Granted Patent
Utility
US 6,815,652 · App. 09/659,100
Low power phototransistor-based welding helmet providing reduced sensitivity to low intensity light and sharp phototransistor response to high intensity light
Inventor:
Thomas J. Hamilton
Patented Case
View Patent ↗
Granted: Nov 9, 2004
Filed: Sep 11, 2000
Inventor
Thomas J. Hamilton
Assignee (at issue)
Jackson Products, Inc.
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.