Patent GB-403199-A (GB)
Title: Improvements in variable pitch propellers
IPC: B64C11/36
Filed: 1932-09-23
Abstract: 403,199. Screw propellers. HEENAN & FROUDE, Ltd., and WALKER, G. H., Worcester Engineering Works, Worcester. Sept. 23, 1932, No. 26438. [Class 114.] In variable pitch propellers wherein power is taken from the propeller shaft for adjusting the pitch of the blades, a differential gear is employed, the cage of which is driven from the propeller shaft, one sun wheel is attached to a spindle normally rotating at the same speed as the cage and the other sun wheel is loosely mounted. Each sun wheel is provided with a positive brake comprising a non-rotating element and a rotating element having means for positive engagement, the non-rotating element being slidable in an axial direction. The blades 1 have an adjusting mechanism which at the root comprises a worm wheel 11, which, through gearing 12, 13, 14, is connected with a spur wheel 15 secured to a shaft 16 passing through the hollow propeller shaft and at its inner end carries a gear wheel 17. Encircling the shaft 16 is a casing secured to the propeller shaft and carrying also a bevel gear. The inner bevel 17 on the shaft 16 is geared to a bevel wheel on a solid spindle 18 which has secured thereto fixedly a sun wheel 19. Surrounding the shaft 18 is an extended hollow shafting 20a having at its lower end a gearwheel 21 and carrying at its central portion a differential cage 20. Supported in the differential cage are planet pinions which gear with a fixed pinion 19 and a free pinion 22. The spindle 18 at its upper end drives an element 23 having jaw teeth 23a adapted to co-operate with the teeth 24a on a braking element 24. The disc 24 is held concentrically with the spindle 18 between friction washers 24b subjected to pressure of springs 25 whereby the brake element is held fixedly. The free sun pinion 22 of the differential has a hollow extension piece which carries a similar brake comprising a sleeve 26 having jaw teeth 26a adapted to coact with teeth 27a on a non-rotating disc 27 held between washers 27b and under the influence of a compression spring 25. Either brake may be applied by hand by a movement of the push rod 28 or such rod may be moved by a speed governor mechanism. The hand control includes a lever 34 connected by links 32 and 47 with the push rod. To prevent over running the blade roots are provided with toothed quadrants engaging racks which operate a central sliding rod 41 through suitable gearing. This rod is coupled at its inner end to a pivoted lever 42 on a cross shaft 43 which thus receives a motion proportionate to the pitch alteration. The cross shaft 43 carries a rod 44 which is coupled by a member 45 with the link 47 of the hand actuating gear. In the event of the blades reaching a maximum setting, rod 45 has an overriding influence on the lever 47 due to the fact that the member 32 includes a spring element 33. If therefore the lever 34 is placed in an operative position for engagement of one of the braking members 24 or 26, then the linkage 47, 31 can be moved and the brakes later on released automatically when the maximum setting is reached despite the position of the hand control lever. A pitch indicator pointer 51 is connected with the lever 47. In an alternative construction the differential and its gearing may be disposed within the hollow propeller shaft, or entirely within the hollow propeller boss. Specifications 381,936 and 403,897 are referred to.