Granted Patent
Utility
US 4,137,942 · App. 05/705,747
Control valve having integral visual indicator for fluid safety systems
Inventors:
Melvin J. Hargraves, Clifford M. Peters
Patented Case
View Patent ↗
Granted: Feb 6, 1979
Filed: Jul 15, 1976
Inventors
Melvin J. Hargraves
Clifford M. Peters
Assignee (at issue)
W-K-M Wellhead 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.