FIELD OF THE INVENTION

The present invention concerns a machine and a method to make tubular products which can be used, in particular, but not only, to produce straws for drinking a liquid or semi-liquid product. The tubular products are made by helically winding on a forming mandrel one or more strip-shaped elements, preferably made of paper or derivatives thereof or suchlike, on at least one of which an adhesive substance, for example a glue containing a liquid solvent, has previously been deposited. In particular, the machine described here is provided with an evaporation apparatus which is based on heating the strip-shaped elements on which the adhesive substance has been deposited, by means of electromagnetic waves, in order to remove, through evaporation caused by electromagnetic radiations, at least a part of the liquid solvent, preferably before winding the strip-shaped elements onto the forming mandrel.

BACKGROUND OF THE INVENTION

Machines and methods for the automated production of tubular products are already known, using paper as raw material, from which drinking straws are then obtained. By the term paper we mean both any type of paper, and also any other material similar or comparable to it, or derived from it.

In particular, some of these methods known in the state of the art are based on the helical winding of one or more strip-shaped elements. This manufacturing technique, known by the English term “filament winding”, can be used to manufacture cylindrical bodies, for example tubular, by helically winding one or more strip-shaped elements made of paper under tension around a cylindrical forming pin, or mandrel, after having deposited or spread one or more layers of adhesive substance, for example glue, on at least one surface of the one or more strip-shaped elements.

Examples of such known machines are described in patent application IT 102020000011344 filed by the Applicant.

The disposition of the glue on the strip-shaped elements constitutes a delicate operation since it plays an important role for the structural stability of the tubular products themselves and therefore of the straws, also considering that the thickness of each strip-shaped element with which the latter are formed is very thin, in the range of tenths of a millimeter or, at times, even hundredths of a millimeter.

In fact, if the glue did not guarantee adequate resistance, the tubular products and therefore the straws could collapse, due to the fact that the strip-shaped elements could separate from each other, and/or that each helically wound stripshaped element could become unstuck.

Furthermore, an excessive quantity of glue could lead to the production of tubular products and therefore straws that are not sufficiently rigid, which could bend or sag in an undesirable way, an effect that can be even more evident when the straw is immersed in the liquid to be sipped.

Moreover, for hygienic reasons, the glue must absolutely not come into contact with the liquid or semi-liquid product that passes through the straw, in order to prevent part of the glue from being accidentally ingested by the user.

In order to try to solve these problems, some solutions known in the state of the art have introduced means for drying the glue, for example comprising gas burners or heaters with infrared rays. Some of these solutions are described, for example, in the patent documents EP 1.080.874 Al, JP 2002028995 A, US 2.931.278 A and US 2005/257878 Al.

One disadvantage of these solutions is that the presence of the drying means in some cases significantly increases the overall bulk of the machine, or, in other cases, it does not guarantee an effective drying action, for example because the drying means act on a very short stretch of the path of the strip-shaped elements, or they are disposed too close to the forming mandrel so that the glue does not have sufficient time to dry.

There is therefore a need to make a machine, and to perfect a corresponding method, to make tubular products that use an apparatus, equipment, device, or other suitable set of components, collectively referred to here as equipment, which can remove, by evaporation, at least a part of the liquid solvent contained in the glue, advantageously before the strip-shaped elements enter a forming unit in which the forming pin is located, and that this equipment can be easily inserted into the machine to make tubular products, preferably made of paper, usable in particular, but not only, for the production of straws. Another important aspect to be taken into consideration in the sector of such machines is the productivity, expressed in meters of tubular product made in the unit of time, which corresponds to the speed at which the individual strip-shaped elements must be made to advance toward the forming unit. In fact, the higher the productivity, the higher, in proportion, is also the speed of advance of the strip-shaped elements. For example, to obtain a very high productivity, for example from 60 to 120 m/min of tubular product, which corresponds to about 1,000 straws per minute, the speed of feed of the strip-shaped elements must be a few meters per second, for example from 1 to 2 m/s.

