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A thermoplastic corrugated drainage tube comprising annular peaks and valleys and a plurality of drainage openings internally cut about the circumference of each valley, the openings in each valley aligned with the openings in successive valleys along helical lines described by said openings. The me

A thermoplastic corrugated drainage tube comprising annular peaks and valleys and a plurality of drainage openings internally cut about the circumference of each valley, the openings in each valley aligned with the openings in successive valleys along helical lines described by said openings. The method of forming the drainage openings comprises placing a cutting tool in the interior of the tubing and rotating the tool while moving the tubing axially past the tool. The cutting tool comprises a body having a plurality of radially projecting cutters spaced equidistantly about the cutter body and means for rotating the tool.

대표청구항 ▼

Corrugated drainage tubing of organic thermoplastic material comprising a tubular wall of alternating peaks and valleys and a plurality of drainage openings in the valleys, characterized in that a like plurality of spaced drainage openings are provided about the circumference of each valley in the b

Corrugated drainage tubing of organic thermoplastic material comprising a tubular wall of alternating peaks and valleys and a plurality of drainage openings in the valleys, characterized in that a like plurality of spaced drainage openings are provided about the circumference of each valley in the base thereof, the drainage openings in each valley are axially and circumferentially offset of wall material from the nearest adjacent drainage opening in adjacent valleys and, together with the nearest adjacent drainage openings in successive adjacent valleys, form a plurality of arrays of drainage openings extending along parallel helical lines at an acute angle in the range of about 14°-37°to the longitudinal tubing axis, and each said drainage opening is axially spaced by wall material from each adjacent helical array and the drainage openings of each said adjacent helical array for an axial distance comprising a plurality of valleys.