MC200031A1 - Transportable and open device incorporating a self-adapting laser head for cutting or welding pipe sections from a pipeline on land or at sea using a laser generator - Google Patents

Abstract

Transportable, open device integrating an auto-adaptive laser head for cutting off or welding sections of tubes of a terrestrial or marine ducting using a laser generator.The laser device is composed of a frame B, a support B1, a motorised rotor 1 which drives the arm C1, a motorised rotor 2 which drives the arm C2 and a motorised rotor 3 which drives the head T and keeps it normal to the tube. The arms C1 and C2 are shown at the start of the cycle. The head T integrates a focus head fixed onto a crossed table guided by 2 motorized axes to automatically compensate geometrical defects of the tube and the positioning of the device with respect to the ducting. A clamping jaw P enables the device to be approximately positioned with respect to the tube.<IMAGE>

Description

20 0 0 3 1

IUPUCATA

January 1, 2001

#10 35

Patent of invention

A portable and open device, incorporating a self-adapting laser head, for cutting or welding sections of pipes in a pipeline on land or at sea using a laser generator.

Applicant's name: Michel Gareaux

The present invention aims to weld and cut any inscribed object in any cylinder corresponding to the dimensions of the device's strokes with a multikilowatt CO2 laser.

The present invention is in particular intended for welding and cutting pipes for the transport of fluids or gases both on land and at sea.

The originality of this invention compared to existing or developing laser devices is that it is an open, compact and lightweight system, therefore easily transportable and cheaper to manufacture.

The system is open because the two arms, of equal length, which guide the laser beam and drive the laser head, are motorized. They do not need to be driven by a closed bearing track. This allows the system to complete a full rotation cycle at any point along an infinitely long pipeline for repair, cutting, or welding.

The system is compact and lightweight because, for example, machining a 600mm diameter tube weighs approximately 500 kg and folds down to a volume of 1 cubic meter. This allows the system to be easily attached to a pipeline without inertia issues, unlike moving a much heavier machine.

The present invention aims to perform, using a CO2 laser beam, 20 automatic cuts and welds on sections of tubes, for example, which can have large diameters, with a device that is easily transportable and resistant to harsh environmental conditions.

The cycle of this motorized compass consists of rotating a laser head, focusing the beam, one full rotation plus a few additional degrees for the weld overlap, while maintaining it perpendicular to the surface of the tube to be cut or welded. The angular displacement of the

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The first motor drive, which drives the primary arm relative to the frame, will have an angular displacement of approximately 275°. The second motor drive, which drives the secondary arm relative to the primary arm, will have the same angular displacement. The third motor drive, which pulls the laser head 5 relative to the secondary arm, will have an angular displacement of approximately 365°.

These 3 motors will be controlled by a programmable digital control so that it makes the laser head describe a perfect circle at a programmed speed.

We know that CO2 laser welding produces a very thin weld bead and a small heat-affected zone. Therefore, precise tracking of the two parts being welded is essential. We will call this tracking of both edges "joint tracking," a term commonly used in the industry. It is also necessary to maintain a constant distance between the laser head and the tube surface. We will call this tracking "skin tracking."

15 However, we saw in the cycle of 3 rotations that our device described a perfect circle, which cannot be the case in reality: a tube is never perfectly round; the joint plane is never perpendicular to the theoretical axis of the machine; the tube is never perfectly positioned relative to the device. These considerations led us to add two additional axes to the laser head 20 itself, and we will call it the self-adaptive laser head.

This "self-adapting" laser head is unique in that it is equipped with two independent axes at 90° called X and Z to ensure "skin tracking," i.e., the distance of the nozzle from the material to be cut or welded, as well as "joint tracking," i.e., following the precise path that the head must follow, materialized by the two materials placed edge to edge or materialized by any trace on the parts to be welded; this trace will be read by an electromagnetic detector or preferably by a laser camera or a matrix CCD camera; the chosen reader will be mounted upstream of the focusing nozzle on the laser head and will allow, by means of a computer integrated into the numerical control, to control in a closed circuit and automatically, without programming, the skin tracking and the joint tracking, i.e. the X and Z axes integrated in the self-adapting laser head.

The motorized compass with the self-adaptive laser head will make it possible to compensate for positioning errors of the tube to be cut or welded relative to the device, within the limit of the stroke of the 2 integrated axes of the head which is on the order of 200 mm in the description of the device that we are going to make.

