GB1273976A - Improvements in or relating to filtration - Google Patents

Abstract

1,273,976. Edge filter; magnetic filter. R. J. STEVENS. 9 May, 1969 [11 May, 1968; 15 May, 1968; 22 May, 1968; 9 July, 1968; 17 July, 1968], Nos. 22476/68; 23103/68; 24332/68; 32600/68 and 33926/68. Headings BID, BIT and B2J. An edge filter comprises a stack of plates having various apertures therein, plates 3 having deflectable portions 14 (Fig. 14) which coact with portions 13 of plates 5 to define filtering gaps. During forward flow from passages 8 to passages 9, the fluid pressure tends to close the gap, portion 14 engaging the sides of an opening through plate 4, whose thickness defines the gap width, but during reverse flow cleaning the portion 14 is able to move into the wider opening in plate 2, widening the gap as shown on the left of Fig. 14 to release solids. In Figs. 1 to 14, portions 14 are formed as flaps, which are deflected by virtue of the flexibility of the plate material or by virtue of a line of perforations therein forming a hinge. Only the free edges of flaps 14 define the filtering gaps in Fig. 14, but Figs. 15 to 17 (not shown) illustrate similar stacks wherein plates 5 and the flaps of plates 3 are slotted in a staggered fashion to increase the effective lengths of the gaps. Plates 3, 5 could be spaced by extensions thereof rather than by separate plates 4. In Fig. 18 there are effectively two gaps in series, one between plates (3" and 3') the other between plates (3' and 5'). In Figs. 19, 20 parts of one plate (15) are supported at one end only by extensions (17) of plate (16), so that filtering gaps tapering from zero to an intermediate width are defined through which fluid flows from slots (22) to slots (21), while wider gaps are formed upstream through which fluid enters slots (22) and thus there is depth filtering. Figs. 21 to 24 (not shown) represent a filtrate outlet chamber presenting a square-sectioned outside, on whose respective faces are mounted filter stacks as in Fig. 14. The chamber is built up of sections and defines a cylindrical interior wherein rotates a helical channel, also built of sections, which delivers backwashing fluid to each outlet, leading to a passage 9, in turn. Fig. 25 represents an alternative plate whose central portion, slotted to extend the length of the filtering gap, is movable relative to its perimeter and relative to the coacting plate, by bending portions 33. Plates may be plastics or metal (exemplified) may be roughened and may be permanently magnetised. Fig. 28 shows a plate stack mounted between steel plates 39 in a magnetic field induced by electromagnetic coil 37. Liquid or gas may be filtered and backwashing may use liquid followed by gas and may be pulsed. The plate portions may be deflected directly by the backwash fluid or by pneumatic/hydraulic pressure applied through separate passages in the stack to the roots of flaps 14. In Fig. 28 plates may be shaken by alternating current in the coil.