Patent ID: 7243954

Claim:
A pipe joint with earthquake-proof function, wherein a lock ring is accommodated in a lock ring accommodating groove formed at an inner surface of a socket of one pipe configuring said pipe joint, a projection formed at an outer periphery of a distal end of a spigot of another pipe, configuring said pipe joint and being inserted to said socket, is configured to be able to engage with the lock ring from the socket inner side, disengagement of the spigot from the socket is prevented as said lock ring is configured to be able to engage with said accommodating groove, a tapered surface converging toward the opening side of the socket is formed on at least one of a portion of said lock ring engaging the accommodating groove and a portion of said accommodating groove engaging the lock ring, when a disengagement prevention force in a pipe axial direction for preventing the spigot from being disengaged from the socket by said engagement is transmitted from the accommodating groove to the lock ring through the tapered surface, a line of action of a component force of said disengagement prevention force in a direction perpendicular to said tapered surface passes the opening side of the socket of a contacting point between a socket bottom end part of the lock ring and the outer periphery of the spigot along the outer surface of the spigot, the tapered surface is formed at the portion of the lock ring engaging the accommodating groove, and an inclination angle of the tapered surface with respect to the spigot outer surface changes in accordance with a distance in a radial direction from the spigot outer surface to said engaging portion, and the inclination angle of the tapered surface with respect to the spigot outer surface gradually decreases as the distance in the radial direction from the spigot outer surface to the accommodating groove engaging portion increases.