Metal container having trunk pipe and branch pipe and its manufacturing method.

Abstract: A welded metal container for a sheath (A) or (1A) of gas insulated switch gear comprises a trunk pipe (2, 21) and a branch pipe (3, 31, 32) welded to the trunk pipe (2, 21) by arc welding (A) or laser beam welding (LB) and flanges welded to the each end portion of the trunk pipe (2, 21) and branch pipes (3, 31, 32) by the laser beam welding. After the arc welding (A), the ends of trunk pipe (2, 21) and branch pipes (3, 31, 32) are machined precisely and flanges (4a, 4b, 4c, 4d, 4f and 4g) are welded to the end portions of the trunk pipe (2, 21) and branch pipes (3, 31, 32).

Description: The present invention relates to a metal container having a trunk pipe and branch pipe, such as a sheath of gas insulated switch gear, and particularly to a structure of welded metal container having a trunk pipe and branch pipe welded thereto and flanges welded to the each end portion of the trunk pipe and branch pipe, and manufacturing method and apparatus therefor. In manufacturing a metal container having a trunk pipe and branch pipe, for example, a sheath of gas insulated switch gear which has a lot of pipes welded to the trunk pipe, it requires to weld flanges to end portions of the branch pipe and trunk pipe with accuracy. Arc welding is used for the above purpose. In the welding, however, this arc welding requires a complete penetration welding so as to ensure the gas-tightness. The flange faces have to be machined after welding when high accuracy is required. The laser welding is used for joining pipe and flanges, as disclosed in Japanese laid-open patent publication No. 59-189092/1984, processing of LAMP'87, Osaka (May, 1987), page 157 ∼ page 162 "Deep Penetration welding with High Power Co Laser" by seigo HIRAMOTO et al and Mitsubishi Denki giho, No. 10, 1989, page 37 ∼ 40. The aforementioned prior arts paid no attention to disclose the working method, in which the joint between the flanges and trunk pipe is merely changed from the arc welding to the laser welding. No consideration is taken into the structure and manufacture of the actual metallic containers, namely the widely used metal container having a branch pipe such as the gas insulated switch gear sheath having many branch pipes. Therefore, the arc welding is still used for manufacturing the metallic container having the branch pipe. When the trunk pipe and the flange are bonded by arc welding, the flange may fall down due to the welding heat and a restrain has to be given. For example, when the following conditions of the welding, diameter of the trunk pipe: 600mm, length of the trunk pipe: 2,000mm, thickness of the trunk pipe: 6mm ∼ 12mm, weld width(bead width): 6mm ∼ 8mm, the welded flange is inclined or felt down by around 2mm. Therefore, inaccurateness in the degree of parallelization and perpendicularity occurs. In order to enhance the accuracy of the container, the flange have to be machined after welded, and the machining results in a problem of troublesomeness. Unless the ends of the branch pipe and the trunk pipe are machined precisely after welded, they are difficult to be weld to the flanges. This makes it necessary to machine the ends, but the flanges are inevitably deformed when welded. Therefore, it is necessary to maintain the accuracy of the flange by machining the same so as to set the flatness of the flange surface and distance between flanges to suitable levels and eliminate the inclination of the flange surface after welding operation. This raises a serious problem in the production. The prior arts requires a large-sized machine for machining the flanges in case the container is large. This necessity dilutes the effects of accomplishing the machine before the welding. However, this dilution is not taken into consideration to raise another serious problem in case of the large sized container. In addition, in the conventional techniques, a recess of 0.2-3 mm in depth is provided in the flange, and an end portion of the pipe is inserted in this recess. A laser beam is applied to the portion to be welded, in the direction to carry out the laser welding of the workpieces while rotating the same. The angle at which the laser beam is applied to the surfaces to be welded, about 3-20°. That is, a laser beam is applied diagonally to the surfaces to be welded. Therefore, the depth of penetration of the flange and pipe becomes uneven, and perfect penetration bead weld cannot be obtained in some cases in one pass (one welding operation). In general, the outer diameter of a pipe has tolerance of ±1% according to the Japanese Industrial Standards. Therefore, even when a recess of a nominal pipe diameter is cut in one surface of a flange, it becomes difficult to insert a pipe, the outer diameter of which has certain tolerance, in the recess in the flange or a clearance between the pipe and recess becomes large even if the pipe fits in the recess, so that such flange and pipe become unsuitable to be welded in some cases. Accordingly, if a pipe of about 50 mm (about 2 inches) in diameter is welded to a flange by using the above-described conventional welding techniques, the pipe can be inserted in the recess in the flange owing to the small tolerance of this diameter and the welding can be done suitably. However, when a large-sized pipe having a diameter of, for example, around 744 mm is used, the welding thereof to a flange cannot be done suitably in many cases since this pipe has tolerance of as large as ±7.4 mm. A laser machining apparatus for cutting or welding a workpiece by making use of a laser beam coming from a laser oscillator is disclosed in Japanese Laid-Open Patent Publication No. 60-227987/1985, for example. A machining table is sequentially arranged thereon with a welding head, a cutting head and a heat treatment head and is underlaid by a laser oscillator so that the workpiece can be moved in the same direction as a laser beam outputted from the laser oscillator. Moreover, the welding head and the cutting head on the machining table can be moved at a right angle with respect to the output direction of the laser beam. In machining application of the workpiece, either the welding head or the welding head and the cutting