Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K37/00—Auxiliary devices or processes, not specially adapted to a procedure covered by only one of the preceding main groups
  • B23K37/04—Auxiliary devices or processes, not specially adapted to a procedure covered by only one of the preceding main groups for holding or positioning work

Definitions

• the present invention relates to a welding device as defined in the preamble of claim 1.
• the invention relates to the welding of metal sheets of mainly non-magnetic material, but it can also be used for other types of joining of different materials. It is only essential to the material to be welded that it is mainly non-magnetic. In other words, the material to be welded must not significantly disturb the magnetic field acting through it. This means that the proportion of magnetic material may be at most a few tens percent .
• the invention has been developed especially for the welding of products, such as containers, manu- factured from austenitic stainless steel, aluminium or titan.
• Longitudinal and circumferential welds on the products must almost always be shielded from the root side by a separate shielding gas flow when the plasma arc or TIG welding method is used.
• the shielding pre- vents oxidation of the root in the molten state and deterioration of its corrosion resistance.
• shielding the root is difficult because the root gas shoe must be supported inside the container and the rotary motion of the contai- ner must be taken into account in the shielding arrangements .
• root shielding is nowadays implemented by having an assistant welder support the gas shoe manually inside the container during the wel- ding operation.
• Corresponding problems and a need for an assistant are also experienced in many other corresponding cases when large plate-like objects are being welded.
• One of the applications of the invention is backing of the weld root.
• Single-side welding is a significant method that can be used to improve produc- tivity. Generally, this requires root backing to ensure a sufficient weld quality. Moreover, the use of backings reduces the precision requirements regarding groove preparation and allows welding with a larger current. The tasks of mounting and dismounting the backings currently used, such as copper rings or ceramic bars, increase the manufacturing costs of the product .
• bosses With current methods, the use of bosses is difficult. Especially in small containers, the conditions are disagreeable due to the smoke and heat produced during welding, and ventilation cannot be easily arranged. Nevertheless, the boss should be supported and moved accurately along the groove. In addition, a welding assistant is generally always needed, which significantly increases the costs.
• a specific object of the invention is to present a new type of welding device by means of which a welding boss can be held as accurately as possible in the right position on the opposite side of the weld during the progress of the welding in a simple and easy manner without an assistant, and which obviates the time-consuming mounting and dismounting operations.
• the welding device of the invention comprises a supporting frame mounted in conjunction with the welding burner and movable along the surface of the material to be welded.
• the supporting frame may be at- tached directly to the welding burner or suitably connected to it or mounted on it in a suitable position so that the supporting frame will move along the sur- face of the material being welded as the welding burner is being moved along the groove.
• the welding device comprises a counter frame which is placed on the opposite side of the supporting frame against the material to be welded and which is provided with a welding boss covering the groove area being welded.
• the supporting frame and the counter frame are provided with at least one pair of magnets, preferably permanent magnets, which keeps the supporting frame and counter frame aligned with each other when the supporting frame is being moved on as the welding work progresses.
• the supporting frame and the counter frame are also provided with bearings that support the supporting frame and counter frame on the material to be welded.
• the perpendicular distance of the bearings from the weld/groove is larger than the perpendicular distance of the magnets from the weld/groove, so that the magnets will press the wel- ding boss towards the material to be welded.
• both the supporting frame and counter frame are light enough, even one pair of magnets of sufficient strength will suffice to keep them aligned with each other, but a better and more reliable grip is achieved if both the supporting frame and the counter frame are provided with at least two pairs of permanent magnets placed on opposite sides relative to each other and at a suitable distance from each other.
• the boss used in the welding device of the invention may be a plate-like backing.
• the backing material may be e.g. copper and the backing may have a channel that runs parallel to the groove to be welded and determines the size of the weld root.
• the boss is a shiel- ding gas shoe consisting of a suitable space filled with shielding gas and open on one side, being held against the welding spot and moved along the groove. It is also possible to use a backing inside the shielding gas shoe.
• the supporting frame and the counter frame are provided with suitable bearings that support them on the surface of the material to be welded and allow them to move along the surface.
• the bearings may consist of various rollers, balls, wheels or equivalent elements, but also of a relatively lubricous solid surface in certain applications.
• the best bearing system consists of relatively large, individual balls that have no directional effect restricting the motion of the welding device. They also form good knuckle points about which the counter frame can be turned against the weld/groove by the magnets.
• the bearings are preferably so disposed that they maintain a clearance between the material to be welded and the magnets attached to the supporting fra- me and counter frame while still keeping the magnets as close as possible to the material surfaces, e.g. at a distance of about 1 mm. In this way, the attractive force of the permanent magnets can be maximised without subjecting them to mechanical strain or wear.
