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 its derivatives, 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, by irradiation and/or conduction, the strip-shaped elements on which the adhesive substance has been deposited, in order to remove at least a part of the liquid solvent by means of the Joule effect, 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, US 1.698.260 A and FR 2.303.663 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 apparatus, 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 apparatus 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.

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, the embodiments concern a machine to make tubular products, preferably straws, using one or more strip-shaped elements, preferably made of paper or its derivatives or suchlike. The machine comprises delivery means configured to selectively deliver on at least one surface of at least one 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 as above also comprises an evaporation apparatus comprising a plurality of heating elements for each of the strip-shaped elements as above; each of these heating elements has one or more electric resistances and is configured to selectively remove, by evaporation, at least a part of the liquid solvent contained in the adhesive substance.

In accordance with another aspect, the electric resistances are mounted on each of the heating elements as above; these elements being configured to heat, preferably by irradiation and/or conduction, directly or indirectly, the adhesive substance to cause the at least partial evaporation of the liquid solvent.

In accordance with another aspect, each of the heating elements as above is mobile between an idle position, in which it is located at a determinate distance from the strip-shaped elements, and an operating position, in which it is in contact with, or in the proximity of, the strip-shaped elements, or vice versa, preferably keeping the one or more electric resistances mounted on it energized.

In accordance with another aspect, the evaporation apparatus also comprises adjustment means associated with the heating elements and configured to selectively adjust the quantity of thermal energy transmitted to the adhesive substance, by acting selectively on the distance of the heating elements from the strip-shaped elements on which the adhesive substance is present, in order to vary their distance from the strip-shaped elements, between the operating position and the idle position.

In accordance with some embodiments of the present invention, the adjustment means act on the current intensity and/or on the energizing time, with which each of the electric resistances is energized.

In accordance with another aspect, the adjustment means comprise a central control unit and actuation means controlled thereby; moreover, the actuation means are configured to selectively move each of the heating elements from the idle position to the operating position, and vice versa.

In accordance with another aspect, the heating elements are preferably disposed in correspondence with a surface of the strip-shaped elements opposite to that on which the adhesive substance is present.

In accordance with another aspect, there is provided at least one heating element for each of the strip-shaped elements on which the adhesive substance is present; moreover, if there is more than one strip-shaped element on which the adhesive substance is present, correspondingly there is also more than one heating element.

In accordance with another aspect, for each of the strip-shaped elements on which the adhesive substance is present there are preferably at least two heating elements, more preferably at least three heating elements and even more preferably at least four heating elements; moreover, the heating elements associated with each of the strip-shaped elements on which the adhesive substance is present are aligned with each other parallel to the corresponding strip-shaped element.

In accordance with another characteristic aspect, the evaporation apparatus is preferably disposed between the delivery means and the forming means of the machine.

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 its derivatives, comprising a delivery step, in which delivery means selectively deliver on at least one surface of at least one 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 as above also comprises an evaporation step in which a plurality of heating elements for each of the stripshaped elements, each having one or more electric resistances, are selectively activated in order to remove, by evaporation, 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 or its derivatives or suchlike, wherein the machine itself is provided with delivery means configured to selectively deliver on at least one surface of at least one 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 heating elements, each having one or more electric resistances, and configured to selectively remove, by evaporation, at least a part of the liquid solvent contained in the adhesive substance present on at least one of the strip-shaped elements.

In accordance with another aspect of the invention, 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 one or more heating elements, each having one or more electric resistances, are selectively activated in order to remove, by evaporation, 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, in the evaporation step as above there is a heating, preferably by irradiation and/or conduction, directly or indirectly, of the adhesive substance by the heating elements.

