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of Stenson Road, Derby, British licensee of the Clarke Viscosity Control Valve.
The valve is fitted in the oil scavenge system between the engine pump and the cooler, its function being to control the degree of cooling necessary to maintain a constant temperature or viscosity of the oil entering the engine, under the widely varying conditions experienced in flight.
1939 Several types of this valve were in production to meet the requirements of many engines and installations.
Clarke Aircraft Products, of the same address, produced the full range of Viscosity Control Valves for H. B. Clarke Engineering Company Limited.