Magnetic Positioning Mechanism for Fluid-Supported Self-Rotating Displays
A self-rotating display device ( 1 ) includes and outer light transmissive container ( 2 ) containing a light transmissive fluid ( 6 ) and a body ( 4 ) containing an electric motor ( 14 ) for rotating the body with respect to the outer container. The body also carries a compass magnet ( 18 ) as a source of counter-torque for the motor to operate against. A magnetic positioning structure ( 20 ) made of ferromagnetic material secured to the container interacts with the magnetic field of the compass magnet to cause the body to migrate toward a location minimizing the distance between the magnetic positioning structure and compass magnet, so that the body can remain centered within the display while rotating.
1 . A self-rotating device comprises:
a container carrying a fluid;
a self-powered hollow rotating body buoyantly supported by said fluid;
wherein said body comprises:
an axis of rotation;
an electric motor comprising:
a counter-torque element rotationally responsive to an ambient magnetic field; and,
wherein said device further comprises:
a magnetic positioning structure fixed with respect to said container,
a local magnetic field generated by at least one of said magnetic positioning structure and said counter-torque element;
wherein said magnetic positioning structure is located an effective distance from said counter-torque element so as to interact with said local magnetic field to bias said body toward a position of magnetic equilibrium between said magnetic positioning structure and said counter-torque element.
2 . The device of claim 1 , wherein said counter-torque element is a compass magnet aligned to said ambient magnetic field.
3 . The device of claim 2 , wherein said ambient magnetic field is the earth's magnetic field.
4 . The device of claim 1 , wherein said magnetic positioning structure comprises a positioning magnet generating a multipurpose magnetic field providing both said ambient magnetic field and said local magnetic field.
5 . The device of claim 4 , wherein said positioning magnet is a permanent magnet.
6 . The device of claim 1 , wherein said container comprises a light transmissive outer wall; and
wherein said fluid comprises a light transmissive liquid.
7 . The device of claim 1 , wherein said position of magnetic equilibrium minimizes a distance between said counter-torque element and magnetic positioning structure.
8 . The device of claim 1 , wherein said position of magnetic equilibrium is located so that said axis of rotation intersects a region occupied by said magnetic positioning structure.
9 . The device of claim 8 , wherein said axis passes through a void bounded by said magnetic positioning structure.
10 . The device of claim 1 , wherein said effective distance is less than about 5 centimeters.
11 . The device of claim 1 , wherein said local magnetic field generates a biasing force which is insufficient to overcome a buoyancy force buoyantly supporting said body against gravity.
12 . The device of claim 1 , wherein said local magnetic field generates a biasing force which is insufficient to overcome a force of gravity acting on said body.
13 . The device of claim 1 , wherein said magnetic positioning structure comprises an amount of ferromagnetic paint coating a portion of said container.
14 . The device of claim 1 , wherein said fluid comprises two different density liquids, wherein said liquids are selected to buoyantly support said body within said container.
15 . The device of claim 1 , wherein said device further comprises a light transmissive outer enclosure forming said container, wherein said enclosure is shaped and dimensioned to have an internal cavity containing an amount of a light transmissive liquid forming said fluid and said self-powered hollow rotating body being immersed in said liquid.
16 . The device of claim 1 , wherein said local magnetic field has a strength which cannot overcome the weight of said body.