Granted Patent
Utility
US 4,248,580 · App. 05/920,817
Structure for directing concrete to pipe jacket
Inventor:
Alfred W. Christian
Patented Case
View Patent ↗
Granted: Feb 3, 1981
Filed: Jun 30, 1978
Inventor
Alfred W. Christian
Assignee (at issue)
Hydrotile Canada Limited
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.