The Lamson & Sessions Co.

Thyssen-Bornemisza Inc.

William R Laney

Harold T Pate

Donald H Shell

A synthetic resin pipe which includes two identical complementary, extruded semi-cylinders joined by electromagnetic bonding along abutting longitudinal edges to form a smooth walled cylindrical pipe. In one embodiment of the invention, the smooth walled pipe forms an internal sleeve or liner within an external corrugated pipe having contiguous circumferential corrugations over its length, and having the troughs of the corrugations bonded to the outer surface of the internal sleeve. In the method for forming the pipe, two identical flat plastic sheets are extruded, then vacuumed formed into semi-cylinders each having radially outwardly projecting longitudinal flanges extending from opposite side edges thereof. A paste or dispersion containing ferro-magnetic particles is then applied to the flanges on the sides thereof adjacent the concavity of the respective semi-cylinder. The semi-cylinders are next arranged in registry to form a cylinder with the flanges abutting. Radio frequency electromagnetic radiation is then directed through the semi-cylinders at the location of the ferro-magnetic particles to fuse the semi-cylinders to each other adjacent the flanges. The flanges are then sheared away along shear lines tangential to the cylindrical side wall of the pipe thus formed.

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Tecumseh, OK, United States of America

William R Laney