GB1316580A - Jacking devices - Google Patents

Abstract

1316580 Rolling GEORGE JONES Ltd 8 Jan 1971 [10 Oct 1969] 49848/69 Heading B3M [Also in Division B8] A jacking device comprises a fluid-operated jack assisted by a mechanical jack operable in parallel, and control means for maintaining the force exerted by the mechanical jack within predetermined limits by varying the force exerted by the fluid-operated jack. The device may be used in tension or compression and applied to horizontal, vertical or universal twohigh, three-high or four-high rolling-mill stands; it may be a spacer between work-roll or supportroll chocks, or a pre-stressing device exerting pressure on the roll chocks in opposition to rollseparating forces. The jacks may be integrated or separate, and two screw-jacks may be association with a single hydraulic jack. As applied to spacing the support rolls 14, 15, Fig. 1, in a four-high rolling mill stand, a pair of integrated jacks is used between the chocks 16, 17 in each frame 18. Each jack unit has a balancing ram 43 in a cylinder 32 and a screwthreaded jack shaft 37 engaging a nut 36. A thrust bearing 35 supports the nut on a load cell 34, and the nuts are driven, through gearing 38, 42, by hydraulic motors 50a, 50b. The frames are pre-stressed by hydraulic rams 21, 23 acting against the chocks 16, 17. Admission of fluid pressure below rams 43 relieves the screw of some of the load that would otherwise be transmitted through the nut 36, bearing 35 and cell 34 to the frame 33. The other jack unit in the frame has a dummy load cell, and chocks 12, 13 for the work rolls 10, 11 are separated by springs and hydraulic rams (not shown). The four balancing rams 43 are connected to an hydraulic pump through a control valve forming part of an electric control circuit including the two load cells 34. A separate pump and control valve is used for the rams 21, 23. Rollers 44, 47 on rails 45, 46 facilitate dismounting of the chocks. After pre-stressing by means of the rams 21, 23, the screw elements are operated and at the same time the balancing rams 43, so as to relieve the screw elements. During a rolling operation, a reduction of load on the screw elements is sensed by the load cells 34 and the control circuit operates automatically to reduce the fluid pressure on the balancing rams 43 and restore the loading on the screw elements. To compensate for deflection of the rolls and their bearings, a pressure transducer senses the pressure on the balancing rams 43 and the transducer readings are applied to the control circuit to determine the change required in chock-spacing, the screw elements being adjusted automatically to maintain constant rollgap. Automatic gauge control may also be provided by an electric thickness gauge monitoring the finished strip.