WO2011104734A1

WO2011104734A1 - Method of and machine for cutting or welding pipes with contactless measuring of the distance between the latter and the surface of the pipe

Info

Publication number: WO2011104734A1
Application number: PCT/IT2010/000081
Authority: WO
Inventors: Andrea Guerra; Angelo Corneo; Daniele Renaldini
Original assignee: Tube Tech Machinery S.R.L.
Priority date: 2010-02-26
Filing date: 2010-02-26
Publication date: 2011-09-01

Abstract

The present application relates to a machine (1) for carrying out the cutting or welding of the surface of pipes, comprising at least one mandrel (3) for supporting and displacing the pipe during the machining and a cutting or welding head (4) for emitting a laser beam adapted to carry out the cutting or welding of / on the surface of the pipe. The machine comprises measurement means (10) operating without contact with the pipe surface, adapted to measure the distance between the measurement means and one or more points of the pipe surface. Preferably, the measurement means the machine is provided with are of laser type. In addition, a method for carrying out the cutting or welding of / on the surface of pipes, comprising a first step wherein a pipe is housed and blocked inside one or more mandrels and a step wherein the pipe cutting or welding is carried out by a laser beam emitted by at least one laser cutting or welding head, is described. The method comprises the further step of measuring the distance between at least one point on the pipe surface by distance measurement means operating without contact with the pipe surface.

Description

METHOD OF AND MACHINE FOR CUTTING OR ELDING PIPES WITH CONTACTLESS EASURING OF THE DISTANCE BETWEEN THE LATTER AND THE SURFACE OF THE PIPE

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FIELD OF THE INVENTION

The present invention relates to a machine and a method for cutting or welding pipes, and particularly a machine and a method for carrying out cutting or welding operations of / on the surface of pipes, having great dimensions too, by a laser machining head for realizing pipe portions having reduced length or cutting portions of the surface and realizing holes, seats, countersinks, welding grooves, and like, or finally for carrying out welding on the pipe surface too.

KNOWN PREVIOUS ART

In the machines known in the art and used for carrying out this type of operations, a preferably tridimensional laser head is used.

With the term tridimensional laser head it is intended that the laser beam used for carrying out the cutting (or welding) is generated by an emitter mounted on a mechanical arm, moved by appropriate means known for such a use, adapted to move the head in the space so that to change its relative position and the tilt relatively to the pipe surface in process, for example obtaining the desired cutting.

Conventional machines for pipe cutting are provided with at least a couple of mandrels used for blocking the pipe during the machining and conferring it the feed and rotation controlled motions.

More in detail, during the machining, the pipe is housed inside the mandrels so that the rotation centre of the mandrel coincides with the longitudinal pipe axis, and it is rotated in order that the laser beam emitted by the cutting head could reach the pipe surface and carry out the cutting.

In addition, the mandrels give the pipe a translation motion along the longitudinal pipe axis causing the feeding while the cutting operations are carried out.

It has to be noticed that, according to the pipe dimensions to be processed, and particularly of its length and diameter, usually the machines are provided with four or two mandrels.

Usually, the two - mandrel configuration is used in the machines intended for machining pipes having a diameter up to about 300 mm, whereas machines provided 0081

with four mandrels are used on the contrary for greater diameters.

In this latter case, two mandrels are placed at two machine ends, whereas the other two are placed closed together in the central part of the machine.

The two mandrels placed in the centre of the machine are reciprocally spaced out in such a way to identify, in the space between them, the cutting zone where the laser head will intervene.

On the contrary, in the machines provided with only two mandrels, then intended for pipe machining having a relatively little diameter, the cutting zone where the laser head will intervene corresponds with the cantilevered portion of pipe surface outside the second mandrel.

The carried out cutting precision is an essential characteristic of these types of machines. In fact, the requested tolerances are very limited most of all if the cut pipe portion is intended for a subsequent welding or coupling with another element complementary therewith.

Despite this, a problem frequently encountered in the machine use is the inadequate precision of the cutting, mainly because of the curvature or bending phenomenon of the pipe along its own longitudinal axis, mainly caused by production defects of the same pipe.

In addition, also the pressure exercised onto the outer surface of the pipe by the mandrels, determining its blocking in the machine, may aid the curvature increasing and its substantially misalignment and displacement from the ideal perfectly straight shape.

