The stone separator is always standing just before the washer, and is used for separating stones, so the do not enter the washing machine along with the vegetables. It is provided by letting the vegetables pass through a water basin, wherein the vegetables is hit from below by a water beam. The power of this beam is adjusted in such a way that it keeps the vegetables floating, and lets the stones and similar heavier fragments, sinks through the beam and to the elevator.
The elevator brings the stones and fragments to a waste-box, or similar. Another beam makes sure that the direction and speed of the vegetables is steady.