EP3593964B1

EP3593964B1 - Cutting apparatus for plastic pipes

Info

Publication number: EP3593964B1
Application number: EP19184255.8A
Authority: EP
Inventors: Claudio Argnani
Original assignee: IPM SRL
Current assignee: IPM SRL
Priority date: 2018-07-11
Filing date: 2019-07-03
Publication date: 2021-08-25
Anticipated expiration: 2039-07-03
Also published as: EP3593964A1; IT201800007117A1

Description

The present invention relates to machines and apparatuses for cutting pipes of plastic material, and in particular it concerns a cutting apparatus arranged to perform cuts and chamfers on pipes made of PVC and other rigid and/or fragile plastic materials.
Pipes made of plastic material are widely used for collecting, distributing and supplying fluids, for example for collecting rain and wastewater, distributing drinkable water, combustible gas, etcetera.
Pipes are generally obtained by means of continuous extrusion processes wherein the plastic material suitably heated and taken to the plastic state is forced through a die such as to form a continuous tubular element that must be cut in order to originate pipes of desired length. The pipes thus obtained can then be further cut to obtain parts or shorter sections, according to the specific needs and applications.
To this end, there are known cutting apparatuses, so-called cutters, that are able to cut pipes, i.e. to completely section one cylindrical side wall thereof according to a plane transversal to the longitudinal axis of the pipe and to obtain the various parts. Cutting can also comprise chamfering at the same time external sharp corners of the ends of the parts originated from cutting i.e. removing by means of an inclined cut the end prism of the aforesaid sharp corners. An apparatus for cutting pipes according to the preamble of claim 1 is known from the publication GB652388A .
There are known cutting apparatuses comprising one or more cutting discs, or mills, that are rotated about their respective axes and coaxially around the pipe to be cut, which is suitably blocked, so as to incise and cut radially and progressively from outside inwardly the cylindrical wall of the pipe along its whole circumference. Rotating mills are generally mounted on likewise rotating supporting rings or crowns, in particular rotatably supported by a fixed frame of the apparatus and rotated about an axis that is almost coaxial and coincident with a longitudinal axis of the pipe.
However, such cutting apparatuses, also known as planetary saws, have several disadvantages.
The aforesaid cutting apparatuses are in fact rather expensive due to complex means and mechanisms required to rotate the mills mounted on the supporting ring which is in turn rotated. Furthermore the mills, rotating at a high speed, for performing precise and top quality cuts and chamfers on the wall of the pipe, are very noisy and produce a huge amount of swarf in the form of dust that, in addition to dispersing in the surrounding environment, penetrate inside the pipe which consequently needs to be suitably cleaned after cutting.
Another disadvantage of the aforesaid cutting apparatuses is the low quality of the chamfered cut which is obtained in case the pipe is not perfectly cylindrical, i.e. with a deformed section, for example oval. As known, the chamfered cut is made by coupling two mills suitably shaped and sized such as to make, by penetrating for a predefined amount into the cylindrical wall of the pipe, a chamfer of predetermined sizes, generally equal to half the thickness of the pipe side wall. Of course, in case the pipe is not perfectly cylindrical, the mills penetrate, while rotating about the pipe, in an uneven manner into the cylindrical wall, producing a chamfer of variable size along the circumference.
In order to overcome such drawbacks, there are known cutting apparatuses provided with one or more single cutting edge tools or knives, rotated around the pipe and movable from outside inwardly of the pipe itself such as to incise and cut the cylindrical wall thereof along its entire circumference. Tools are generally mounted on respective supporting arms rotatably fixed to a rotating crown or ring such as to rotate with the latter about an axis coincident with the pipe axis and further rotate in relation to the rotating ring so as to move the tools towards the pipe external surface and progressively incise and cut the latter.
A drawback of such cutting apparatuses is that they cannot be used with pipes made of PVC. Polyvinyl chloride or PVC is in fact a stable and hard plastic material, though rather rigid and subject to be broken when it is mechanically stressed. In particular, pipes made of PVC cannot be cut, especially at high speed, with single cutting edge tools unless they are previously heated and thus made more malleable and plastic and hence not susceptible to be locally broken, fractured, chipped when they are cut by a blade.
However, the process of heating pipes causes the cutting apparatus to be more expensive and complex as it has to be provided with suitable means for heating the pipe. Furthermore, the cutting process lasts significantly longer as a certain amount of time is required for heating at the required temperature the pipes being processed.
GB 652388 illustrates an apparatus for cutting pipes made of asbestos-cement comprising a supporting ring provided with two series of studs, screwed as staggered relatively to each other to fix the ring concentrically of the pipe, and with a peripheral groove adapted to partially receive a ring-like blade-holder that is manually rotated relative to the ring by means of two spokes, one of which comprises a tool-holder housing having a nut screwed thereon. The tool-holder is slidably mounted in the housing and connected to the nut so that, by rotating the latter, the cutting tool can be moved closer to the pipe. The supporting ring and the ring-like blade-holder are each provided with locating means, for example a hole, which are suitably aligned and enable to remove the apparatus from the pipe. A calibrated setting wedge is used in conjunction with the studs for locating the supporting ring concentrically of the pipe.
One object of the present invention is to improve the known cutting apparatuses for cutting and chamfering pipes made of plastic material, in particular PVC.
Another object is to provide a cutting apparatus which makes it possible to cut clearly and precisely pipes of any plastic material, even made of PVC or other rigid and/or fragile plastic material, without breaking them.
One further object is to implement a cutting apparatus that is little noisy and capable of generating while cutting, fragmented, non-continuous and large-size swarf, that can therefore be more easily sucked and recycled for later processes and only outside the pipe, not inside it.
One still further object is to implement a cutting apparatus having a simple and cost-effective structure and efficient and reliable functioning.
These and other objects are obtained by a cutting apparatus according to one or more of the hereinafter reported claims.
The invention shall be better understood and implemented referring to the enclosed drawing which shows an exemplary and non-limiting embodiment, wherein:

