Coupling and circumferential groove shape

A pipe element for use with a pipe coupling comprising a plurality of segments attached to one another end to end surrounding a central space for receiving said pipe element, at least a first arcuate projection positioned on one side of said coupling and facing an axis extending through said central space, said arcuate projection having a semi-circular cross section taken parallel to said axis, said pipe element comprising:

• a sidewall surrounding and defining a bore, said sidewall having an outer surface facing away from said bore;
• a groove extending radially inwardly from said outer surface of said sidewall, said groove extending circumferentially around said bore and positioned axially between respective first and second portions of said outer surface of said sidewall, said groove comprising:
• a first side surface contiguous with said outer surface and a first floor surface, said first side surface and said first floor surface together having a first 90° circular arc when viewed in cross section taken parallel to an axis extending coaxially through said bore;
• a second side surface contiguous with said outer surface and a second floor surface, said second side surface being in spaced relation to and facing said first side surface, said second side surface and said second floor surface together having a second 90° circular arc when viewed in cross section taken parallel to said axis extending coaxially through said bore;
• and
• a third floor surface contiguous with both said first and second floor surfaces, said third floor surface comprising a flat surface;
• wherein
• said first 90° circular arc begins at said first portion of said outer surface and extends to said first floor surface,
• said second 90° circular arc begins at said second portion of said outer surface and extends to said second floor surface, and
• said groove is configured to receive said first arcuate projection of said coupling.