GB517117A - Improvements in or relating to variable-pitch airscrews - Google Patents

Abstract

517,117. Screw propellers. ROTOL AIRSCREWS Ltd., and LUSTY, I. April 9, 1938, No. 10948. [Class 114] In a variable pitch propeller installation wherein a datum speed motor is employed, this motor controls means for rendering the pitch varying motor inoperative upon failure of the constant speed mechanism. A variable pitch propeller 12 utilises the pitch changing electric motor 13 driven off a battery 14 through lines 15 and either 16 or 17. A constant speed motor 32 driven at a regulated speed from the battery 14 drives generator 31 which in turn energizes a three-phase synchronizing alternating current electric motor 24. The motor 24 drives one pinion 23 of a differential, another pinion 22 of which is driven by the engine and the planet members 25 are used to drive a bevel wheel system 27, 28, 29, 30, the latter of which is used. as a switch member 19 The circuit for the motor 24 includes an on and off switch 20 and a main switch 34. When the switch 34 is on, the motor 24 is rotated and as long as the motor and engine speeds are alike, switch member 19 remains in a neutral position. When the engine speeds up or slows down, the switch 19 receives a motion and contacts with 35 or 36 whereby motor 13 increases or decreases the pitch accordingly. In the event of an electric breakdown, switch 20 opens and the motor 13 is deenergised and the propeller then runs as a fixed pitch propeller. When it is required to feather the propeller, the switch 34 is passed over to the other pair of contacts and motor 13 operates until the switch is opened again. In an alternative, instead of a rotary electric motor 24, a reciprocating ratchet type motor may be employed.