For these reasons, in the pipe in process in the cutting machine, when it is blocked and rotated by the mandrel, every cross section of the pipe have a rotation centre not necessarily coinciding with the rotation centre of the mandrel.

Such problems are more evident in the portion of the pipe surface more distant from the mandrel constraining point, above all in the machines provided with only two mandrels, where the cutting is carried out onto the cantilevered portion of the pipe, out of the second mandrel.

It has to be noticed, for example, the case wherein a series of aligned holes is to be realized at the center line of a pipe surface having a squared section: because of the pipe curvature the hole centers will not be perfectly aligned with the center line of the surface.

The same problems caused by the pipe curvature are encountered in the pipe cutting along its cross section, that is along a plane perpendicular to the ideal longitudinal axis of the pipe.

In fact, as mentioned, the pipe has not a longitudinal axis perfectly aligned with the rotation centre of the mandrel, therefore the cross section too, along which the cutting has been carried out, will not be perfectly perpendicular to the pipe longitudinal axis.

It's obvious that problems caused by the longitudinal curvature of the pipe cannot be disregarded if high qualitative levels in machining and precision in carried out cutting have to be guaranteed.

For these reasons, some tricks have been adopted to reduce the pipe curvature and render the longitudinal axis straight as much possible, in such a way that its surface will be coincident as much possible with the ideal surface that it would have if the longitudinal axis would be perfectly straight.

A first effort to solve these problems leaded to the installation of mandrels provided with clamps for blocking pipes in the machines for pipe cutting, having a greater extension in the longitudinal direction, so that to distribute the pressure exercised on the pipe along a bigger portion of its surface, to obtain a "straightening" effect.

However, such a solution leaded limited improvements in pipe curvature reduction, not sufficient to guarantee a correct alignment of the pipe longitudinal axis with the rotation centre of the mandrel. As a consequence, the problems encountered in correct alignment and cutting precision effected are not completely solved.

Another solution adopted is to provide the machines for cutting pipes with measurement systems able to evaluate the pipe curvature carrying out measurements of the distance in different points of the pipe surface.

Particularly, the laser cutting machines known in the art are provided with measurement means contacting the pipe surface, for example a contour follower.

The tip of the contour follower is placed in contact with the pipe surface in 000081

different positions thereof, in such a way to be able to detect differences of the measured values and determine the pipe curvature and its misalignment relatively to the ideal straight condition.

Nevertheless this solution too does not allow a satisfying measurement accuracy and, above all, the measurement steps carried out by a contour follower will considerably slow down the process of pipe laser cutting. In fact, the measurement operation takes long time because the contact measurement means, and particularly the contour followers, are very fragile and then their positioning in contact with the pipe surface has to be carried out very slowly to avoid possible breaking and maintain high measurement precision.

SUMMARY OF THE INVENTION

Object of the present invention is to provide a machine and a method for carrying out the laser cutting or welding of / on the surface of pipes, allowing to overcome problems of the known prior art before explained and allowing to avoid the positioning and precision problems in cutting or welding caused by the misalignment of the longitudinal pipe axis and its curvature.

In addition, it is an object of the present invention to speed up the steps of detecting the pipe geometry, and particularly its curvature in the cutting or welding zone, so that to not slow down the machining process.

In addition, it is another object of the present invention to provide a machine and a method for cutting or welding pipes, wherein the operations of pipe curvature measurement may be carried out both before and during the cutting operations, in such a way to be able to guarantee with high precision the movement adaptation of the laser cutting head based on the real geometry of the pipe and its curvature.

These and other objects are obtained by a machine and a method for carrying out the pipe cutting according to the independent claims 1 and 10.

The machine for carrying out the cutting of the surface of pipes, according to the present inventions, comprises at least one mandrel for supporting and moving the pipe during the machining and a cutting or welding head, preferably of tridimensional type, for emitting a laser beam adapted to carry out the cutting or welding of / on the surface of the pipe.

According to a preferred embodiment, the machine is provided with a couple of mandrels housing the pipe in their inside, and imposing it a rotation and translation motions around / along the rotation axis of the mandrel itself.

The machine is characterized by comprising measurement means operating without contact with the pipe surface, adapted to measure the distance between the measurement means and one or more points of the pipe surface.

With the term non - contact measurement means it is intended that the latter do not need any contact with the surface from which the distance is to be measured.

