Patent GB-1075822-A (GB)
Title: Tanks for holding liquids
Inventor: ROBINSON NORMAN ROBERT
IPC: B65D88/54
Filed: 1964-03-31
Abstract: 1,075,822. Filling and emptying tanks. ROLLS-ROYCE Ltd. March 19, 1965 [March 31, 1964], No. 13294/64. Heading B8T. [Also in Division G1] A tank 21, for use in a servo control system on an aeroplane gas turbine engine, comprises a first chamber 41 from which liquid may be drawn off, the chamber being maintained full of liquid when in use, whatever the disposition of the tank and working state of the servo system. The chamber 41 includes inlet and outlet connections 31, 30 through which liquid in the closed servo control system is pumped continuously, liquid entering the inlet passing through a Venturi ejector pump 45 to draw additional liquid from a second chamber 42 through an aperture 46 into the first chamber, and. make up any loss through leakage. Air drawn by the Venturi pump 45 from the second chamber 42 into the first chamber 41 is vented through a pipe 51 and a one-way valve 53 to a third chamber 43. To fill the tank 21 with oil initially, a supply hose is connected to the outlet 30 and oil is pumped through a tube 47 into the first chamber 41. The oil rises, purging the chamber of air, which flows into the second chamber 42 through a tube 44 and the aperture 46, and then into a third chamber 43 through an inverted U-tube 50. The air may also flow through the one-way valve 53 to the third chamber 43, if the pressure is sufficient. The oil rises to a level indicated by a line 70 and then flows through the tube 44 and the aperture 46 into the second chamber 42; when this chamber is also full, the oil flows into the third chamber 43 which it fills to the level indicated by a line 72. When this level is reached, the supply of oil to the tank is stopped. Upon starting the gas turbine engine, compressed air flows through a duct 60 and a valve 58 to the air space in the third chamber and the whole tank is pressurized, since oil from chamber 43 is urged through the second chamber 42 and into the first chamber 41. The level of the oil in the chamber 41 rises, urging the trapped air out through the one-way valve 53. This continues until both the first chamber 41 and a tube 51 as far as the one-way valve 53 are full of oil. A valve 63 is spring biased to the operating pressure of the system and if this pressure is less than that prevailing in the chamber 43, the excess air passes through a duct 55, a valve 57 and a vent 61 to the atmosphere. Leakage oil may be collected and pumped back into the circuit through a port 56. Fig. 4 (not shown) illustrates the tank in an inverted position in which the air pocket moves to the bottom of the third chamber (43) adjacent an end wall (35) and thus no oil can be supplied from the third chamber (43) to the second chamber (42). The first chamber (41) is maintained full of oil by oil supplied from the second chamber (42), the oil level in the second chamber (42) falling to a level indicated at (81) if oil is withdrawn into the servo control system by its being used. In one modification, the Venturi pump (45), Fig. 8 (not shown), connects the inlet 31 to the third chamber (43) instead of the first chamber, and draws off air from the second chamber (42) through a gravity valve (52<SP>1</SP>) and a pipe (51<SP>1</SP>). The reduced pressure thus induced in the second chamber (42) draws in oil through the inverted U-tube (50) from the third chamber (43). Flow of oil through the outlet (30) draws oil through a pipe (73) from the second chamber (42) into the first chamber (41). The gravity valve (52<SP>1</SP>) closes if the tank (2) is inverted, to prevent oil out through the pipe (51<SP>1</SP>) from the second chamber (42). In a variation of this modification, Fig. 9 (not shown), the wall (40) between the first and second chambers (41, 42) is omitted, so that these two chambers are combined, and the tank (21) contains only two chambers (41, 43). The Venturi pump (45) draws off air from the combined first and second chambers.