Patent GB-756665-A (GB)
Title: Improvements in or relating to control means for motor-driven pumps
Inventor: MEREDEW GEORGE CHARLES
IPC: F04D15/00
Filed: 1953-04-18
Abstract: 756,665. Centrifugal pumps; elastic-fluid turbines. SELF-PRIMING PUMP & ENGINEERING CO., Ltd., and ROLLSROYCE, Ltd. April 12, 1954 [April 18, 19531, No. 10468/53. Classes 110(1) and 110(3) [Also in Group XXIX] In a motor driven pump of the kind in which the pump produces a pressure difference which varies with the motor speed, a device responsive to variations in the pressure difference operates a valve, rheostat or other means for controlling the supply of operating medium (which may be a fluid or electricity) to the motor to restrict or cut off the supply if the pressure difference has a value P 1  below a predetermined value P 2 , to increase the supply as the pressure difference rises to P 2  to maintain the supply as the pressure difference rises from P 2  to a value P 3  and then to reduce the supply as the pressure difference increases from P 3  to a value P,. A centrifugal fuel pump is driven through gearing 11, 12, Fig. 1, by an air turbine rotor 16; the assembly is mounted on the bottom wall of a fuel tank. Driving air passes from a pipe fitting 25 to the turbine nozzles by way of an inlet elbow 22 and an annular conduit 20, and is exhausted through a shroud 31 surrounding the turbine and leading to an outelt elbow 22. The air supply is controlled by a valve comprising a fixed ported sleeve 40 and a ported inner sleeve 44 which is rotatable by means of an arm 50 and a push rod 51, Fig. 4. The pump discharge pressure is communicated by way of a connection 55 to the interior of a chamber 54, where it tends to collapse a bellows 53 mounted on the push rod 51 against the action of springs 60, 61. The bellows interior is vented to the fuel tank. The lighter spring 60 is compressed first as the pump discharge pressure rises, and the air inlet valve 40, 44 gradually opens until it is fully open when the spring 60 is fully compressed. The valve 40, 44 remains fully open until the pump discharge pressure has risen sufficiently to commence to compress the stiffer spring 61. The resultant further movement of valve 40, 44 tends to close it. A diaphgarm or piston may be used in place of the bellows. A by-pass valve 70, comprising a valve disc 73 held off a seat 72 by a spring 74, admits sufficient air to start the turbine when the valve 40, 44 is in its initial closed position; the valve 70 closes when the pressure difference across it reaches about 5 lb. per square inch. Valve 70 may be omitted, valve 40, 44 then having a bleed around it or arranged to leak when closed. If the pump discharge pressure fails as through exhaustion of the fuel, valve 40, 44 closes and the air flow through the by-pass maintains the turbine speed at a safe value. A piston valve 173 in the flow path between the connection 55 and the interior of chamber 54 is actuated by the push rod 51 and is fully open when the valve 40, 44 is in its initial closed position; it closes when the valve 40, 44 reaches its fully open position and remains closed as the valve 40 44 moves towards its second closed position. While valve 173 is open, fuel may enter and leave the chamber 54 with little restriction, so that operation of valve 40, 44 is rapid in either direction. While valve 173 is closed, fuel can enter chamber 54 through two non-return valves 170 but can leave only by leakage past valve 173 or through a bleed, so that valve 40. 44 can be closed rapidly but can be opened only slowly; this prevents hunting. Valve 40, 44 controls the air supply to all the turbine nozzles 'simultaneously; in an alternative arrangement, the valve shown in Fig. 6a may be used instead. The stationary outer sleeve 80 has six equally spaced ports 81-86 which lead respectively to six equally spaced turbine nozzles. The rotatable inner sleeve 90 has pairs of ports 91, 91a and 92, 92a which are respectively thrice and twice as wide as further ports 93, 93a. The valve is shown in the initial closed position. As the pump discharge pressure increases, sleeve 90 is rotated clockwise, a position being reached at which all the ports are fully open. Further rotation closes the ports 83, 86, then the ports 82, 85 and finally the remaining ports 81, 84. The Provisional Specification refers to Specification 731,672.