Patent CZ-300247-B6 (CZ)
Title: Double-walled structure, method for producing thereof, arrangement for producing such double-walled structure and double-walled silencer
Inventor: HULTBERG KENT
IPC: F16L59/14
Filed: 1998-01-26
Abstract: In the present invention, there is disclosed a double-walled structure, comprising: an inner tube (2) having a perforated wall; an outer casing (20) spaced from and enclosing the inner tube (2); a filler material (19) provided between the inner tube (2) and the casing (20); and a fluid-permeable cover (13) tightly applied to the outside of the inner tube (2) and covering the perforated wall of the inner tube (2). The inner tube (2) is a helically wound lock-seam tube formed from a first perforated strip (7). The fluid-permeable cover is formed from a second strip (13) helically wound together with the first perforated strip (7) wherein said fluid-permeable second strip (13) has its longitudinal edge portions (16, 17) secured in the helical lock seam (12) of the inner tube (2). There is also disclosed a method for producing the above-described double-walled structure, characterized by the steps of: applying a strip (13) of a fluid-permeable material to a perforated strip (7) to form a composite strip (7, 13); helically forming said composite strip (7, 13) in a forming head (5) to form a helically-wound lock-seam tube (2), the outside surface of which being tightly covered by said fluid-permeable material; cutting the tube (2) to a predetermined length; applying a filler material (19) to the outer surface of the tube such that the tube and the filler material form an assembly (2, 19); and enclosing the assembly (2, 19) in a casing (20), wherein the longitudinal edge portions (16, 17) of the strip (13) of fluid-permeable material are secured in a helical lock seam (12) formed in the tube (2). There is further disclosed an arrangement for producing the above-described double-walled structure, characterized in that it comprises a forming head (5) for forming a helically-wound lock-seam tubing (2); means for applying a strip (13) of a fluid-permeable material to a perforated strip (7) to form a composite strip (7, 13); means for helically forming said composite strip (7, 13) in the forming head (5); a cutting unit (11) for cutting the tube (2) to a predetermined length; apparatus (3) for applying a filler material (19) to the outside surface of the tube (2) such that the tube and the filler material form an assembly (2, 19); means for enclosing the assembly (2, 19) in a casing (20), and means for securing longitudinal edge portions (16, 17) of the strip (13) of fluid-permeable material a helical lock seam (12) formed in the tube (2). There is also disclosed a double-walled silencer structure for use in a ventilation duct system, characterized in that it comprises an inner tube (2) having a perforated wall; an outer tube (20) spaced from and enclosing the inner tube (2); a tubular space defined by the inner tube (2) and the outer tube (20); a sound-absorbing material (19) provided in and filling up said space between the inner tube (2) and the outer tube (20) wherein the inner tube is a helically-wound lock-seam tube (2) formed from a perforated metal strip (7). The silencer structure further comprises an air-permeable cover of a cloth material (13) tightly applied to the outside surface of the inner tube (2) and covering the perforated wall of the inner tube (2) wherein the cloth cover is formed from a strip (13) helically wound together with the metal strip (7) and has its longitudinal edge portions (16, 17) secured in the helical lock seam (12) of the inner tube (2).