GB552255A - Means for preventing the aeration of oil in oil circulating means - Google Patents

Abstract

552,255. Aeration preventing in liquid pumps. LE CLAIR, C. C. S., and TELCALEMIT, Ltd. Aug. 22, 1941, No. 10705. [Class 102 (i)] In a liquid circulating system in which a pump withdraws liquid from a container, aeration of the liquid circulated by the pump is prevented by a level detecting means which permits or stops the flow of liquid from a supply source to the pump when the level of the liquid in the container is low or high, respectively, and the flow of liquid from the container to the pump is stopped when the pump is receiving liquid from the supply source. In the form shown, oil from an engine sump 1 is drawn by a scavenge pump 2 through a suction pipe 3 with a spring-pressed bias valve 5, and is delivered by a discharge pipe 4 to a storage tank from which it is returned to the engine by a pressure pump. An auxiliary pump 8 is connected to the sump 1 by a smaller suction pipe 7 arranged with its end above the end of pipe 3, and the discharge pipe 9 from the pump 8 is connected to the pressure end of a cylinder 10 which is connected by a flow-restricting orifice 11 and a return pipe 9a to the sump 1. The cylinder 10 contains a spring 23 and a piston valve 12 having a piston part 13 which acts against a stop 24, and valve parts 14, 14a separated by a recess 15 which co-operates with inlet and outlet ports 16, 17 connected by pipes 18, 19, respectively, to the storage tank and to the suction pipe 3. The parts 13, 14 are separated by a space 21 which is connected by a port 22 and a small leakage bleed-off pipe 20 to the sump 1. When the level of the oil in the sump 1 is above the end of the pipe 7, the auxiliary pump 8 circulates oil, and pressure is built up in the end of cylinder 10, due to the resistance of the orifice 11, to force the valve 12 into the position shown. The ports 16, 17 are closed by the valve part 14 and oil cannot flow from the storage tank to the suction pipe 3. The demand of the scavenge pump being greater than the supply, the oil level in the sump falls until it is below the end of pipe 7. The auxiliary pump 8 then circulates air, the flow of which is not resisted by the orifice 11 so that the spring 23 forces the valve 12 against the stop 24. Oil then passes from the storage tank to the suction pipe 3, flow of oil from the sump 1 being prevented by the bias valve 5, so that the level of the oil in the sump again rises. By this means the oil level in the sump is maintained approximately at the level of the end of the pipe 7 and flow of air through the scavenge pump 2 is prevented. In a modification, the return pipe 9a and the orifice 11 are formed in the valve 12 itself, the bleed-off pipe 20 is enlarged, and the stop 24 is placed eccentrically or provided with an internal port. Alternatively, the piston valve may be replaced by a bellows or diaphragm operated valve.