Abstract: A rotary rock bit is provided having a lubrication system with an expansion space within the lubricant reservoir to accommodate changes in lubricant volume. A flexible diaphragm is located within the lubricant reservoir. The lubricant reservoir is filled with lubricant thereby moving the flexible diaphragm to a substantially completely filled position. A predetermined volume of lubricant is displaced from the lubricant reservoir by forcing a fluid through passage means in the reservoir cap, moving the flexible diaphragm and displacing a predetermined volume of lubricant thereby providing an expansion space within the lubricant reservoir.

Abstract: A seal acts as a barrier to the drilling fluid, pulverized cuttings and other materials in a borehole preventing the materials from entering the bearing area of a rolling cone cutter earth boring bit and retains lubricant inside the bearing area. A rolling cone cutter is rotatably mounted on a cantilevered bearing pin extending from the bit body. A "Z" seal is positioned between the cutter and bearing pin. An outer rigid seal ring is positioned around the bearing pin. The outer rigid seal ring is split to allow radial expansion and contraction. An inner rigid smaller diameter seal ring is positioned around the bearing pin. The inner rigid seal ring is also split to allow radial expansion and contraction. An elastomer ring is located between the inner and outer rigid rings and affixed to the rigid rings.