Socket for pipe coupling

A socket for a pipe coupling, comprising:

• a hollow cylindrical socket main body comprising a tip end in which a plug insertion port capable of receiving a plug including an engagement groove in an outer periphery of the plug is formed, a rear end in which a piping connection portion attachable to a piping to be connected to the plug is formed, and an inner peripheral surface which defines a fluid channel connecting the plug insertion port to the piping connection portion and an inner space;
• at least one locking element which is supported in the tip end of the socket main body so as to be projected/retracted in a centripetal/centrifugal direction with respect to the socket main body and which can engage with the engagement groove, when the plug is inserted into the plug insertion port;
• a sleeve for plug connection which is attached to the outer periphery on a tip-end side of the socket main body and which can move forwards/backwards and which moves forwards to move the locking element toward a centripetal side and to lock the plug and which moves backwards so that the locking element can move toward a centrifugal side;
• a valve main body which is disposed in a concentric form at a predetermined interval from the inner peripheral surface of the socket main body and whose tip end is fixed to the socket main body and which comprises a cylindrical member including a tip end provided with a port fitted into the tip end of the plug, closed rear end, and cylindrical wall extending between the tip and rear ends to define the inner space, a channel hole formed in the cylindrical wall on a rear-end side, and a purge hole formed before the channel hole;
• a cylindrical seal member which is attached between the socket main body and valve main body so as to be rotatable between a first position and a second position distant from the first position and which seals between the socket main body and valve main body and which opens the channel hole and closes the purge hole in the first position to connect the inner space of the valve main body to the fluid channel on a rear side of the cylindrical seal member and which closes the channel hole and opens the purge hole in the second position to connect the inner space of the valve main body to the inner space of the socket main body on a front side of the cylindrical seal member;
• a sleeve for valve opening/closing operation which is rotatably attached to the outer periphery of the socket main body;
• and
• a connection pin which integrally connects the sleeve for valve opening/closing operation to the cylindrical seal member,
• the socket main body having a guide groove which is formed through the socket main body and which extends in a circumferential direction to guide the connection pin.