This means that, if the machine for making tubular products is to be kept as compact as possible, the evaporation apparatus must also be compact, but it must guarantee at the same time and in a small space, an excellent removal of a predetermined quantity, preferably programmable, of the liquid solvent contained in the adhesive substance.

Therefore, one purpose of the present invention is to provide a machine and a method to make tubular products, preferably made of paper, which are simple and reliable and which allow, in a limited space, to remove by evaporation a predetermined quantity, preferably programmable, of the liquid solvent contained in the adhesive substance used to form said tubular products.

Another purpose of the present invention is to provide a machine and a method to make tubular products, preferably made of paper, in which it is possible to accurately regulate the quantity of thermal energy used to remove by evaporation at least a part of said liquid solvent.

Another purpose of the present invention is to control, in a simple and prompt, but at the same time precise and reliable manner, the quantity of adhesive substance which is deposited on the strip-shaped elements.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea. In accordance with the above purposes, some embodiments concern a machine to make tubular products, preferably straws, using one or more strip-shaped elements, preferably made of paper or derivatives thereof, or suchlike. The machine comprises delivery means configured to selectively deliver on at least one surface of at least two of the strip-shaped elements an adhesive substance containing at least a liquid solvent, and forming means configured to form the tubular product by winding the one or more strip-shaped elements in a helical manner and simultaneously gluing them, by means of the adhesive substance.

According to one embodiment, the machine also comprises an evaporation apparatus comprising a plurality of evaporation units, each having at least one antenna for transmitting and/or receiving electromagnetic waves having a wavelength, and therefore frequency, characteristic of the microwave spectrum, configured to remove, by evaporation caused by the radiations of the electromagnetic waves, at least a part of the liquid solvent contained in the adhesive substance.

In a preferred embodiment, the apparatus is disposed between the delivery means and the forming means of the machine.

According to one aspect of the present invention, each evaporation unit of the plurality of evaporation units comprises a plurality of walls which define an internal chamber, in which the at least one antenna is disposed, the walls having a pair of through apertures able to allow the passage of a corresponding stripshaped element of the plurality of strip-shaped elements.

In accordance with another aspect, one or more evaporation units are provided, each intended to interact with a respective strip-shaped element and provided with the antenna for transmitting and/or receiving electromagnetic waves. In other words, only one corresponding strip-shaped element passes through each evaporation unit.

According to one possible embodiment, the evaporation units are disposed so as to be positioned in a segment of the path of the strip-shaped elements which develops substantially parallel to a substantially vertical direction, preferably above the delivery means.

According to another aspect of the present invention, the plurality of walls of the plurality of evaporation units are made of metal material, so that the internal chamber is electromagnetically isolated from the external environment.

According to another aspect of the present invention, the through apertures are aligned with respect to each other along a directrix parallel to the vertical direction.

According to some embodiments, the apparatus according to the present invention also comprises a modulator device operatively connected to the at least one antenna for transmitting and/or receiving electromagnetic waves and configured to adjust the intensity of the electromagnetic waves.

We wish to clarify that here and throughout this description with the term intensity we mean the amount of energy transported by one wave per unit of time and per unit of surface.

According to some embodiments, the pair of through apertures comprises an inlet aperture and an outlet aperture, which are configured to allow the passage of the respective strip-shaped element through the internal chamber of the evaporation unit; moreover, the inlet and outlet apertures are aligned with respect to each other along a directrix parallel to the corresponding strip-shaped element while it passes through the corresponding evaporation unit. Furthermore, the relative position of each antenna with respect to the inlet and outlet apertures on the one hand, and the calibrated sizes of the same apertures on the other, allow to prevent, or limit to a minimum, the escape of electromagnetic waves from the internal chamber. This advantageously allows to protect the operators responsible for controlling the apparatus, who in this way are not hit by electromagnetic radiation.

