Adapter coupling

A combination, comprising:

• a plurality of segments attached to one another end to end in a preassembled state by fasteners to form a loop around a central space, wherein in said preassembled state, said plurality of segments are supported in spaced relation while attached to one another to allow insertion of a first pipe element into said central space, each of said segments comprising a first side and a second side, wherein a channel is disposed between the first and second sides of the plurality of segments, wherein the channel extends circumferentially around and faces said central space;
• a flexible, resilient sealing ring positioned in said channel, the sealing ring comprising first and second lobes that each extend radially inwardly to define first and second ring inner seal surfaces, respectively;
• and
• a tube comprising:
• a first end disposed and retained within the central space while the segments are in the preassembled state,
• a first protrusion extending radially outwardly and disposed proximate the second sides of the plurality of segments, wherein the first protrusion limits an extent to which the first end of the tube can extend axially into the central space,
• a second protrusion extending radially outwardly and disposed within the central space while the segments are in the preassembled state, wherein the second protrusion is axially disposed between the first protrusion and the first end, wherein the second sides of the plurality of segments and the first lobe of the sealing ring are both axially disposed between the first and second protrusions, wherein the first lobe is axially disposed between the second protrusion and the second sides of the plurality of segments, and the second protrusion extends radially outwardly farther than an inner radial extent of the first lobe such that the second protrusion and first lobe help retain the tube within the sealing ring while the segments are in the preassembled state, and
• a sealing surface disposed between the first and second protrusions on an outer surface of the tube;
• wherein the combination is shaped and configured such that an end of the first pipe element may be axially inserted into the central space, and
• wherein the combination is shaped and configured such that once the end of the first pipe element is properly inserted into the central space, the fasteners can be tightened so as to draw the plurality of segments toward one another and the central space and thereby cause the first ring inner seal surface to sealingly engage the sealing surface of the tube, and the second ring inner seal surface to sealingly engage a sealing surface of the first pipe element.