Granted Patent
Utility
US 5,217,531 · App. 07/812,014
Fluid loss additives for cementing compositions
Inventor:
Ping-Sun Cheung
Patented Case
View Patent ↗
Granted: Jun 8, 1993
Filed: Dec 23, 1991
Inventor
Ping-Sun Cheung
Assignee (at issue)
Western Company of North America
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.