According to other embodiments, a method is provided to make tubular products using one or more strip-shaped elements, preferably made of paper, or similar materials, or materials derived therefrom, comprising a delivery step, in which delivery means selectively deliver on at least one surface of at least two of the one or more strip-shaped elements an adhesive substance containing at least a liquid solvent, and a forming step, in which forming means form the tubular product by winding the one or more strip-shaped elements in a helical manner and simultaneously gluing them, by means of the adhesive substance.

According to one embodiment, the method also comprises an evaporation step in which a plurality of evaporation units, each having at least one antenna for transmitting and/or receiving electromagnetic waves having a wavelength, and therefore frequency, characteristic of the microwave spectrum, are selectively activated to remove, by evaporation produced by the radiations of the electromagnetic waves, at least a part of the liquid solvent contained in the adhesive substance.

According to one aspect of the present invention, in the evaporation step each of the at least two strip-shaped elements on the surface of which the adhesive substance has been delivered passes inside an internal chamber of a respective evaporation unit, where the at least one antenna is disposed to remove at least a part of the liquid solvent contained in the adhesive substance.

In accordance with another aspect, an evaporation apparatus is suitable to be installed in a machine configured to make a tubular product using one or more strip-shaped elements, preferably made of paper, wherein the machine itself is provided with delivery means configured to selectively deliver on at least one surface of at least two of the strip-shaped elements an adhesive substance containing at least a liquid solvent.

In accordance with one aspect, the evaporation apparatus comprises a plurality of evaporation units, each having at least one antenna for transmitting and/or receiving electromagnetic waves having a wavelength, and therefore frequency, characteristic of the microwave spectrum, configured to selectively remove, by evaporation caused by the radiations of the electromagnetic waves, at least a part of the liquid solvent contained in the adhesive substance present on at least one of the strip-shaped elements. The antenna for transmitting and/or receiving electromagnetic waves is therefore configured as an evaporation mean.

In accordance with another aspect, a method to evaporate at least a part of a liquid solvent contained in an adhesive substance present on at least one surface of at least one or more strip-shaped elements, preferably made of paper, used to make tubular products, comprises an evaporation step in which a plurality of evaporation units, each having at least one antenna for transmitting and/or receiving electromagnetic waves having a wavelength, and therefore frequency, characteristic of the microwave spectrum, are selectively activated to remove, by evaporation caused by the radiations of the electromagnetic waves, at least a part of the liquid solvent contained in the adhesive substance. According to some embodiments, which can be combined with all the embodiments described here, there can also be provided a step of adjusting the intensity of the electromagnetic waves emitted by the at least one antenna and the adjustment step is operated by acting on a modulator device operatively connected to the at least one antenna. In particular, the intensity is adjusted in the adjustment step so that it is correlated both to a speed of advance of the stripshaped elements and/or their thickness, and also to the quantity of adhesive substance that has been delivered on the strip-shaped elements.

According to some embodiments, which can be combined with all the embodiments described here, there can also be provided a feedback control step of the quantity of adhesive substance that has been deposited on the strip-shaped elements, in which it is provided to compare an electric signal characteristic of electromagnetic waves received by the at least one antenna with a preset value, correlated to the quantity of adhesive substance that it is provided to deposit on the strip-shaped elements.

According to some embodiments, which can be combined with all the embodiments described here, the evaporation means are part of an evaporation apparatus that is also provided with one or more evaporation units in which the antenna for transmitting and/or receiving electromagnetic waves is disposed and is configured to interact with at least one of the strip-shaped elements, and the evaporation apparatus as above, at least during the evaporation step, is stationary in a determinate position. Preferably, the evaporation step occurs while each of the strip-shaped elements on which the adhesive substance is present passes through the evaporation apparatus with a determinate speed of advance, passing into an internal chamber of a corresponding evaporation unit where the antenna is disposed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages the present invention will become apparent from the following description of one embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a partial and schematic front view of an evaporation apparatus installed in a machine to make tubular products;

- fig. 2 is a schematic perspective view of the apparatus of fig. 1, in which a portion of the machine to make tubular products is also visible;

- fig. 3 is an enlarged detail of fig. 2;

- fig. 4 is a perspective view like that of fig. 3 but from a different perspective, in which the apparatus is seen from below.

