Granted Patent
Utility
US 4,245,816 · App. 05/897,894
Flow force balanced spool valve
Inventor:
Howard L. Johnson
Patented Case
View Patent ↗
Granted: Jan 20, 1981
Filed: Apr 19, 1978
Inventor
Howard L. Johnson
Assignee (at issue)
Caterpillar Tractor Co.
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.