Granted Patent
Utility
US 4,310,139 · App. 06/137,549
Annular blowout preventer
Inventors:
Bolie C. Williams, III, Richard M. Church, Jr.
Patented Case
View Patent ↗
Granted: Jan 12, 1982
Filed: Apr 4, 1980
Inventors
Bolie C. Williams, III
Richard M. Church, Jr.
Assignee (at issue)
Cameron Iron Works, 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.