Abstract: The present invention provides a lubricant circulation system for a rock drill bit which circulates a flow of lubricant over the bit bearing surfaces to keep the bearings optimally lubricated and free to particulate contaminants from the drilling process. A lubricant pumping assembly, including a pair of nested gerotor pump elements is attached to either the drill bit cutting element or support structures so that one of the gerotors is driven by rotation of the bit cutting element or related structures and the other gerotor rotates freely. The gerotors have a corresponding tooth and recess configuration that pulls lubricant from the lubricant supply under positive pressure into a variable sized cavity formed as the gerotors rotate relative to each other and then forces lubricant to the bearing surfaces. Lubricant may optionally be pumped back to the lubricant supply with continued rotation of the gerotors or out of the journal area with the drilling cuttings for return to the surface.

Abstract: A three stage beam welding method is provided which is particularly useful for reliably joining two bulky, irregularly configured workpieces requiring a deep weld. The method is especially well suited for joining a piece to replace a broken or damaged portion of a tool to the tool body. In accordance with the present method, a first high energy beam is applied to the joint between the workpieces to penetrate the joint and to produce at least one undercut on the workpiece exterior surface, an optional second high energy beam is substantially simultaneously applied to the joint to smooth and flatten the undercut, and a third high energy beam is applied to the joint to heat treat the welded joint, thereby improving its metallic microstructure and mechanical properties. The three stages of this beam welding process may be repeated sequentially for the number of times required to produce a mechanically optimal, reliable joint between two particular workpieces.

Abstract: An improved apparatus and method for rotatably mounting and retaining a rock bit roller cone on a journal of a drill bit is disclosed. The bit body has at least one depending leg with an outer free end and an inner end continuous with the remainder of the bit body, and the cone surrounds the leg adjacent the outer end, forming an annular space between the leg and the cone. At least two retention bearing sleeves are disposed in the space: a first fixed to the leg and rotatable relative to the cone; and a second, disposed longitudinally inwardly of the first, fixed to the cone and rotatable relative to the leg. The retention bearing sleeves cooperate to prevent relative movement of the second sleeve longitudinally past the first.