GB507408A - Improvements in or relating to screw propellers - Google Patents

Abstract

507,408. Screw propellers. FRASER, K. G. Sept. 11, 1937, No. 24818. Convention date. Sept. 15, 1936. [Class 114] The blades of a variable pitch screw propeller, on.which the aerodynamic and centrifugal moments co-operate to vary the pitch, have a distribution of the mass with respect to the plane of rotation ,and pivot axis is such that the centrifugal moments operate in a sense tending to increase the pitch for small values of V/n.d and in a sense tending to decrease the pitch for large values of V/n.d. The gravity axis of the blade is substantially co-incident with the pivot axis thereof but is gradually offset in a substantially straight line toward the tip so as to be lagging with respect to the pivot axis in the direction of rotation and leading with respect to the plane of rotation in the direction of travel. The blades 10 are rotatably mounted in their boss upon an axis PP and the central gravitios of the sections are disposed along a line GG having the disposition referred to above. To provide a further'balance of the moments acting upon the blade there may be disposed at the blade root weights 11 clamped thereto by bolts 13. For the purpose of setting, the blade root and the weight are given suitable markings 43. The boss driven from the shaft by a flexible means which permits a slight movement in and out of the plane of rotation as well as tangentially therein.