GB567710A - Improvements in and relating to pitch controlling means for aeronautical propellers - Google Patents

Abstract

567,710. Fluid-pressure servomotor-control systems. HOOVER, W. S. March 1, 1943, No. 3328. [Class 135] In means for varying propeller pitch in order to maintain the driving engine speed constant, the propeller hub carries a pitchchanging motor, a pump supplying said motor, and a governor controlling the pump, and means are provided for controlling the action to prevent hunting and for driving the pump independently to change the pitch when desired with the driving engine stopped. The pump comprises a sleeve 40, Figs. 1 and 3, slidably keyed to the propeller hub 24 so as to rotate within members 42, 44, normally held from rotation by a gear 98. The sleeve 40 has vanes 68, 70 contacting the inner elliptical periphery of the member 42 and is provided with internal grooves 58, 60, 62. When the governor weights 46 move in response to a change in propeller speed, the members 40, 42, 44 are thereby moved axially in one direction or the other, to connect the pump delivery groove 60 with one or the other of the grooves 130, 132 in the hub, and one or the other groove 58, 62 with the other of the grooves 130, 132. Liquid is thereby drawn from a reservoir 152, and supplied to the motor 34 which effects a pitch change through reducing gear 38 and a gear 32. When the driving engine is stopped, the pump may bedriven by rotating the gear 98 from a motor 99. The means for preventing hunting comprises a member 156 fixed to the hub and provided with fluid manifolds 166, 168, a groove 162 divided by vanes 170, 172, Fig. 9, and a reservoir 164. A member 174 carrying vanes 176, 178 is fixed to the gear 32, so that when the latter is operated, liquid is forced to the reservoir 164 through a restriction 222 or 238. If due to rapid operation, the flow tends to be greater than the restriction can accommodate, the pressure generated acts on a piston 186 to move a sleeve 192 to throttle the flow from the groove 60 to the motor 34, the degree of throttling increasing as the pitch assumes the necessary condition. The propeller blades may be locked in the adjusted position by a device including a cam 228 held against rotation by balls 232 until released by the motor 34 being set into motion.