GB1063669A - Filter assembly for sterilizing water - Google Patents

Abstract

<PICT:1063669/C1/1> A portable filter assembly for purifying drinking water comprises a manually operated piston pump 3, 15 and a bacteria removing and purifying filter 21, 22, arranged in a common housing and connected by a passage 5 incorporating a non-return valve 13, the pump connecting by a tube 8 to a source of impure water through another non-return valve 10. The outlet 31 is threaded to receive a canteen for milling when the pump is operated, and tube 8, when not in use, coils round the housing 1, which is of moulded plastic. The filter comprises bacteria-removing filter element 21 enclosing a sorbent 22. Element 21, as shown, is a pleated paper cylinder whose pores are reduced to average less than 0.2 microns by a deposit of particulate material, but sintered, foamed or woven metal, plastics or textiles may be used instead of paper. The particulate material may be any of a comprehensive list of natural or synthetic textiles or plastics, metals, minerals and ion-exchange resins in fibrous and/or granular form, and may also incorporate various slightly soluble silver salts which kill any bacteria deposited on the filter element and remain in non-toxic amount in the effluent water to maintain its sterility. Preferred forms are a mixture of asbestos fibres and 12.5% silver bromide or a mixture of diatomaceous earth and glass fibres, deposited on paper. The element is prepared by depositing the particulate material on to the supporting surface from a liquid dispersion and an intermediate layer of binding agent may be incorporated. The bactericide may be applied separately or together with the particulate material. The sorbent 22 is preferably activated carbon but other materials listed are chabazite, silica gel, chromic oxide gel, lithopone, powdered porous glass, glass wool, activated alumina, quartz crystals and fuller's earth. Clogging of the filter is indicated by opening of a relief valve 28 and discharge of water therethrough, but the vent 45 can be closed by the user so that the pump 3, 15 forces water through a partially blocked filter.