Concrete type drainage pipe with sheath holes - has interior hollow and holes made in single process with form cores

摘要

The concrete or similar pipe is esp. of the type laid for drainage, in or near rods and other traffic routes, with sheath apertures in the top for water collection. In prodn. both its interior hollow space and sheath openings are formed in a single proces, with the aid of form core units. The internal walling for the hollow space and the sheath openings can be formed by an integrated thin-walled form core, which may be made of plastics, asbestos cement, or metal. The sheath openings may be slit-shaped, and arranged along a single line, or in a surface pattern. They may widen conically towards the interior. A smooth internal surface is ensured, likewise min. risk of encrustation of the holes.