Granted Patent
Utility
US 4,926,905 · App. 07/421,964
Manually operated air valve and actuator in combination control a hydraulic spool valve for maneuvering heavy equipment
Inventor:
Jim Helfenstein
Patented Case
View Patent ↗
Granted: May 22, 1990
Filed: Sep 29, 1989
Inventor
Jim Helfenstein
Assignee (at issue)
WILLIAMS CONTROLS, INC.
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.