| 摘要 |
PURPOSE:To prevent the printing sound from leaking out directly through an opening part, by providing a printing head with a conical casing for radiating the printing sound in a direction substantially opposite to the opening part of an outlet for a printing paper. CONSTITUTION:The printing sound has a repetition frequency of dots for a series of printing, in which the greatest is a harmonic frequency component having a frequency band of not less than several kHz and a wavelength of about 10cm. The conical casing 12 having a size approximate to the wavelength is provided so that an opening thereof is directed oppositely to the opening part 5 of the outlet for the printing paper 4, whereby the printing sound is radiated upward. The radiant sound collides against a sound-absorbing material 13 adhered to the inside surface of a cover 7, whereby most of the sound energy is absorbed. Although the rest of the radiant sound leaks through the opening part 5, the sound constituting the major part of the printing sound and reaching the opening part 5 can be greatly reduced. In addition, the heat of the printing head 3 is also radiated by the casing 12. |
