Patent ID: 6508406
Filing Date: 2003-01-21
Classification: G05D,Y10S

Abstract:
A fail-safe proportional mixing valve assembly, comprising:a valve body defining a mixing chamber; a cold fluid inlet in communication with said mixing chamber and connected to a supply of a first flow of a cold fluid; a hot fluid inlet in communication with said mixing chamber and connected to a supply of a second flow of a hot fluid; a fluid outlet in communication with said mixing chamber for discharge of fluid therefrom, wherein said cold fluid inlet and said hot fluid inlet are proportionately sized to temper the hot fluid within said mixing chamber below a predetermined set point temperature; and failure responsive means for substantially restricting said second flow of hot fluid into said mixing chamber upon a failure of said first flow of cold fluid, said failure responsive means being at least partially disposed within said mixing chamber and including; a thermal expansion member disposed in said mixing chamber that volumetrically changes in proportion to the fluid temperature in the mixing chamber; a plug disposed between said hot fluid inlet and said mixing chamber and engaged to said thermal expansion member to move with said member from an open position which allows substantially full flow from said hot fluid inlet into said mixing chamber, to a closed position in which said plug substantially restricts flow from said hot fluid inlet; and biasing means for biasing said plug to said open position when the temperature of fluid within said mixing chamber is below said set point.