GB648919A - Improvements in method of rolling out tubes in pilgrim rolling mills and equipment therefor - Google Patents

Abstract

648,919. Making tubes. SEE FABRIKS AKTIEBOLAG. Feb. 27, 1948, No. 6189. [Classes 83 (ii) and 83 (iv)] Rolling ; feeds for mandrel carriages.-In a pilger rolling-mill for cold-rolling tubes, of the kind in which a pair of conicallygrooved rollers is reciprocated along the axis of the work, the position of a tapered mandrel and length of stroke of the roller housing may be changed as the work is fed to obtain an internal or external taper. The taper may reduce and increase alternately as required and a work-piece comprising a string of similarly-tapered lengths may be produced. The roll housing 1 is reciprocated with a variable stroke by adjustment of the throw of a crank 2 and length of a connecting rod 3. The blank 7 held in a chuck 8 which rotates approximately 45 degrees between each stroke of the rolls 4 is fed a given distance for each stroke by a screw 9 actuated by a nut in a gear-box 10 geared to the reciprocating mechanism. The rolls 4 with conical grooves 5 carrying gear-wheels at both ends running on fixed racks roll the blank 7 over a conical mandrel 12 on a slidable rod 13 attached to an arm 14 on the end of a push-rod 15 which is pressed by a spring 17 normally to hold the mandrel in the forward position shown.. In this position a tube section of large constant internal diameter a, e is rolled and for rolling sections of small internal diameter c the mandrel is displaced to the left by the action of a stop 16 on the roll housing engaging a spring-loaded plunger 20 which is moved into line with the stop 16 and push-rod 15 by a solenoid-operated carriage 19. The mandrel and rod 15 remain locked to the left by a spring-loaded bolt 23 and the carriage is returned to its original position by a spring 25. Upon completion of the rolling of the portion c the bolt 23 is withdrawn by a solenoid 31 allowing the mandrel and rod 15 to return to the forward position. The carriage and bolt solenoids 28, 31 are each connected to contact bars 32, 33 carrying contact riders 34 with which the circuits are closed as required by contact springs 37 on a carrier 35 attached to the end of the tube blank. In one modification the mandrel-shifting mechanism is replaced by a screw-feed geared to the blank-feed so that the mandrel position is changed' uniformly at each reciprocation of the rolls to produce a continuous internal taper on the work. In a further modification the roll housing is reciprocated by a double-acting hydraulic cylinder and the mandrel may remain stationary while an external and internal taper is obtained by varying the forward limit of the roll stroke by an adjustable screw stop in one end of the cylinder. The stop may be screwed in or out automatically at each stroke of the rolls and in this case the nut for the blank-feed is rotated by a ratchet operated through a push-rod from a stop on the roll housing. Tubes of non- circular section may be produced by the latter form of apparatus if correspondingly-shaped mandrels, and roller grooves are used and the work is not rotated.