Granted Patent
Utility
US 4,428,552 · App. 06/260,110
Railroad switch machine
Inventors:
Earl E. Frank, Bing S. Yee
Patented Case
View Patent ↗
Granted: Jan 31, 1984
Filed: May 4, 1981
Inventors
Earl E. Frank
Bing S. Yee
Assignee (at issue)
Abex Corporation
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.