Figure 1 is a front schematic view of the cutting apparatus of the invention associated with a pipe made of plastic material.

Referring to Figure 1, a cutting apparatus 1 according to the invention is illustrated arranged for making cuts on pipes made of plastic material, in particular pipes made of PVC or rigid and/or fragile plastic materials.
The cutting apparatus 1 comprises a supporting ring 2 suitable to rotate about a rotation axis Z and provided with a central opening 2a for inserting a plastic pipe 50 to be machined in a work configuration L. In such work configuration L the pipe 50 is blocked by locking means of the cutting apparatus 1, of the known type and not illustrated, such that a longitudinal axis thereof is substantially coincident with the rotation axis Z. The supporting ring 2 and the locking means are supported by a supporting structure or frame of the cutting apparatus 1, also of the known type and not illustrated in the figures.
The cutting apparatus also comprises a cutting tool 3 supported by first supporting means 11 fixed to the supporting ring 2 and arranged to move the aforesaid cutting tool 3 towards the rotation axis Z so as to abut and cut a wall 50a of the pipe 50. The cutting tool 3 comprises a single cutting edge tool or knife arranged to incise and pass completely through the wall 50a of the pipe 50, achieving a complete cut which originates two parts of pipe 50. The complete cut carried out by the cutting tool 3 is preferably orthogonal to the wall 50a of the pipe 50 and to the rotation axis Z.
The cutting tool 3 can further be heated to a predefined cutting temperature T during the cutting of the pipe 50, so as to plasticize and make the plastic material of the pipe locally malleable, as will be better explained in the hereinafter description. To this end, heating means 30 are provided and associated to the cutting tool 3 to heat the latter to the predefined cutting temperature T, comprised between 70 °C and 120 °C. Heating means 30 are for instance electric heating means 30 i.e. fed with power energy by suitable cables 31 to generate heat inside the cutting tool 3. The heating means 30 are provided with an adjusting device, of the known type and not illustrated, which makes it possible to adjust the heating level of the cutting tool, namely the working temperature T of the latter according to the characteristics of the pipe 50 to be cut (type of material, thickness of the wall). Furthermore, the cutting apparatus 1 comprises a chamfering tool 4 supported by second supporting means 12 fixed to the supporting ring 2 and arranged to move the chamfering tool 4 towards the rotation axis Z so as to abut and interact with a wall 50a of said pipe 50. The chamfering tool 4 comprises a respective single cutting edge tool or knife suitably shaped, that is capable of performing externally on the wall of the pipe 50 an annular-shaped groove which will originate a chamfer on the outer edge of the end of one of two parts of the pipe 50 obtained by the complete cut performed by the cutting tool 3.
The cutting apparatus 1 comprises a compression tool 5 supported by third supporting means 13 fixed to the supporting ring 2 and arranged to move the aforesaid compression tool 5 towards the rotation axis Z so as to abut the wall 50a of the pipe 50 and flatten and compress the edges of the cut made on said wall 50a by the cutting tool 3. The compression tool 5 comprises a roller that is mounted free to rotate on the third supporting means 13 and capable to abut and rotate externally on the wall 50a of the pipe 50 by exerting a defined compression force.
In the illustrated embodiment, the first supporting means 11, second supporting means 12 and third supporting means 13 comprise respective supporting arms fixed to the supporting ring 2 and operable, for instance separately and independently, to move, in particular linearly and radially with respect to the rotation axis Z, the respective tools 3, 4, 5 towards, or away from, the pipe 50. More precisely, the supporting arms 11, 12, 13 are cantilevered fixed to a front wall of the supporting ring 2, radially directed towards the central opening 2a and comprise respective actuating slides 21, 22, 23 which support the corresponding tools 3, 4, 5 and are linearly actuated by a movement system of the known type and not illustrated in the figures, so as to make the tools 3, 4, 5 abut against the pipe 50. The movement system, for instance of mechanical type, is capable of moving the actuating slides 21, 22, 23 together or separately.
