this paper researches the relationship between the direction of involute elliptic gear profile and the polar radius of elliptic gear's pitch curve.
本文研究了渐开线椭圆齿轮齿廓方向与椭圆齿轮极径方向之间的关系;
in other words, if according to the proportion of production with a radius of 30 cm of the globe, so its equatorial radius and the polar radius is only a difference of 1 mm!