Core bit having axial conical core breaker
Patent 4207954 Issued on June 17, 1980. Estimated Expiration Date: 
March 31, 1998. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 31, 1998. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2731236 2738166 2975849 3055443 3112800 3158216 3768581 3845830 3861478 InventorAssigneeApplicationNo. 05/892357 filed on 03/31/1978US Classes:175/405.1, Includes diamond175/391, Plural larger diameter steps175/404With core-breaking meansExaminersPrimary: Purser, Ernest R.Assistant: Nichols, Nick A. Jr. Attorney, Agent or FirmInternational ClassesE21B 10/26 (20060101)E21B 10/46 (20060101) E21B 10/00 (20060101) E21B 10/04 (20060101) Foreign Application Priority Data1977-03-31 FRAbstractA drilling tool comprising a body having a leading face with a central recess providing the body with an annular leading cutting edge such that during drilling a central core is formed, and a central cone positioned axially in the recess for breaking up the core. | |
