Variable flow rate hopper to reduce feed pulsation to a downstream process

DETAILED DESCRIPTION The main objective of the present invention is to provide apparatus that converts a fluctuating incoming stream of particulate material into a uniformly flowing output stream.
The steady output stream is more efficiently utilized by downstream processing equipment.
In accordance with the present invention, the apparatus includes a hopper that is interposed between a feeder and the downstream processing equipment so that surges in the feed rate are accumulated in the hopper and lapses in the feed rate are compensated by the propensity of the hopper to discharge at a constant rate.
Initially, the hopper is empty, and the incoming particles merely cascade through the apparatus.
One of the problems overcome by the present inventor was how to get the hopper full enough initially so that hopper-type flow would continue.
In accordance with the present invention, the discharge opening of the hopper is initially blocked by a trap door that is preloaded into a closed position against the discharge outlet of the hopper.
The trap door does not open until sufficient particulate material has accumulated in the hopper, at which point the weight of the particulate material overcomes the preloading force, thereby releasing the trap door and permitting hopper-type flow from the discharge opening.
In a preferred embodiment, a magnet is used to supply the preloading force.
The magnetic force is effective only over a short distance, and therefore it was also necessary to solve the problem of how to close or reset the trap door after the flow from the hopper has ceased.
In the preferred embodiment, this is reliably accomplished by a counterweight, which also urges the trap door to its closed position.
The discharge rate of a hopper is determined by the slope of the walls of the hopper and the size of the outlet of the hopper, and therefore remains approximately constant regardless of how much material is in the hopper, and regardless of variations in the input stream.
Thus, an existing hopper will have a fixed discharge rate for the material with which it is used