GB468602A - Improvements in and relating to variable pitch air-screws - Google Patents

Abstract

468,602. Variable - pitch airscrews. JUNKERS FLUGZEUG-UND MOTORENWERKE AKT.-GES. Nov. 5, 1936. No. 30146. Convention date, Nov. 11, 1935. [Class 114] The blades of a variable-pitch airscrew are adjusted by hydraulic motor of the rotary kind through angles of 360‹ and over, the transmission members between it and the blade root are of high ratio and each element of the mechanism describes a purely rotational movement. The boss 5 is secured to a hollow shaft 1, driven by gear-wheels 51, 52 from the engine shaft 53. Mounted beyond the boss 5 is the gear-wheel motor 7, 8 connected by passages 35, 36 with a rotary pump 30, the passages having control valve 37 under the control of the lever 40 and a rod 41 which passes to the pilot's cockpit. When the valve 37 is in the neutral position, the pump supply is shortcircuited by valve 45. The spindles 9<1>, 10 of the motor 7, 8 are produced and carry worm wheels 13, 14 respectively, which gear with worms 15, 16 and other gear-wheels 21, 22 on the roots of the blades 11, 12. The setting of the blades is indicated by means of a screwed extension 46 on one of the operating members which acts upon a nut 47 and produces a motion endwise of the sleeve 49, movements of which are in turn transmitted to the cockpit by a rod 50. When the valve 37 is turned to the position of Fig. 1a, an increase of pitch of the blades is produced, and when turned to the position in Fig. 1b the pitch is decreased and if continued long enough the blades move into a braking position. In a modification, the pump supply is controlled by a piston valve 61 operated automatically by a centrifugal governor 65. The setting of this governor may be modified by altering the compression of the spring 68 through the levers 71, 74, 77 and the hand wheel 78. In a further modification, the gearwheel motor is mounted as at 88 immediately in front of the propeller boss and one shaft 83 is produced to carry a pinion 84 which gears internally with a pinion 85 having worm teeth externally engaging a number of worm wheels 90, one for each blade. In a modification of this arrangement, two motors of the gear type are provided, and drive a common bevel wheel from which the drive is taken to each blade. Alternatively, there may be gear-type motors of the same number as there are blades, the shafts of each one having a worm wheel which drives its particular worm gearing, and also has a bevel wheel meshing with a central common bevel wheel whereby movement of the three blades is synchronized.