GB963778A - Improvements in or relating to method and apparatus for controlling the successive positions of a movable part - Google Patents

Abstract

963,778. Rolling metals. ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE CHARLEROI (ACEC). July 30, 1962 [July 31, 1961], No. 29143/62. Heading B3M. [Also in Division G4] The reversible rolling mill control system of Specification 953,561 is modified in that the device for changing the number of passes programmed by the analogue computer comprises a function generator which produces a voltage which is dependent on variable parameters such as the width and temperature of the ingot being rolled. The initial thickness of the ingot is set by operating one of buttone 0<SP>11</SP>-9<SP>11</SP> and the desired final size is entered by operating one of buttons 333. The system then operates to position the rolls automatically for a succession of passes in such a way that the reduction in thickness produced by each pass, including the final pass, is substantially the same, taking into account variations in parameters which may occur during the rolling process. The operation in a specific example is as follows. If buttons corresponding to initial and final thicknesses of 900 mm. and 200 mm. are operated, relays 9‹ and 322 are energized to produce voltages V p and Vq of, say, 900 v. and 200 v. from resistance networks 202, 330, and control unit T positions the rolls 900 mm. apart. The function generator S produces a voltage corresponding to a maximum permissible reduction of 120 mm. from the initial thickness of 900 mm. by means of resistance network 205, and this voltage is further modified by resistance chain 206 and variable resistance 340 to account for the width of the ingot and its temperature respectively, the resistance selected in each case being controlled manually or automatically. The maximum permissible reduction is thereby reduced to 105 mm. say. Initially Vp - Vq is applied across resistor 271, and amplifier 216 adjusts stepping switch 219 until the voltage drop across resistor 217 is less than or equal to the output Vs of function generator S representing the maximum permissible reduction. The number of passes programmed by the analogue computer comprising resistance chain 218 is equal to the number of steps performed by switch 219, but this number may subsequently be altered as the rolling process proceeds. The voltage now appearing across conductors 213, 243 represents the position of the rolls for the first intermediate pass, e.g. 800 mm., and switch 210 is driven by amplifier 214 until the corresponding tapping 68 on resistance chain 209 is reached. On completion of the initial pass, switch 240 opens and switch 241 closes, whereby switch arm 211 energizes relay 8‹, and the process is repeated, control unit T driving the rolls to the position required for the first intermediate pass, and function generator S providing a fresh reference voltage representing the maximum permissible reduction for the second intermediate pass in dependence on the thickness, width and temperature of the ingot as before. Switch 219 may or may not be adjusted at this stage, depending on the inputs to amplifier 216, and therefore the number of passes to be performed is continually subject to revision. The final pass is made with switch 219 on contact a and Vp - Vq less than or equal to Vs. Other corrections, e.g. for zeroizing effects of wear or play and for edge rolling between grooves may be introduced by means of potentiometer 222 and by source 221, respectively. Two identical systems may be used to control rolling of the two axes of an ingot in a slabbing mill, and the speed of the vertical rolls may additionally be controlled in accordance with the ratio of the exit thickness to the entry thickness of which the voltages Vp - Va and Vp are measures. Vs may also be varied in accordance with further parameters such as thr torque supplied by the motor driving the rolls, the rolling stress and the quality of steel being rolled. Specification 758,765 also is referred to.