Covering for a ground opening
US4873795A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 2, 1988 |
| Grant date | Oct 17, 1989 |
| Priority date | — |
| Expiry date | Nov 2, 2008 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE02D29/14
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A covering includes a cover and a frame into which the cover is inserted. A supporting surface of the cover and a cooperating bearing surface of the frame each have a surface inclined with respect to the cover plane. These surfaces are partial peripheral surfaces of a sloping cylinder and/or a sloping cone bounded by sections. As a result the partial surfaces have along their circumferences a different inclination with respect to the cover plane. Therefore the cover can only be inserted in the frame in a specific position. Since as a result of this the same surface positions of the cover and the frame always rest on one another, in the case of such coverings a tight closure can be achieved with a circular or oval opening.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.