Patent Description:
Known in the tobacco industry is the need for tube-shaped elements of paper material, for example for use as components of traditional cigarettes (to make the filters, for example) or "HNB" (heat-not-burn) cigarettes. For increased strength, these tube-shaped elements are made with a multilayer structure.

Generally speaking, these multilayer tube-shaped elements are made by superposing and gluing two paper webs in such a way as to obtain, on one or both of the longitudinal edges, suitable joining zones intended to be spliced to each other to form a tube-like configuration.

Also, to obtain a shape that is as cylindrical as possible, the two webs are offset during superposing and gluing, so that, when the tube is formed, the splices between the corresponding end edges of the two layers are angularly spaced from each other about the axis of the tube itself.

These known production methods, however, have the disadvantage of not guaranteeing sufficient precision in the final shape of the tube, especially in terms of precise size and superposition of the two webs. In effect, if the two webs are of the wrong size or incorrectly positioned relative to each other, the final shape will likely be irregular, and the edges of the layers not properly juxtaposed, resulting in a poor connection in the splicing zones or in a tube with an incorrect diameter. <Insert page 1a>.

In this context, the basic technical purpose of this invention is to provide a method and a machine for making multilayer tubes of the tobacco industry to overcome the above mentioned disadvantages of the prior art.

More specifically, this invention has for an aim to provide a method and a machine for making multilayer tubes of the tobacco industry, capable of guaranteeing a high level of dimensional precision of the end product.

It is also known from <CIT> to form a two-layer strip at a folding roller and to longitudinally wrap the two-layer strip into a tubular shape.

The technical purpose indicated and the aim specified are substantially achieved by a method and a machine for making multilayer tubes of the tobacco industry, comprising the technical features described in claims <NUM> and <NUM>, respectively, and/or in one or more of the claims dependent thereon. The invention is described below with reference to the accompanying drawings, which illustrate a non-limiting embodiment of it, in which:.

With reference to the accompanying drawings, the numeral <NUM> denotes in its entirety a machine for making tubes of the tobacco industry according to this invention (only partly illustrated in the accompanying drawings).

The machine <NUM> comprises feed means <NUM> for feeding a continuous web <NUM> and configured to feed a continuous web <NUM> along a feed direction X parallel to the direction of extension of the web <NUM> and, along the feed path of the web <NUM>, a first folding station <NUM>, followed by another folding station <NUM>. Each folding station <NUM>, <NUM> is configured to fold a respective longitudinal strip of the web <NUM> onto a second longitudinal strip of the web <NUM> about a longitudinal fold line which is parallel to the feed direction X so as to obtain a multilayer web having at least two superposed layers.

Looking in more detail, the embodiment illustrated has two consecutive folding stations <NUM>, <NUM> to fold respective longitudinal strips in such a way as to obtain a three-layer web. To obtain a two-layer web, however, only the first folding station <NUM> is necessary.

Downstream of the two folding stations <NUM>, <NUM> there is also a forming station <NUM> for forming a continuous tube from the multilayer web. More in detail, the forming station <NUM> is configured for continuously wrapping the multilayer web itself around a longitudinal axis to form a continuous tube with a longitudinal splice.

Interposed between the folding stations <NUM>, <NUM> and the forming station <NUM> there may be an uncoupling and/or tensioning station <NUM> operating to allow the continuous web <NUM> to move at different speeds upstream and downstream and/or to tension the web, for example with a "dandy roller" system.

Downstream of the forming station <NUM> there is a cutting station (not illustrated) operating on the continuous tube to make a succession of transverse cuts to obtain a succession of tubes <NUM> of the tobacco industry.

The term "tube of the tobacco industry" is used to denote a generic tubular element, made, for example, of paper, plastic or metal or combinations thereof, cylindrical in shape, internally hollow and open at both ends.

The tube may be used directly in the form thus made, in particular internally hollow, to define a segment of a cigarette (traditional, HNB or other type of cigarette) or it may be intended to contain filling material such as tobacco fibre, granules or other material suitable for heat-not-burn (HNB) technology. Generally, the length of the tube is less than the length of a standard cigarette because the tube is advantageously used to make a cigarette segment.

<FIG> illustrate details of the structure of the tube <NUM> in transverse cross sections. In particular, <FIG> shows the final configuration of the tube <NUM>, where different layers can be seen (in the embodiment with the three-layer thickness), while <FIG> show the configurations after the first step of folding and after the second step of folding, respectively. The two steps of folding are carried out, respectively, on a first longitudinal strip <NUM> of the web <NUM>, folded over onto a second longitudinal strip <NUM> of the web <NUM>, and on a third longitudinal strip <NUM> of the web <NUM>, folded over onto the second longitudinal strip <NUM> of the web <NUM> (or on the first longitudinal strip <NUM> after it has been folded). More specifically, the longitudinal strips <NUM>, <NUM> subjected to folding are side strips of the web <NUM>, folded flat against the middle strip <NUM> by folding about folding lines which are parallel to the direction of extension of the web <NUM> (perpendicular to the sheet in <FIG>).

