| 摘要 |
<p>412,951. Screw propellers. SELMAN, G. S., and MANGANESE BRONZE & BRASS CO., Ltd., Caxton House, Tothill Street, London. Dec. 3, 1932, No. 34326. [Class 114.] A screw propeller blade is provided with a curved back which from the point of maximum thickness to the leading edge of the blade is geometrically similar and substantially elliptical for all the cross-sections, the ratio of the height te of the curvature above the helical datum-line to the intercept le on the width of the blade of the ordinate at the maximum thickness measured from the leading edge being 0À26 with a tolerance of + or -0À02. In addition, the intercept is from 25 to 29 per cent of the complete width L of the blade at that section. The values adopted are associated with camber ratios t by L of 0À064 to 0À075. Where, as at the root, this ratio is exceeded the nose is lifted and the driving face is curved toward the nose. Toward the tip it may be necessary to increase the thickness in order to preserve the ratio even though the blade width narrows toward the tip. Immediately adjacent the leading edge the nose section is radiused or trimmed to connect the back and front faces.</p> |
