Granted Patent
Utility
US 4,957,424 · App. 07/322,175
Concrete pipe making machine
Inventors:
William J. Mitchell, Navarro T. Fosse
Patented Case
View Patent ↗
Granted: Sep 18, 1990
Filed: Mar 13, 1989
Inventors
William J. Mitchell
Navarro T. Fosse
Assignee (at issue)
Hydrotile Machinery Company
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.