GB795525A - Improvements in or relating to indicating and/or measuring instruments - Google Patents

Abstract

795,525. Photo-electric control systems. BRITISH IRON & STEEL RESEARCH ASSOCIATION. Sept. 26, 1955 [Sept. 24, 1954], No. 27651/54. Class 40 (3). In measuring or indicating instruments operated by radiation emanating from the edge of a member, for example a hot steel strip, a radiation detector operates means to move a member which adjusts the proportion of the radiation which can reach the detector in such a way as to maintain constant the detector output. The position of the member will then indicate the position of the edge. As shown, two measuring units 14 and 15 are mounted on rails 13 above the moving strip 12. They include tubes 20 bearing lenses which direct radiation from the strip through two holes in a bottom plate of each unit. One hole is fixed in size, while the other in each unit is varied by a shutter moving in a direction normal to the motion of the steel strip. Radiation from each hole falls on a separate photo-cell, and the shutters of each unit are operated by means responsive to the difference in the reception of the two cells of the unit, in such a sense as to maintain the response of the two cells equal. The position of the shutter thus gives an indication of the position of the edge of strip 12 which it is observing. In the circuit shown in Fig. 3 the two photo-cells 33 and 34 of unit 14 control in a differential manner servomotor 27 which drives a servo-transmitter 43. In a similar manner a transmitter 43a is driven in unit 15 and the two transmitters 43 and 43a drive a single receiver operating a pointer indicating the width of strip 12. The units 14 and 15 are altered in position by connection with an endless belt 16 driven by a motor 18. As shown in Fig. 4 two control elements 50 and 51 are geared together in a 10 to 1 ratio and are provided with indicating pointers 53. They operate transmitters 54 and 55 connected to coarse receiver 56 and fine receiver 57 which are also geared together in a ratio of 10 to 1. When the misalignment of the rotors of coarse transmitter 54 and coarse receiver 56 is greater than a certain amount the current passing through relay 61 operates switch 60 so that the motor 18 is operated from receiver 56 to bring the units approximately to the desired position. When the misalignment is reduced below a certain amount the two-way switch 60 changes over and the final setting takes place under the control of fine receiver 57. In a modification units 14 and 15 are fixed and movable optical elements are provided to focus the edges of the strip irrespective of its actual width.