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Self-cleaning system for monitoring the opacity of combustion engine exhaust using venturi effect

  • US 5,424,842 A
  • Filed: 09/16/1994
  • Issued: 06/13/1995
  • Est. Priority Date: 04/27/1993
  • Status: Expired due to Term
First Claim
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1. A self-cleaning smoke-monitoring system for use in measuring opacity of exhaust from an internal combustion engine, comprising:

  • an exhaust pipe attached to the engine for conveying exhaust from the engine;

    a light source and sensor combination defining an optical path therebetween that traverses said exhaust pipe;

    a first air duct having a first outlet that opens into said exhaust pipe and a portion that coincides with said optical path;

    a first window positioned in said optical path and attached to said first air duct, said light source being positioned outside said first air duct and adjacent said first window;

    a second air duct having a second outlet that opens into said exhaust pipe and a portion that coincides with said optical path;

    a second window positioned in said optical path and attached to said second air duct, said sensor being positioned outside said second air duct and adjacent said second window;

    inlet means attached to said air ducts for supplying ambient air to said air ducts;

    filter means attached to said air ducts for removing particulate matter from ambient air entering said air ducts through said inlet means; and

    a portion of said first air duct between said first window and said first outlet, and a portion of said second air duct between said second window and said second outlet, extending into said exhaust pipe and restricting the cross-sectional area of said exhaust pipe to create a venturi effect in the vicinity of said first and second outlets when the engine is running such that the fluid pressure of the exhaust from the engine adjacent said outlets is lower than the air pressure at said inlet means, said venturi effect causing air to be pulled through said first and second air ducts to thereby prevent said exhaust from contaminating said first and second windows.

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