378,014. Emery and sand cloth ; wheels. TENNANT, W. J., 111, Hatton Garden, London.-(Bohr-Manning Corporation ; Troy, New York, U.S.A.) March 28, 1931, No. 9486. [Class 60.] In the manufacture of abrasive coated paper, grinding discs, &c., the grains of abrasive, as they fall on to the adhesive coated sheet of paper &c., pass through an electric field whereby they are separated, and also turned so that the sharpest points of the grains are outwardly directed when on the sheet ; by controlling the electric field the density of the abrasive on the sheet may be varied. The paper &c. sheet 10, coated with adhesive, is fed over a roller 12 supported in the machine frame 131, and receives the abrasive from a hopper 13 the lower end of which is partially closed by a roller 14. The wall of the hopper terminates at 15 and the size of the outlet for the abrasive is controlled by a gate 16 moved, through rack gearing, by a lever 20, and by a second gate 22 adjusted by bolts 24. The abrasive, as it falls, passes through an electrostatic field produced between the roller 12, which is earthed and a tube 35 supported by insulators and connected to a source of high potential ; the ends of the tube may be rounded to avoid " end effect," or strips of metal may be secured at an angle to the ends of the tube for this purpose. Excess of abrasive is allowed to fall from the hopper, the surplus being diverted by a baffle 51 into a hopper 53 ; the baffle is adjustable by slots 54 and bolts 55 and by screws 60. A modified form of electrode comprises a small diameter inner tube surrounded by a tube of larger diameter, and the distribution and intensity of the field may be varied by the use of various diameters of tube, by rotation of the tube, or by the use of wires instead of a tube. Specification 378,057 is referred to.
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