Granted Patent
Utility
US 6,637,980 · App. 09/992,415
Method and apparatus for re-tensioning a roof bolt in an underground mine
Inventor:
Roy Lee Robertson, Jr.
Patented Case
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Granted: Oct 28, 2003
Filed: Nov 23, 2001
Inventor
Roy Lee Robertson, Jr.
Assignee (at issue)
Earl Products, 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.