| 摘要 |
PROBLEM TO BE SOLVED: To provide a drum with plastic collars having improved durability and shock resistance by improving strength of the outside circumferential edge of each disc-like collar. SOLUTION: A cross-sectionally nearly I-shaped annular surrounding part 11 comprising an outermost circumferential rib 9 and a circumference rib 10 immediately inside it is integrally formed in the circumference of each disc-like collar 2. A plurality of connection ribs 12 and 13 for connecting the outermost circumferential rib and the circumference rib are integrally formed on both surfaces of each annular surrounding part. The connection ribs 12 and 13 are formed in a zigzag shape tilting with respect to the radial direction. The connection ribs 12 and 13 are formed by shifting the positions thereof from one another on both surfaces of the surrounding part 11. COPYRIGHT: (C)2003,JPO
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