O-ring push-pull pipe joint

Abstract

A coupling device is used for joining two pipes. Each end of the coupling has a pair of adjoining grooves in its inner surface. Each groove has at its largest diameter a substantially flat portion located at its innermost end and then tapers in the direction of the coupling end. At the junction between the two grooves, the diameter of outermost groove is greater than the diameter of the innermost groove, forming a small circumferential ridge. An O-ring is initially set in the innermost groove and is compressed as the pipe is pushed into the coupling. The O-ring is further compressed as it rolls down the ramp of the inner groove as the pipe is partially retracted from the coupling. As the O-ring is pulled past the circumferential ridge between the grooves, it expands into the flat portion of the outer groove, forming a seal between the pipe and the coupling and a positive indication of sealing. The flat portion of the outer groove permits the entire O-ring to roll over the ridge before compression of the O-ring by the tapered portion of the outer groove. After installation, forces tending to push the pipe out of the coupling cause the O-ring to roll against the steep incline of the tapered surface of the outer groove, resulting in further compression of the O-ring, thereby tightening the seal.