Patent GB-552366-A (GB)
Title: Improvements in and relating to electric welding apparatus
IPC: B23K11/08
Filed: 1941-06-24
Abstract: 552,366. Welding aircraft wings &c. BRIGGS MANUFACTURING CO. June 24, 1941, No. 7933. Convention date, Jan. 4. [Classes 83 (ii) and 83 (iv)] In an electric welding apparatus, particularly for welding the flanged channel-shaped reinforcing ribs to the skin of aluminium aircraft wings, the work is mounted on a carriage moved step by step between a pair of electrodes which are operated during periods of rest of the carriage, the work being carried by supports which are shiftable transversely relatively to the carriage to register different portions of the work with the electrodes. The wings which are of taper form may thus be adjusted so that the ribs are in turn in the longitudinal centre line of the carriage. The wings 15 are secured at each end by clamps 31 to a pair of cradles 25, 26 lined with insulation and resting on pairs of shaped supports 27 on a carriage 19, which is provided with guide rollers 22, 23 and is traversed along tracks 21, 20 o na table so that the work passes between a pair of welding electrodes 73, 72. The cradle 26 is provided with a strip 29 for spacing the channelled ribs 16 to be welded to the wing and the cradle 25 has a number of clamps 30 for securing the opposite ends of the ribs thereto. The cradles are provided with pairs of holes 37 situated in alignment with the flanges of the ribs, the distance apart of the pairs of holes in the cradles being different in accordance with the taper of the wings. The cradles are laterally adjusted by hand and are connected to the carriage by a pair of pins 38, 40 passing through holes in the cradles and holes in U-shaped brackets 33, 34 in the carriage in the longitudinal centre line of the carriage. Intermediate supports 32 for the wings are also provided. The carriage may be traversed by hand to effect pre liminary welds and is then traversed automatically to effect the main welding operations. The carriage is provided with a toothed rack 51 which is adjustable by slots 54 and screws 56 to adjust the position of the welds. The spacing between the teeth on the rack may be twice the distance between adjacent welds so that each series of welds is effected at two stages in order that the metal may cool between adjacent welds. The pawl 48 which is provided with teeth 49, 50 held in contact by a spring 59 with the rack according to the direction of traverse is carried by a lever 44 operated from a fluid actuated piston 43 supplied with pressure from a pipe 80 through a four-way valve 81 and a pair of three-way reversing valves 82, 83. The valves 82, 83 are reversed by hand so as to reverse the direction of the power stroke of the piston 43 according to the direction of traverse of the carriage. The valve 81 is operated by a solenoid 92 against the action of a spring 94 so as to control each forward and return stroke of the piston 43. The fluid-operated welding apparatus which is used is described in Specification 547,110. The throttle valve is controlled by a solenoid 158 in circuit with a hand switch 161 during preliminary welding and an automatic-switch 162 during automatic welding, the switches 161 and 162 being in a circuit including the low voltage side of a transformer c<SP>1</SP> connected with the mains side of a switch 140. In the automatic operation of the apparatus when the electrode 73 rises from the work after effecting a weld a rod carried thereby closes momentarily a spring-opened switch 96 so as to energize a solenoid 104 which closes a switch 106 to energize a circuit through the solenoid 92 to effect the power stroke of the piston 43. The arm 109 of the switch 106 is held closed by a latch 108. Closing of the switch 96 also causes the solenoid 110 to be energized so closing the switch 112 to energize a solenoid 66 which raises a locking dog 62 from contact with the rack 51 to allow the traverse of the carriage by the piston 43. The switch 112 is held closed by a latch 115. During the power stroke of the piston 43 pressure is also admitted to the cylinder 122 to operate a spring-returned piston 124, which reciprocates a slide 125 provided with a cam 126 which in turn closes spring- opened switch 118, 121. The switch 118 closes a circuit containing a solenoid 116 for removing the latch 115 to open the switch 112 to allow the rack 51 to be engaged by the locking dog. The switch 121 closes a circuit containing a solenoid 119 for removing the latch 108 to open the circuit containing the solenoid 92 so as to reverse the valve 81 and thus effect a return of the piston 43. Thereupon another weld is effected. In order that the electrodes may be rendered inoperative when they are over spots welded during the preliminary welding operation a corresponding number of switches 146 in the circuit containing a relay B controlling the primary circuit 761 of the welding transformer are arranged to be opened by a projection on the carriage 19 to prevent closing of the welding circuit. In effecting preliminary welding by traversing the carriage by hand after first opening the switch 140, the carriage is provided over each spot to be welded with a recessed bracket 141 which brackets are in turn brought over a vertical slide 144 mounted on the table 18. The slide carries a pin 143 which is pushed into the recess and clamped therein prior to effecting each weld. During preliminary welding the switches 146 are shunted out of the welding circuit by closing a switch 150. Only after all the ribs are preliminary welded to the wings is the automatic welding effected.