Air flow control unit

Claim 1

For use with an internal combustion engine having an exhaust system and an air pump for delivering air to said exhaust system, an air flow control unit comprising a housing, a diaphragm closing one end of said housing, a valve stem actuated by said diaphragm and extending from said diaphragm axially into said housing, a valve member secured to said valve stem, said housing defining a valve chamber about said valve member, said chamber having a lateral inlet for receiving air from said pump and a main outlet for discharging air to said exhaust system, said main outlet being axially aligned with said valve stem and having a valve seat formed thereabout for receiving said valve member, an annular insert member disposed between said diaphragm and said valve chamber, said insert member surrounding and guiding said valve stem, said insert member and said housing defining an annular silencing chamber therebetween, said insert member sealing said diaphragm from said valve chamber and said silencing chamber and further sealing said valve chamber from said silencing chamber, said insert member having a cylindrical recess opening from said valve chamber, said recess being aligned coaxially with said valve stem and having a valve seat formed thereabout for receiving said valve member, said insert having a pair of diametrically disposed apertures opening laterally from said recess into said silencing chamber, said housing having a pressure relief passage including a portion opening laterally from said valve chamber and a portion extending axially to said silencing chamber, a pressure relief valve disposed in said pressure relief passage, said laterally opening portion of said pressure relief passage having a pressure relief valve seat formed thereabout for receiving said pressure relief valve, spring means biasing said pressure relief valve into engagement with said pressure relief valve seat, said pressure relief passage and one of said insert apertures discharging into radially aligned portions of said silencing chamber, said housing having two apertures opening from said silencing chamber to the atmosphere on the side of said housing adjacent said one of said insert apertures, said housing apertures being circumferentially spaced one from the other and each from said pressure relief passage, said housing further having three circumferentially spaced apertures opening from said silencing chamber to the atmosphere on the side of said housing adjacent the other of said insert apertures, a felted polyester fiber silencing material disposed in said annular region, said silencing material having been axially needled and having a density in a range of from about .006 to about .007 pounds per cubic inch, whereby said diaphragm may actuate said valve stem to move said valve member from engagement with said insert valve seat into engagement with said main outlet valve seat to thereby divert all air flow from said inlet through said valve chamber into said recess through said insert apertures, said silencing material and said housing apertures and whereby said pressure relief valve member may open against the bias of said spring at a selected pressure to permit air flow from said inlet through said valve chamber, said pressure relief passage, said silencing material and said housing apertures, said housing apertures having smaller air flow areas than said insert apertures and said pressure relief passage and being disposed at an axial position spaced from the axial position of said insert apertures whereby air flow through said silencing material has radial, axial and circumferential components, and an annular screen surrounding said silencing material and covering said housing apertures to prevent said silencing material from extending into said housing apertures.