High pressure coupling for plastic pipe and conduit

A coupler system comprising:

• a coupler having a stop and a bell extending therefrom, the bell defining a cylindrical inner wall in which an outward annular groove is defined, each annular groove having a gasket engaging surface which faces generally toward the stop;
• a length of corrugated pipe having a corrugated outer wall and a smooth inner liner affixed interior to and lining the corrugated outer wall, the inner liner providing a smooth surface to fluid flowing therethrough to reduce drag and improve fluid flow capacity relative to the corrugated outer wall, the inner liner being sufficiently thin that the corrugated outer wall provides support that prevents the inner liner from being collapsed by backfill and from rupturing under internal pressure of the fluid flowing therethrough;
• a gasket received in a valley of the length of corrugated pipe and inserted with a tight frictional fit into the coupler bell, the internal fluid pressure acting on the gasket such that the gasket converts a portion of the internal fluid pressure into an axial force which urges the gasket and an end of the corrugated pipe adjacent the gasket to move axially away from the stop, the gasket including an outward projecting flange which slopes outward and away from the coupler stop, the annular flange having a groove engaging surface facing generally away from the coupler stop and engaging the gasket engaging surface of the groove such that the gasket transfers the axial force to the coupler bell such that the coupler bell strengthens the corrugated pipe adjacent the gasket against axial compression.

A method of coupling corrugated plastic tubing which has a corrugated outer wall, the method comprising:

• inserting a resilient gasket into a valley of the corrugated outer wall closely adjacent an end of the tubing, the gasket extending radially outward beyond adjacent peaks of the corrugated outer wall;
• inserting the tubing end into a cylindrical coupler bell compressing the gasket into the valley;
• continuing to insert the tubing end further into the cylindrical coupler bell until the gasket aligns with an annular groove in the bell, the gasket snapping resiliently into the groove;
• conveying fluid under pressure through the tubing such that the fluid under pressure places an axial force on an inner surface of the gasket in communication with the fluid, which axial force urges the tubing end to compress axially and the gasket to slide out of the bell;
• transferring a portion of the axially force through the gasket to the coupler bell such that structural strength of the coupler bell under tension combines with structural strength of all the tubing end under compression to hold the tubing extended against the axial force and anchors the gasket against sliding relative to the coupler bell.