Patent GB-1493835-A (GB)
Title: Apparatus for welding
IPC: B23K9/127
Filed: 1974-09-18
Abstract: 1493835 Welding by fusion GLITSCH Inc 18 Nov 1974 [19 Nov 1973] 49797/74 Heading B3R [Also in Division G3] Arc welding apparatus for automatic lap seam welding together two sheets each having intersecting spaced corrugations 12, 13, the welding being effected along a seam disposed transversely of the corrugations 12, comprises a track 17 attachable to one said sheet parallel to the sheet seam edge and in any spacial orientation of the sheet (e.g. horizontal, vertical) by clamps 14 adapted to grip sheet protuberances formed at the corrugation intersections, a carriage 19 traversable on the track, a weld head 41 traversable on said carriage perpendicularly to the carriage movement direction and arcuately in a plane parallel to the track, the weld head carrying a torch 43 and a mechanical sensor 44 which on detection of the presence of a corrugation as the carriage is traversed along the track initiates card programmed control of the head to weld around the corrugation. The apparatus is particularly for use in the construction of liquefied gas or fuel shipping containers. The clamps 14 comprise fixed and levermovable soft-faced members 52, 54 shaped to embrace the corrugation 13 and to engage the opposite sides of the intersection protuberances, the latter having clamp retaining depressions 58. The track 17 is secured to the clamps by means allowing relative transverse adjustment. The carriage 19 is traversable by a motor 26 via gearing 25 engaging a track rack 24. A subcarriage 28 is traversable on the carriage, perpendicularly to the track, by a motor 31 via a screw 30. The weld head 41 is pivotally mounted on the sub-carriage 28 and is arcuately movable by two simultaneously energizable motors 34, 39 respectively carried by the subcarriage and the weld head and having pinions engaging twin rack segments 33, 36 fast together and pivotable on the sub-carriage, the use of two motors doubling the speed of weld head arcuate traverse. A motor 61 moves the torch 43 with respect to the head 41 in response to an arc-voltage control unit 42, to cater for small workpiece surface deviation. The torch is gas purged before welding commences. The card-programmed control comprises eictrostatic reading devices 63a-63f into which are fed cards bearing information in the form of lines or wave forms interrupting uniform electrostatic fields on the cards. Reading is by detection of voltage representing position of field interruption. The cards are propelled through the reading devices on receipt of a command amplitude and width. A further reading device may be provided to determine pulse slope. The motors 26, 31 and 34, 39 are controlled, under command of the sensor 44, by the reading devices 63d-63f, the devices 63e, 63f acting via follow-up circuits 92, 104 using motor movement responsive potentiometers 90 and 98, 100. The signal and after use re-cycled. The reading devices 63a-63c control A.C. pulsed D.C. to the welding torch, 63a determining basic D.C. voltage and 63b, 63c superimposed A.C. pulse arc voltage control unit 42 comprises a circuit 73 which detects deviation between a desired arclength voltage and one sensed at 75 and uses the deviation to control the torch motor 61 via a follow-up circuit using a torch position potentiometer 71.