GB1388877A - Device for controlling the movement of a welding electrode along the butt of adjacent parts being welded - Google Patents

Abstract

1388877 Welding by fusion INSTITUT AVTOMATIKI MINISTERSTVA PRIBOROSTROENIA SREDSTV AVTOMATIZATSII I SYSTEM UPRAVLENIA SSSR 1 Dec 1972 55553/72 Heading B3R [Also in Division G3] An electrode 3 in seam welding apparatus is automatically guided to follow a butt 2 by a system in which the butt is detected photoelectrically by a device 1 connected to the electrode carriage. A projected light beam is reflected from the plates 4, 5 in the vicinity of the butt and imaged at an aperture which is scanned by a rotating slotted disc. The resulting output from the photo-cell is shown in Fig. 3a in which the first dip indicates the butt. This signal is shaped at 6 to produce Fig. 3b; T1 equals T2 when the electrode is centralized. The output of 6 is fed to two further signal shapers 7, 8 whose outputs are positive and negative pulses which are summed at 10 (the sum should be zero) and the result integrated at 11 to produce a voltage which is proportional to the electrode position error. This error signal is fed through a logic unit 14 to a controller 12 for an actuator 13 which positions the electrode carriage. A similar arrangement comprising a detector 16 and shaping and integrating circuits 17 ... 20 looks at the finished weld and overrides the first system, by logic 14, if the weld is incorrectly positioned. The detector 1 also determines the width of the butt and adjusts the welding current accordingly, by unspecified devices 21 ... 23. Also, the width of the weld, detected by 16, is used to control the feed speed of filler wire, by devices 24 ... 26. The action of all the control systems are suspended by an "inhibit" network 27 ... 30 in the event of spurious signals such as that constituting the second dip in Fig. 3a. Logic circuit 27 receives signals from the shapers 7, 8 (also from shapers 17, 18 by connections not shown) and from a "counter" 28. This determines when a dip occurs at a time when a plate is being scanned (i.e. during T2, Fig. 3b) and operates a flip-flop 29 controlling an inhibit switch 30. The circuits of the various devices are illustrated in Fig. 2 (not shown); in the main they comprise transistor bi-stable devices.