GB219477A - Improvements in screw propellers - Google Patents

Abstract

219,477. Leitner, H. July 10, 1923. Screw propellers.-Hollow metal detachable screw propeller blades are constructed from plates or tubes which are folded around one another at the butt end and decrease in width until a joint is formed along the centre of the blade. Two plates a, b, Figs. 1 and 2, are pressed to form the trailing and leading portions of the blade, the parts being riveted together at e along the middle of the faces. The plates at the root ara wide enough to be formed into complete cylinders, the cylindrical part c of the. portion a fits within the cylindrical part d on the portion b and is riveted or otherwise secured thereto. In a modification, the leading and trailing edges are straight and the blanks before pressing are formed with a V opening at the butt end, so that the root of the blade is of tapered form. Instead of plates, slightly conical tubes a, b, Fig. 8, may be used, each tube being suitably flattened to aerofoil shape and being cut away for three-quarters of the length and slightly less than half the width so that an overlapping joint at e is provided. The tubular ends are bent round and secured to a flange l on a fitting k which constitutes the cylindrical root. A longitudinal internal stiffening girder connecting the two faces may be added to the preceding constructions. In one form, the girder is constructed from strips o, p, Figs. 10, which are of channel form with abutting webs riveted at q, the flanges of the channels being enlarged and brought into curved form at the butt ends. The blade plates may be of taper gauge and/or made up of laminations.