Patent FR521322A successfully refreshed from Google Patents.
FR521322A
Expired / Lapsed
FR
⏱️ 0.0 years remaining
Improvements in tunnel construction
Assignee: Individual
•
Filing: 1920-07-28
•
Granted: 1921-07-09
•
Expires: 1940-07-28
Abstract
No abstract record available.
Inventors
- 👤 Gustav Peter Helfrich
Bibliographic Details
Application Number
—
Jurisdiction
FR
Data Source
google_patents
Last Synchronized
2026-11-07 12:45
CPC Classifications
E; E02; E02D; E02D29/00; E02D29/063; E02D29/07
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.