PURPOSE: To simplify the shape of a core member and to improve the frequency characteristics, by forming a plurality of ribs radially for the core member and sequentially reducing the height of the ribs from the center to the external circumference.
CONSTITUTION: In Figure, 1 is a core member and 2 is surface member sticked to upper and lower surfaces of the core member 1. A plurality of ribs 3 are radially incorporated on the core member 3, and the ribs 3 are continuously provided toward the circumference direction with uneveness. The ribs 3 are provided radially with their height being sequentially reduced from the center to the external circumference, and one rib 3 is constituted to almost triangular pyramid with two square surface elements 4 and 5.
TAKEUCHI HIROSHI
MURATA KOUSAKU
TAKAYAMA SATOSHI
| JP54117229B |