Pipe lap joint with collapsible sealing zone and band clamp

Claim 1

In a coupling for a pipe lap joint of the type comprising: an inside pipe and an outside pipe in telescoping relationship to provide an overlap region on the end of each pipe, said overlap region on the outside pipe defining a circumferentially continuous area and at least one pair of axially extending slots, the first slot of each pair being disposed adjacent and through the end of said outer pipe and the second slot of each pair being spaced inwardly from the end of said outer pipe, a clamping band disposed around said outside pipe and covering said second slot, tightening means for clamping said band around said outside pipe to clamp the pipes together and collapse the overlap region of said outer pipe into close fitting engagement with said inner pipe to cause sealing engagement of said outer pipe with said inner pipe and with said band, the improvement wherein: said first slot has sidewalls extending axially inwardly from the end of said outside pipe and terminates in a transverse inner end wall within said overlap region, said second slot is circumferentially offset from said first slot and has sidewalls extending axially inwardly from an outer end wall, the adjacent sidewalls of said slots being in substantial alignment with each other and said end walls being in substantial alignment with each other, whereby said end walls of said slots are disposed in edge-to-edge engagement with each other when the overlap region of said outer pipe is collapsed into close fitting engagement with said inner pipe by clamping said band around said outside pipe.