Granted Patent
Utility
US 4,890,980 · App. 07/229,256
Centrifugal pump
Inventors:
Charles C. Heald, Trygve Dahl
Patented Case
View Patent ↗
Granted: Jan 2, 1990
Filed: Aug 8, 1988
Inventors
Charles C. Heald
Trygve Dahl
Assignee (at issue)
Ingersoll-Rand Company
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.