End adaptor for flexible corrugated tube

Claim 1

In a flexible corrugated tube having a major axial length portion and, an one end, an integral, outwardly flared end adapter of frustoconical form, the major length portion having both internal and external helical ridges and grooves, the improvement wherein said tube is made by: placing a sleeve of uncured rubber on a forming mandrel having a main, axially extending outer surface portion defining an external helical groove and at one end, axially aligned with said main surface portion, an end mold with a frustoconical, axially outward portion having a flared, relatively smooth outer surface and an axially inward portion defining an external helical groove that registers with and has the same diameter, pitch, and width as the external helical groove on the main surface portion, the sleeve being placed about the end mold for the entire axial length thereof; wrapping a flexible cord around the uncured sleeve along the main surface portion of the mandrel and the inward portion of the end mold to press the sleeve into the helical grooves so that axial length portions of the sleeve conform to the helical grooves and another axial length portion conforms to said smooth frustoconical outer surface of said axially outward portion of said end mold to define a smooth flared end of said sleeve wherein both the interior and exterior surfaces of the flared end are smooth; and thereafter curing the partially corded, uncured sleeve while on the mandrel to set the flared end and the helical corrugations and to form a flexible tube with a helically corrugated major axial length portion and an outwardly flared frustoconical end adapter having a smooth exterior surface and a smooth interior surface on an axially outward length portion and exterior helical groove on an axially inward length portion.