Granted Patent
Utility
US 4,357,121 · App. 06/203,536
Flap-gate for bottom discharge control in canals having ice problems
Inventor:
Helmut H. Wirschal
Patented Case
View Patent ↗
Granted: Nov 2, 1982
Filed: Nov 3, 1980
Inventor
Helmut H. Wirschal
Assignee (at issue)
Allis-Chalmers 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.