Universal Joint
A universal joint assembled in a drill string transfers torque between two components where rotation of the components may not be completely aligned. The universal joint includes upper and lower members with radial teeth connected by a serpentine retainer. As the joint rotates the members can pivot within the confines of the serpentine retainer to accommodate misalignment of the components. Axial force can be transferred through a bearing member between the members.
1 . A universal joint assembly to be used as part of a downhole drill string, comprising:
an upper member and a lower member, each with a longitudinal axis of rotation;
a first plurality of engaging elements disposed around a perimeter of the upper member;
a second plurality of engaging elements around a perimeter of the lower member; and
a flexible retainer coupled with the first and second plurality of engaging elements for transmitting torque between the upper and lower members.
2 . The universal joint of claim 1 , wherein each of the first and the second plurality of engaging elements are each comprised of teeth disposed around the perimeters of the member, separated by slots, for engaging the retainer.
3 . The universal joint of claim 1 , wherein the first and the second plurality of engaging elements are comprised of pins.
4 . The universal joint of claim 1 , wherein the retainer comprises a serpentine retainer that allows for limited, relative movement between the upper and lower members to accommodate axial, angular and lateral misalignment the respective longitudinal axes of rotation of the upper and lower members.
5 . The universal joint of claim 4 , wherein the serpentine retainer allows for limited rotation of the upper member in relation to the lower member.
6 . The universal joint of claim 4 , wherein the serpentine retainer is elastic.
7 . The universal joint of claim 1 wherein each of the engaging elements in the first and second plurality of engagements elements extend in a radial direction, relative to the longitudinal axis of rotation of the upper or lower member on which they are disposed.
8 . The universal joint of claim 1 , wherein the upper and lower members are spaced apart by a bearing element retained between upper and lower members to transfer axial loads through the joint.
9 . The universal joint of claim 8 , wherein the bearing element comprises a ball bearing.
10 . The universal joint of claim 1 , wherein the flexible retainer is comprised of one or more of metal, carbon fiber, Kevlar®, and matrix.
11 . The universal joint of claim 1 wherein the upper member has a first connector for joining to a first drill string component and the lower member has a second connector for joining to a second drill string component.
12 . The universal joint of claim 11 , wherein one of the upper member and the lower member is coupled with a rotary output of a positive displacement motor or a radial impulse tool.
13 . The universal joint of claim 12 , wherein the other of the upper member and the lower member is coupled with a drill bit.
14 . The universal joint of claim 1 wherein the upper and lower members each have a surface facing the other that is planar.
15 . A universal joint assembly for downhole applications comprising:
two members for coupling to adjacent components of a downhole drill string, each of the two members having disposed around its circumference teeth; and
at least one flexible retainer for coupling the two members by engaging corresponding teeth to transmit torque.
16 . The universal joint of claim 15 , wherein at least one of the teeth comprises a rectangular lug.
17 . The universal joint of claim 15 , wherein at least one of the teeth has one of a lenticular, elliptical and cylindrical shape.
18 . The universal joint of claim 15 , wherein at least one of the teeth has formed thereon an end chamfer for accommodating displacement of the retainer when under torque.
19 . The universal joint of claim 15 wherein the at least one retainer has a serpentine configuration disposed around the entire circumference of the two circumferentially toothed members.
20 . The universal joint of claim 15 , wherein the least one retainer is comprised of at least two parallel ribs joined.
21 . An assembly to transfer torque in a downhole drill string comprising:
first and second bodies, each having a connector for joining body to an adjacent component of a downhole drill string and each having a longitudinal axis of rotation; the first body having slots formed around an outer circumference the body aligned with the slots formed around the circumference of the second body; and
a retainer passing through aligned slots in the first and second bodies.
22 . The assembly to transfer torque in a downhole drill string of claim 21 , wherein the upper and lower members are spaced apart by a bearing element.
23 . The assembly to transfer torque in a downhole drill string of claim 22 , wherein the bearing element is retained between upper and lower members to transfer axial loads through the joint.
24 . The assembly to transfer torque in a downhole drill string of claim 22 wherein the bearing element comprises a ball bearing.
25 . The assembly to transfer torque in a downhole drill string of claim 21 wherein one of the upper member and the lower member is coupled with a rotary output of a positive displacement motor or a radial impulse tool.
26 . The assembly to transfer torque in a downhole drill string of claim 21 , wherein the retainer has a serpentine configuration.
27 . The assembly to transfer torque in a downhole drill string of claim 26 , wherein the serpentine retainer comprises ribs that are straight parallel sections connected by arcuate loops.