Granted Patent
Utility
US 6,226,928 · App. 09/039,053
Caustic fluid blocking member in the base of a manhole
Inventor:
Julian P. Trangsrud
Patented Case
View Patent ↗
Granted: May 8, 2001
Filed: Mar 13, 1998
Inventor
Julian P. Trangsrud
Assignee (at issue)
Royal Environmental Systems, Inc.
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.