Granted Patent
Utility
US 4,286,502 · App. 06/118,037
Hydraulic load lifting system with automatic blocking valve
Inventors:
Donald L. Bianchetta, Edward A. Wirtz
Patented Case
View Patent ↗
Granted: Sep 1, 1981
Filed: Oct 15, 1979
Inventors
Donald L. Bianchetta
Edward A. Wirtz
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.