<FIG> also show a specific embodiment where the longitudinal strips <NUM>, <NUM> are folded on the same side: that is to say, the second longitudinal strip <NUM> is folded over onto the first longitudinal strip <NUM>, which had, in its turn, been previously folded over onto the middle longitudinal strip <NUM> of the web <NUM>. In the context of this invention, however, the two longitudinal side strips <NUM>, <NUM> might equally be folded on opposite sides, without departing from the inventive concept.

The details of <FIG> are embodiment details showing the splicing zone where opposite lateral edges of the multilayer web are joined and the related recessed zone <NUM> (<FIG>) is made to accommodate a protruding splicing edge <NUM> (<FIG>).

More specifically, the recessed zone <NUM> is obtained by retracting the corresponding edge of the first longitudinal strip <NUM> in such a way that the folding operations create a longitudinal cavity <NUM> (<FIG>) that can be compressed to form the recessed zone <NUM>.

On the opposite lateral edge, the protruding splicing edge <NUM> is obtained by suitably adjusting the folding of the third longitudinal strip <NUM>, specifically by laterally offsetting its respective fold line in such a way as to obtain a portion which extends beyond the width of the portion of web <NUM> that has already been folded (<FIG>).

It is evident that both the recessed zone <NUM> and the protruding splicing edge <NUM> can be modified as a function of the operating parameters of the folding stations <NUM>, <NUM>, specifically the widths of the longitudinal strips <NUM>, <NUM>, <NUM> by suitably varying the position of the longitudinal fold lines.

Described in detail below are the means and procedures used for folding the longitudinal strips <NUM>, <NUM> (or just one of them in the case of a two-layer tube). In particular, the following detailed description applies to the first folding station <NUM>, since the second folding station <NUM> can advantageously be made in the same way.

The first folding station <NUM> has a first deflector edge <NUM> disposed and/or configured to deflect the first longitudinal strip <NUM> of the web <NUM>, and a second deflector edge <NUM> disposed and/or configured to deflect the second longitudinal strip <NUM> of the web <NUM>, and, more specifically, the remaining part of the web <NUM>. The deflector edges <NUM>, <NUM> are shown more clearly in <FIG>.

Advantageously, the deflector edges <NUM>, <NUM> are angled to each other. Looking in more detail, the second deflector edge <NUM> is straight and perpendicular to the feed direction X of the web <NUM>, whilst the first deflector edge <NUM>, which is also straight, is inclined to the second deflector edge <NUM> at an acute angle (α), preferably included between <NUM>° and <NUM>°, and still more preferably, between <NUM>° and <NUM>°.

In a preferred embodiment and as illustrated in <FIG>, the deflector edges <NUM>, <NUM> are peripheral edges of the same deflector element <NUM> which is preferably plate-shaped. More specifically, the deflector element <NUM> is plate-shaped at least at the parts of it defining the peripheral edges used for folding. This gives the deflector element <NUM> a flat shape suitable for folding the web.

The deflector element <NUM> is associated with a respective gluing device <NUM> operating on the first strip <NUM> and/or on the second strip <NUM> of the web <NUM> just upstream of folding the first strip <NUM> and preferably downstream of the second deflector edge <NUM> to deliver an adhesive substance suitable for holding the first strip <NUM> on the second strip <NUM> after folding.

In a variant embodiment not illustrated, the web <NUM> is pre-gummed on specific zones of its surface and the gluing device <NUM> is replaced by hot-melt or high-pressure adhesive activating means. The activating means may be disposed upstream of the folding zone (in the case of hot-melt glue) or downstream of the folding zone (in the case of high-pressure activated glue) to activate the adhesive present in the overlapping zone between the first and the second strip <NUM>, <NUM> of the web <NUM>.

Advantageously the first folding station <NUM> also comprises an auxiliary guide member <NUM> located downstream of the first deflector edge <NUM> to receive and guide the first longitudinal strip <NUM> of the web <NUM> as it leaves the first deflector edge <NUM> and to guide the first strip <NUM> while it is being folded. The auxiliary guide member <NUM> is configured to slidably receive the first longitudinal strip <NUM> of the web <NUM> as it leaves the first deflector edge <NUM> and to guide the first longitudinal strip <NUM> while it is being folded completely onto the second longitudinal strip <NUM>.

Preferably, the auxiliary guide member <NUM> is planar and still more preferably, plate-shaped.

