Cutting unit for thermoplastic pipe

Abstract

The present disclosure describes a cutting unit (1) for thermoplastic tubulars (T) comprising a ring (2) rotating about an axis of rotation (X) and in which the tubulars (T) are progressively moved in a sliding manner, so that the longitudinal axis of the tubulars (T) coincides with the axis of rotation (X), and at least one cutting arm (3) mounted on the rotating ring (2). The cutting unit (1) also comprises at least one distance measuring sensor (4) located on the rotating ring (2) and configured to acquire, during the rotation of the rotating ring (2), a plurality of values representative of the radial distance between the at least one measuring sensor (4) and the outer surface (S) of the tubulars (T). The distance is measured on a measurement plane (M) transverse, in particular perpendicular, to the axis of rotation (X). The cutting unit (1) also comprises a processing and control unit (5) operatively connected to the at least one measuring sensor (5) and configured to receive the plurality of values representative of the measurements and configured to calculate, on the basis thereof, at least one parameter related to the peripheral profile of the tubulars (T) on the measurement plane (M).

Description

TECHNICAL FIELD

[0001] The present invention relates to a unit for cutting a tubular element made of thermoplastic material.

[0002] In particular, the present invention relates to a unit for cutting a tubular element made of thermoplastic material, which can be preferably used in an automatic cutting machine designed for cutting tubular elements of large diameter and / or large thickness, such as, for example, tubular elements made of polyolefin material, for the manufacture of tubular elements for the transport of fluids even under pressure (typically water or gas) and in general for the design of tubular elements for the manufacture of, for example, water supply and / or sewer pipes in construction works, sewage networks, drinking water distribution networks. BACKGROUND

[0003] In systems for the production of tubular elements made of thermoplastic material, the automatic cutting machine is generally aligned with the extrusion station that produces the continuous tubular element, more specifically downstream of the latter.

[0004] The automatic cutting machine generally has a cutting unit equipped with one or more cutting tools for making cuts on the tubular element being extruded and generating a plurality of workpieces of predetermined length in sequence.

[0005] Typically, the cutting unit has a ring, on which the cutting tools are mounted, which is movable in rotation around the tubular element.

[0006] Typically, according to the preferred embodiment, during the cutting step, the cutting unit moves in synchronism with the feed of the tubular element along the longitudinal axis thereof. During the cutting step, the cutting tools are radially fed until they come into contact with the tubular element to penetrate the thickness. At the same time, the movable ring rotates around the axis of the tubular element so that the cutting tools can make a complete circumferential cut in one or more consecutive rotations, thus forming a piece of tubular element.

[0007] Once the cut has been completed, the cutting tools are moved radially away from the tubular element so that there is no longer contact between the cutting tools and the profile of the tubular element.

[0008] It is known that, due to the fact that it has not yet completely solidified, the tubular element during the extrusion process generally tends to deviate from the cylindrical shape set by the extruder due to the effect of its own weight and preferably adopts a shape with an elliptical cross-section. The above-mentioned phenomenon increases significantly as the diameter and the relative thickness dimensions of the tubular element increase. The elliptical shape assumed by the tubular element under the action of gravity generally has a major semi-axis positioned horizontally, while the minor semi-axis is positioned vertically.

[0009] Generally, in the cutting units of the prior art, during the setting step preceding the start of extrusion, the operator who controls the cutting machine sets the machine with reference to the nominal diameter of the pipe that must be extruded. In particular, the cutting tool is designed for cutting a reference diameter, then the cutting unit is actuated. Since the movable ring in which the cutting tool is installed has a circular cross section, while, as already mentioned, the pipe can have a more or less elliptical cross section, during the rotation of the movable ring around the pipe, there is the risk that the cutting tool does not make correct contact with the entire profile of the pipe in the cutting section, tracing a substantially circular trajectory of said tool. In fact, when the cross section of the pipe is generally elliptical, there are some points in which the cutting tool can exert an excessive cutting action on the section of the pipe (mechanical stresses on the cutting unit and on the pipe are generated, also an inaccurate cut is generated), while on the other hand, in other points the penetration will not be as expected, so that the cut can not be completed.

[0010] The prior art presents cutting units that can define the maximum diameter and the minimum diameter of the pipe to be extruded (measurements performed during the process are not simple), so that, in principle, an assumed elliptical shape of the pipe can be obtained.

[0011] Disadvantageously, these cutting units also have drawbacks in terms of precision and versatility.

[0012] In fact, said cutting units adopt an ellipse, whose origin is the maximum and minimum diameter inserted, generally having a major semi-axis positioned horizontally (parallel to the ground) and a minor semi-axis positioned vertically (perpendicular to the ground).

[0013] However, if the cross section of the pipe does not have a completely elliptical cross section, with the major semi-axis positioned horizontally and the minor semi-axis positioned vertically, or more generally adopts a non-circular cross section, but even a shape that is not completely elliptical, for example due to the presence of grooves or protrusions, the cutting tool will in any case be positioned and moved incorrectly with respect to the actual section to be cut.

