BACKGROUND OF THE INVENTION

The present invention relates to an apparatus and a method for making a continuous rod of fibrous material in a tobacco industry machine.

In particular, the present invention relates to making a rod containing fibrous material, such as tobacco fibres or fibres of filtering material or a plurality of filtering elements that are different from one another, each containing fibres of filtering material, to which the following discussion makes explicit reference without loss of generality.

PRIOR ART

In order to make a continuous rod of fibrous material in the tobacco industry, supplying a continuous web of material is known, for example paper web material, to a forming beam that wraps the continuous web around a fibrous material deposited thereupon.

The term "fibrous material" refers to fibres of filtering material (for example cellulose acetate or a combination of cellulose acetate and different components for making combined filters) intended for forming a continuous, single or double-line, filter rod in a machine, for producing smoke articles such as cigarette filters; alternatively "fibrous material" refers to the fibres of tobacco intended for forming a rod of tobacco in a machine, or in a single or double line, for producing smoke articles such as cigarettes. In particular, the continuous web is supplied to a forming apparatus, in particular the continuous web is supplied along a determined path P in an advancement direction D in contact with a belt conveyor to a forming beam, through a loading station at which the web receives the fibrous material deposited centrally thereupon. The forming beam comprises folding means, namely a variable section groove, in which the belt conveyor and the continuous web engage to deform transversely, thus progressively wrapping the fibrous material and making a tubular wrapper.

A ribbon of adhesive material is arranged parallel to an end border of the continuous web on an inner surface of the latter to be placed in contact with an outer surface of the tubular wrapper at the forming beam and, when stabilised, make the continuous rod.

At the high operating speeds of cutting machines of the tobacco industry, reduced time to stabilise the glued tubular wrapper is increasingly requested. For this reason, thermofusible adhesive material of the ribbon is being increasingly used, as it is sufficient to cool the glued portion to make gluing rapidly permanent, thus stabilising the glued tubular wrapper. The term thermofusible adhesive material or heat activated adhesive or also hot melt adhesive is defined as a polymeric material that is active when it is in melted state and performs its gluing action during cooling from melted state. If the polymeric material is not in melted state it is devoid of adhesive properties, but can be thermally reactivated if it is brought to melting temperature.

The hot melt material is applied hot to the surface of the continuous web through a glue- applying nozzle that creates a ribbon of glue. Subsequently, thermal energy is supplied to the ribbon to maintain the glue in melted state until the moment of wrapping in the forming beam, also being able to be very long the supply path of the continuous web because of internal geometries linked to the structure of the forming apparatus from the position of applying the ribbon of glue to the position of wrapping in the forming beam, in which the web is brought into contact with the outer surface of the tubular wrapper.

For example, the hot melt material is applied to the continuous web at a temperature comprised in a range between 160° and 200° and has to be maintained at a melting temperature of around 110°, which is variable in relation to the type of hot melt adhesive used, to perform an adhesive action.

Applying the adhesive ribbon of hot melt adhesive and the thermal treatment thereof to maintain the ribbon in a melted state nevertheless causes problems.

Heating plates are in fact necessary that are arranged along the path P upstream of the loading station of the fibrous material, which are suitable for contacting the surface of the web opposite the surface to which the glue is applied to maintain the ribbon in melted state (the so-called pre-heating plates). Further, the forming beam has to be provided with both heated folding means, arranged upstream of the wrapping position to maintain in melted state the ribbon of adhesive material before wrapping, and cooled bars, arranged downstream of the wrapping position to remove heat from the ribbon of adhesive material in contact with the tubular wrapper and thus stabilise the rod of fibrous material.

Nevertheless, the presence of the heating plates and of heated folding means in the forming beam does not guarantee that the adhesive material of the ribbon has reached the desired melting temperature at the moment of wrapping in the forming beam.

For example, to make a rod of material containing multi-component filtering elements in which several types of filtering material are different from one another, a material of great thickness is used that is in a continuous web, in particular a card that is a few tenths of a millimetre thick.

