Patent GB-469282-A (GB)
Title: Improvements in or relating to welding
IPC: B23K11/24
Filed: 1936-07-31
Abstract: 469,282. Current meters. BUDD MANUFACTURING CO., E. G. July 31, 1936, No. 21202. Convention date, Aug. 5, 1935. [Class 37] A welding system comprises, in combination with the welding circuit, means for producing recurring impulses of welding current in the circuit, a heat units indicator responsive to the welding current and the duration thereof and means for electrically connecting the indicator with the welding circuit for a period including only one complete impulse of welding current and excluding the preceding and succeeding current impulses. The welding electrodes 1 are supplied from a transformer 2 which is energized from a source of A.C. supply 9, when a safety switch 59 and a control switch 54 are closed to energize a relay 55, whereby successive relays 56, 57 are energized to close contacts 7, 8, 70, the first two of which are in the circuit of the transformer 2. A timing device 10 of the gas-filled trigger type of relay or of a mechanical type is operative to close and open the circuit of the secondary of a series transformer 11, the variations of impedance in the circuit of the primary of the transformer 2 serving to bring in or cut off the supply current to produce the desired welding current impulses. The timing device also supplies impulses through a rectifier to an electromagnet 28, which at each impulse steps on a contact-making device 30 having arms 31, 32 adapted by the rotation of the device 30 to make contact with studs 74. Of these, the studs 35, 36 are connected together and to a normallv closed contact 81 on an under-weld signalling relay 40, while contacts 41, 42 are also connected together and to a control relay 44, for transmitting impulses to a measuring instrument 22. This comprises a series type motor relay having a spring-biassed rotor 18, carrying a contact member 19 and a suitable recording device co-operating with a recording tape, all as described in Specification 412,418, [Group XXII], which is referred to. In operation, each welding current impulse steps on the contacting device 30 over the dead contact stud 74 until one of the arms 31, 32 engages a stud 35 or 36. At this point, a magnet 26 for feeding the record tape is energized together with the under-weld signal relay 40. The relay 40 opens its initial energizing circuit at contact 81 but completes a hold-in circuit at 85 and a circuit at contact 52 through a signalling device 49. The response of the latter is small, however, before the arm 31, say, engages contact 41, owing to the shortness of the time interval. At this point, relay 44 is energized and removes the short-circuit 45 connected across the measuring instrument 22. At the next welding impulse, a current flows through the instrument proportional to the welding impulse and owing to the nature of the instrument its movement is proportional to the square of the current flowing to its duration and is thus a measure of the heat-units developed in the welding operation. The rotor 18 is rotated and contact member 19 moves towards two fixed contacts 20, 21. Between the limits fixed by these contacts the weld is a good one and provided the member 19 engages the contact 20 the under-weld signal relay 40 is de-energized by a relay 46. If, however, the member 19 reaches the contact 21, an over-weld signal relay 47 is energized which completes a hold-in circuit for the relay at contact 48 and the circuit for the signal 49. The signal 49 is thus operated should faulty welding take place and remains operative until the operator opens a switch 78 and makes the necessary adjustment. The contacts 45 of relay 44 may be controlled directly from the switch member 30, or when a mechanical timing device such as a rotating commutator is used, this switch member and the relay may be replaced by mechanical switching means driven in timed relation with the commutator. A visual or audible signalling device may be employed and different signals may indicate the different faults.