Preferably, the measurement means of the machine are of laser type and they are selected between laser triangulation, time of flight laser and laser scanner.

The machine, according to the present invention, comprises means for moving the measurement means, allowing their displacement in different measurement positions relatively to the pipe surface.

In detail, the means for moving the measurement means allow, preferably, the space movement along the three orthogonal directions X-Y-Z, and comprise at least one straight guide disposed parallel with the rotation axis of the mandrels, at least one linear actuator for allowing the controlled displacement along the guide, and at least one arm, or similar means, for constraining the measurement means to the guide.

Advantageously, the measurement means of the distance of the pipe surface, not needing any contact with the surface itself, allow to carry out the measurements in a speedy and accurate way.

In the laser cutting or welding machine according to the present invention, a measurement of the distance in different points of the pipe surface is carried out, such measurements being subsequently processed and interpolated by a controlling unit determining the real curvature of the pipe in process.

In fact, by the measurement of the distance in points placed in opposed position on the pipe surface it is possible, by valuating the difference of such values, to determine the misalignment of the real longitudinal axis of the pipe relatively to the rotation axis of mandrels.

As will be more evident in the rest of the description, the distance measurement is carried out in points belonging to opposite pipe faces, in case of squared, rectangular or similar section pipes, otherwise in diametrically opposed points in case of circular section pipes.

Advantageously, the non - contact measurement means of which the machine is provided with, according to the present inventions, allow to determine the real rotation centre of each pipe cross section in which the cutting or welding are being carried out or have to be carried out, in such a way to balance the geometrical misalignment of the rotation centre and its curvature adapting and modifying the cutting or welding head movement.

In addition it is described a method for carrying out the cutting or welding of / on the pipe surface, comprising a first step wherein the pipe is housed and blocked inside one or more mandrels, by which the pipe is shifted and rotated in a controlled way along / around an axis. The cutting or welding of the pipe is carried out by a laser beam emitted by at least one laser cutting or welding head.

The method according to the present invention is characterized by comprising the step of measuring the distance between at least one point on the pipe surface by distance measurement means operating without contact with the pipe surface.

The points wherein the distance is measured by the non - contact measurement means are preferably placed in an opposed position on the pipe surface.

In other words, the distance measurement is carried out in points belonging to opposite pipe faces, in case of squared, rectangular or similar section pipes, otherwise in diametrically opposite points in case of circular section pipes.

The method further comprises the step of determining the curvature of the pipe by a controlling unit providing the difference of the distance values of the pipe surface measured in points placed in opposed position over the pipe surface.

The real pipe curvature is then simply, rapidly and accurately determined, and allows to remove problems of cutting and welding precision caused by the non perfect straightness of the pipe.

Advantageously, the measurement operation of the distance of some points of the pipe surface may be carried out both before executing the cutting or welding operations, to determine the pipe curvature, and successively, between a cutting and the subsequent one, to render even more accurate the measurement and assessment of the real geometry of the pipe portion wherein the subsequent machining will be carried out. The movement of the laser cutting or welding head is controlled based on the measured pipe curvature, to adapt the head movement to the real pipe shape and then to obtain the cutting desired, with no positioning errors.

In addition, the laser measurement means allow to check and control the carried out cutting or welding quality and precision, when the process is ended, always with reduced time and extraordinary accuracy.

BRIEF DESCRIPTION OF THE FIGURES

These and other advantages of the present invention will be evident from the following description and drawings in attachment for illustrative and not limitative purposes, wherein:

^■ figure 1 shows a top plant schematic view of a pipe cutting machine according to the present invention;

^■ figure 2 shows a top plant schematic view of another possible embodiment of a pipe cutting machine provided with four mandrels;

■ figure 3 shows a front view of the machine of figure 1 for cutting pipes according to the present invention;

^■ figure 4 shows a side partial view of the machine of figure 1 for cutting pipes according to the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Figure 1 shows a schematic plant view of a machine 1 for cutting pipes according to the present invention, provided with two mandrels 2 and 3 holding the pipe 5 during the machining steps, respectively placed at the initial and ending parts of the machine, and pipe cutting means, preferably composed of a tridimensional laser cutting head 4.

As can be better seen in the front view of the machine in figure 3, each of the two mandrels 2 and 3 is provided with a cross - shaped couple of clamps 6 that, contemporaneously actuated by hydraulic or pneumatic actuators, block the pipe 5 in their inside to carry out the machining steps.

