Granted Patent
Utility
US 4,508,311 · App. 06/441,056
Annular blowout preventer
Inventors:
Friedrich E. Just, Bolie C. Williams, III
Patented Case
View Patent ↗
Granted: Apr 2, 1985
Filed: Nov 12, 1982
Inventors
Friedrich E. Just
Bolie C. Williams, III
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.