According to some embodiments, which can be combined with all the embodiments described here, an adjustment step can also be provided, in which adjustment means associated with each of the heating elements selectively adjust the quantity of thermal energy transmitted to the adhesive substance, varying the distance of each of the heating elements from the strip-shaped elements on which the adhesive substance is present. The adjustment step provides to alternatively take each heating element of the plurality of heating elements to an idle position, in which it is located at a determinate distance from the one or more strip-shaped elements, or to an operating position, in which it is in contact with, or in the proximity of, the strip-shaped elements.

According to some embodiments, the adjustment step comprises a step of controlled energizing of the electric resistances, in which the adjustment means, in addition to acting selectively on the distance of each of the heating elements from the strip-shaped elements, also act on the current intensity and/or on the energizing time with which each of the electric resistances is energized.

According to some embodiments, which can be combined with all the embodiments described here, the evaporation means are part of an evaporation apparatus, which at least during the evaporation step as above is stationary in a determinate position. In the evaporation step as above, the strip-shaped elements on which the adhesive substance is present pass through the evaporation apparatus, in front of the heating elements, at a determinate effective speed of advance. The step of controlled energizing of the electric resistances as above occurs as a function of the effective speed of advance.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of 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 ;

- fig. 3 is another schematic perspective view of the apparatus of fig. 1, in which some parts have been removed in order to show its interior;

- fig. 4 is a left lateral view of the part of the apparatus of fig. 3;

- fig. 5 is a front view of the part of the apparatus of fig. 3.

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 examples of embodiments, which refer to the attached drawings. These examples are provided by way of illustration of the invention and are not intended as a limitation thereof.

Fig. 1 shows a diagram in which there is a machine 100 for the automated production of tubular products A, preferably made of paper, also suitable to 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 in order 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 in relation to 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 strip-shaped element B (indicated respectively with Bl, B2 and B3) wound in a spiral, and a forming unit 15, disposed downstream of the feed unit 11 and configured to form the tubular product A by appropriately 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 which are configured to selectively deliver on at least one surface of at least one or more strip-shaped elements, for example on two of them, B 1 and B2, an adhesive substance S containing at least a liquid solvent, while a third stripshaped element B3 is guided directly by the corresponding reel 12 to the forming unit 15. 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 stripshaped elements B in an appropriate 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 of advance 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 for example comprised 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 speed of advance V can reach up to 4 m/s.

The apparatus 10 comprises evaporation means 23, which are configured to selectively remove, in a controlled manner, by evaporation caused by a heat source, at least a part of the liquid solvent contained in the adhesive substance S deposited on the strip-shaped elements B, in the example provided here Bl and B2, before the latter cooperate with the forming means 16.

The evaporation means 23, which will be described in detail below, are disposed inside a box-like body 25 (fig. 2) having a fixed part 26, hollow internally and without upper and lower walls. A closing door 27 is hinged on the fixed part 26 and can be selectively opened by means of a handle 28. The boxlike body 25 has an oblong shape and is disposed in a substantially vertical direction, preferably above the delivery unit 19, that is, functionally between the latter and the forming unit 15. This has the advantage, among other things, of reducing the space in the horizontal direction between the delivery unit 19 and the forming unit 15, and of speeding up the production process of the tubular element A.

Inside and above the box-like body 25 there are second guide means 29 positioned so as to guide the strip-shaped elements Bl and B2 between the delivery means 23 along a segmented path (fig. 5) which is disposed parallel, or slightly arched, with respect to the second substantially vertical direction mentioned above.

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 29, with suitable loop means between one roller and the next, where required.

In other words, the evaporation means 23 (fig. 1) are functionally disposed between the delivery means 20 and the forming means 16, that is, immediately downstream of the delivery means 20 and upstream of 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 in order to not overflow from the strip-shaped elements B and make the latter adhere to each other well and quickly.

According to one aspect, the heat source as above comprises heating means, configured as one or more heating elements 30, in each of which there is inserted an electric resistance 31 of a known type and schematically shown in fig. 5.

Some embodiments can provide that the heating elements 30 consist of, or comprise, heating lamps, for example infrared.

