Month in the Patent Office

Abstract

The blades of an airscrew or spars and similar hollow structural parts of aircraft are formed of two shell sections of wood laminæ joined together with a moisture‐resisting adhesive, each shell section forming in the case of a blade substantially one face of the blade and being made by assembling very thin wood laminæ between shaped dies, which dies may be heated as well as pressed together. The wood laminæ is preferable less than one millimetre in thickness and the laminæ may be assembled so that parts which take higher stresses are more highly compressed. The laminæ 9 are treated with a resin and pressed between the dies, 7, 8 which have tubes 10 for conveying a heating medium. After pressing, the parts may be clamped together while the shell member is setting, and finally the free edges 11 are cut away. If desired, the shell‐like members 2, 3 may be strengthened by inner longitudinal ribs 22 and the parts are subsequently united by gluing at the leading and trailing edges. For the purpose of securing the blade root within a cylindrical socket, it may have an inner stiffening tube 15 and an outer hardwood sleeve 17 to which a metal sleeve 16 is attached. Alternatively, the hardwood sleeve and metal sleeve are both placed inside and outer clamping sleeves are employed. The shell members 2, 3 may be enclosed in a metal sheeting 23, 24, the edges of which are joined by welding or by interlocking the edges 25. The leading edge may be formed by a separate member 30 dovetailed as at 34 into the outer shells, and such member may be formed with a rubber tip 37 or be wholly of rubber. The resistance to bending stresses may be increased by loading the blade tip either by adding weight or using material of high density. The wood laminæ may be interleaved with laminæ of other suitable pliable material such as fabric or metal gauze.

Citation

(1939), "Month in the Patent Office", Aircraft Engineering and Aerospace Technology, Vol. 11 No. 6, pp. 259-260. https://doi.org/10.1108/eb030507