Safety coupling for rotary down hole pump

Abstract

A safety coupling for preventing backspin at excessive speeds of a torque transmitting drive powering a drive shaft which stores reactive torque due to torsional stress is disclosed. The safety coupling includes a rotatable driving member to be coupled with a torque producing power source, a rotatable driven member to be coupled with the drive shaft for axial rotation therewith, a support structure for coaxially and rotatably supporting the driving and driven members in relation to each other, a radial abutment provided on the driving member, and a centrifugal force responsive pawl pivotally mounted to the driven member for releasable engagement with the abutment. The pawl is pivoted from a locking position wherein it engages the radial abutment upon mutual rotation of the driving and driven members to provide a positive driving connection therebetween, to a disengaged position wherein the driving and driven members are freely rotatable relative to each other by the centrifugal force acting thereon when the driven member is coupled to a drive shaft backspinning at a speed in excess of a selected speed. The coupling substantially prevents damage to the torque transmitting drive upon excessive back-spin of the drive shaft and reduces the risk of injury to personnel working in the vicinity of a drive shaft subject to elastic torsion.