Patent Description:
More specifically, the invention refers to a straw that has enhanced flexural rigidity, making it also suitable for mixing liquid or semi-liquid products (beverages, granitas, fruit shakes, milk shakes and more).

Known at the present time are straws made of paper material, obtained from a web or sheet of paper material. These have very good environmental properties (easy waste disposal) but low rigidity properties, which means they cannot be effectively used for mixing semi-liquid or thick products because they tend to bend or break, thus becoming totally useless.

Also known are straws made from plastic material, obtained by extrusion. These are more rigid than paper straws but less environmentally friendly and in some cases, they are also not rigid enough for use with semi-liquid or thick products.

In this context, the basic technical purpose of this invention is to provide a food-safe straw and a method for making it, to overcome the above mentioned disadvantages of the prior art.

In particular, this invention has for an aim to provide a food-safe straw that can be used to consume semi-liquid or thick products, allowing them to be mixed without being bent or twisted out of shape or breaking.

Another aim of this invention is to provide a food-safe straw which complies with current waste disposal regulations, hence minimizing its environmental impact.

The technical purpose indicated and the aims specified are substantially achieved by a food-safe straw and a related method comprising the technical features described in claims <NUM> and <NUM> and/or in one or more of the claims dependent thereon.

According to the invention, the straw comprises an outer tubular element and a longitudinal insert placed inside the outer tubular element and defining an element for enhancing the bending strength of the straw.

The outer tubular element is made of paper material and extends along a longitudinal axis.

Preferably, the insert extends along the longitudinal axis for a length corresponding to the length of the outer tubular element. The length is preferably between <NUM> and <NUM>.

The longitudinal insert is also made of paper material and is connected stably to an inner surface of the outer tubular element.

The insert has a profile whose shape, in transversal cross section, is defined by a line that is at least partly corrugated and/or partly jagged in such a way as to increase the bending strength of the straw. This profile shape may be three-dimensional and not circular. According to the invention, the outer layer is not necessarily the outermost layer but a layer that is on the outside of the insert. For example, the outer layer might be an intermediate layer that is in turn covered by another layer on the outside of it.

The insert is connected stably to the inner surface of the outer tubular element in at least two zones, more preferably in at least three zones which are angularly spaced from each other around the longitudinal axis. These connecting zones preferably extend along the full length of the straw.

A straw according to the preamble of claim <NUM> is known from the document <CIT>.

In a preferred embodiment, the connecting zones are spaced from each other by intermediate portions of the insert that extend towards the longitudinal axis, preferably uninterruptedly.

In an embodiment, the connecting zones define a main portion of the surface of the insert, preferably a portion of between <NUM>% and <NUM>% of the surface of the insert.

In an embodiment, the intermediate zones define a main portion of the surface of the insert, preferably a portion of between <NUM>% and <NUM>% of the surface of the insert.

In an embodiment, the shape of the insert, in transversal cross section, extends along a curved profile, preferably without edges and/or rectilinear portions. In this solution, the connecting zones are defined by tangential zones between the insert and the outer tubular element.

In an embodiment, the insert has a corrugated profile, in transversal cross section, having a succession of top portions, defining the connecting portions, alternated with bottom portions, facing towards the longitudinal axis. In this solution, the straw may comprise (but not necessarily) an additional inner covering layer that is stably connected to the bottom portions and thus defines a smaller diameter region of the straw.

In an alternative embodiment, the connecting portions have a curvature that is substantially concentric with the outer tubular element. In other words, the curvature is such that the connecting portions adhere entirely or almost entirely to the inside wall of the outer tubular element (hence, a curvature that is substantially identical to the outer tubular element). This results in complete (or almost complete) adherence between the connecting portions and the outer tubular element, unlike the solution described above, where the connection is along the tangential zones only.

In this variant embodiment, the intermediate portions create structural continuity between adjacent connecting portions and are preferably defined by reinforcing ribs. This allows increasing the flexural modulus of the straw, compared to the case where the insert is simply circular. The ribs are preferably U- or V-shaped but may also be shaped differently.

In a variant embodiment, the insert has a rectilinear shape. In this variant, the connecting zones are preferably opposite to each other (spaced at <NUM>° from each other).

