Dust trap with removable valve seat

Claim 1

In a dust trap which defines a flow path axially therethrough, a device positioned within said dust trap and in said flow path for controlling the flow therethrough, comprising: a valve seat defining a central opening, means removably securing said valve seat in said dust trap comprising a pair of matching flange surfaces, one on said dust trap and one on said valve seat, with bolts securing said surfaces together, a matching valve flap for covering said valve seat opening, means independent of said valve seat supporting said valve flap for movement into and out of sealing engagement with said valve seat; said dust trap having a number of sides at least two of which are opposite and parallel, providing a polygonal cross section to define said axial flow path; said valve seat having a number of sides equal to and complementary to those of said valve body to provide a corresponding cross section; one of said dust trap sides transverse to said parallel sides defining a port including a removable port cover of a size to permit said valve seat to be slid laterally from said valve body through said port when unbolted; and, said dust trap and said valve seat flange surfaces having complementary matching ledges to support said valve seat in a predetermined location, while permitting supported lateral movement of said valve seat outwardly from said trap through said port, whereby said valve seat may be removed from or replaced in said dust trap, and permitting said valve seat to be guided laterally along the axis of said flanges; and, said valve seat ledge is axially displaced from said dust trap ledge by a distance greater than the thickness of the valve seat flange to permit the valve seat to be lowered onto and raised above said dust trap ledge during insertion and removal.