Hereafter it will be referred to a pipe cutting machine provided with two mandrels, as illustrated in figure 1, although the machine according to the present invention is not intended to be limited by such a configuration. In fact, as afore said, the number of mandrels of the machine may change according to the dimensions of the pipe in process.

Preferably the machines adapted for working pipes having a diameter up to about 300 mm are provided with only two mandrels whereas in the machines intended for pipe machining having a bigger diameter are used four mandrels to assure a more correct positioning and blocking of the pipe itself. The figure 2, for example, shows a machine for cutting pipes provided with four mandrels 2, 2a, 3 and 3a, wherein the cutting zone is comprised in the space between the mandrels 2a and 3a placed in the central portion of the machine.

Going back on the embodiment illustrated in figure 1 , wherein the two mandrels 2 and 3 are present inside which the pipe is housed, the first mandrel 2 imparts to the pipe 5 the feeding and rotating motions along the axis A needed for carrying out the cutting operations along the whole outer pipe surface.

In fact, the mandrel 2 placed into the initial part of the machine is mobile, being constrained to means allowing the shifting along the X direction in such a way to impart the feeding motion of the pipe in process.

In addition, the mandrel is provided with means for rotating the pipe 5 along the rotation axis A of the mandrel.

The second mandrel 3, placed nearer the laser machining head, is rotatable too in synchronization with the first mandrel 2, and it can be subjected to limited displacements along the X direction so that it is not disposed in the range of cutting laser beam, for example when the laser beam is tilted relatively to the pipe surface and it is oriented towards the mandrel 3.

It has to be noticed that, to allow the feeding pipe motion during the machining, the clamps 6 of the second mandrel 3 are provided with rollers, or similar means known for such an use, allowing the pipe shifting inside the mandrel in a direction corresponding with its longitudinal axis.

The pipe is blocked inside the mandrels 2 and 3 thereby resulting centered relatively to them, that is in such a way that the longitudinal pipe axis coincides with the rotation axis of the mandrel, represented with the reference A.

As mentioned, the perfect alignment condition of the pipe longitudinal axis with the axis A is verified only if the pipe does not present any production defects, and the pressure exercised by the mandrel clamps does not cause any effect on its surface.

Such a condition has really never occurred, and each pipe in process presents a different curvature and its cross sections, particularly those of the cantilevered pipe portion out of the second mandrel 3 (right side of figure 4), at the cutting zone, have a rotation axis non - coincident with the rotation axis A.

In other words, every single cross section of the pipe have a rotation centre more or less far from the theoretic rotation centre that it would have if the longitudinal axis of the pipe should be perfectly straight.

For this reason, the machine 1 according to the present invention comprises measurement means 10 of the distance between them and some points of the outer surface of the pipe, to evaluate the curvature of the pipe in process and its misalignment relatively to the rotation axis A of the mandrels 2 and 3.

The measurement means 10, of which the machine is provided with, are non - contact measurement means, that is they do not need any contact with the surface points of which the distance has to be measured.

Preferably, the non - contact measurement means comprise a distance gauge of the laser triangulation type, better known as triangulator, allowing to obtain high precision measurements, up to a hundredth of millimeter.

Obviously, other measurement means of the distance could be used, not needing any contact with the surface of which the distance has to be measured, for example of the time of flight laser or laser scanner type.

It has to be noticed that, by the distance gauges of the laser triangulation and time of flight laser type, point distance measurements are obtained, that is the distance between the laser gauge and a point over the pipe surface is measured. On the contrary, using a laser scanner, a measurement of the two - dimensional distance on a point array over the pipe surface is carried out.

The assessment of the curvature of the pipe 5 and the misalignment of the rotation centre of each cross section relatively to the rotation axis A of the mandrels 2 and 3, is carried out from the measurements of the distance obtained on points belonging to opposite pipe faces, in case of squared or rectangular section pipes, otherwise on diametrically opposite points for pipes having different shapes, particularly the circular shape.

In detail, in case of a pipe having a squared section, a measurement of the distance on a point over one of the faces is carried out, subsequently the pipe 5 is forced to have a whole semi - rotation by the mandrels, so that the face opposite to that the distance measurement has been before carried out would be in front of the laser measurement means 10.

By doing so, the distance measurement on the opposite point relatively to the previous one is carried out, and the same operation is carried out for the other two faces.

