GB2042394A - A welding machine for welding tapered structures - Google Patents

Abstract

A welding machine for welding a tapered tube 9 formed by shaping a metal sheet comprises a clamping bearing 6 through which the tube is continuously fed for welding at an adjacent welding position 47 submerged arc. A guide 45 rigidly secured to a frame 75 of the machine engages the longitudinal gap in the tube to align the tube. The clamping bearing comprises circumferentially distributed thrust elements 26, 28 carrying pressing rolls 21, 22 for acting on the tube. One thrust element 26 is fixedly mounted on the frame 25 and the other thrust elements 28 are radially movable relative to the tube, the movable elements being actuated by a cam 33 rotatable by linear actuators. <IMAGE>

Description

SPECIFICATION A welding machine for welding tapered structures This invention relates to a welding machine for welding tapered tubular structures and concerns a stationary welding machine for welding tapered structures which are of substantial length and which are initially produced in the form of gapped or divided tubes prepared from preshaped metal sheet or plate.

Tapered tubular structures of this kind are produced by rolling or pressing the metal sheet or plate to form a tube having a longitudinal slot or gap and then closing the gap by means of a continuous weld. Since the shape of the gap may vary considerably, more particularly in the case of vary long structures, constant adjustment of the alignment of the tube is required during welding. The distance between the gapped tube and the welding station must remain contant and the tube must move through the welding machine at a constant speed throughout the welding process. The means for clamping and guiding the gapped tube are therefore very important.

German Auslegesschrift 1 912 394 discloses a device for clamping and guiding a tapered tube during welding. The device has a number of clamping units, the number depending upon tube length, so disposed on a track as to be movable relative to the welding machine. The clamping units enable the tube to be rotated about its longitudinal axis to a limited extent by means of spaced-apart jaw pairs, so that the gap can take up a predetermined position relative to the welding station; two oppositely disposed pairs of clamping jaws act alternately as retaining means and as torsion means to align the welding gap. A large number of pairs of clamping jaws provide reliable guidance and alignment of the gapped tube throughout the welding process.

A different approach to the problem is disclosed in United States patent specification 3 329 329, in which the entire tube is subjected to torsion free rotation within the welding machine, by means of a guide which engages the tube gap. The guide engages behind the gap edges so that the width of the gap yields to the lateral pressure of guide rolls and the gap is aligned correspondingly. The gapped tube is guided laterally by lateral guide rolls which adapt to the continuously varying diameter of the tube and which can be actuated by linear actuators.

However the complicated construction of the combined guiding and clamping means of the apparatuses described above means that they operate reliably only in association with a relatively uniform gap and mis-welds are therefore unavoidable if the gap to be welded together is irregular. The guide which engages behind the gap is mainly responsible for ensuring that the gap is in the necessary uniform position relative to the welding station.

Consequently, the guide must always be pressed sufficiently tightly on to the gap.

Unfortunately, this requires heavy outlay on machinery and control facilities. Also, if the sides of the gap are not parallel tilting of the tube or similar problems which the guide cannot compensate for may occur, with the result that the gap edges cannot be guaranteed to extend dead straight and plane-parallel. Another problem is that the large driving discs and their associated shaping plates must be interchanged when it is required to deal with tubes of different dimensions.

According to the present invention, there is provided a welding machine for welding a tapered structure in the form of a longitudinally divided tube, comprising a clamping bearing through which the tube is fed during welding and a guide for engaging the longitudinal gap in the tube to align the tube, in which machine the guide is rigidly secured to a frame of the machine and the clamping bearing comprises circumferentially distributed thrust elements each carrying pressing roll means for acting radially on the surface of the tube to be welded, one of the thrust elements being fixedly mounted relative to the frame and the other thrust elements being radially movable relative to the frame.

Rigidly securing the guide to the frame ensures that the gapped tube to be welded is always in constant alignment relative to the welding machine. The tube edges to be welded together thus always come into the same welding position irrespective of the shape of the gap in the tube. The movable thrust element and the fixedly mounted thrust element, which is preferably disposed in the plane of the welding gap, ensure that the interval between the gapped tube and the stationary welding station remains constant.

The movable thrust elements press their pressing roll means against the pressing roll means of the fixed thrust element so that the welding gap is always in the required position relative to the welding station. Tapered structures of substantial length can therefore be provided with a welding seam of constant quality irrespective of variations in the dimension of the gapped tubes.

