Filter unit and dust-proof mask therewith
US6309438A · kind A · utility
21Cited by
4References
8Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Nov 15, 1999 |
| Grant date | Oct 30, 2001 |
| Priority date | — |
| Expiry date | Nov 15, 2019 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB01D39/163
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
The present invention provides a filter containing a filter material folded into a chrysanthemum shape. While such a filter can be made of an electret fiber nonwoven fabric or a fiberglass nonwoven fabric, preferably it is made of a polytetrafluoroethylene porous film that is extended lengthwise and widthwise such that the overall area is extended by more than fifty-fold.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.