| 摘要 |
<p>Measurement head for the measurement of the porosity of a moving web (1) of porous material. The measurement chamber (2) of the measurement head is covered by a measurement plate (3) in which measurement apertures (4) are provided. To measure the porosity, air is sucked through the porous web (1) and through the orifices (4) into the chamber (2). The quantity of air flowing through the chamber (2) is measured on an installation connected to a measurement air stub pipe (5) and serves as a measurement for the porosity of the web (1). The plate (3) is surrounded by a guide plate (7), which partly covers a blower ring (9). The guide plate (7) and blower ring (9) together form a blower slot (14) running around the measurement plate (3), the outlet opening (15) of said slot being oriented outwards tangentially to the blower side of the moving web (1). The necessary blowing air is fed into an annular duct (12) via a connection stop (13), said duct being formed by a semi-circular groove (11) in the blower ring (9) and passing into the blower slot (14). The blowing air flowing out horizontally from the outlet orifice (15) produces a negative pressure between the lower side of the moving web (1) and the convex surface of the blower ring (9). As a result of this negative pressure, the web (1) is pressed on the edge of the guide plate (7), so that the measurement chamber (2) is sealed naturally and air can then only flow into the measurement orifices (4). Between the measurement orifices (4) in the measurement plate (3) and the measurement air stub pipe (5) a filter (18) can be provided. An additional extraction stub pipe (22) enables cleaning of the filter (18) and the measurement chamber (2) by the scavenging air fed through the measurement air stub pipe (5).</p> |
