Month in the Patent Office

A hollow airscrew blade is formed from preformed complementary moulded plastic sections, the joint lines of which extend along the leading and trailing edges, the sections being homogeneously united under pressure. The plastic material comprises resinous or similar material of the thermoplastic or thermosetting type such as impregnated fibres of cotton, linen, or wood or laminated sheets of wood veneer and resin. The preformed sections are moulded between pairs of primary and secondary dies produced from a master pattern. Preformed struts 25 may be incorporated in the blade or a permanent core of expanded rubber. The shank of the blade may be “up‐ended” by means of an axially moving end mould.