[0014] In fact, as already described, if the extrapolated or assigned point of the cross section is smaller with respect to the distance of the corresponding point of the actual cross section of the pipe from the axis of the pipe, the cutting tool will move excessively towards the cross section to be cut, giving it an action greater than expected, which can have a negative impact on the integrity of the structure and / or cause the creation of burrs, scratches on the pipe or damage to the cutting tool. On the other hand, if the extrapolated or assigned point of the cross section is greater with respect to the distance of the corresponding point of the actual cross section of the pipe from the axis of the pipe, the cutting tool will not be able to move close enough to the pipe and there is the risk of not being able to completely penetrate its thickness, creating an incomplete cut and causing the pipe to be rejected.

[0015] The technical purpose of the present application is therefore to provide a unit and a method for cutting thermoplastic pipes that overcomes the drawbacks of the prior art. SUMMARY

[0016] The purpose of the present application is therefore to provide a cutting unit of thermoplastic pipes that is able to make precise cuts of the pipes, regardless of the shape of the cross section of the pipes in the cutting plane.

[0017] A further purpose of the present application is therefore to provide a unit for cutting thermoplastic pipes and a reliable, precise and simple method that does not require the operator to measure the actual dimensions of the pipes.

[0018] The indicated technical purpose and the specified aims are substantially achieved by a unit for cutting thermoplastic pipes and by a method comprising one or more of the technical characteristics described in the attached claims. The dependent claims correspond to possible embodiments of the application.

[0019] In particular, the indicated technical purpose and the specified aims are achieved by a cutting unit of thermoplastic pipes comprising a ring rotating around an axis of rotation, in which the pipe is progressively moved in sliding manner so that the longitudinal axis of the pipe coincides with the axis of rotation. The cutting unit according to the present application further comprises at least one cutting arm mounted on the rotating ring and equipped with a cutting tool and having a relative portion integrated with the rotating ring. The cutting arm can also be moved between an operating position, in which the cutting tool engages the pipe to apply the cutting action, and a rest position, in which the cutting tool is disengaged from the pipe. The cutting unit according to the present application further comprises at least one distance measuring sensor located on the rotating ring and configured for acquiring, during the rotation of the rotating ring, a plurality of representation values representing the radial distance between the at least one distance measuring sensor and the outer surface of the pipe. This radial distance is measured on a measurement plane transverse, in particular perpendicular, to the axis of rotation.

[0020] In the case of a single distance measuring sensor, the rotation is a full rotation; in the case of two or more distance measuring sensors, the rotation can also be partial (for example, with 2 sensors, the rotation can be only 180°).

[0021] Preferably, the distance is measured on the cutting plane, that is, on the plane in which the cutting element is operatively active.

[0022] The cutting unit further comprises a processing and control unit operatively connected to the at least one distance measuring sensor and configured to receive the plurality of representation values representing the measured values and configured for calculating, on the basis of the measured representation values, at least one parameter relating to the peripheral profile of the pipe on the measurement plane.

[0023] In other words, the ranging sensor can scan the outer surface of the pipe in the area where the cut must be made, thus deriving the actual profile of the pipe in that area.

[0024] Advantageously, the possibility of obtaining the actual profile of the pipe in the cross section where the cut must be made allows to adjust and move the components of the cutting unit, in particular the cutting tool, so as to make a clean and precise cut at each point of the cross section.

[0025] Advantageously, since the actual cross section of the pipe can be reconstructed, it is possible to detect the presence of defects (for example protrusions, grooves and surface irregularities) of the pipe in the area where the cut must be made, thus setting the movement of the cutting tool according to the profile measured, thus guaranteeing the best penetration for any type of cross section and avoiding the application of excessive stresses on the pipe or on the cutting unit.

[0026] Further features and advantages of the present application will become more apparent in the course of the following non-limiting description, which is a non-exclusive embodiment of the cutting unit and method of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] The following description is made with reference to the drawings, which are merely intended to illustrate the present application and not to limit the scope thereof, in which:

[0028] - Figure 1A and 1B respectively show a perspective view of a cutting unit according to the present application, with the frame mounted on the cutting unit and with the frame removed;

[0029] - Figure 2 is a front view of a cutting unit according to the present application;

[0030] - Figures 3A-3C shows a series of front views of the cutting unit in use;

[0031] - Figure 4 is a front view of a further embodiment of a cutting unit according to the present application. DETAILED DESCRIPTION

[0032] With reference to the drawings, the number 1 indicates a cutting unit of a thermoplastic pipe "T", configured to obtain a piece of pipe "T" starting from a continuous pipe "T".

[0033] The cutting unit 1 can be inserted into an automatic cutting machine (not shown) in a system for shaping the pipe "T" made of thermoplastic material, so as to make a predetermined measurement starting from a continuous pipe "T" coming from an extrusion station (not shown).

[0034] As Figure 1AAs shown, the cutting unit 1 includes a frame 8 and one or more clamps 8a and 8b, which are configured to constrain the pipe fitting "T" to the cutting unit 1 in such a way that the longitudinal axis of the pipe fitting "T" coincides with the rotation axis "X".

