Granted Patent
Utility
US 4,856,554 · App. 07/277,749
Vacuum check valve and method of control
Inventors:
Donald L. Heffner, Dennis G. Merical, David A. Homan
Patented Case
View Patent ↗
Granted: Aug 15, 1989
Filed: Nov 30, 1988
Inventors
Donald L. Heffner
Dennis G. Merical
David A. Homan
Assignee (at issue)
General Motors LLC
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.