head are moved at a right angle with respect to the output direction of the laser beam so that the laser beam may not be obstructed but can enter the machining head. The workpiece is so moved that the workpiece may be positioned just below the machining head in operation. Since the individual machining heads are independently fixed on the machining table in accordance with the aforementioned prior art, the machining heads have to be moved each time according to the machining application of the workpiece, and the workpiece has to be positioned just below the machining head in accordance with the machining application, thus raising a problem in the machinability. Moreover, the individual machining heads need not be spaced so long, if the workpiece is small, but has to be spaced long if the workpiece is large. As a result, there arises a defect that the system is enlarged in its entirety. When the machining head once moved is returned to its initial position before a predetermined machining, it is necessary to align the optical axis of the laser beam coming from the laser oscillator and the center of a bend mirror which is disposed in the machining head to change the path of the aforementioned laser beam. This alignment is difficult, and it is seriously troublesome to position the moved machining head for each machining. Still the worse, the aforementioned prior art has taken consideration neither into the cutting of the end face of the tubular container such as the bus of the gas insulation control apparatus nor into the correction of that gap between the pipe end and the flange groove, which never fails to occur in the actual welding, and the correction of the dislocation. Summary of the Invention One object of the present invention is to provide a welded metal container, such as a sheath of an insulated switch gear, in which flanges are joined in high accuracy and a reduced number of steps to the individual ends of the trunk pipe and the branch pipe bonded to the trunk pipe by the welding operation. This object is accomplished by the welded metal container defined in claim 1. Another object of the present invention is to provide a method of producing tubular containers, capable of minimizing the welding deformation of even a branch pipe-carrying container in which flanges are joined to the end portions of a trunk pipe and branch pipes, reducing the manhour with a machining operation, which is carried out after the welding of flanges to pipes in a conventional method of this kind, omitted, and thereby obtaining a highly accurate welded tubular container. This object is achieved by the method defined in claim 2. According to an embodiment of the present invention, a trunk pipe and a branch pipe are thermally deformed when they are jointed together by arc welding. However, after the deformed portions are mechanically processed to increase the accuracy of the pipes to a proper level, flanges can be jointed to the end portions of the same pipes by laser beam welding which causes minimum thermal deformation. Therefore, it is unnecessary to carry out a machining process after the pipes and flanges are finally welded, and a highly accurate tubular container can be obtained with fewer manhour. Especially, in the case of production of a sheath for a device formed by combining a plurality of machines, such as a gas insulating switch device, these advantages are more markedly displayed. Brief Description of the Drawings Fig. 1 is a perspective view showing one embodiment of the welded metal container of the present invention. Fig. 2 is a perspective view showing another embodiment of the welded metal container of the present invention. Fig. 3 is a sectional view of Fig.2. Fig. 4 is a sectional view showing the jointed portion of the trunk pipe end and the flange. Fig. 5 is a sectional view showing the jointed portion of the branch pipe end and the flange. Fig. 6 is a top plan view showing the gas insulated switch gear according the present invention. Fig. 7 is a front elevational view along a line A in Fig. 7. Fig. 8 is a flow chart showing the production of the pressure container for a gas insulated switch gear, which constitutes of an embodiment of the method of producing tubular container according to the present invention. Figs. 9a to 9c are sectional views of various shapes of welded joints used for a tubular container. Figs. 10 and 11 illustrate methods of cutting a pipe end surface in a tubular in the embodiment of present invention. Figs. 12a to 12c is sectional view showing the steps of welding a pipe and a flange to each other by the welding method of an embodiment. Fig. 13 is a sectional view illustrating an applied example of the welding method of the embodiment. Figs. 14 and 15 illustrate the welding apparatus of the other embodiments. Fig. 16 is a perspective view showing one embodiment of the whole structure of the laser machining system of the present invention. Fig. 17 is a front elevational view showing the machining apparatus to be used in the laser machining system. Fig. 18 is a top plan view of Fig. 2. Fig. 19 is a sectional view showing the positioning device to be used of the system of the present embodiment. Fig. 20 a side elevational view taken in the P direction from Fig. 19. Fig. 21 is a sectional view showing a portion of the butting portions of the trunk pipe and the flange in detail. Fig. 22 illustrates a dislocation measuring method practiced by an embodiment of the edge aligning mechanism according to the present invention. Fig. 23 is a flow chart showing the steps of attaching the trunk pipe and the flanges. Fig. 24 is a view taken along the line A-A in Fig. 17. Fig. 25 is a sectional view in case the aperture is small. Fig. 26 is a view taken in the direction B-B in Fig. 25. Figs. 27a to 27d is a flow chart showing the machining steps in case the flanges are to be attached to the branched trunk pipe. Fig. 28 is a perspective view showing the whole structure of another embodiment of the laser machining system of the present invention. Detailed Description of the Preferred Embodiments Fig. 1 shows one embodiment of the present invention. A sheath 1 used for a gas insulated switch gear is composed of a trunk or main pipe 2, branch pipes 3 and 31 jointed