IE36321B1 - Improvements in or relating to liquid straining apparatus - Google Patents

Abstract

1357902 Liquid straining apparatus GLENFIELD & KENNEDY Ltd 21 April 1972 [22 April 1971] 10773/71 Heading B1D [Also in Division G3] A filter apparatus comprising a continuously moving screen, e.g. in the form of a rotary drum, disc or a moving band, includes means for cleaning the screen, driving means to move the screen so that each portion of the screen is first brought into a liquid filtering position and then into a cleaning position, and manometer means which is coupled to the driving means to control the rate of movement of the screen in response to the -difference in hydrostatic head across the screen. Fig. 1 shows a rotary drum 1 driven by motor-3 the periphery of which is formed of screens, cleaning means 2 and a pair of capacitance electrodes 4 and 5 forming the manometer means, these electrodes being situated either side of a wall 7 separating liquid to be strained from liquid already strained. The electrodes which dip into the liquid are connected to a comparator 8 (Fig. 2) which generates a difference signal which depends on the pressure difference between the electrodes. This difference signal is passed to a process controller 9 which compares the difference signal with a control signal which it itself produces and which corresponds with the desired pressure difference across the screen, The controller then generates an output signal dependant on the difference between the control signal and difference signal and this is fed to servo-motor 10 controlling the operation of variable speed motor 3. A feed-back connection is provided from the motor 3 to the servo-motor 10 to stop the servo-motor when the speed of the straining screen attains a value maintaining the required pressure difference. A remote control unit 11 containing an amplifier 12 conected to the output of comparator 8 provides a difference head indicator 13 and an audible alarm unit 14. [GB1357902A]