To maintain in melted state the ribbon of adhesive material applied to the card, a very high temperature of the heating plates is necessary so that heat reaches the glue through the card and maintains the glue melted. At the same time, however, it is not possible to increase this temperature too much as the card could be damaged by an excess temperature. As a result, at the maximum temperature to which the heating plates can be heated without damaging the card, a film of unmelted adhesive material can form in the outer surface layer of the ribbon that has not been reached by the heat, which does not permit ideal gluing.

It is added that, working at very high temperatures, the cooled bars of the forming beam might not be able to stabilise effectively the adhesive material downstream of the wrapping position inasmuch as it could be necessary to remove in a short time a quantity of heat that is too high.

The tubular enclosure might in other words not close, either because the glue of the ribbon did not melt in an optimum manner during wrapping or because the glue of the ribbon is not cooled sufficiently downstream of the wrapping position in the forming beam.

In order to overcome this problem, it was proposed to increase the quantity of glue in the ribbon to increase the thermal inertia of the ribbon and make the external film of the ribbon, if present, non-influential for the purposes of gluing.

Nevertheless, by increasing the quantity of glue there is the danger that this will dirty the mechanical components of the forming apparatus, despite the presence of sucking means to retain in position the continuous web during the supply path thereof when the glue is activated. In fact, the sucking means might not be effective if the web is a card of great thickness.

It is added that controlling the temperature of the glue and of perfect gluing is practically impossible both during switch-on and during operation of the forming apparatus, which can entail both long periods of operation without stops and frequent stops and short periods of operation.

When the machine for making smoke articles is switched on, during an initial transition of the forming apparatus in which the heating plates have not yet reached a preset work temperature, if the speed of the machine is high and then the tubular enclosure then remains briefly in contact with the heating plates, the heating of the glue ribbon is insufficient to maintain the adhesive material melted in an optimum manner and thus the tubular enclosure cannot close.

The thermal inertia of the heating mechanical elements further causes undesired heating, if, for example, the apparatus has to stop and the heating plates are active, or insufficient heating, when the apparatus is restarting after a stop the heating plates, which had cooled during the stop, are thus still cold.

It is added to this that when the web of continuous material slides for a long time in contact with the heating plates, heat is generated that is due to the friction that increases in an uncontrolled manner the temperature of the heating plates. For this purpose, blown air cooling means is provided that acts on the heating plates, which are driven if the forming apparatus operates for a long time without stops, which makes the forming apparatus all the more complicated and costly.

GB 1378169 discloses an alternative method for heating hot melt adhesive found in a web of wrapper material for filters.

GB 1378169 shows forming means of a continuous rod of filters comprising a forming belt that is suitable for guiding a web of wrapper material for filters supplied by a reel. The web has three strips of hot-melt adhesive, applied preliminarily to the web. In order to activate the hot-melt adhesive, by heating the hot-melt adhesive, a source of heat is provided in the form of an infrared heater with radiant energy arranged behind a parabolic mirror arranged above a supply path of the web of wrapper material.

Also with the method proposed by GB 1378169 it is necessary to work at very high temperatures because the radiant energy of the infrared waves heats an entire portion of web with which it comes into contact. Also in this case the cooled bars of the forming beam might not be able to stabilise effectively the adhesive material downstream of the wrapping position, having to remove too great an amount of heat in a short period.

DESCRIPTION OF THE INVENTION

One object of the present invention is to provide an apparatus and a method of making a rod of fibrous material that is free of the drawbacks disclosed above and which is, at the same time, easy and cheap to make.

Another object of the present invention is to provide apparatus and a method for making a rod of fibrous material that permits optimum heating of the thermofusible glue ribbon, also using web material of great thickness and without risk of damage the web material itself. A further object is to use the minimum quantity of glue necessary for gluing, whilst ensuring effective gluing.

Another further object is to control effectively the heating temperature of the glue in any operating condition of the forming apparatus and at any operating speed of the machine for making smoke articles.

According to the present invention an apparatus and a method are provided for making a rod of fibrous material, according to what is claimed in the appended claims.

