A Method of and Apparatus for Testing a Powdered Material to Determine the Fineness Thereof.

摘要

1,176,678. Electro-physical measurement - particle size. FULLER CO. Nov. 28, 1967 [Nov. 30, 1966], No. 54163/67. Heading G1N. The fineness of particles is determined by measuring the fluid permeability of a sample, compacted to a known porosity or density, determining the length of the sample in the direction of measurement of the fluid permeability and multiplying the one by the other to obtain a valve of the fineness of the particles. As shown, the sample is introduced into a tube 16, Fig.1, via inlet 14 while the tube and inlet are vibrated by devices 56 to obtain an initial even density of the sample, the tube being filled to the level of overflow outlets 28. After filling a piston 30 is moved downwards under the action of a cam 44 driven by the shaft 45 of a motor 46, to compress the sample. Measurement of porosity. During compression the density of the sample is continuously monitored, by measuring the capacitance of electrodes 62, one connected to an oscillator 66, Fig. 2, the other via an amplifier 70 to a comparator 68 where the signal on one electrode 62 is compared with that on the other. When the inputs from the oscillator and amplifier are equal, a relay 72 is energized to deenergize the compression motor 46. The set valve of porosity is determined by adjustment of capacitor 74 connecting the oscillator to the amplifier. Alternatively the porosity of the sample may be determined by measuring the absorption of electromagnetic or particle radiation which occurs across the sample. Measurement of fluid permeability. The fluid permeability is determined by connecting constant fluid-pressure differential between porous plates 18, 32 at the lower end of tube 12 and the lower surface of piston 30 respectively and measuring the rate of flow of fluid through the sample using flowmeter 76 which produces a representative voltage at outputs 86, 88. Alternatively the fluid permeability may be measured by applying initially a known pressure difference across the sample and measuring the time for it to be reduced to a predetermined value or by applying setting up constant flow rate of fluid through the sample and measuring the pressure difference across it. Determination of fineness. The voltage output from the fluid-flowmeter 76 is connected across a potentiometer 96 geared to the motor 46 to move according to the position of the piston 30 and therefore according to the length of the sample. The voltage between the slider and one end of the potentiometer is representative of the fluid permeability of the sample, i.e. the fineness of the sample corrected according to the length of the sample.