Patent GB-1534257-A (GB)
Title: Automatic welding apparatus
IPC: B23K9/028
Filed: 1977-05-16
Abstract: 1534257 Welding by fusion Z LEVIN 16 May 1977 20434/77 Heading B3R [Also in Division F2] An orbital apparatus for arc butt welding together the ends of workpiece pipes P 1 , P 2  comprises a wheeled carriage 3 engaging and selfdriven around one of the pipes, the carriage mounting a sprocket 5 engaging a chain 2 wrapped around said workpiece pipe, a turret 14 mounted on said carriage for indexing about an axis disposed radially of the workpiece pipes, and a plurality of rectilinear groups of holders 67 for consumable rod electrodes 69 carried in generally circular array by the turret and provided with drive means for feeding the electrodes radially of the pipes, the arrangement being such that as the turret is orbited around the pipes it is periodically indexed so as to bring successive groups of electrodes into the plane of the pipe joint, the interval between indexing being determined by the time taken for consumption of an electrode group. As shown, there are three electrodes 69 per group increasing in diameter from the leading to the trailing. The respective leading, intermediate and trailing electrodes of all of the groups are supplied with different currents via three concentric rings 93-95 carried by the turret and are fed at different speeds towards the workpiece pipes. Carriage drive, turret indexing and electrode feed are all derived from a single electric or hydraulic motor 8. Turret indexing (Figs. 1, 10, 12).-A shaft 17 gear driven from the motor 8 drives a sleeve 25 via a spring-loaded slipping saw-toothed clutch 18 and gears 22, 23. A spring-biased pawl 27 is mounted on an arm 29 which is continuously oscillated by a crank 31 also geardriven from the motor 8. Once per revolution of the sleeve 25, the pawl enters the latter through a port 36 thereof to engage and index a ratchet wheel 26 fast with the turret 14. Between indexing, the turret is locked by a spring-loaded pin 42 engaging a notched wheel 40 fast with the turret, and a cam 37 fast with the gear 22 acts to withdraw the pin 42 to allow indexing. Electrode feed (Figs. 1, 4, 7, 8).-The electrode holders 67 are fast with racks 68 which, on turret indexing, are brought into mesh with gears 76-78. The latter are bevel gear-driven by shafts 52-54 in turn driven from the motor 8 via gears 48-51 and spring loaded, selectively disengageable, overload - slipping clutches 55-57. In respect of the first group of electrodes, the clutches 55-57 are manually disengaged and held by pins 84 and are sequentially spring engaged, by spring release of the pins under control of cams 88 driven by the motor 8, to start three successive weld layers. In respect of subsequent groups of electrodes, the clutches 55-57 are disengaged and engaged by turret mounted cams 82 engaging clutchactuating levers 79-81. Arc striking.-The first group of electrodes are depressed and subsequently spring-raised for arc striking by sectors 71A which engage the racks 68 and are acted on by cams 89 driven by the motor 8. For the subsequent groups, similar sectors 71 are depressed by a fixed cam 75 on indexing movement of the turret. For the last group of electrodes, holders 102 are pivoted on their racks 68, the arrangement being such that electrical contact to the electrodes is broken by electrode pivoting when the beginning of the weld seam is reached.