Patent ID: 8118331

Claim:
A non-bolt joint structure comprising: a fluid conduit having a receiving opening section; a polyethylene pipe having an insertion opening section, the insertion opening section being configured to be inserted into the receiving opening section, and an inner circumference of the receiving opening section including a means for engaging an outer circumferential surface of an engaged portion of the polyethylene pipe to connect the fluid conduit to the polyethylene pipe without using bolts and to prevent the polyethylene pipe from disengaging from the receiving opening section; a packing ring inserted between the receiving opening section and the insertion opening section to seal between the receiving opening section and the insertion opening section; and a tubular metallic inner core fit into an inner circumference of the insertion opening section of the polyethylene pipe; wherein the inner core includes a bulge portion that is in a plastically deformed state, a cross-sectional shape of the bulge portion along an axis of the inner core being curved to bulge in an outward radial direction toward the fluid conduit from the axis of the inner core; wherein the polyethylene pipe is in a deformed state so as to include a bulge portion, the bulge portion of the polyethylene pipe being formed as a result of the bulge portion of the inner core and having an inner circumferential surface that is in close contact with an outer circumferential surface of the bulge portion of the inner core, a cross-sectional shape of the bulge portion of the polyethylene pipe along the axis being curved to bulge in the outward radial direction, wherein the bulge portion of the inner core includes a first tapered portion, a diameter of the first tapered portion gradually expanding as the first tapered portion extends into the fluid conduit in a longitudinal direction from an opening in the receiving opening section; and wherein the engaged portion is formed on the outer circumferential surface of the bulge portion of the polyethylene pipe by the bulge portion of the polyethylene pipe bulged in the outward radial direction, a diameter of the engaged portion gradually expanding as the engaged portion extends into the fluid conduit in the longitudinal direction from the opening, and the means for engaging by engaging the outer circumferential surface of the engaged portion of the polyethylene pipe prevents the polyethylene pipe from disengaging from the fluid conduit.