| 摘要 |
Perforated conditioning sacks of synthetic material are e.g. in the form of thread, to aerate the product handled. Rectangular parallel perforations are formed in a continuous strip of synthetic material, the edges being unaffected and forming selvedges with continuous surfaces. The perforated strip is then fitted to a cylindrical mandrel so as to shape it into a tube, the selvedges overlapping and being welded together. The tube is then closed at the bottom and filled, the contents holding the perforations open, and finally closed at the top. |