[0035] Preferably, the frame 8 can move according to the alternating sliding movement of the guide rail 8c parallel to the axis of rotation "X", so that the cutting unit 1, which is normally in the standby position, can accelerate along the axis of rotation "X", reach the cutting area in question, and continue to move as a whole with the pipe "T" during the cutting operation, and then return to the starting position when they are finished.

[0036] In practice, the clamps 8a and 8b are configured to constrain the cutting unit 1 to the pipe fitting "T", allowing the cutting unit 1 to move integrally with the pipe fitting "T" in a sliding mode during the cutting operation. More specifically, to perform the cutting operation, the clamps 8a and 8b are fastened around the pipe fitting "T", causing the frame 8 and the entire cutting unit 1 to slide together with the pipe fitting "T" along the rotation axis "X" in the feeding direction of the pipe fitting "T". Once the cutting operation is completed, that is, once the finished pipe fitting "T" is obtained, the clamps 8a and 8b are opened, and the cutting unit 1 slides in the opposite direction to the feeding direction of the pipe fitting "T" to return to the starting position and perform a new operation on the pipe fitting "T".

[0037] like Figure 1B As shown, the cutting unit 1 also includes a rotating ring 2 that rotates around the rotation axis "X", wherein the pipe fitting "T" to be cut moves gradually in a sliding manner with the longitudinal axis of the pipe fitting "T" coinciding with the rotation axis "X". Preferably, the rotating ring 2 is located between the clamps 8a and 8b and inserted into the frame 8.

[0038] For example again Figure 2 As shown, the cutting unit 1 also includes at least one cutting arm 3 mounted on the rotating ring 2, which is equipped with a cutting tool 3a and has a related part 3b integrated with the rotating ring 2.

[0039] Preferably, the cutting tool 3a is a circular inert blade, which cuts the pipe "T" by separating the material.

[0040] According to a further possible embodiment (not shown), the cutting tool 3a is made in the form of a fixed blade or a circular motor-driven blade.

[0041] As shown in the attached figure, the cutting arm 3 can move between an operating position and a stationary position. In the operating position, the cutting tool 3a engages with the pipe fitting "T" to apply a cutting action on the pipe fitting "T", while in the stationary position, the cutting tool 3a disengages from the pipe fitting "T".

[0042] Preferably, the cutting arm 3 moves the cutting tool 3a between the operating position and the rest position at right angles to the rotation axis "X" on the cutting plane, and vice versa.

[0043] More preferably, the cutting arm 3 moves the cutting tool 3a by means of an actuator mounted on the rotating ring 2.

[0044] In other words, as shown in Figures 3A-3C respectively, in the operating position the cutting tool 3a first comes into contact with the outer surface "S" of the pipe "T" and then penetrates its thickness by applying a cutting action to separate the piece of pipe "T" from the continuous pipe "T", while in the rest position the cutting tool 3a is distanced from the pipe "T" and does not come into contact with it in any way.

[0045] Therefore, in use, in an initial step the pipe "T" is slid forward along the direction defined by the rotation axis "X" inside the rotating ring 2. According to the cutting command, the frame 8 starts advancing, reaching and synchronizing with the section to be cut. In this case, the tongs 8a, 8b are activated to close to constrain the cutting unit 1 to the pipe "T", guaranteeing that the latter moves forward as a whole with the pipe "T" during the entire cutting process. After activation of the tongs 8a, 8b to close, the cutting arm 3 moves from the rest position to the operating position to apply the cutting action on the pipe "T". When the cutting arm 3 is in the operating position, the rotating ring 2 makes one or more rotations around the pipe "T" so that the cutting tool 3a gradually makes a circumferential cut on the pipe "T" (cutting that occurs by sinking the cutting tool 3a into the thickness of the pipe "T") and separates the piece of pipe "T" from the continuous pipe "T". At the end of the cutting operation, the cutting arm 3 (and therefore the cutting tool 3a) returns to the rest position and the tongs 8a, 8b release the cutting unit 1 from the pipe "T" so that the latter can freely slide along the guide 8c in the direction opposite to the feed of the pipe "T" to reposition and be able to perform a new cutting operation.

[0046] According to a possible embodiment, as shown in Figure 4 , the cutting unit 1 comprises two cutting arms 3, which are preferably positioned in diametrically opposite positions with respect to the rotating ring 2 and also simultaneously act on the pipe "T" to perform the cutting action. Preferably, each cutting arm 3 is moved between the operating position and the rest position simultaneously. More preferably, according to this embodiment, one contact element 7a of the contact arm 7 has a smaller size than the cutting tool 3a of the other cutting arm 3.

[0047] Advantageously, the presence of the cutting arm 3 and of the contact arm 7 is generally used for particularly large thicknesses of the tubular, in which a first portion of thickness is cut by the contact element 7a with a smaller but more solid extension, creating a first precise recess therein, then the cutting tool 3a (which must have larger dimensions in order to be able to handle the entire thickness, but which is thereby more flexible) is guided until the cutting is completed, which will be without misalignments or deviations. The simultaneous action of the two tools then accelerates the overall cutting action, thereby increasing the production rate of the entire cutting unit.

