JPS6338275B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises at least one electrode device arranged for rolling movement over the weldment, said device not contacting the weldment, connected to a current supply device. It is configured as a pressing member made of a material with good electrical and thermal conductivity, such as copper, and an endlessly rotating element, which is configured to roll into contact with the workpiece and can be movably pressed against the workpiece. The present invention relates to an electric resistance roller seam welding device having a contact member.

In particular, it is known that resistance welding of iron plates with certain materials, especially metal coatings such as tin, zinc, lead, etc., is encountered with considerable difficulties in industrial applications. The reason for this is that the commonly used copper-based electrodes form alloys with the coating material of the weldment under the influence of welding temperatures and pressure forces and are thereby contaminated. This alloy formation, which varies depending on the welding conditions and is not or only slightly controllable during the course of the process, changes the material properties of the electrode material, which influence the welding parameters, in particular the passage of current and heat, and thereby A uniform weld seam structure is no longer guaranteed, since the weld structure formation is then impaired. The mechanical properties of the electrode, such as hardness, heat resistance, geometry, etc., can also be changed by the process, which likewise impairs the welding temperature and electrode service life.

Swiss Patent No. 370175 discloses that the contact element of the electrode is constructed as a wire, in particular made of copper;
Since the wire is wound around a pressure roller and driven, the welding site is supplied with new, uncontaminated wire, and wire contaminated by the welding process is carried away, thereby reducing Devices of the type mentioned at the outset are known which avoid the above-mentioned difficulties. According to one embodiment of this known device, the wire is guided as an endless ring through a pressure roller and a deflection roller and, after leaving the welding point, passes through a cleaning device, so that the wire passes through a cleaning device several times. can be used. However, in practice this comes with drawbacks. Copper wire undergoes significant cross-sectional changes due to welding pressure and temperature, and it is only after significant material removal from the wire cross-section that surface contamination caused by alloying can be adequately removed from the wire. It is possible. The influence of these cross-sectional changes allows only a slight rotation of the endless wire ring, in which case the welding temperature also changes depending on the cross-sectional change. With such devices only an approximately sufficient service life can be achieved.

In practice, therefore, only other variants of the known device have been implemented in which the copper wire is unwound from a storage roll, wound up on a take-up roll after passing through the welding point, and then removed from the device, for example melted. According to German Patent No. 1565803, it is also possible to pass the wire twice above and below the welding point. This method was widely used at that time, especially in the canning industry, for roller welding of very thin steel sheets to be metallized. However, the disadvantage in this case is that the copper wire is a consumable metal that must be continually supplied fresh and is consumed after one or two passes. When welding large quantities of workpieces continuously, it is necessary to constantly replenish the welding equipment with wire storage rolls and to remove the take-up reel with spent copper wire. Each roll change means a work stoppage, so the known process is ultimately a discontinuous process. Since the wire receives at least 1% by weight of the coating metal, for example tin, during the welding process, an extremely large amount of copper wire must be supplied. Another drawback is that the relatively soft copper wire is deformed by the welding pressure so that during the second pass it no longer has the same cross-section as during the first pass, and is and that complex and expensive mechanisms are required to compensate for the wire elongation that occurs during winding, welding and, if necessary, for cross-sectional processing of the copper wire.

When spot welding metal-coated iron plates, the main part consisting of copper and no or only a small amount of tungsten or similar covering material of the weldment, which is mechanically strongly bonded to it and in contact with the weldment, are used. Composite electrodes consisting of liners or contact elements made of non-alloyable metallic or alloyed materials are known (see, for example, DE 191 442 A1). Although this can in fact significantly reduce electrode contamination due to alloying, due to the different coefficients of thermal expansion of the electrode materials, significant thermal stresses can occur within the electrode at the welding temperature, causing the electrode to break and come into contact with the pressing member. Significant difficulties arise in that the bond between the components loosens and the current conductivity and heat extraction therefore change, which ultimately results in uncontrollable changes in the welding parameters and/or a reduction in the electrode service life. .

