Granted Patent
Utility
US 4,377,415 · App. 06/233,664
Reinforced cement sheet product containing wollastonite for reduced shrinkage
Inventors:
Robert M. Johnson, Elmer M. Melling
Patented Case
View Patent ↗
Granted: Mar 22, 1983
Filed: Feb 11, 1981
Inventors
Robert M. Johnson
Elmer M. Melling
Assignee (at issue)
National Gypsum 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.