Patent GB-209180-A (GB)
Title: Improvements in electric welding apparatus
IPC: B23K9/12
Filed: 1922-10-04
Abstract: 209,180. Cutler, A. E., and Marsden, P. A. Oct. 4, 1922. Uniting by fusion.-An electric arcwelding machine is automatically traversed over the work by a geared wheel, and the electrode is automatically fed by rollers, by means of an electric motor, the armature of which is connected across the arc and the field windings in shunt with the welding circuit, so that the rate of feed of the electrode and the rate of travel of the machine vary in synchronism directly with the variation in the arc voltage. The machine consists of a housing 30 mounted on adjustable wheels, one of which 33 is driven by worm gear 34, 35, spur gear 37, 38, 39, bevel gear 41, 42, and one of a series of concentric crown wheels 46, from a slidable pinion 47 on a shaft 57, which is driven by gearing 58 from an electric motor carried in the housing. The pinion 47 is moved on its shaft by a fork on a lever 49 connected to a handoperated sliding rod 53 furnished with a lock. The motor is cooled by a fan 65 which draws air through the casing and forces it through perforations in the cover 31. The electrode 123 is drawn from a drum mounted on the housing and fed by interchangeable grooved and serrated rollers 119, 100, carried by a head 93 secured to a sleeve 75, which is angularly adjustable on an insulated bracket 70 concentric with the shaft 57. The tang end 154 of the shaft 99 of the feed roller 100, Fig. 9, engages a spring-pressed contact block 155 mounted in an.insulated bracket 156 which is electrically connected thereto bv a wire 156<1>. The feed rolls are driven from a shaft 73 in alignment with and separated by an insulated coupling 74 from the shaft 57. A worm 94 on the shaft 73 gears with worm wheel 95 on shaft 96, which is connected by gear 97, 98 to the shaft of the feed roll 100, which is connected to the shaft 117 of the feed roll 119 by gearing 100, 102, 104, 120. The shaft 117 is carried by a pair of levers on the shaft 105 so that it may be guided in a curved slot in the head 93. One of the levers 106 is pressed forward, to regulate the grip of the rolls, by a spring 111 and segmental bearing block 113 mounted on a screw spindle 109, the tension being adjusted by a nut 114 and interchangeable sleeve 112. The electrode passes through a guide tube 125 with spherical seating 126 for alignment purposes, which is secured by a nut 128 with screwed mouthpiece 135 to a nozzle 127 furnished with a deflector 133. The tube is connected electrically to the head 93 by a wire 188, contact between the electrode and tube occurring at the lower end thereof so that the main welding current only passes through the lower end of the electrode. The head 93 is roughly adjusted angularly and is then secured by a split band 77, which carries a pair of bearings for a tangent screw for effecting a fine adjustment. The screw passes through a block loosely mounted on a split strap 83, which carries a bracket 87 containing a slotted bearing block 88 so that the head may be oscillated across the joint by a crank pin 89 projecting eccentrically from a disc 90 screwed into an eccentric recess in the head 91 of the shaft 40 and locked by a spring- pin 92. The nozzle may be oscillated longitudinally of the joint on removal of the cover 134. For this purpose it is pivoted at 131, Fig. 12, in the head 93 and connected by pintles 137 on an adjustable collar 136 with a slotted forked arm 140, which is connected by a bell-crank 142 to the arm of an eccentric strap 147. The eccentric 148 is loosely mounted on the shaft 96 and is attached to a gear wheel, which is driven from the wheel 97 by gearing on a counter shaft. The tendency of the arc to be deflected by magnetic reluctance at the joint away from the direction of traverse may be counteracted by securing to the pivoted cover 159 a magnet, preferably an electromagnet 163 provided with a pair of adjustable pole-pieces 165 one at each side of the joint. Adjustable resistance strips 170 for the main welding circuit are secured to the cover and a shield 189 is provided for protecting the rear of the machine from the arc. When welding on flat surfaces one of the wheels may be grooved to engage a guide-rail. When making lap welds on pipes externally the machine is arranged as shown in Fig. 22, with one or more of the wheels 32 running along the joint. For making internal welds a bracket is laterally secured to the top of the machine and carries a wheel to rest against the side of the pipe. The main welding circuit, Fig. 26, from the negative terminal 208 contains switch 202, adjustable rheostat 201, reactance 200, ammeter 193, contactor 242, adjustable shunt 170 for the field 170<1> of the motor 60, the binding- post 173 being connected by a cable 253 either to the magnet 163 or direct to the head 93, and thence is connected to the tube 125 and electrode, across the arc to the work 203 and positive terminal 204. To effect a weld, a striking rod 206 is first placed between the electrode and the work and a push-button switch 181 then pressed upwards so as to complete a circuit from negative 208, through wires 210, 214, contact 207, wires 216, 218, coil 219, wires 220. 221, resistance 222 of current limiter 199, wires 223, 224, 205 to positive terminal. Contacts 227 and 259 of current limiter are thus closed and a circuit is completed through wires 210, 214, contact 207, wires 216, 218, 228, 229, coil 196 of a slow-acting relay or relay with dash-pot, wires 230, 232, 233 to roll 100 and thence through electrode 123 and rod 206 to the positive terminal. The armature 236 is thus closed and a circuit completed through wires 210, 238, adjustable resistance 194, wire 239, coil 195 of contactor 242, wires 240, 241, 224, 205. The contactor 242 being now closed to complete the welding circuit, the push-button is released and the rod 206 removed so as to strike the arc. The current limiter is maintained closed by current passing through the coil 247 when the contacts 254, 255 are closed and the motor 60 is rotated by current passing from the arc through armature circuit, wire 256, contacts 255, 254, wires 257, 221, contact 259, wires 260, 223, 224, 205. The coil 196 remains energized by current passing from the arc through wires 233, 232, 230, coil 196, wire 229, contacts 227, wires 228, 218, 216, switch 181, contact 254, wires 257, 221, contact 259, wires 223, 224, 205. The armature being connected in shunt with the arc, and the field in shunt with the main current, the motor is caused to maintain a constant length of arc. If the arc lengthens or the fusing rate increases, the motor is accelerated, and vice versa. If the arc ruptures, the current limiter 199 is de-energized and the current thus cut off, and if the electrode freezes on to the work, the relay coil 196 is de-energized due to loss of arc voltage and the current thus cut off. The machine may be stopped by pushing the switch 181 to neutral position or by inserting striking rod 206 between the electrode and work. According to the Provisional Specification, on completion of the welding circuit an electromagnetic switch with condenser to reduce arcing is energized to close the armature circuit and to maintain the contactor closed when the hand-operated controlling switch is released. The variable-speed gear consists of friction discs. Flux may be applied to the electrode prior to placing in the machine or fed to the weld in liquid or powder form down the nozzle &c.