Motor compensating spring

Details Motor compensating spring Motor compensating spring

1999-10-20

2001-10-09

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S090000, C417S423300

Reexamination Certificate

active

06300699

ABSTRACT:

TECHNICAL FIELD
This invention relates to a motor configuration for controlling movement of components therein. More specifically, this invention relates to a configuration of an axial motor, such as a submersible pump motor, which allows variations in thermal expansion of the motor shaft and other components while protecting the components from damage during shipping and start-up.
BACKGROUND ART
Axial motors, such as a submersible pump motor, have multiple rotors, each separated by a rotor bearing and retained on the motor's central shaft by retaining rings. These rotors are constructed primarily from copper while the shaft is primarily steel. As the motor runs, it generates heat and causes the components to expand. There is a substantial difference in the rate of thermal expansion between copper and steel, thus the rotors expand significantly more than the shaft. In some cases, this difference in expansion can result in the rotor stack being as much as half an inch longer than the shaft. If the rotor stack is constrained by the retaining rings and not allowed to expand relative to the shaft, the rotors expand into the bearings and prevent the bearings from rotating. The friction from the locked bearings causes tremendous heat and ultimate failure.
The prior art motors have loosely fit the rotor stacks on the central shaft, allowing a clearance between the rotor stack and the upper retaining ring. This provides room into which the rotors can expand and prevents the rotors from expanding into the bearings. However, the clearance introduces new problems. The rotors of the prior art can freely slide on the shaft and be damaged as they slam into each other during transport. Further, during start-up, the rotor stack can jump upwards on the shaft. As the rotor stack settles down, one or more rotor bearings can become misaligned and wedge in the stator bore. A wedged bearing may prevent the rotors beneath from expanding freely as the motor warms up, and as discussed above, prevent the bearings from rotating and cause a motor failure.
Therefore, there is a need for a motor that allows for the variance in thermal expansion of the rotor stacks and central shaft, yet protects the rotor stack from damage during transport and prevents rotor bearing misalignment and failure at start-up.
SUMMARY OF THE INVENTION
The present invention is directed to a motor configuration that allows for the variance in thermal expansion of the rotor stacks and central shaft while protecting the rotor stack from damage during transport and preventing misalignment and failure at start up. The motor has a housing with cylindrical stator and a centrally mounted shaft. A retaining ring is mounted on the shaft and a rotor stack is carried to slide axially on the shaft. The rotor stack is biased against the retaining ring. In a preferred embodiment, a spring is mounted above the rotor stack, between the rotor stack and a second retaining ring. The spring abuts both the rotor stack and the second retaining ring and is sized to limit free axial sliding of the rotor stack yet allow for thermal expansion of the rotor stack.


REFERENCES:
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patent: 3816782 (1974-06-01), Dow et al.
patent: 4319150 (1982-03-01), Roddy et al.
patent: 4350911 (1982-09-01), Wilson et al.
patent: 4438361 (1984-03-01), Manson
patent: 4466165 (1984-08-01), Otto
patent: 4471246 (1984-09-01), Paillet
patent: 4613778 (1986-09-01), Wrobel et al.
patent: 4745316 (1988-05-01), Nakashima et al.
patent: 5367214 (1994-11-01), Turner, Jr.

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