| 摘要 |
<p>A dot display assembly has a three-position rotor (25) carrying a dot display disk (32) for use as a portion of a matrix of dots in a variable message sign. The assembly has a stator (9) including a support (18) carrying reversely magnetizable separate magnetic cores (20, 22) on which are separate electrically energizable coils (23). The rotor (25) which is carried by the support has a shaft (26) rotated axially perpendicular to the cores (20, 22). A permanent magnet (42) on the rotor (25) is adjacent to the cores (20, 22) to interact magnetically with them and rotate the shaft (26) selectively to any one of three rotor positions, by selective energization of the coils (23), the middle position being achieved by ensuring that the upper end of core (20) defines an S pole whilst the upper end of core (22) defines an N pole. The display disk (32) has a peripheral display edge (32X) and two opposite display sides (34, 36), and is mounted on the shaft (26) for selective display of said edge or either of the display sides in a viewing direction V. The disk (32) may be replaced by a unit of three disks providing three exposed display sides.</p> |
