Apparatus and method for cutting thermoplastic pipe

Abstract

Described is a device for cutting a thermoplastic pipe (T), comprising: at least one guide (2) for movement in a predetermined direction (X); a unit (3) movable along the guide (2) with respect to a predetermined direction (X); a first actuator (5) configured for moving the movable unit (3) along the guide (2), the movable unit (3) comprising: a rotating unit (12) configured to rotate about the thermoplastic tube (T); a second actuator (6) configured for rotating the rotating unit (12) about the thermoplastic tube (T); at least one locking unit (20) provided with a clamping element (21) interacting with the tube (T) and movable between an open configuration and a closed configuration, said clamping element (21) and the rotating unit (12) being coupled to allow longitudinal plugging of the rotating unit (2) to the tube in a predetermined direction (X) in the closed configuration; a cutting tool (13) carried by the rotating unit (12) for cutting the pipe (T), the cutting tool (13) being configured to move radially relative to the pipe (T); a third actuator (7) carried by the rotating unit (12), running on the cutting tool (13) to move it radially relative to the pipe (T); a compression device (15) configured to act on the cutting edge (51, 52) of the pipe (T); means (16) for heating the compression means (15), configured for heating the compression means (15) to a predetermined temperature.

Description

Technical Field

[0001] The invention relates to an apparatus and a method for cutting a pipe made of thermoplastic material.

[0002] Thermoplastic tubing is produced by an extrusion process that starts with the material in a plastic state and uses a rotating screw system to force the material through a calibrated die of the appropriate shape and size.

[0003] A pipe production facility is called an extrusion line and it consists of several pieces of equipment, each designed for a specific function.

[0004] There is usually a cutting device in such a facility, usually located at the end of the production line, configured to divide the continuously extruded tube into pieces of specified and predetermined lengths.

[0005] The device comprises a cutting unit (with the cutting tool inserted therein) mounted on a movable carriage which, during the cutting operation, is integrally coupled to the extruded tube by means of clamping means called clamps.

[0006] Generally, the nature of the cutting action depends on the type of thermoplastic material being cut. Background Art

[0007] Many of the commonly used thermoplastic materials for pipes, such as PVC-U, ABS and PMMA, have brittle mechanical behavior and a particularly high hardness. Due to the above mechanical characteristics, these materials are usually cut by removing material using toothed discs or motor-driven grinding wheels. All the disadvantages of this cutting method are well known in the prior art, including the generation of polluting powder and shavings, and the need to suck, collect and dispose of them.

[0008] Cutting by separating material (e.g. using a cutting tool) overcomes all the problems associated with cutting by removing material, but, particularly in the case of tubes made from the above materials, if not cut using specific techniques, the tube may break during cutting (possibly damaging the tool), while the final quality of the cut surface may not be good enough and the cut itself may not be clean and precise.

[0009] In particular, in order to be able to perform a high-quality cut, it is necessary to ensure that the action of the cutting tool is perpendicular to the surface of the tube, which can be achieved by using a sufficiently rigid tool.

[0010] The stiffness of a cutting tool depends on the shape and thickness of the tool itself.

[0011] According to the prior art solutions commonly used in cutting by separating material, increasing the thickness of the cutting tool to increase the rigidity disadvantageously causes lips and large deformations of the pipe surface, for example thereby modifying the nominal external dimensions.

[0012] However, modifications of the lip and the nominal dimensions of the pipe may adversely affect the functionality of the pipe (for example the possibility of effectively coupling it with other components to build a specific network for supplying fluids) and generally determine a reduction in the quality of the pipe. Summary of the invention

[0013] It is considered necessary to overcome the above-mentioned technical drawbacks and in particular to ensure that the tube retains its dimensions and integrity even downstream of the cutting action (in particular concerning tubes made of thermoplastic materials with brittle mechanical behavior and particularly high hardness).