SHORT DESCRIPTION OF THE DRAWINGS

The present invention will now be disclosed with reference to the attached drawings that illustrate some non-limiting embodiments thereof by way of non-limiting example, in which:

- figure 1 is a schematic view of a forming apparatus of a rod of tobacco made in accordance with the present invention, in which there is a forming beam for wrapping a rod of fibrous material from a continuous web;

- figure 2 is a schematic side view of a portion of the forming beam of figure 1, with which three schematic sections are associated in the section planes indicated, in particular at a wrapping position and upstream of this position;

- figure 3 is a schematic view of a portion of the continuous web provided with a ribbon of adhesive material with which a schematic side view is associated of a source of radiant energy that heats the ribbon;

- figure 4 is a schematic view of a portion of the continuous web provided with a ribbon of adhesive material with which a schematic side view is associated of one source of radiant energy, in which different forms of emission of light beams are shown;

- figure 5 is a graph that shows on the y axis an absorption spectrum of the ribbon of adhesive material and an absorption spectrum of the continuous web as a function of the wavelength of the luminous radiation with which they are hit.

PREFERRED EMBODIMENTS OF THE INVENTION

In this description, identical elements that are common to the illustrated embodiments are indicated by the same numbering.

According to what is illustrated in figures 1 and 2, with 1 there is illustrated an apparatus for making a continuous rod 2 of fibrous material 100, for example containing tobacco fibres or fibres of filtering material, in a tobacco industry machine. The definition "fibrous material" has been provided previously and will not be repeated here for the sake of brevity.

The continuous rod 2 of fibrous material is obtainable starting from a continuous web 3. The apparatus 1 in fact comprises supplying means of known type which is arranged for supplying longitudinally a continuous web 3, the width of which is slightly greater than the circumference of the continuous rod 2 to be produced, along a determined path P in an advancement direction D. The continuous web 3 is provided with a ribbon 4 of thermofusible adhesive material (figures 2 and 4) arranged parallel to an end border 3 a of the continuous web 3. The ribbon 4 of adhesive material is applied to the continuous web 3, as will be specified better below.

The supplying means comprises a plurality of rollers 5, in particular cylindrical rollers, rotating around respective rotation axes 5 a which are substantially parallel to one another and in particular are perpendicular to the sheet plane of figure 1. The rotation axes 5a of the rollers 5 are usually horizontal. As known, the continuous web 3 is supplied in contact with belt conveying means (which are not illustrated) driven by motor means (which is not illustrated) such that an outer surface of the continuous web 3 comes into contact with a conveying branch of the conveying means, which is suitable for advancing the continuous web 3 along the path P around the rollers 5.

Along the path P, a loading station 6 is provided that is arranged above the continuous web 3 for transferring the fibrous material 100 to the continuous web 3, in particular to an inner surface of the continuous web 3. The fibrous material 100, once it is deposited centrally on the continuous web 3, leaves two side strips of the inner surface of the continuous web free, as will be seen better below.

The forming apparatus 1 comprises a forming beam 7, arranged in particular horizontally, extending downstream of the loading station 6 along the path P in the advancement direction D, for wrapping the continuous web 3 around the fibrous material 100 at a wrapping position 8, arranged in an intermediate position in the forming beam 7, and thus obtaining the continuous rod 2.

The forming beam 7 comprises an upper variable section groove which is in particular of curved shape and with a curvature radius that is variable in relation to the distance from the loading station 6.

Near the loading station 6, upstream of the wrapping position 8 and near a first deformation position 9, the forming beam 7 is "U" shaped, to deform transversely the continuous web 3 above which the fibrous material 100 is present. A first side appendage 10 and a second side appendage 11 of continuous web 3, that face one another and correspond to the side strips of continuous web left free by the fibrous material 100 at the moment of transfer thereof, emerge from the groove in the forming beam. One of the side appendages, in particular the side appendage 10 as shown in figure 2, is provided with the ribbon 4 of adhesive material.

At a second deformation position 12, arranged downstream of the first deformation position 9 (thus more different from the loading station 6) but upstream of the wrapping position 8, the forming beam 7 has first folding means 13, which has an inner semicylindrical profile with a curvature radius that is the same as that of the rod 2 to be formed, for deforming further the continuous web and folding the side appendage 11 on the fibrous material 100. The first side appendage 10 with the ribbon 4 of adhesive material emerges from the forming beam 7.

