Patent GB-1285285-A (GB)
Title: Travelling arc-welding apparatus
Inventor: RANDOLPH JAMES B
IPC: B23K9/02
Filed: 1970-06-04
Abstract: 1285285 Welding by fusion CRC-CROSE INTERNATIONAL Inc 4 June 1970 [4 June 1969] 26984/70 Heading B3R A MIG butt welding apparatus comprises a carriage movable along a guide track capable of being secured adjacent the line of the joint to be welded and a welding head movable transversely of the joint. The apparatus is particularly for use in butt welding of pipes but may also be used for butt welding flat plates. In Figs. 1, 3 a transversely oscillatable and adjustable welding head 61 is supported on a carriage 21, on the one hand via a stiffly resilient coiled metal spring wire guide 104 tending to centre, but permitting transverse deflection of, the head, and on the other hand via a bracket 57 pivoted on the carriage. The bracket 57 has adjustably slidable thereon a plate 140 having arms 134, 136 provided with cam followers 137 selectively engageable, by means of knobcontrolled eccentric 164, with cam grooves disposed on opposite sides of a cam 130, each cam providing a different amplitude of head oscillation. The cam 130 is rotatable, via a gear reducer (128), by a motor 126 which is connected to the carriage by a screw 120 adjustment of which varies the general transverse position of the head. Consumable electrode wire from a reel 72 is taken through flexible and semiflexible tubes 60, 102, motor-driven and spring- pressed feed rollers (82, 84) and the wire guide 104. The carriage has grooved rollers 23, 25 engaging a flexible guide track 27 held by tension on the workpiece surface. One or more carriages may be used on tracks 27, 33 on either side of the joint. The carriage, controlled from a box 39, is propelled by one or more of the grooved rollers driven by an electric motor 43. A connection 70 to the welding heads supplies welding current and shielding gas (e.g. nitrogen, argon). With neither cam follower 137 engaging a cam groove, the head is held by the guide tube and does not oscillate. In Fig. 10, a pivoted welding head supporting bracket 57a is axially movable, against a spring 300, by a face cam 130b to provide for longitudinal reciprocation of the head. Transverse oscillation may be added to the longitudinal oscillation to achieve more complex weaving patterns. In Fig. 13 (not shown), the reciprocation cam is double acting so that the spring 300 may be dispensed with. In Figs. 6-8 (not shown), a screw directly transversely adjusts a pivoted bracket 57 supporting the welding head, no provision being made for oscillation. Welding of thick-walled pipes may comprise the following steps: (i) making an initial inner pass manually or automatically and preferably internally, (ii) making one or more rapid " hot " passes using heavy current, from the outside, to fuse into the inner pass and the workpieces, and (iii) making one or more cooler, slower, oscillated head, passes, the latter acting as a corrosion resistant cover for the corrosion susceptible austenitic conditions created by the " hot " passes. The hot pass step may be effected, using the apparatus of the invention, by making one or more vertical electrode feed passes, one or more angled passes, or a combination thereof. When making angled passes, the weld gap may be filled by alternate side corner passes, as by alternately using separate heads respectively on tracks mounted one on each side of the joint. The joint preparation may comprise, from inside to outside, a small V, a narrow land where the adjoining pipe ends actually or nearly abut, a perpendicular or nearly perpendicular wall stepped back, say 1/32-1/8 inch, in one or both pipe ends, and a wide V.