FIELD OF DISCLOSURE

The present disclosure relates to coupling together drive shafts of modules of a submersible well pump assembly. More specifically, the present disclosure relates to couplings that will selectively transfer torque or ratchet to avoid rotating the thrust bearing in reverse.

BACKGROUND

Electrical submersible pumps (ESP) are commonly used in hydrocarbon producing wells. An ESP includes a pump driven by an electrical motor. A thrust bearing is normally located between the pump and the motor for transferring down thrust imposed on the pump shaft to a housing. The thrust bearing has a thrust runner that operates best while rotated in a normal operating direction. If rotated in reverse, damage to the thrust bearing can occur.

Reverse rotation to the thrust runner can occur in some instances. For example, in some ESP's, when the motor is shut down, the weight of the well fluid in the production tubing can cause the well fluid to flow back down the production tubing, through the pump and out the pump intake. This reverse flow spins the pump shaft in reverse, which in turn would spin the thrust bearing runner in reverse. Also, if the motor shaft is being driven by the pump shaft in reverse, the motor could generate electrical voltage to the surface, which could create problems.

In another instance, the power conductors to the motor may be accidentally reversed during installation, causing the motor to rotate in reverse. This reverse rotation would also spin the thrust bearing runner in reverse.

SUMMARY

An apparatus for pumping well fluid from a well comprises an electrical submersible pump assembly (“ESP”) having a motor and a pump, the motor having a motor shaft that drives a pump shaft of the pump. A thrust bearing unit between the motor and the pump has a thrust bearing shaft that rotates a thrust runner in sliding engagement with a non-rotating thrust bearing base. A pump shaft coupling couples the thrust bearing shaft with the pump shaft. A motor shaft coupling couples the thrust bearing shaft with the motor shaft. At least one of the couplings has a one-way clutch that allows forward direction rotation of the thrust bearing shaft and prevents reverse direction rotation.

At least one of the couplings may comprise the pump shaft coupling. At least one of the couplings may comprise the motor shaft coupling. At least one of the couplings may comprise both the pump shaft coupling and the motor shaft coupling.

At least one of the couplings comprises a coupling housing having a coupling housing socket with internal splines. A receptacle in the coupling housing has a receptacle interior wall. A hub is rotatably carried in the receptacle, the hub having a hub socket with internal splines. A one-way clutch is located between the receptacle interior wall and the hub and configured to transfer torque between the hub and the receptacle interior wall while the motor shaft is being driven in the forward direction. The one-way clutch allows relative rotation between the receptacle interior wall and the hub while the motor shaft is not being driven in the forward direction.

The one-way clutch may comprise a plurality of pawls located between the receptacle interior wall and the hub that are configured to transfer torque between the hub and the receptacle interior wall while the motor shaft is being driven in the forward direction. The pawls allow relative rotation between the receptacle interior wall and the hub while the motor shaft is not being driven in the forward direction.

Each of the pawls may be spaced around the hub, each having an inner end in engagement with the hub and an outer end in engagement with the receptacle interior wall. The pawls are configured to transfer forward direction torque between the hub and the receptacle interior wall when the motor shaft is rotating in the forward direction and to allow slippage between the hub and the receptacle interior wall if the motor shaft is not rotating in the forward direction.

