Patent GB-1119248-A (GB)
Title: Improvements relating to liquid filters
IPC: B03C1/03
Filed: 1964-10-02
Abstract: 1,119,248. Magnetic separators. AUTO-KLEAN STRAINERS Ltd. 12 Nov., 1965 [20 Oct., 1964; 10 June, 1965; 6 July, 1965], Nos. 40256/64, 24616/65 and 28595/65. Heading B2J. A liquid filter comprises a casing 1 having a liquid inlet 7, a liquid outlet 8 and a flushing outlet 39 and incorporating a number of filter stations 27 in each of which is located a removable magentisable filter element 28, an inlet part of each station being in permanent communication with the liquid inlet 7 and an outlet part of each station selectively communicating with the liquid outlet 8 and the flushing outlet 39, means being provided for magnetising and demagnetising each filter element 28. As shown, sets of concentrically arranged diametrically opposite apertures 14 15, are provided in a plate 11 clamped between the parts 2, 2a of the casing and locate the filter stations 27. Each station comprises a tube 29, Fig. 2, of moulded plastics forcefitted in a mild steel tube 31 and having embedded therein a solenoid 30. Each of the filter elements is of the cage type and is supported within the tube 29 by a spider 32 resting on the upper ends of the tubes 29, 31. The solenoid is connected by leads to a rotary contactor 34. A screen 35 provided above the filter stations 27 is formed with apertures at each of the stations and ensures that solids to be separated from the liquid do not settle on the plate 11 but are directed to the filter stations. The flushing outlet 39 is at the end of a conduit 38 coupled via a rotary joint to a rotatable tube 26 which is provided at its ends with spring-loaded collars 41 adapted to successively seal against the lower surfaces of the tubes 29 in the outer and inner concentric sets of filter stations. The tube 26 is mounted on a shaft 20 driven by a motor 43 via gearing and coupled shafts 23, 44. The motor 43 also drives the contactor 34 and a cam 45. The latter operates a micro-switch 46 which initiates operation of a cycle controller 47 controlling the operation of a magnetising/demagnetising unit 48 and a remote-controlled flushing valve 49. In operation, liquid to be filtered enters at 7 and passes through the interior of those tubes 29 which are in communication with the Chamber 13, i.e. those corresponding to the filter stations 27 not shown in section in the figure, the solids being retained on the filter elements 28 and the filtered liquid flowing towards the outlet 8. In the position of the tube 26 shown in the figure, switch 46 has been operated to initiate the cycle controller 47 to provide a de-magnetising pulse through the rotary contactor 34 to the solenoids of those filter stations shown in section in the figure. At the same time the valve 49 is opened so that liquid passing through the sectioned filter stations washes the previously trapped magnetisable particles from the filter elements 28 into the tube 26 and out through the outlet 39. After a predetermined interval, the cycle controller operates bo shut valve 49, energise the solenoids and start the motor 43 to move tube 26 to the next pair of diametrically opposite filter stations, and the above operation is repeated. When cleaning is required at infrequent intervals, the motor 43 and hence the tube 26 can be arranged to run continuously at slow speed. Alternatively, the tube 26 can be arranged to be "parked" between filter stations and the cycle initiated as and when required. Initiation of the cycle may be by means of a differential pressure switch connected between the chambers 12 and 13 and measuring pressure differences resulting from partly choked filter elements. Instead of each set of filter stations having the same number of stations, the outer set may have twice the number of stations present in the inner set. In a modification, Fig. 3, only a single set of filter station,s are provided, each comprising a magnetisable cage 101 mounted within a non-magnetic sleeve 102 and extending between perforated pole pieces 103, 104 joined to limbs 105, 106 of an electromagnet or of a permanent magnet. In a further modification, Fig. 5, a tube 203 of nioni-magnetisable material having a closed lower end extends from outside the casing 1 through the magnetisable cage 201 at each filter station. A permanent magnet 205, 206, 207 connected by a rod 208 to a fluidoperated motor 209 is slidable in the tube 203 so that in operation the pole pieces 206, 207 are brought into register with the end plates 210, 211 of the cage 201. In this position the tube 26 would not (as shown for convenience in the drawing) be in communication with the interior of the filter station; this would occur when the permanent magnet is drawn out of the cage 201 by energisation of motor 209 to demagnetise 'the cage whence flushing liquid will pass therethrough into tube 26.