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Image Number 2 for United States Patent #7654220.
An indicator has a permanent magnet and a coil rotatably supported on the permanent magnet and wound so as to form a surface that is parallel to and disposed at a preselected distance from a bottom surface of the permanent magnet. The coil generates a torque by interaction with a magnetic field of the permanent magnet upon supply of a current to the coil. An indicator needle is mounted to undergo rotation with the coil through a range of angles corresponding to indicator angles of the indicator needle. A pair of spiral springs urge the indicator needle in a direction opposite to a direction of the torque to undergo rotation through the range of indicator angles. The pair of spiral springs comprise a first spiral spring connected at one end thereof to one end of the coil and a second spiral spring connected at one end thereof to another end of the coil. The first spiral spring is larger than the second spiral spring and is arranged on an outer peripheral side of and coaxially with the second spiral spring so that the first and second spiral springs lie on a common plane.
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