| 摘要 |
PURPOSE:To secure an accurately formed ball valve, by molding a pipe having a bearing member into a sphere, and machining a groove, making a flat surface to pass the center of this sphere a central surface, on an outer surface of the bearing member for finishing. CONSTITUTION:A long aperture 2 long in the circumferential direction is installed in the axial central part of a stainless steel pipe 1. A bearing member 3 is fitted in this long aperture 2 and joined together with each other by means of welding. A pipe material 6 is housed in a mold having a spherical space, while it is pressurized from both sides in the axial direction and deformed into a sphere 1' having a circular opening 15 at both sides in the axial direction. The pipe material 6 is inserted into the sphere 1' from the opening 5 and both ends of this pipe material 6 is welded to both openings 5. A longitudinal section of a bottom surface of a groove 7 for stem use should be a circular arc making a point on a center surface of the groove 7 the center.
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