(19)

(11)

EP 0 504 143 A1

(12)

(43) Date of publication: 23.09.1992 Bulletin 1992/39 (21) Application number: 90911823.0 (22) Date of filing: 29.06.1990

(51) International Patent Classification (IPC):  B03C 3/ 68( . ) (86) International application number: PCT/US1990/003714 (87) International publication number: WO 1991/008053 (13.06.1991 Gazette 1991/13)

(84) Designated Contracting States: BE DE DK FR GB NL SE (30) Priority: 30.11.1989 US 19890005430 (71) Applicant: BHA GROUP, INC. Kansas City, MO 64133 (US)	(72) Inventors: JOHNSTON, David, F. Tabb, VA 23602 (US) FARMER, Terry, L. Pleasant Valley, MO 64068 (US) (74) Representative: Witte, Alexander, Dr.-Ing.  Witte, Weller, Gahlert & Otten Patentanwälte Augustenstrasse 14 W-7000 Stuttgart 1 W-7000 Stuttgart 1 (DE)