generally at a right angle with respect to the axial direction of the trunk pipe 2 by an arc welding as indicated at A, flanges 4a and 4b jointed to the two ends of the trunk pipe 2, flanges 4c and 4d jointed to the ends of the branch pipes 3 and 31. The sheath 1 is constructed by bonding the trunk pipe 2 to the flanges 4a and 4b and bonding the branch pipes 3 and 31 to the flanges 4c and 4d by the laser beam welding LB. In the present embodiment, the thermal deformations by the arc welding A are solved by carrying out the laser beam welding after the arc welding A. After the arc welding A, end portions of the trunk pipe 2 and branch pipes 3 and 31 are machined precisely and flanges 4a, 4b, 4c and 4d are welded to the end portions of the trunk pipe 2 and branch pipes 3 and 31 by the laser beam welding LB. As a result, the sheath 1 obtained can be highly accurate and the workability and the assembly accuracy can be improved in assembling the sheath 1. For example, when the following conditions of the welding, diameter of the trunk pipe: 600mm, length of the trunk pipe: 2,000mm, thickness of the trunk pipe: 4.5mm ∼ 12mm, weld width(bead width): 2mm ∼ 3mm, Laser output: 5Kw ∼ 10Kw the flange welded by the laser beam is inclined or felt down by around 0.3mm. Therefore, accurateness in the degree of parallelization and perpendicularity is trunktained. In Fig. 2 and Fig. 3 showing a second embodiment of the present invention, a sheath 1A comprises a trunk pipe or trunk pipe 21, a branch pipe 32 jointed to the trunk pipe 21, the flanges 4e, 4f and 4g jointed individually to the two ends of the trunk pipe and the end of the branch pipe 3 and stays 5 and 51. In the present embodiment, the laser beam welding LB is applied to the joints between the trunk pipe 21 and the flanges 4e and 4f, between the branch pipe 32 and flange 4g, between trunk pipe 21 and the stays 5 and 51, and between the trunk pipe 21 and the branch pipe 32. The laser beam welding is not suitable in applying to a corner portion. In case of the embodiment shown in Fig. 2 and Fig. 3, the end portion of the branch pipe 32 is flared in advance, and the branch pipe 32 is bonded to the trunk pipe 21 by the laser beam welding LB. As a result, it is easy to apply an automatic welding system with a low strain and to produce a high accurate sheath. Incidentally, the sections of the joints between the flange 4e and the trunk pipe 21 and between the flange 4g and the branch pipe 32 are shown in detail in Figs. 4 and 5, respectively. As shown, not only the end of the trunk pipe and the flanges 4e, and the end of the branch pipe 32 and the flanges 4g are welded by the laser beam, but also the corners are fillet-welded from the inside and outside by the laser beam welding LB. Thus the fall of the flanges 4e and 4g are reduced in comparison with those of the arc welding and the cost required in pre-straining, shaping, and machining works after the welding operations is reduced. Fig. 6 and 7 show an example, in which the present invention is applied to a gas insulated switch gear (hereinafter referred to as "GIS"). The GIS is constructed of a breaker 11, a disconnector 13, an arrester 14 and a single phase bus 15. In these units, a trunk circuit conductor 17 of three phase bus 16 is supported by an insulator in the sheath 1 having the welded structure shown in Fig. 1 and has a structure in which a space is sealed with highly insulating SF gases. The individual units are connected through the flange 4a to 4g of the individual sheath 1 by means of bolts. Usually, the containers are sealed with the SF gases under 4 to 5 atms. This confinement may be performed at the time of installation. The flanges 4a to 4g of the sheath 1 are required to have both a flatness for ensuring the contactness thereof and effecting the sealing properties of an O-ring and the rectangularities with respect to the flanges 4c, 4d and 4g of the branch pipes 3, 31 and 32 which extend at a right angle from the other sheath 1 positioned below the trunk pipe 2 and 21 on the axis of the breaker 11 and covering the conductor 17 of the trunk bus and with respect to the flange 4a, 4b, 4e and 4f of the last-mentioned trunk pipe 2 and 21 of the other sheath 1. In the present embodiment, the sheath for accommodating each device adopts the structure, in which the trunk pipe and the flanges, and the branch pipe and the flanges are welded by the laser beam welding. As a result, the aforementioned accuracy can be easily achieved to improve the efficiency of the assembly. Fig. 8 shows a flow chart of the production process of the sheath 1 and 1A (container) for GIS as shown in FIGs. 1 and 2. A sheath for GIS is divided into four members, i.e. a trunk pipe 121, a branch pipe 122, trunk pipe flanges 109 and a branch pipe flange 110. Each member is prepared independently, and a bore for connecting the branch pipe 122 is made in the trunk pipe 121 in a subsequent step. The branch pipe is cut so that the shape of a joint end portion thereof corresponds to that of the bore made in the trunk pipe 121. Connecting bores are made in trunk pipe flanges 109 and a branch pipe flange 110, these flanges being then subjected to surface finishing and a process corresponding to the use of the sheath. The trunk pipe 121 and branch pipe 122 are then joined together by arc welding, and the end portion of the arc welded trunk pipe 121 and the branch pipe 122 are cut by the laser beam or machined in a subsequent step as shown in Fig. 8. The bored and surface finished trunk pipe flanges 109 and the branch pipe flange 110 are then joined by laser welding to the laser cut or machined end portions of the trunk pipe 121 and branch pipe 122 to produce a tubular sheath. As welded structural members as shown in Fig. 9a, 9b and 9c, a T-shape joint in which a pipe end is welded to an end surface of a flange, and a butt joint in which pipe ends are abutted on and welded to each other. Since the bevel portions of these joints are mechanically processed as shown in the drawings, the accuracy of the joints is improved, and the laser welding can be applied. This can prevent the welding deformation of the joints. Accordingly, even when a flange including a surface thereof to be sealed is mechanically processed in