Advantageously, the guide has a tongue or blade or similar device which extends through the tube gap into the tube interior. The tongue is rigidly connected to the frame and ensures accurate radial positioning of the welding gap. Since the guide serves merely to align the gapped tube and not to maintain the edges of the gap at a predetermined distance from one another, the guide can be simple and rugged construction.

The use of an appropriate welding support may prevent damage to the tube inside wall being caused by welding scraps and like frag ments during welding. Conveniently, the portion of the tongue extending into the tube interior extends to a position downstream of the welding station and is in the form of a welding saddle. This feature makes it unnecessary to provide a separate mounting for the welding saddle and unnecessary to provide a separate guide. Combining the tongue with the welding saddle is a means of ensuring correct location of the welding saddle in relation to the welding gap and to the welding station.Thus the guide may, if required, provide a welding factor of To ensure uniform adjustment of the whole clamping bearing and to maintain the constant height of the gap edges to be welded together, the thrust elements preferably have backup rolls bearing on a cam which is subdivided into segments, the cam being rotatable and movable horizontally and vertically to a limited extent by linear actuators. Desirably, the fixedly mounted thrust element carries a backup roll so that the clamping bearing shifts centrally and vertically when the cam rotates; consequently, the pressing roll means always provide a uniform preselectable pressure irrespective of tube diameter and, in co-operation with the pressing roll means of the fixedly mounted thrust element, ensure that the weld gap advances horizontally.The cam can be turned radially by means of the linear actuators so that the correspondingly preselectable pressure is applied in directed fashion via the thrust element to the pressing rolls and thus to the tube wall.

The pressure operative on the vertically acting linear actuators may be used to control the adjustable pressure. Also, in a preferred embodiment of the present invention control values including the diameter, wall thickness and conicity if the blank to be welded, are set by means of a sensing roller and act by means of pressure controlling means to control the operative pressure of the linear actuators.

According to another preferred feature of the invention, the cam segments have curvilinear sawtoothed inner surfaces corresponding to the conical shape of the gapped tube to be welded. Desirably linear actuators rotate the cam uniformly to the extent allowed by the reducing diameter of the gapped tube or of the pressing rolls bearing on its outer surface.

This simple feature produces an even pressure over the particular type of blank concerned, such pressure being applied by all the pressing rolls in the same order of magnitude.

The cam may, for example, be rotatably mounted in a casing adjustable along vertical guides, further improving uniformity of movements. To improve this feature still further, slideways for the movable thrust elements may be disposed in the casing.

In a preferred embodiment of the present invention the linear actuators are pressurized differently to rotate the cam, that is, while the piston rod of one actuator moves in the piston rod of the other moves out. Damage of the actuators may be reliably prevented if, the linear actuators are, for example, mounted for pivoting and connected to the lugs on the cam.

Conveniently a portion of the fixedly mounted thrust element disposed adjacent the segments is bent into an S-shape to form a bearing for the backup roll. The fixedly mounted thrust element can then be devised as far as the bent part in exactly the same way as the movable thrust elements.

To ensure a uniformly smooth infeeding of the gapped tube and a uniformly smooth welding rate it is desirable that the gapped tube be infed into the welding station by an infeed carriage and be moved past the welding station by a pulling carriage. Preferably, each such carriage has its own drive, the drives being operated synchronously with one another. The infeed carriage can be operated by a pull cable or cable winch while the pulling carriage may have a geared drive providing very uniform movement.

In a preferred embodiment of the present invention the infeed carriage moves the gapped tube as far as the welding station whereas the pulling carriage moves the gapped tube past the welding station. Therefore, to provide a convenient connection between the pulling carriage and the gapped tube, vertically adjustable grippers are associated with the pulling carriage. The grippers can engage the tube wall either in the top part or in the bottom part.

The entire gapped tube need not therefore be rotated when it is required to align the position of the gap; indeed, it is a great aid to rectilinearity of the gap if only the portion of the tube which has just been welded is rotaxed. Since the tube is located at the justwelded end by the grippers of the pulling carriage, the other end of the tube should be movingly mounted. Therefore, the infeed carriage preferably has a trough-shaped tubesupporting surface and a vertical abutment.

