Granted Patent
Utility
US 6,237,704 · App. 09/675,603
Backhead and check valve for down-hole drills
Inventor:
Warren T. Lay
Patented Case
View Patent ↗
Granted: May 29, 2001
Filed: Sep 29, 2000
Inventor
Warren T. Lay
Assignee (at issue)
Ingersoll-Rand Company
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.