Granted Patent
Utility
US 4,228,817 · App. 05/911,403
Valve construction having multiple piston means
Inventor:
Marvin P. Weaver
Patented Case
View Patent ↗
Granted: Oct 21, 1980
Filed: Jun 1, 1978
Inventor
Marvin P. Weaver
Assignee (at issue)
ROBERTSHAW CONTROLS PRIVATE LIMITED
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.