Granted Patent
Utility
US 4,327,526 · App. 06/162,061
Apparatus for grinding the internal walls of pipes
Inventors:
William H. Pettyjohn, John Lewis, William E. Milligan, deceased
Patented Case
View Patent ↗
Granted: May 4, 1982
Filed: Jun 23, 1980
Inventors
William H. Pettyjohn
John Lewis
William E. Milligan, deceased
Assignee (at issue)
Combustion Engineering, 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.