Illustration of the interior and exterior rotors of second-order gears with the ferromagnetic stator in between the rotors.Drawings of patent US687292, showing a first-order motor with electromagnets on one of the gears.
A magnetic gear resembles the traditional mechanical gear in geometry and function, using magnets instead of teeth. As two opposing magnets approach each other, they repel; when placed on two rings the magnets will act like teeth. As opposed to conventional hard contact backlash in a spur gear, where a gear may rotate freely until in contact with the next gear, the magnetic gear has a springy backlash. As a result magnetic gears are able to apply pressure no matter the relative angle. Although they provide a motion ratio as a traditional gear, such gears work without touching and are immune to wear of mating surfaces, have no noise, and may slip without damage.
A magnetically coupled gear can be used in a vacuum without lubrication, or operations involving hermetically sealed barriers. This can be an advantage in explosive or otherwise hazardous environments where leaks constitute a real danger.
