| US Patent: 3,417,639 
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| Planetary Speed Change Transmission for Machine Tool Feed Drives | 
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| Patentees: |  
 | Earl E. Johnson (exact or similar names) - Fond Du Lac, Fond Du Lac County, WI |  | Walter L. McCann (exact or similar names) - Fond Du Lac, Fond Du Lac County, WI |  
 
 
 
 
| Manufacturer: |  | Not known to have been produced |  
 
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| Patent Dates: |  
| Applied: | Apr. 06, 1966 |  
| Granted: | Dec. 24, 1968 |  USPTO (New site tip)
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                        Joel Havens
 "Vintage Machinery" entry for Giddings & Lewis Manufacturing Co.
 
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| Description: |  | Abstract:
A machine tool feed drive transmission is described in which three modular planetary transmission units are stacked in series to effect a large number of closely spaced output speed steps in an upper range, and a plurality of more widely spaced steps in a lower range, and in which a differential planetary gear set is employed to achieve both up-drive and down-drive output speed ratios in the first transmission unit. |  |