Pipe coupling socket

A pipe coupling socket having a piping junction at one end thereof and a plug inlet at the other end, in which a piping passage and the plug inlet are internally connected by means of a through passage of a built-in ball valve, comprising:

• a socket body having therein a valve chamber, one end of which communicates with the piping passage and the other end of which communicates with the plug inlet, the ball valve located for rotation in the valve chamber, and a valve control sleeve which is fitted on the outer periphery of the socket body and which advances to open the ball valve and retreats to close the ball valve;
• a locking element which is supported on the distal end portion of the socket body for movement in the centripetal and centrifugal directions and engages an engaging groove formed on the outer periphery of a plug inserted in the plug inlet, thereby locking the plug;
• a plug connecting sleeve which is fitted on the distal-side outer periphery of the socket body and which advances to move the locking element to the centripetal direction, thereby locking the plug, and retreats to allow the locking element to move to the centrifugal direction, thereby unlocking the plug;
• first lock means which prevents the valve control sleeve from advancing when the plug connecting sleeve is situated in a retreated position;
• and
• second lock means which prevents the retreat of the plug connecting sleeve and the advance of the valve control sleeve when the plug connecting sleeve and the valve control sleeve are situated in an advanced position and a retreated position, respectively, and third lock means which prevents the retreat of the plug connecting sleeve and the valve control sleeve when the plug connecting sleeve and the valve control sleeve are situated in their respective advanced positions.