1. Field
Aspects of the present invention generally relate to a non-reverse ratchet assembly for vertical shaft motors and a vertical shaft motor comprising a non-reverse ratchet assembly.
2. Description of the Related Art
Non-reverse ratchets are typically used in deep well applications where vertical electric motors that drive pumps, for example water pumps, are installed. The application can comprise for example water lubricated pump bearings. A non-reverse ratchet, herein also referred to as NRR, provides immediate protection against reversing due to phase reversals or from backspin at shutdown. The NRR stops a shaft of the vertical motor while the pump water column is receding. Otherwise, as the water flows back into the well, it will run the pump and electric motor in reverse at unbounded speed that could reach destructive levels for either the pump or the motor or both.
Currently, there are a few NRR devices available for large vertical motors that drive pumps that require a NRR. Smaller applications use for example a ball type NRR which is a virtually maintenance free device. But the ball type NRR has limited torque capacity since it depends on locking the machine on one ball only. Larger machines use for example a sprag type NRR, which has the required torque capacity. But the sprag type NRR is expensive and may require maintenance, high accuracy of machining and setting. Even a lubrication free sprag type NRR would demand tight tolerance on assembly to function correctly. Thus, there may be a need for a high capacity, maintenance free non-reverse ratchet for large vertical motors.