Connection device

A CO2 gas seal device comprising:

• means (11, 13) for sealing the CO2 gas;
• and
• first and second connecting hollow members (7, 9),
• the connection of said first and second connecting hollow members (7, 9) forming a connection part having a hollow part for passing the CO2 gas through it between said first connecting hollow member and said second connecting hollow member and forms a groove (19G, 17G1, 17G2, 19G1) at a gas leakage part in the connection part,
• said groove having a first part and a second part connected to the first part and having a sectional area smaller than that of the first part along the direction of leakage of said CO2 gas, the second part has a tapered surface inclined so that its thickness becomes smaller along the direction of leakage of said CO2 gas,
• said gas sealing means having an O-ring (11) made of rubber arranged at the first part of said groove and one backup ring (13) made of 46Nylon arranged at the second part of said groove,
• said backup ring having an inclined surface contacting the tapered surface of the second part of said groove, being enlarged in a diametrical direction at the second part of said groove by said CO2 gas, the deformation of said O-ring (11), and a pressing action by the movement, and moves over the second part of said groove,
• an angle of said inclined surface of said backup ring (13) being larger than the angle of the tapered surface of the second part of said groove, the inclined surface of the first gas seal member is crushed at the time of the pressing action by said CO2 gas to further narrow the clearance of said second part, and
• a front end of the second part of said groove being provided with a clearance from which said backup ring can be projected.