Granted Patent
Utility
US 4,460,156 · App. 06/259,421
Wellhead connector with check valve
Inventors:
Keith R. Hazelrigg, Edward W. Locheed, Jr.
Patented Case
View Patent ↗
Granted: Jul 17, 1984
Filed: May 1, 1981
Inventors
Keith R. Hazelrigg
Edward W. Locheed, Jr.
Assignee (at issue)
NL Industries, 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.