US Patent 8651530 Mechanical fastener for clamp

A pipe coupling including an annular clamp having an opening at at least one end of its axial length for inserting therein a pipe, the annular clamp including two clamp members, an annular seal disposed in the annular clamp, and a mechanical fastener that includes a threaded shaft with a washer flange, the washer flange having a lower rim, wherein when nuts are tightened on both ends of the threaded shaft, the lower rim bites into the annular seal.