| 摘要 |
PROBLEM TO BE SOLVED: To reduce the time required for the ultrasonic welding of a welding boss and to improve the welding stability by increasing the transmission efficiency of the ultrasonic oscillation energy to the welding boss. SOLUTION: The boss part 15 of a lower reel 16 is provided with a side wall 22 which forms the winding surface of a magnetic tape, on the circumference separated in the radial direction from a center part 21 of the boss and further constituted in such a manner that the center part 21 of boss and the side wall 22 are connected by plural ribs 23 arranged along the radial direction of the boss part 15. Each rib 23 is provided along the radial direction of the boss part 15 respectively between the specified positions keeping away base end parts 24 of the welding boss 20 on the side surface 21a of the center part 21 of boss and the inner surface 22a of the side wall 22, and the gap is arranged therein against the welding boss 20.
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