Sealed lubricated and air cooled rock bit bearing

In an earth boring bit of the type having at least one rotatable cutter with a cavity for mounting on a depending bearing pin, the cutter and the bearing pin having a thrust bearing in an inner portion of the cavity and a set of roller bearings in an outer portion of the cavity, the improvement comprising:

• air passage means for discharging through the roller bearings in the outer portion gaseous fluid pumped from the surface;
• seal means mounted between the bearing pin and the cutter for preventing the gaseous fluid from reaching the thrust bearing;
• a lubricant chamber containing lubricant and formed in the bearing pin in communication with the thrust bearing;
• and
• pressure means for applying pressure in the lubricant chamber greater than atmospheric.

In an earth boring bit of the type having at least one rotatable cutter with a cavity for mounting on a depending bearing pin, the cutter and the bearing pin having a thrust bearing in an inner portion of the cavity and a set of roller bearings in an outer portion of the cavity, the improvement comprising:

• air passage means for discharging through the roller bearings in the outer portion gaseous fluid pumped from the surface;
• seal means between the bearing pin and the cutter for preventing the gaseous fluid from reaching the thrust bearing;
• a lubricant chamber containing lubricant and formed in the bearing pin in communication with the thrust bearing, the lubricant chamber also being in communication with the air passage means;
• and
• compensator means mounted in the lubricant chamber for separating the gaseous fluid from the lubricant, the compensator means being movable for limiting pressure differential between the air passage means and the lubricant chamber.

In an earth boring bit of the type having at least one rotatable cutter with a cavity for mounting on a depending bearing pin, the cutter and the bearing pin having a thrust bearing in an inner portion of the cavity and a set of roller bearings in an outer portion of the cavity, the improvement comprising:

• air passage means for discharging through the roller bearings in the outer portion gaseous fluid pumped from the surface;
• seal means between the bearing pin and the cutter for preventing the gaseous fluid from contacting the thrust bearing;
• a lubricant chamber containing lubricant and formed in the bearing pin in communication with the thrust bearing, the lubricant chamber also being in communication with the air passage means;
• and
• a piston slidably mounted in the lubricant chamber for separating the gaseous fluid from the lubricant, the piston being movable in response to pressure differential between the air passage means and the lubricant chamber.

In an earth boring bit of the type having at least one rotatable cutter with a cavity for mounting on a depending bearing pin, the cutter and the bearing pin having a thrust bearing in an inner portion of the cavity and a set of roller bearings in an outer portion of the cavity, the improvement comprising:

• air passage means for discharging through the roller bearings in the outer portion gaseous fluid pumped from the surface;
• seal means between the bearing pin and the cutter for preventing the gaseous fluid from reaching the thrust bearing;
• a lubricant chamber containing lubricant and formed in the bearing pin in communication with the thrust bearing, the lubricant chamber also being in communication with the air passage means;
• a piston slidably mounted in the lubricant chamber for separating the gaseous fluid from the lubricant, the piston being movable in response to pressure differential between the air passage means and the lubricant chamber;
• and
• pressure relief means for discharging lubricant to the exterior should the pressure in the lubricant chamber exceed a selected maximum.

In an earth boring bit of the type having three rotatable cutters, each having a cavity inserted on a depending bearing pin, each cutter and bearing pin having mating thrust buttons at the bottom of the cavity, a radial load bearing immediately outward from the thrust buttons and a set of roller bearings at the entrance of the cavity, the bit further having an axial passage for discharging compressed air, the improvement comprising:

• an air passage extending from the axial passage to the roller bearings for passing compressed air through the roller bearings to the exterior at the cavity entrance;
• a lubricant chamber containing lubricant and extending from the air passage to the thrust buttons for supplying lubricant to the thrust buttons and the radial load bearing;
• a sliding piston carried in the lubricant chamber, separating the lubricant from the compressed air, limiting pressure differential between the compressed air and the lubricant;
• an O-ring seal located between the roller bearings and the radial load bearing for sealing the lubricant in the area of the thrust buttons and radial load bearing;
• a relief passage in the bearing pin in communication with the lubricant chamber and extending to the exterior;
• and
• a pressure relief valve mounted in the relief passage for discharging lubricant to the exterior should the pressure in the lubricant chamber exceed a selected maximum.