GB487084A - Improvements in or relating to propellers - Google Patents

Abstract

487,084. Screw propellers. UNITED AIRCRAFT CORPORATION. March 19, 1937, No. 8157. Convention date, March 26, 1936. [Class 114] A variable-pitch screw propeller in which the blades are carried by spider arms and held in a hub barrel, are controlled as regards pitch by members inside the barrel and inside a front hydraulic cylinder mounted on the hub. The propeller shaft 14 carries an extension 72 having a hexagonal flange 74 contiguous to the hexagonal nut on the end of a hollow member 42 which is screwed to the shaft at 20, and which holds the conical members 36, 38 which clamp the hub in position. The two hexagonal faces are held in locked engagement by an encircling member 78. Upon this central tube 72 is adapted to slide a piston 82 which is contained within a cylinder 64 screwed to the propeller hub at 60. The piston has, on its extended faces, two curved depressions 88, in which engage the bent ends of arms 92 which are secured to the blade root. The blades tend to set themselves under external forces in the low pitch position and are moved to high pitch position by the piston 82. In order that the piston shall not turn on its axis under the reaction imparted to the arms 92, it is provided with side recesses which move over pins 110, fitted to segmental sleeves 108 in the cylinder. These recesses 110, normally straight, may be given a curve opposite to that in the recesses 88. Within the recess 110 are screwed rods 136 carrying nuts 142 which, by contact with fixed side projections, limit the upper and lower pitch position settings. The arms 92 are secured to the blade root through a ring 104 which has inner and outer teeth of differing number to provide a vernier adjustment. The supply of pressure oil to the cylinder may be controlled by a centrifugal governor, in which case the governor 120 controls a valve 126 in a passage 124 leading to the hollow crankshaft ; the setting of the governor being controlled by hand-lever 134. In a modification, instead of the piston moving along the pins 110, it may be provided with a series of balls on either side of the depressions, whereby tilt of the piston is catered for. In a further arrangement, the space in the centre of the crankshaft is provided with vents and is thus adapted for acting as a crankcase breather when the lubricating pump of the engine is used as the source of power liquid for operating the piston.