Importance

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Abstract

A die arm 34 and a punch 35 to be used to punch a hole are inserted into chambers 21 and 22 lying parallel to each other along the direction of ventilation through openings located on one side of the chambers along the lengthwise direction. A partition portion 20 has a small wall thickness T1 relative to the wall thicknesses of partition portions in the related art, in a range of equal to or greater than 0.4 mm and equal to or less than 1.65 mm, so as to ensure that the punch unit achieves a high enough level of fatigue resistance to assure a specific number of uses without a failure even though the fulcrum and the power point of the die arm 34 and the punch 35 are not on a single axis along the operating direction and also that the partition portion 20 with the smaller wall thickness still has sufficient strength to prevent deformation. Consequently, the partition portion of a tank manufactured through extrusion molding achieves an optimal wall thickness for the formation of a communication passage at the partition portion in a post-process.

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First Claim