With structural parts or bodies that are movable relative to each other, sealing is quite difficult, because sealings of ordinary type, being more or less elastic and having a given shape, wear easily out when the parts are moved. In other applications, e.g. for tube switches, expandable sealings have been suggested which are inflated only if the respective body is motionless and is to be sealed. Such sealings engage, in general, a flat surface which does not cause any problem. An example of an inflatable sealing which engages a flat surface is disclosed in EP-B-0 114 278.
More difficult is it, however, if rounded parts, for example a connected container or a shutter valve and to be sealed. This is why an inflatable sealing has not become known for such applications.
An inflatable sealing ring can be fastened to the respective radially outer part so as to be pressed by pressurized air against a radially inner part. This involves an advantageous possibility of supply of pressurized air from the exterior. However, it has been found that the service life of such sealings is relatively short so that they are not distinguished from non-inflatable elastic sealings of a substantially given shape in this respect. It is clear that this is one reason why this suggestion has not been used any further.