Rotary earth boring drill bit with centrifugal foreign particle barrier device

In a drill bit employing a roller cone,

• a central cavity formed in said cone, said cavity having a closed end towards the apex of the cone and an open end at the base of the cone,
• bearings formed within the walls of said cavity with a peripheral portion of said cavity outside the periphery of said bearings,
• oil contained in said cavity for lubricating said bearings,
• a bearing pin mounted on said bit, said bearings rotatably mounted on said bearing pin,
• a disc-shaped wall member forming a slinger disc having a central aperture formed therein through which the pin passes in internally concentric relationship with said wall member, said wall member being mounted on said cone for rotation therewith near the base of the cone so as to partially close the open end of said cavity,
• port means including an opening formed in an outer peripheral portion of said wall member for providing fluid communications between said cavity and the outside environment of the cone, and
• a second disc-shaped wall member mounted on said cone for rotation therewith and positioned opposite the outer peripheral portion of said first mentioned wall member in parallel relationship thereto, a narrow radial annular passage being formed between said wall members, said second wall member operating to trap said oil and minimize its escape from said cavity when the cone is stationary,
• whereby particulate material entering from outside the bit is forced outwardly by the centrifugal force generated by the disc-shaped member with the rotation of the cone so as to pass through the opening in said wall member and is centrifugally trapped in said outer peripheral portions of said cavity away from said bearings.