(19)

(11)

EP 0 784 733 A1

(12)

(43) Date of publication: 23.07.1997 Bulletin 1997/30 (21) Application number: 95928225.0 (22) Date of filing: 01.08.1995

(51) International Patent Classification (IPC):  E21B 10/ 46( . ) E21B 10/ 50( . ) (86) International application number: PCT/US1995/009671 (87) International publication number: WO 1996/012084 (25.04.1996 Gazette 1996/18)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL PT SE (30) Priority: 14.10.1994 US 19940323481 (71) Applicant: KENNAMETAL INC. Latrobe, PA 15650 (US)	(72) Inventor: BEACH, Wayne, H. Roaring Spring, PA 16673 (US) (74) Representative: Sulzbach, Werner, Dipl.-Chem. Dr., et al  Prinz & Partner, Manzingerweg 7 81241 München 81241 München (DE)