The difference between values of the distance measured on the two opposite faces allows to determine the misalignment of the pipe axis relatively to the rotation axis A of the mandrels.

The operation could be repeated for more points on opposite faces and for more cross sections of the pipe along the X direction. In any case, the values detected by the measurement means 10 are processed by a controlling unit, not shown in figures, interpolating the distance values with mathematical continuous functions, determining the real curvature of the pipe and the misalignment of the rotation centre of each pipe cross section in the cutting zone, relatively to the rotation centre A of the mandrels 2 and 3.

The controlling unit, based on the cutting type to be realized, will change the movement of the tridimensional laser cutting head 4 relatively to the real pipe curvature before detected by the differential measurements of the distance, which are subsequently interpolated.

The presence of the measurement means 10 non contacting the pipe surface 5, and particularly the laser measurement means, allows to quickly obtain the distance in different points of the surface, allowing to obtain accurate measurements of the real pipe curvature, without for this reason slowing down the cutting process.

The machine for cutting pipes according to the present invention further comprises moving means 11 for the distance non - contact measurement means 10, allowing their displacement relatively to the surface of the pipe 5, so that to reach different points of the surface wherein the distance measurement could be carried out.

Particularly, as can be better seen in figures 3 and 4, the laser measurement means 10 are moveable in the space along three orthogonal directions X-Y-Z, by known means for such a use.

In detail, as can be seen in figure 3, the laser measurement means 10 are slidingly constrained on a straight guide 12 by an arm 14.

The sliding over the guide 12 is obtained by a linear actuator 13.

The sliding of the measurement means 10 along the guide 12 will determine their controlled displacement along the X direction parallel to the rotation axis A of the mandrels, as illustrated on the right side of figure 4, wherein the dotted lines are representing the measurement means 10 in different position along the X direction.

In a similar way, the measurement means 10 are moveable along the Y and Z directions.

The movement of the measurement means 10 along the three directions X-Y- Z, allows the cutting head 4 to be followed, so that the measurement means always remain aligned with the point wherein the cutting laser beam will contact, or has contacted, the pipe surface. In fact, as can be seen in figure 4, the tridimensional laser cutting head may change its tilt (a angle in figure 4), relatively to the vertical position wherein the cut is carried out according to the Y direction.

It has to be noticed that, in case wherein a laser scanner is used as a measurement means non contacting the pipe surface, the movement along the Y axis will allow to adapt, and then to improve, the accuracy of the measurement of the pipe surface distance.

In fact the laser scanner, on the contrary of gauges of time of flight laser or laser scanner type, allows to obtain two - dimensional distance measurements along a point array.

Obviously, changing the distance between the pipe surface, on which the measurement has to be carried out, and the laser scanner, that is moving the laser scanner in the Y direction, the measurement accuracy could be modified.

In fact, by moving the laser scanner in the Y direction, the range of the swept length is changed, that is the length of the measurement point array.

Moving the laser scanner closer to the pipe surface, the point array will be less wide with a greater measurement accuracy, and vice versa. As afore mentioned, the machine comprises an electronic controlling unit, not shown in the attached figures, managing, controlling and coordinating the mandrel movement, hence the pipe rotation and feeding, the movement of the cutting head and the movement of the measurement means and the manage of the distance data of the pipe surface detected in different points thereof.

The machine 1 , according to the present invention, further comprises protecting means 20 of the measurement means 10. In detail, the measurement means are housed inside a casing 21 having the function of protecting the fragile and sensible laser measurement system 10 from the remains of the cutting carried out by the laser, that is for example fume, incandescent material, plasma, etc.

In the case wherein the casing 21 , and then the measurement means housed therein, are disposed in proximity of the pipe and the cutting head, the casing 21 may be provided with a shutter, not shown in the attached figures, allowing the laser beam passing for the distance measurement of the pipe surface when the cutting head is not working, for being subsequently closed again when the cutting has been carried out and there is the risk that the process remains would compromise the functionality of the measurement means 10.

The controlling unit has then the further task, by an appropriate software, of controlling the shutter closing and opening to protect the measurement means 10 when the cutting head is working.

The steps of the cutting method of a pipe according to the present invention will be now described. It has to be noticed that in the attached figures a circular section pipe is represented, for only illustrative and not limitative purposes, even if in the machine according to the present invention pipes having different shape in the cross section could be processed, as mentioned.