advance, and then welded by laser beam, the function of a sealed sheath can be trunktained. In the case where the direction and size of the flange surface do not require a high accuracy with respect to a trunk pipe 101 as in a branch pipe for constituting a manhole, the branch pipe 12 and flange member 13 for forming the manhole are joined together in advance by arc welding, and the manhole-forming flange 113 is then mechanically processed. The resultant flange 113 is arc welded to the trunk pipe 1, and a product thus obtained is then subjected to the same steps as shown in Fig. 8. Fig. 10 shows an example of a means for cutting an end surface of the pipe shown in Fig. 8, in which the end portion of a branch pipe-carrying trunk pipe 221 is cut by applying the laser beam from a laser oscillator 214 to the end surface via a processing head 215 while tuning the branch pipe-carrying trunk pipe 230. The workpiece is positioned by a positioner 240. Fig. 11 shows an example of a means for cutting an end surface of the pipe shown in Fig. 8, in which the end portion of a branch pipe-carrying trunk pipe 230 is cut by applying the laser beam to the end surface while turning a laser processing head 152 .The advantage of the laser cutting resides in that a highly accurate cut surface can be obtained by making a full turn of an object pipe or processing head irrespective of the cutting length of a pipe end surface. According to this embodiment described above, a flange can be mechanically processed in the form of a single part. Therefore, a flange can be processed singularly in an intensive manner, and a comparatively small-sized processing machine can be used. This enables the set up time which is not included in the cutting time to be saved. Since the pipe member plate working and welding step and flange machining step can be carried out simultaneously, the sheath producing period can be reduced around 40%. In addition, the time required for a pipe shaping operation carried out after a branch pipe is welded to a trunk pipe can also be reduced by around 50-70% since the bending of the trunk pipe and the inclination of the branch pipe can be eliminated by the mechanical processing or laser cutting of the pipe end surface. Fig.12a, 12b, and 12c are sectional views showing the steps of welding a pipe 301 and a flange 302 to each other by a welding method. Fig. 13 is a sectional view illustrating an example to which the welding method of this embodiment is applied. Fig.12a shows the condition of the pipe 301 and flange 302 not yet subjected to a welding process. The two surfaces 302a and 302b of the flange are parallel as shown in the drawing. Fig. 12b shows the flange 302 tapered by cutting off the portion thereof shown by broken lines 303. If the flange 302 is processed in this manner, the surface thereof which is opposed to a surface 306b of the pipe 301 to be welded becomes parallel at a portion 306a to be welded thereof alone to the surface 306b. The angle of inclination of this tapering surface is set to about 9°. Fig. 12C shows the tapered flange 302 and pipe 301 abutted on and laser welded to each other. Since the flange 302 is tapered, a laser beam can be applied in the direction of an arrow 304 to the surfaces 306a and 306b to be welded. As a result, the depth of penetration 305 shown by a broken line of the welded surfaces 306a and 306b become substantially uniform. If the flange and pipe are machined at their surfaces to be welded to a predetermined surface accuracy and then subjected to welding, they can be complete penetration within one pass. Even when the outer diameter of the pipe has tolerance, the surfaces 306a, 306b to be welded of the flange 302 and pipe 301 have no clearance therebetween. Therefore, a stable laser welding operation can be carried out. Fig. 13 is a sectional view of a principal portion of a branch pipe-carrying pressure container 330, an example to which the above embodiment is applied. This pressure container 330 is a pressure container for GiS used for a gas insulating transformation machine which is used with an insulating gas, such as SF gas sealed therein. The pressure container 330 consists of two perpendicularly crossing pipes 331, 333, and flanges 332a, 332b, 333a welded to the end surfaces of these pipes 331, 333. If the welding method of the embodiment described in Fig. 12a to 12c is used for welding the flanges 332a, 332b and 333a to the pipes, they can be laser welded reliably and the leakage of the insulating gas can be prevented. Fig. 14 illustrates a welding apparatus of the embodiment. This welding apparatus 340 is provided with a fixed base 341, a rotary unit 342 and 342' set on the fixed base 341, a rotary disc 343 adapted to be rotated by the rotary unit 342, and two opposed rotary units 344, 345 set on the rotary disc 343, and the axis of rotation of the rotary disc and that of rotation of a member rotated by the two rotary units 344, 345 cross each other perpendicularly. A material to be welded is set as a member rotated by the two rotary units 344, 345, and three flanges 348, 349, 350 are laser welded to the end surfaces of two perpendicularly crossing pipes 346, 347 as shown in the drawing. The apparatus for laser welding these parts consists of a laser oscillator 351, a bending mirror 354 adapted to change the path of a laser beam 352 emitted from the laser oscillator 351, and a processing head 353 adapted to apply a laser beam 355, the path of which has been changed, to the surfaces to be welded. An operation of welding the pipes 346, 347 and flanges 348, 349, 350 to each other by using this apparatus will now be described. The path of the laser beam 352 outputted from the laser oscillator 351 is changed by the bending mirror 354, and the resultant laser beam is introduced into the pivotable processing head 353. A condensed laser beam 356 is applied in the perpendicularly downward direction to a groove between the tapering flange 350 and pipe 347 to weld the same. In this case, the pipe 347 is rotated in the direction α by the rotational movements of the rotary units 344, 345, whereby the full-circled welding of the flange 350 and pipe 347 can be done in practice. The welding of the flange 348 and pipe 347 is done by turning the