Patent GB-606895-A (GB)
Title: Improvements in apparatus for detecting and indicating a change of colour in liquids
IPC: G01N21/78
Filed: 1945-07-09
Abstract: 606,895. Photo-electric apparatus for detecting and indicating colour or translucency changes in liquids. SQUIRES, M., SAVAGE, J., BRECHNER, D., BROATCH, J. D., and BIELAK, W. M. July 9, 1945, No. 17483. [Class 40 (iii)] [Also in Group XL (c)] Sequential changes in colour or translucency of a fluid are detected by a balanced array of photo-cells in the input of an electronic trigger circuit operating indicating means through electromagnetic relays. A light-absorbing fluid chamber is placed in the photo-cell light path so that any change in colour or translucency unbalances the optical system, applies a corresponding D.C. voltage to trip the trigger circuit (switchable to operate at different D.C. voltage levels) and so energizes the indicating means. Fig. 3 shows a form of the invention in which a fuel pipe-line PL carries alternately red M.T. spirit and green 100-octane spirit, and may be connected by valves CU1., CU2, CU3, CU4 to one of two storage tanks ST1, ST2. Fuel is byepassed through BP to a glass-walled absorption chamber AT (Fig. 4), contained in the pipe-line unit PLU, a lamp S illuminating balanced photo-cells P1, P2 respectively through red-absorbent filters F1, F2, the absorption chamber, and an adjustable iris D covered by a diffuser G. The photo-cells are connected in parallel opposition, and when the absorption chamber contains red fuel only, a small D.C. voltage appears on the grid of valve VS1 in the indicating unit IU (Fig. 6). Valves VS1 and VS2 are connected to have two stable conditions in which either VS1 conducts and VS2 cuts off, or (as initially) VS1 cuts off and'VS2 conducts. AS A relay - is connected in the anode circuit 3- of VS2, the steady bias on the grid of which is controlled by potentiometer RS10 while two alternative negative bias voltages on the grid of VS1 are derived from potentiometers RS13, RS14, and selected by switch CS, which is initially in position 1. When the photo-cell voltage is zero, VS1 is cut off and VS2 conducts, AS relay - operates, and red indicator lamp RL 3 lights. The arrival of red fuel contaminated with green fuel increases the illumination of photo-cell P1 and a positive D.C. potential is applied to the grid of VS1, until at a voltage dependent on the bias from potentiometer RS13 and corresponding to (say) 15 per cent admixture of green fuel, VS1 conducts, VS2 cuts off, AS and - releases, causing bell B to ring and 3 green indicator lamp GL to light. After valve adjustment to direct the mixed fuel into waste tank WT, the pipe-line operator rotates switch CS to position 2, mechanical safety devices ensuring that motion is clockwise and one step at a time. The bell stops and a higher negative bias is applied to VS1 from potentiometer RS14:, AS VS1 cuts off, VS2 conducts, and - operates, 3 causing RL and GL to remain alight. Increased contamination of red fuel by green causes an increase in the photo-cell potential until at (say) 85 per cent contamination, VS1 AS again conducts, VS2 cuts off, - releases, the 3 bell rings and RL is extinguished. After valve adjustment to direct the predominantly green fuel in the line to the appropriate storage tank, the operator rotates CS to position 3, stopping the bell. The photo-cell potential rises until the fuel in the line is 100 per cent green, but decreases with increasing admixture of red until !when (say) 15 per cent red fuel is present, VS1 AS 'cuts off, VS2 conducts, - operates, the bell 3 'rings and lamp RL lights. After valve adjustment to direct the mixed fuel to the waste tank, CS is set to position 4, biassing VS1 from RS13, causing it to conduct, VS2 to cut off, and AS - to release. The bell stops and RL and GL 3 remain alight. The propertion of red fuel increasing, the photo-cell potential falls until VS1 AS cuts off, VS2 conducts, - operates, GL is. 3 extinguished and the bell rings. Valves are adjusted to direct the predominantly red fuel into the appropriate storage tank, and CS is set to position 1, stopping the bell and resetting the equipment to its condition at the beginning of the cycle of changes. The power supply unit PSU (Fig. 5) is fed with 24 v. D.C. and provides by means of barretters R3, R4 and carbon pile regulators CP1, CP2 a stabilized 18 v. supply for bias, photo-cell lamp and valve heaters, and a 300 v. smoothed H.T. supply from the motor generator G1. Inter-unit connection is made by plugs W1, W2 and the main switching operates through switch RS2 and BS contactor RL1, The differential relay - 1 causes continuous ringing of the alarm bell on failure of the 18 v. supply, photo-cell lamp, or a valve heater. Methods of alignment and adjustment of the equipment are described. In modifications (not shown), manually or automatically stepped uniselectors may be used instead of the switch CS, relay or servomechanism may automatically control the fuel valves, or the equipment may operate on changes involving fluids of three or more colours.