(19)

(11)

EP 0 267 957 A1

(12)

(43) Date of publication: 25.05.1988 Bulletin 1988/21 (21) Application number: 87903970.0 (22) Date of filing: 01.06.1987

(51) International Patent Classification (IPC):  G03B 21/ 56( . ) (86) International application number: PCT/US1987/001301 (87) International publication number: WO 1987/007398 (03.12.1987 Gazette 1987/27)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 30.05.1986 US 19860868712 (71) Applicants: LAINE, Curtis S. St. Paul, MN 55102 (US) DOW, Ronald G. Brooklyn Park, MN 55444 (US)	(72) Inventors: LAINE, Curtis S. St. Paul, MN 55102 (US) DOW, Ronald G. Brooklyn Park, MN 55444 (US)