FIELD: machine engineering and metallurgical industry branches, namely manufacture and exploitation of cogging rolling mills. SUBSTANCE: locking device is mounted on upper end of nut around screw of screw-down mechanism and it is in the form of supporting annular disc with guiding dowels having stops. On supporting disc with dowels and preliminarily compressed plate springs movable stoppers are mounted. Movable stoppers have upper cone surface and they are bored by diameter equal to outer diameter of screw. Thrust ring with skirt, inner cone surface and flat upper surface is placed from upwards onto stoppers forced by means of springs to rear position in such a way that to form gap equal to 2mm between stoppers and outer surface of turns. At working overbalancing effort occurs. Said effort acting upon screw and nut is caused by resistance of springs designed for large efforts and friction forces in wedge joints of stoppers and thrust ring but it cannot compress locking device. Positions of nut and screw of screw-down mechanism remain the same. At biting strip between rolls large rolling effort overcomes action of springs and friction forces in wedge joint of stoppers and thrust ring, that is why locking device is compressed through screw and nut, stopper shifts to screw of screw-down mechanism for arresting it. In order to provide small vertical movement of nut it is secured in seat of housing with use of spring. After termination strip rolling process, rolling effort disappears, stoppers by action of springs are shifted backwards and screw becomes free. EFFECT: prevention of release of screw of screw-down mechanism at biting strip between rolls. 6 dwg