rotary disc 348 in a 180-degree arc, and then applying a laser beam 356 to the flange 348 and pipe 347. If one more laser oscillator is provided, the flange 348, 350 can be welded at once to the pipe 347. In order to weld the flange 349 to the pipe 346, the processing head 353 is turned up in a 90-degree arc to be set in a horizontal position shown by a two-dot chain line, and a laser beam is then applied to the surfaces to be welded. When the rotary disc 343 is rotated by using the rotary unit 342, 342' in this case, the pipe 346 is rotated in the direction β to enable the full-circled welding of the pipe 346 and flange 349 to be done. When the welding apparatus 340 of the second embodiment is used, the laser welding of a flange and a pipe of a branch pipe-carrying tubular pressure container can be done easily. Fig. 15 illustrates other welding method which is used to laser weld a flange and a pipe of a branch pipe-carrying tubular pressure container. The shape of this branch pipe-carrying tubular pressure container 471 is substantially identical with that of the branch pipe-carrying tubular pressure container shown in Fig. 13, and the container 471 has two pipes, i.e. a pipe 465, and a pipe (extending at right angles to the surface of Fig. 15) crossing the pipe 465 perpendicularly, the respective end portions of these pipes being adapted to be subjected to laser welding for joining flanges 462, 463, 464 thereto. An apparatus for laser welding these flanges to the pipes is provided with an oscillator 467, and a rotary processing head 66 adapted to apply a laser beam emitted from the the oscillator 467 to the surfaces to be welded, and this rotary processing head is adapted to be rotated in the direction of an arrow 469. A rotary unit 461 is adapted to rotate the branch pipe-carrying tubular container 471 freely and substantially horizontally. The operation of each apparatus in the laser welding of workpieces will now be described. The laser beam outputted from the laser oscillator 467 passes through the rotary processing head 466 to be applied to the branch pipe-carrying tubular pressure container 471 fixed on the rotary unit 461, and carry out the full-circled welding of the pipe 465 and flange 464. After the completion of the welding of the pipe 465 and flange 464 to each other, the rotary unit 461 is turned in a 90-degree are in the direction of an arrow 470, and the welding of the flange 463 is done. The rotary unit 461 is then further turned a 90-degree arc to carry out the welding of the flange 462. According to the welding method of this embodiment, the laser welding of flanges and pipes of a branch pipe-carrying tubular pressure container can be easily. The laser butt welding of pipe and flange of not less than 500 mm in diameter can be done. Accordingly, the cost of production of a branch pipe-carrying tubular pressure container can be greatly reduced. Fig. 16 shows the structure of a system which exemplified one embodiment of the laser machining system. In this system, the welding of a trunk pipe and a flange along the bus of a gas insulating control apparatus and the boring of the trunk pipe are accomplished by means of a laser beam. A conveyor truck 502 on conveyor rails 501 runs to form a first conveyor line. The aforementioned conveyor truck 502 carries a workpiece or trunk pipe 503 to convey it midway of the first conveyor line in the direction of arrow X 1 . Conveyors 504 are arranged at the two sides of the aforementioned first conveyor line generally at a right angle with respect to said first conveyor line to convey flanges 505 to be welded to the two ends of the trunk pipe 503 in the directions of arrows y 1 and y 2 , thus forming a second conveyor line. Flange assembling apparatus 506 are arranged at the two sides of the conveyor rail 501 so that it may assemble the flanges 505 conveyed on the conveyors 504 to the two ends of the aforementioned trunk pipe 503 by changing the directions of the flanges 505. The trunk pipe 503 thus assembled with the flanges 505 by that flange assembling means 506 is conveyed by the conveyor truck 502 on the conveyor rails 501 in the direction of arrow x 2 to a subsequent step. A positioning device 507 is arranged midway of the conveyor rails 501 to support rotatably the trunk pipe 503 conveyed in the direction x 2 and assembled with the flanges 505 and to correct the axal gap and radial dislocation of the abutting portions of the flanges 505 and the trunk pipe 503. A rotary machining apparatus 508 for welding the flanged trunk pipe 503 supported by the positioning device 507 to the flanges 505 and for boring the trunk pipe 503 by using the laser beam. The rotary machining apparatus 508 has its welding head 508a and boring head 508b arranged rotatably. This rotary machining apparatus 508 is supported by a suspender 509 so that it can be moved in the directions x and y. The welding head 508a and the cutting head 508b can be moved in the (vertical) direction z and are connected to a laser oscillator 511 through a beam guide 510. Incidentally, a control unit 512 controls the whole system. Next, the rotary machining apparatus 508 will be described in detail with reference to Figs. 17 and 18. As shown in the Figures, the rotary machining apparatus 508 is composed of a plurality of welding and cutting heads 8a to 8d which are arranged at a predetermined spacing on the ends of a rotary disc 513 and concentrically with a pivot 514. The rotary disc 513 is rotationally driven by a drive motor 515. This drive motor 515 is fixed on a vertically moving base 516 which is equipped at its one end with a nut engaging with a threaded shaft 518. Thus, the whole apparatus can be moved vertically (in the z direction) by driving a vertically moving motor 519 connected directly to the threaded shaft 518. A dust cover 520 is attached to the vertically moving base 516. This dust cover 520 covers the optical system 521 of an unused machining head, as shown in Fig. 18 to protect the optical system 521 against any dust. The aforementioned optical system 521 is so mounted on the rotary disc 513 as to have its optical axis aligned with that of a laser beam 522 guide by a beam guide when the laser beam 522 has its path changed downward by a bend mirror 