| 摘要 |
A piercing apparatus for forming partially overlapped small holes in upper and lower layers of lining material includes upper and lower piercing stands having piercing members affixed thereto respectively. The upper and lower piercing members have engaging cut-out portions corresponding to a shape of the overlap desired between the holes. When holes are formed for a first layer of lining material, the material is positioned between upper and lower stands mounting the piecing members and the lower piercing member is driven up to cut-out the shape of the opening for the first layer except for the overlap area. Then as the lower piercing member is driven up further, the leading edge of its cut-out portion engages the trailing edge of the corresponding cut-out portion of the upper piercing member. At this time the shape of the overlap portion is cut from the first layer of lining material. When the openings for the second layer of lining material are to be formed, the above operation is reversed and the opening may be shaped and positioned with a single apparatus.
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