Patent GB-574779-A (GB)
Title: Improvements in or relating to the grading of granular materials or substances
IPC: B03B5/38
Filed: 1944-02-17
Abstract: 574,779. Grading granular materials. WILSON, W. A. G., and MONOTYPE CORPORATION, Ltd. Feb. 17, 1944, No. 2942. [Class 82 (ii)] Mixtures of granular materials are graded into groups by spreading a small quantity of the mixture over the surface of a confined and quiescent body of liquid, such as oil, of a predetermined or known specific gravity or viscosity and of such a depth that the particles in gravitating through the liquid are graded into separate groups, each comprising particles of one size, each group being collected in a separate pan or receiver beneath the body of liquid. To assist the grading, a small quantity of benzene or cleansing liquid may be situated above the main body of liquid, and the liquid may be maintained at an approximately even temperature during the grading by placing the apparatus described below in an air-conditioned room or in a chamber furnished with any known temperature-controlling device. In the apparatus shown in Fig. 1, for grading diamond dust, a small quantity of the dust is fed into a layer of cleansing liquid F<1> on the top of the main body F of liquid such as oil, contained in an upright cylinder A, the lower end of which is fitted in a fluid-tight manner into a socket a secured to the cover B<1> of a collecting tank B and passes through an opening b in the cover. The tank B is formed of a cylinder of glass or other transparent material set in a base-plate B<2> which with the tank B and cover B<1> are secured together by bolts and nuts B<3>, the joints being made fluid-tight by washers b<1>. Collecting pans, three in this form, C, C<1>, C<2>, are carried by bases C<3>, C<4>, C<5> supported on arms extending respectively from spindles D, D<1>, D<2> which project through fluid-tight joints B<4>, B<5>, B<6> in the cover B' and are fitted with retaining collars D<3>, D<4>, D<5> and manipulating knobs D<6>, D', D<8>. With oil as the liquid F, which also fills the cylinder B, an operating temperature of 60‹ F. is found suitable. In operation, the pans are moved away from underneath the cylinder A, and a small quantity of the granular mixture fed in at the top of cylinder. The heaviest particles are deposited and then the pan C is moved into position below the cylinder to collect that grade of the material and is then moved aside by turning the knob D<6>, the second pan C<1> being then moved into the collecting position. In a second form, the pans. are all carried at the same level and are supported from separately notched concentric spindles. To facilitate, the removal of a charged pan, a chamber with an open bottom is mounted in the cover of the tank, the lower edges of the wall of the chamber being bevelled to contact with a correspondingly shaped part on the side of the collecting pan which when raised forms a fluid-tight joint with the chamber. The cover of the chamber can then be removed and the pan removed from its base. In a third form, Figs. 7 and 9, the chamber A is mounted on an arm E' pivoted on a port E<8> secured to the base E<9> of a tray E<4> and provided with a handle E<10>, The collecting pans C<1> are placed in separate oil-containing compartments E, E<1>, J, E<2> formed in a plate E3 supported within the tray E<4>. Gaskets E<5> placed in grooves surrounding the chambers E, E<1>, E<2> prevent the leakage of oil and contacting with the gaskets and the upper face of the plate E3 is a plate E<6> secured to the arm E'. To further ensure a fluid-tight joint between the plates E<3>, E<6>, springs E<11> are fitted in sockets in the plate E<9>. In a fourth form, a number of sector-shaped pan receiving chambers are mounted in a movable plate and are moved under one fixed vertical tube A, a shield surrounding the lower end of the tube and adapted to extend over at least two of the chambers and the gearing for moving the plate and thus the chambers successively under the tube. In all forms, the pans may be moved by a clockwork or timing mechanism.