Patent GB-710893-A (GB)
Title: Method of manufacturing seamless tubes and rolling mill therefor
IPC: B21B19/06
Filed: 1951-11-13
Abstract: 710,893. Rolling tubes. CALMES, A. Nov. 13, 1951 [Nov. 20, 1950], No. 26585/51. Class 83 (4) Skew-rolling.-A method of manufacturing seamless tubes and pipes by cross rolling between two or more outer rolls and an inner mandrel consists in reducing the inner and outer diameter of a tubular blank between converging rolling walls of a pair of rolls arranged with inclined axes lying in two parallel planes, reducing the wall thickness of the blank over an ogival portion of the mandrel and smoothing said blank between parallel walls of said rolls following said converging walls and a cylindrical portion of the mandrel, the said mandrel portions being carried by a bar arranged within the inner bore of the blank. Skew rolls 1 comprise a section A for feeding the tubular blank S, a section B for reducing the blank diameters unsupported by the mandrel and a rolling section C. A bar 2 carries a mandrel 3 having an ogival inlet portion and a cylindrical portion 4 and an extension 5 on the bar carries a roll 6. The blank which is rolled to a tube T is centrally held by stationary guides 8 and 9 formed with a shaped step 10 whose inclination, e.g. 15 degrees to 22 degrees, varies with the inclination of the rolls. In operation, the blank is fed with a helical rotation by the section A of the rolls and the section B reduces the outer and bore diameter below the ultimate size of the tube T unsupported to correct any wall irregularities. Rolling commences as the blank reaches the region y, Fig. 8, when it is rolled between section C of the first roll 1 and the ogival portion 3 of the mandrel. The blank is elongated and made elliptical in cross section so that it engages the top guide 9 and after half a turn the blank undergoes at Z a further rolling between the second roll and the mandrel portion 4 whereon the tube reaches its ultimate thickness and is gradually formed into cylindrical shape by the stationary guides. The inner roll 6 smooths and accurately shapes the tube. The rate of feed of the blank effected by section C of the rolls is less than that effected by section B so that the blank is braked between sections B and C. The shaped step 10 on the guides and conveys and adjusts the feeding rate of the blank over the section x, y preceding rolling. A rolling mill for carrying out the invention comprises a housing 11 for the rolls 1 which are driven by spindles 12 and wobblers 13 from a gear box 14 actuated by a motor 15. Two sets of extractor cylinders 18, 19, a roller way 20 and heat insulated troughs 16, 17, serve for the outlet of the roller tubes. The inlet comprises a guide trough 21, a set of inclined feeding rollers 22 for spiral rotation of the blank and a carriage 23 guided on a frame 24 said carriage carrying the mandrel bar 2. The carriage 23 is actuated by a rod 27 and piston 26 movable in a pneumatic cylinder 25 said piston also acting as a brake. The carriage also carries a box 28 capable of lengthwise adjustment by means of a screwthreaded bush 29. The box encloses a sleeve 30 rotating on bearings and carrying the bar 2, gears 31 connected to a coupling 32, 33 and a helically grooved rod 34 reaching within a cradle 46 slidable on guides having end abutments 47, 48. The bar 2 carries the mandrel 3 through a clutch 35 and the bar has conduits 36, 37 for cooling water and lubricating powder respectively. The water conduit 36 communicates through an injector 40 and a conduit 38 with a feeding tap 39 and through a chamber 41 in the box 28 with a discharge conduit 42. The lubricating powder conduit 37 is connected with a reservoir 43 and an air supply pipe and opens through ports 45 into the region between the blank and the mandrel. In operation, when the carriage 23 is moved forwardly for starting the rolling the helically grooved rod 34 also moves forward and carries the cradle 46 which stops as it abuts the abutments 47 while the carriage and rod move further to the position shown in Fig. 8. After rolling, the mandrel clutch 35 and the coupling 32-33, which has a single spring-loaded piston in one member co-operating with a groove in the other, is orientated in any position. As the carriage returns, the rod 34 pressed by a spring 49 engages the coupling 32-33 and then moves back with the carriage and cradle 46 until the latter abuts the abutment 48 and causes the rod 34 to rotate one full turn thereby rotating the rod 2 by means of the gears 31 and setting the clutch 35 in the right position for changing the mandrel 3.