In ventilation systems, the ventilation air is admitted to the room through openings in the wall or ceiling and such openings are fitted with a removable ventilation elements, normally air valves, diffusers or grilles for supplying and exhausting air. The conduits to which the elements are connected may be of varying widths or diameters and may even vary in type. Frequently the conduit is simply an opening in a concrete wall and such conduits are often uneven and include a great number of varying irregularities.
If the conduit embodies a standard piece of duct work or other pre-formed conduit, the ventilation element may be designed to mate with the pre-formed conduit and may be screwed in place or glued by suitable sealing cement. However, where it is desirable to permit ready removal and replacement of the ventilation element, it has been proposed to provide spring latches which releasably mount the ventilation element in the duct. Such devices are normally not suitable unless the ventilation element has a cylindrical portion which telescopically engages in the duct conduit to position the same. In such cases, the latch element may comprise a special expanding member on the cylindrical portion which springs out to engage the conduit and secure it in position.
In order to solve these problems, a mounting arrangement has been provided in which the ventilation element is provided with resilient brackets which may spring outwardly against or behind an irregularity or a shoulder. The resilient element then is designed either to pass "over-center", or to act as a cam element to resiliently cause the ventilation element to bear tightly against the wall surface surrounding the ventilation opening.
The foregoing mounting apparatuses are not entirely satisfactory, because of their complicated construction and assembly, their expense, and their inability to adapt to openings which are quite irregular.