due to their accumulation and sliding on the wind tunnel bottom plate with resultant high sorting accuracy fig4 graphically shows the results of experiments which were conducted by the present inventors for a mixture of crushed pieces of planar plastic and bulky foamed heat insulating material this graph shows the recovery ratio and the mixing ratio of the plastic pieces in the recovered foamed heat insulating material pieces in this figure the black dot and the white dot indicate the recovery ratios of the inventive sorter and the conventional sorter respectively furthermore the black triangular dot and the white triangular dot indicate the mixing ratios of the inventive sorter and the conventional sorter respectively in the wind force sorter of the present invention the ideal sorting with 100 of the recovery ratio and 0 of the mixing ratio can be achieved at the wind speed 4 8 m s shown by the solid line arrow lt a gt on the contrary in the conventional sorter only the sorting with about 80 of recovery ratio can be achieved at a wind speed 5 1 m s shown by the broken line arrow lt b gt furthermore in the conventional sorter when the wind.