GB1172663A - Apparatus for Welding a Circular Joint Between a Tube and a Tube Plate. - Google Patents

Abstract

1,172,663. Welding by fusion. ESAB Ltd. 29 March, 1968 [31 March, 1967; 7 July, 1967], No. 15274/68. Heading B3R. [Also in Division H2] Apparatus for welding a circular joint between a tube and a tube plate comprises a centring member 17 at the extremity of a rottable shaft 18, 7, the centring member being adapted to engage the work in such a way that the axis of rotation of the welding head 9, e.g. a TIG welding head, is aligned with the axis of the tube to be welded, the centring member being normally biased by a spring 39 to an inoperative position in which it is withdrawn from the work, but displaceable to engage the work by operation of a pivoted lever 24 coupled to the shaft 18, 7, in a direction towards the handle 3 against the action of spring 39. The welding head, which may be supplied with argon shielding gas, is mounted adjacent a recess in the lower end of the shaft 7 (Fig. 5, not shown), whereby the radius of the circular joint may be varied by moving the head into or out of the recess. The head rotates with the shaft which is driven by a motor 26 through gearing 27. In its inoperative position with the centring member withdrawn from the work, the lever 24 closes a switch M whereby an electromagnet 2 is energized to clamp the apparatus to the work. Operation.-The apparatus is correctly located for welding by engaging the centring member with the tube end by moving the lever 24 towards the handle 3. Push-button K is then depressed and energization of relay contact a2 establishes a feed circuit for the electromagnet 2. Also, a solenoid valve 33 is energized to supply shielding gas to the welding head. When handle 24 is released again (after pushing button K), an ignition relay I operates to connect the welding head to the welding voltage generator G, e.g. a D.C. device, and to connect an H.F. current source H to the primary of a transformer 34. As soon as the arc starts the H.F. source is automatically disconnected and a timing relay T is energized. Also the motor 26 is energized to rotate the shaft 18, 7. After one revolution of the welding head a relay F operates to reduce the excitation of the generator and after a delay the welding current is reduced again. Then the alternative energizing circuit (using switch M) for the electromagnet is restored and the ignition relay I de-energized to extinguish the arc. The supply of gas is cut off. The unit is moved to the next weld location by de-energizing the electromagnet by moving the lever 24 towards the handle 3. If the tube plate is, e.g. non- magnetic stainless steel, then a magnetic support plate which may be as disclosed in Specification 1,172,197 is fixed over the tube plate for welding.