We must clarify that in the present description and in the claims the terms vertical, horizontal, lower, upper, right, left, high, low, front and rear, with their declinations, have the sole function of better illustrating the present invention with reference to the drawings and must not be in any way used to limit the scope of the invention itself, or the field of protection defined by the attached claims. For example, with the term vertical our aim is to indicate an axis, or a plane, that can be either perpendicular to the line of the horizon, or inclined, even by several degrees, for example up to 20°, with respect to such perpendicular position.

Furthermore, the person of skill in the art will recognize that certain sizes or characteristics in the drawings may have been enlarged, deformed, or shown in an unconventional or non-proportional way in order to provide a version of the present invention that is easier to understand. When sizes and/or values are specified in the following description, the sizes and/or values are provided for illustrative purposes only and must not be construed as limiting the scope of protection of the present invention, unless these sizes and/or values are present in the attached claims.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

We will now describe some example embodiments, with reference to the attached drawings. These example embodiments are provided by way of illustration of the invention and are not intended as a limitation thereof.

Fig. 1 shows an overall diagram of a machine 100 for the automated production of tubular products A, preferably made of paper, suitable to also form straws, then cutting each tubular product A to size, in any known manner whatsoever. The machine 100 comprises an evaporation apparatus 10, as described in detail below.

Before describing the apparatus 10 in detail and to better understand its function and functioning, we will briefly describe the machine 100, which comprises means 20 for delivering an adhesive substance S containing at least a liquid solvent, and forming means 16 configured to form the tubular product A. It is understood that the machine 100 could be, in particular because of the other components or devices present therein, of any other type whatsoever, whether known or to be developed in the future.

Essentially, the machine 100 can comprise a feed unit 11, configured to rotatably support one or more reels, for example three, 12, 13 and 14, each of which is formed with a corresponding helically wound strip-shaped element B (indicated respectively with Bl, B2 and B3), and a forming unit 15, disposed downstream of the feed unit 11 and configured to form the tubular product A by suitably winding, in a helical manner, the three strip-shaped elements Bl, B2 and B3 onto the forming means 16, which in this specific case comprise a pin, or mandrel 17, disposed along a longitudinal axis X, for example horizontal. The forming unit 15 can be, for example, of the type described in patent application IT 102020000011344 filed by the Applicant.

The machine 100 also comprises a delivery unit 19 provided with the delivery means 20 that are configured to deliver an adhesive substance S containing at least a liquid solvent, selectively on at least one surface of at least one or more strip-shaped elements, for example on two of them, that is, in the example provided here, on a first strip-shaped element Bl and a second strip-shaped element B2, while a third strip-shaped element B3 is guided directly to the forming unit 15 by the corresponding reel 12. First guide means 18, for example consisting of a plurality of first rollers, are disposed between the reels 12, 13 and 14 in order to guide the three strip-shaped elements B in a suitable manner between the feed unit 11 and the forming unit 15, in a first substantially horizontal direction.

Indicatively, the thickness of the adhesive substance S deposited on each stripshaped element Bl and B2 is of the order of micrometers, for example from about 10 pm to about 50 pm.

The theoretical speed V at which the three strip-shaped elements Bl, B2 and B3 should be transferred from their reels 12, 13 and 14 to the forming unit 15 is comprised, for example, between about 1 and 2 m/s, which corresponds to a productivity of the machine 100 of about 60 to 120 m/min of tubular product A. In some cases, the theoretical speed V can reach up to 4 m/s.

