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Method and apparatus for measuring air permeability of a wall-like or sheet-like element

  • US 4,756,183 A
  • Filed: 04/18/1987
  • Issued: 07/12/1988
  • Est. Priority Date: 04/10/1986
  • Status: Expired due to Fees
First Claim
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1. A method for measuring the permeability to air of a wall-like or sheet-like element having opposite surfaces defining the thickness of the element between them, such as a felt or wire used in paper machines, utilizing a blower including an air discharge nozzle, a blade wheel and variable-speed motor means for rotating said blade wheel to produce an air flow which discharges through said nozzle, comprising the steps of:

  • locating said blower with said discharge nozzle against one of the surfaces of said element and operating said motor means to rotate said wheel to produce a volumetric air flow through the thickness of said element and a corresponding pressure in said blower;

    detecting said pressure in said blower, and generating a pressure measurement signal indicative of the magnitude of said pressure which is input to a central unit coupled to said blower and, at the same time,detecting the speed of rotation of said blade wheel of said blower and generating a speed measurement signal indicative of the magnitude of said wheel rotational speed which is input to said central unit;

    operating said central unit to adjust the speed of rotation of said blade wheel by adjusting the speed of said motor until said blower pressure is substantially equal to a predetermined standard value at which time said speed measurement signal input to said central unit corresponds to said predetermined standard blower pressure;

    determining the permeability value of the element at said central unit based on a previously determined relationship between the values of speed measurement signals corresponding to said predetermined standard blower pressure and corresponding permeabilities; and

    pre-programming said central unit with said relationship between the values of speed measurement signals corresponding to said predetermined standard blower pressure and corresponding permeabilities.

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