| 摘要 |
1,155,551. Automatic control of speed. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. March 20, 1967 [March 25, 1966], No. 13415/66. Heading G3R. In material processing apparatus having at least three rotary stages (a tube stretch mill), the speed ratio of adjacent stages is kept constant by control means responsive to any error detected by a comparator of speed representative pulses which is switched between pairs of stages. Each stage is controlled by a retroactive system comprising tachogenerators G, the voltage of which is modified by course control rheostat CP N and a fine control FP N and applied to a motor field operational amplifier OA N for comparison with a reference voltage D.C. and a voltage SVP, different for each stand, by which speed ratios are established. Each stage also has a pulse generator PG N connectible to the comparison equipment FC, of which there may be only one for the mill. This is automatically connected sequentially to adjacent stages along the mill and comprises frequency multipliers SM, IM, the former coupled to SVP, to provide the desired ratio, the latter settable for scaling purposes. Comparison is made in a pulse frequency comparison circuit PFC, the output of which comprises pulses where frequency and polarity correspond to the error and drive a stepping motor MS which adjusts the fine control FP N of one of the motor control systems. If the stretch is not to be uniform throughout the mill the signal SVP is omitted from the appropriate stands, and any pair can be excluded from the adjusting sequence. The speed of the first stand may be set by the control unit FC if the D.C. reference signal is converted to pulses and applied at A. |
