GB220673A - Improvements in spars or struts and longerons for use more particularly in aeroplaneconstruction, and in blades or aeroplane propellers - Google Patents

Abstract

220,673. Coupland, E., and Trevitt, F. J. Dec. 10, 1923. Posts and columns; screw propellers.- A longeron, strut, propeller blade, &c. is produced from a metal tube by an operation which performs an alteration of the dimension of the perimeter of the tube by spinning combined with a subsequent operation for altering the crosssectional shape of the tube. The invention is described with reference to the construction of a metal propeller blade. A tube is first reduced to the form shown in Fig. 2 by turning, rolling, or spinning, if desired the gauge of the tube being made to vary at any particular cross-section. Alternatively the parts subjected to the greatest stresses may be strengthened by placing inside the tube one or more additional thicknesses of metal. The tube is then bulged to the form shown in Fig. 3 by internal spinning. This alteration of the perimeter may also be produced by spinning down a shorter tube of the shape shown in Fig. 4, the tube being extended to the correct length by the process. The bulged tube is then given the desired cross-sectional shape by pressing it between external dies of the shape shown in Figs. 9 and 10, or by means of internal dies b, b<1>, b<2>, Fig. 11, the die b being pressed in after the insertion of the dies b<1>, b<2>. The blade is finished in suitable exterior dies, if desired, before the dies b, b<1>, b<2> are removed. The tip of the blade is closed by welding or riveting and the other end spun or staved open for securing to a boss. A two-bladed propeller may be produced from a single tube in a similar manner. Fig. 8 shows a method of securing a collar c on a blade &c.. the tube d being expanded into a groove e in the collar. Alternatively the tube d may be slightly expanded on either side of the collar.