Abstract: A substantially continuous flow is attained in the unloading of a bulk particulate from a storage hopper by monitoring the pressure differential between the hopper and a point in the discharge line downstream of the hopper outlet. The pressure differential is sensed by a pressure switch in the discharge line which activates a vibrator on the hopper near the outlet when the differential is at a first predetermined value and deactivates the vibrator when the differential is at a second predetermined value, thereby maintaining the flow and reducing mechanical damage to the hopper.

Abstract: A bottom assembly for a hopper vehicle is adapted to permit safe pneumatic unloading as well as gravity unloading of a hopper. The bottom assembly includes a membrane mounted to be moved over and away from a hopper bottom opening, and sealing devices for insuring a secure seal for the hopper which can be easily set. A discharge manifold is connected to the hopper at a location spaced from the hopper bottom opening, and the hopper bottom opening is contained in a plane which is tilted with respect to the horizontal.