The Donaldson Company (Donaldson) appeals from the January 30, 1991 decision of the Board of Patent Appeals and Interferences (Board) of the United States Patent and Trademark Office (PTO), reaffirmed on reconsideration on April 17, 1991, sustaining the Examiners rejection of claim 1 of reexamination application Serial No. 90/001,776 (Schuler application) under 35 U.S.C. § 103. We reverse.