[0014] The object of the present invention is to meet the above needs by providing a cutting device and a method which allow cutting of thermoplastic pipes while maintaining the original dimensions of the pipe and its functionality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The technical features of the present invention are clearly described in the claims below with reference to the accompanying drawings, and its advantages are obvious from the following specific embodiments. The accompanying drawings only provide preferred embodiments of the present invention by way of example and do not limit the scope of the inventive concept. In the accompanying drawings:

[0016] - Figure 1 is a schematic perspective view of an apparatus for cutting a thermoplastic pipe according to the present invention;

[0017] - Figure 2 is a perspective view of a detail of an apparatus for cutting thermoplastic pipes according to the present invention;

[0018] - Figure 3 and Figure 4 yes Figure 1 A cross-sectional view of an embodiment of a cutting tool of a cutting device;

[0019] - Figure 5 and Figure 6 is a perspective view of an embodiment of a compression device of a cutting device;

[0020] - Figure 7 yes Figure 5 Schematic cross-sectional view of a compression device of an embodiment. DETAILED DESCRIPTION

[0021] With reference to the drawings, numeral 1 denotes an apparatus for cutting a pipe T made of thermoplastic material, for example a pipe T made of PVC.

[0022] Other thermoplastic materials for producing the tube T are, for example, PE, PP, PB, ABS and PMMA.

[0023] The tube T extends along a predetermined direction X and has an axis A.

[0024] According to an aspect, the cutting device 1 comprises at least one guide 2 for movement in a predetermined direction X.

[0025] The device 1 comprises a unit 3 movable along said guide 2 , which moves relative to a predetermined direction X.

[0026] The device 1 comprises a first actuator 5 configured for moving the movable unit 3 along the guide 2 .

[0027] The actuator 5 is preferably an electric actuator.

[0028] According to other examples, the actuator 5 is of the pneumatic or hydraulic type.

[0029] The movable unit 3 comprises a carriage 11 which allows movement in a predetermined direction X thanks to an actuator 5 .

[0030] The movable unit 3 comprises at least one locking unit 20 equipped with a clamping element 21 interacting with the tube T.

[0031] The clamping element 21 is movable between an open configuration and a closed configuration.

[0032] The gripping elements may be, for example, jaws (the clamp described above) allowing the pipe X to be locked relative to the movable unit 3 .

[0033] The movable unit 3 includes a receiving body 30 coupled to the bracket 11 .

[0034] like Figure 1 As shown in FIG. 1 , the body 30 of the movable unit 3 is passed through by the pipe T that has to be cut.

[0035] The movable unit 3 includes a rotating unit 12 configured to rotate around the tube T.

[0036] The rotating unit 12 is positioned inside the receiving body 30 .

[0037] According to e.g. Figure 2 In the embodiment shown in , the rotary unit 2 comprises a pair of annular elements 12A, 12B connected by a plurality of longitudinal bars 12C.

[0038] The clamping element 21 and the rotating unit 12 are coupled in such a way as to allow the rotating unit 12 to be constrained longitudinally to the tube T in a predetermined direction X in the closed configuration.

[0039] Thus, the rotating unit 12 can rotate relative to the locking unit 20 about the direction X, however, during cutting of the tube T, the rotating unit 12 is constrained to the tube T in the direction X, ie along the guide 2 .

[0040] The movable unit 3 includes a second actuator 6 configured to rotate the rotating unit 12 about the tube T.

[0041] The movable unit 3 comprises a cutting tool 13 for cutting on the tube T, carried by the rotating unit 12 .

[0042] The rotating unit 12 serves as a supporting body for the cutting tool 13 .

[0043] The movable unit 3 comprises a third actuator 7 carried by the rotary unit 12 , operating on the cutting tool 13 to move the tool 13 radially relative to the tube T.

[0044] Thus, the actuator 7 allows the cutting tool 13 to be moved from a first position in which the tool 13 is not in contact with the tube T, to a second position in which the tool 13 is fully immersed in the tube T for cutting.

[0045] Therefore, the cutting tool 13 is configured to move radially relative to the tube T.

[0046] The tool 13 rotates about the axis A of the pipe T and simultaneously radially sinks into the pipe T to perform cutting.

[0047] In fact, since the tool 13 is supported by the rotating unit 12 , when the rotating unit 12 rotates about the axis A, the tool 13 rotates about the axis A of the pipe T.

[0048] Then, the tool 13 is used to cut the tube T into two sections T1 and T2 having edges 51 and 52, respectively.

[0049] according to Figure 3 In the embodiment shown in FIG. 1 , the cutting tool 13 is a rotary disk blade which rotates about an axis of rotation A2 .

[0050] In other words, the tool 13 is preferably an idle disc blade.

