Patent GB-467532-A (GB)
Title: Improvements relating to alluvial mining dredges
IPC: E02F7/06
Filed: 1936-05-14
Abstract: 467,532. Washing dredged material. HUTTON, G. H., and BLANCHARD, F. M. May 14, 1936, No. 13608. [Class 82 (ii)] [Also in Group XXXIII] A dredger comprising a pontoon and a ladder supporting digging and elevating means and pivotally mounted adjacent one of its ends on the pontoon with means for raising and lowering its other end is provided with a washing plant comprising a rotary inclined screening drum into which the elevated material is fed, a sump for screened fines below the drum, washing devices such as jigs or tables above the level of the sump, and at least one bucket elevator for raising the fines from the sump to the jigs &c. The buckets of the elevator or elevators are preferably perforated so that the fines are dewatered, clean water being supplied to the washing devices. Means may be provided for separating clay from the screened fines, the clay being then disintegrated and returned to the washing plant. In the.form shown in Fig. 1, material raised by buckets 30 on the ladder 31 passes by way of a shoot 35 to a rotary screening drum 1, the centre part of which may be imperforate, in which it is washed by high pressure jets of water. The drum is mounted in a casing 2 which tapers downwardly and in which are provided perforated plates 4 which divide the bottom of the casing into two outer portions 5 for the fines and a central portion 6 for clay. The portions 5 lead to sumps 11, the bottoms of which extend outwardly, Fig. 3, to the sides of the pontoon, forming settling boxes 13 the outer ends of which are closed by preferably adjustable gates 14. Clay is removed from the portion 6 by a pump 8 which disintegrates it and returns it to the drum 1. The fines collecting in the sumps 11 are raised by bucket elevators, which preferably have perforated buckets, to a rotary distributer 17 which feeds them to troughs 18 leading to jigs 19. The concentrates from the jigs 19 are passed by pumps to cleaning jigs 26, the tailings from the jigs 19 and 26 being discharged into sluices 25. Fresh water withdrawn through filters from the surface of the pond by pumps is fed to the distributers 17 and the material which does not pass through the screen drum 1 passes on to a stacker belt 29. In a modification, the clay separated from the fines is passed through puddling devices such as log washers and then mixed with the fines in the sumps 11, and a gate is provided in a shoot at the end of the drum 1 by means of which large size material passing along the drum may if desired be passed to the log washers by way of a grid on to which are directed high pressure water jets, material rejected by the grid being discharged over the rear of the pontoon by a shoot. A second gate is provided in the shoot at the end of the drum by which the material can be sent direct to a rock shoot instead of to the stacker belt. In another form, Fig. 7, in which no means for separating clay is provided, the stacker belt 29 extends under the whole length of the drum 1 and an adjustable shoot 52 is provided by means of which the dredged material mav be directed either into the drum 1 or, when overburden is being dredged, direct to the stacker belt. The stacker belt is mounted on inclined rollers so that it is concave and is disposed within a shoot 49 which extends over the end of the pontoon.