Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-08
2001-03-20
Mullins, Burton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S262000, C310S273000, C310S074000, C310S156030, C074S572200
Reexamination Certificate
active
06204589
ABSTRACT:
TECHNICAL FIELD
This invention relates to systems and methods for reducing mechanical strain in electric motors and generators.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,705,902 of Merritt et al. discloses a DC motor/generator based on a Halbach array of permanent magnets. This motor/generator is “inside-out” when compared with a conventional motor/generator: its rotor is on the outside of the machine, and its stator is on the inside. An array of permanent magnets rotates along with the rotor.
This geometry creates new mechanical challenges. When the rotor operates, it expands radially. The permanent magnets increase the centrifugal expansion by adding parasitic mass to the inner surface of the rotor. Large degrees of radial expansion threaten to pull the rotor away from other components of the motor/generator, thereby causing mechanical failure.
U.S. Pat. No. 4,860,611 of Flanagan et al. discloses a flexible rim hub for an energy storage rotor. Flanagan's metal hub is designed for use within the rotor itself. A tight interference fit within the rotor inhibits easy removal of the hub during maintenance. Flanagan's metal hub design is not a suitable mechanical attachment outside the axial length of the rotor. The hub lacks a surface through which bolts might be used to attach the hub to an outer axial end of a rotor. Moreover, because outer rim sections of Flanagan's hub between the spokes would expand more than rim sections at the end of spokes, the hub would be prone to failure if not surrounded by the rotor. Therefore, such a hub cannot be mounted outside the axial length of the rotor because, with its rim unenclosed by the rotor, it expands unevenly around its circumference and could break apart.
There is a need for hubs that reduce mechanical strain in motor/generators, while also being easily accessible for maintenance.
SUMMARY OF THE INVENTION
Embodiments of the invention are directed toward providing a strain-matched hub for a motor/generator.
The motor/generator preferably includes a cylindrical rotor surrounding a stator, and of larger diameter than a shaft. The hub, formed of a single material, connects the shaft to the rotor assembly, and contains a fastener circle whose expansion is matched to the rotor's expansion, in operation. Like the rotor, the hub's fastener circle expands uniformly around the fastener circle's circumference.
In a preferred embodiment, the system includes a Halbach array motor/generator, in which an array of permanent magnets on the rotor provide a uniform dipole field, and the stator lies along the axis of the dipole field.
Preferably, a ring of keystone-shaped metal elements fits the hub to the rotor. The hub attaches to the keystone-shaped elements with a plurality of bolts or other fasteners, and the keystone-shaped elements fit to the rotor. The hub is formed of a single material and contains a plurality of spokes, each spoke positioned along a radius from the center of the hub to the center of a bolt. Each spoke is shaped to fit between two pairs of tangent-joined circles. For each pair of circles, the center of the circle that forms the inner curve of the hub rim is located radially outside the center of the circle that forms the outer curve of the hub's center region.
In a preferred embodiment, the hub is made of plastic; in particular, the hub may be made of the polyamideimide plastic known at the time of filing as Torlon®.
REFERENCES:
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patent: 4058024 (1977-11-01), Gordon
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patent: 4636675 (1987-01-01), Takahashi
patent: 4860611 (1989-08-01), Flanagan et al.
patent: 4864175 (1989-09-01), Rossi
patent: 4879793 (1989-11-01), Stuecker et al.
patent: 5344895 (1994-09-01), Lai et al.
patent: 5705902 (1998-01-01), Merritt et al.
patent: 5717263 (1998-02-01), Cox
patent: 5732603 (1998-03-01), Swett et al.
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www.amocochemicals.com/pdf/imtrus.htm “Typical Properties, Torlon Polyamide-imide” (2 pages).
www.cadillacplastic.com/BuyersGuide/engineer/torlon53.htm “Torlon ®” (2 pages).
www.dsmsheffield.com/products
america/torlonnamerica . html “DSM Engineering Plastic Products, Torlon ® PA1” (4 pages).
www.magma.ca/~fesi/Home/Home.html “Flywheel Energy Systems Inc.-Home” (1 page).
www.magma.ca/~fesi/Products/Products.html Flywheel Energy Systems Inc.-Products (4 pages).
www.portplastics.com/fzen3aMb/plastics/highperform/torl on-457. html “Port Plastics—Torlon* 4347, 5030, 7130” (1 page).
Acumentrics Corporation
Bromberg & Sunstein LLP
Mullins Burton
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