Abstract: In a drilling operation fatique producing vibrational motion is produced in the drill string in the form of longitudinal and torsional load variations at the drill bit and throughout the bottom hole assembly. These load variations occur at least partially as a result of the irregularly shaped hole bottom which develops beneath the bit and which in turn cause the bit to rise and fall with rotation, and the bit loading to vary. In addition, the rotating drill string causes gyrations in the drill string which are transmitted to the bottom end of the drill string and drill bit in the form of load and torque variations. These variations in loading appear as longitudinal and torsional vibrations in the drill string. A dampening and shock absorbing mechanism is at least partially comprised of piezoelectric elements which are responsive to the vibrations of the drill string to produce electrical energy which is used to operate downhole electrical circuits.

Abstract: A shock absorbing subassembly, for use in an oil well drilling string above a drilling bit to absorb and reduce bit induced vibration and impact loads, wherein a shock absorber element is provided which includes at least one set of ring springs.The ring springs comprise alternating closed outer rings and closed inner rings with tapered contact surfaces on the outer and inner rings.