| 摘要 |
PROBLEM TO BE SOLVED: To enable the discarding and incinerating disposal of a non-metallic sheet material with plural punched through holes to be easily performed by joining the ends of the sheet material, when a tubular body with holes for supporting the filter paper or the like of a filter element, in an oil treatment filter or the like used in an automobile. SOLUTION: First, a non-metallic sheet material 21 prepared is perforated by punching and a part of both end parts of the sheet material 21 is bent inwardly as an end part bending process. Next, the intermediate part bending process is performed to form the intermediate part into a recess shape. After that, one bent end or one unbent end of both end parts is bent inwardly to be fixed as a one-end part fixing process. Further, the other end is bent and lapped on the one end and fixed together as an other-end part lapping/fixing process. Finally, the end parts of the lapped part are joined to obtain a complete tubular body with holes 30. The non-metallic sheet material 21 to be used is a sheet material made of a paper material, a mixed paper or the like. When the upper is made, it is impregnated with a curable resin or this resin is applied to the paper, according to necessity.
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