| 摘要 |
<p>PURPOSE:To abolish conventional ribs by integrally forming a rib frame to plate form with plywood or the like, opening plural holes therein and providing rib functions to the portions segmenting these holes. CONSTITUTION:A rib frame 20 is integrally formed by particle board to approximately the same size as that of a soundboard 4. It is formed with a multiplicity of slender holes 21 in its diagonal direction opened in the plate thickness directions and its top surface is curved to convex form to about the crown that the soundboard 4 has. Ribs 22 have the function as conventional ribs and extend in the direction crossing the woodgrain direction A of the soundboard 4. The soundboard 4 is bonded to the top surface of the rib frame 3. If such rib frame 20 is used, work is rationalized and it is helpful for cost reduction.</p> |
