Abstract: A pipe-coupling device comprises a joint body having an opening with external threads to receive a pipe, a locknut having internal threads engaged with the external threads of the joint body, an annular core member disposed within the locknut, and a plurality of locking members retained in apertures of the core member to be spaced circumferentially apart from each other. Upon tightening rotation of the locknut around the joint body, the internal conical surface of the locknut slidably contacts with the conical surfaces of the locking members so as to press the locking members radially inwardly, to cause the gripping portions of the locking members come into gripping engagement with the outer periphery of the inserted pipe, thereby strongly preventing withdrawal of the pipe from the joint body even when the pipe is made of hard material.

Abstract: A pipe-coupling device comprises a joint body 2 having an opening 2h with external threads 2d to receive a pipe P, a locknut 5 having internal threads 5a engaged with the external threads 2d of the joint body 2, an annular core member 6 disposed within the locknut 6, and a plurality of locking members 7 retained in apertures 6d of the core member 6 to be spaced circumferentially apart from each other. Upon tightening rotation of the locknut 5 around the joint body 2, the internal conical surface 5c of the locknut 5 slidably contacts with the conical surfaces 7a of the locking members 7 so as to press the locking members 7 radially inwardly, to cause the gripping portions 7b of the locking members 7 come into gripping engagement with the outer periphery of the inserted pipe P, thereby strongly preventing withdrawal of the pipe P from the joint body 2 even when the pipe is made of hard material.