In a further variant embodiment, the insert is substantially S-shaped and has two connecting zones whose curvature substantially follows the curvature of the outer tubular element. In this variant, the connecting zones may be alternated with a rectilinear or curved intermediate zone.

In an embodiment, the shape of the insert, in transversal cross section, extends along a closed profile. This closed profile may be defined by folding (wrapping or rolling) a sheet or portion of a continuous web so its opposite longitudinal edges are joined together to obtain a closed profile.

In an alternative embodiment, the shape of the insert, in transversal cross section, extends along an open profile. In this situation, therefore, the two opposite longitudinal edges are not brought into contact with each other.

In a first embodiment, the outer tubular element defines a main longitudinal cavity intended for the passage of a liquid or semi-liquid product (hence the straw does not comprise a corresponding inner tubular element concentric with the outer tubular element and the insert extends between at least two distinct portions of the inner surface of the outer tubular element (that is to say, it has two distinct connecting portions) and is positioned in the main cavity of the straw intended for the passage of the liquid or semi-liquid product. In this solution, therefore, the insert is, during use, normally immersed and/or surrounded by the liquid or semi-liquid product.

In a different embodiment, the straw comprises an outer tubular element and an inner tubular element, concentric with each other and defining, between them, an annular chamber in which the insert is placed. Preferably, the insert has outer connecting portions that are fixed to the outer tubular element and/or inner connecting portions that are fixed to the inner tubular element.

Preferably, the insert is made by folding, specifically by transversally folding a continuous web which is then cut.

Preferably, the insert is made in a single body by folding, specifically by transversally folding a continuous web which is then cut.

Preferably, the insert and the outer tubular element are made in a single body (a sheet or portion of a continuous web) by folding, specifically by transversally folding a continuous web which is then cut.

In an alternative embodiment, the insert and the outer tubular element are made separately and connected to each other at a later stage.

Preferably, the connecting portions are connected to the outer tubular element by gluing, preferably using at least one glue selected from: water-based glue (for example, PVA) hot-melt glue, edible glue, biodegradable glue, compostable glue.

According to the invention, the straw is made by wrapping, preferably progressive, an outer layer around an inner preformed layer, the outer layer defining the outer tubular element and the inner layer defining the insert. A method for making a food-safe straw according to the invention, obtained by shaping two separate webs, comprises the following steps:.

In an alternative embodiment, a method for making a food-safe straw according to the invention, obtained by shaping a single continuous web, comprises the following steps:.

Preferably, the step of folding and/or deforming the first web or the first portion of the web is carried out continuously so that the first web or the first portion of the web is deformed while the first web or the first portion of the web advances continuously.

Preferably, the step of folding and/or deforming the first web or the first portion of the web is performed by a first sub-step of deforming the first web or the first portion of the web, preferably a permanent deformation, and a subsequent second sub-step of at least partly wrapping the first web or the first portion of the web about the longitudinal axis, preferably around a spindle to give the first web or the first portion of the web the shaped configuration.

Preferably, the first sub-step is performed by imparting a permanent deformation to the first web or to the first portion of the web through a pair of deformation rollers configured to impress on said first web or on said first portion of the web a transversal succession of longitudinal protrusions or corrugations.

Preferably, also, the step of wrapping the second web or the second portion of the web around the shaped insert comprises, or is preceded by, a step of applying an adhesive substance in a zone of the insert and/or of the second web (or second portion of the web) where the insert and the outer tubular element will come into contact with each other, so as to obtain a straw in which the insert and the outer tubular element are stably connected.

The invention is described below with reference to the accompanying drawings, which illustrate a non-limiting embodiment of it and in which:.

A food-safe straw made according to the invention is illustrated in <FIG>. The straw <NUM> essentially comprises an outer tubular element <NUM> and an insert <NUM> placed therein, and extends along a longitudinal axis defining a main direction of extension of the straw <NUM>. The insert <NUM> extends longitudinally into the outer tubular element <NUM>, preferably for the full length of the straw <NUM> so that both the outer tubular element <NUM> and the insert <NUM> have flush end surfaces.

The outer tubular element <NUM> and the insert <NUM> are made of a paper material. The paper material may be a single-layer or multilayer material.

