Drive unit for a rotary decoration

摘要

A drive unit for a rotary decoration has a transmission gear train configured to include a damper such as a coil spring and is capable of imparting a visually elegant swing motion to the rotary decoration. A reciprocating stepping motor is capable of rotating or turning in both the forward and reverse directions to drive a rotary decoration in such a manner that the rotary decoration exhibits a reciprocative swing motion over a specified angular displacement. A memory circuit stores data for determining the drive timing of the stepping motor. A control circuit controls the stepping motor in accordance with the data stored in the memory circuit. The data represents the interval between drive pulses supplied to the stepping motor so as to cause the rotational speed of the rotary decoration to vary according to a sine curve. In alternative embodiments, (1) the intervals between drive pulses are set to a uniform and short value in a predetermined region of the specified angular displacement; (2) the intervals between drive pulses are set to a short value in a predetermined region of the specified angular displacement which corresponds to the location immediately after which the rotational direction of the rotary decoration is reversed; and (3) the drive pulses are blanked over a predetermined region corresponding to the location immediately before the rotational direction of the rotary decoration is reversed.