GB524152A - Improvements in and relating to the manufacture of airscrew or propeller blades - Google Patents

Abstract

524,152. Making propeller blades. HIGH DUTY ALLOYS, Ltd., and HERON, J. A. Jan. 23, 1939, Nos. 2245 and 4275. [Classes 83 (ii) and 83 (iv)] Forging ; extruding.-In a method of making airscrew or propeller blades or like hollow articles with a closed end the metal is extruded through a die and over a mandrel by relative movement between the two to shape the i nterior of the blade in front of the mandrel, the crosssectional area of the blade being varied during extrusion by variation of the size of the die and a thickened root portion being produced on the blade. According to one method a heated billet 3 of light alloy, having a pre-formed central cavity 4, is placed in a container 1 and is acted upon by a two-part plunger 5, 6 whose mandrel portion 5 first fills the cavity 4 and then extrudes the billet rearwardly until its top surface reaches the shoulder 7 of the plunger. The plunger 6 then extrudes the end of the billet through a die 11 to produce a closed end 14 which is shaped internally by the continued advance of the mandrel 5. Further advance of the mandrel through the die extrudes the billet to form the hollow portion 17 and this advance is stopped whilst a thickened root portion 16 still remains in the cavity 2 of the container. The plunger is then replaced by a cylindrical plunger 30 fitting the cavity 2, or the mandrel 5 is removed from the plunger 6, and the thickened root is forced through the die to close this end as shown in Fig. 3. Alternatively the partially formed blade may be removed from the container 1 and the root closed or partially closed by hot swaging or other means. The die and mandrel are of elliptical section to produce a blade of approximately aerofoil section. The die 11 is furnished with movable segments 20, 21 which reduce the effective size of the die whilst the tip portion of the blade is being extruded, but are withdrawn progressively by mechanism 23 &c. during advance of the ram to vary the wall thickness of the blade along its length. The blade may be extruded into a mould 25 Fig. 4, in order to impart thereto a helical twist, or may be extruded in tapered or cylindrical form and given its final shape by stamping or pressing, with or without final machining, the root portion being finished as shown in Fig. 3. The mould is in two parts 24, 25 to permit removal of the finished blade and has a vent at 27. The interior of the blade may be filled with cellular and preferably inert material for balancing purposes. Specifications 518,037 and 524,146 are referred to.