Large diameter double-walled plastic pipe

Abstract From the Canadian patent

Non-releasable double-walled molded, large-, diameter, corrugated plastic pipe having walls made of high density polyethylene, PVC or polypropylene of sufficient thickness so as to be rigid but elastic and therefore relatively inflexible and having an integral automatically locking female coupling at one end, with access to its latching members at its exterior, and a method of manufacturing multiples thereof by a continuous molding process. The pipe has a smooth interior wall and a corrugated outer wall integral therewith. Only minor auxiliary cutting operations are required to separate portions thereof into individual plastic pipe sections, each having the automatic-locking coupling at one …