n ',.essentially predetermined position within the 'bell- E t rnal operable valve V-l by which an inert gas such as carbon dioxide, -,nitrogen, etc., may be introduced from a tank T. Similarly; the manually operable valve ii-'4 permits evacuationby a suitable means suchlas a suction conduit M and 'a filter N. In the illustrated form.-thegassing and evacuation conduits are connected to a common co