Patent GB-511591-A (GB)
Title: Improvements in and relating to electric welding machines
IPC: B23K11/24
Filed: 1937-11-15
Abstract: 511,591. Automatic control systems. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 15, 1937, Nos. 31359 and 31360. Void. Convention dates, Nov. 14, 1936, and March 9. 1937. [Class 38 (iv)] [Also in Groups XXII, XXXVII and XXXVIII] In welding curved seams, particularly in containers having locally curved seams, the work is passed at uniform speed in front of the welding tool in such a manner that the tool is always perpendicular to the tangent to the curve. In Fig. 3 a face plate 5 is rotated in a fixed bearing by a motor 6, and carries cross slides traversed by motors 3, 4, the centre of the face plate being at the welding point 7. The speed of the motors 3, 4 is so varied by an eccentric 8 carried by the face plate through control slides 9, 10 and voltage dividers 11, 12 that the work always travels at constant speed in a direction at right angles to the welding tool. Any deviation from this line is corrected by a feeler 18, Fig. 4, in the vicinity of the welding point, which engages contacts 21, 22 for backward or forward running of the motor 6. Correction for non-uniform control of the motors 3, 4 due to load dependence is effected by a second feeler which carries contacts 23 to switch in a motor 24 for controlling this feeler. The speed of the motor 6 may also be regulated in dependence on the position of the feeler so that the follow-up is quicker the more the feeler is shifted, i.e.; the smaller the radius of. the work..In a further 'form, Fig. 8, in which the tool and feeler are mounted in an adjustable arm 92 at the centre of the face plate 77 which is rotated by a motor and carries a compound slide S2, 79, traversed by separate motors M1, M2, the eccentric 82 controls the traversing motors through' a spring-returned slide 85 having a rack engaging a pinion 87 driving a double regulator for the motors. This form is controlled as shown in Fig. 10 two control slides St1, St2 being shown for sake of clearness instead of the double regulator and controlling through eccentric 82 on the face plate 77 voltage dividers Sp1, Sp2, respectively for the traversing motors M1, M2. The work or pattern engaging feelers T1, T2 engage armatures A1, A2 respectively controlling by induction bridge circuits S1, S2, fed by alternating current through transformers Tr4, Tr5. The alternating voltage in the secondary of a transformer Tr, is connected to the paralleled grids of three valves R1, R2, R, in the anode circuit of which is a relay 98, 99 or 100. The valves are given a different direct current bias by voltage dividers and a rectifier Gl so that the alternating voltage produced in the transformer Tr1 allows relay 98 to respond at position 1 of the armature A@, relays 98, 99 at position 2 and all three at positions 3. The secondary of transformer Tr2 is connected to the grid of valve R, in the anode circuit of which are two relays 101, 102 fed by dry rectifiers rectifying one half wave each of the current so that at position 1 of the armature A2 relay 101 responds and at position 2 the relay 102. Direct current for the motors M, M1, M2 is supplied to a generator G from a three phase current motor D. A control drum 93 shown in developed form, is mounted on the axis of the face plate or coupled to it. When one side of the work is at right angles to the tool but not in contact with the feelers, the armatures are in position shown in Fig. 10. On closing the main switch, motor M, is operated to raise the work into contact with the feelers by current from plus terminal of generator through left segment of control drum normally closed contact 105r, second segment from right of drum and armature of motor M1 to potential zero between resistances 111, 112. When the work strikes the feeler T2 armature A, is brought to zero to release relay 101. Feeler T, is then moved to position 1 to energize relay 98 and hence relays 105, 107, 108, 110 and opens contact 105r to stop motor M,. Motor M2 is then energized to traverse the work horizontally to the left through minus terminal of G, voltage divider Sp2, contact 107a and armature of M, to potential zero. When the right corner of the work comes under feeler T2, the latter is moved down to position 1 and relay 101 closes switch 101a to switch in the motor M for anticlockwise rotation of the face plate. When the new surface is horizontal below the feelers the feeler T, is moved to zero to release relay 101 and stop motor M. If the angle of the new surface is e.g., at 60 degrees to the previous one, segments 225‹, 315‹ of the drum are operative and the work is traversed horizontally to the left by the resultant of the motions effected by motors M1 and M2. The eccentric 82 has moved the slide St1 upwards along the voltage divider Sp1 so as to cause the motor M1 to move the work to the left at 60 degrees from the vertical at a velocity somewhat greater than the mean one and the slide St2 has been moved along the voltage divider Sp2 so that the motor M2 moves its slide to the left in a direction at 60 degrees to the first movement and with a velocity somewhat smaller than the mean one. If the work in this position moves away from the feelers, the motor M2 is caused to rotate at full speed in its reverse direction until the feeler T1 again comes into contact with. the pattern since by opening of contacts of relay 98, the contact 108r is closed and current proceeds from plus of G through left segment of drum in position 225‹, 315‹ third segment from left, contact 108r, extreme right segment, to armature of motor M2. If the work is driven too far upwards in this operation the feeler T1 comes into position 2 to energize also relay 99 whereby motor M<2> is switched on to its normal feed direction, the circuit being from minus of G through middle contacts of drum contact 109a, right segment of drum to armature of motor M,.