Pipe joint

a pipe joint having a one-piece socket assembly provided with an annular groove for receiving a rubber ring seal, the internal surface of said socket comprising tow conic parts which axially diverge from the circumferential edges of said groove to the opposite directions along two conic surfaces with identical vertical angles, respectively, such that said two conic parts formed along said two conic surfaces, respectively, pass through a circle having a larger diameter than a pipe to be inserted and imaginarily provided on a section taken along the outside circumferential edge of said groove with its center on the axis of said socket and which have vertexes with identical vertical angles on the axis of the socket at the opposite sides of said section and diverge from the circumferential edges of said groove inwardly and outwardly, respectively, wherein said vertical angle is 2.theta..degree. and has the following relationship when the inclination of said pipe to be inserted is assumed to be .theta..degree.:

• D = d/cos.theta..degree.
• wherein D is the inside diameter of the socket at the section taken along the outside circumferential edge of the groove and d is the outside diameter of the pipe to be inserted and wherein .theta..degree. is greater than 4.degree..