• the welding device of the invention has significant advantages as compared with prior art. The welding device allows shielding or other treatment of the weld from the opposite side without assistants, without difficult and unpleasant working conditions and without time-consuming mounting work.
• the entire groove can be welded without having to perform any actions on the opposite side while the counter frame, magnetically adhering to the supporting frame, is accurately following the groove and the progress of the welding operation.
• the supporting frame is car- ried by the welding burner and the counter frame accurately follows the supporting frame, the weld root can be effectively shielded and supported.
• a shielding gas shoe of a very small structure can be used, thus significantly reducing the amount of shielding gas needed.
• the welding device can be easily moved from one groove to another within the object under construction by simply moving the suppor- ting frame along the surface of the object while the counter frame is following on the opposite side. This brings a significant additional saving in time in the case of large objects comprising several different grooves to be welded.
• Fig. 1 presents a side view of a supporting frame according to the invention
• Fig. 2 presents the supporting frame of Fig.
• Fig. 3 presents a counter frame according to the invention in side view
• Fig. 4 presents the counter frame of Fig. 3 as seen from above,
• Fig. 5 presents an additional application for the counter frame in Fig. 4, and
• Fig. 6 presents an alternative structure for the counter frame in Fig. 4.
• Figures 1 and 2 illustrate a supporting frame
• the supporting frame consists of a rigid central frame 15 and end frames 17 connected to it by parallel joints 16.
• the end frames can be turned in relation to the central frame so as to give the supporting frame as a whole a desired curvature, i.e. a curvature substantially corresponding to the surface to be welded.
• Each one of the end frames comprises a bearing element 13, i.e. a ball, which is free to rotate in any direction.
• each end frame 17 is provided with a permanent magnet 4, 5, which protrudes from the end frame 17 by a distance smaller than the distance of protrusion of the bearing element 13, so that when the bearing elements 13 rest on a straight or curved surface, depending on the shape of the supporting frame as a whole, a small air gap is left bet- ween the surface and the magnets 4 and 5.
• the central frame 15 is connected to a supporting arm 19, via which the supporting frame is attached to the welding burner or to a suitable element moving in conjunction with the welding burner, so that the supporting frame and the welding burner always move and advance simultaneously in the direction of the groove .
• Figures 3 and 4 illustrate a counterpart of the supporting frame of the welding device, i.e. a counter frame 2.
• the counter frame consists of a rigid central frame 20 and end frames 22 connected to it via parallel joints 21.
• Each end frame 22 is provided with a ball acting as a bearing element 14 as well as a permanent magnet 6, 7.
• the dimensions of the counter frame correspond to the supporting frame so that, when placed opposite to each other on opposite sides of the material to be treated, permanent magnets 4 and 7 form a pair of magnets precisely aligned with each other while permanent magnets 5 and 6 form another pair of magnets precisely aligned with each other.
• a shielding gas shoe 12 acting as a boss 3.
• the joint used is preferably a universal joint, which keeps the shielding gas shoe correctly oriented while allowing it to turn both in the longitudinal and in the transverse direction of the groove.
• the shielding gas shoe consists of a chamber that is open on the side facing the groove to be welded and is provided with a sealing 24 covering its entire underedge .
• a pipe 25 Connected from outside to the chamber is a pipe 25 used to supply shielding gas into a shielding gas distribution pipe 26 circling inside the chamber and provided with holes allowing the shielding gas to be uniformly discharged into the shielding gas chamber.
• the reference numbers used in the second embodiment presented in Fig. 5 correspond to the embodiment in Fig. 4, but in the embodiment in Fig. 5 the shielding gas shoe 12 is additionally provided with a backing 8 placed inside the chamber.
• the backing consists of a plate-like body with a channel 10 in its surface facing the weld, said channel being of a curved shape in cross-section and running in the direction of the weld.
• the underside of the weld is shaped and moulded against the channel as the backing is sliding along the weld.
• Fig. 6 shows a third embodiment of the counter frame, which only has a backing 9 attached to the central frame 20 via a shaft 23 and provided with a channel 11 running in the direction of the weld and supporting and shaping the root of the weld.
• the bearing elements 14 and permanent magnets 6 and 7 are so disposed that the line 27 passing via the centres of the bearing elements 14 is farther removed from the boss 3 than the line 28 passing via the centres of the permanent magnets 6 and 7.
• the attractive force of the permanent magnets will press the boss 3 against the weld.
• the shielding gas shoe is held with a sufficient tightness around the weld by the force of attraction of the permanent magnets alone and the backing is pressed against the weld with a pressure required for sufficient shaping of the weld.
• the supporting frame and the counter frame are preferably made of light non-magnetic material, such as aluminium.
• the frames are provided with oppositely disposed pairs of permanent magnets, which position the frames very accurately relative to each other.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Butt Welding And Welding Of Specific Article (AREA)

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• 1997
  • 1997-05-26 FI FI972224A patent/FI972224A/fi unknown
• 1998
  • 1998-05-25 AU AU75320/98A patent/AU7532098A/en not_active Abandoned
  • 1998-05-25 WO PCT/FI1998/000435 patent/WO1998056536A1/fi not_active Application Discontinuation
  • 1998-05-25 EP EP98922821A patent/EP1015170A1/en not_active Withdrawn

Non-Patent Citations (1)

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