A rotor has a rim that diverges from its peripheral portion. Accordingly, the rim more securely couples with a shaft. More specifically, the rotor has a support member with a peripheral portion and an interior rim. The interior rim defines a central opening and, as noted above, diverges from the peripheral...http://www.google.ca/patents/US7548007?utm_source=gb-gplus-sharePatent US7548007 - Rotor shaft coupling