The device, the subject of the practical application of this invention, will be easily transportable and usable in difficult environments such as on an offshore pipe-laying vessel or on an onshore pipe-laying truck. The laser source and motorized compass assembly, equipped with its laser head, will be

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attached to the same building.

The device will be brought to an approximate position within 50 mm of the joint plane to be welded by means of a motorized platform on a laying truck for use on land.

5 In the event of possible movement of the tube during the welding operation, on a boat in heavy swell, it can be equipped with guide rails which will allow the device to be attached to the tube by mechanical clamping or to be controlled by a motor and a detector for tracking the joint of the tube.

Apart from this coupling, no contact with the tube is required.

10. Welding or cutting is carried out in one or more passes depending on the thickness of the tube and whether or not filler wire is used. Generally speaking, with a 15 kW laser source, it is possible to weld up to 15 mm thick in one pass.

In practice, the sections of pipe to be welded are held edge to edge, the

15 welding steps, using an internal expanding mandrel, a classic device called a "CLAMP" in the profession.

The cutting will be performed with the same laser head used for welding. Only the assist gas will be changed. This head will allow for repairs, such as cutting out a crown containing a part

20 defective or carry out the dismantling of a pipeline.

A device designed according to the invention will be described below, with the option of a coupling in case the tube is likely to move relative to the device during cutting or welding, by referring to the figures in the attached drawings on which:

25 - Fig. 1 is a general diagram of the elevated device for machining pipes without untimely movement of the tube during the welding operation, mounted on the ground for example.

- Fig. 2 is a diagram of the same device on the left hand.

- Fig. 3 is a top view cross-section of the machine where are

30 represented, including the equipped arms and the self-adapting laser head.

- Fig. 4 and Fig. 5 represent 2 cross-sections of the self-adaptive laser head.

- Fig. 6 is a variant of the device where the optical path and its mechanical components can be attached to the pipe when the latter is likely to move during machining.

35 The following description will allow us to refine the specific characteristics of the invention.

The device shown in elevation in Fig. 1 is mainly composed of

of a very rigid and stabilized B0 frame on which the laser source and the Bl frame are attached.

40 The frame Bl is designed to support the first rotation 1 which is equipped with

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Its hollow-shaft geared motor M1, coupled to a high-precision spindle, is centered on which the laser beam enters the device. The rotating shaft M1 is attached to the first arm of the compass C1, at the end of which is the second motorized rotation 2, which is attached to the second arm of the compass C2. At the end of this second arm is the third rotation 3, attached to the laser head T. Fig. 1 represents the device at the beginning of the cycle on a tube V.

Fig. 2 is the side view of Fig. 1, where the device is also shown at the start of the cycle, with the added path 7 that rotation 2 will follow for a complete cycle, as well as the position of arms C1 and C2 at the end of the cycle, shown as dashed lines 8 and 9 respectively. Note that the head T is in the same position at the start of the cycle as at its end.

The P pad, mounted on a spring damper, will allow the device to be roughly positioned in relation to the pipe to be cut or welded.

The laser beam therefore enters the device at the center of the hollow shaft motor Ml (fig.3) which drives the hollow shaft reducer 1, itself driving the high precision hollow shaft spindle 4. The spindle shaft is fixed to the arm Cl.

A plane mirror RI reflects the laser beam onto the mirror R

Inside the arm Cl, at the end of which is the second rotation 2 equipped with a hollow shaft reducer driving the high-precision spindle

5 and powered by the M2 motor via a belt on the primary drive of the reducer.

The spindle shaft 5 is attached to the second arm C2 and drives it in rotation; at its end is fixed the third rotation 3, consisting of its hollow shaft reducer driving the rotation spindle 6. The shaft of the latter drives the head T in rotation.

The laser beam, arriving at R3 via the center of the hollow pin, is then reflected at 90° onto R4, and then again via the center of the hollow pin.

6 is reflected on the mirror R5 of the head T to arrive on the last plane mirror R6 of the optical path.

