FR521322A
Expired / Lapsed
FR
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Improvements in tunnel construction
Assignee: Individual
•
Filing: 1920-07-28
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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 12:10
CPC Classifications
E; E02; E02D; E02D29/00; E02D29/063; E02D29/07
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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