Granted Patent
Utility
US 6,561,256 · App. 09/842,301
Extension spring counterbalance system
Inventor:
Willis Jay Mullet
Patented Case
View Patent ↗
Granted: May 13, 2003
Filed: Apr 25, 2001
Inventor
Willis Jay Mullet
Assignee (at issue)
Wayne-Dalton Corp.
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.