Device in ventilation ducts provided with adjustable filter means

An arrangement of ventilation plants comprising ducts in which longitudinal filters are mounted with open end portions sealingly attached to walls of the ducts, and balancing of the air flows in the ducts of the plants is achieved by required individual throttling of the air throughflow capacity of the filters by adjustment of a length of the filters, at least one of said filters enclosed by a tubular air pervious casing that is longer than the filter and has end portions that are axially fixed, and a linear feeding device including an attachment member movable back and forth along a longitudinal direction of said filter and a casing, said actuating member including a ring-shaped member with an opening with a substantially smaller diameter than a diameter of the filter, through which opening the casing extends and brings about a pressure of the ring-shaped member against the outside of the filter and, when the actuating member is applied against the end portion of the filter, is moved along an extension of the filter.

In an arrangement of ventilation plants including ducts in which bag-shaped filters are mounted with open end portions sealingly attached to walls of the ducts, and balancing of the air flows in the ducts of the plants is achieved by individual throttling of the air throughflow capacity of the filters by adjustment of a length of the filters, the improvement comprising a linear feeding device associated with at least one of said filters, said device having an actuating member operatively associated with the closed end of the filter to adjust the operative filter length of said at least one filter.