Abstract: A driveshaft assembly for a downhole motor including a driveshaft having a longitudinal axis, first and second ends, and a convex spherical bearing surface disposed at the first end configured to transfer axial loads. The assembly also includes a connection lug disposed at the driveshaft first end, extending circumferentially between first and second ends, and including a recess in the first end of the lug, the recess comprising a concave cylindrical surface concentrically disposed about a pivot axis oriented orthogonal to the longitudinal axis. The assembly also includes a torque transfer key disposed within the recess and having a central axis radially spaced from the pivot axis, a convex cylindrical surface concentrically disposed about the pivot axis, and a planar surface. The convex cylindrical surface of the key slidingly engages the concave cylindrical surface of the recess; and the pivot axis intersects the key.

Abstract: A driveshaft assembly including a driveshaft having a first recess proximate a first end, and a second recess proximate a second end. The assembly also includes a first key within the first recess, a second key within the second recess, a first end housing, and a second end housing. The assembly further includes a first thrust bearing seat coaxially disposed within a first receptacle of the first end housing and including a first end, a second end, and a first length L1 measured axially between the second end and the first end, and a second thrust bearing seat coaxially disposed within a second receptacle of the second end housing and including a first end, a second end, and a second length L2 measured axially between the second end and the first end. L1 and L2 are both fixed and L2 is greater than L1.

Abstract: An embodiment of a method for drilling a borehole into an earthen formation, the method including contacting a first end housing at a first axial position with a first drive key, wherein the first end housing has a central axis, a first end, a second end opposite the first end, and a first receptacle extending axially from the first end, and wherein the first drive key is disposed within the first receptacle in the first end housing and radially disposed between the first end housing and a driveshaft. In addition, the method includes transferring torque between the first end housing and the driveshaft via the first ball during. Further, the method includes, contacting the first end housing at a second axial position with the first drive key or a second drive key after (b), wherein the second axial position is axially spaced from the first axial position.

Abstract: A driveshaft assembly for a downhole motor including a driveshaft having a longitudinal axis, first and second ends, and a convex spherical bearing surface disposed at the first end configured to transfer axial loads. The assembly also includes a connection lug disposed at the driveshaft first end, extending circumferentially between first and second ends, and including a recess in the first end of the lug, the recess comprising a concave cylindrical surface concentrically disposed about a pivot axis oriented orthogonal to the longitudinal axis. The assembly also includes a torque transfer key disposed within the recess and having a central axis radially spaced from the pivot axis, a convex cylindrical surface concentrically disposed about the pivot axis, and a planar surface. The convex cylindrical surface of the key slidingly engages the concave cylindrical surface of the recess; and the pivot axis intersects the key.

Abstract: In a downhole motor bearing section having a cylindrical mandrel rotatably disposed within a cylindrical housing, a bi-directional thrust bearing is disposed within a four-shouldered annular containment chamber formed partially into the inner cylindrical wall of the housing and partially into the outer cylindrical wall of the mandrel. Under on-bottom loading conditions, thrust loads are transferred through the thrust bearing by the upper shoulder of the housing and the lower shoulder of the mandrel. The radial widths of these two shoulders are both symmetrical about the centerline of the thrust bearing such that on-bottom thrust loads are transferred non-eccentrically to the thrust bearing, thereby avoiding twisting loads on the thrust bearing races, increasing the effective on-bottom load capacity of the thrust bearing and extending its service life.