[0048] As shown in the accompanying drawings, the cutting unit 1 according to the present application comprises at least one distance measuring sensor 4. Figure 2

[0049] The distance measuring sensor 4 can preferably be chosen among laser sensors or ultrasonic sensors, but this does not limit the scope of the present application. The distance measuring sensor 4 is located on the rotating ring 2 (i.e. is supported as a whole by the rotating ring 2) and is configured for acquiring, during the rotation of the rotating ring 2, a plurality of representation values representative of the radial distance between the distance measuring sensor 4 and the outer surface "S" of the tubular "T". The radial distance is measured on a measurement plane "M" transverse, in particular perpendicular, to the rotation axis "X".

[0050] Preferably, the measurement plane "M" on which the distance measuring sensor 4 measures the radial distance coincides with the cutting plane on which the cutting tool 3a of the cutting arm 3 acts.

[0051] Advantageously, in this case the measurement of the radial distance by the distance measuring sensor 4 occurs exactly on the same plane on which the subsequent cutting by the cutting tool 3a takes place, to make the cutting unit 1 accurate and reliable.

[0052] The cutting unit 1 further comprises a processing and control unit 5, which is operatively connected to the distance measuring sensor 4 and is configured for receiving the measured plurality of representation values, and is configured for calculating at least one parameter representative of the peripheral profile of the tubular T on the measurement plane M, based on the above-mentioned measured representation values.

[0053] Preferably, the processing and control unit 5 is positioned on the rotating ring 2.

[0054] Preferably, the unit comprises an actuator of said cutting arm 3 for moving said cutting tool 3a between an operating position and a rest position. The processing and control unit 5 is operatively connected to the actuator of the cutting arm 3 for moving the cutting tool 3a (towards and away from the tubular) as a function of said parameter representative of the peripheral profile of said tubular T on said measurement plane M, which is derived on the basis of the representation values representative of the radial distance acquired by the distance measuring sensor 4.

[0055] ​According to a further aspect, the processing and control unit 5 is configured to send to the actuators of the cutting arm 3 a signal of movement towards or away from said pipe T according to a comparison between the value measured by the first sensor 6a (located at the cutting tool 3a) and an expected positioning value, calculated from the values representative of the radial distance acquired by the ranging sensor 4.

[0056] According to a further possible embodiment, not shown, the processing and control unit 5 is positioned on a portion of the frame 8.

[0057] In use, once the tongs 8a, 8b have been clamped, before the actual cutting operation is performed by means of the cutting tool 3a, the rotating ring 2 is rotated around the pipe "T" so that the ranging sensor 4 can measure the radial distance of several points of the outer surface "S" of the pipe "T" on the measurement plane "M" to obtain a plurality of values representative of the radial distance of the respective points.

[0058] In this case, the values representative of the radial distance of the respective points are sent to the processing and control unit 5, which processes them, thus obtaining the trend of the actual peripheral profile of the cross section of the pipe "T" lying on the measurement plane "M". Once the actual peripheral profile assumed by the pipe "T" has been acquired (and preferably the entire profile) on the measurement plane "M", the cutting tool 3a is moved from the rest position to the cutting position on the cutting plane (which, according to the embodiment shown in the figures, coincides with the measurement plane "M"). In this case, the cutting tool 3a (which rotates around the pipe when mounted on the rotating ring 2) penetrates gradually into the pipe "T" according to the trend of the profile acquired, in such a way that a (calibrated) circumferential cut is always performed on the pipe "T" for separating the piece of pipe "T" from the rest of the continuous pipe "T".

[0059] Therefore, the possibility of measuring the actual circumferential profile of the pipe "T" on the measurement plane "M" is advantageous and allows an accurate cutting operation to be performed even in the case of non-elliptical cross sections and / or in the presence of defects such as grooves or recesses, etc. In fact, in this case, by knowing the actual shape of the profile of the pipe "T" in the measurement plane "M", it is possible to move and adjust the cutting tool 3a so that it is always in the required position with respect to the pipe "T", thereby exerting the correct cutting action on each point thereof.

[0060] Advantageously, the possibility of detecting the actual cross section of the pipe "T" lying on the measurement plane "M" allows an accurate and calibrated cutting operation to be performed with any shape of cross-sectional profile assumed by the pipe "T" in the measurement plane "M", without the need for operator intervention to compensate for any defects or lack of roundness of the pipe.

[0061] Advantageously, the fact that the measurement plane "M" coincides with the cutting plane makes it possible to know the actual shape of the cross-section on which the cutting tool 3a must act, thus allowing the cutting tool 3a to move in a more precise manner during the rotation of the rotating ring 2, preventing the risk of applying too much or too little penetration force on the tubular element "T".

[0062] According to a preferred embodiment, the cutting unit 1 also comprises a first sensor 6a, as previously described, located on the cutting tool 3a and configured to acquire, at different angular positions of the cutting tool 3a, a plurality of values measured on the measurement plane "M" representing the distance between the cutting tool 3a and the outer surface "S" of the tubular element "T". In this case, the processing and control unit 5 is also configured for receiving and processing these representation values and for performing, in the respective angular positions, a comparison with the parameter relating to the peripheral profile. The processing and control unit 5 is also configured to send to the cutting tool 3a a signal for moving towards or away from the tubular element "T" according to the values measured by the first sensor 6a, if the distance measured by the first sensor 6a deviates from the expected distance.