The forming apparatus 10 further comprises heating means 14 of the ribbon 4 of adhesive material, which is suitable for heating the adhesive material upstream of the wrapping position 8. The heating means 14 is arranged at the second deformation position 12.

At the wrapping position 8, the forming beam 7 has an inner semicylindrical profile with a curvature radius that is the same as that of the rod 2 to be formed and has further second folding means 15 for wrapping the first side appendage 10 the ribbon 4 of which has been heated previously on the already partially formed rod 2.

Following the transverse deformation due to the first folding means 13 and to the second folding means 15, the continuous web 3 is wrapped completely around the fibrous material 100 at the wrapping position 8.

The heating means 14 comprises at least a source of radiant energy, which is arranged for directing said radiant energy to the ribbon 4 so as to hit directly the ribbon 4 to heat the ribbon 4.

The source 14 of radiant energy is suitable for emitting one light beam 16 of a wavelength that is such that the ribbon 4 is able to absorb such radiant energy, heating up, whilst the web of continuous material 3 reflects this energy. In figure 5 a graph is shown that shows a first absorption spectrum 17 of the ribbon of adhesive material 4 and a second absorption spectrum 18 of the continuous web 3 as a function of the wavelength of the luminous radiation with which the adhesive material of the ribbon 4 and the continuous web 3 are respectively hit. On the y axis the absorption A is shown, which expresses the fraction of light impacting on a given wavelength that is absorbed by a sample, in the specific case the fraction of impacting light that is absorbed by the ribbon 4 of adhesive material or by the continuous web 3 and causes the heating thereof.

Experimentally, it has been observed that if the wavelength of the light beam is comprised in a range between 800 to 3000nm, in particular preferably comprised between 800 and 1 lOOnm, the ribbon 4 of adhesive material absorbs the impacting luminous energy whereas on the other hand the continuous web 3 of paper reflects the impacting luminous energy. In other words, the impacting light beam 16, the wavelength λ of which is comprised between 800nm and 3000nm, which is directed to the ribbon 4 to hit the ribbon, does not damage the continuous paper web to which the ribbon 4 of adhesive material is applied inasmuch as the radiant energy is reflected.

According to a preferred embodiment of the present invention, the source of radiant energy 14 comprises one source laser that is suitable for emitting one collimated light beam which is arranged for hitting substantially exclusively said ribbon.

Alternatively, according to one version that is not illustrated, the source of radiant energy 14 can comprise at least a lamp, which is associated with a set of focusing lenses, that is suitable for emitting one focused light beam which is arranged for hitting substantially exclusively said ribbon.

Typically, the source of radiant energy that is suitable for emitting a luminous radiation wavelength λ comprised between 800nm and 3000nm is an Nd/YAG laser, i.e. a solid state laser that exploits a neodymium-doped (Nd:Y3A15012) yttrium aluminium garnet (YAG). The first absorption spectrum 17 shown in figure 5 has been obtained by hitting the ribbon 4 by means of one source of Nd/Y AG radiant energy.

In order to modify the wavelength λ at which the adhesive material of the ribbon 4 absorbs the radiant energy, it is possible to add additives to the adhesive material itself.

The second absorption spectrum 18 shows how the continuous web absorbs the maximum amount of energy when the continuous web is hit with a source of radiant energy that is suitable for emitting wavelength λ luminous radiation comprised between 9200nm and 10600nm. These wavelength ranges are typically used for making perforations in the continuous web 3, when required, in the tobacco industry machine. The second absorption spectrum 18 shown in figure 5 has been obtained by hitting the continuous web 4 by a source of radiant energy of C0 ₂ laser type.

According to what is illustrated in figure 2, the source of radiant energy 14 is arranged facing the ribbon 4.

According to one version that is not illustrated, the source of radiant energy 14 does not face the ribbon 4 but it is still possible to direct the radiant energy to the ribbon 4 by means of deflecting means (which are not illustrated), for example mirrors, of the light beam 16. The source of radiant energy 14, whether obtainable from a source laser or from a lamp, is activatable for emitting a continuous light beam 16 or is activatable for emitting a pulsed light beam at a given frequency, each pulse being emitted for a given period of time, depending on the adhesive material to be heated and/or according to the operating speed of the machine.

