Method of controlling delivery conditions in a pneumatic conveyor line, and mill pneumatics for implementing this method

Claim 1

In a pneumatic conveying system of the type including a separator, constructed as a cyclone, having an inlet connected to a conveyor line, an air outlet connected to an air collecting line and a product outlet; an air flow valve downstream of the air outlet of the cyclone; and control means pneumatically coupled to a first pressure measuring point on the conveyor line ahead of the cyclone inlet and to a second pressure measuring point downstream of said cyclone air outlet, said control means being responsive to the pressure difference between said first and second pressure measuring points to control said air flow valve, the improvement comprising: immersion tube means connected at a first end to said air flow valve and projecting within said cyclone at a second end; said air flow valve comprising an enclosure with partly superimposed upper and lower chambers separated by a wall, the lower chamber being directly connected to the immersion tube means and the upper chamber being connected to the air collecting line, a passageway in said wall providing communication between said upper and lower chambers, and movable throttle means interposed in said passageway for controlling air flow therethrough; said control means including a control chamber coupled through a sealed membrane to the lower air flow valve chamber and pneumatically coupled directly to the first pressure measuring point, and a regulating valve having an inlet coupled to a source of compressed air, an outlet, and a regulating member mechanically coupled to said sealed membrane and being positionable to control the pneumatic coupling between said regulator valve inlet and outlet; and a pneumatically operated force member pneumatically coupled with said regulating valve outlet and mechanically coupled to move said throttle means to control the air flow in said passageway.