These difficulties, which already occur in spot welding electrodes, are disproportionately increased in the case of composite electrodes for roller seam welding, which may consist, for example, of a copper roller with a coating layer of tungsten or the like on its circumference. The reason for this is that in this case a uniform current and heat transmission over the entire circumference of the electrode and a satisfactory bond must be maintained under the influence of rolling movements on the weldment, which is also required. This is because the service life is extremely long. A satisfactory construction of a composite electrode for roller seam welding is not yet known.

The object of the invention is to improve a device of the type mentioned at the outset in such a way as to avoid constant consumption of the wire electrode and to obtain a high service life of the device without changes in the welding parameters due to electrode contamination. be.

According to the invention, this object is achieved in a device of the type mentioned at the outset, in which the contact member is made of a non-alloying, heat-resistant material, surrounds the pressure member and guides or guides it in such a way as to permit relative movement of the pressure member. The solution is that it is configured as a rigid ring that is retained.

Thereby, the contact member is practically free from alloying contamination due to the fact that its material does not form alloys with the welding object, and due to its heat resistance there is no cross-sectional change due to welding pressure and welding temperature. The advantage is therefore that a high service life is possible without changes in the welding parameters. Such material selection is
This is not possible with known devices with linear electrodes flexibly guided on deflection rollers due to the constantly repeated bending deformations during rotation. On the other hand, compared to composite electrodes, in the device according to the invention the pressure member and the contact member do not have a strong mechanical connection, so that the different thermal expansions mentioned above do not cause such a connection to loosen, and therefore This has the advantage that no controllable changes in the current and heat conductivity and thus in the welding parameters occur.

According to one embodiment of the invention, the ring-shaped contact element is arranged concentrically with respect to the pressure element and is rotatably supported on the pressure element by a roller. These rollers also cause electrical current and heat conduction to the contact members.

According to another advantageous embodiment of the invention, the ring-shaped contact element has a larger diameter than the pressure element and carries out an eccentric rotational movement relative to the pressure element.

This has the particular advantage that the contact element has a significant part of its rotation path extending at a distance from the pressure element and can therefore be cooled or cleaned of deposits independently of the pressure element here. have In its rotation path extending at a distance from the pressure element, the contact element can be guided and supported by additional guide rollers.

The drive of the rotating contact member can be caused by a pressure member or by one or several drive rollers engaging the contact member.

A cooling device, for example in the form of a fan, and/or a cleaning device for removing deposited tin or the like from the contact member are preferably arranged in the part of the rotation path of the contact member that extends at a distance from the pressure member. This cleaning device may consist, for example, of a brush or a scraper, optionally combined with a heating device for heating the part to be removed to melting temperature.

In another particularly simple and advantageous embodiment of the invention, a ring-shaped contact element with sufficient radial movement for radial thermal expansion between the clamping or mounting surfaces of the pressure element is a current- and heat-conductor. It is installed with sufficient pressing force.

In this case, in contrast to the embodiments described above, the significant contact pressure between the pressure element and the contact element is not only due to the pressure on the weldment, but also completely independently of this, in general, in the ring plane and together with the weld. Procured by a clamping force acting perpendicular to the direction of pressure on the object. By determining the clamping force in such a way that radial thermal expansion is also possible, it is ensured that no high thermal stresses can form in the electrode and that no cracks in the electrode or loosening of the contact elements can occur. This results in a sufficiently defined current and heat transfer between the pressure element and the contact element of the electrode, which is sufficiently independent of local heating.

