BECHDEFRGBLINLSE0033654EUROPEAN PATENT APPLICATIONA319811021EP8130042419810202800359119800202GB800442719800209GB1981102119814219810812198132 6E 21B 10/60 A 6E 21B 21:00 B 6E 21B 07:18 B 6E 21B 33:138 BenRotary drill bits and method of usefrTrépan de forage rotary et procédé pour son utilisationdeDrehbohrmeissel und AnwendungsverfahrenDRILLING & SERVICE U.K. LIMITEDDenzil, Barr JohnBECHDEFRGBLINLSE19811021198142

To prevent foreign bodies or lost circulation material in drill mud locking the nozzles of a rotary drill bit, the central passageway incorporates a separating means arranged to separate larger particles from the drill mud and to divert them away from the nozzles and out of the bit. The separating means is arranged to operate in a static or dynamic manner.