GB476852A - Improvements in or relating to variable pitch propellers automatically regulated to constant speed - Google Patents

Abstract

476,852. Fluid-pressure servomotorcontrol systems. SIEMENS APPARATE UND MASCHINEN GES. May 5, 1937, No. 12890. Convention date, May 6, 1936. [Class 135] [Also in Group XXXIII] A variable-pitch propeller which is automatically regulated hydraulically to constant speed and including a closed oil circuit containing an oil pump, a regulating valve and an oil motor and with means for connecting these with the blades for varying the angle is characterized by the accommodation of the whole of this apparatus within the hub of the propeller, the oil pump being driven by a wind-mill screw. The blades 11 of the screw propeller are coupled by gearing 6 with an oil motor 5 adapted to be driven by an oil pump 2 which is in turn actuated by a wind-mill screw 3. The pipe connections between the pump and the motor are controlled by a valve 8 disposed in the hub so that on rotation of the propeller centrifugal force tends to move the valve, such tendency being under the constraint of an adjustable spring 19. Under normal conditions, the valve is positioned as shown and no oil passes to the pump 5. With rise or fall of propeller revolutions, the valve moves so as to couple up either the pipe 13 or the pipe 14 to the delivery side of the pump 2, thereby changing the pitch and remaining operative till the propeller revolutions are back to normal. For minimum pitch position a cam or projection 15 on the blade root actuates a bell-crank lever 16 and contacts with a pin 17 so as to move the control piston valve 8 back to the position in Fig. 1.