The clamping and uniformity of current and heat transfer can be achieved by mounting and/or clamping surfaces using additional means, e.g. clamping devices such as expansion screws, spring members, etc., which have a clamping force independent of material expansion. Further improvements can be made by arranging the pressure element or the contact element obliquely to the axis and/or by coating the mounting or contact surfaces of the pressure element or the contact element. Such and other embodiments of the invention are set forth in the following claims.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to FIG. 1, two roller electrodes made of copper are provided which are rotatably mounted, driven, connected to a welding power source and cooled in the conventional manner (therefore not shown), between which The metal plate 2 to be welded passes through. However, the roller electrode 1 does not come into direct contact with the metal plate 2, but in each case a ring 3, made of a heat-resistant material sintered with tungsten, molybdenum or a similar alloy, passes between the roller electrode 1 and the workpiece 2. Useful for pressing onto the workpiece. The ring 3 made of tungsten, molybdenum, etc. may be manufactured by any method, such as sintering, forging, casting, cutting, lathing, etc. Therefore, the roller electrode 1 is regarded as a pressing member and a current supply part, and the ring 3 in contact with the workpiece 2 is
are considered to be contact members of the device. The ring 3 has a larger diameter than the roller electrode 1, so that the current transmission from the roller electrode 1 via the contact element 3 to the workpiece 2 takes place in the area of the welding point forming the weld seam. It is only a matter of contact.
The ring-shaped contact member 3 extends at a constant distance from the pressing member 1 on the other part of its rotation path. The contact member is now provided with an additional support and guide roller 5
The roller may be supported and guided by a roller electrode 1 serving as a pressure member, as well as a groove on its circumference for guiding a ring-shaped contact member 3. One or several support and guide rollers are designed as drive rollers and can be driven simultaneously for driving the pressure member 1 and for transporting the welding workpiece 2.

Furthermore, along the rotation path of the lower contact element 3 in FIG. 1, a purification station consisting of a heating element 6, a wire brush 7 and a receiver 8, and a cooling station with a fan 9 are shown. Of course, corresponding devices can also be provided for the upper contact element 3.

Depending on the material and the purpose of application, the contact element 3 can have various cross-sectional shapes, such as are advantageous in order to obtain an optimum weld seam, as high a pressing force as possible and/or as good a guidance as possible for the pressing element 1 or for the guide roller 5, e.g. It may have a circular, square, or wedge shape.

In the embodiment shown in FIGS. 3 and 4, each electrode consists of a roller-shaped pressure member 1, which, unlike the previous embodiment, does not have to be rotatably mounted. On the outer circumference of the pressure element 1, which is preferably made of copper and is connected to the welding current feed line and is capable of applying a force directed to the workpiece, a ring 3 made of tungsten, molybdenum, etc. is arranged around the rollers 10. Since the ring 3 is rotatably supported by the rim in the form of a roller bearing, the ring 3 can perform a rotational movement about the pressing member 1.
The welding pressure and the welding current are transmitted by the pressure element 1 via the rollers 10 to the ring 3 serving as a contact element and from this ring to the workpiece 2 to be welded. The lower electrode in FIG. 3 has the same structure as the upper electrode and is therefore not shown in detail. In order to simultaneously drive the ring 3 relative to the workpiece 2, a circumscribing drive roller 5 can be used.

5 and 6, the ring-shaped contact member 3 is supported in the groove of the pressure member 1 by a ball 10', so that
This differs from the illustrated embodiment. Furthermore, contact member 3
Since a special drive roller for the welding part 2 is omitted, its drive is carried out by entrainment by the weldment 2. Otherwise, the structure and operation are the same as in the previous embodiments.

The roller electrode illustrated in FIG. 7 is constructed as a copper roller and has a pressure member 1 which is divided into two halves 1a and 1b and which can be tightened together by screws 15. Both parts 1a and 1b form a circumferential groove into which a ring-shaped contact element 3 made of a heat-resistant, non-alloying material, for example tungsten, molybdenum or an alloy thereof, is clamped. Therefore, the contact member is connected to both electrode halves 1a and 1b by means of screws 15.
It is tightened between the tightening surfaces 11 and 12 of.
The tightening force by the screw 15 is applied to the tightening surfaces 11 and 12.
A satisfactory current and heat transfer is ensured in the radial direction, but on the other hand, a relative radial movement between the contact member 3 and the pressure member 1 due to the different thermal expansions is possible to a large extent unhindered. It is determined to be. The screw 15 is preferably constructed as an expansion screw, so that it produces a clamping force that is largely independent of the heating of the pressure element 1.

