Patent GB-507541-A (GB)
Title: Improvements in or relating to automatic electric resistance welding machines
IPC: B23K11/24
Filed: 1938-11-19
Abstract: 507,541. Electric welding. PATENT-VERWERTUNGS-GES. HERMES. Nov. 19, 1938, No. 33711. Convention date, Nov. 19, 1937. [Class 83 (iv)] In an automatic electric-resistance flash welding machine the forward feed movement of the work is controlled by a member which, operating in dependence on time and/or on the condition of the work, periodically raises and lowers' the speed of the forward feed and/or the energy consumption of the welding transformer in order to impart one or more intermediate fusing periods during the welding operation so as to smooth the faces particularly of very irregular work parts. The member may be variable, and may consist of a length measuring gauge coupled to the work slide or its drive and controlling either mechanically or through relays an output regulator in the primary of the welding transformer or a speed governor in the current circuit of the forward feed motor or both, or may consist of a time mechanism such as a relay which functions in dependence on time. The rails 6, 7 or other parts to be welded may be secured respectively in a fixed clamp 4 and in a clamp 5 carried by a slide 9, the clamps being connected to the secondary 3 of a transformer. The slide is normally reciprocated by a screwed spindle 13 carried thereby and engaging a nut in a worm wheel 17 and driven by worm gear 12, 11 from a direct-current motor 10 whose field contains a variable resistance 23 -and whose armature is connected to the mains 24 through polarity reversing switches 21, 22. The clamps are connected to a voltage coil 260 and the secondary terminals of the transformer to a voltage coil 261, the coils being so dimensioned that with equal voltage the attractive force of the winding 260 predominates. These coils control a change over switch 25 for the motor 10. The transformer primary 2 is connected through a switch 1 to the conductors R, S, of a three-phase current network and has a tapping 200. When the main switches 33, 34 are closed by push buttons with the work parts out of contact and with the switch 1 engaging the contacts 100, the whole of the primary is energized and the coil 260 operates the switch 25 to bridge the contacts 250 and through relay 210 to close the switch 21 so as to set the motor running in the forward direction with the resistance 23 in circuit. When the parts come into contact the voltage across the clamps falls and the coil 261 reverses the switch 25 and so causes the switch 21 to be opened and the switch 22 closed for backward running of the motor. After the parts separate the voltage across the clamps increases and the switch 25 is again reversed for forward running. This process is repeated for a definite period the slide moving progressively forward each time the parts make contact due to burning off from the ends of the work. Eventually an adjustable control finger 280 carried by a rod 32 projecting from the slide 9 closes a switch 28 so as to cause the switch 1 to be raised into the position shown, whereupon the resistance 23 is short circuited so as to reduce the speed of the motor and the primary is connected through the tapping 200 so as to increase the energy consumption of the transformer. In consequence a continuous forward feed is maintained until the finger 280 leaves the switch 28, whereupon the previous conditions are re-established to effect further reciprocating movements. When the switch 28 is again closed by a finger 281, a continuous forward movement is again effected until a contact finger 310 closes a switch 31 so as to connect a three phase upsetting motor 19, which rotates through worm gear 18, 17 the nut engaging the spindle 13. After traversing the required upsetting distance, or after a required time interval, or when a particular upsetting pressure is attained, the relays 330, 340 are.brought by a time running mechanism or by a further control finger on the rod 32 into switched out position to stop the machine. In a modification reduced forward speed and/or increased energy consumption may be used during the preheating and final welding effected at greater speed and with reduced energy consumption. The direct current motor may be replaced by a single or multiple phase alternating current motor, and the variation of speed and direction of motion of the slide may be effected through reducing or reversing gears. The double acting relay 261, 260 may be replaced by a simple voltage or current relay or by a differential relay responding to voltage and current. The intermediate fusing stages may be switched out, if desired.