Coupling for helically corrugated spiral pipe

Claim 1

A coupling for providing a substantially soil tight joint between abutting ends of helically corrugated, spiral pipe which comprises: (a) a pair of flexible, pre-formed strips, each strip having a top and bottom surface, said bottom surfaces having helical corrugations which are of a similar pitch and depth as said pipe's corrugations, each strip being circumferentially continuous, each strip fitting about one of said pipe's outer circumference near its abutting end with said strip's helical corrugations and mating with said pipe's corrugations, and (b) a tightening band having a width sufficient to fit over both of said strips positioned on said pipes and having clamping means to clamp said strips in radial compression between said band and said pipes, said band having a bottom band surface in contact only with said top strip surface, said bottom band surface being substantially flat in those areas in contact with said top strip surface, said band, strips and clamping means being all so constructed and arranged that said strips are free to expand in an axial direction anywhere between their said top and bottom surfaces when said strips are radially compressed into engagement with said pipes and inner band surface by said clamping means.