Granted Patent
Utility
US 4,290,749 · App. 05/953,376
Perlite expansion process and apparatus therefor
Inventor:
Andre R. de Muinck
Patented Case
View Patent ↗
Granted: Sep 22, 1981
Filed: Oct 23, 1978
Inventor
Andre R. de Muinck
Assignee (at issue)
Johns Manville
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.