Abstract: Pneumatic conveyor apparatus for conveying particulate material in successive plugs separated by gas-filled spaces, comprising a take-off chamber connecting a supply source to a pressurizing chamber through an internal port, a valve rod and valve closure member for closing the port between the two chambers, a valve actuator connected to an extension of the rod outside the two chambers, a main gas supply for supplying gas under pressure into the top of the pressurizing chamber, and control means for cyclically energizing and de-energizing the valve actuator and the main gas supply, closing the port and supplying gas to the pressurizing chamber and then opening the port with the main gas supply shut off. A cylinder encompasses the valve rod extension, and a continuous flow of gas is maintained through the cylinder into the transfer chamber. The valve closure member has a conical elastomer surface facing a sharp valve seat at the internal port, affording free flow in a self-cleaning valve.