523. Next, the positioning device 507 will be described in detail with reference to Figs. 19, 20 and 21. Fig. 21 shows a seam portion at the time of the butt welding of the trunk pipe 503 and the flanges 505. Usually, there arise a widthwise gap g and an external dislocation δ when the trunk pipe 503 and the flanges 505 abut against each other. In case of the laser beam welding, the allowable values are set at g ≦ 0.3 mm and δ = 0.5 mm. The positioning device is used to effect the positioning within the above-specified values. In Figs. 19 and 20, there is mounted on a stationary base 531 a width adjusting motor 532 which has its output shaft connected to a driving threaded shaft 533. This threaded shaft 533 is overlaid by a moving base 535 which is supported on guide rails 534. On one end of the moving base 534, there is mounted a pipe expanding cylinder 537 which is supported by a bracket 536. To the pipe expanding cylinder 537, there is connected a hydraulic motor 537a through a hydraulic electromagnetic valve 537b. Moreover, this pipe expanding cylinder 537 has its cylinder rod 538 connected to a spline shaft 540 through a coupling 539, and these cylinder rod 538 and spline shaft 540 are arranged on a common axis. A pipe rotating motor 542 has its output shaft fixed to a gear 543 meshing with a spline bearing 541 for transmitting the rotation and slide. In front of the aforementioned moving base 535, on the other hand, there is fixed a support base 544 for supporting the pipe expanding spline shaft. A rotary guide 546 is connected to the support base 544 through a bearing 545. To the end of the rotary guide 546, there are connected a pressure plate 546a for contacting with the end face of the flange 505 to be welded to the trunk pipe 503 and a slide guide 547 for supporting a pipe expanding core 548. To the leading end of the aforementioned spline shaft 40, moreover, there is fixed a taper rod 549 which supports the pipe expanding core 548 on its sloped side through a slide guide 554. To the end of the aforementioned stationary base 531, on the other hand, there are fixed a flange receiving roller 552 for receiving the flange 505 and a trunk pipe receiving roller 553 for receiving the trunk pipe 503. Next, the positioning operations of the positioning device thus constructed will be described in the following. First of all, when the pipe expanding cylinder 537 is retracted by operating the hydraulic electromagnetic valve 537b, the taper rod 549 is retracted, and the pipe expanding core 548 is bulged. If the pipe expanding cylinder 537 is advanced, on the other hand, the pipe expanding core 548 is radially constricted from the center axis. If, moreover, the rotary motor 542 is rotated in a direction , the spline shaft 540 is rotated through the gear 543 and the spline bearing 541. Simultaneously with this, the rotation is also transmitted to the taper rod 549. Since the cylinder rod 538 of the pipe expanding cylinder 537 and the spline shaft 540 are connected by the coupling 549 having a built-in bearing, the rotations are blocked here. If, moreover, the width adjusting motor 532 on the stationary base 531 is rotated, the driving threaded shaft 533 is rotated, and the moving base 535 carried on the slide guide 534 is moved in the direction x of the trunk pipe 503 so that the flange contacting plate 546a adjusts the widthwise positions of the flange 505. At this time, the pipe expanding cylinder 537 in the constricted state is inserted from the ends of the trunk pipe 503 and the flange 505 supported by their individual receiving rollers 552 and 553. The pipe expanding cylinder 537 is advanced, and the expanded pipe is temporarily stopped at the instant when the cylinder 537 comes into contact with the inner wall of the trunk pipe. Then, the width adjusting motor 532 is rotated to move the moving base 535 forward to bring the trunk pipe 503 and the flange 505 close to each other. After this, the pipe expanding cylinder 537 is further advanced to effect the pipe expansion, which is stopped and held when the dislocation between the flange 505 and the trunk pipe comes into within the allowable range. Next, the rotating motor 542 is rotated to rotate the trunk pipe 503 and the flange 505 together. After this, the welding is executed by radiating the laser beam from the welding head 508a positioned thereabove. The positioning device will now be described with reference to Fig. 22. A pipe expanding rod 805 and a pipe expanding piece 806, which are used to eliminate dislocation between pipes, are inserted in the interior of pipes 801a, 801b to be welded, and height sensors 802a, 802b are provided above the outer circumferential surfaces of the pipes 801a, 801b. The signal lines of the height sensors 802a, 802b are connected to a comparator 803, a signal line of which is connected to a hydraulic cylinder 804 via a hydraulic unit 807. The data concerning the heights h 2 , h 1 of the pipes 801a, 801b, the workpieces the edges of which are to be aligned are sent to the comparator 803, in which a difference δ between h 1 and h 2 is calculated. The result of the calculation is transmitted to the hydraulic unit 807 to operate the hydraulic cylinder 804. Consequently, the pressure in the hydraulic cylinder increases to cause the tapering rod 805 and pipe expanding piece 806 to be operated, so that the pipes 801a, 801b make alignment actions. During this operation, the height sensors 802a, 802b conduct measurement moment by moment and output signals representative of the results of the measurement to the comparator 803. This operation is carried out until the difference δ becomes zero. When the difference δ becomes zero, the alignment actions are stopped to complete the elimination of the dislocation between the pipes. The measurement of the quantity of a gap between the opposed edges of a pipe and a flange and a gap eliminating mechanism will be described. A gap sensor 813 is set in a position above the outer circumferential surfaces of the opposed edge portions of pipes 801a and 801b, workpieces to be welded together, and a signal line of the gap sensor is connected to a comparator 814 so as to drive a hydraulic cylinder 815 through a hydraulic unit 817. A push head 816 is fixed to the front