| 摘要 |
<p>In the grading unit fine fraction of sand is freed from impinging impurities and graded sand can be discharged at several points of the unit. The water sand mixt. is fed into the rotating drum (1) through inlet tube (2) which has an increasing dia. in direction of the water flow. By this arrangement the flow velocity of the water is gradually decreased, so that by the time the water reaches the end of the tube its velocity is very low and it trickles evenly distributed into the water level already present inside the drum through the perforated part (5) of the tube. As the water and sand slides gently into the water content of the drum, the spiral channels formed by the numerous guide blades (7) enable the sand to settle in these channels. By the rotation of the drum the sand is steadily shifted towards the other end of the drum, where it comes within operating range of the two sets of rotating wings (8, 8) which scoop up sand particles on their surfaces while the water drops back into the drum. As the wings rotate sand deposited on any wing reaching its top dead centre drops its deposit onto the conical discharge surface (10, 10) from where it is disposed of via chute (17).</p> |
