Feed pipe for conveying sticky bulk material

A straight, stationary feedpipe mounted vertically between a bunker outlet and an enclosed, pressurized conveyor system for feeding from a bunker to the pressurized conveyor system bulk material of the type having a tendency to arch and for forming a pressure seal for the enclosed pressurized conveyor system, said feedpipe consisting of a plurality of serially connected, downwardly tapering tubular members of substantially identical design, rigidly connected together with the lower edge of each downwardly tapering tubular member laterally spaced around its entire periphery from the upper end of the adjacent lower tubular member by annular means extending completely around and filling the gap between adjacent tapered tubular members to form a portion of the interior surface of said feedpipe which extends outward and faces downward to the extent that sticky bulk material can not cling to this surface in forming an arch, and wherein each of said tubular members has a ratio of its axial length to its average diameter which is smaller than that required for arching of the bulk material within that tubular member such that the feedpipe can be continuously filled with the bulk material to a level which seals the pressurized conveyor system, yet the bulk material remains free-flowing for feeding the conveyor system.