Steerable rotary drilling device and directional drilling method

摘要

A fulcrum bearing assembly for rotatably supporting a shaft within a housing, including at least one row of spherical thrust bearings positioned at a first axial position within the housing, at least one row of spherical thrust bearings positioned at a second axial position within the housing and at least one row of spherical radial bearings positioned at a third axial position within the housing. The third axial position is located between the first and second axial positions. Further, a bearing preload assembly for maintaining a bearing assembly in a preloaded condition, including a thrust bearing shoulder associated with a housing and a thrust bearing collar. The bearing assembly is axially maintained within the housing between the thrust bearing shoulder and the thrust bearing collar, wherein the thrust bearing collar is axially adjustable relative to the thrust bearing shoulder in order to preload the bearing assembly therebetween.