portion of the hydraulic cylinder 815. The operation of this mechanism will now be described. A gap g between the pipes 801a and 801b, workpieces is measured at the gap sensor 813, and the data on this measurement are transmitted to the comparator 814. The hydraulic cylinder 815 is operated through the hydraulic unit 817 as the gap g is measured, to move the push head 816 in the X-direction, whereby the gas g can be eliminated. According to this embodiment, the alignment of the opposed edges can be carried out automatically when a pipe and a pipe, or a pipe and flange are butt welded together. Therefore, this embodiment produces a large effect when it is applied to a laser welding system. Next, the operations of the laser machining system according to the present embodiment will be described with reference to Fig. 16. The present system is directed to the case, in which the trunk pipe forming the bus and the flange to be used in the gas insulation control system are to be welded or in which the trunk pipe is to be bored for branching. Usually, the bus is used to joint the trunk pipe 503 and the flange 505 machined, and the trunk pipe 503 is then machined to have a bore for branch pipe, as shown in Figs. 23a, 23b and 23c. These machining operations are continuously accomplished with the laser beam by using the present system. First of all, the trunk pipe 503 is carried on and conveyed by the conveyor truck 502 in the direction x 1 until it is positioned and stopped at the center of the flange assembling apparatus 506. At this time, the flange assembling apparatus 506 has its table surface directed upward. The flanges conveyed by the flange conveyors 504 are grasped on the table surface of the flange assembling apparatus and are caused to clamp the trunk pipe 503 and turned at 90 degrees so that they are assembled with the trunk pipe 503. The trunk pipe 503 and the flanges 505 thus assembled are conveyed by the aforementioned conveyor truck 502 to the positions just below the welding head 508a and are positioned at the center portion of the positioning apparatus 507 for the pipe expanding, width adjusting and rotating operations. In this positioning apparatus 507, the pipe expanding head is inserted from the two sides of the flange 505 to effect the expansion and positioning to predetermined sizes. After this, the trunk pipe 503 and the flanges 505 are butt-welded by the laser beam coming from the welding head 508a. After the end of the welding of the two ends of the trunk pipe 503, the laser beam is switched from the welding head to the cutting head 508b to bore the trunk pipe 503. The flanged trunk pipe thus bored is carried again on the conveyor truck 507 and conveyed to the subsequent step. According to the present embodiment, as has been described in various manners, the conveyance, positioning, rotations and expansions of the workpiece can be automated in series when the tubular container composed of the trunk pipe and the flanges is to be manufactured as in the bus of the gas insulation control apparatus. As a result, the production cost can be drastically reduced while using one laser oscillator for the welding and boring operations interchangeably. Thus, it is possible to manufacture a tubular container having little thermal deformation. According to the machining apparatus of the present embodiment, moreover, the plural machining heads are arranged on the circumference concentric with the pivot of the rotary disc, and the base of the rotary drive system is reliably fixed. As a result, it is possible at the time of indexing rotation to align the optical axis of the laser beam reflected by the bend mirror and the optical axis of the optical system of the machining heads so that the laser beam can be prevented from coming out of focus. Since the machining head left unused is protected by the dust cover, the optical system can be protected against the dust to invite no trouble at the time of beam condensation. According to the positioning device of the present embodiment, still moreover, all the pipe expanding cores for expanding the trunk pipe from the inside are uniformly moved in the radial directions by the transverse movement of the taper rod so that the deformed pipe can be corrected to have a true circle. Furthermore, the transverse drive source of the taper rod can retain the size of the expanded pipe as it is, if a pilot check valve is disposed in the hydraulic cylinder and its oil pressure circuit. Then, the size is not changed in the welding operation. If a relief valve in the oil pressure circuit is used, any hydraulic motor is not damaged, even if it is used as the width adjusting drive source and pressurized even with the grooves of the tubes being contacting with each other. Next, another embodiment of the machining heads to be used in the present system will be described with reference to Figs. 24, 25 and 26. In the present embodiment, as shown, a base for supporting the machining head is equipped on its lower face with the nozzle 652 having a variable aperture for spraying the shield gas and the guide 653 for adjusting the diameter of the nozzle 652. The condenser lens 654 is disposed in the aforementioned aperture-variable nozzle 652, and the aforementioned guide 653 is connected to an air cylinder 655 for moving said guide 653 vertically. On other hand, a nozzle body 656 above the aforementioned nozzle 652 is formed with a shield gas introduction port 657 which has its leading end piped with a three-way electromagnetic valve 658 for interchanging the gases. Next, the operations will be described in the following. The laser beam 622 coming from the laser oscillator is deflected by the bend mirror 623 into the condenser lens 654 of the machining head. The aperture-variable nozzle 652 has its tip divided, as shown in Fig. 24. At the lowermost position of the air cylinder 655, the guide 653 also takes its lowermost position so that the maximum opening d o is obtained by the spring action of the aforementioned nozzle 652. When the air cylinder 655 is moved to the uppermost position, on the other hand, the guide 653 constricts the opening of the nozzle 652 to the minimum opening d s , as shown in Fig. 26. In the maximum opening state, moreover O 2 gases, for