[0063] In use, once the profile of the tubular element "T" on the measurement plane "M" has been acquired by means of the ranging sensor 4, the cutting arm 3 is moved so as to position itself as if it had to perform a cut of the tubular element "T" on the measurement plane "M" having a diameter equal to the maximum diameter measured by the ranging sensor 4. During the rotation of the rotating ring 2, the first sensor 6a is activated so as to acquire, at different angular positions of the cutting tool 3a, a plurality of values representing the actual radial distance between the cutting tool 3a and the outer surface "S" of the tubular element "T", measured on the measurement plane "M". For each angular position, the respective representation value is sent to the processing and control unit 5, which processes the representation value, in particular comparing it with the parameter relating to the peripheral profile in the respective angular position. By means of this comparison, it is possible to understand whether the actual position of the cutting tool 3a at each angular position is correct with respect to the actual profile of the tubular element "T" on the cutting plane. In fact, if it is necessary to correct the position of the cutting tool 3a with respect to the peripheral profile determined by the ranging sensor 4, the processing and control unit 5 can send to the actuators that move the cutting arm 3, and therefore the cutting tool 3a, a signal for moving towards or away from the tubular element "T" according to the values measured by the first sensor 6a.

[0064] In other words, the first sensor 6a allows a closed control to be performed during the cutting operation, so that the cutting arm 3 always positions the cutting tool 3a at the best distance with respect to the actual profile of the outer surface "S" of the tubular element "T" for each angular position assumed by the cutting tool 3a during the rotation of the rotating ring 2.

[0065] In other words, during the rotation of the rotating ring 2, the cutting arm 3 moves on the measurement plane "M" towards or away from the outer surface "S" of the tubular element "T" based on the comparison between the data provided by the first sensor 6a and the data acquired thanks to the ranging sensor 4, thus "following" the actual profile assumed by the tubular element "T" in the measurement plane "M".

[0066] According to a preferred embodiment, as shown in the example of Figure 2 According to the application, the cutting unit 1 also comprises at least one contact arm 7, equipped with a contact element 7a for the tubular element "T" and having a relative portion 7b integral with the rotating ring 2.

[0067] Preferably, the contact arm 7 is mounted on the rotating ring 2 in such a way that it is diametrically opposite the cutting arm 3.

[0068] Preferably, the contact element 7a is mainly located on the measurement plane "M".

[0069] In use, when the rotating ring 2 rotates so that the cutting tool 3a cuts the tubular element "T" to perform the separation, the contact arm 7 also moves so that the contact element 7a comes into contact with a portion of the outer surface "S" of the tubular element "T" which is opposite the portion operated on by the cutting tool 3a. Since both arms are integrated with the rotating ring 2, when the cutting tool 3a changes its angular position, the contact element 7a also changes its angular position, so that it is always substantially diametrically opposite the cutting tool 3a.

[0070] Advantageously, during cutting, the contact element 7a supports the portion of the tubular element "T", preventing any bending due to the penetration action of the cutting tool 3a and the weight of the tubular element, which is particularly evident during the final steps of cutting when the tubular element loses axial stiffness, thus guaranteeing better cutting precision and final quality.

[0071] Preferably, as shown in the example, the contact element 7a is made in the form of one or more idle supporting rollers which rest on the outer surface of the tubular element "T". Figure 2

[0072] Advantageously, the rollers allow the contact element 7a to move in rolling contact along the outer surface "S" of the tubular element "T" without damaging the outer surface "S" by scraping or scratching.

[0073] According to a preferred embodiment, the contact arm 7 can also move on the measurement plane "M" between an operating position, in which the contact element 7a is in contact with the tubular element "T" to exert the action for supporting the tubular element "T", and a rest position, in which the contact element 7a is away from the tubular element "T".

[0074] Preferably, like the cutting arm 3, the contact arm 7 can also be moved by means of an actuator.​

[0075] According to a further aspect, the unit comprises an actuator of the contact arm 7 for moving the contact element 7a between an operating position and a rest position. The processing and control unit 5 is operatively connected to the actuator of the contact arm 7 for moving the contact element 7a as a function of the parameter representative of the peripheral profile of the tubular article T on the measurement plane M, which is derived on the basis of the values representative of the radial distance measured by the ranging sensor 4.

[0076] According to a further aspect, the processing and control unit 5 is configured to send to the actuator of the contact arm 7 a movement signal towards or away from the tubular article T as a function of the comparison between the values measured by the second sensor 6b (located at the contact element 7a) and the expected positioning values calculated on the basis of the values representative of the radial distance acquired by the ranging sensor 4.

[0077] In use, when the cutting arm 3 passes from the operating position to the rest position, the contact arm 7 also passes from the operating position to the rest position and vice versa, so that the contact element 7a performs the operation of cutting the tubular article "T" on the measurement plane "M" together with the cutting tool 3a.

