Screen device for pneumatic transport equipment

Claim 1

A screen device for fine-grain materials, especially flour, to be used in pneumatic transport equipment comprising: a source of pneumatic pressure; a transfer pipe connected to said source of pneumatic pressure; means connected to said transfer pipe for feeding said material into said transfer pipe in order to transport said material along the pipe entrained in a flow of air from said source; a screen connected to said transfer pipe downstream of said feeding means, and arranged transversely to the transfer pipe; and stationary means connected to a source of compressed air and defining an array of small apertures, which array extends completely around the interior of a portion of the transfer pipe located immediately upstream of the screen to form a multiplicity of sMall, closely spaced air streams in order to mix effectively substantially all of said fine-grain material moving towards said screen with the air of said streams thereby to fluidize the fine-grain material, the pressure of the air of the streams being substantially the same as the transport pressure of said flow of air.