The sources of radiant energy can in fact act as a continuous and as a pulsed wave. In the latter mode, if the source of radiant energy is of laser type, every single pulse can be of very high power, optical output power, for example, even of 6 megawatt and impulse durations of less than 10 nanoseconds can be achieved.

In this manner, as for example shown in figure 4, the source of radiant energy 14 is activatable for emitting luminous spots of different shape, in particular a spot of circular shape 19, a succession of circular sports 20, a spot of elliptic shape 21 or a spot of rectangular shape 22, in the latter case if for example the source of radiant energy is activated continuously for a given period of time.

By varying the emission frequency of the pulses and/or the duration thereof, the overall optical emission power can be varied in relation to the operating needs of the forming apparatus, as will be seen better below. Alternatively, or in addition, the emission power of every single light pulse can be varied.

It is noted that the emission light pulse 16, whether emitted collimated by a source 14 of laser type or emitted by a lamp and subsequently focused by the set of focusing lenses, is suitably dimensioned, i.e. of a dimension that is such that the spot that hits the ribbon 4 of adhesive material is substantially of the same dimensions as the ribbon 4, as shown in figure 4. Nevertheless, if also the luminous spot were of a greater dimension than the ribbon 4, the continuous web 3 would not be damaged by reflecting the luminous radiation with which it would be hit.

As can be seen in figure 1, the source of radiant energy 14 can be positioned at several points of the forming apparatus 1 or there can be several sources of radiant energy 14 repeated along the path P.

The source of radiant energy 14 can be positioned upstream of the forming beam, for example at a straight portion of the path P or also at a roller 5.

Alternatively, this source 14 can be arranged at the forming beam upstream of the wrapping position 8.

The forming apparatus can comprise, as shown in figure 1, a glue-applying device 23 for applying the ribbon 4 of adhesive material in the continuous web. In this case, if arranged in a straight portion of the path P before the loading station 6, the source of radiant energy 14 would have a pre-heating function to maintain the ribbon 4 at the desired temperature. The emission power necessary to heat the ribbon 4, which would already be hot because it had just been applied by the glue-applying device 23, would be minimal. If on the other hand the source of radiant energy 14 were arranged further from the glue-applying device 23, for example at the forming beam 7, the required optical emission power would be greater.

The forming apparatus 1 can alternatively be devoid of the glue-applying device and be supplied by a reel (not shown) of continuous web 3, in which the ribbon 4 of adhesive material is present, in as much as applied previously, but is in an inactive state. In the inactive state, the adhesive material is devoid of adhesive properties and is not sticky. The ribbon 4 thus has to be reactivated thermally by the radiant energy emitted by the source 14, which has to have one power emission source that is sufficiently high to return the adhesive material of the ribbon 4 to the melted state. Alternatively, several sources of radiant energy 14 can be present along the path P to heat the ribbon 4 in two different positions and with increasing power.

The forming apparatus comprises control means, which are not illustrated, for managing the operation of the forming apparatus 1, to check the emission power of the source of radiant energy 14 (or alternatively to synchronise between themselves the plurality of sources of radiant energy 14 that may be present) and to control the frequency and duration of activation of the light beam 16.

Optionally, the forming apparatus 1 can comprise a pyrometer, which is not shown, arranged along the advancement path P, to read the temperature of the adhesive material of the ribbon 4 downstream of the source of radiant energy 14. The control means, if the pyrometer is present, can acquire the temperature T of the ribbon 4 of adhesive material downstream of the source of radiant energy 14 and can thus control the emission of the light beam 16 (duration and/or frequency of the pulse and/or emission power) accordingly on the basis of the acquired temperature T, for optimum heating of the ribbon.

In use, to make a continuous rod 2 of fibrous material in a tobacco industry machine, the method comprises the following steps: supplying a continuous web 3, in which a ribbon 4 of thermofusible adhesive material is present, to a forming beam 7 along a determined path P that extends in an advancement direction D through a loading station 6; transferring the fibrous material to the continuous web 3 at the loading station 6 and wrapping by means of the forming beam 7 the continuous web 3 at a wrapping position 8 to obtain the continuous rod 2. The method further provides heating the ribbon 4 of adhesive material upstream of the wrapping position 8, to maintain the adhesive material in melted state. The step of heating the ribbon 4 provides for emitting radiant energy and directing the radiant energy to the ribbon 4 so as to hit directly the ribbon 4 to heat the ribbon 4.

