GB1319611A - Apparatus for the separation grading and sampling of a granular or pulverulent material - Google Patents

Abstract

1319611 Wet screening apparatus NATIONAL RESEARCH DEVELOPMENT CORP 26 April 1971 [24 April 1970] 19737/70 Heading B2H [Also in Division B8] An apparatus for separating grading and sampling granular or pulverulent material comprises a plurality of superposed members 10-13 for grading the coarser fraction of the material and simultaneously separating the finer fraction therefrom, means, e.g. 17, for vibrating the superposed members, means 29 for dividing the finer fraction of the material into a plurality of samples, a distributor 25 for supplying the finer fraction to the dividing means 29, and means 30, 31 for effecting relative movement between the distributor 25 and the dividing means 29. The apparatus is used for separating the coarse aggregate fraction of unhardened concrete from the fine sand, silt and cement fraction, grading the coarse fraction and dividing the fine fraction into a number of samples. Sieves 10-13 of progressively decreasing mesh size downwards are mounted above a collector funnel 15 on a sub-frame 14 which is agitated by vibrators such as 17 and is supported by dampers 20 on a main frame 19. Liquid is sprayed on to the sieves through piping 21, 22 equipped with flow-control valves 23. The funnel 15 communicates via a valved outlet with the distributor 25 which includes a rotatable funnel 26 provided at its lower end with curved distributor pipes 27 and driven by a shaft 31 coupled to an electric motor 30. Liquid is supplied to the upper end of the funnel 26 through a valved pipe 34. The dividing means 29 comprises a flat plate 36 having apertures 37 in communication with associated pockets 38 having outlets 42 to which tubing may be connected for discharging samples to receivers 43 for subsequent analysis. The dividing wall 39 between adjacent apertures 37 is formed as a knife edge 40 to provide a positive cut-off as the flattened ends 28 of the distributor pipes 27 pass over the dividing walls 39. Concentric splash guards are provided at 41. In use, the valve at the outlet of the collector funnel 15 is first closed, the funnel 26 is rotated and a constant head of liquid is maintained in the latter by adjustment of the valve 35 on pipe 34. A sample of unhardened concrete is discharged in the top sieve 10 and the sub-frame 14 is vibrated. At the same time the flow of liquid to the funnel 26 is reduced by progressive closure of valve 35 and flow of liquid to the top sieve 10 is commenced by progressively opening the valve 23 on its associated piping 22, 21, whilst the valve at the outlet of funnel 15 is progressively opened. When liquid flowing from funnel 15 is clear, the valve 23 associated with sieve 10 is closed and the valve 23 associated with sieve 11 opened, this sequence being repeated for the sieves 12, 13. When the liquid which has been sprayed on to the lowermost sieve 13 flows clear, the valve 23 associated therewith is closed and the valve 23 associated with sieve 11 opened, this sequence being repeated for the sieves 12, 13. When the liquid which has been sprayed on to the lowermost sieve 13 flows clear, the valve 23 associated therewith is closed and the valve 23 associated with the sieve 10 is opened to flush through the sieve assembly. Thus, the fine sand, silt and cement fraction is passed through the smallest mesh sieve 13 into the funnel 15 and delivered as a slurry to the funnel 26 and to the rotating distributor pipes 27 which in turn deliver equal sampling volumes of slurry to the apertures 37 and associated pockets 38. A stream of hot air may be blown by a blower 45 and conduit 44 through or across each sieve to dry the coarse aggregate fractions retained thereon.