As shown in detail in <FIG>, the auxiliary guide member <NUM> and the first deflector edge <NUM> are disposed in such a way as to come into contact with respective opposite surfaces of the continuous web <NUM>.

Further, the auxiliary guide member <NUM> has a guiding edge <NUM> which is preferably straight and inclined relative to the feed direction X of the web <NUM> in such a way as to progressively fold the first longitudinal strip <NUM> onto the second longitudinal strip <NUM> of the web <NUM>. The guiding edge <NUM> is preferably disposed at an angle β of between <NUM>° and <NUM>° to the feed direction X. In the embodiment illustrated, the angle β is approximately <NUM>°.

With reference to the accompanying drawings, the guide member <NUM> also has an end edge <NUM>, disposed downstream of the guiding edge <NUM> and parallel to the feed direction X, at a position such as to substantially coincide with the free longitudinal edge of the first longitudinal strip <NUM> at the folded position.

In a preferred embodiment and as illustrated in the accompanying drawings, the deflector element <NUM> defines a positioning plane of the web <NUM> entering the folding station <NUM>, whilst the auxiliary guide member <NUM> defines a positioning plane of the continuous web <NUM> leaving the folding station <NUM> (<FIG>, <FIG> and <FIG>).

In an embodiment not illustrated, there is provided, upstream of the folding stations <NUM>, <NUM>, a creasing or scoring station which makes one or more crease lines or lines of weakness intended to coincide with fold lines at a folding station <NUM>, <NUM>. The creasing station may comprise, for example, a pair of opposed rollers, at least one of which is provided with a pair of discs or ridges which are axially spaced from each other to make corresponding parallel lines of weakness on the initial web.

<FIG> shows a further component of the machine <NUM> according to the invention, specifically a stabilizing element <NUM> configured to stabilize the folds on the multilayer web after all the steps of folding have been carried out. More in detail, the stabilizing element <NUM> is disposed downstream of the second folding station <NUM> (or more generally speaking, downstream of the last folding station) and is shaped in such a way as to present one or more deviating edges <NUM>, <NUM> transverse to the feed direction of the multilayer web. The deviating edges <NUM>, <NUM> have the function of applying a flattening action on the folded edges of the multilayer web (labelled M in <FIG>) while the web undergoes a local change in its positioning plane at each deviating edge <NUM>, <NUM>. The multilayer web leaving the stabilizing element <NUM> thus has stable, well-defined folds which have lost any possible curvature that might negatively affect the shape stability of the multilayer web.

According to an advantageous aspect of the invention, for one or both of the folding stations <NUM>, <NUM>, at least one position detector <NUM> is provided downstream and/or upstream of the folding station <NUM>, <NUM> to detect a transverse position of the multilayer web <NUM>. In the embodiment illustrated, there is a single position detector <NUM> upstream of the first folding station <NUM> (only schematically illustrated in <FIG>); there may, however, be a plurality of position detectors <NUM> distributed along the feed line of the web. The machine <NUM> also comprises a processing unit (not illustrated), connected to the position detector <NUM> and to the folding station <NUM>, <NUM>, and configured to vary one or more operating parameters of the folding station <NUM>, <NUM>, preferably the width and/or transverse position of the first and/or the third longitudinal strip <NUM>, <NUM> relative to the second longitudinal strip <NUM> as a function of the transverse position detected. That way, it is possible to maintain a high precision tolerance and to compensate for any constructional imprecisions, and to vary the dimensions of the recessed zone <NUM> and of the protruding splicing edge <NUM> to modify the properties of the longitudinal splice of the continuous tube.

According to a further advantageous aspect of the invention, a device (not illustrated) is used to detect at least one diameter value of the continuous tube and/or of at least one tube <NUM> obtained by cutting the continuous tube. In this situation, the processing unit is also connected to the position detector to vary one or more operating parameters of at least one folding station <NUM>, <NUM>, preferably the width and/or transverse position of the first and/or the third longitudinal strip <NUM>, <NUM> relative to the second longitudinal strip <NUM> as a function of the diameter value detected. This allows using feedback to operate on the folding stations <NUM>, <NUM> to compensate for possible excessive deviations of the real diameter from a reference diameter.

The machine <NUM> may further comprise a centring device <NUM>, located preferably upstream of the folding stations <NUM>, <NUM> for setting a transverse position at least of the continuous web <NUM> entering the first folding station <NUM>. Preferably, the processing unit is configured to operate also on the centring device <NUM> to vary, through the centring device <NUM>, the transverse position of the entire continuous web <NUM> upstream of the folding stations <NUM>, <NUM> as a function of the transverse position detected by the detecting device <NUM>.