Particularly, herein are described the steps of the method for obtaining a series of aligned holes at the center line of a pipe face having a squared section.

At first the pipe is loaded into the machine and then it is housed inside the mandrels 2 and 3 and blocked in their inside by the pressure exercised by the clamps 6.

As illustrated in the right side of figure 4, the holes are realized in the cantilevered pipe portion out of the second mandrel 3, in the cutting zone under the 0081

tridimensional laser head 4.

Before the cutting is carried out, the pipe curvature is determined by the laser measurement means 10 performing a series of distance measurements of some points over the pipe surface.

Particularly, the distances of points disposed in an opposed position on the pipe surface are detected and subsequently, by the difference evaluation of the measured value in one or more couples of opposed points , it is possible to determine the misalignment of the rotation centre of that cross section of the pipe relatively to the rotation centre of mandrels A.

In detail, first of all the distance of a point belonging to a pipe face is detected, and then the value is stored in a controlling unit.

Afterwards, the mandrels 2 and 3 cause a semi - rotation of the pipe 5 (rotation of 180°), in such a way that the point disposed in an opposed position relatively to the previous point, that is on the opposite face of the pipe relatively to that wherein the measurement has been carried out before, would be next to the measurement means.

At this point, a distance measurement of the pipe surface in that point is performed and the value is stored.

Such operations could be repeated on different points for every face and the correspondent points on the opposite face, and for different cross section of the pipe in the cutting zone, as shown by the dotted line of figure 4.

The difference in the values measured for points disposed in an opposed position on the pipe surface allow to assess its misalignment and its curvature relatively to the rotations of the mandrels A.

To perform the distance measurement on different cross sections of the pipe, the measurement means 10 are displaced in the X direction by the moving means 1 1, particularly by the controlled sliding along the guide 12.

Once the real geometry of the pipe portion in the cutting zone is detected, and particularly of the curvature thereof, it is possible to proceed with the cutting execution of the surface by the tridimensional laser head 4.

It has to be noticed that the method and the machine according to the present invention allow to carry out further measurements of the distance of the pipe surface in points wherein the cutting has to be performed, to reduce the precision errors caused by the pipe curvature and to improve the accuracy of the carried out measurements to accurately determine the curvature and misalignment of the pipe.

In fact, before doing a hole, the measurement means 10 are moved in such a way to reach the points wherein the cutting will be carried out and they perform further distance measurements.

These values are compared with the before measured values and the point curvature obtained by interpolation.

By doing so, the cutting head may be accurately controlled and adapted to the real pipe curvature to avoid the precision and positioning errors of the obtained cutting, complained in the cutting machines and methods used in the known art.

In addition, the method provides to verify and control the performed cutting quality and the correctness and precision thereof by the measurement means 10, when the cutting operations have ended.

In fact, the pipe face on which the series of holes has been realized is aligned with the measurement means, by the mandrel rotation.

Some further measurements are realized, for example to evaluate the correct alignment of the holes and their arrangement on the pipe face.

In other words, the control and check are carried out comparing the geometrical real data detected by the measurement means and the theoretical parameters of the cutting program performed by the machine.

For example, in case of executing a hole onto the pipe surface, the measurement means will detect the real hole dimensions and its position on the pipe face, when the cutting operations have ended. These geometrical data are automatically compared with the theoretical geometrical data of the cutting program performed by the machine and then with the position, dimension and tolerance data for the hole to be realized.

Further, the non - contact measurement means of the machine according to the present invention, allow to automatically and simply and rapidly check if the parting of a portion pipe to be cut has been correctly carried out and if the detachment of the pipe portion has really occurred. In fact, in the machines for cutting pipes it is possible that the cutting will be not correctly performed -and a lip of the pipe portion to be parted will remain anchored with the remaining pipe in process in the machine, with consequent problems coming from the pipe rotation in process and the portion not - detached therefrom that could contact the cutting head causing the breaking thereof.

By the non - contact measurement means of the machine according to the present invention, it is possible to carry out the distance measurement few millimeters outside (in the X direction) relatively to the point wherein the cutting of the pipe portion should be performed. If the cutting is correctly carried out, and then the pipe portion has been correctly detached, the measurement means do not detect any body presence thereby reporting a distance measurement equal to the end - of - scale value of the tool.

