GB496577A - Improvements in or relating to the manufacture of propeller blades - Google Patents

Abstract

496,577. Screw propellers. BLANCHARD, W. J. June 1, 1937, No. 15231. Convention date, June 10, 1936. [Class 114] [Also in Group XXII] Hollow blades for aircraft propellers are made by working a billet into root and blade portions and forging the blade portion to form leading and trailing edges defining an airfoil shape with a cavity therebetween by displacing metal from that part of the blade in which the cavity is formed. A round billet, preferably of alloy steel of the nickelmolybdenum type, is roughly shaped to the form shown in Fig. 3 by rolling forging, or the like in one or more steps. Figs. 4 and 8 show the sections along 4 ... 4 and 8 ... 8 respectively. The flow lines produced by this operation are lengthwise of the blade. The blank is then again heated and further shaped between forging dies 12, Fig. 18, to impart the desired pitch and produce the form shown in Fig. 11 having a central rib 20 and longitudinal cavities 16, 18. Another rib 22 is formed at the leading edge and rib 24 at the trailing edge. The outer faces 26, 28, 30 of the ribs, Fig. 14, define the outline of the back surface of the blade and merge into the shank at 35 and into a flat surface 34 at the tip. The bottoms of the cavities are preferably of straight section and the side walls of the cavities are preferably at right-angles to the bottom surfaces. The blank is then heat treated. The round part of the shank may be finished in a lathe and the shank then bored out to form a hollow part 48 with branches 50, 52, Fig. 21, leading to the cavities. The side and bottom surfaces of the cavities may be generated by planing, milling, or grinding. The surfaces 34, 35 and the faces 26, 28, 30, of the ribs are machined to receive the camber section forming the back of the blade. This section may be formed from a rolled sheet pressed in dies to the form B<1>, Fig. 24. The end of the forged section has a bevelled end surface 74, Fig. 33, shaped to receive the camber section which is secured to the forged section by fusion welding or, preferably, copper-hydrogen brazing, fillets being formed at 78, Fig. 34, during the brazing.