According to an aspect of the invention, the insert <NUM> has a profile whose shape, in transversal cross section, is defined by a line that is at least partly corrugated and/or partly jagged in such a way as to increase the bending strength of the straw <NUM>.

In other words, the insert <NUM> has a three-dimensional shape other than a circular shape so its bending strength is greater than it would be if it had a plain circular shape.

Looking in more detail, in the context of this invention, three-dimensional shapes of the insert <NUM> may include transversal cross section shapes obtained by a process of elastic and/or permanent deformation of a sheet or web such that the insert <NUM> has, in transversal cross section, a specifically contoured shape that is visible in the outer tubular element <NUM> from the outside. The shape is preferably modelled on a geometrical figure or a symbol or a generic shape of varying complexity. By way of non-limiting example, the shape may have a corrugated configuration or it may be the shape of a star or a leaf or a letter of the alphabet (for example, an "S" or an omega, as in <FIG> and <FIG>) or of a logo (for example, a trademark) or a geometrical figure (square, triangle, rectangle), or a heart or other shape. In the context of this invention, the specific shape does not constitute a limitation of the invention but falls within its scope insofar as the insert <NUM> adopts a specific shape whose purpose is to increase the bending strength modulus of the straw in at least one direction, preferably in two directions which are transversal or perpendicular to each other. Moreover, the shape of the insert may also be selected with a view to evoking a specific image or emotion in the user.

<FIG> and <FIG> show a first embodiment in which the shape of the insert <NUM>, in cross section, follows a totally curved, open line.

This shape of the insert <NUM> defines three connecting zones <NUM> where it joins the outer tubular element <NUM> and which correspond to the same number of zones where the insert <NUM> and the outer tubular element <NUM> are tangent or similar or identical in curvature. These connecting zones <NUM> extend for the full length of the straw <NUM>, in particular defining connecting areas or lines.

Preferably, the connecting zones <NUM> are the sites where an adhesive substance is applied in order to stably, and in particular, irreversibly join the outer tubular element <NUM> and the insert <NUM> to each other.

The adhesive substance may comprise at least one glue selected from: water-based glue (for example, PVA) hot-melt glue, edible glue, biodegradable glue, compostable glue.

The connecting zones <NUM> are angularly distributed around the longitudinal axis of the straw <NUM> and are spaced from each other by respective intermediate portions <NUM> that are not connected to the outer tubular element <NUM>. The intermediate zones <NUM> extend towards the longitudinal axis of the straw, thus defining radial protrusions, directed radially inwards, relative to the connecting portions <NUM>.

In the specific embodiment illustrated in <FIG> and <FIG>, the connecting portions <NUM> and the intermediate portions <NUM> jointly define a single shape with a smooth, curvilinear profile without rectilinear stretches or edges.

Also, in the embodiment of <FIG> and <FIG>, the intermediate zones <NUM> define a main portion of the surface of the insert <NUM>, preferably a portion of between <NUM>% and <NUM>% of the surface of the insert <NUM>.

The insert is formed by folding and/or wrapping a single body, specifically a segment or portion of a continuous web.

<FIG> shows a variant embodiment in which the insert <NUM> has a succession of connecting zones <NUM> whose curvature substantially follows the curvature of the outer tubular element <NUM> and which are glued to it entirely or almost entirely. The connecting zones <NUM> preferably lie on a common circle and extend along the full length of the straw <NUM>.

The connecting zones <NUM> are alternated with respective intermediate zones <NUM> defining V-shaped, inward facing protrusions whose vertices are pointed towards the longitudinal axis of the straw <NUM>.

In this embodiment, too, the insert may be formed by folding and/or wrapping a single body, specifically a segment or portion of a continuous web. Unlike the embodiment of <FIG> and <FIG>, the insert <NUM>, in this case, extends along a closed line and its end edges are close together or abutted end to end in a closing zone <NUM>.

Moreover, in this embodiment, it is the connecting zones <NUM> that define the main portion of the surface of the insert <NUM>, preferably a portion of between <NUM>% and <NUM>% of the surface of the insert <NUM>.