[0051] according to Figure 4 In the embodiment shown in FIG. 1 , the cutting tool 13 is a knife edge.

[0052] The movable unit 3 also comprises power transmission means, preferably of the slip ring type, which allow power and signals to be transmitted to the rotating unit 12 , thus allowing the operation of the third actuator 7 .

[0053] The movable unit 3 comprises compression means 15 configured to act on the cut edge of the tube T.

[0054] The compression means 15 allow the cutting edge to be mechanically acted upon, ie deformed locally, thereby substantially eliminating any deformation caused by the cutting action.

[0055] In particular, the compression device 15 is configured to act on each cutting edge 51 , 52 of the tube T.

[0056] It should be noted that the compression means 15 act simultaneously on the end of the section of tubing being cut and on the end during cutting of the continuous tubing upstream of the section in question with respect to the extrusion direction.

[0057] Preferably, the compression device 15 is associated with the cutting tool 13 and is beside the tool 13 .

[0058] In other words, according to a preferred embodiment, the compression means 15 are positioned on opposite sides of the cutting tool 13 .

[0059] according to Figure 5 and Figure 7 In the embodiment shown by way of example, the compression device 15 comprises a flange 18 .

[0060] according to Figure 7 In the embodiment shown in FIG. 1 , the compression device 15 , in particular the flange 18 , comprises a first flange 18A and a second flange 18B.

[0061] The first flange 18A acts on the edge 51 of the segment of the tube T1 , whereas the second flange 18B acts on the cut end of the tube T2 upstream of the aforementioned segment with respect to the extrusion direction.

[0062] Each flange 18 preferably has a frustoconical shape, with the larger base facing towards the cutting tool 13 .

[0063] The movable unit 3 comprises a heating device 16 configured to heat the compression device 15 to a predetermined temperature.

[0064] The compression device 15 is heated to a temperature preferably between 50° and 200°, depending on the type of thermoplastic material of the tube T.

[0065] Advantageously, the heating means and the compression means 15 facilitate compression of the deformations produced by the cutting action and the movement of the lip.

[0066] Preferably, the heating device 16 comprises a stationary heating body 17 .

[0067] According to the example, the fixed heating body 17 transfers heat to the compression device 15 by sliding contact.

[0068] In this case, the compression device 15 , in particular the flange 18 , is heated by conduction.

[0069] Each fixed body 17 rests continuously on the outer surface of a corresponding flange 18 .

[0070] According to an embodiment, the fixed body 17 is coupled to the flange 18 and is configured to heat the flange 18 to a predetermined temperature.

[0071] According to one embodiment, each fixed body 17 comprises a resistance 19 determining the heating.

[0072] According to one embodiment, the compression device 15 comprises a support element 40 which is configured to also support the cutting tool 13 .

[0073] According to one embodiment, the compression device 15 comprises an outer compression element 41 supported by a support element 40 .

[0074] Preferably, the compression element 41 is an idle roller rotating about its own axis.

[0075] According to an example, the element 41 is heated by suitable heating means (not shown).

[0076] The heated compression element 41 contacts and compresses the edges 51, 52 of the cut tubing to eliminate the lip created by the cutting action and restore the original dimensions of the tubing T.

[0077] According to another aspect, the support element 40 comprises contact means configured to keep the compression element 41 in contact with the surface of the tube T during cutting.

[0078] Preferably, the contact means comprise one or more elastic elements, such as springs, which exert an elastic action on the compression element 41 (preferably operating by compression).

[0079] According to one embodiment, for example Figure 6 As shown in , the compression device 15 includes a compression element 41 and a flange 18 .

[0080] According to this embodiment, the compression element 41 acts simultaneously with the heated flange 18 at different parts of the edges 51 , 52 of the tube.

[0081] In general, the flange 18 and / or the compression element 41 can be heated by conduction (by means of a fixed body - shown and indicated as 17 for the flange 18 - which transfers heat to them), or, in an example not shown, the compression device 15 can be heated by induction or by radiation.

[0082] If the compression device 15 is heated by induction, the device 15 comprises a ferromagnetic material and the rotation unit 12 comprises at least one induction coil which is configured to generate electromagnetic induction on the compression device 15 .

