Patent Number: 6,309,438

Title: Filter unit and dust-proof mask therewith

Abstract: The present invention provides a filter containing a filter material foldedinto a chrysanthemum shape. While such a filter can be made of an electretfiber nonwoven fabric or a fiberglass nonwoven fabric, preferably it ismade of a polytetrafluoroethylene porous film that is extended lengthwiseand widthwise such that the overall area is extended by more thanfifty-fold.

Inventors: Kanno; Tomoaki (Hatano, JP), Yamada; Kunio (Tokorozawa, JP), Umezaki; Hirohisa (Fujidera, JP)

Assignee:

International Classification:

Expiration Date: 10/32013