Filter for gas filtration

Claim 1

In a filter constructed of an upper dome housing and a mated lower housing and a hydrophobic filter disc for gas filtration sandwiched between them, intended in particular for a gas exchange between a container partially filled with liquid and the surrounding atmosphere: (a) the upper housing has an integral upper filter support forming upper channels, the upper channels terminate into a gas inlet-outlet located in the upper housing part, (b) the mated lower housing has an integral lower filter support forming lower channels, the lower channels terminate into a bore which run approximately perpendicular to the filter support, (c) the hydrophobic filter disc is connected at its periphery between the upper and the lower housing parts as a selectively permeable partition, whereby the filter disc contacts the one or the other filter support as a function of the direction of the pressure gradient, the improvement comprising: (1) the filter support of the lower housing part has a planar plane and the lower channels include an annular channel at least 2 mm wide in the area of the periphery of the filter disc and include at least one radially extending lower channel fluidly connecting the bore and said annular channel, (2) the radially extending lower channel widens out from the vicinity of the bore from between about 0.5 to 2 mm, in the direction of the annular channel to between about 3 to 10 mm, (3) in the area of the bore the radially extending channel has a depth of between about 0.3 to 0.8 mm, and becomes deeper in the direction of the annular channel to between about 1.1 mm to 1.6 mm, (4) the bore possesses a length of between about 0.5 mm to 3 mm, and has a diameter of between about 0.5 mm to 4 mm, with it being less at the proximate confluence of the filter support than at the distal end of the bore.