The text and illustrations of US patents published before March 1, 1989 are in the public domain unless the patent text contains a specific notice that portions are copyrighted. See 37 CFR 1.71(d), 37 CFR 1.84(s)
The original patent contains no such notice, so its contents are in the public domain.
Note: This only applies to images published before March 1, 1989. Patents published after that date are most likely copyrighted, unless in the public domain for another reason, such as {{PD-ineligible}}.
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{{Information
|Description={{en|1=Patent Drawing of the Original Annular-type Blowout Preventer, by Hydril Corporation,
U.S. Patent 2,609,836 (1952).}}
|Source=[http://patimg1.uspto.gov/.piw?docid=02609836&PageNum=9&IDKey=3F03EE6C
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