Abstract: An olefin is polymerized by using a catalyst consisting essentially of (A) a solid catalyst component containing a magnesium halide and a titanium chloride, (B) an organic aluminum compound, and (C) an ether compound represented by the formula: R.sup.1 R.sup.2 R.sup.3 C(OR.sup.4), R.sup.1 R.sup.2 C(OR.sup.4).sub.2 or R.sup.1 C(OR.sup.4).sub.3. The catalyst has high catalytic activity and high stereoregularity as well as good activity endurance and is especially suitable for production of block copolymers.

Abstract: An improvement of a globoid worm gear generating method based on the "basic member gear theory" and the "secondary action theory" both proposed by the same inventors is disclosed. In one form, the surface of a globoid worm generating tool is defined as the tooth surface of an intermediate gear by a conical surface whose semivertical angle .UPSILON., 0.degree..ltoreq..UPSILON..ltoreq.90.degree.. In another form, the surfaces of a globoid worm gear generating tool are defined by two conical surfaces whose semivertical angles are equal and satisfy the above condition and whose major axes as well as bottoms are coincident with each other so that both tooth surfaces of a worm may be simultaneously generated.

Abstract: A system for shutting down a hydraulic machine having a runner mounted on a rotating shaft and a stationary part or parts surrounding the runner, comprising a rod or rods installed on the stationary part or parts opposite to the periphery of the runner, each rod being yieldable to the pressure of the runner, in case of the latter's deformation or off-center displacement, so as to sense the gap between the runner and the stationary part, a member or members each adapted to be actuated when the stroke of the associated sensing rod has exceeded a predetermined value, and a shutdown device operable upon actuation of the said member.