It has to be noticed that, although it has referred to a cutting head of laser type, the machine according to the present invention may be provided with a laser welding head for carrying out the welding machining on the pipe surface. Also in this case, the real pipe curvature detected by the differential distance measurements on diametrically opposite points on the pipe surface, allows to adapt the welding head movement to avoid problems of accuracy lack.

Claims

1. Machine for carrying out the cutting or welding of / on the surface of pipes, of the type comprising at least one mandrel (2, 3) for supporting and displacing said pipe (5) during the machining, and at least one cutting or welding head (4) for emitting a laser beam adapted to carry out the cutting or welding of / on the surface of the pipe, said pipe (5) being rotated and shifted by at least one mandrel around / along the rotation axis of the mandrel (A), characterized by comprising measurement means (10) non - contacting the surface of said pipe, for measuring the distance between said measurement means and at least one point of the surface of said pipe.

2. Machine according to claim 1 , characterized in that said measurement means ( 0) non - contacting the surface of said pipe are of laser type.

3. Machine according to claim 2, wherein said measurement means of laser type are selected between laser triangulation, time of flight laser and laser scanner.

4. Machine according to claim 1 , characterized by comprising means ( 1) for moving said measurement means (10) in different measurement positions relatively to the surface of said pipe.

5. Machine according to claim 4, wherein said means ( 1 ) for moving said measurement means (10) allow the movement in the space along three orthogonal directions X-Y-Z.

6. Machine according to claims 4 and 5, wherein said means (11) for moving said measurement means comprise at least one straight guide (12) disposed parallel to the rotation axis (A) of said at least one mandrel (2, 3), at least one linear actuator (13) and at least one arm (14) for constraining said measurement means (10) to said at least one straight guide (12).

7. Machine according to any one of the preceding claims, characterized by comprising protecting means (20) for housing in their inside said measurement means (10) non - contacting the surface of said pipe.

8. Machine according to claim 7, wherein said protecting means (20) comprise at least one casing (21) for housing said measurement means (10).

9. Machine according to claim 8, wherein said at least one casing (21) is provided with at least one shutter for allowing the measurement carrying out when said cutting or welding head (4) is not working and protecting said measurement means when said cutting or welding head (4) is working.

10. Method for carrying out the cutting or welding of / on the surface of pipes, particularly by a machine according to at least one of the claims from 1 to 9, comprising the steps of:

- housing and blocking a pipe (5) in at least one mandrel (2, 3) of said machine;

- shifting and rotating under control the pipe (5) along / around an axis (A) by at least one mandrel (2, 3);

- carrying out the cutting or welding of / on said pipe (5) by a laser beam emitted by at least one laser cutting or welding head (4);

characterized by comprising the step of measuring the distance of at least one point on the surface of said pipe (5) by the distance measurement means (10) non - contacting the surface of said pipe (5).

11. Method according to claim 10, characterized by comprising the step of measuring the distance of the surface of said pipe by said non - contact measurement means (10) in points placed in opposed position on said pipe surface.

12. Method according to claim 10 or 11, wherein said step of measuring the distance of the surface of said pipe (10) by said non - contact measurement means (10) occurs before carrying out the step of cutting or welding of / on said pipe.

13. Method according to claim 11 , characterized by comprising the step of determining the curvature of said pipe by a controlling unit based on the difference of the distance values from the pipe surface, measured in points placed in opposed position on said pipe surface.

14. Method according to claim 13, characterized by moving the cutting or welding head (4) during the cutting or welding step based on the curvature of the pipe (5) determined by the difference of the distance values from the pipe surface, measured in points placed in opposed position over said pipe surface.

15. Method according to any one of the preceding claims, characterized by comprising the further step of moving the measurement means (10) non - contacting the surface of said pipe (5) in the same position of the cutting or welding head during the cutting or welding step and carrying out measurements of the distance before the head (4) carried out the cutting or welding.

16. Method according to any one of the preceding claims, characterized by comprising a further controlling and checking step following said cutting or welding step, wherein the cutting or welding carried out are checked and controlled by said measurement means (10) non contacting the surface of said pipe.

17. Method according to claim 16, characterized in that in said checking and controlling step the non - contact measurement means detect real geometrical data of the carried out cutting or welding, said real geometrical data being compared to the theoretic geometrical data of cutting or welding carried out by the machine.