and the on off valve chamber 10 normally communicate through a space between adjacent blades or bores formed on the disc the flow of the fluid such as a gas is not prevented by the on off valve 11 the on off valve 11 has a compression coil spring 21 surrounding the sleeve 19 and disposed between the abutment 14 and the supporting means 20 the compression coil spring 21 normally biases the on off valve body 12 toward said engaged end of the connecting pipe 5 a check valve 22 having a ball 23 a valve seat 24 disposed on the ball 23 close to the on off valve chamber 10 and a weak compression spring 25 disposed between the valve seat 24 and the supporting means 20 is disposed in the check valve chamber 9 the check valve 22 serves to block the fluid passage 8 with the ball 23 when fluid pressure is not applied to the connecting pipe 5 or it is weaker than the biasing force of the spring 25 as shown in fig3 in the socket body 3 a first packing chamber 26 a second packing chamber 27 and a cylindrical bore 28 for receiving the plug end portion are continuously formed in the order as viewed from the internal screw threads 4 an annular packing 29 of rubber or the like is placed in the first packing chamber 26 an annular sealing member 30 such as an o ring.