The space between the two halves 1a and 1b of the pressure element 1 may be configured as a cavity 17 for circulation of coolant. Overlapping annular collar 18,1
9 makes it possible to additionally seal off the coolant from radially escaping. The coolant supply device is not shown, as is the connection device between the pressure member 1 and the drive shaft, which can, for example, exert a feeding force on the welding piece onto a roller electrode.

The roller electrode illustrated in FIG. 8 differs from the roller electrode according to FIG.
The clamping surfaces 13 and 14 of which a and 1b are clamped to the contact member 3 extend obliquely to the electrode axis;
In other words, the difference is that it is a conical surface. Correspondingly, the contact surface to which the contact element 3 belongs is also conically inclined. The contact element 3 extends on the outside in a blade-like manner, as in the embodiment according to FIG. 7, depending on the desired width of the weld seam to be produced.

In the embodiment according to FIG. 8, both electrode halves 1
a and 1b are screws 15 with disc springs 16 inserted between them.
are tightened together. These disc springs absorb changes in the axial distance of the two parts 1a and 1b of the pressure member, which occur due to axial thermal expansion and radial thermal expansion due to the inclined mounting surfaces 13, 14, and provide an approximately constant clamping force. can be maintained.

The clamping surfaces 11, 12, 13, 14 and/or the contact surfaces of the contact member 3 adjoining thereto are provided in order to favor the transmission of electrical current and heat and/or to reduce friction during relative movements due to temperature.
A suitable coating can be provided, for example silver plating.

The embodiment according to FIGS. 7 and 8 has the advantage that the contact member is not concentric with respect to the pressure member, but is arranged eccentrically, as in the embodiment according to FIG. 1, and also relative to the pressure member. It can also be modified to perform a type of stagger. Instead of screws and springs, other tightening devices known to those skilled in the art can also be used to attach the contact elements.

Instead of the circular, rectangular or blade-shaped cross-sections of the contact elements shown, band-shaped or oval cross-sections can also be used. Furthermore, various driving methods are also possible. It is also possible to drive the pressure member, which transmits its movement to the contact member. On the contrary, it is also possible to drive the contact element, which itself entrains the pressure element. It is also possible for the feed drive to act only on the welding piece back and forth, and for the movement of the contact element and the pressure element to take place exclusively by frictional entrainment.
Particularly good welding results are achievable if the workpiece and the electrode system are driven simultaneously.

The device according to the invention works with significantly higher pressing forces compared to copper wire electrodes, thereby achieving a good collapse seam formation and avoiding material thickening in the seam area, which is necessary in each case for the desired current concentration. electrode penetration depth can be achieved. In this case, due to the good heat resistance of tungsten or comparable materials, virtually no cross-sectional changes and/or elongations of the contact element occur. Furthermore, by means of the alloy-inert contact element, no or only minimal removal of coating metal, such as tin, from the welding point occurs, so that a weakening of the corrosion protection in the seam area is avoided.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an electrode device according to an embodiment of the device according to the invention, and FIG.
3 is a side view of another embodiment of the electrode device according to the present invention, and FIG. 4 is a cross-sectional view of FIG.
5 is a corresponding side view of a variant of the embodiment according to FIG. 3; FIG. 6 is a cross-sectional view of FIG.
7 is a partially sectional side view of a roller electrode according to another embodiment of the invention, and FIG. 8 is the same as FIG. 7 of another embodiment of a roller electrode according to the invention. A side view is shown. DESCRIPTION OF SYMBOLS 1... Roller electrode, 2... Welding object, 3... Ring-shaped contact member, 4... Welding seam, 5... Support and guide roller, 6... Heating device, 7... Wire brush, 8... Receiver, 9... Fan, 10... Roller, 11, 12...tightening surface, 15...screw.