The step of emitting radiant energy comprises emitting at least a light beam 16 that is collimated (because emitted by a laser source) or focused (because emitted by a lamp associated with a system of lenses), of a wavelength that is such that the ribbon 4 is able to absorb such radiant energy by getting heated whilst the web of continuous material 3 reflects this energy. The light beam 16 hits substantially exclusively the ribbon 4.

A continuous light beam 16 or a pulsed light beam of a given frequency is emitted and each pulse of a given duration, in relation to the adhesive material to be heated and/or to the operating speed of the forming apparatus 1.

For example, if the operating speed is slow it may be possible to emit a light beam 16 of medium power for a long time and for example the luminous spot can be of an elongated elliptic shape 21 or be of rectangular shape 22. On the other hand, if the operating speed is high, a high power light beam has to be emitted to heat the adhesive material in a short time and thus it can be possible to emit a circular spot 19 or a sequence of circular spots 20 of great optical power.

The control means of the forming apparatus varies the dimension and/or the duration and/or the emission power of the light beam emitted, on the basis of the operating conditions of the forming apparatus. In addition, if a pyrometer is provided for reading the temperature T of the ribbon 4 of adhesive material, the source of radiant energy 4 is controlled retroactively on the basis of the temperature data T of the ribbon 4 that are acquired downstream of the source 14.

By considering the path P and the advancement direction D of the continuous web 3, the adhesive material of the ribbon 4 can be hit by the radiant energy upstream of the forming beam 7 or at the forming beam 7 but upstream of the wrapping position 8. For example, the position can be selected in which it is appropriate to arrange the source of radiant energy 14 for the overall dimensions of the source in the forming apparatus 1 or the position can be selected in which the heating of the ribbon 4 is more effective.

The choice of position in which the source 14 is arranged can also depend on the configuration of the forming apparatus, if the ribbon 4 of adhesive material is applied to the continuous web 3 upstream of the loading station 6 or if the ribbon 4 of adhesive material is reactivated that is present in an inactive state in the continuous web 3 supplied by reel.

Owing to the invention, it is thus possible to heat the ribbon 4 without damaging the continuous web 3 as the ribbon is hit directly and not through the continuous web 3.

Further, by selecting a source of radiant energy 14 that is able to emit a light beam 15, it is possible to position the source 14 facing the ribbon or spaced away therefrom, suitably directing the light beam 16 to the ribbon 4 with optical deflecting means such as, for example, mirrors. This ensures great positioning flexibility of the source of energy 14 in the forming apparatus 1.

In addition, by being able to adjust the duration, frequency and power of the pulses of the emitted light beam 16, effective gluing of the continuous rod 2 is ensured, at the first daily start up of the machine, or after a stop, or for long operating periods, inasmuch as the adhesive material is always heated in an optimum manner. Another result is that the minimum possible quantity of adhesive material can be used, the heating of which is independent of the quantity of adhesive material used.

The cooled plates present in the forming beam 7 can thus be simpler and this, together with the absence of heating plates along the path P and the positioning flexibility of the source of radiant energy 14, translates into a simpler and thus less costly forming apparatus.

Further, owing to the selection of a light beam 16 in a specific wavelength range, in which the adhesive material absorbs the radiant energy whereas the continuous web reflects the radiant energy, the continuous web 3 is not damaged although it is hit by the light beam 16, even when the latter is of great power.

The possibility of heating the ribbon 4 even with great radiant power enables the forming apparatus to be simplified further, which can be devoid of the glue-applying device. In fact, although reactivation of the adhesive material requires high-power heating, it is possible to provide just one source of radiant energy 14 that is able to emit suitable power or it is possible to provide several sources along the path P that are able to emit suitable power, to ensure optimum heating of the ribbon 4.

Also, what has just been said is translated into a simpler and thus less costly forming apparatus.