Patent GB-786570-A (GB)
Title: Improved filter for liquids
IPC: C12H1/07
Filed: 1955-01-26
Abstract: 786,570. Filters for liquids. PATERSON ENGINEERING CO., Ltd., and BAILY, E. W. Jan. 13, 1956 [Jan. 26, 1955], No. 2310/55. Class 46. A filter for liquids comprises one or more hollow main filter elements mounted, in an inlet chamber and connected at one end to a main outlet chamber, one or more auxiliary filter elements mounted in the inlet chamber below the level of the main elements and connected at one end to an auxiliary outlet chamber by an imperforate tube having its lower end within and close to the closed end of the auxiliary element, and valves on each outlet chamber permitting either the main or auxiliary elements to be used selectively and to enable the contents of the inlet chamber to be displaced by compressed air and to be discharged through the auxiliary elements leaving only a negligible residue of unfiltered liquid. A diaphragm 12 dividing a casing into lower and upper parts 13, 14, supports a parallel arrangement of tubular filter elements 11, some, 11a, of which have extensions 21 from which axial tubes 20 extend upwards through the chamber 14 and an upper diaphragm 24 into a chamber 27 ; the interiors of the elements 11 open into the chamber 14. To commence the filtering operation, liquid entering through a valve 31 is charged with diatomaceous earth which settles on the exterior of the filter elements 11, 11a, to provide a filter medium, filtrate passing mainly up the centres of the elements 11, 11a into the chamber 14 and out through a valve 35, sight glass 37 and master valve 38 leading to a reservoir for filtered liquid, a small part traversing the extensions 21, tubes 20, chamber 27, outlet pipe 34 and valve 36 to the sight glass 37. A cushion of air is trapped at the top of each chamber. When the filter elements 11, 11a become clogged, the valve 35 is closed slightly to increase the pressure in the chamber 14 and compress its air cushion ; an air valve 39 in the chamber is then opened and the valve 35 closed, the compressed air forcing the filtrate in the chamber downwards through the main elements into the chamber 13 which is itself emptied by pressure air introduced through a valve 40, the discharge being through the extensions 21, tubes 20 and chamber 27. When the discharge is completed, the valve 36 and the air valves 39, 40 are closed, the remaining liquid being drained off through a valve 41. To clean the filter, the master valve 38 is changed over from the reservoir to waste, the valves 36, 38 and 31 are opened: the chambers fill with water under pressure and the air cushions are compressed. Thereupon an air relief valve 43 at the top of the chamber 13 is opened suddenly and the air cushions in the chambers 14, 27 " air bump " the water in the elements 11, 11a, 21 to clean them. The main elements 11 may be made up of sections secured together by a hollow tie rod which constitutes the tube 20. The elements shown consist of a tubular former covered with a wire winding, wire mesh, cloth or other septum but elements of porous stone or plastics or of sintered metal, may be used. Specifications 595,891 and 619,973 are referred to.