The infeed carriage can therefore be lightweight and small, whereas the pulling carriage has corresponding dimensions and is heavy enough to receive any forces occurring.

In the case of structures of substantial length twisting may occur within the part already welded. To compensate for this effect, the tube-pulling grippers may, for example be mounted for radial rotation in the pulling carriage.

In order that the invention be readily understood an embodiment thereof will now be described, by way of example, with reference to the acompanying drawings, wherein: Figure 1 illustrates diagrammatically, partly in side elevation and partly in vertical longitudinal cross-section, a machine for welding structures of substantial length; Figure 2 is an end view of the clamping bearing of the welding machine with the cover plate removed; and Figure 3 is a vertical longitudinal crosssection through the clamping bearing.

Referring now to the drawings, Fig. 1 shows a continuous welding machine 1 comprising a powder feed 3 rigidly disposed on a platform 2, a powder extractor 4, a welding wire 5, a stationary clamping bearing 6 and, movable relative to the latter, an infeed carriage 7 and a pulling carriage 8.

A conical gapped or divided tube 9 is placed, prior to welding, on a carriage 7 and a support roll 10. By means of a winch 11 and cable 12 the carriage 7 is then advanced towards the welding machine 1. The narrower end of tube 9 is received in a trough-like support surface 13 of carriage 7 and bears against an abutment-like carriage rear wall 14.

After the welding position has been reached, the pulling carriage 8 is connected to the iarger-diameter tube end by means of grippers 15. By means of an adjusting wheel 16 the grippers 15 can be adjusted so as to engage, as a rule, with the bottom edge of tube 9. Any torsion arising because of necessary or automatic corrections of the welding gap affects the grippers 15 and consequently, the grippers are mounted in a radially mobile rotating bearing (not shown in detail), so that any torsional stresses occurring can be compensated for satisfactorily. As a means of ensuring a uniform drive, gearing 17 associated with the carriage 8 co-operates with a toothed rack 18. Carriage 8 moves in a horizontal plane on a way 19. The drives 17, 11 operate in synchronism with one another to ensure a uniform advance of the tube 9.

Further details of the bearing 6 of machine 1 are shown in Figs. 2 and 3; the cover plate 20 visible in Fig. 3 is not shown in Fig. 2.

The tube 9 is introduced substantially centrally into the bearing 6 with guidance by pressing rolls 21, 22. In Fig. 2 there can be seen the front end 23 of tube 9 and its rear end 24. As will be apparent from Fig. 2, the conical tube 9 is guided horizontally below the top pressing roll 21 of a thrust element 26 which is rigidly mounted in a frame 25 of the bearing 6, the tube 9 being guided near the welding seam 27. Thus, the element 26 is secured to the frame, but other thrust elements 28, which are in the form of slides and which extend radially in relation to the tube 9 are mounted for radial movement in guides or slideways 29 of a casing 30. The elements 28 also bear by means of backup rolls 31 on a cam 33 subdivided into segments 32.The segments are of sawtooth shape and have curvilinear inner surfaces 34 whose curvature corresponds to the conicity of the tube 9.

Cam 33 is mounted for rotation in a bearing casing 30 which is in turn mounted in vertical guides 35.

The thrust element 26 associated with the top pressing roll 21 also has a backup roll 36 which, as can be seen in Fig. 3, is mounted in the thrust element 26 which is of S-shape form. The roll 36 ensures that when the cam 33 turns the entire clamping system is shifted vertically. The cam 33 is rotated by the actuation from alternate sides of linear actuators 37 by way of connections 38, 39, 40 and 41.

The linear actuators 37 have piston rods 42 connected to lugs 43 formed on cam 33, and are securely connected by cylinders 44 to the frame 25.

During welding the actuators 37 operate so that the piston rod 42 of one actuator 37 moves in while the piston rod 42 of the other actuator 37 moves out causing the cam 33 to be rotated clockwise. The pressing rolls 21, 22 are therefore pressed with the necessary preselected force against the wall of the tube 9 as its diameter decreases continuously.

The force with which the tube edges to be welded together are pressed against one another can be varied within limits, variation being provided by means of the vertically acting actuators 37. A staight edge template (not shown) is devised in accordance with the diameter, the wall thickness and the conicity of the blank to be welded. The values found from the straight edge by means of a sensing roll and supplied to a pressure controller are used to control the operative pressure of the actuators 37.