Figure 5, a cross-section of the laser head T, shows the flat mirror R6, which is attached to the table 12. This table 12 moves linearly along the Z-axis on high-precision prismatic slides 16 via ball bearings 17, with a stroke of approximately 200 mm in this representation. It is driven by a ball screw 18, a belt and toothed pulleys 19, and its motor M4, shown in Figure 4. Regardless of the position of the table 12, mirror R6 always faces mirror R5 at the same angle and thus reflects the laser beam onto the mirror.

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parabolic R7 which has a focal length of 300 mm in this representation.

The parabolic mirror is itself fixed to the second table 13 via the focusing chamber T1; Table 13 is attached to Table 12 by means of two prismatic slides 20 on two ball bearings 21, such that it is free to translate along the X-axis, which in this representation has a travel of 50 mm. This table 13 will be driven by a micro motor with an integrated ball screw M5.

The detector 10, here represented by a laser camera, is mechanically fixed 10 to the extension 22 attached to the focusing chamber T1. This detector will control in a closed loop the motors M4 of the Z axis and M5 of the X axis in such a way that the focal height relative to the workpiece is constant, as well as the joint to be followed along the X axis.

Fig. 6 represents a variant of the device, seen in elevation where the frame B0 has been lengthened and on which 2 rectified slides 24 have been fixed. The compass support frame Bl is then equipped with pads 25 allowing it to move in translation on the slides 24 shown here with a length of 3 m with a precision of 1/100th of a mm per meter, so that the beam produced by the laser source L always passes through the center of rotation RI, without 20 significant angular variation.

As a safety measure and to prevent any dust penetration, a protective bellows 23 was installed between the source L and the beam arrival on the mobile frame Bl.

The mobile frame Bl is then mechanically secured to the pipe with 2 jaws or any other 25-point fixing. This mechanical fixing can be replaced by a detector fixed to the frame that reads a path to follow on the pipe and drives a motor that moves the mobile part of the device to within 1/10th of a millimeter.

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Claims (5)

DEMANDS 1. Device using a laser generator L to cut or weld any pipe, which can be of infinite length, by intervening at any location of it, characterized by two support arms Cl and C2 and a laser beam focusing head T, which are each driven in rotation by three motorized hollow shaft pins 1, 2, and 3, allowing the device to fold its arms by acting on a manual control of the 10 motors or by programming a specific sequence on the numerical control, before putting the laser head T into working position and making it describe a circle around the pipe while keeping it at the normal of the surface of the tube to be machined; the laser beam from its generator L is transported to the laser head T where it is focused by a parabolic mirror R7 after being previously reflected by six plane mirrors RI R2 R3 R4 R5 R6 and passing through the center of the hollow shaft pins inside the support arms and the head T. 2. Device according to claim 1, wherein the arms C1 and C2 are self-supporting and carry the laser beam via reflective plane mirrors, located on each side and at the center of each rotation, which are motorized. 20 independently; these arms have sufficient rigidity so that there is no deformation that could significantly deflect the laser beam which is carried to the head. 3. Device according to claims 1 and 2 which is open and capable of working on a pipeline of infinite length, thanks to motorized arms and 25 self-supporting units inside which the optical path progresses to the laser head by passing through the center of rotation of the hollow pins coupled to geared motors also with hollow shafts, linking in rotation the frame Bl to the arm Cl then to the arm C2 and finally to the laser head T. 4. Device according to claims 1 to 3 sufficiently compact and lightweight 30 to be installed on a self-elevating truck platform or to be attached to a pipeline that undergoes unwanted movement during machining on a pipe-laying vessel, for example, as shown in Fig. 6; in this application, the attachment may be mechanical with clamping jaws P in Fig. 2 which will only drive the frame Bl, its telescopic optical path, the two arms with the laser head; it is understood that the device thus positioned will only be in an approximate manner, to within about 80 mm, but that the detector 10 fixed on the head T will position itself on the joint surface and automatically compensate for both the defects of the joint surface to be welded and the positioning of the device relative to the pipeline to be machined, this within the limits of 7 travels of the two axes of the T head, provided for this purpose and which are 200 mm in classic use. 5. Self-adaptive laser head T according to claims 1 to 4 integrating two axes X and Z allowing to be controlled independently of the cycle of the 3 axes of rotation of the arms Cl and C2 of the device and which will automatically compensate for the defects of following the joint plane to be welded as well as it will maintain a constant distance of the laser head from the skin of the tube to within 1/1th of a mm. 10 15 20 25 30 35 40