DK141774B - STANDING WELDING HEAD FOR WELDING OF THIN THROUGH SEATING PLATES - Google Patents

Description

141774

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed welding head for welding thin continuous sheet metal, and in particular for welding under a protective gas of the longitudinal edges of a metal strip by means of three non-melting electrodes arranged in a row in the welding seam direction. , where the electrodes fed above the continuous sheet plates and collectively fed from separate power sources can be adjusted vertically and horizontally across the weld seam.

10 A welding head is known for welding the edges of a metal strip, which consists of three consecutive electrodes. The electrodes are arranged in electrode holders which can be adjusted vertically and horizontally separately. These measures allow a precise adjustment * of the electrodes in accordance with the current welding conditions. The electrode holders are made of a ceramic material with a high thermal conductivity, which electrically insulates the electrodes assembled into a unit electrically, cf. German Publication No. 1,615,341.

In the manufacture of copper or aluminum pipes, it would be possible without difficulty with the known welding head to increase the welding process speed by a factor of three (due to the three electrodes) relative to a welding head with only one electrode. However, steel strips and especially strips having a thickness 25 of less than 1.5 mm caused difficulties as this material in an area behind the forming mechanism which forms it along longitudinal metal strips into a slit tube and whose final step consists of a forming ring , which encloses the tube versatile, spring back due to the aluminum-copper and copper higher elastic limit. Since the rear electrode, viewed in the direction of movement of the tube, was placed too far away from the molding for structural reasons, and as the melting bath produced by the rear electrode formed in an area where the band edges tended to spring back, i.e. to remove from apart, it was not possible to obtain a flawless weld seam in connection with such steel pipes.

In view of this, it is the object of the invention to improve the known welding apparatus so that it is also possible to weld a pipe of steel strip of lesser thickness.

This object is achieved with a welding head of the kind mentioned in the introduction, which according to the invention is characterized in that the two outer electrodes have a slope relative to the direction of the welding seam and can be tilted to adjust this inclination and are adjusted so that during the welding process, the melting baths provided by their arcs overlap the melting bath of the middle electrode. By these measures it was possible to place the melting bath of the rear electrode approx. 16 mm closer to the molding ring.

15 In order to be able to adjust the electrodes to the current welding conditions, the electrodes can be individually adjusted in vertical direction.

According to a particularly convenient development of the invention, the outer electrodes are mounted in a bearing and arranged pivotally around a fixed point located within the region of the bed by means of a setting screw which attacks the electrode at the end opposite the electrode tip. This mounting allows for an oscillation of the outer electrodes at some degrees. A particularly advantageous material for storing the electrode has been found to be polytetrafluoroethylene.

The invention is explained in more detail below with reference to FIG. 1 and 2, which diagrammatically show an embodiment of a welding head according to the invention viewed transversely, respectively, along the direction of spacing.

In a manner known per se, by means of a forming member not shown, a tube 1 is formed of a longitudinal metal strip, e.g. a steel band the thickness of which is less than 3

U177 A

1.5 mm. This tube is fed to a welding head 2 which, in particular, is shown in FIG. 1, consists of three in the welding direction on a series of electrodes 3, 4 and 5. The middle electrode 4 is arranged vertically, while the outer electrodes 3 5 and 5 are arranged with a certain inclination. The welding head 2 is attached to a welding head holder 6. As a result of the outer electrodes 3 and 5 being arranged with a certain inclination, it has become possible to place the total welding head 2 closer to a forming ring 7 in the forming member and thus bringing it to a melting bath. formed by the electrode 5 into an area where the band edges of the tube 1 are still held together by the forming ring 7.

The two outer electrodes 3 and 5 are pivotally mounted in plastic electrode holders 8. To this end, a bearing 9 of polytetrafluoroethylene serves as well as a set screw 10 which engages the electrode at the opposite end of the electrode tip, so that this set screw pushes the end of the electrode against a biased spring 11. This oscillation of the outer electrodes allows an exact fine adjustment.

In FIG. 2 shows a section through the welding device 2.

The electrode tip 12 is clamped in a longitudinally slotted clamping rod 13 and protrudes a short distance from a protective gas nozzle 14. The clamping pliers 13 are secured to an electrode holder 15 which is mounted by means of the bearing 9 in the interior of the electrode holder 8. The outer electrodes can be pivoted about an axis A. In addition to the pivotality about the axis A, each electrode can be further displaced in its longitudinal axis. This can be done by means of a setting screw 16 which moves via a thread 17 on the clamping pliers 13 in the electrode holder 15. A setting screw 18 serves to clamp the electrode tip 12 30 into the clamping pliers 13. The welding head 2 can be moved vertically by means of a setting screw 19 direction. Furthermore, a swing of the welding head around a point B is possible.