US Patent 8062140 Power transmission line section

A power transmission section particularly adapted for use in a downhole drilling system. A drive shaft is pivotally connected to input and output end connection members with pivot balls therebetween to allow pivoting of the shaft ends relative to the input and output end connection members. A plurality of ball segments having one spherically-curved surface are provided at each end of the drive shaft to engage with the input and output connection members and to transmit torque between the shaft ends and the input and output end connection members, regardless of the angular variation between the drive shaft longitudinal axis and the longitudinal axes of the input and output end connection members.