<FIG> shows a variant embodiment that differs from <FIG> in that the intermediate zones <NUM> are arcuate, specifically in the shape of circular arcs, with convexity facing towards the longitudinal axis of the straw <NUM>.

More generally speaking, the intermediate portions <NUM> define longitudinal ribs protruding towards the inside of the straw <NUM> in order to increase the bending strength of the straw <NUM> so it is also suitable for mixing liquid or semi-liquid (thick) products.

In a further variant, illustrated in <FIG>, the insert <NUM> has, in transversal cross section, a corrugated profile, preferably periodic and symmetrical. The corrugated profile has a succession of top portions, defining the connecting portions <NUM> connected to the outer tubular element, alternated with bottom portions, facing towards the longitudinal axis of the straw and defining the intermediate portions <NUM>. Preferably, optionally provided is an inner covering layer, or inner tubular element <NUM>, that is stably connected (glued) to the bottom portions and thus defines a circular channel for the passage of the food product.

In a yet further possibility, as illustrated in <FIG>, the inner tubular element <NUM> may, in general, also be provided for the other embodiments, in particular those in which the insert <NUM> extends along a closed, or substantially closed, line or in any case, along a profile forming a ringshaped figure. In this situation, the inner tubular element <NUM> is internally applied and connected to the insert <NUM>, specifically to the intermediate portions <NUM>. That way, the insert <NUM> remains confined within an annular zone interposed between the outer tubular element <NUM> and the inner tubular element <NUM>.

In a further variant embodiment, as illustrated in <FIG>, the insert <NUM> has a rectilinear shape and there are two connecting zones <NUM>. These connecting zones <NUM> are preferably opposite to each other (spaced at <NUM>° from each other).

These connecting zones <NUM> are alternated with a rectilinear intermediate zone <NUM>.

In a further variant embodiment, as illustrated in <FIG>, the insert <NUM> is substantially S-shaped. The insert <NUM> comprises two connecting zones <NUM> whose curvature substantially follows the curvature of the outer tubular element <NUM> and which are glued to it entirely or almost entirely. The connecting zones <NUM> preferably lie on a common circle and extend along the full length of the straw <NUM>.

The connecting zones <NUM> are alternated with a rectilinear intermediate zone.

In a further variant embodiment, as illustrated in <FIG>, the insert <NUM> is substantially S-shaped. The insert <NUM> comprises two connecting zones <NUM> whose curvature substantially follows the curvature of the outer tubular element <NUM> and are glued to it entirely or almost entirely. The connecting zones <NUM> preferably lie on a common circle and extend along the full length of the straw <NUM>.

The connecting zones <NUM> are alternated with curved intermediate zones <NUM>.

The reference numeral <NUM> in <FIG> denotes in its entirety a machine for making the straw <NUM> described above, according to a first embodiment of it.

To make the outer tubular element <NUM> of the insert <NUM>, the machine <NUM> uses respective continuous webs advancing along respective feed paths and which may be unwound from respective rolls or be obtained by cutting an initially single web longitudinally. However, in a variant embodiment, the outer tubular element <NUM> and the insert <NUM> may be obtained by folding, wrapping and/or gathering a single web.

Whatever the case, the main purpose of the machine is to at least partly form first the insert and then wrap the outer tubular element progressively around the insert. More specifically, the insert is a continuous insert and wrapping the outer tubular element occurs progressively to form an outer tubular element that is also continuous before cutting into segments (straws).

The machine <NUM> of <FIG> comprises first feed means <NUM> for feeding a first continuous web and configured to make at least a first continuous web <NUM> advance along a first feed path P1 and second feed means <NUM> for feeding a second continuous web and configured to make a second continuous web <NUM> advance along at least a respective second feed path P2.

The webs <NUM>, <NUM> are made of paper and are unwound from respective rolls 2a, 3a, preferably motor-driven.

Preferably, the webs <NUM>, <NUM>, at least in a step of unwinding them from the respective roll 2a, 3a are defined by a single layer.