example, can be introduced into the nozzle 652 by opening one of the inputs of the three-way electromagnetic valve 658. In the minimum opening state, on the contrary, Ar gases can be introduced by opening another input of the three-way electromagnetic valve 658. As has been described hereinbefore, by changing the nozzle diameter of the machining head in accordance with the application (for the welding or cutting operation) and by interchanging the kinds of the gases to be sprayed, the cutting and welding operations with the laser can be accomplished with one head. By the introduction into the laser machining system, moreover, a laser composite machining system can be realized. Next, still another embodiment of the laser machining system will be described in the following. To the most buses in the gas insulation control apparatus, there are connected not only the aforementioned flanges but also the branch pipes. Then, the system corresponds to the case in which the cutting and flange-welding of the end faces of the branched pipe are accomplished by the use of the laser beam. First of all, the machining process will be schematically described with reference to Figs. 27a to 27d. The trunk pipe 603 having a branch pipe 603a welded thereto in advance (as shown in Fig. 27a) has its pipe end face cut with the laser beam, as shown in Fig. 27b. After this, flanges 605, 605' and 605a are assembled to the ends of the trunk pipe 603 and the branch pipe 603a, as shown in Fig. 27c. After this, the individual flanges 605, 605' and 605a are welded to the individual pipes 603 and 603a by the use of the laser beam, as shown in Fig. 12d. Next, the system for the operations described above will be described in the following with reference to Fig. 28. The trunk pipe 603 having the branch pipe 603a arc-welded in advance thereto is conveyed by the conveyor truck 602 on the conveyor rails 601 to a cutting station A ○. This cutting station A ○ is generally constructed of a turntable 660 which can be moved in the y direction and rotated in a direction of α while carrying the branched trunk pipe 603, and a swivel table 662 which is connected to the laser oscillator 611 through a beam guide 610a and can be rotated in a direction  while carrying a cutting head 661. Then, the turntable 660 is turned to bring the end of the trunk pipe 603 or the branch pipe 603a to the cutting position, in which the swivel table 662 is rotated while radiating the laser beam from the cutting head 661 to cut the pipe end. When the two ends of the trunk pipe 603 and the end of the branch pipe 603a are cut away, the workpieces are conveyed to a flange assembling station B ○ at a next step. This flange assembling station B ○ has a structure substantially similar to that of the flange assembling apparatus which has been described with reference to Fig. 16, and its repeated description will be omitted here. The trunk pipe 603 having its two ends and its branch pipe 603a assembled with the flanges 605 at the flange assembling station B ○ is conveyed to a welding station C ○ for a subsequent step. If, in this case, the trunk pipe 603 and the branch pipe 603a have an equal diameter, they can be individually assembled with the flanges 605 on the two conveyors. If the branch pipe 603a has a diameter smaller than that of the trunk pipe 603, these two pipes can be assembled with the individual flanges by causing one conveyor to carry the flanges having a diameter matching the diameter of the trunk pipe 603 and the other conveyor to carry a flange having a diameter matching the diameter of the branch pipe 603a. The welding station C ○ has a structure substantially similar to that of the cutting station A ○, excepting that it is equipped with a welding head 663 on the swivel table 662 in place of the cutting head. Moreover, the trunk pipe 603 or the branch pipe and the flanges 605 and 605a are welded while being irradiated with the laser beam of the laser oscillator 11 from the welding head 663 by rotating the swivel table 662. According to the present embodiment, as has been described hereinbefore, the machining can be accomplished at the unit of each member so that the flanges can be welded without any consideration into the thermal deformation which might otherwise be caused in the mark welding. Moreover, a machining operation using a large machine after the laser welding is not required to reduce the production cost drastically. Still moreover, the composite machining system using the laser can be produced. Incidentally, in the foregoing embodiments, the laser oscillator is disposed for each of the cutting station and the welding station but may be shared commonly between the two stations.

Claims: A welded metal container comprising: a trunk metal pipe (2), a branch pipe (3) having an end portion arc welded to the outer peripheral wall of said trunk pipe (2), and flanges (4a, 4b, 4c) connected to the end portions of said trunk and branch pipes (2, 3) by laser-beam welding carried out after said arc-welding. A method of manufacturing a welded metal container comprising: welding an end portion of a branch pipe (3) to the outer peripheral wall of a trunk metal pipe (2) by arc welding so that said branch pipe (3) extends radially from said trunk pipe (2), and welding a flange (4a, 4b, 4c) to each end portion of said trunk and branch pipes (2, 3) by laser beam welding after said arc-welding. The method of claim 2, wherein the end surfaces of said trunk and branch pipes (2, 3) are cut by mechanical or laser cutting after said branch pipe (3) has been arc welded to said trunk pipe (2) and before said flanges (4a, 4b, 4c), which have been mechanically processed, are laser-beam welded to said end portions.

Inventors: FUKUDA SHINJI, GOTO KOJI, HASHIURA MASAYOSHI, ISSHIKI OSAMU, KIKUCHI HIDEAKI, KOBAYASHI YUTAKA, MATSUSHIMA OSAMU, MURASHITA MASAKI, NAKAGAWA SADAO, NAKANO SEIZO, OTA KATSURO, SATO TAKASHI, SATOH TAKASHI, FUKUDA, SHINJI, GOTO, KOJI, HASHIURA, MASAYOSHI, ISSHIKI, OSAMU, KIKUCHI, HIDEAKI, KOBAYASHI, YUTAKA, MATSUSHIMA, OSAMU, MURASHITA, MASAKI, NAKAGAWA, SADAO, NAKANO, SEIZO, OTA, KATSURO, SATO, TAKASHI, SATOH, TAKASHI
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1991
Main classification: B23K26
IPC codes: B23K26, B23K37