| US Patent: 421,020 
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| Wrench For Oil Well Tools | 
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| Patentee: |  |
 | Dexter J. Thayer (exact or similar names) - Pittsburgh, PA |  
 
 
 
 
| Manufacturer: |  | Not known to have been produced |  
 
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| Patent Dates: |  
| Applied: | Feb. 28, 1889 |  
| Granted: | Feb. 11, 1890 |  
 
USPTO (New site tip)| Patent Pictures: |  |  |  | Dexter J. Thayer patent February 11, 1890 |  Google Patents
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                        Stan Schulz
 
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| Description: |  | A power wrench for drill stem links.  The power is supplied by a lever that works gear teeth in a sliding block.  The gear teeth engage rack teeth on a cross-member connecting two "hook jaw" wrenches.  The lever handle has a pawl to reset the handle in relation to the gear teeth as the sliding block's position changes. |  |