Pipe joints are already known which comprise a pair of tubular joint members each having a gasket holding annular protuberance on an abutting end face thereof, an annular gasket interposed between the abutting end faces of the respective joint members, and a nut for joining the joint members together. The joint members, annular protuberances and gasket are equal in inside diameter, and each annular protuberance is adapted to contact the inner edge portion of the gasket over the entire circumference thereof.
With reference to FIGS. 6 and 7 showing the conventional pipe joint, indicated at 42 is the joint member, at 44 the gasket holding annular protuberance and at 45 the annular gasket.
With the conventional pipe joint described, each annular protuberance 44 is adapted to come into contact with the inner peripheral edge portion of the gasket 45 over the entire circumference thereof to make the protuberance 44 flush with the gasket 45 when the nut has been tightened up and to eliminate any liquid trapping recess from the pipe joint.
In the case of the conventional pipe joint described, the force acting on the gasket holding annular protuberance 44 when the nut is tightened has not only an axial (i.e., rightward in FIG. 6) component but also an inward (downward in FIG. 6) component as seen in FIG. 6, so that the protuberance 44 deforms inward. On the other hand, the gasket 45 deforms most markedly at the inner edge portion thereof with which each protuberance 44 comes into contact first. Consequently, there arises the problem that the protuberance 45 and the inner edge portion of the gasket 44 become separated, forming a liquid trapping annular recess S between the protuberance 44 and the gasket 45 when the pipe joint is tightened up as shown in FIG. 7.