| 摘要 |
A ventilation duct consists of a refractory fibre material and binder agent and has longitudinal wall sections (1-5, 9) and longitudinal fold- or joint lines (7) located there between. According to the invention, the wall sections (1-5) between the fold- or joint lines (7), have longitudinal, thickened and outwardly bulging portions (17), in which longitudinal rigidifying elements (8) are disposed. A method of manufacturing the ventilation duct comprises the steps that the duct is manufactured in the planar, spread-out state, that the wall sections (9) which are located along opposing edges of the spread-out duct, are given a configuration which corresponds the configuration of half of the other wall sections (1-5), whereby the duct, after raising to the intended configuration, is given a longitudinal joint (10) where the half wall sections (11, 12) meet one another. |
