GB1430041A - Arc welding apparatus - Google Patents

Abstract

1430041 Welding by fusion; grinding COMMISSARIAT A L'ENERGIE ATOMIQUE 9 Jan 1974 [11 Jan 1973] 01091/74 Headings B3R and B3D In a TIG arc welding apparatus, e.g. for welding nuclear reactor fuel rods, a tungsten electrode 33 is mounted in a head 1 which is pivotable between a welding position I and a sharpening position II in which latter position the electrode is brought against a grinding device 25, and means operative with the head 1 in the sharpening position II are provided to rotate and advance the electrode. The apparatus may be disposed in a glove box. Operational control may be by programmer or manual. As examples, a single sharpening may be effected after two or three successive weldings, or two sharpenings may be effected after a single welding. The head 1 is pivotable on a shaft 11 supported on a column 3 vertically adjustable by manually operable screw and nut 5, 6. The head is biased towards position II, determined by an adjustable stop 31, by a spring 24 which acts via an articulated lever 20a, 20b on a head peg 22. The head is moved between positions I, II by a screw jack 13 driven by a motor 18. By laterally moving the lever section 20a to clear the peg 22, the head may be pivoted to an electrode replacing position III. The grinding device 25 is mounted on a slide 27 on the column 3 and comprises an electric motor driven grinding wheel 28, e.g. diamond set, enclosed in a casing 30 provided with an abrasive particle outlet. In the head 1, a shaft 7a, driven by a motor 7, e.g. electric or pneumatic, via a friction coupling 7b, is arranged to rotate a spindle 37 via a sliding key connection 7c. The spindle 37 is journalled in a sheath 40 slidable in a casing 8 of the head. The sheath is fast with a nut 40a which engages a screw 45 and bears an electrode-wear-indicating reference mark 40b co-operating with casing index marks signifying new electrode, worn electrode and electrode release positions. The spindle 37 is fast with a collet 42 which is moved to electrode gripping and releasing positions respectively by a spring (42d) and by engagement of one or more push rods (42e) with a casing end 44. The screw 45 is connected to the shaft 7a, so as to advance the electrode stepwise with rotation of said shaft, by way of a gearing 48, 49, eccentric 50, connecting rod 51, releasable pawl 53 and ratchet wheel 54, the arrangement being such that, as described, for two revolutions of the motor 7 and the electrode corresponding to one sharpening operation, the electrode is advanced only during the first of said revolutions. The head comprises a moulded insulating cone 9 and an interchangeable welding torch 55. A metallic insert 70 in the cone provides for screw acceptance of the torch 55, introduction of inert gas (e.g. He, A) and welding current connection. The torch 55 comprises a ceramic nozzle (55a) enclosing a gas diffuser (55b) and a collet (55d) which is moved to electrode gripping and releasing positions respectively by a spring 58 and by downward movement of a rod 61 acting via a rocket 57. The rod 61 is downwardly moved automatically by a cam 60 when the head 1 is moved into its sharpening position II or manually by a lever 62. The collet (55d) serves as guide and electrical contact means for the electrode. In operation, when sharpening is required, the motor 18 is energized to allow the head 1 to move to the sharpening position II. Whereby the collet (55d) is actuated to release grip on the electrode and to provide a bearing therefor. The motor 7 is then energized so that the electrode is first given a combined rotation and advance and then a rotation only. After sharpening, the motor 18 is energized reversely, and on return of the head to its welding position I, the collet (55d) is spring-actuated to resume its grip on the electrode. After successive sharpenings, the push rods (42e) engage the end 44 to actuate the collet 42 to release grip on the electrode. The head 1 may then be moved to position III and the lever 62 actuated to release the grip of the collet (55d) so that the electrode may be extracted. If electrode change is desired before that in place is consumed (e.g. to insert a different diameter electrode) the motor 7 is rapidly rotated to effect collet release engagement of the push rods with the end 44. For pulling an electrode into the head, the screw 45 may be rotated manually by a knob 66 acting through bevel gears 67, 68.