Magnetic positioning mechanism for fluid-supported self-rotating displays

Abstract

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.

What is claimed is: 
     
         1 . A self-rotating device comprises:
 a container carrying a fluid;   a self-powered rotating body buoyantly supported by said fluid;   wherein said body comprises:
 an axis of rotation; 
 an electric motor contained inside said body, said electric motor comprising:
 a counter-torque element rotationally responsive to an ambient magnetic field; and, 
 
   wherein said device further comprises:
 a magnetic lateral positioning structure apart from said body and apart from said electric motor, wherein said magnetic lateral positioning structure is fixed in a non-rotating manner to said container; and, 
 wherein said magnetic lateral positioning structure is located an effective distance from said counter-torque element so as to laterally bias said body toward a position of magnetic equilibrium between said magnetic lateral 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 lateral positioning structure comprises a positioning magnet generating a multipurpose magnetic field providing both said ambient magnetic field and said local attractive magnetic force. 
     
     
         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 counter-torque element and magnetic lateral positioning structure are vertically aligned. 
     
     
         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 lateral positioning structure. 
     
     
         9 . The device of  claim 8 , wherein said axis passes through a void bounded by said magnetic lateral positioning structure. 
     
     
         10 . The device of  claim 1 , wherein said magnetic lateral positioning structure has an aggregate center of mass located along said axis of rotation. 
     
     
         11 . The device of  claim 1 , wherein said effective distance is less than about 5 centimeters. 
     
     
         12 . The device of  claim 1 , wherein said device further comprises:
 a local attractive magnetic force between said magnetic lateral positioning structure and said counter-torque element; and,   wherein said local attractive magnetic force has a strength which is insufficient overcome a buoyancy of said body.   
     
     
         13 . The device of  claim 1 , wherein said magnetic lateral 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.