Patent GB-443112-A (GB)
Title: Improvements in filters
Filed: 1934-08-20
Abstract: 443,112. Filters. FILTRATION & WATER SOFTENING PROPRIETARY, Ltd., 395, Collins Street, Melbourne, Australia. Aug. 20, 1934, No. 23995. Convention date, Aug. 18, 1933. [Class 46] The space above the normal surface of a sand or like filter is restricted or formed with passages so that when the bed iswashec with an upward flow of water at a rate sufficient to cause an ex pansion of the bed, the velocity of the wash water is increased in the restricted zone and causes a secondary expansion of the bed at a section of the zone where the velocity is uniform. There may be a further restriction above the zone to facilitate the discharge of impurities. Fig. 1 shows a filter casing 10 with a restriction 31 into which the bed is expanded by the upward flow of wash water and a further restriction 15 to which the wash water outlet 11 is connected. The expansion of the bed may be controlled by a valve 18 on the wash water inlet operated manually or by a float 19 responsive to the sand level. As shown in Fig. 4 the upper restriction is provided by means of a vertically adjustable displacement member 30. Fig. 2 shows a filter in which passags 31, 15, are formed in a diaphragm 25 supported on a screwed rod 26 so that it can be adjusted vertically by an electric motor 48. This motor and another for operating the valve on the waste water inlet are driven in either direction in accordance with the position of a contact piece 22 supported from a float 19. Alternatively the valve may be controlled from a photo-electric cell responsive to the comparative opacity of the upper portion of the expanded filter bed. A diaphragm 25 may be itself arranged as a float. Fig. 5 shows apparatus with a partition 33 having a number of passages 31, 15 therethrough. As shown on the left of the Figure the passages 15 extend above the partition and the space above the partition serves during filtration as a settling chamber for matter in the water to be filtered. As shown in Fig. 7 a filter casing 10 is closed by a concrete slab 36 having a recess 37 with wash water outlet 11. Passages 31 are formed by members 41 with perforations 42 near the top of their walls. Fig. 9 shows a filter having a diaphragm 43 with passages of double-cone shape, the diaphragm being arranged at a level above the top of the bed formed when the sand is settled down during filtration but below the level to which the sand expands when lifted by the reverse flow of wash water. In all forms the passages 15, 31 may be provided with projections, preferably in the form of helical vanes, to give a rotary movement to water passing therethrough. It is stated that the level to which the sand bed expands during washing may be controlled by a thermostat responsive to the temperature of the water. Specification 28197 /97, [Class 46] is referred to. The Specification as open to inspection under Sect. 91 describes filters with tapering restrictions just above the level to which the sand rises during the washing of the bed. Fig. 17 (Cancelled) shows a filter with a restriction formed by a central displacement member 46 supported on arms 47. This subjectmatter does not appear in the Specification as accepted.