GB931088A - Improvements in or relating to classifiers - Google Patents

Abstract

931,088. Sifting or screening apparatus. F. K. MOGENSEN. July 21, 1961 [July 25, 1960], No. 26600/61. Class 117. A screen classifier of the " sizer " type, i.e. the type where the mesh size of a screen is larger than the grain-size of the particles fed to said screen, comprises a group of screens arranged one above the other and each sloping downwardly in its forward direction from the feeding end of the classifier, particularly in which at least one screen slopes more steeply than the screen nearest above, characterized in that an impervious body is spaced vertically below the uppermost portion of at least one screen and is arranged to collect particles which have passed through said portion and feed them to the feeding end of the screen next below said screen. The " sizer as shown comprises impervious plates 22a to 22e secured to side plates 11 underneath such as screens 35a to 35c. The screens such as 35a to 35c are supported by front bars 31, intermediate bars 32 and stretching bars 33 having tension adjusting bolts 34 movable in sleeves 24 and are stretched between nose ribs 36, 37 on bars 31, 33. A vibrator 41 is provided and the sizer is suspended from springs 39. All the screens have the same mesh size. In operation, particles of different sizes are fed to screens via feeder plate 21. The smaller particles will pass directly through the screens while the coarser particles will impinge against the screens more frequently. and be reflected to pass through a lower level on the same screen so providing a separation according to size. It is stated that due to the inclination and the small distance between the screens at their uppermost portions, coarse particles falling on a screen from a higher screen tend to rebound in a rearward direction and pass through a mesh opening in the upper area of the screen so that after passing through the " sizer " the finest particles will be polluted with coarse particles. The impervious plate is said to prevent this by throwing all particles falling on it to lower areas of the screen below it. Specification 670,017 and U.S.A. Specification 2,853,191 are referred to.