[0083] The cutting tool 13 rolls with the heated flange 18 forced into contact with the surface of the tube T and is deformed, if necessary, by compression of the cut itself, with the mechanical and thermal effects causing the tube to deform after the cutting action and restore the original dimensions of the tube T that were not cut at the edge.

[0084] As mentioned above, in order to ensure a good cutting quality, the cutting plane must always be perpendicular to the axis A of the tube T.

[0085] Therefore, the axial stiffness of the cutting tool 13 is critical to prevent it from bending during the penetration action and translating into a non-vertical cutting plane.

[0086] This is particularly important for pipes made of thermoplastic materials such as PVC-U, ABS and PMMA, which have brittle mechanical behavior and a particularly high hardness.

[0087] However, as previously mentioned, the stiffness of the cutting tool 13 is closely related to its thickness.

[0088] According to an embodiment of the blade tool 13 , it is not possible to fall below a limiting thickness value of the tool 13 without a minimum stiffness to prevent non-perpendicular cutting and / or premature breaking of the tool 13 .

[0089] It should also be considered that it is the thickness of the cutting tool 13 that determines the degree of deformation induced on the tube T and the size of the resulting lip.

[0090] Therefore, in order to facilitate the rigidity of the tool 13, increasing the thickness of the tool 13 will result in a larger lip and deformation of the tube T.

[0091] The use of an idle disc cutting tool 13 advantageously allows limiting the deformation and reducing the extent of the lip.

[0092] Advantageously, the disc shape of the cutting tool 13 relative to the blade makes it possible to effectively reduce its thickness (with the same bending stiffness), thus significantly limiting the undesired formation of bulges and lips at the cutting plane of the tube T.

[0093] In this case, the cutting action comprises a radial feed movement and a rotation of the tool 13 about the axis A of the tube T, like a conventional knife edge, and a rotation movement of the disc tool about the corresponding axis A2.

[0094] The friction generated between the disc-shaped cutting tool 13 and the surface of the tube T is of the rolling type, all of which has the advantage of reducing the coercive effect on the material of the tube T during penetration.

[0095] However, it should be noted that the use of a thin disk blade can reduce but not eliminate deformation effects (such as curling) on ​​the surface of the tube T caused by the penetration of the cutting tool 13.

[0096] In this case, during the final steps of the cutting process, the heated compression device 15 (in the form of the flange 18 and / or the compression element 41) further acts on the surface of the tube T to mechanically and thermally recompress any lip and expansion created by the cutting tool 13.

[0097] According to a preferred embodiment, the rotation unit 12 comprises at least one temperature sensor 30 which is configured to measure a temperature value and to generate a signal S1 which represents the temperature value of the heating device 16 .

[0098] It should be noted that the heating device 16 brings the compression device 15 to a predetermined temperature, and therefore monitoring the temperature of the heating device 16 is critical.

[0099] The device comprises at least a control unit U communicating with a temperature sensor 30 and with a heating device 16, such as Figure 5 and Figure 6 as shown in .

[0100] The control unit U is configured to receive the signal S1 and control the heating device 16 according to the signal S1.

[0101] In other words, the unit U receives the signal S1 from the sensor 30 and controls the operating temperature of the heating device 16 based on the signal, for example controls the start-up or adjusts the power.

[0102] Controlling the operating temperature of the heating device 16 indirectly involves controlling the temperature of the flange 18 .

[0103] In practice, the temperature sensor 30 is combined with the unit U, advantageously allowing the heating device 16 to be maintained at a predetermined temperature.

[0104] Preferably, the temperature sensor 30 is a thermocouple.

[0105] According to another embodiment not shown, the temperature sensor 30 directly measures the temperature of the compression device 15 using, for example, a pyrometer type sensor.

[0106] According to one aspect, the invention relates to a method for cutting a thermoplastic tube T.

[0107] The method comprises the following steps:

[0108] - locking the thermoplastic tube T in a first direction,

[0109] - preparing a cutting tool 13 and a compression device 15 associated with the cutting tool 13,

[0110] - radially moving the cutting tool 13 relative to the thermoplastic tube T and rotating the cutting tool 13 about the axis A of the thermoplastic tube T to cut the thermoplastic tube T,

[0111] - heating the compression device 15 associated with the cutting tool 13 to a predetermined temperature,

[0112] - The heated compression device 15 rotates about the axis A of the tube T to compress the edges 51 , 52 of the cut tube.

