GB536816A - Improvements in or relating to variable pitch propellers and bearings therefor - Google Patents

Abstract

536,816. Variable-pitch propellers. HOOVER, W. S. Nov. 9, 1939, No. 29760. Convention date, June 13. [Class 114] [Also in Group XXXIV] In a propulsion unit comprising a pair of oppositely rotating co-axial propellers, the members 34, 76, for charging the pitch angles of the blades are coupled together by a ball thrust bearing 70 to ensure similar and simultaneous pitch changing movements of the two propellers. As shown, the propeller hubs 22, 26, are mounted on co-axial shafts 18, 16, driven in opposite directions through gearing 14, 15, 17. The rods 34, 76, are slotted and engage pins 36 on the propeller blades so that axial movement of the rods rotates the blades to vary their pitch. The forward ends of the rods 34, 76, are secured to pistons 32, 42, respectively. The piston 42 carries the inner race 40 of the bearing 70 and the outer race 38 is secured to the adjacent end of the rod 34. A governor 50 connects a conduit 52 either with a source of pressure or with a drain. The spaces 66, 58 behind the pistons 42, 32, are connected to the conduit 52 through passages 64, 60, 54, and 56, 54' respectively. Hydraulic pressure such as lubricating oil under pressure acting on the pistons 42, 32, increases the blade pitch. Reduction of the blade pitch when the conduit is.opened to a drain is produced by centrifugal force. Lubricant is led to the bearing 70 from the space 66 through a duct 68. Oil leaking through the bearing is trapped in an annular chamber 74 and a pump returns this oil to the space 66: The pump is carried by the piston 42 and its plunger 78 is reciprocated by a cam 80 formed on the outer race ring 38. In a modification, the connection between the rods 34, 76, and the propeller blades is a rack and pinion, and the piston 32 is arranged so that either side thereof can be opened up to pressure oil or to a drain.