Abstract: An insertion member provided with a male thread on the peripheral surface thereof is inserted through an opening of a receiving member. The insertion member is fastened by a fastening member provided with a female thread on the inner surface thereof. A first O-ring is provided between the insertion member and the fastening member, and a second O-ring is provided between the fastening member and the receiving member. When viewing each circular cross-section of the first and second O-rings along a surface parallel to a moving direction of the fastening member at the point of fastening the insertion member by rotating the fastening member, a first point of each circular cross-section is pressed against a surface perpendicular to the moving direction, and a position displaced from a second point opposite to the first point of each circular cross-section is pressed against an inclined surface inclined to the moving direction.

Abstract: An insertion member provided with a male thread on the peripheral surface thereof is inserted through an opening of a receiving member. The insertion member is fastened by a fastening member provided with a female thread on the inner surface thereof. A first O-ring is provided between the insertion member and the fastening member, and a second O-ring is provided between the fastening member and the receiving member. When viewing each circular cross-section of the first and second O-rings along a surface parallel to a moving direction of the fastening member at the point of fastening the insertion member by rotating the fastening member, a first point of each circular cross-section is pressed against a surface perpendicular to the moving direction, and a position displaced from a second point opposite to the first point of each circular cross-section is pressed against an inclined surface inclined to the moving direction.

Abstract: A waterproof structure for a tightening section where a first member (1) having a screw hole (1a) with a bottom and a second member (2) having a screw insertion hole (2a) are fastened with a screw (4) that is inserted into the screw insertion hole (2a) and screwed to the screw hole (1a). The screw (4) is a flat head screw, and an annular groove (3b) is formed in the outer surface of a spacer (3) having an insertion hole where recessed circular conical surface (3a) is formed. The spacer (3) is fitted in the screw insertion hole (2a) to be in surface contact with a circular conical surface of a head of the flat head screw. The annular groove (3b) is coaxial with the recessed circular conical surface (3a).

Abstract: A waterproof structure for a tightening section where a first member (1) having a screw hole (1a) with a bottom and a second member (2) having a screw insertion hole (2a) are fastened with a screw (4) that is inserted into the screw insertion hole (2a) and screwed to the screw hole (1a). The screw (4) is a flat head screw, and an annular groove (3b) is formed in the outer surface of a spacer (3) having an insertion hole where recessed circular conical surface (3a) is formed. The spacer (3) is fitted in the screw insertion hole (2a) to be in surface contact with a circular conical surface of a head of the flat head screw. The annular groove (3b) is coaxial with the recessed circular conical surface (3a).