In the embodiment shown in figs, from 1 to 4, an apparatus 10 comprises two evaporation units 22, each comprising respective evaporation means configured to selectively remove in a controlled manner, advantageously by evaporation caused by the radiations of the electromagnetic waves as above, at least a part of the liquid solvent contained in the adhesive substance S just deposited on the first strip-shaped element B 1 and on the second strip-shaped element B2 respectively.

In the example provided here, the evaporation means are configured as an antenna 30 (figs. 3 and 4), of a known type and capable of defining a mean for transmitting and/or receiving electromagnetic waves.

In the embodiment described here, the apparatus 10 is configured to simultaneously treat two strip-shaped elements B, but it is clear that it can be sized in order to treat even just one, or more than three of them. In fact, one of the characteristics of the apparatus 10 is modularity and that it can be expanded as desired.

It is therefore quite evident that in other variants in which it is provided to deposit the adhesive substance on all three strip-shaped elements Bl, B2, B3, three evaporation units 22 will be provided. Preferably, in general, it is provided that each evaporation unit 22 interacts with a respective strip-shaped element B.

The evaporation units 22 are disposed between the delivery unit 19 and the forming unit 15 and in particular, preferably, above the delivery unit 19. In this way, in order to reduce the space between the delivery unit 19 and the forming unit 15 and to speed up the production process of the tubular elements A, the evaporation means are disposed between the delivery means 20 and the forming means 16 so that the strip-shaped elements B come into contact with the pin 17 after the adhesive substance S has conveniently dried so as not to overflow from the same strip-shaped elements B and to make the latter adhere well and quickly to each other.

In particular, between the evaporation units 22 and the forming unit 15 there are also second guide means 25, consisting for example of second rollers, which in the example shown guide the strip-shaped elements Bl and B2 for a segment of their path toward the forming unit 15.

Preferably, the evaporation units 22 are disposed in correspondence with a segment of the path of the strip-shaped elements B, in this specific case of the first and second strip-shaped elements Bl and B2, which is disposed substantially parallel to a second substantially vertical direction, indicated by the arrow E in fig. 1, and disposed substantially above the delivery means 19.

Furthermore, each strip-shaped element Bl and B2 is suitably guided so that only its surface without adhesive substance S comes into contact with the guide means 18 and 25, with suitable loop means between one roller and the next, where required.

As shown in fig. 2, the apparatus 10 can comprise a support panel 21 intended to support various members of the apparatus 10 and/or of the machine 100 in which it is installed. By way of a non-limiting example, the support panel 21 can support the shafts on which the rollers that constitute the guide means 18 and 25 are mounted, as well as the delivery unit 19 and/or the evaporation units 22 themselves.

Each evaporation unit 22 preferably has the shape of a cylindrical drum having a lateral wall 24, a lower wall 33, perpendicular to the lateral wall 24, and an upper wall 35, parallel to the lower wall 33.

The three walls 24, 33 and 35 together define an internal chamber 26, in which the antenna 30 is disposed. Preferably, the walls 24, 33 and 35 are made of metal material, so that the internal chamber 26 is electromagnetically isolated from the external environment.

The lower wall 33 is provided with a central through aperture 27, which acts as an inlet aperture into the internal chamber 26 for a corresponding strip-shaped element Bl or B2, while the upper wall 35 is provided with a central through aperture 28, which acts as an outlet aperture from the internal chamber 26 for the same strip-shaped element Bl or B2. In particular, the sizes of the inlet aperture 27 and the outlet aperture 28, in addition to their relative position with respect to the antenna 30, are such as to prevent the escape of electromagnetic waves outside the internal chamber 26 as much as possible.

The positions of each evaporation unit 22 and of their central through apertures 27 and 28 with respect to the underlying delivery unit 19 are such that a corresponding strip-shaped element B can pass through the latter, from bottom to top, advantageously without touching their walls, thus temporarily entering the corresponding internal chamber 26, where the evaporation occurs, as will be described in detail below. In other words, the walls 24, 33 and 35 shield the internal chamber 26 and prevent the electromagnetic waves generated by the antenna 30 from escaping to the outside.

