Patent GB-543947-A (GB)
Title: Improvements in or relating to welding apparatus
IPC: B23K11/00
Filed: 1940-10-16
Abstract: 543,947. Welding. WILKIE, L. A. Oct. 16, 1940, No. 15349. Convention date, Oct. 28, 1939. [Class 83 (iv)] In a welding apparatus in which a welding circuit is closed through the ends of parts which are in abutting engagement and forced together to apply the welding pressure means are provided for varying the pressure and welding current simultaneously. The severed ends of band saws of different widths may thus be welded together. The welding apparatus may be mounted on the panel of a metal sawing machine as described in Specification 492,206. Movable and fixed clamps 16, 15 for holding the ends of the saw project through the panel 10, which is also provided with the dial 13 of a voltage control, a dial 12 for a rheostat for varying the current and graduated to correspond to the saw width, a twoway switch 14 to adapt the circuit for welding and subsequent annealing operations, an illuminating lamp 17 and an operating lever 21 mounted on the shaft 58. The clamp 16 is carried by an arm 39 pivoted at 41 and moved between stops 47, 48 by a spring 51 which applies the welding pressure. The current is adjusted by turning the indicator 88 of the rheostat the shaft of which carries a cam 56 engaging a lever 53 so that at the same time the tension of the spring 51 is varied. On the shaft 58 is mounted an arm 59, which is held in the position shown by a spring 62 with its set screw 64 in contact with the arm 39. On pressing the lever 21 the arm 59 closes a switch 60 to connect the welding current. The arm 39 carries at its lower end an arm 43 having at its outer end a screw 45 which normally engages a trigger 74 pivoted on a plate 69 which is itself pivoted at 68 on the panel and pressed down into the position shown in Fig. 7 by a spring 72. The trigger 74 is pressed against a stop 76 on the plate 69 by a spring 77. The plate 69 carries a mercury switch 81. When the work softens the spring 51 moves forward the arm 39 and eventually the screw 45 moves away from the trigger so that the spring 72 turns the plate 69 to tilt the switch 81 and thus cut off the welding current. The parts are reset when the lever 21 is released the extension 61 of the arm 59 engaging the stud 71 on the plate 69 and the rounded end 82 of the trigger wiping past the end of the screw 45. The mercury switch is in the primary circuit of a welding and annealing transformer which is also in series with the tapped primary of a choke the secondary of which contains the rheostat so as to vary the current. The welding and annealing transformer is provided with a tapping closed by the switch 14 so as to effect welding and annealing operations. In a modification the hand lever 21a, Fig. 10, operates a lever 109 against the action of a spring 111. The upper end of the lever engages a spring-pressed welding switch 110 and the lower end engages the movable work clamp 116 which is fixed on a movable rod 117 and is pressed towards the fixed clamp 128 by a spring 119. One end of the spring 119 is connected to a lever 121 which is engaged by the cam 125 on the rheostat to vary the tension of the spring when the current is varied. On pressing down the lever 21a the switch 110 is closed to put on the welding current. When the work softens an insulated knob 136 on the end of the rod 119 opens contacts 134, 131 to cut out the welding current. The annealing circuit is closed by the operator holding down a spring pressed button switch which is normally closed by the spring. Joints.-The burr may be removed from the weld by grinding.