Device for testing the air permeability of an article

An improved device for testing the air permeability of an article, and particularly felts and screens associated with the manufacture of paper products, said device being of the type including a measuring channel through which air is propelled through utilization of a blower mechanism, and including measuring means for measuring the flow rate of air within said measuring channel, said air being propelled through a measuring area immediately adjacent the exposed surface of said article as a function of a controlled constant pressure differences created at said adjacent measuring area, said device further being of the type including a longitudinal positioned belt channel juxtaposed about said measuring channel in which said belt channel is additionally and operably directing propelled air from said blower mechanism, wherein said measuring channel and said belt channel each further include an orifice immediately adjacent to the exposed surface of said article, said improvement in said air permeability testing device further comprising:

• said blower mechanism, said measuring channel, said measuring means for determining the rate of air flow in said measuring channel, said measuring area and said belt channel being integrated into a single operational testing device capable of being placed for air permeability testing to one of either of two sides of said article being tested;
• said measuring means comprising a fan wheel anemometer having a fan wheel element operably positioned within said measuring channel for direct exposure to the air being propelled therewithin;
• said measuring channel containing said fan wheel anemometer wheel element being operably connected to said orifice of said measuring channel immediately adjacent to said article through a channel section element, immediately adjacent said measuring channel orifice having a substantially cylindrical longitudinal construction, with said channel section further and operably being attached to a tappered longitudinal section emanating towards said measuring means in order to insure that said propelled air stream is unidirectional;
• said air permeability testing device further including in at least one position upstream from said fan wheel element of said fan wheel anemometer, flow rectifier means for precluding the creation of rotational flows of propelled air onto the surface of said fan wheel element,
• said substantially cylindrical longitudinal section immediately adjacent said measuring channel area having one or more sensing means operably associated therewithin for measuring the extent of static pressure created at said area of measuring channel, for the purpose of regulating the rotational speed of the blower mechanism so as to maintain a desired static pressure value;
• one or more of said belt channel and said measuring channel means being of such a geometric configuration so as to equalize the propelled air flow volume and velocity longitudinally conducted through said belt channel to the propelled air flow volume and velocity longitudinally directed through said measuring channel.