The invention relates to a sieve jigger for sorting solid material mixtures, such as raw coal or other minerals, in a separating liquid, such as water, according to density, in particular for the pre-separation of tailings, comprising a rocker that can pivot in the water bath and carries the sieved-product carrier and the sieved-product, which rocker executes an upward stroke by way of a pivotedly connected hydraulic cylinder and a downward stroke by letting it fall under the force of gravity.
From the leaflet 4-230d of KHD Humboldt Wedag AG of June 1989 the so-called ROMJIG sieve jigger is known for the pre-separation of tailings from raw coal. The jigging takes place in a water bath. The loosening of the material required for the sorting according to density is produced by the lifting or pivoting upward and dropping down of a rocker which is pivotally mounted in the water bath and carries the sieved-product carrier and the product. The lower specific density coal and the higher specific density tailings are separately discharged from the jigging machine by a lifting wheel.
With the known sieve jigger, the upward pivoting movement, i.e., the upward stroke of the sieved-product rocker, takes place by hydraulic oil flowing into a single-acting hydraulic cylinder which engages the rocker. On reaching a lifting height of, for example, 300 to 400 mm, the rocker is allowed to drop and moves downwards again as a result of gravity and its own mass (including the sieved-product) of, for example, 4000 to 5000 kg. In doing so the loaded rocker at the end of its downward movement falls onto at least two hydraulic vibration dampers, which are able to transmit the forces released during the falling down of the rocker in an as jolt-free manner as possible. It was found that with this type of rocker drive the lifting frequency of the rocker is limited to approximately 40 strokes per minute. In addition, the vibration dampers are subject to wear and an undesirable heat generation.