Since the backup roll 36 is non-displaceably secured to the fixedly mounted thrust element 26, the clamping system also alters its vertical position so that the slides 28 follow up accordingly. Upon completion of a welding operation the actuators 37 are reversed and returned to their original positions so that the cam 33 and therefore the slides 38 return to their initial positions.

The components described above are fixed in relation to the welding machine 1. A guide 45 (Fig. 3) is secured to frame 25 and engages the gap to be welded by way of a tongue or blade or the like 45. The tube 9 is therefore so aligned that the gap is always fed into the welding station 47 in the same position relative to the station 47. Since tube end 23 is secured by grippers 15 of carriage 8, the welding seam 27 always runs dead straight despite the presence of torsion forces in the just-welded material. To compensate for the possibility of such torsion forces occurring, the grippers 15 are mounted in the carriage 8 for radial movement. This feature is not shown.

The guide 45 which extends into the tube interior 48 includes a welding saddle 49. The saddle 49 is always correctly positioned exactly below the seam 27 and forms a welding support to help prevent damage being caused to the tube interior by welding scraps and like fragments dropping into the tube. Also, irrespective of the coinicity of the advancing blank, the stationary and vertically located welding station 47 with the saddle 49 can guide a welding bath to such an extent that the welding factor I can, if required, be achieved.

In the preceding description it has been assumed for the sake of simplicity that the grippers 15 engage the gapped tube at its large-diameter end, the blank welded in the welding machine in this position. The apparatus may of course be constructed so that the narrower-diameter end of the gapped tube is engaged by the grippers and the means for retaining and advancing the tube devised in accordance with the position of the tube to be welded.

Claims (17)

1. A welding machine for welding a tapered structure in the form of a longitudinally divided tube, comprising a clamping bearing through which the tube is fed during welding and a guide for engaging the longitudinal gap in the tube to align the tube, in which machine the guide is rigidly secured to a frame of the machine and the clamping bearing comprises circumferentially distributed thrust elements each carrying pressing roll means for acting radially on the surface of the tube to be welded, one of the thrust elements being fixedly mounted relative to the frame and the other thrust elements being radially movable relative to the frame.

2. A machine according to claim 1, wherein the guide has a tongue which in use extends through the tube gap into the tube interior.

3. A machine according to claim 2, wherein the portion of the tongue extending into the tube interior extends to a position downstream of a welding station of the machine and is in the form of a welding saddle.

4. A machine according to any one of claims 1 to 3, wherein the thrust elements have backup rolls bearing on a cam which is subdivided into segments, the cam being rotatable and movable vertically and horizontally to a limited extent by linear actuators.

5. A machine according to claim 4, wherein the segments have curvilinear sawtoothed inner surfaces which substantially correspond to the conical shape of the divided tube to be welded.

6. A machine according to claim 4 or 5 wherein the cam is rotatably mounted in a casing which is mounted in vertical guides.

7. A machine according to claim 6, wherein slideways for the movable thrust elements are disposed in the casing.

8. A machine according to any one of claims 4 to 7, wherein the linear actuators are mounted for pivoting and are connected to lugs on the cam.

9. A machine according to any one of claims 4 to 8, wherein a pressure operating on vertically acting ones of the linear actuators is used to control an adjustable pressure with which the pressing rolls act on the gapped tube during use.

10. A machine according to claim 9, wherein the pressure is controlled in dependence on control values, which include the diameter, wall thickness and conicity of the tubular structure to be welded and are set by means of a sensing roller and a control template.

11. A machine according to any one of claims 4 to 10, wherein a portion of the fixedly mounted thrust element disposed adjacent the segments is bent into an S-shape to form a bearing for the backup roll.

12. A machine according to any preceding claim, including an infeed carriage which is movable past a welding station of the machine by a pulling carriage and wherein each carriage has its own drive, the drives being operated synchronously with one another.

13. A machine according to claim 12, wherein vertically adjustable grippers are associated with the pulling carriage.

14. A machine according to claim 13, wherein the grippers are mounted in the pulling carriage for radial rotation.

15. A machine according to claim 12, 13 or 14 wherein the infeed carriage has a trough-shaped tube-supporting surface and a vertical abutment.

16. A welding machine substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

17. Any novel feature or combination of features herein disclosed.