[0078] Preferably, the cutting unit 1 also comprises a second sensor 6b located on the contact element 7a and configured to acquire, at different angular positions of the contact element 7a, a plurality of values representative of the distance between the contact element 7a and the outer surface "S" of the tubular article "T" measured on the measurement plane "M".

[0079] Even more preferably, the processing and control unit 5 is also configured to receive and process the above-mentioned values representative and perform, in the respective angular positions, a comparison of the parameter relating to the peripheral profile. This aspect makes it possible to check whether the position assumed by the contact element 7a at the different angular positions of the rotating ring 2 is correct with respect to the trend of the actual profile of the tubular article "T" assumed on the measurement plane "M" and acquired by the ranging sensor 4.

[0080] The processing and control unit 5 is also configured to send to the contact element 7a, after the above-mentioned comparison, any movement signal towards or away from the tubular article "T" as a function of the values measured by the second sensor 6b. In this case, the second sensor 6b allows a closed control to be performed, so that the processing and control unit 5 can modify the position of the contact element 7a on the basis of the comparison between the actual profile trend of the tubular article "T" on the measurement plane "M" determined by the ranging sensor 4 and the distance directly measured by the second sensor 6b. This guarantees that the contact element 7a is always in the correct state of support on the tubular article outer surface S, without being too far from it (so as not to perform the function of preventing bending) or too close to it (excessive compression of the tubular article surface, creation of marks on the tubular article surface or mechanical stresses on the component).

[0081] Therefore, in use, the tubular "T" advancing along the rotation axis "X" enters into the cutting unit 1, so as to be inserted inside the rotating ring 2. Upon a required cutting signal, the frame 8 starts sliding along the guide 8c to reach the cutting area; the tongs 8a, 8b are clamped around the tubular "T", while the frame 8 moves at the same speed as the tubular "T", so that the whole cutting unit 1 advances as one piece with the tubular "T" along the rotation axis "X".

[0082] During the feeding of the cutting unit 1, the cutting tool 3a and the contact element 7a are initially in a rest position, and the rotating ring 2 rotates so that the distance sensor 4 measures a plurality of indicative values representative of the radial distance between the distance sensor 4 and the outer surface "S" of the tubular "T" at a plurality of angular positions assumed by the rotating ring 2 on the measurement plane "M".

[0083] After the measurement step, the measured plurality of indicative values is sent to the processing and control unit 5, where it is processed for calculating at least one parameter representative of the peripheral profile of the tubular "T" on the measurement plane "M".

[0084] After acquiring the trend of the peripheral profile assumed by the tubular "T" on the measurement plane "M", the cutting arm 3 and the contact arm 7 are pre-positioned as they have to act on a tubular "T" having a diameter value on the measurement plane "M" equal to the maximum value acquired by the distance sensor 4. Preferably, in order to perform this positioning, the cutting arm 3 and the contact arm 7 both have a potentiometer.

[0085] After this first positioning, the rotating ring 2 remains rotating around the tubular "T", while the cutting arm 3 and the contact arm 7 pass from said pre-positioning position to the operating position.

[0086] During the rotation of the rotating ring 2, the first sensor 6a acquires a plurality of values representative of the radial distance between the cutting tool 3a and the outer surface "S" of the tubular "T" measured on the measurement plane "M" at different angular positions of the cutting tool 3a. At the same time, the second sensor 6b acquires a plurality of values representative of the radial distance between the contact element 7a and the outer surface "S" of the tubular "T" measured on the measurement plane "M" at different angular positions of the contact element 7a.

[0087] In this way, it is possible to know at all times the actual position of the cutting tool 3a and / or of the contact element 7a with respect to the surface of the tubular.

[0088] According to a preferred embodiment, the first and second sensors 6a, 6b are made in the form of laser sensors or ultrasonic sensors.

[0089] At the same time as the above acquisition step, the values representative are sent to the processing and control unit 5 which processes them and compares them with the parameters relating to the peripheral profile previously determined in the respective angular position (the profile is determined by means of the points measured by the distance sensor 4). Subsequently, if it is necessary to change those actual positions with respect to the peripheral profile determined by the distance sensor 4, any approach or distancing signals are sent to the cutting tool 3a and to the contact element 7a, according to the parameters measured by the first and second sensors 6a, 6b respectively. In this way, all the cutting operations are carried out with a complete closed control of the positions of the tool and of the contact element, which guarantees a high precision of the cut.

[0090] In other words, since the actual profile of the tube "T" is acquired on the measurement plane "M" by means of the distance sensor 4, and since it is compared with the distances acquired from the first and second sensors 6a, 6b in different angular positions, for each point of the external surface "S" it is possible to correct the respective positioning of the cutting tool 3a and of the contact element 7a, making them always follow exactly the actual profile of the tube "T", thus carrying out a particularly precise cut, regardless of the profile shape of the tube "T".

[0091] Advantageously, the cooperation of the distance sensor 4 with the first and second sensors 6a, 6b makes it possible to modify the position of the cutting tool 3a and of the contact element 7a at any instant, according to the trend of the actual profile of the tube "T" on the measurement plane "M", in particular the radial distance from the external surface "S" of the tube "T".

