Abstract: An internal circulation ball screw comprises a nut, a screw, a plurality of return assemblies, and a plurality of balls. The nut is threaded on the screw through the balls. An arc-shaped curving surface is formed on the edge of a tip of an outer thread of the screw and is to be connected to a return path of the return assemblies. The radius of the arc-shaped curving surface of the screw is between 9%-17% of the diameter of a ball, and each of the outer threads of the screw has three different curvature sections formed at the positions where the balls climb over, which are climbing curvature section, fillet curvature section and tip curvature section. By such arrangements, the internal circulation ball screw can allow the balls to move more smoothly and stably, and keep the balls from falling off or deflecting.

Abstract: The elaborately calculated method of the present invention using photoelastic analysis for finding contact relation between ball and track is characterized in that a photoelastic plate having a semi-circular section is used in measurement by observing contrast of stripes appeared thereon in stead of observing track profile from the plucked image of the object in conventional technique therefore being released from shortcoming of inaccurate measurement result due to vagueness of profile of plucked image.

Abstract: The elaborately calculated method of the present invention using photoelastic analysis for finding contact relation between ball and track is characterized in that a photoelastic plate having a semi-circular section is used in measurement by observing contrast of stripes appeared thereon in stead of observing track profile from the plucked image of the object in conventional technique therefore being released from shortcoming of inaccurate measurement result due to vagueness of profile of plucked image.