.

In the embodiments shown herein, the control unit 17 is coupled to the forming unit 8 to control the groups 2 of cigarettes 3 before starting the wrapping of the wrapping materials and thus to be able to discard the defective groups 2 of cigarettes 3 before starting the wrapping of the wrapping materials. According to other embodiments, not shown, the control unit 17 is coupled to the wrapping unit 9, to the wrapping unit 10, or to an output conveyor arranged downstream of the wrapping unit 10; in this case, the groups 2 of cigarettes 3 are checked after the wrapping of at least part of the wrapping materials, and thus the semi-finished or finished packets 1 of cigarettes containing defective groups 2 of cigarettes 3 are discarded.

In the embodiment shown in the accompanying drawings, each cigarette 3 comprises (at least) metal material dispersed in the filter 5, which has the function of increasing the filtering capacity (as described, for example, in patent application W02005020723A1). According to a different, equivalent embodiment, each cigarette 3 comprises an (at least one) annular metal element, which is arranged on the outer surface of the strap connecting the filter 5 to the length of tobacco 4 (which is therefore in sight, i.e., visible from the outside) and has an aesthetic function; this annular metal element could be laminated on the paper band from which the connection straps are formed or could be printed (typically by jet printing technology) on the paper band from which the connection straps are formed.

According to a further, equivalent embodiment, each cigarette 2 comprises a (at least one) metal element which, instead of being arranged inside the filter 5, is arranged inside the length of tobacco 4 (as for example described in patent US4715389A).

In all the possible embodiments described above (which can also optionally be combined together), the cigarette 3 comprises a (at least one) portion containing metal material arranged asymmetrically with respect to a longitudinal center line of the cigarette 3.

In the embodiment shown in the accompanying drawings, the group 2 comprises conventional cigarettes 3, therefore each provided with a length of tobacco 4 intended for combustion and a filter 5. Alternatively, the group 2 may comprise cigarettes 3 in which the filter 5 and/or the length of tobacco 4 is of the multi-segment type; in this case, the metal material may be contained in one or more segments of the filter 5 and/or of the length of tobacco 4.

The embodiments described herein may be combined with each other without departing from the scope of protection of the present invention.

The control unit 17 described above has many advantages.

Firstly, the control unit 17 described above allows the correct longitudinal orientation of the individual cigarettes 3 in a group 2 of cigarettes 3 to be verified effectively and efficiently, independently of the external appearance of the cigarettes 3 (i.e., without using cameras or similar optical sensors).

Moreover, the control unit 17 described above is fast enough to operate correctly even in a fast packing machine 7 (for example, capable of producing 800-1,000 packets 1 of cigarettes per minute); that is, the control unit 17 described above is able to verify in (much) less than one hundredth of a second the correct longitudinal orientation of the individual cigarettes 3 in a group 2 of cigarettes 3 even when the group 2 of cigarettes 3 is moving (rapidly).

The control unit 17 described above is particularly compact and therefore can also be installed in an existing packing machine 7 without undue difficulty.

Finally, the control unit 17 described above is particularly simple and inexpensive to manufacture, since it uses structurally simple and inexpensive components (coils, magnets, capacitors, small electronic circuits).

Claims

C L A I M S

1) A control unit (17) configured to control a group (2) of smoking articles (3), each comprising a portion (5) containing metal material; the control unit (17) comprises: a sensor (18), which is arranged along a path followed by the group (2) of smoking articles (3); and a processing device (19), which is coupled to the sensor (18) and is configured to establish whether, depending on the signals provided by the sensor (18), the group (2) of smoking articles (3) moving along the path has or has not all the smoking articles (3) with a same longitudinal orientation; the control unit (17) is characterized in that the sensor (18) is an electromagnetic sensor and is sensitive to the presence of the metal material contained in the portion (5) of the smoking articles (3).

2) The control unit (17) according to claim 1, wherein the processing device (19) reads the sensor (18) when the group (2) of smoking articles (3) is moving in the area of the sensor (18).

3) The control unit (17) according to claim 1, wherein the processing device (19) reads the sensor (18) when the group (2) of smoking articles (3) is standing still in the area of the sensor (18).

4) The control unit (17) according to claim 1, 2 or 3, wherein the processing device (19) is configured to: detect a time development of a parameter (x) when the sensor (18) is in proximity to the group (2) of smoking articles (3); compare the detected time development with a sample time development corresponding to a sample group (2) of smoking articles (3), in which all the smoking articles (3) have a same longitudinal orientation; and establish whether the group (2) of smoking articles (3) has or has not all the smoking articles (3) with a same longitudinal orientation depending on the result of the comparison.