The machine <NUM> also comprises a forming station <NUM>, disposed on the first feed path P1 and configured to fold and/or deform the first continuous web <NUM> in such a way as to obtain a continuous web with a shaped configuration. In other words, the forming station <NUM> elastically and/or permanently deforms the first web <NUM> so that the web changes from a flat configuration to a three-dimensional configuration, specifically a laterally gathered configuration, such as to make it suitable for insertion into, thus partly filling, a continuous tube following it.

The forming station is illustrated in detail in <FIG>.

Advantageously, the forming station <NUM> is configured to operate steplessly, thus deforming the first web <NUM> while the first web <NUM> advances steplessly.

This is preferably achieved thanks to the structure of the forming station <NUM>, which is configured to make the first web <NUM> pass uninterruptedly through a forming gap whose transverse cross section is such as to give the first web <NUM> the above mentioned shaped configuration. Preferably, the forming gap is defined by a slot extending along an open line - that is to say, where the ends of the line along which the forming gap extends are spaced and do not coincide.

In an embodiment, the forming station <NUM> is configured to deform the first web <NUM> at least partly elastically. More in detail, that means folding longitudinal portions of the first web <NUM> relative to each other in such a way as to allow "lateral compacting" or, more generally speaking, "transverse compacting" of the first web <NUM>, but reversibly, so that the first web <NUM> thus shaped retains a certain elastic tendency to return laterally to its original shape, causing it to adapt to the internal shape of the continuous tube it will next be inserted into.

In this embodiment, the forming gap extends along an open line which is at least partly, and preferably entirely, defined by a succession of curved stretches and specifically by a spline curve. The open line may also have straight stretches - for example, straight stretches alternated with curved stretches or splines - thereby deforming or compacting gently and gradually in order to prevent or limit permanent deformations.

In addition or alternatively to deforming elastically, as just described, the forming station <NUM> is configured to deform the first web <NUM> at least partly permanently, specifically to fold the first web <NUM> about one or more longitudinal fold lines. More in detail, that means permanently deforming certain specific zones of the first web <NUM>, allowing lateral compacting to a greater degree than in the case of purely elastic deformation, as well as repeatedly folding superposed layers. In this last embodiment, the forming gap extends along an open line which has one or more sharp corners defining respective longitudinal fold lines for permanently folding the first web <NUM>.

As mentioned above, the forming station <NUM> may produce lateral compacting elastically or permanently, or a combination of the two, specifically with elastically deformed zones alternated with permanent fold lines.

In a preferred embodiment, shown in <FIG>, the forming station <NUM> comprises a pair of rollers <NUM>, <NUM> between which the first web <NUM> is made to pass and which have respective matchingly shaped external features 31a, 32a (that is to say, whose profiles are shaped to match each other and are thus geometrically compatible) defining the forming gap between them. In other words, the rollers <NUM>, <NUM>, rotatable about parallel axes, have respective peripheral profiles which, in cross section relative to a plane passing through the respective axis, correspond to, and hence are shaped to match, each other so as to define the forming gap of substantially uniform width through which the first web <NUM> is shaped.

In the embodiment illustrated in <FIG>, a forming gap of the type described above is also defined by a second forming element, hereinafter called preforming element <NUM>, disposed upstream of the forming rollers <NUM>, <NUM> and configured to pre-shape the first web <NUM>.

Looking in more detail, the preforming element <NUM> may be defined by a rigid or monolithic element provided with a fixed forming gap by which the first web <NUM> undergoes an initial deformation to give the first web <NUM> a configuration that makes it easier for it to pass through the pair of rollers <NUM>, <NUM>.

In an embodiment not illustrated, the preforming element <NUM> may even be sufficient to act as a single forming element, in place of the pair of rollers <NUM>, <NUM>.

In a preferred embodiment, the rollers <NUM>, <NUM> are, instead, structured and/or mounted in such a way as to be held together by a predetermined force such as to compress the first web <NUM> passing between them. In this configuration, therefore, the size of the forming gap between the rollers <NUM>, <NUM> is defined by the thickness and compressibility of the first web <NUM>. This advantageously allows giving the rollers <NUM>, <NUM> not only a function of forming the first web <NUM> but also of entraining it, where at least one of the two rollers <NUM>, <NUM> is associated with respective motor means.

