GB1461391A - Analysis of materials - Google Patents

Abstract

1461391 Determining particle sizes in fluids: Weighing ENGLISH CLAYS LOVERING POCHIN & CO Ltd 10 Jan 1974 [11 Jan 1973] 1623/73 Headings GIN G1S and G1W A device for obtaining from a fluid mixture of first and second component materials a quantity thereof which contains a fixed weight of said first component, the density of the second component being known and the mixture containing the two components in unknown proportions, which device comprises container 1, Fig. 3, a float 2, and means such as a mark or a switch S for indicating when the float has reached a fixed height, the relative shape of the container and float being such that when a volume of the fluid mixture containing said fixed weight of the first component has been put into the container, the float, over a range of proportions of said components will float at said fixed height independently of the proportions within said range. The upper portion of the float is shaped according to a disclosed formula and is designed to measure S.G. in the range of 1.040 to 1À200 and at the upper limit of float the bottom of the conically shaped portion of the float is level with the surface of the suspension, and at the lower limit the container 1 is filled to capacity. In use, a suspension is introduced into the container 1 until the float rises and operates the switch S to interrupt the inflow. A fixed weight of solid particles will then be present in the container, and the suspension is allowed to flow from the container into a sieve housing 3 held clamped between two cylinders 4, 5. In Fig. 2 the sieve housing 3 is fixed to bars 27, 28 resting in slots 29, 30 in a bar 32 provided with a C-shaped portion 31. The bar 32 may be rotated to various 90 degrees indexing positions and raised and lowered by motor driven gearing so that in one position the housing 3 is held between the cylinder 4 and a cylinder 5 raised by a screw 9 and in another position it is lowered on to an infrared heater 11 which dries the solid material retained in the sieve. In another position, advanced 180 degrees from the heater, the sieve is lowered gently on to a balance pan 13 and left standing on the pan as the bar 32 is detached from the bars 27, 28. The weight and the related proportion of larger particles is automatically found and the bar 32 then raised again to pick up the housing 3. The sieve and its housing 3 is then advanced through 90 degrees and inverted and emptied by means of a pinion 39 engaging a rack 40. The cycle is completed when the housing 3 is again between the cylinders 4, 5. The float 2 and container 1 may be sprayed by water jets (not shown) to remove residue from the container and washing water may be supplied through a rose 10, Fig. 2. A programme controller (not shown) enables automatic operation to be carried out if desired. Weighing In Fig. 3, the balance pan 13 and its supporting arm 15 are carried on a beam 16 counterbalanced by a weight 17. Balance is detected by capacitor plates 18, 19 changes in current which is directly proportional to the weight of material on the sieve being detected by a transducer and passed through a moving coil of a motor 21, in which the coil moves in a constant magnetic field, the motor returning the beam to a balanced position. A second winding on the coil is used for fine zero adjustment and is fed from a stabilized variable current source. The balancing current is passed through a resistor and a digital voltmeter is connected across the resistor to indicate the percentage by weight of solid particulate material. A memory device e.g. a servomotor driven potentiometer can be used to retain the measured quantity. In the balance of Fig. 6, the arm 84 having a counterbalance weight located inside a casing 87 and provided with capacitor plate 90 pivots about an agate knife edge 85 resting on an agate plane 86 but may be lifted off these edges to an inoperative position, where it rests on three pins 102, by rotation of a motor 99 and cam 98 controlled by micro-switches 109, 110, the cam acting on a rod 100 fixed to a pivoted member 101. The suspending arm 81 is supported by two pins 105 which rest on an agate block 106 and a conical agate block (not shown) to give precise location. The balance pan 80 carries at its upper end an agate plane 82 co-operating with an agate knife edge 83 fixed to the beam 84. Pendulum motion of the balance pan is damped out by an aluminium vane 111 fixed to the pan and hanging in the gap between two U-shaped permanent magnets (not shown) with poles of opposite polarity at adjacent faces. A sensitivity adjusting weight 94 and a rough balance adjusting weight 96 are provided.