GB754887A - Improvements in or relating to one-piece hollow propeller blades and method of making the same - Google Patents

Abstract

754,887. Making screw propellers. UNITED AIRCRAFT CORPORATION. June 30, 1954 [Nov. 20, 1953], No. 19159/54. Classes 83 (2) and 83 (4). Forging; rolling.-In a method of making hollow propeller blades a hollow blank 16, Figs. 8, 9, formed with longitudinal fins 18, 20 in the region of the leading and trailing edges to be formed is hot and cold worked as by rolling over a mandrel to produce the required length and aerofoil section, the ribs being subsequently removed. The hollow blank 16 may be formed by piercing an elliptical billet 12, Fig. 5, while enclosed in a die 28. The ribs 18, 20 and the root end 24 may be simultaneously formed by the die 28 during the piercing process or may be subsequently machined thereon. Alternatively the blank may be formed by piercing a round or rectangular billet which is subsequently machined inside and out and placed on a mandrel and forced through a drawing die or roller dies to form the elliptical shape and the fins. In the next stage the heated blank is placed on a mandrel 42, Fig. 6, of a push bench actuated by an hydraulic ram 44 and is elongated and formed to the required approximate aerofoil section and taper by pairs of rolls 52 spaced so that the work is in engagement with only one roll pair at a time. The shape of the rolls 52, Fig. 7, is arranged so that a gap is maintained in the region of the leading and trailing edges for shaping the ribs which may be free to expand laterally or are engaged by fixed side guides 55. After completing the roll passes the blank is held at the shaped root end 24 by grippers 54 which strip the blank from the mandrel 42 as it is withdrawn. After heattreatment the cold blank is further elongated by further rolling passes. The blank 62, Fig. 16, is then machined at the root end 64 to the required shape and the end 66 is flattened between dies while the blank wall is supported by internal hydraulic or inert gas pressure. The leading and trailing edges are then machined or ground to the required aerofoil section, the ribs 58, 60, Figs. 24, 26, being wholly or partially removed. The blade is finally heated and formed to the required shape including twist between dies while the interior of the blade is filled with nitrogen under pressure.