Douglas F. Koelfgen

📍 Delano, MN: #39 of 80 inventorsTop 50%

🗺 Minnesota: #23,881 of 52,454 inventorsTop 50%

Overall (All Time): #2,281,079 of 4,157,543Top 55%

Patents All Time

Issued Patents All Time

Showing 1–2 of 2 patents

Patent #	Title	Co-Inventors	Date
5548893	Spin-on oil filter replacement element	—	1996-08-27
4401563	Oil filter cartridge for motorcycles	—	1983-08-30