Patent GB-930906-A (GB)
Title: Hydraulic arrangement for adjusting the spacing of the rolls of rolling mills and compensating mill spring
IPC: B21B37/64
Filed: 1959-10-27
Abstract: 930,906. Rolling. INSTITUT DE RECHERCHES DE LA SIDERURGIE. Oct. 27, 1959 [Oct. 31, 1958; Nov. 10, 1958], No. 36352/59. Class 83 (4). Means for adjusting the pass and compensating for mill spring including a jack, the total height of which increases with the pressure applied thereto in accordance with the spacing of the rolls, and means for controlling the jack comprising two elements, the positions of which depend on the pressure within the jack and on the location of the piston in the jack, the two elements being included in a control circuit for the pressure control of the jack is characterized in that the control means for the jack include two identical systems adapted to be active respectively for idle operation of the mill and for operation under load, means being provided to allow automatic transition from one system to the other. The control arrangement is first described with reference to a single system wherein the jack 1, 2 is fed with liquid through an electrically-actuated valve 4 by a pump 6, the flow to the jack being controlled by a circuit containing a switch, one contact 9 of which is rigidly attached to the piston 1 of the jack while the other contact 10 is resiliently connected to a rod 12 rigid with a transverse spring 13, the latter being subjected to bending by a plunger 14 responsive to the pressure in the jack. The jack may be inserted between the screw-down of the mill. The pressure is normally maintained constant by the continuous make- and-break of the switch in the control circuit, but if during entry of the work into the mill or during rolling the mill-stress increases, in the latter case through increase in the strip thickness or hardness, the increased pressure in the jack causes a deflection of the spring 13 by the plunger 14 so that the position of the switch 9-10 is altered relative to the jack-casing 2 which results in an increased overall height of the jack equal to h=ho+KF, where ho is the height of the jack before the application of any stress F and K is a coefficient depending on the stiffness of the spring 13. By suitably choosing the value of the coefficient K the increase in height of the jack can be made to precisely compensate for the elastic deformation of the kinematic chain of the mill stand resulting in a constant output thickness of the strip. In an arrangement for stabilizing the height of the jack, a winding 19, Fig. 2, is attached to the piston 1 and is connected through an amplifier to the valve 4 and moves parallel to a vertically arranged composite rod, the upper half 20 of which is non-magnetic while the lower half 21 is ferro-magnetic. When the winding 19 is horizontally in register with the non-magnetic portion of the rod, the liquid from the pump passes to the jack whereas with the winding 19 registered with the magnetic portion liquid is discharged from the jack to the sump. In another modification a photo-cell control may be used. As shown in Fig. 3, continuous and gradual pressure control is provided to the jack by an hydraulic distributer 23-24. The piston movement of which is controlled by varying pressure on an elastic diaphragm 27, the pressure being determined by the degree of throttling applied to a constant supply of compressed air escaping from a nozzle 25 by a blade 26 connected to the spring 13. In hotrolling mills the work enters the mill at high speed and in order to obtain a very quick adjustment two identical control systems are provided according to the invention. Two vertically-spaced windings 19a, 19b, Figs. 7 and 9 (not shown), may be used, the winding 19a acts as one element of the stabilizing switch when the mill is idle, but during the passage of the material the winding 19b acts as the corresponding element of the switch. With correct adjustment of the vertical distance between the windings the junction of the two portions of the composite rod will fall opposite the winding 19a due to the deflection of the spring 13 on entry of the material between the rolls. Means are provided for automatically moving the coils into or out of the operating circuit of the valve 4 as required. In addition the spacing of the coils 19a and 19b may be automatically controlled by a pair of levers 46, 47, Fig. 12, pivoted together at 48 and connected one to each coil. The other end of the lever 47 is pivoted to a fixed tubular member 44 beneath which the lever 46 projects to be acted upon by a rod 45 secured to the plunger 14.