Method and apparatus for making a disposable casting pattern of expanded foamed beads
US5078932A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 21, 1990 |
| Grant date | Jan 7, 1992 |
| Priority date | — |
| Expiry date | Jun 21, 2010 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29K2025/00
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
In the production of thin-walled disposable casting patterns of expanded foamed plastic beads for the full mold casting method, difficulty is encountered in that the prefoamed preexpanded beads to be introduced into the pattern mold cavity with a bulk density of less than 20 g/l have a diameter of about 2 mm and consequently a reliable reproduceable complete filling of pattern mold cavities with a cross-section of less than 5 to 7 mm is not possible. It has been found that prefoamed and preexpanded beads nevertheless having adequate foaming agent content for the final foaming expansion in the pattern mold can be produced in that following prefoaming, evacuation of the steam-air atmosphere in the prefoamed chamber is effected and additional foaming agent is introduced. Due to the partial vacuum effected by the evacuation any condensate mist can be removed from the preexpanded beads without appreciable pressure drop in the interior of the beads and without a damaging cooling so that the foaming agent being supplied can diffuse very well into the fine beads having a large surface area. As a result, the entire foaming agent content of the beads can be used for the preexpansion so that …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.