29 each merge into an outer section 27 30 the inner sections 26 29 and the outer section 27 30 lie with their central axes on a common longitudinal axis 31 the outer section 27 of the inlet duct 25 is formed as a gas inlet and has in the region of its free end a thread 46 preferably formed as vg8 valve thread for the connection onto a gas pressure source not shown in fig1 the outer section 30 of the outlet duct 28 is provided with a portion 48 of reduced diameter with hook like coupling elements 49 formed onto its outer side which serves for the connection to a filling line which will be explained in more detail in the following with reference to fig2 via which the sealing apparatus can be connected to an article to be sealed whereas the free inner cross sectional areas of the inlet duct 25 and of the outlet duct 28 are of the same size the outer section 30 of the outlet duct 28 has a greater wall thickness than the outer section 27 of the inlet duct 25 in deviation from the illustrated embodiment the free inner cross sectional areas of the inlet duct 25 and of the outlet duct 28 can also be of different size the inner section 26 of the inlet duct 25 merges into an inflow passage 50 the longitudinal axis of which coincides with the longitudinal axis 23 of the connection stub 22 and the free inner cross sectional area of which is smaller than that of the inner section 26 the inflow passage 50 projects into the connection stub 22 of.