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| All Patents in class 175/213 | |||||
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| Number | Date | Patentee | Title | Type | |
| 2,919,901 | Jan. 05, 1960 | R.L. Sandvig | Drill system with suction | ||
| 2,969,846 | Jan. 31, 1961 | R.L. Sandvig | Percussive drill bit for use in reverse flow flushing is soft rock drilling | ||
| 3,057,417 | Oct. 09, 1962 | R.L. Sandvig | Drill system with suction removal of cuttings | ||