GB399313A - Improvements in or relating to variable pitch airscrews - Google Patents

Abstract

399,313. Air-screws. FAIREY AVIATION CO., Ltd., Cranford Lane, Hayes, Middlesex, and FORSYTH, A. G., Venlaw, Burdon Lane, Cheam, Surrey. Sept. 29, 1932, No. 27061. [Class 114.] A variable-pitch air-screw includes a differential screw mechanism connected with two skew gear-wheels of opposite sense, mounted coaxially of the air-screw shaft, said skew wheels being adapted to be restrained against rotation for the purpose of altering the pitch of the propeller blades. Within the hollow driving shaft of a propeller are two coaxial shafts 17, 18 having at their inner ends spur wheels 23, 24 which are in mesh with corresponding teeth formed on two brake drums 23a, 24a that are furnished with brake bands 23b, 24b controlled by a lever 26c. The outer ends of the shafts 17, 18 carry skew gear wheels 29, 30 of opposite sense which engage permanently pairs of gear wheels 31, 32, and 33, 34 mounted on parallel transverse shafts 35, 36 and 37, 38. The shafts 35, 37 are connected by means of right and, left-hand skew gears 39, 40 with a transverse rotatable sleeve 41 splined on to a shaft 44. This shaft 44 bears two differential screw threads 45, 46, the smaller of which 46 engages a threaded boss 47, whilst the other engages a screwed lug 48 on a slidable sleeve 55 having an open jaw member 57 which engages an eccentric pin 58 at the root of a blade. When the hand lever 26c is moved to brake one or other of the wheels 23, 24 one or other of the skew gears is given a relative rotation and a corresponding movement takes place of the shaft 44 whereby the blade is altered in pitch. As an alternative to the brake drums the shafts 17, 18 may be furnished with notched discs adapted to be engaged by spring-influenced pawls carried by a lever similar to the lever 26c.