There may also be provided an adhesive presence and/or properties detector (not illustrated) - for example, a capacitive sensor - for detecting the presence and/or properties of the adhesive substance, interposed between the first and the second longitudinal strip <NUM>, <NUM> and/or between the second and the third longitudinal strip <NUM>, <NUM> of the continuous web <NUM>.

In the embodiment illustrated in the accompanying drawings, at least one guiding device <NUM> is preferably provided downstream of each folding station <NUM>, <NUM> to adjust the transverse position of the web leaving the station <NUM>, <NUM>.

Further, in an embodiment not illustrated, one or more of the folding stations <NUM>, <NUM> comprises cooling means to prevent the deflector element <NUM> and/or the auxiliary guide member <NUM> from overheating as a result of the web sliding on them.

In use, the continuous web <NUM> is fed along the feed direction X, parallel to the direction of extension of the web <NUM>, and then the first longitudinal strip <NUM> of the web <NUM> is folded onto the second longitudinal strip <NUM> about a respective fold line which is parallel to the feed direction X so as to obtain a multilayer web having two superposed layers. Optionally, the third longitudinal strip <NUM> of the web <NUM> is then folded onto the second longitudinal strip <NUM> (onto which the first longitudinal strip <NUM> had been folded) about a second fold line which is parallel to the feed direction X so as to obtain a multilayer web having three layers.

Next, the continuous tube is formed by continuously wrapping the multilayer web around a longitudinal axis, in particular by juxtaposing and splicing opposite lateral edges of the multilayer web (for example by joining the recessed portion <NUM> to the protruding splicing edge <NUM>).

The continuous tube is then cut transversely to obtain a succession of tubes <NUM> of the tobacco industry.

Each step of folding is accomplished by deflecting the first longitudinal strip <NUM> of the web <NUM> around the respective first deflector edge <NUM> and simultaneously deflecting the second longitudinal strip <NUM> or, as the case may be, the remaining longitudinal strip, of the web <NUM> around the second deflector edge <NUM>.

Whilst the deflection of the first longitudinal strip <NUM> produces a twisting action, or "screwing" motion of its positioning plane such that the first strip <NUM> is overturned onto the second strip <NUM>, the deflection of the remaining part or longitudinal strip of the web <NUM> only changes the inclination of its positioning plane, specifically about an axis (which is substantially defined by the second deflector edge <NUM>) perpendicular to the feed direction X. This change in the inclination of the positioning plane defines a "pitching action" at the front of the web, that is to say, a folding action up or down with reference to the feed direction X of the web <NUM>.

This change in the inclination of the positioning plane, in conjunction with the folding of the first longitudinal strip <NUM>, has the effect of optimizing the superposing geometry of the longitudinal strips, compensating for the greater length of the path that the first longitudinal strip <NUM> would have to travel in its folding movement if the remaining part of the web <NUM> were not deflected.

Claim 1:
A method for making multilayer tubes of the tobacco industry, comprising the following steps:
- feeding a continuous web (<NUM>) along a feed direction (X) parallel to the direction of extension of the web (<NUM>);
- folding a first longitudinal strip (<NUM>) of the web (<NUM>) onto a second longitudinal strip (<NUM>) of the web (<NUM>) about a fold line which is parallel to the feed direction (X) so as to obtain a multilayer web having at least two partly superposed layers;
- forming a continuous tube by continuously wrapping the multilayer web around a longitudinal axis;
- cutting the continuous tube to obtain a succession of tubes (<NUM>) of the tobacco industry;
characterized in that the step of folding is accomplished by deflecting the first longitudinal strip (<NUM>) of the web (<NUM>) around a first deflector edge (<NUM>) and by deflecting a remaining longitudinal strip (<NUM>, <NUM>) of the web (<NUM>) around a second deflector edge (<NUM>), the first and second deflector edges (<NUM>, <NUM>) being angled to each other, in that the step of folding is also accomplished by an auxiliary guide member (<NUM>) located downstream of the first deflector edge (<NUM>) and configured to slidably receive the first longitudinal strip (<NUM>) of the web (<NUM>) as it leaves the first deflector edge (<NUM>) and to progressively guide the first longitudinal strip (<NUM>) while it is being folded completely onto the second longitudinal strip (<NUM>), and in that the method further comprises at least one step of applying an adhesive substance between the first and the second longitudinal strip (<NUM>, <NUM>) performed by a gluing device (<NUM>) which is associated with the deflector element (<NUM>) and operating on the first strip (<NUM>) and/or on the second strip (<NUM>) of the web (<NUM>) just upstream of folding the first strip (<NUM>) to deliver an adhesive substance suitable for holding the first strip (<NUM>) on the second strip (<NUM>) after folding.