5) The control unit (17) according to any one of the claims from 1 to 4, wherein the sensor (18) comprises: an electric oscillator circuit (20) having at least one quantity, in particular an inductance, which is influenced by a proximity with the metal material contained in the portion (5) of the smoking articles (3); and a power supply (21), which applies an electric voltage, in particular an AC voltage, to the electric oscillator circuit (20) and is connected to the processing device (19).

6) The control unit (17) according to claim 5, wherein the electric oscillator circuit (20) comprises one single coil (22), which is connected to the power supply (21) and is arranged in a fixed position along the path.

7) The control unit (17) according to claim 6, wherein the coil (22) is wound around the path so that the group (2) of smoking articles (3) moving along the path longitudinally passes inside the coil (22).

8) The control unit (17) according to claim 5, 6 or 7, wherein: there are a plurality of electric oscillator circuits (20) arranged along respective paths followed by corresponding groups (2) of smoking articles (3); and said plurality of electric oscillator circuits (20) have different work frequencies.

9) The control unit (17) according to claim 5, wherein the electric oscillator circuit (20) comprises: a first coil (23), which is galvanically separated from and independent of the power supply (21) and is wound around a pocket (12) moving the group (2) of smoking articles (3) along the path; and a second coil (25), which is connected to the power supply (21) and is arranged in a fixed position along the path so as to be electromagnetically coupled to the first coil (23).

10) The control unit (17) according to any one of the claims from 1 to 4, wherein the sensor (18) comprises: a magnet (26), which is arranged in a fixed position on one side of the path; and a series of elements (26) sensitive to the magnetic field, which are arranged in a fixed position on the opposite side of the path and are connected to the processing device (19).

11) The control unit (17) according to any one of the claims from 1 to 4, wherein the sensor (18) comprises: a resonating cavity (28), which is arranged along the path so as to be crossed by the group (2) of smoking articles (3); and a microwave emitter/receiver (29), which is designed to emit/receive microwaves inside the resonating cavity (28) and is connected to the processing device (19).

12) A packing machine to manufacture a pack of cigarettes around a group (2) of smoking articles (3), each comprising a portion (5) containing metal material; the packing machine comprises: conveyor means, which move the group (2) of smoking articles (3) along a path; and a control unit (17), which is coupled to the conveyor and is manufactured according to any one of the claims from 1 to 11.

13) The packing machine according to claim 12 and comprising: a forming conveyor belt (11), which supports a plurality of pockets (12), each designed to receive and move a corresponding group (2) of smoking articles (3) along a forming path (PI); a hopper (13), which contains a mass of smoking articles (3) and has, at the bottom, at least one output mouth (14); at least one pushing element (15), which makes a linear reciprocating movement along an insertion path (P2) and is designed to cyclically cross the output mouth (14) so as to extract a group (2) of smoking articles (3) from the output mouth (14) and insert the group (2) of smoking articles (3) into a corresponding pocket (12) standing still; and a tubular guide duct (16), which is arranged along the insertion path (P2) between the output mouth (14) and the forming conveyor (11); wherein the control unit (17) is coupled to the guide duct (16) and is arranged along the insertion path (P2).

14) The packing machine according to claim 13, wherein the sensor (18) of the control unit (17) is arranged around the guide duct (16) in the area of an end facing the forming conveyor (11).

15) The packing machine according to claim 12 and comprising: a forming conveyor belt (11), which supports a plurality of pockets (12), each designed to receive and move a corresponding group (2) of smoking articles (3) along a forming path (PI); a hopper (13), which contains a mass of smoking articles (3) and has, at the bottom, at least one output mouth (14); and at least one pushing element (15), which makes a linear reciprocating movement along an insertion path (P2) and is designed to cyclically cross the output mouth (14) so as to extract a group (2) of smoking articles (3) from the output mouth (14) and insert the group (2) of smoking articles (3) into a corresponding pocket (12) standing still; wherein the control unit (17) is coupled to the forming conveyor (11) and is arranged along the forming path (PI). 16) A control method to control a group (2) of smoking articles (3), each comprising a portion (5) containing metal material; the control method comprises the steps of: moving the group (2) of smoking articles (3) along a path; and establishing, by means of a processing device (19) coupled to a sensor (18) arranged along the path and depending on the signals provided by the sensor (18), whether the group (2) of smoking articles (3) moving along the path has or has not all the smoking articles (3) with a same longitudinal orientation; the control method is characterized in that it comprises the step of detecting the presence of the metal material contained in the portion (5) of the smoking articles (3) by means of an electromagnetic sensor (18).