It will be quite clear to the person of skill in the art that the evaporation unit 22 can take many other shapes, such as for example the shape of a prism with a square or rectangular or polygonal base, since all shapes are technically equivalent to the cylindrical one described above.

Advantageously, the sizes of each evaporation unit 22 are very compact. This, in addition to the fact that the evaporation units 22 are disposed above the evaporation unit 19, along a substantially vertical segment of the path of the strip-shaped elements B, allows to take the evaporation unit 19 significantly close to the forming unit 15, so that the machine 100 in which the apparatus 10 is installed can be compact in its overall sizes, especially in length.

Each antenna 30 is connected, outside the internal chamber 26, to suitable devices for transmitting/receiving electromagnetic waves, of any known type whatsoever, or that will be developed in the future, which are neither shown nor described in detail here. For this purpose, an attachment 29 is provided (figs. 2- 4), for example shaped as an “L”, intended to connect each antenna 30 to these devices.

In particular, the antenna 30 is configured to emit and/or receive micro waves, that is, electromagnetic waves comprised in the frequency range between 300 MHz and 300 GHz.

According to some variants, not shown, in each evaporation unit 22 there can be provided two distinct antennas 30, for example one configured to emit electromagnetic waves and the other to receive such waves.

Each evaporation unit 22 also comprises a modulator device 31, which is operatively connected to the corresponding antenna 30 and configured to adjust the intensity of the electromagnetic waves emitted by the latter.

In particular embodiments, the antenna 30 can be a directional antenna, of the type commonly available on the market for emitting microwaves, capable of directing the electromagnetic waves in a localized zone disposed inside the internal chamber 26, for example substantially at the center of the latter.

The apparatus 10 also comprises a central control unit 32, which can be of any known type whatsoever, or which will be developed in the future.

The central control unit 32 can be either the same one that can be present in the machine 100 and that also controls, in a programmed manner, at least the functioning of the forming means 16 and of the delivery means 20, or an autonomous one dedicated only to controlling the evaporation means, that is, the antenna 30 in the example provided here, based on information on the effective speed of advance of the strip-shaped elements B, which is directly proportional to the time that the latter take to pass through the internal chambers 26 of the evaporation units 22, and possibly also based on other parameters, such as for example the temperature and humidity in the location where the apparatus 10 is installed and/or other parameters useful for optimizing the evaporation method.

According to possible embodiments, the apparatus 10 comprises at least one temperature sensor, and/or at least one humidity sensor, not shown and configured respectively to detect the temperature and relative humidity of the environment in which the apparatus is installed 10. In these embodiments, the temperature and humidity sensors are operatively connected to the central control unit 32 in order to communicate to the latter the signals relating to the temperature and humidity values detected. In this case, the central control unit 32 can intervene directly on the modulator device 31 in order to automatically adjust the intensity, or the power, of the electromagnetic waves emitted by each antenna 30 based on the environmental conditions that have been detected by the sensors.

The functioning of the apparatus 10, which also corresponds to the evaporation method, is coordinated with the functioning of the machine 100, that is, the method to make the tubular products A, and advantageously occurs entirely in an automated manner under the control of the central control unit 32.

In an initial step of preparing the machine 100 and the apparatus 10, it is provided to set the functioning operating parameters in the central control unit 32, such as the linear speed of advance of the strip-shaped elements B, the quantity of adhesive substance S to be delivered on them and the thickness of the strip-shaped elements B being worked.

In this initial preparation step, it is provided that an operator adjusts the intensity of the electromagnetic waves emitted by each antenna 30 by acting on the modulator device 31. It is evident that this adjustment will be correlated to the speed of advance of the strip-shaped elements B that has been set, as well as to the quantity of adhesive substance S that has been decided is to be delivered on them, and to their thickness.

