Patent GB-790048-A (GB)
Title: Improvements in the welding together of pipes
IPC: B23K9/035
Filed: 1954-09-11
Abstract: 790,048. Welding by fusion. HANDLEY, J. and UNION TOTALISATOR CO., Ltd., Dec. 9, 1955 [Sept. 11, 1954; Oct. 28, 1954; Dec. 23, 1954; Feb. 11, 1955], Nos. 26348/54, 31088/54, 37131/54 and 4084/54. Class 83 (4). [Also in Group XXIX] In a method of butt-welding pipes in which an arc and/or flame is rotated around the pipes or the pipes are rotated, a backing ring loosely fitting within the pipes is progressively pressed against that portion of the joint which is being welded. A backing device for insertion in the pipes 10, 11 to be welded consists of a frame 12 carrying fixed legs 13, 14 and a compressed air jack 24 by means of which the device is secured within one of the pipes. A sleeve 39 rotatably mounted on a spigot 38 secured to the frame 12 carries a drum 40 and a compressed air cylinder 44 containing a piston to which is loosely connected a block 58. A copper backing ring 70 having a grooved outer face is formed with a dovetail which is a sliding fit in a pad 64 mounted in the block 58 so as to be angularly movable. A projection 113 on the pad 64 engages a projection 112 on the drum 40 to hold the ring 70 in an oblique position to facilitate removal and insertion of the device. Compressed air supplied to the cylinder 44 forces the ring 70 into contact with the uppermost portion of the joint which is immediately beneath a welding head, the ring being free to tilt to allow for say slight variations in the diameters of the pipes 10, 11. During welding the pipes are continuously rotated. As soon as the pad 64 moves from the position vertically above the spigot 38 a lever 104 suspended from a pivot on the drum 40 moves relatively to the drum to open a valve secured on the drum 40 to pass compressed air to a rotary motor 28 secured to the frame 12 which rotates the drum to return the pad to its vertical position. An inert gas such as argon may be fed to the interior of the pipes e.g. through passages terminating in nozzles in the block 58. In a modification, the pipes are held stationary and the welding head is rotated around them. The welding head and the block 58 may be rotated by electric motors operated in synchronism. Alternatively the welding head may be rotated by a continuously running hydraulic or pneumatic motor which by means of a cam-controlled valve intermittently supplies pressure fluid to a cylinder which operates a pawl and ratchet device to intermittently rotate the block 58. The second Provisional Specification describes a device to which the backing member is a shoe 1, Fig. 1 (Prov.), e.g. of copper, carbon or a ceramic, which is rotated relatively to and in sliding contact with the pipes by a motor driven in synchronism with a motor serving to rotate the pipes or the welding head. The device is secured in the pipes by legs movable radially by a toggle mechanism operated by rotation of a flexible cable. The shoe 1 is pivotally mounted in a box 6 rotated around a guide ring 2 by a pin 20 on a gear driven by the motor. Springs urge the shoe towards the pipes. Argon is supplied to the box 6 through a pipe 11. The first Provisional Specification describes a similar device in which the shoe is directly guided by the ring 2, and there is no provision for supplying argon. The shoe may be driven by a clockwork motor which in the case when the pipes are rotated is controlled by a hanging lever which when the shoe moves from the uppermost position releases the escapement of the motor to rotate the shoe. The third Provisional Specification' describes a device somewhat similar to that of the second Provisional Specification in which a backing ring is located in a groove in the shoe and pressed against the pipes. The backing ring may be coated with a flux.