Socket and pipe fitting including same

A socket, comprising:

• a base part having a cylindrical shape;
• a valve body housed in the base part;
• an incorporated plug part housed in the base part, having a front end in an axial direction in contact with the valve body, and including an engaging portion protruding outwardly in a radial direction;
• an engaged part housed in a hole portion penetrating the base part outwardly in the radial direction, and including a first engaged portion on a front side in the axial direction and a second engaged portion on a rear side in the axial direction, the first engaged portion being configured to be engaged with the engaging portion of the incorporated plug part, the second engaged portion being configured to be engaged with the engaging portion of the incorporated plug part;
• and
• a plurality of steel balls housed in housing holes that penetrate through a vicinity of a rear end of the incorporated plug part in the radial direction,
• wherein in an inserted state where an airtight condition is established with a plug inserted, a front section of the plug is inserted in a rear section of the incorporated plug part, an engaging portion of the plug is engaged with the steel balls pushed out inwardly in the radial direction, and the engaging portion of the incorporated plug part is engaged with the first engaged portion of the engaged part,
• when the engaged part is pressed inwardly in the radial direction, the engaging portion of the incorporated plug part is disengaged from the first engaged portion, moved toward the rear side, and engaged with the second engaged portion, so that the socket shifts to a half-inserted state where a non-airtight condition is established, and
• when the pressing of the engaged part is released, the engagement between the engaging portion of the incorporated plug part and the second engaged portion is released, the incorporated plug part is moved toward the rear side, and the steel balls are moved outwardly in the radial direction, thereby releasing the engagement between the engaging portion of the plug and the steel balls, so that the socket shifts to a non-inserted state where the plug is capable of being pulled out, and
• wherein the base part comprises an outer part and an inner part that is separate from the outer part and housed completely inside the outer part, and a portion of the inner part of the base part, which is rigidly connected to the remainder of the base part, is placed inside the engaged part so as to be at a same position with respect to the axial direction in the inserted state, the half-inserted state and the non-inserted state, and
• the portion of the inner part placed inside the engaged part is in contact with both the engaged part and the incorporated plug part.