公开(公告)号：US11795986B2

公开(公告)日：2023-10-24

申请号：US17160151

申请日：2021-01-27

Applicant: TOPURA CO., LTD.

Inventor： Minoru Sugiyama ,  Shigeto Mori ,  Mayumi Matsuno ,  Naoki Horiuchi

IPC: F16B25/00 ,  F16B5/00

CPC classification number: F16B5/0052

Abstract: An external screw member includes a parallel screw portion and a tapered screw portion provided on a side further toward a tip end than the parallel screw portion, and a plurality of sets of step portion and a transition screw thread portion are provided on at least one of the parallel screw portion and the tapered screw portion, the step portion having a reduced thread height in a radial direction and the transition screw thread portion gradually increasing in diameter from the step portion in an anti-driving rotation direction so as to reach a thread height of a normal screw thread portion. A top portion of the transition screw thread portion is positioned at an offset toward a pressure side relative to a position of a regular screw pitch in a minimum diameter portion of the step portion, and transitions to the regular screw pitch in the anti-driving rotation direction.