Downstream of each of the aforementioned feed means <NUM>, <NUM> and of the forming station <NUM>, the machine <NUM> also comprises a tubular guide <NUM> configured to guide the first web <NUM> as it leaves the forming station <NUM> that has given it the shaped configuration and so that it keeps the shaped configuration as it proceeds from the forming station to a wrapping station <NUM> (described below).

In effect, the passage of the first web <NUM> through the tubular guide <NUM> in the shaped configuration allows the first web <NUM> to keep its shape, contrasting its tendency to return elastically to a laterally expanded configuration.

The tubular guide <NUM> is shown in detail in <FIG>.

Preferably, the tubular guide <NUM> has at least one stretch <NUM> whose transverse cross section progressively decreases, gradually decreasing in diameter, for example, so as to further compact the shaped first web <NUM> transversely before it reaches the wrapping station <NUM>, so that the first web <NUM> that has already been shaped is given the required final transverse cross section.

<FIG> show cross sections of the tubular guide <NUM>, respectively upstream and downstream of the stretch <NUM> with the decreasing transverse cross section, specifically at the cross sections S1 and S2 of <FIG>.

In a preferred embodiment, the tubular guide <NUM> is made entirely in one piece. It may, however, also be made up of a succession of parts connected to each other to form a single rigid body.

As shown in <FIG>, the tubular guide <NUM> has an outlet end portion <NUM> with an outlet opening <NUM> lying in an inclined plane not perpendicular to the feed direction of the shaped first web in such a way that the outlet opening <NUM> faces down.

In a further embodiment not illustrated, the tubular guide <NUM> may itself be a forming element if the web <NUM> is not required to adopt a predetermined shaped configuration and has to pass through the tubular guide <NUM> only. Downstream of the forming station <NUM> and of the tubular guide <NUM>, the machine <NUM> also comprises the aforementioned wrapping station <NUM>, where the first feed path P1 and the second feed path P2 meet and where the second web <NUM> is wrapped around the previously formed first web having the shaped configuration, thus obtaining a continuous tube defined by an outer covering enclosing within it the first web that has been shaped.

Looking in more detail, the wrapping station <NUM> is located at the end portion <NUM> of the tubular guide <NUM> from which the first web <NUM> comes out with the shaped configuration and the second web <NUM> is at least partly wrapped directly round the end portion <NUM> of the tubular guide <NUM>. Wrapping is accomplished by superposing opposite lateral edges of the second web <NUM> and gluing them to each other.

The wrapping station preferably also comprises a belt (not illustrated) for guiding the second web <NUM> driven along a closed path and designed to act in conjunction with fixed deflectors for guiding the second web <NUM> being wrapped around the end portion <NUM> of the tubular guide <NUM>.

As shown in <FIG>, the second web <NUM>, during its initial wrapping movement around the end portion <NUM> of the tubular guide <NUM>, comes from below and thus the aforementioned outlet opening <NUM> of the tubular guide <NUM> faces a central portion of the second web <NUM> being wrapped around the end portion <NUM> itself. This advantageously allows exposing a portion of the second web <NUM> and/or of the shaped first web <NUM> so that they can be glued to each other to permanently join the shaped first web <NUM> to the second web <NUM>. In other words, at least the shaped first web <NUM> or the second web <NUM> have to interact with a gluing device <NUM> along their path in order to spread a layer of glue on at least one of the two webs <NUM> or <NUM> so as to join the two webs <NUM> and <NUM> to each other.

In a possible embodiment, the end portion <NUM> of the tubular guide <NUM> may have the shape of a truncated cone or otherwise tapered in the direction of the continuous tube being formed.

In particular, the gluing device <NUM>, configured to apply an adhesive substance - for example, water-based glue (such as PVA), or hot-melt glue, edible glue, biodegradable glue, compostable glue - on the shaped first web and/or on the second web <NUM>, may be disposed in proximity to the wrapping station <NUM>, and, more specifically, near the outlet opening <NUM>. The gluing device <NUM> preferably comprises one or more spray nozzles, not illustrated, configured to direct a jet of glue on the shaped first web or on the second web <NUM>.

In embodiments not illustrated, the gluing device may be disposed at a different position: for example, on the first and/or the second feed path P1, P2.

