Plastic railway crosstie
Abstract
Abstract A cellular thermoplastic product such as a railway crosstie is produced by an apparatus comprising extrusion means for producing a web of a foamable thermoplastic polymer such as polyethylene, a mold corresponding to the size and shape of the cellular product positioned adjacent the extrusion means to receive the web of foamable thermoplastic polymer, and means for imparting relative reciprocal motion between the mold and the extrusion means in a direction generally normal to one of the surfaces of the web such that the web is deposited in layers within the mold. In producing a cellular thermoplastic product by the method of the invention, the steps include plastifying a thermoplastic polymer such as polyethylene in the presence of an expanding agent to produce a foamable thermoplastic polymer, forming the foamable thermoplastic polymer into a web, depositing the web into a mold, and imparting relative reciprocal motion between the web and the mold in a direction normal to at least one surface of the web such that the web is deposited in layers within the mold. The foamable thermoplastic layers in the mold fuse together at their mating surfaces thereby resulting in the cellular thermoplastic product.
Inventors
- 👤 B Heinemeyer
Bibliographic Details
Claims Analysis
Total Claims: 2References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-27 | 1977-11-26 | 1978-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-27 | 1981-11-26 | 1982-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-27 | 1985-11-26 | 1986-05-28 | $7700.00 | Window Closed / Lapsed |