GB673113A - Improvements in or relating to mountings for blades of wind motors or of propellers or of helicopter rotors - Google Patents

Abstract

673,113. Helicopters. BROWN & CO., Ltd., J., MENSFORTH, T., and POUNCEY, H. Oct. 3, 1950 [Oct. 3, 1949], No. 25410/49. Class 4. [Also in Group XXVI] In a mounting for the blades of a helicopter rotor of the kind in which a limited degree of freedom of swinging movement is permitted for each blade abount one or more axes transverse to the longitudinal axis of the blade, a member; pivotally attached to the blade root or to a part attached to the root is slidably mounted in a socket attached to the rotor hub and urged inwardly by resilient means, the socket and the root or the part being so shaped that, when brought into mutual contact at the inner limit of travel, they restrain the pivotal movement. Each blade 10 is carried by a tubular support 16 which is rotatably mounted on a stub shaft 17. Variation of the blade pitch is carried out by a hydraulic or pneumatic motor 31 which is connected by linkage 30 to a shaft 28 which is connected by universal joints 23, 26, a splined shaft 25 and gearing 20, 21 to the support 16. To permit the blade 10 to pivot about an axis parallel to the axis of rotation of the rotor and about a further axis tangential to a circle of revolution, the stub shaft 17 is formed with one fork 32 of a universal joint the other fork of which is carried by a cylindrical member 39 which is slidable in a cylindrical guide 40 fixed to an arm 11. Blocks 41 carried by the member 39 engage slots 42 formed in the guide 40, and carry pegs 45 to which is pivotally attached a member 47. The latter is attached by links 49 to springs 51 which are anchored to a plate 52. The required spring tension is obtained by drawing the plate 52 inwardly by means of a chain 55 which encircles a sprocket 56 which can be turned by a key applied to a square portion 58 of the sprocket spindle. When the rotor is stationary or only rotating at a slow speed, the springs 51 draw the blades inwardly so that a curved portion 61 of each shaft 17 seats on a resilient seating 62 and pivotal movement is consequently prevented. A bearing 64 for the shaft 28 slides in a slideway 67 and is moved radially in unison with the blade 10 by engagement with a peg 44 carried by one of the blocks 41. The resultant relative movement between the two elements of a dog clutch 29 having tapered teeth controls the amount of backlash between the elements. Thus, there is a positive drive when the blade 10 is in its normal running position, but when the blade is in its retracted position the backlash is sufficient to permit it to take up any position within limits. To enable the blade to take up a feathered position, its longitudinal axis of rotation is displaced from the centre of pressure by, say, one inch. According to the Provisional Specification, a lever arm engaging a lug carried by the blade root is used instead of the gearing 20, 21.