| 摘要 |
A manhole assembly and a method for producing cover sections for lining such manhole assembly are provided herein. The manhole assembly is comprised of a plurality of manhole sections stacked one upon the other. Each of the manhole sections is formed of a cast material and has liner means formed of a sheet-like, semirigid plastic material lining the interior surface of each manhole section. The liner means have integral, anchoring projections along their curved surfaces which engage the cast material, the integral, anchoring projections being imbedded in the cast material and having a configuration which anchors the liner means to the manhole section. The method includes the steps of providing a mold sheet having the curvature of the liner section to be formed and provided with a plurality of openings extending over the surface of the sheet. Elongated flexible strips are provided. The elongated strips are affixed upon the mold sheet with the strips being arranged in substantially-spaced, parallel fashion upon the mold sheet and following the curvature of the mold sheet, such strips being releasably securable. A flat sheet of plastic material is placed upon the surface of the mold sheet upon which the elongated strips are mounted. The sheet-like material and strips are heated to a temperature sufficient to facilitate a vacuum-forming operation. A vacuum is applied to the underside of the mold sheet, thereby causing the heated sheet to be drawn tightly against the mold sheet and the exposed surface of the elongated strips, thereby to form the liner section. The vacuum forming member is allowed to cool, and the molded member is then removed from the mold sheet. |