[0092] Advantageously, the cooperation of the distance sensor 4 with the first and second sensors 6a, 6b makes it possible to ensure that the cutting tool 3a (and the contact element 7a, if present) is always in the correct position to impart the best penetration action during the cut, which can be translated both into not generating excessive forces on the cutting tool 3a (and on the contact element 7a, if present) and in effectively penetrating the entire thickness of the tube "T", completely separating the piece of tube "T" from the continuous tube (with the contact element 7a, if present, suitably supporting it).

[0093] According to a preferred embodiment, the cutting unit 1 also comprises an adjustment sensor 9 (as shown in Figure 2 positioned on the frame 8 and configured for measuring the angular position of the rotating ring 2 with respect to the frame 8 and for defining the orientation of the peripheral profile of the tube "T" on the measurement plane "M".

[0094] Preferably, the adjustment sensor 9 is a capacitive sensor and provides a reference of the angular position of the rotating ring 2 in space and as a function of time.

[0095] Advantageously, the presence of the adjustment sensor 9 is useful because it ensures that the distance measuring sensor 4 always performs its measurements starting from the same point and allows the profile measured on the respective measurement plane "M" to be uniquely oriented.

[0096] More generally, the adjustment sensor 9 can be any type of sensor.

[0097] The present application achieves the predetermined objects, overcoming the drawbacks of the prior art.

[0098] In particular, the presence of the distance measuring sensor 4 makes it possible to scan (i.e. acquire the profile of) the outer surface "S" of the tube "T" on the measurement plane "M" in order to reconstruct the actual section of the tube "T" by points, thus moving the cutting tool 3a and / or the contact element 7a in a more precise manner, avoiding the risk of applying too much or insufficient cutting action.

[0099] The presence of the first and second sensors 6a and 6b, respectively at the cutting tool 3a and the contact element 7a, makes the cutting unit 1 more precise in cutting because they allow a closed control to be performed on the instantaneous position of the cutting tool 3a and the contact element 7a.

[0100] The presence of the first and second sensors 6a, 6b allows the position of the cutting tool 3a and the contact element 7a to be modified and adjusted, if necessary, according to the trend of the actual profile of the tube "T" acquired by the distance measuring sensor 4.

[0101] The cutting unit 1 according to the present application is therefore precise, reliable and versatile because it is able to make precise and accurate cuts regardless of the cross-sectional shape of the tube "T", adjusting the action of the cutting and contact devices in a unique and real-time manner according to the specific profile of the tube at the area being cut, significantly improving the ease of use and versatility of the entire cutting process on a line of extruded tubes made of thermoplastic material, eliminating the need for corrective measures or any incorrect settings required by the operator and guaranteeing complete automation of the process.

Claims

1. A cutting unit (1) for thermoplastic tubular fittings (T), comprising: - A rotating ring (2) that rotates about a rotation axis (X) and a pipe (T) that slides gradually in the rotating ring such that the longitudinal axis of the pipe (T) coincides with the rotation axis (X); - At least one cutting arm (3), which is mounted on the rotating ring (2) and equipped with a cutting tool (3a) and has related parts integrated with the rotating ring (2), the cutting arm (3) being movable between an operating position and a stationary position, in which the cutting tool (3a) engages with the pipe fitting (T) to apply a cutting action, and in the stationary position the cutting tool (3a) disengages from the pipe fitting (T); - At least one distance sensor (4) is located on the rotating ring (2) and configured to acquire multiple representation values ​​representing the radial distance between the at least one distance sensor (4) and the outer surface (S) of the tube (T) during rotation of the rotating ring, the radial distance being measured on a measurement plane (M) perpendicular to the axis of rotation (X); - A processing and control unit (5) operatively connected to the at least one ranging sensor (4) and configured to receive the measured plurality of representation values ​​and calculate at least one parameter related to the outer contour of the pipe (T) on the measuring plane (M) based on the measured representation values; The cutting unit (1) further includes an actuator for the cutting arm (3), the actuator being used to move the cutting tool (3a) between the operating position and the rest position. The cutting unit (1) further includes a first sensor (6a) configured to acquire multiple values ​​representing the distance between the cutting tool (3a) and the outer surface (S) of the pipe fitting (T) at different angular positions of the at least one cutting tool (3a); The processing and control unit (5) is configured to send a movement signal toward or away from the pipe fitting (T) to the actuator of the cutting arm (3) based on a comparison between the value measured by the first sensor (6a) and a desired positioning value, the desired positioning value being calculated based on the radial distance value collected by the distance sensor (4).

2. The cutting unit (1) according to claim 1, characterized in that, The at least one ranging sensor (4) is configured to acquire the plurality of representation values ​​representing radial distance during the full rotation of the rotating ring (2).

3. The cutting unit (1) according to claim 1, characterized in that, And among them, The processing and control unit (5) is operatively connected to the actuator of the cutting arm (3) for moving the cutting tool (3a) according to the parameters representing the outer contour of the pipe (T) on the measuring plane (M), the parameters being obtained based on the representation value representing the radial distance acquired by the distance sensor (4).

4. The cutting unit (1) according to claim 1, characterized in that, The ranging sensor (4) can be selected from: laser sensor and ultrasonic sensor.

