Patent GB-1139581-A (GB)
Title: Magnetic filter
IPC: B01D35/147
Filed: 1966-01-13
Abstract: 1,139,581. Magnetic filters; oil filters. MARVEL ENG. CO. 13 Jan., 1966 [13 Jan., 1965], No. 1744/66. Headings B1D and B2J. A magnetic fluid-filter or filter cartridge comprises an arrangement of parallel permanent, pencil-like, bar magets forming a magnetic-field screen across the fluid flowpath upstream of a fluid-pervious mechanical filter screen so as to attract magnetic contaminant particles in the fluid and cause them to adhere to the magnets prior to passing of the fluid through the mechanical filter screen. The fluid may be oil contaminated with metallic, e.g. ferrous particles. As shown in Figs. 1 and 3, a filter cartridge has a hollow, perforated steel core 6 extending between end caps 2, 5 and having its interior in communication with a bore 3a of a connection 3 for the filtered fluid. A corrugated filter screen 7 of non-magnetisable fine mesh material surrounds the core 6 and is retained in the caps 2, 5 by bonding material M. Removable, elongated, cylindrical permanent magnet assemblies 8 are located in troughs 7a formed in the screen 7 and are held through magnetic attraction with the core 6 through the interstices or open spaces in the mesh of the screen 7. Alternatively, the core 6 may be corrugated and arranged in laminated relationship with the screen 7. In another modification, Fig. 2 (not shown), the magnet assemblies 8 instead of extending within the end caps 2, 5 are of shorter axial length and may be retained against accidental displacement by a spring clamping band (55), a wire coil or individual clips. Each magnet assembly 8 consists of a thin, pencil-like tube 20, Fig. 4, of magnetically-permeable material, e.g. aluminium, enclosing a number of permanent magnets 21 positioned with like poles in contact with each other and retained against the repellant magnetic effect by the ends of the tube 20 being pinched or plugged. As shown, the like contacting poles in one tube of an assembly are of opposite polarity to those of the adjacent tube of the other assembly. Such an arrangement provides a strong enough magnetic field to completely envelope the entire filtering surface. Alternatively, the intermediate magnets in each tube 20 are spaced apart by a narrow gap. In another embodiment, Fig.5 (not shown), a filter screen (36) is surrounded by a wide mesh screen (35) of expanded metal. The magnet assemblies (8) are held against the sleeve (35) by magnetic attraction and are positioned either in an external recess (35a), Fig. 6 (not shown), or an internal recess (35b), Fig. 7 (not shown), formed in the sleeve (35). In a further embodiment, Fig. 9, a filter cartridge 46 is centrally located within a housing 40 of a magnetic filter by means of a sleeve 44 and centering ribs 45 and has the magnet assemblies 8 positioned in corrugations formed in a sleeve 51 made of mesh or perforated material serving as an additional filter screen for the fluid which enters the diaphragm inlet 43 and leaves through a central outlet 42. A spring-loaded valve seat 48c is provided in an aperture 48b at the top. of the cartridge 46 and a spring-loaded valve member 48d rests against the seat 48c during normal operation of the filter. When a predetermined pressure is reached outside the cartridge 46 corresponding to a selected filter clogging state, the valve member 48d is opened to permit the fluid to by-pass the filter screen 47a and flow directly from the chamber 41 into the core 47 and out through the outlet 42. A pivotably signal arm 48e, Fig. 8 (not shown) actuated by operation of the valve member 48d via a stem 48f actuates a switch assembly 48h which signals the condition of the filler and/or shuts down machinery served by the filter when the valve member 48d opens.