Bearing assembly with flow restrictor for a dual rod directional drilling apparatus and method of use

A horizontal directional drilling apparatus, the horizontal directional drilling apparatus comprising:

• a horizontal boring machine having a frame, a rotary machine supported on the frame, a drill string and a directional boring head, the rotary machine producing a rotation of the drill string, where the drill string has a first end, which is operatively connected to the rotary machine to drive the rotation of the drill string, and a second end, which is attachable to the directional boring head, the drill string itself being comprised of a plurality of lengths of dual-rod pipe which include drill string passageways for conducting drilling mud to the directional boring head to cool the directional boring head and remove cuttings produced during drilling operations;
• wherein the rock housing is located in the drill string at a lower extent thereof, the rock housing having an upper connecting end for connection in the drill string and an opposite, lower end, the lower end including a lower housing and a bearing mandrel bit box for connection to the directional boring head, the lower housing containing a bearing assembly and also containing an internal flow path which communicates with the drill string passageways for the passage of drilling mud;
• wherein the bearing assembly is lubricated by special bearing passageways formed within the bearing assembly which divert a portion of the flow of drilling mud passing through the drill string passageways and through the rock housing to the directional boring head, a remaining flow of drilling mud from the drill string passageways passing toward the directional boring head, the special bearing passageways serving as a metering device for the flow of drilling mud through the bearing assembly;
• wherein the bearing assembly includes a plurality of inner bearing races and a plurality of companion outer bearing races, the inner and outer bearing races having a plurality of bearing elements located therebetween, and wherein all of the inner and outer bearing races are intentionally machined so that a gap of a predetermined width exists between all of the bearing races when the bearing races are assembled with the bearing elements located therebetween;
• wherein the bearing assembly is made up of five or more of the inner bearing races and companion outer bearing races, including a first inner bearing race and a companion first outer bearing race, separated by the plurality of bearing elements, and wherein the gap which exists between the first inner bearing race and its companion first outer bearing race is smaller in size than the gap which exists between each remaining inner and outer pairs of bearing races in the bearing assembly in the downhole direction toward the directional boring head;
• wherein the size of the gap between the inner and outer bearing races can be adjusted to provide a desired amount of back pressure in the special bearing passageways which control the amount of drilling mud that is allowed to pass through the bearing assembly, the remaining flow being encouraged to flow toward the directional boring head;
• and
• wherein an additional flow restrictor is provided, integral to the bearing assembly, within the special bearing passageways defined by the gap between the inner and outer bearing races.