Dust trap and valve with auxiliary pressure equalizing valve

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) a valve seat defining an opening, a matching valve flap, and an articulated single arm drive train having flap connecting means for supporting said flap to move the same in response to movement of said drive train into and out of closing engagement with said valve seat;
• (b) said flap connecting means including as an integral part thereof, a two-piece pressure regulating valve comprising a port and a matching plunger, with the port being defined by said flap to provide for a flow therethrough when said plunger is displaced from said port, said flap having a shield on the side opposite said plunger and substantially covering said port to prevent clogging of said pressure regulating valve;
• (c) said plunger and said flap each having a common connection to said articulated drive train in a manner to provide for a predetermined incremental movement of said plunger in either direction before said flap responds to the movement of said train, whereby when said drive train is actuated to move said flap towards its open position, said plunger is withdrawn from said port to first release and balance the pressure across said flap before said flap is removed from its valve seat and whereby said plunger positively closes said port before the flap is moved toward its closed position.