| 摘要 |
<p>According to the invention, there are provided: - downstream of the filter tank (1), a double-acting adjustable-flow controlled valve (6) capable of creating a variable pressure drop in the filtered water exit conduit of the tank, - at the surface of the volume of water in the tank, a detector sensor (E1) comprising an electrode sensitive to the presence or absence of liquid at a predetermined set level, producing a signal representative of the water level in the tank, and - means (8, 100) of incremental control of the valve, operating in response to the signal produced by the sensor, capable of opening the valve by successive pulses until the emergence of the initially immersed electrode is obtained, or of closing it again by successive pulses until the immersion of the initially emerged electrode is obtained, so as to vary the pressure drop created by the valve downstream of the tank in the opposite direction to the variation in pressure drop of the filter bed accompanying a variation in the water level in the tank. As a result, the rate of filtration of the water delivered to the tank remains substantially constant. <IMAGE></p> |