Each electric resistance 31 can be energized selectively and in an adjustable manner under the command of 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 controls, in a programmed manner, at least also the functioning of the forming means 15 and of the delivery means 19, or an autonomous one dedicated only to the control of the evaporation means 23, on the basis of information on the effective speed of advance VN of the strip-shaped elements B and possibly also of 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 the optimization of the evaporation process.

The same central control unit 32 is configured to selectively adjust the quantity of thermal energy transmitted by the heating elements 30 to the adhesive substance S present on each strip-shaped element B, for example by acting selectively on the distance of each of the heating elements 30 from the corresponding strip-shaped element B on which the adhesive substance S is present, or on the current intensity and/or on the energizing time with which each of the electric resistances 31 is energized.

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 three or even more. In fact, one of the characteristics of the apparatus 10 is modularity and that it can be expanded as desired.

In the specific embodiment described here, there are eight heating elements 30 and these are divided into four groups, respectively 30A, 30B, 30C and 30D (figs. 3 and 4), which are disposed vertically aligned and slightly spaced apart; moreover, each group is formed by two heating elements 30 aligned horizontally, that is, one for each of the two strip-shaped elements Bl and B2.

Therefore, each strip-shaped element B can be affected by a variable number of heating elements 30, for example from one to four, as will be described in detail below.

In particular, all the heating elements 30 face the surface of the strip-shaped elements B 1 and B2 opposite to that on which the adhesive substance S has been deposited.

Furthermore, each of the four groups of heating elements 30 A, 30B, 30C and 30D (figs. 4 and 5) is selectively mobile between an idle position, in which it is moved away from the strip-shaped elements Bl and B2 by a determinate distance, for example of a few tens of millimeters, and an operating position, in which it is in contact with, or in the proximity of, the strip-shaped elements Bl and B2, or vice versa.

The movement of each group of heating elements 30 A, 30B, 30C and 30D between the idle and the operating positions is carried out by a corresponding actuator 33, that is, 33A, 33B, 33C and 33D respectively (figs, from 2 to 5), for example of the pneumatic type, which is known, commanded individually by the central control unit 32.

However, some embodiments may provide that each of the heating elements 30 can be driven autonomously and can be commanded by a corresponding actuator 33 driven by the central control unit 32.

The functioning of the apparatus 10, which also corresponds to the evaporation method described here, 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 particular, in an initial idle condition the electric resistances 31 of the heating elements 30 are not energized and the latter are in their idle position.

Essentially, the functioning of the machine 100 comprises a dragging step in which the strip-shaped elements Bl, B2, B3 are dragged directly by the forming means 16 which make them suitably unwind 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 does not have to be deposited by-passes the delivery unit 19 and the apparatus 10.

At the beginning of the dragging step, all the electric resistances 31 of the heating elements 30 are energized, but the latter are selectively taken from their idle position to their operating position only under certain conditions, as explained below.

The theoretical speed of advance V of the strip-shaped elements B is determinate a priori, as a function of the productivity to be achieved, as explained above, and is stored in a memory associated with the central control unit 32. In particular, in this memory three speed of advance thresholds are stored, respectively VI, V2 and V3, wherein the first threshold VI is the lowest speed of advance of the three and the third threshold V3 is the highest speed of advance of the three.

Speed sensors of a known type and not shown in the drawings are able to detect the effective speed of advance VN of the strip-shaped elements B and to communicate it to the central control unit 32.

At the same time as 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 B 1 and B2, such delivery step being immediately followed by an evaporation step in the apparatus 10, in which the evaporation means 23 make at least a part of the liquid solvent contained in the adhesive substance S just deposited on the same strip-shaped elements B 1 and B2 evaporate. Specifically, in a first operating condition, shown in fig. 5, when the effective speed of advance VN of the strip-shaped elements B, detected by the speed sensors, is lower than the first speed of advance threshold V 1 , the central control unit 32 only commands the actuation of the actuator 33A so that only the first group of heating elements 30 A, for example the lowest one, is taken from the idle position to the actuation position, while the other three groups of heating elements 30B, 30C and 30D remain in their idle position, but with the their electric resistances 31 energized.

