Patent GB-186314-A (GB)
Title: Improvements in and relating to electric arc welding apparatus
IPC: B23K9/12
Filed: 1922-08-10
Abstract: 186,314. British Thomson-Houston Co., Ltd., (Assignees of Glasser, C. E.). Sept. 23, 1921, [Convention date]. Heating by electricity.-In an are-welding apparatus of the type in which a fusible metal electrode is fed continuously to the work as consumed through a hand tool to which the current is supplied, the tool has a delivery member which is constructed so as to bend the electrode as it is moved therethrough in order to obtain electric contact between the member and the electrode, and to deliver the electrode to the work at a convenient angle. In the form shown in Fig. 1, the delivery member or nozzle 2, preferably of brass, through which the electrode wire is fed, is curved so as to bend the electrode and make electrical contact at 24. The nozzle, which is preferably provided with insulator 19 held in place by a metal cover 20 or which is coated with vitreous heat-resisting insulating material, is secured by a flanged nut 15 to the tubular metal body 7 of the tool, the nut being preferably covered with insulating material 17 held in place by a metal cover 18. The co-operating flanges of the nozzle and nut may be tapered. The angle of the electrode may be adjusted by loosening the nut and turning round the nozzle. The insulated flexible metal guide tube 5 through which the electrode wire is fed to the tool from the feed rolls as described in Specification 184,141, is secured in the body by a set screw 8 passing through an enlargement 9 on a clamp 10 surrounding the body, an insulating washer 11' preventing contact between the screw and body. Current is supplied to the body from a conductor 21 by a clamp 22 secured on the body, the clamp being preferably covered with insulation. The rest of the body up to the nut 15 is covered with insulation 12 held in place by a wire covering 13. The tool may be held in the hand directly or by a pistol grip 4 consisting of curved sheet metal having ears 25 pivoted to the clamp 10 and secured at the required angle by a wing nut 11. The grip is lined with insulation and is slotted to receive an insulator 28<1> in which contacts 32, 33 connected to the control wires 30. 31 are secured. A contact spring 34 is secured on the insulator at 35 and is operated by an insulated lever 27. A third control wire may be connected by the bolt 35 to the spring. In a modification, the guide tube is secured in the body by a pair of screws 8<1>, Fig. 2<a>, passing through insulating washers 11<1>, and carried by a metal block 9' separated from the clamp 10' by insulating washers 12' and from the bolt of the wing nut 11 by an insulating bush, in order to avoid the danger of shocks in case the set screw penetrates the insulation 6', Fig. 1. The ears 25<1> of the pistol grip are separated from the clamp 10<1> by washers 12". In a further modification, the nozzle 2, Fig. 6, is secured to the body 3 by a knurled nut 52 in close contact with a projecting insulating sleeve 62, which may be secured in position by the screw 66 of an insulated clamp 63, 65. In order to renew the nozzle the nut is screwed off by rotating the sleeve, the body, winch is screwed to a tapered block 55, being prevented from rotating by a screw 56. The body has a metal liner 57 which is separated therefrom by an insulating liner 58, the metal liner being flanged over a metal washer 60 resting against an insulating washer 59, and being separated from the block 55 by an insulating washer 61. A conductor 53 and control wires 74 are braided on the flexible guide tube as described in Specification 184,141, the conductor being secured to the block 55 by a tapered nut 54. The conductor and flexible guide tube are fixed by a clamp 69 to the slitted end of a tubular member 67, which has over part of its length an insulating lining 68 and is secured by screws 72 to the clamp 63. The pistol grip, which is pivoted to the ears 65 of the clamp 63 contains an insulating block 91 provided with saw cuts, Fig. 7, to receive the flat conductors 84, 85 of the contacts 82, 83, into engagement with which the contact spring 81 is pressed by an insulating hand lever. The conductors 84, 85 are clamped by the nut 73 against contacts 78 secured to a curved insulating block 75, Fig. 8, which is rigidly fixed against the tool by the nut 73. One of the control wires is secured by a screw 79 to the contact 77 and is engaged by the curved upper end of the spring 81, and the other wires pass through holes 80 in the block 75 and are secured to the contacts 78. The bolt of the nut 73 has an insulating bush and insulating washers 87, 88 separate the contacts from the side plates 89, 90 of the pistol grip. This construction affords a sliding engagement between the contacts on the pistol grip and those on the block 75 and angular adjustment of the pistol grip is thus effected without bending the control wires. Fig. 4 shows an arc welding system in which the electrode wire is fed through a flexible guide tube 40' and through a tool of the kind shown in Fig. 1 by rolls 39<1> driven by a motor at a speed in accordance with the voltage at the arc to keep the length of the arc constant. The welding current may be supplied from the terminals 42, 43 through a resistance 44 from a balancer set as described in Specification 133,439 or from a generator as described in Specification 159,374, [Class 35, Dynamo-electric generators &c.]. The field 41 of the motor is supplied from any source, and the motor armature 40 is connected to the terminals through a switch 47, which is opened by its actuating coil 48 when the welding circuit is open, so as to keep the motor out of action. To perform the welding operation the spring contact 34 is first engaged with the contact 32 so as to energize the coil 48 and is then engaged with the contact 33 so as to energize the coil 50 for closing the welding switch 49. When the electrode is touched to the work and withdrawn to strike the are, the drop in voltage weakens the coil 48 and allows the switch 47 to make contact to put in the motor. In order to enable the motor to be operative when the welding circuit is open, for the purpose of feeding in a new electrode, a shunt circuit through a resistance 47<11> is provided round the switch 47 and is completed by a switch 47<1>. The switch 47' may be left permanently closed, the resistance 47" being adjusted to keep the speed of the motor low.