Granted Patent
Utility
US 4,861,252 · App. 07/253,365
Vibrator type concrete pipe making machines having combined lubrication and cooling system
Inventor:
Thomas D. Grau
Patented Case
View Patent ↗
Granted: Aug 29, 1989
Filed: Sep 29, 1988
Inventor
Thomas D. Grau
Assignee (at issue)
International Pipe Machinery Corporation
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.