[0113] The term "edges 51, 52 of the cut tube" refers to the edges of the tube T where the cut is made.

[0114] Advantageously, heating the compression device 15 enables it to compress better and eliminate the lip caused by the cutting of the tube T, restoring the integrity of the edge and the original dimensions of the tube.

[0115] According to one embodiment, the method comprises a step of heating the compression device 15 by radiation or magnetic induction.

[0116] According to an embodiment, the method comprises the steps of preparing the compression device 15 comprising the flange 18 and heating the flange 18 to a predetermined temperature.

[0117] Preferably, the step of heating the flange 18 to a predetermined temperature comprises a step of heating the flange 18 to a temperature preferably between 50° and 200°, depending on the type of thermoplastic material of the tube T.

[0118] Advantageously, heating the compression device 18 enables it to compress better and eliminate the lip caused by the cutting of the tube T, restoring the integrity of the edge of the tube.

[0119] According to one embodiment, the method comprises a step of preparing a heating device 16 coupled to the compression device 15 .

[0120] The step of heating the compression device 15 associated with the cutting tool 13 to a predetermined temperature comprises the step of activating the heating device 16 to heat the compression device 15 to the predetermined temperature.

[0121] According to an embodiment, the step of preparing the heating device 16 comprises a step of preparing a fixed heating body 17 coupled to the flange 18 to transfer heat by conduction.

[0122] The step of heating the flange 18 to a predetermined temperature includes the step of sliding the flange 18 and the fixed heating body 17 .

[0123] Advantageously, the sliding flange 18 and the fixed heating body 17 allow the flange 18 to be heated by conduction, allowing heat to be transferred from the fixed heating body 17 to the flange 18 .

[0124] According to an embodiment, the step of preparing the compression device 15 comprises a step of preparing the compression element 41 .

[0125] According to an embodiment, the method comprises the step of rotating the compression element 41 about the axis A of the tube T to compress the edges 51 , 52 of the cut tube T.

[0126] According to one embodiment, the step of rotating the heated compression device 15 for compressing the edges 51, 52 of the cut pipe T around the axis of the pipe simultaneously includes the step of rotating the flange 18 around the axis A of the pipe to compress the first edge portions 51A, 52A of the cut pipe, and the step of rotating the compression element 41 around the axis A of the pipe T to further compress the edges 51, 52 of the cut pipe T at the second edge portions 51B, 52B.

[0127] Therefore, in short, providing a cutting tool 13 with a heated compression device 15 significantly improves the cutting quality by separating the material of the tube T, effectively eliminating the limitation of cutting by separating the material (which advantageously does not generate dust and chips), namely, the generation of a lip and deformation on the surface of the tube T at the cutting plane, in particular for thermoplastic tubes with brittle behavior but high hardness.

Claims

1. An apparatus for cutting a thermoplastic pipe (T), comprising: - at least one guide (2) for movement in a predetermined direction (X); - a unit (3) movable along the guide (2) relative to the predetermined direction (X); - a first actuator (5) configured to move the movable unit (3) along the guide (2), The movable unit (3) comprises: - a rotating unit (12) configured to rotate around the thermoplastic pipe (T); - a second actuator (6) configured to rotate the rotation unit (12) about the thermoplastic tube (T); at least one locking unit (20) provided with a clamping element (21) interacting with the thermoplastic tube (T) and movable between an open configuration and a closed configuration, the clamping element (21) being coupled to the rotation unit (12) so as to allow longitudinal restraint of the rotation unit (12) to the tube along the predetermined direction (X) in the closed configuration; a cutting tool (13) carried by the rotating unit (12) for cutting the thermoplastic pipe (T), the cutting tool (13) being configured to move radially relative to the thermoplastic pipe (T); - a third actuator (7) carried by the rotary unit (12) and operating on the cutting tool (13) to move it radially relative to the thermoplastic pipe (T); - compression means (15) configured to mechanically act on the cut edges (51, 52) of the thermoplastic tube (T), i.e. to deform them locally, thereby substantially eliminating any deformation caused by the cutting action; means (16) for heating the compression means (15), configured to heat the compression means (15) to a predetermined temperature.

