Granted Patent
Utility
US 4,234,992 · App. 05/947,174
Cleaning apparatus
Inventor:
William P. Billington
Patented Case
View Patent ↗
Granted: Nov 25, 1980
Filed: Sep 28, 1978
Inventor
William P. Billington
Assignee (at issue)
NATIONAL RESEARCH DEVELOPMENT 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.