Patent GB-269273-A (GB)
Title: Improvements in the manufacture of butt and lap welded tubes
IPC: B21C37/08
Filed: 1926-02-02
Abstract: 269,273. Chisholm, D. W. Feb. 2, 1926. Tubes. - Welded tubes are made from strips drawn from a furnace through a skelping-bell, in passing through which the edges are further heated by a current of oxygen, and a pair of closing rolls. The bell is in two parts, the upper part being raised together with the upper roll to permit the passage of the tongs which are then hooked on to a draw bench chain. The skelp is supported by a special mandrel and guide extending right up to the roll pass. Automatic control by the draw chain may be provided for the opening and closing mechanism and for the oxygen supply valve. The machine is mounted to run on a track across the front of the furnace to facilitate the rapid handling of a succession of strips, power traversing mechanism being provided. The machine is provided with an operator's platform F, Figs. 3 and 4, alongside the draw chain E the slack side of which passes over supporting rolls c, Figs. 1 and 2. Controls for the various motors &c. are mounted on or adjacent to the platform. The chain is driven by a motor G through a flexible coupling e and gear train g. The machine is supported on a track by four wheels B, two of which are geared to a shaft n geared to a motor J. A third motor 44 drives a pump for circulating cooling water in tanks which together with a guard plate lined with asbestos screen the machine and operators from the heat of the furnace. The parts 5, 6 of the skelping-die are either integral with the upper and lower roll housings 1<a>, 2b or they may be attached thereto either directly or through an intermediate hinge pin. Mandrels 27, 29 constructed as described in Specification 263,323 are provided. The lower roller is geared to a motor 56 and a gear on the upper roll shaft meshes with a corresponding gear on the lower roll when the pass is closed. Tandem hydraulic cylinders open and close the pass under the control of a pair of valves with handles so linked that when pressure-fluid is admitted to one cylinder it is exhausted from the other. The exhaust water is discharged on to the skelping-bell for cooling. The housings are shaped to interengage in the closed position to prevent relative movement laterally. Oxygen is stored in a series of cylinders mounted in a rack 46 and connectable bv handcontrolled valves with the supply pipe leading to the mandrel. A further valve is controlled bv tappets on the movable housing to cut off the supply when the upper roll is raised and restored when the pass is closed again. The rolls are preferably provided with ball bearings that on one side being allowed to float to provide for expansion of the roll. Grooves packed with asbestos may be provided to exclude scale from the bearings. In a modification the upper roll is driven from the lower by the two stage chain drive shown in Fig. 15, tension adjustment being provided at 76, so that the roll revolves continuously. The upper part of the skelping-die is formed as a recess 80 on the face of a square block pivoted at 77, one recess being provided on each face and the block being indented each time the roll is raised and returned by pins 84<a> co-operating with a step 85 and cam surface 86 on a lever pivoted at 82 and controlled by a weight 83 and guide and stop 81<a>. In this construction the mandrel 29 is pressed on the skelp by a strap 87 pivoted to a lever 88 controlled by a wedge 92 and stop screw 91. Instead of being carried by the bar 26 the mandrel 27 is supported by the wall of the lower roll housing, and oxygen is fed to the mandrel by a pipe 97 and also bv a pipe 97<a> to a point in advance of the guide 32 and close to the roll pass. In a further modification automatic control gear for the pass and the gas supply is provided. Assuming the pass to be open as shown in Fig. 17, a cup-shaped tappet 111 on the draw-chain, which serves to engage the tangs, actuates a crank 109 connected by other cranks and links to a valve arm 102 and moves it to the position shown in dotted lines in Fig. 17 admitting pressure to the lower cylinder 14 and causing the pass to close. The upper and smaller cylinder 13 is always open to pressure and opens the pass when the cylinder 14 is exhausted. As the pass closes a tappet 139 engages the arm 102 and returns it gradually to the neutral position. Further as the pass closes a tappet 100 engages a spring-closed check valve 99 to admit oxygen to the pipes 97, 97a. A finger 132 controlled by a spring 133 is engaged by the tappet 111 and locked to engage a trip mechanism with a lever on the shaft carrying the crank 109. If a tube has not been drawn through the rolls the spring returns the finger and causes the valve arm 102 to be actuated to exhaust the cylinder 14 and open the pass. A tappet 140 returns the arm at the end of the up-stroke. If, however, a tube is present the trip mechanism is locked until the end of the tube passes the finger 132.