초록 ▼

In a method of producing a double-walled structure, such as a silencer for use in a ventilation duct system, use is made of an arrangement having a forming head for forming helically-wound lock-seam tubing. In the forming head, a perforated metal strip is helically would together with an air-permeab

In a method of producing a double-walled structure, such as a silencer for use in a ventilation duct system, use is made of an arrangement having a forming head for forming helically-wound lock-seam tubing. In the forming head, a perforated metal strip is helically would together with an air-permeable cloth strip such that the tubing fed out of the forming head has an outer cover of said cloth. The tube assembly consisting of the perforated tube and the cloth cover is provided with an outer tubular layer of insulating material and then inserted in a casing which makes the silencer complete.

대표청구항 ▼

[ What we claim and desire to secure by Letters Patent is:] [1.] A double-walled structure, comprising:an inner tube having a perforated wall;an outer casing spaced from and enclosing said inner tube;a filler material provided between said inner tube and said casing; anda fluid-permeable cover tight

[ What we claim and desire to secure by Letters Patent is:] [1.] A double-walled structure, comprising:an inner tube having a perforated wall;an outer casing spaced from and enclosing said inner tube;a filler material provided between said inner tube and said casing; anda fluid-permeable cover tightly applied on the outside of said inner tube and covering said perforated wall of said inner tube;wherein said inner tube is a helically-wound lock-seam tube formed from a first perforated strip; andwherein said fluid-permeable cover is formed from a second strip helically would together with said first strip.