GB449247A - Improvements relating to variable or controllable pitch airscrews - Google Patents

Abstract

449,247. Screw propellers. MILNER, H. L., The Folly, Gotherington, Gloucestershire. Nov. 23, 1934, Nos. 33746/34 and 17082/35. [Class 114] An automatic variable-pitch air-screw wherein the blades are connected to an axially movable sleeve are provided with controls for limiting the extent of such axial movement in accordance with the speed or acceleration of the screw propeller. The blades 10 are connected by links and pins 13 with a sleeve 15 which is under spring restraint 17. The sleeve is also provided with rods 18 adapted in their limiting positions to contact with depressions 31 in a flywheel member 21, the latter being mounted on a screw thread 20 and thus in accordance with the speed of the engine assumes a movement to or from the main boss. Its own movements are limited by adjustable flange members 25, 24. Further, the flange 24 is provided with flexible lip 32 engageable with a ring 33 on the flywheel for the purpose of damping and preventing hunting of the flywheel. In a modification, an adjustable sleeve 36 is provided on one side of the flywheel member 21 which carries centrifugal weights 39 adapted to contact with the adjustable member 36 or with a plate 42 which in this case carries the depressions into which the rods 18 can pass for the purpose of locking the blades in the maximum pitch position. In yet another modification, the sleeve 15 carries pivotal rods 18 having weights 58 thereon and a number of prongs 50 ... 55. The two rods are coupled by a spring 57 acting in opposition to the centrifugal forces on the weights 58. The rods 18 pass through the openings 56 in the boss which are shaped so that the projections 50-55 can engage at different speeds with the edge of the openings 56 and so limit the pitch changes. In another form, arms 64, 65 having inserts 67, 68 are pivoted and abut against the shoulder 69 on a sleeve 70 slidable on the shaft against a compression spring 71. The spring is disposed between an adjustable stop 72 in the frame 73 and in this case the rods 18 are connected to the stop plates 74 which are guided at their ends by the plate 72. The stop plates 74 are slotted to receive levers 77 formed integrally with the arms 64, 65 and each lever has a roller 78 engaging a corresponding slot in the stop plates 74 whereby angular movement of the arms is limited.