GB756134A - An improved variable-pitch propeller for airplanes or other flying machines - Google Patents

Abstract

756,134. Variable-pitch propellers. RATIER AVIATION-MARINE. Oct. 29, 1954 [July 28, 1954], No. 31336/54. Class 114. Each blade in a variable-pitch propeller is mounted in a helical bearing 15, Fig. 1, in a socket 1a on a central hub 1 and carries at its base a gear 25 rigid with it and adapted to engage a rack 31, Fig. 5, secured at one end to a single-acting piston 40 working in a chamber 57 containing ahead of the piston hydraulic fluid provided by a pump 49 driven by the propeller shaft through planet wheels 48 running on a stationary sun wheel 47, a centrifugal governor 67 between the pump and the chamber 57 controlling the increase or decrease of pressure in the chamber to lower or raise the pitch of the propeller blades. Fig. 5 shows the blade at zero pitch with hydraulic fluid locked in the chamber 57 by closure of a release passage 60 by a land 67a on the governor 67 and a pressure passage by a valve 66 in position 66a. The governor 67 moves outwards, against an adjustable spring 68, under centrifugal force until at a speed slightly exceeding the desired one, the land 67a partially clears the passage 60 opening the chamber 57 to a low-pressure chamber 39a communicating by an orifice 54 with the suction chamber 39b of the pump. The centrifugal force of the rotating blades draws them outwards along their helical mountings increasing their pitch and rotating the gear 25 to displace the rack 31 and piston 40 away from the blade. When equilibrium is established, the governor land 67a moves inwards to open the passage 60 and close the passage 61. Pressure built up by the pump lifts the valve 66 to open a release. passage 65 to the chamber 39a.