In detail, the first supporting means comprise a first supporting arm 11 provided with a first actuating slide 21 which the cutting tool 3 is fixed to. The second supporting means comprise a second supporting arm 12 provided with a second actuating slide 22 which the chamfering tool 4 is fixed to. The third supporting means comprise a third supporting arm 13 provided with a third actuating slide 23 which the compression tool 5 is fixed to.
The functioning of the cutting apparatus 1 of the invention provides an initial step of inserting and blocking the pipe 50 in the work configuration L.
The supporting ring 2 is rotated about the rotation axis Z along with the tools 3, 4, 5 and the respective supporting rings 11, 12, 13.
In case of chamfer-free cut, the first actuating slide 21 of the first supporting arm 11 is linearly actuated such as to push the cutting tool 3 against the wall 50a so as to incise and gradually cut the pipe 50 along its entire circumference.
The cutting tool 3 is previously heated by the heating means 30 until the predefined cutting temperature T is reached and it is kept at that temperature almost constant during the whole cutting process. Thereby, the cutting edge of the cutting tool 3 heats the plastic material, in particular PVC, making it locally plastic and malleable, capable of being incised and cut without breaking or shattering or fracturing as a result of the force or push exerted by the tool itself.
At the same time, the third actuating slide 23 of the third supporting arm 13 is linearly actuated so as to push the compression tool 5 (roller) against the wall 50a to squeeze or press the edges of the cut with a pre-established compression force while said cut is being made by the cutting tool 3. Thereby the outer surface of the wall 50a of the pipe 50 is kept even and regular.
In case of chamfered cut, the chamfering tool 4 too is abutted against the wall 50a of the tube 50 actuating the second actuating slide 22 of the second supporting arm 12. Thereby the chamfering tool 4, rotating with the supporting ring 2 about the rotation axis Z and penetrating in the wall 50a, makes an annular-shaped groove of pre-established depth which creates the chamfer on the outer corner of the end of one of two parts of the pipe 50. In this case, the cutting tool 3 is inserted in the aforesaid annular-shaped groove 52 so as to finish the complete pass-through cut.
It is further provided that the chamfering tool 4 makes the annular-shaped groove before the cutting tool 3 operation.
In the illustrated embodiment, thanks to the shape of the chamfering tool 4 only one of the two ends of the parts of pipe 50 created by the cut has a chamfer of the outer corner. However, it is possible to shape the chamfering tool such that it originates respective chamfers on both ends of the parts of pipe 50.
Thanks to the cutting apparatus 1 of the invention it is thus possible to make precise and clear cuts with or without chamfers also on pipes made of PVC or similar plastic material, in particular rigid and/or fragile.
Tests made by the Applicant have shown that heating the cutting tool 3, in addition to preventing break or crack or chipp of the material (PVC) while cutting, allows to obtain a processing (complete cut) quality and precision comparable to those of cuts made by means of planetary saws where the plastic pipe is previously heated.
The use of a single cutting edge cutting tool 3 also enables the cutting apparatus 1 of the invention to be silent and to cut the pipe substantially without removing material.
Furthermore, as the cutting tool 3 cuts the pipe after the chamfering tool 4 has made the annular-shaped groove originating the chamfer, the plastic swarf generated by such chamfering operation cannot penetrate inside the pipe which therefore does not need to be cleaned after cutting.
Lastly, it should be noted that the cutting apparatus 1 of the invention provided with the three supporting arms 11, 12, 13 fixed to the supporting ring 2 and supporting the respective tools 3, 4, 5 have a simple and cost-effective structure with efficient and reliable functioning.

