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Self-powered rotation indicator

  • US 4,728,942 A
  • Filed: 12/09/1985
  • Issued: 03/01/1988
  • Est. Priority Date: 12/09/1985
  • Status: Expired due to Term
First Claim
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1. In a device having a rotating member contained at least partially within a housing so that the rotating member is obscured from direct view by a user when the device is in a normal operating position, a rotation indicating device comprising:

  • a permanent magnet mounted on the rotating member, the magnet being radially spaced from the axis of rotation of the member, the magnet revolving in a circular path about said axis, said revolving occurring in a plane perpendicular to said axis of rotation, said magnet having a north pole face and an opposed south pole face, one of said pole faces facing inwardly toward said axis of rotation, the other of said pole faces facing outwardly from said axis of rotation;

    a coil having an elongated ferromagnetic core lying along a center axis coinciding with a line extending radially from said axis of rotation, said line extending in said plane, said coil including a large plurality of conductor turns wound about and along the length of said core, said coil being cylindrically shaped, one end of said cylindrically shaped coil being mounted on said housing and being positioned adjacent to the said circular path of said revolving magnet wherein magnetic flux derived from said magnet cuts the turns of said coil as the magnet moves past said one end of said cylindrically shaped coil, wherein said coil generates a cycle of alternating current voltage each time said magnet passes by said one end of the cylindrical coil; and

    a light-emitting diode mounted on said housing and readily visible to said user, the light-emitting diode being electrically connected to the coil and being illuminated solely by a rectified portion of cycles of said alternating current voltage.

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