5. The cutting unit (1) according to claim 1, characterized in that, The cutting arm (3) moves the cutting tool (3a) in a cutting plane that is perpendicular to the axis of rotation (X).

6. The cutting unit (1) according to claim 5, characterized in that, The measuring plane (M) coincides with the cutting plane.

7. The cutting unit (1) according to claim 1, characterized in that, The first sensor (6a) is located on the cutting tool (3a), and the distance is measured on the measuring plane (M).

8. The cutting unit (1) according to claim 1, characterized in that, Includes at least one contact arm (7), which is equipped with a contact element (7a) for the fitting (T) and has a related portion integrated with the rotating ring (2). The contact arm (7) is also movable between an operating position and a rest position, in which the contact element (7a) contacts the fitting (T) to apply an action for supporting the fitting (T), while in the rest position the contact element (7a) is away from the fitting (T).

9. The cutting unit (1) according to claim 8, characterized in that, It includes at least one contact arm (7), which is diametrically opposed to the at least one cutting arm (3).

10. The cutting unit (1) according to claim 8, characterized in that, Includes a second sensor (6b) located on the contact element (7a) and configured to acquire multiple values ​​representing the distance between the contact element (7a) and the outer surface (S) of the pipe fitting (T) at different angular positions of the at least one contact element (7a), the distance being measured on the measuring plane (M).

11. The cutting unit (1) according to claim 10, characterized in that, The device includes an actuator for moving the contact element (7a) between the operating position and the rest position, and wherein the processing and control unit (5) is operatively connected to the actuator of the contact arm (7), the actuator being used to move the contact element (7a) according to a parameter representing the peripheral contour of the fitting (T) on the measuring plane (M), the parameter being based on a representation value representing radial distance acquired by the distance sensor (4).

12. The cutting unit (1) according to claim 11, characterized in that, The processing and control unit (5) is configured to send a movement signal toward or away from the pipe (T) to the actuator of the contact arm (7) based on a comparison between the value measured by the second sensor (6b) and a desired positioning value, the desired positioning value being calculated based on the indicated value representing radial distance collected by the distance sensor (4).

13. The cutting unit (1) according to any one of claims 1-12, characterized in that, The processing and control unit (5) is positioned on the rotating ring (2).

14. The cutting unit (1) according to any one of claims 1-12, characterized in that, Includes a frame (8) and an adjustment sensor (9), the frame (8) being designed to support the rotating ring (2) and to move along the axis of rotation (X) according to alternating sliding movements, the adjustment sensor (9) being positioned on the frame (8) and configured to measure the angular position of the rotating ring (2) relative to the frame (8).

15. The cutting unit (1) according to any one of claims 1-12, characterized in that, Includes one or more clamps (8a, 8b) configured to constrain the tube (T) to the cutting unit (1) such that the longitudinal axis of the tube (T) coincides with the rotation axis (X).

16. A method for cutting a thermoplastic pipe fitting (T), comprising the following steps: - Prepare a cutting unit (1) according to any one of claims 1 to 15; - Rotate the rotating ring (2); - For multiple angular positions of the rotating ring (2) rotating around the pipe (T), the at least one distance sensor (4) is used to measure multiple representations of the radial distance between the distance sensor (4) and the outer surface (S) of the pipe (T), the radial distance being measured on a measurement plane (M) perpendicular to the axis of rotation (X); - The processing and control unit (5) is used to process the plurality of representation values ​​to calculate at least one parameter representing the outer contour of the pipe fitting (T) on the measuring plane (M) based on the measured representation values.

17. The method according to claim 16, characterized in that, The steps include: moving the cutting arm (3) toward or away from the pipe (T) based on the calculated parameters representing the outer contour of the pipe (T) on the measuring plane (M) and according to the represented value measured by the distance sensor (4).

18. The method according to claim 16 or 17, characterized in that, When the cutting unit (1) is manufactured according to claim 7, the following steps are further included: - The first sensor (6a) is used to acquire a value representing the radial distance between the cutting tool (3a) and the outer surface (S) of the pipe fitting (T), the distance being measured on the measuring plane (M); - Compare the value representing the radial distance between the cutting tool (3a) and the outer surface (S) of the pipe fitting (T) with the parameter related to the peripheral profile; - The cutting tool (3a) is moved toward or away from the pipe (T) based on the result of a comparison between the value representing the radial distance between the cutting tool (3a) and the outer surface (S) of the pipe (T) and the parameter associated with the peripheral contour.

19. The method according to claim 16 or 17, characterized in that, It also includes the following steps: - The second sensor (6b) of the cutting unit (1) is used to acquire a value representing the radial distance between the contact element (7a) of the fitting (T) and the outer surface (S) of the fitting (T), the radial distance being measured on the measuring plane (M); - Compare the value representing the radial distance between the contact element (7a) and the outer surface (S) of the tube (T) with the parameter related to the peripheral profile; - The contact element (7a) is moved toward or away from the pipe (T) based on the result of the comparison between the value representing the radial distance between the contact element (7a) and the outer surface (S) of the pipe (T) and the parameter related to the peripheral profile.

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