Located downstream of the wrapping station <NUM> there is a cutting station <NUM> for dividing the continuous tubular element into a succession of tubular segments <NUM> defining individual straws <NUM>, specifically between <NUM> and <NUM> in length. The cutting station <NUM> may comprise a rotary blade of customary type as used, for example, to cut continuous, rod-shaped elements, specifically paper tubes or even continuous cigarette or filter rods, and provided with a rotary drum fitted with one or more radial, preferably adjustable blades.

<FIG> shows a second embodiment of the machine <NUM>. The machine <NUM> of this embodiment differs from that of <FIG> in that it comprises, on the second feed path P2, upstream of the wrapping station <NUM>, a folding device <NUM> operating on the second web <NUM> to fold the second web <NUM> about two parallel, longitudinal fold lines to give the second web <NUM> a three-layer structure.

In this situation, the outer tube <NUM> thus made is visible in the view of <FIG> and in the enlarged view of <FIG>, showing the splicing zone where the opposite lateral edges of the second, three-layer web <NUM> are joined.

More generally, the folding device <NUM> disposed on the second feed path P2 may be configured to fold the second web <NUM> one or more times about one or more parallel, longitudinal fold lines to give the second web <NUM> a multilayer structure. Folding in this way is carried out continuously by one or more fixed deflectors having respective folding edges disposed at the respective longitudinal fold line. In order to facilitate folding the second web about the longitudinal fold lines, a scoring device (not illustrated) may be provided on the second feed path P2, upstream of the folding device <NUM>, to make one or more longitudinal lines of weakness that will constitute the fold lines in the folding device <NUM>.

With reference to the embodiment of a straw <NUM> according to <FIG>, the machine described above may be substantially the same as that in which the first web <NUM> is deformed, except for changes in the geometry of the deformation rollers <NUM>, <NUM> that form the insert <NUM>. In such a case, there is a first sub-step of deforming the first web <NUM>, preferably deforming it permanently, followed by a second sub-step of at least partly wrapping the first web <NUM> around a longitudinal spindle to give the first web <NUM> the aforementioned shaped configuration. In this case, on their outside surfaces, the two deformation rollers <NUM>, <NUM> are provided with a succession of circumferential ridges (on one roller) and corresponding circumferential grooves (on the other roller), respectively V- or U-shaped in cross section, so as to give the first web <NUM> a transversal succession of longitudinal ridges or corrugations.

This invention is susceptible of modifications without departing from the scope defined by the independent claims. By way of an example, in the case of a multilayer outer tube, for example with at least two at least partly superposed webs, two or more second webs from respective rolls (or from a single roll cut lengthways to form two webs) and wrapped in such a way as to present respective splicing zones angularly spaced about the axis of the final tubular segment can be used instead of a single second web folded about one or more longitudinal, parallel fold lines.

Furthermore, on the first and/or the second feed path there may be an additional applicator device for applying an additional substance, for example, a flavouring, on the first and/or the second web as they advance before and/or after being formed.

According to a further optional possibility, a creasing and/or scoring device may be provided on the first feed path to make one or more lines of weakness (either continuous or with cyclic interruptions) on the first web to facilitate its subsequent deformation in the forming station. Alternatively, the first web might have these creases and/or scored cuts already made on it when it is unwound from the respective roll.

Moreover, the guide <NUM> might coincide totally or at least partly with the wrapping station <NUM>, where the outer surface of the guide <NUM> allows wrapping the second web <NUM>.

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

Claim 1:
A food-safe paper straw, comprising:
- an outer tubular element (<NUM>) made of paper material which extends along a longitudinal axis;
- a longitudinal insert (<NUM>) made of paper material positioned inside the outer tubular element (<NUM>) and stably connected to an inner surface of the outer tubular element (<NUM>), characterised in that
said insert (<NUM>) having a profile, in transversal cross section, defined by a line at least partly corrugated and/or partly jagged in such a way as to increase the bending strength of the straw (<NUM>), wherein said insert (<NUM>) is stably connected to the inner surface of the outer tubular element (<NUM>) in at least two connecting zones (<NUM>), preferably at least three connecting zones (<NUM>), angularly spaced from each other about said longitudinal axis.