Structures of plastics material
US4954299A · kind A · utility
Inventors
Key dates
| Filing date | Jun 28, 1989 |
| Grant date | Sep 4, 1990 |
| Priority date | — |
| Expiry date | Jun 28, 2009 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29L2031/246
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Large fittings or other structures are made by rotationally moulding a first component 18 of polyethylene and joining cylindrical pups 20, 22, 24 of polyethylene to the component by butt fusion joints 26, 28, 30. The structure within the boundary 50 is irradiated with gamma radiation followed by post-heating to remove free radicals. The extremities of the pups are shielded to prevent irradiation. Their capability to be joined to polyethylene pipes 12, 14, 16 by butt-fusion joints 32, 34, 36 is unimpaired. The irradiation introduces cross-linking to give improved properties such as impact resistance and stress crack resistance and to bring the fitting within the specification for polyethylene pipe for natural gas distribution. The joints 26, 28, 30 are made using differential heating of the ends to be joined to compensate for differences in melt flow index. Alternatively, the component 18 is slightly irradiated to lower its MFI before the pups are joined to it.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.