Claims

Cutting apparatus (1) for making cuts on pipes made of plastic material, in particular PVC, comprising:
- a supporting ring (2) suitable to rotate about a rotation axis (Z) and provided with a central opening (2a) for inserting a pipe (50) to be machined in a work configuration (L);

- at least one cutting tool (3) supported by first supporting means (11) fixed to said supporting ring (2) and arranged to move said cutting tool (3) towards said rotation axis (Z) so as to abut and cut a wall (50a) of said pipe (50);
characterized in that said cutting tool (3) is heatable to a predefined cutting temperature (T) during the cutting of said pipe (50) by heating means (30) associated to said cutting tool (3) and arranged to heat the latter to said predefined cutting temperature (T).
Cutting apparatus (1) according to claim 1, wherein said heating means (30) comprises electric heating means.
Cutting apparatus (1) according to any preceding claim, wherein said predefined cutting temperature (T) is comprised between 70 °C and 120 °C.
Cutting apparatus (1) according to any preceding claim, comprising a chamfering tool (4) supported by second supporting means (12) fixed to said supporting ring (2) and arranged to move said chamfering tool (4) at least towards said rotation axis (Z) so as to abut and interact with said wall (50a) of said pipe (50).
Cutting apparatus (1) according to any preceding claim, comprising a compression tool (5) supported by third supporting means (13) fixed to said supporting ring (2) and arranged to move said compression tool (5) towards said rotation axis (Z) so as to abut said wall (50a) of said pipe (50) and compress edges of a cut made on said wall (50a) by said cutting tool (3).
Cutting apparatus (1) according to claim 5, wherein said compression tool (5) comprises a roller that is mounted free to rotate on said third supporting means (13) and capable to abut and rotate externally on said wall (50a) of said pipe (50) by exerting a defined compression force.
Cutting apparatus (1) according to claim 5 or 6, wherein said first supporting means (11), second supporting means (12) and third supporting means (13) comprise respective supporting arms fixed to said supporting ring (2) and operable to move, in particular linearly and radially with respect to said rotation axis (Z), the respective tools (3, 4, 5) towards, or away from, said pipe (50).
Cutting apparatus (1) according to any preceding claim, wherein said cutting tool (3) comprises respective single cutting edge tools.
Cutting apparatus (1) according to any preceding claim, wherein a longitudinal axis of said pipe (50) is substantially coincident with said rotation axis (Z) in said work configuration (L).