Patent GB-973997-A (GB)
Title: Improved system and apparatus for the linear measurement of bodies in motion
Inventor: HAMILTON-JONES GLYN
IPC: G01B11/04
Filed: 1959-12-07
Abstract: 973,997. Electric selective signalling systems. DAVY & UNITED INSTRUMENTS Ltd. March 7, 1961 [Dec. 7, 1959], No. 41558/59. Heading G4H. In a system for measuring the length of a red-hot metal bar, a series of 45 range phototransistors 10 1 -10 45  are mounted at one foot intervals in a water-cooled manifold along the path of the bar, and a datum phototransistor XO is mounted at a predetermined distance from transistor 101 and has associated vernier transistors X4 and X8 spaced four inches and eight inches therefrom. When the leading edge of the bar reaches transistor 10 45 , a uniselector switch having banks 13-15 is stepped round quickly until wiper 16 reaches the contact connected to the first range transistor which is illuminated by the trailing edge of the bar. The switch then follows the progress of the bar by advancing one step as each successive range transistor is passed by the trailing edge of the bar. When the leading edge of the bar reaches datum cell XO the uniselector switch is conditioned to step only once more as the trailing edge passes to the next range cell, and an indication of the amount by which the leading edge has progressed beyond XO at this instant is obtained from XO and the vernier transistors X4, X8. Detailed operation. In a preferred embodiment XO is mounted 33<SP>1</SP>10<SP>11</SP> from 10 45  to give a range of measurement of between 34<SP>1</SP> and 78<SP>1</SP>, and the operation will be described for the case where the bar is just over 76 feet long. When the leading edge reaches 10 45  this transistor conducts, and as line 11 is maintained at earth potential by normally conducting transistor X5, the negative basis on the control grid of V1 is reduced, V1 conducts and relay L1 operates. Contacts 4, 5 of L1 remove the H. T. supply to multicathode tube indicators 23, 24, 26 and contacts 2, 3 energize the coil 19 of the uniselector through interrupter contacts 21. Wipers 16,17,18 are then rotated rapidly, wiper 18 reaches the bridged contacts 25 and connects earth to the cathodes of V2, V3, whereupon V3 conducts and L3 operates to complete a holding circuit over contacts 2, 3, When wiper 16 reaches the contact connected to the first range transistor 10 1  (which is still conducting), V2 conducts and L2 operates to arrest the uniselector by holding coil 19 energized. When the trailing edge pases 10 1 , relay L2 releases and the uniselector steps to contact 2 where it is again arrested since 102 is still conducting. The operation continues until the leading edge reaches XO which thereupon conducts and cuts off transistor XS. This has no initial effect on the operation as XS is short circuited by contacts 5, 6 or L2, but as soon as the trailing edge passes 10 3 , L2 releases, line 11 assumes a negative potential and L1, L3 release. The uniselector advances one position, H.T. is applied to indicators 23, 24, 26 and a triggering potential is applied to tubes T0, T4, T8. One of tubes T0, T4, T8 fires according to which of X0, X4, X8 are illuminated, and the length measurement is thereby obtained in tens of feet, feet and thirds of afoot in indicators 23,24, 26. The range of the system may be increased by providing further datum transistors X0 and associated vernier transistors X4, X8 spaced further away from 10 45  a switching arrangement transferring control to the desired datum transistor X0 in accordance with the length of the bar. Any one of the range transistors may be used to indicate operation of the uniselector, and the datum cells may also be situated ahead of the range cells.