Mixing of gaseous substances

Claim 1

Apparatus for the controlled mixing of two gasses supplied by two separate sources, comprising: a plurality of identical capillary tubes; a distributor device; two connectors each defining a respective inlet to said distributor device and each connectable to a respective one of said sources; said distributor device being arranged to connect each said inlet to a different group composed of a selected number of said capillary tubes for supplying a respective one of said gasses to each respective group; a mixing chamber communicating with said capillary tubes for receiving said gasses therefrom and forming a gaseous mixture of said gasses; and an outlet duct connected to said mixing chamber for receiving said gaseous mixture therefrom and supplying it to an outlet connector defining an outlet from the apparatus, said gaseous mixture containing said two gasses in proprotions which differ according to the number of capillaries in each said group, said distributor device comprising: a first intake manifold connected to a first connector of said two connectors; a first plurality of outlet ducts from said first intake manifold; a second intake manifold connected to the other connector of said two connectors; a second plurality of outlet ducts from said second intake manifold; a plurality of valves each of which is connected to a respective outlet duct of said first plurality of outlet ducts, to a respective outlet duct of said second plurality of outlet ducts, and to a first end of a respective capillary tube, each said valve being operable independently to put the respective capillary tube into communication with a selected one of said outlet ducts, each manifold being connected to a respective one of said connectors through a respective pressure regulator and a respective vent duct having constriction means therein being provided downstream of the pressure regulator for partially venting gas from the respective source from the apparatus.