GB530823A - Improvements in or relating to propeller blades - Google Patents

Abstract

530,823. Screw propellers. ALUMINUM CO., OF AMERICA. July 4, 1939, No. 19455. Convention date, July 18, 1938. [Class 114] [Also in Group XXII] In a process of making metal propeller blades an elongated blank is formed, e.g. by forging, with one or a pair of radially projecting fins through at least a portion of the length, is pierced to form an internal opening and is then flattened by pressure to form the fin or fins into one or both edges of the blade, these edges being thicker than the faces of the blade. A cylindrical blank of aluminium alloy or other metal or alloy capable of being forged, which may be produced by rolling or extrusion, is made conical at 3, Fig. 2, for a portion of its length by a series of one-way rolling passes. The blank is next rolled, pressed or hammerforged in dies 8, 9, Fig. 24, to draw out part of the tapered portion into fins 5, 6 having roughly the required spiral shape of the finished blade and adapted to form the trailing and leading edges respectively. The longitudinal flow lines of the metal are thus spread out into the fins without being broken. A hole is then formed in the blank, parallel at 13, Fig. 8 and tapering at 14, either by drilling or by piercing and then finish boring, the blank being made smaller in this case to allow for enlargement when piercing. The shank 4 is next swaged between dies or otherwise worked to thicken the walls thereof at the butt end and produce a tapered hole therein of smaller diameter, the dies being arranged to make the shank oval in two directions at right angles alternately. The shank is next machined and the end upset to form a securing flange thereon and before or after this operation the blade is placed in pressing or forging dies to flatten the conical portion 7 into the faces 22, 23, Fig. 29, merging into the solid leading and trailing edges 21, 20, formed from the fins 5, 6. The interior of the blade may be filled with deformable material during the pressing, such as sand or compressed gas. The blade is then trimmed, sized and heat-treated and is finished by machining, grinding and polishing and mounted on a hub.