Granted Patent
Utility
US 4,803,398 · App. 06/881,709
Electron gun with one directly heatable and one indirectly heatable cathode
Inventors:
Reinhardt Kraft, Horst Ranke
Patented Case
View Patent ↗
Granted: Feb 7, 1989
Filed: Jul 3, 1986
Inventors
Reinhardt Kraft
Horst Ranke
Assignee (at issue)
Leybold-Heraeus GmbH
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.