Claims (1)

[Claims] 1. At least one electrode device arranged for rolling movement over the workpiece, which device does not contact the workpiece and is connected to a current supply device, for electrical and thermal power supply. Electrical conductor having a pressing member made of a highly conductive material, for example copper, and a contact member which is constructed as an endlessly rotating element and is adapted to roll into contact with the workpiece and which can be pressed against the workpiece by the pressing member. In an apparatus for resistance roller seam welding, the contact member 3 is constructed as a rigid ring of non-alloying material, which surrounds the pressure member 1 and is guided or held in such a way as to allow relative movement to the pressure member. A resistance roller seam welding device characterized by: 2. Device according to claim 1, in which a ring-shaped contact member 3 is arranged concentrically with respect to the pressure member 1 and rotatably supported thereon by rollers 10 or balls 10'. 3. Device according to claim 1, in which the ring-shaped contact member 3 has a larger diameter than the pressure member 1 and performs a concentric rotational movement relative thereto. 4 The ring-shaped contact member 3 has a support and guide roller 5 in its area extending at a fixed distance from the pressing member 1.
4. The device of claim 3, wherein the device is rotatably supported by. 5. The device according to any one of claims 1 to 4, wherein the rotating contact member 3 is driven by the pressing member 1. 6. Apparatus according to any one of claims 1 to 5, in which a drive roller 5, which can be driven simultaneously with the feeding of the workpiece, engages the contact member. 7. The contact element 3 and the pressure element 1 and/or the guide and drive roller 5 are provided with roughened surfaces on their mutually contacting surfaces and/or with corrugated grooves cooperating in the form of a gearing. The device according to paragraph 6 or paragraph 6. 8. The device according to any one of claims 1 to 7, wherein the pressing member 1 has a guide groove adapted to the cross section of the contact member 3. 9 Pressing member 3 is circular, flat, or welded object 2
9. A device according to any one of claims 1 to 8, having a wedge-shaped cross section towards. 10 A cooling/ventilation device 9 and/or a purification device 6, 7, which acts on the contact member 3, is provided in the rotary path portion of the contact member 3 extending at a certain distance from the pressing member 1.
8. The device according to claim 3, wherein: 8 is arranged. 11 Tightening surfaces 11, 12, 13 of pressing member 1,
2. Device according to claim 1, characterized in that between 14 a contact member (3) with sufficient radial movement for thermal expansion is mounted with sufficient pressure for electrical current and heat transfer. 12 Pressing member 1 has clamping surfaces 11, 12, 1
Two parts 1 with one each of 3 and 14
a, 1b, and this part consists of tightening members 15, 1
12. The device according to claim 11, wherein the devices are clamped together by 6. 13. Device according to claim 12, characterized in that the clamping element is constructed as a screw 15 with a spring 16 or as an expansion screw. 14. Parts 1a, 1b of the pressure member enclose a cavity for coolant circulation between them, as claimed in claim 12.
Apparatus described in section. 15. Device according to claim 14, in which the cavity 17 is sealed against the contact member 3 by sealing parts 18, 19. 16. The device according to claim 11, wherein the clamping surfaces 13, 14 of the pressure member 1 and the contact surfaces of the contact member 3 cooperating therewith are inclined with respect to the electrode axis. 17 The clamping surfaces 13, 14 and/or the contact surfaces of the contact member 3 cooperating therewith are anti-friction and/or
2. A device according to claim 1, or having a coating that improves current and heat transfer, for example silver plated. 18. The device according to any one of claims 1 to 17, wherein the contact member 3 is made of tungsten or molybdenum or an alloy thereof.