Granted Patent
Utility
US 4,704,876 · App. 06/895,875
Cryogenic refrigeration system
Inventor:
Ralph P. Hill
Patented Case
View Patent ↗
Granted: Nov 10, 1987
Filed: Aug 12, 1986
Inventor
Ralph P. Hill
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.