Patent GB-596378-A (GB)
Title: Improvements in pilger mills
IPC: B21B21/00
Filed: 1944-10-18
Abstract: 596,378. Rolling tubes and bars. THURSTON, A. P. (Rockrite Processes, Inc.). Oct. 18, 1944, No. 20140. [Clase 83 (iv)] Rolling -mandrel and like carriages and carriage feeds; cold rolling.-A pilger mill with continuously rotating gapped rolls has the bar or mandrel carriage fed positively on both strokes by means independent of the roll pass. The feed mechanism also provides the acceleration to the rolling speed. The rollstand 20 is of I-section form, the web being cut away in part to form an opening in which four blocks 27, 28, 31 and 32 are located, blocks 27 and 28 carrying the shafts of the overhung rolls 21 and 22, and blocks 31 and 32 being formed as the axles of overhung backing rolls 23 and 24, all the rolls being mounted on spherical bearings. The rolls are adjusted vertically by two sets of wedges 55 and 56 acting against the blocks of the backing-rolls, the upper wedges being adjusted by hand wheels 65 through worm-gearing, after which this means is used for pre-loading the rolls. Side-plates 45 secure the backing-rolls axially, similar side-plates 48 carrying set-screws 47, securing the rolls. The rolls are bodily adjustable axially by screws 47, and individually by shims 77. Work guides are provided at 72 and are vertically adjustable by screws 74. The roll shafts are connected through reduction gearing at 244 and 243 to an electric motor 240. The same motor drives the feed and control mechanisms through gearing at 241 and 242, the main drive being transmitted through segmental gears at 227, one above and one below a rack 225, the gears rotating in opposite directions and engaging the rack at different times to reciprocate it. The rack is connected by a crank to shaft 82 to which two gear segments 110 are secured and are oscillated about the axis of shaft 82. Gear segments 110 mesh with bevel gears 111 secured to two shafts 105 disposed either side of the machine. For feeding the work to the rolls, drive is taken from one of the shafts 105 to a one-way clutch at 167 through gearing and crank and connecting rod, through a clutch 170, a reduction gear 171, shaft 174, to a rack and pinion 160, the rack extending to the feed mechanism housing 125 which is slidably mounted on a bed extending up to the roll-housing. Feed increments are thereby given to the housing to which workpieces are attached at 128. For the rolling operation, the tubes and mandrels are fed forward. and returned through the oscillatory motion of rack 225 transmitted to shafts 105. The feed housing 125 and mandrel housing 80 are fitted with gear segments meshing with bevel wheels on the shafts. Combined with each segment is a crank coupled to the respective slidably mounted tube and mandrel gripping members, ensuring that both mandrels and tubes are oscillated independently, but in unison and at a speed equal to the pitch circumferential speed of the die-rolls. The tubes and mandrels are also partially turned on each return stroke by gearing and chain drives through one-way clutches from shafts 105, so that uniformity of motion is maintained in all moving parts. A secondary driving unit is incorporated at 226 comprising a cross-head having vertical slots engaged by a rotating crank during the periods between segmental gears at 227 disengaging and re-engaging the rack 225, the cross-head being directly connected to the rack. A simple harmonic motion is thereby transmitted to the feed during the non-rolling periods of the forward stroke and reversing. A receiving unit 15 on the exit side of the roll-stand, is similarly provided with mechanism for reciprocating and turning the reduced tube projecting from the die-rolls, and in addition friction clamps are provided which are adjusted to allow the workpieces to be fed forward but retain them in position whilst new workpieces are being inserted for the follow on. During the time that the mill is stopped for this operation, clamps at 78 are operated by air pressure from 79 to grip the unfinished ends of the tubes. Tension springs anchored to the beds of the machine and acting against the oscillating cranks on the receiving feed, and mandrel housings absorb energy from the reciprocating parts during retardation and expend it during acceleration ; further, the pistons of two air cylinders 340 are connected to the cross-head 226. Adjustable stops on the mandrels are provided to act in conjunction with mandrel gripping members 96 to ensure correct relation between mandrels and tubes on insertion of new workpieces. In order to return the feed housing to the end of its bed, clutch 170 is disengaged by hand, upon which the circuit of an electric motor 177 is closed and press-button control enables the housing to be quickly returned at will, the motor operating the rack and pinion 160. Mandrel and work-supporting means 265 are mounted on a bed 266 supported by the roll-frame 20 and mandrel housing 80. These units are power-driven to lower and raise mechanical gripping means in support of overhung lengths of the members concerned, the motors being operated by pole reversing switches actuated by interference stops and trips located on the feed housing and bed of the machine.