Automatic fluid flow regulator

A device for regulating the airflow rate in an air distribution system comprising:

• a housing having two ends, one end defining an air inlet passageway and a second end sealably engaging a discharge duct, said duct having a lateral wall with at least one aperture therein;
• flow restricting means mounted within said duct adjacent said aperture and axially displaceable therein in response to pressure differentials between the portions of the air in said distribution system upstream and downstream from said regulating device, said flow restricting means including an axially extending shaft and a piston slideably mounted on said shaft and axially displaceable coincident with said aperture in response to said pressure differentials;
• spring means mounted on said shaft downstream from said piston and having a predetermined non-linear coefficient of stiffness for yieldably resisting the downstream displacement of said flow restricting means;
• said aperture and said flow restricting means together comprising means for forming a variable area airflow passageway through which substantially all the air must flow in passing through said regulating device;
• and
• said aperture having a size and shape including axial continuity and a continuously decreasing transverse dimension along the entire length of travel of said flow restricting means, and said spring coefficient of stiffness having a non-linear value such that the displacement of said flow restricting means is inversely proportional to the logarithm of the area of said fluid flow passageway continually along the entire length of travel of said flow restricting means.