Granted Patent
Utility
US 4,243,120 · App. 06/052,800
Retractable boarding ladder
Inventors:
Dexter Roydon Pratt, John F. Holz
Patented Case
View Patent ↗
Granted: Jan 6, 1981
Filed: Jun 28, 1979
Inventors
Dexter Roydon Pratt
John F. Holz
Assignee (at issue)
Harnischfeger 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.