2. The device according to the preceding claim, characterized in that The compression device (15) is associated with the cutting tool (13) and is placed next to the cutting tool (13).

3. The device according to claim 1 or 2, characterized in that The compression device (15) comprises a flange (18).

4. Device according to the preceding claim, characterized in that Each flange (18) has a frustoconical shape, with the larger base facing towards the cutting tool (13).

5. The device according to any one of the preceding claims, characterized in that The compression device (15) comprises a support element (40) configured to support the cutting tool (13).

6. The device according to claim 5, characterized in that The compression device (15) comprises a compression element (41) supported by the support element (40).

7. The device according to any one of the preceding claims and claim 3, characterized in that The heating device (16) comprises a fixed heating body (17) coupled to a flange (18) and configured to heat the flange (18) to a predetermined temperature.

8. The device according to claim 7, characterized in that The fixing body (17) is configured for heating the flange (18) by conduction.

9. The device according to claim 7 or 8, characterized in that Each fixed body (17) comprises a resistor (19).

10. The device according to any one of the preceding claims, characterized in that The device comprises a temperature sensor (30), the temperature sensor (30) being configured to measure a temperature value and generate a signal (S1) representing the temperature value, the device comprising a control unit (U) communicating at least with the temperature sensor (30) and with the heating device (15), the control unit (U) being configured to receive the signal (S1) and control the heating device (16) according to the signal (S1).

11. The device according to any one of the preceding claims, characterized in that The cutting tool (13) is an idle disc blade.

12. A method for cutting a thermoplastic pipe (T), comprising the following steps: - locking said thermoplastic tube (T) in a first direction, - preparing a cutting tool (13) and a compression device (15) associated with said cutting tool (13) for mechanical action, ie local deformation of the cut edge of said thermoplastic pipe (T), - radially moving the cutting tool (13) relative to the thermoplastic pipe (T) and rotating the cutting tool (13) about the axis (A) of the thermoplastic pipe (T) in order to cut the thermoplastic pipe (T), - heating the compression device (15) associated with the cutting tool (13) to a predetermined temperature, - Rotating the heated compression device (15) about the axis (A) of the tube to deform the edges (51, 52) of the cut thermoplastic tube (T) in order to eliminate any deformation caused by the cutting action.

13. The cutting method according to claim 12, characterized in that: The cutting method comprises the steps of preparing a compression device (15) including a flange (18) and heating the flange (18) to a predetermined temperature.

14. The cutting method according to claim 12 or 13, characterized in that: The cutting method comprises the step of preparing a heating device (16) connected to the compression device (15), and the step of heating the compression device (15) associated with the cutting tool (13) to a predetermined temperature comprises the step of activating the heating device (16) to heat the compression device (15) to the predetermined temperature.

15. The cutting method according to claim 13 or 14, characterized in that: The step of preparing the heating device (16) includes the step of preparing a fixed heating body (17) coupled to the flange (18) to transfer heat by conduction, and the step of heating the flange (18) to a predetermined temperature includes the step of sliding the flange (18) and the fixed heating body to allow heat to be transferred from the fixed heating body to the flange (18).

16. The method according to any one of claims 12 to 15, characterized in that The step of preparing the compression device (15) comprises the step of preparing a compression element (41) associated with a support element (40) operatively connected to the cutting tool (13).

17. The method according to claim 16, characterized in that The step of rotating the heated compression device (15) about the axis (A) of the tube to compress the edges (51, 52) of the thermoplastic tube (T) comprises rotating the heated compression element (41) about the axis (A) of the tube to compress the edges (51, 52) of the cut tube (T).

18. The method according to claim 16 or 17, characterized in that The step of rotating the heated compression device (15) about the axis of the tube to compress the edges (51, 52) of the cut thermoplastic tube (T) also includes the step of rotating the flange (18) about the axis (A) of the tube to compress the first edge portion (51, 52) of the cut tube, and the step of rotating the compression element (41) about the axis (A) of the thermoplastic tube (T) to further compress the edges (51, 52) of the cut thermoplastic tube (T) at the second edge portion (51, 52) of the cut thermoplastic tube (T).

19. The method according to any one of claims 13 to 18, characterized in that The step of preparing a cutting tool (13) and a compression device (15) associated with said cutting tool (14) comprises the step of preparing a cutting tool (13) of the idle disc type.

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