In a second operating condition, not shown in the drawings, when the effective speed of advance VN of the strip-shaped elements B, detected by the speed sensors, is greater than that of the first speed of advance threshold VI, but lower than that of the second speed of advance threshold V2, then the central control unit 32 also commands the actuation of the actuator 33B so that in addition to the first group of heating elements 30 A, the second group of heating elements 30B is also taken from the idle position to the actuation position, while the other two groups of heating elements 30C and 30D remain in their idle position, but with their electric resistances 31 energized.

In a third operating condition, not shown in the drawings, when the effective speed of advance VN of the strip-shaped elements B, detected by the speed sensors, is greater than that of the second speed of advance threshold V2, but lower than that of the third speed of advance threshold V3, then the central control unit 32 also commands the actuation of the actuator 33C so that in addition to the first group of heating elements 30A and to the second group of heating elements 30B, the third group of heating elements 30C is also taken from the idle position to the actuation position, while the fourth group of heating elements 30D remains in its idle position, but with the corresponding electric resistances 31 energized.

Finally, in a fourth operating condition, shown in fig. 3, when the effective speed of advance VN of the strip-shaped elements B, detected by the speed sensors, is greater than that of the third speed of advance threshold V3, then the central control unit 32 also commands the actuation of the actuator 33D so that the fourth group of heating elements 30D is also taken from the idle position to the actuation position, so that all the heating elements 30 contribute to effect the evaporation of the adhesive substance S.

The central control unit 32 will correspondingly command, in an inverse manner, the actuators 33, if the effective speed of advance VN of the strip-shaped elements B falls below each of the three speed of advance thresholds VI, V2 or V3.

It should be noted that, advantageously, the central control unit 32, by controlling the actuators 33 in the manner described above, allows to adjust the quantity of thermal energy transmitted by the heating elements 30 to the stripshaped elements B without having to frequently energize/de-energize the electric resistances 31 , even if, as an alternative to the selective movement of the heating elements 30, the adjustment of the quantity of thermal energy as above could be carried out in another way, for example by adjusting the current intensity and/or the energizing time with which each of the electric resistances 31 is energized. However, it has been experimented that this last mode of adjusting the quantity of thermal energy delivered involves generating thermal inertias which are difficult to manage, taking into account that, in general, the electric resistances require a certain amount of time, sometimes relatively long, to cool down.

In addition, also for safety reasons, regardless of the adjustment mode adopted, a temperature sensor or a thermocouple, of a known type and not shown in the drawings, can be installed in the apparatus 10 in order to signal to the central control unit 32 when a determinate threshold temperature, which can be set when setting up the apparatus 10, has been exceeded, in order to possibly stop the entire machine 100 or deactivate one or more heating elements 30 or deenergize one or more electric resistances 31.

Furthermore, again for safety reasons, the central control unit 32 is programmed to block the energizing of the electric resistances 31 if a sensor associated with the closing door 27 detects that the latter has been opened, even inadvertently or accidentally.

The evaporation step is then followed by a forming step, carried out by the machine 100, in which the three strip-shaped elements Bl, B2 and B3 are wound on the pin 17 (fig. 1) in a helical manner, for example in the winding sense R, and at the same time are glued together by means of the adhesive substance S interposed between them. Therefore, based on what described above, it is evident that having the evaporation means 23 based on heating means that have one or more electric resistances is very advantageous and allows to obtain surprising results.

Furthermore, with the apparatus 10 it is possible to program and control, even instantly, 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 of steps, may be made to the machine 10, to the apparatus 100 and to the corresponding methods to make tubular products and of 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 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 claimed in the specific claims.