GB662673A - Improvements in or relating to valves for controlling hydraulically-operated mechanisms - Google Patents

Abstract

662,673. Jet propulsion plant. BRISTOL AEROPLANE CO., Ltd. April 25, 1950 [May 4, 1949], No. 11949/49. Class 110(iii) [Also in Groups XXIX and XXXIII] A gas turbine power plant having a turbine rotor 13, Fig. 1, driving the compressor 14 and a rotor 11 driving a variable-pitch propeller 10, has the latter so controlled that the speeds of the two rotors are maintained in a required ratio. The casing 20 of a differential hydraulic pump is driven by the rotor 11 whilst a gear wheel 22 of the pump is driven by the rotor 13 so that when the rotors are running at the required speed ratio, the pump discharges sufficient liquid to a chamber 33, Fig. 2, to make up for leakage through an outlet 41 and to balance a spring 31 acting on a control valve 28 so that the latter is maintained in a position in which the propeller pitchchanging motor 25, which is supplied by a pump 27, is stationary. A second liquid at constant pressure is delivered through a pipe 35 and a valve member 39 to the chamber 33 and the arrangement is such that a change of delivery pressure from the differential pump due to a variation in viscosity of the liquid acts on a piston portion 37 of the valve member 39 to vary the flow of the second liquid to compensate for the change in viscosity . The valve member 39 also checks hunting when the control valve 28 is operated since any change of pressure in the chamber 33, consequent upon a variation in output of the differential pump, causes actuation of the valve member 39 such as to lessen the change of pressure in the chamber. The control valve is surrounded by an adjustable sleeve 29 by which the propeller may be feathered or,reversed in pitch. The speed of the turbine rotor 13 is controlled by a governor 16 which regulates the quantity of fuel supplied to the combustion equipment and whose datum is adjustable by a hand lever 18.