Essentially, the functioning of the machine 100 comprises a dragging step in which the strip-shaped elements B 1 , B2, B3 are dragged directly by the forming means 16 which cause them to unwind in a suitable manner from the respective reels 12, 13 and 14, and make each strip-shaped element on which to deposit the adhesive substance S, that is, in the example provided here, the strip-shaped elements Bl and B2, pass first through the delivery unit 19 and then through the apparatus 10, while the third strip-shaped element B3 on which the adhesive substance S must not be deposited by-passes the delivery unit 19 and the apparatus 10.

Simultaneously with the dragging step, a delivery step occurs in the delivery unit 19, in which the delivery means 20 deposit the adhesive substance S on the strip-shaped elements Bl and B2, the delivery step being immediately followed by an evaporation step in the apparatus 10, in which the strip-shaped elements Bl and B2, and therefore the layer of adhesive substance S deposited thereon, are hit by the electromagnetic waves emitted, preferably in a localized manner, by each antenna 30. This allows to remove, by evaporation caused by the radiations of the electromagnetic waves, at least a part of the liquid solvent contained in the adhesive substance, exploiting physical principles which will be well known to a person of skill in the art.

Furthermore, during the functioning, by exploiting the dual functionality of the antenna 30, which allows it to both transmit and also receive the electromagnetic waves, the method according to the present invention provides a step of feedback control of the quantity of adhesive substance S that has been actually deposited on the strip-shaped elements Bl and B2.

This control step provides to analyze the electrical signal characteristic of the electromagnetic waves received by the corresponding antenna 30. In particular, these are the electromagnetic waves previously emitted by the antenna 30 itself which return to the antenna 30 after having hit the strip-shaped elements B. Passing through the strip-shaped elements B, the electromagnetic waves lose part of their intensity, in a manner proportional to the energy that has been absorbed by the adhesive substance S, in particular by the liquid solvent contained therein to cause its evaporation.

This signal is communicated to the central control unit 32, which is configured to compare it with a preset value, correlated to the theoretical quantity of adhesive substance S which, based on the settings entered in the central control unit 32, should have been deposited on the strip-shaped elements B.

The comparison can reveal that an excessive or - on the contrary - low amount of adhesive substance S has been deposited on the strip-shaped elements Bl, B2, if the intensity of the electromagnetic wave that returns to the antenna 30 is respectively lower, or - on the contrary - higher than the preset value as above.

The evaporation apparatus 10 and method described here therefore advantageously also allow to check, in a simple and continuous manner, if the quantity of adhesive substance S that is delivered by the delivery means 20 is as expected. This allows to detect, almost in real time, any deviations from the optimal quantity of adhesive substance that has been set, allowing operators to intervene promptly with suitable corrective measures, and thus avoid wasting non-compliant tubular products A, for example because they have too much or too little glue, with the consequent economic damage that results.

The evaporation step is then followed by a forming step, by the machine 100, in which the three strip-shaped elements B 1 , B2 and B3 are helically wound onto the pin 17 (fig. 1) and simultaneously glued to each other by means of the adhesive substance S interposed between them.

Therefore, based on the above disclosure, it is evident that having the functioning of the evaporation means based on the transmission of electromagnetic waves is very advantageous and allows to achieve surprising results, especially in terms of productivity.

Furthermore, with the apparatus 10 it is possible to program the quantity of liquid solvent contained in the adhesive substance S to be removed by evaporation under the control of the central control unit 32.

It is clear that modifications and/or additions of parts, or steps, may be made to the machine 100, to the apparatus 10 and to the corresponding methods to produce tubular products and for evaporation as described heretofore, without departing from the field and scope of the present invention as defined by the attached claims. In fact, it is understood that the field of protection of the present invention shall include all such modifications and/or additions of parts or steps. It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of machines, apparatuses and methods, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby. In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection defined thereby.