Patent GB-717705-A (GB)
Title: Improvements in or relating to internal combustion engines incorporating electrostatic filters
IPC: F02M35/02
Filed: 1952-01-03
Abstract: 717,705. Electrostatic filters. SOC. FINANCIERE D'EXPANSION COMMERCIALE ET INDUSTRIELLE SOC. ANON. & SFINDEX. Jan. 3, 1952 [Jan. 10, 1951], No. 273/52. Class 39(1) [Also in Groups XXVII and XXXV] An electrostatic precipitator is provided with radioactive preionisation means, and the combination is built into the air inlet duct and/or the exhaust gas tube of an internal combustion engine such as a petrol or diesel engine, so as to precipitate solid and liquid particles therein. In one form, Fig. 2, air is drawn in through coarse mesh mechanical filter 24 and is subjected to preionisation by radioactive material such as radium 25 enclosed in a gas-tight annular wall, which emits mainly alpha particles. The conical inlet of the precipitator 5 has an air distributer 26, 27 and the outlet which may or may not have a further air distributer is connected to the carburetter. A precipitaor in the exhaust gas duct may be similarly constructed. In a modification, Fig 3 (not shown) the ionisation duct is of rectangular cross-section, the radioactive material being disposed on the two shorter walls which are spaced apart by not more than twice the maximum alpha particle range. In a modification, Fig 4 (not shown) the preionisation duct has a metallic inner surface and encloses an axial electrode so that a radial field can be set up to aid the particle charging. In another form, Fig. 5, the ionisation duct comprises two insulating walls 33, 34, narrow metallic walls with radioactive layers 29, 30, and an intermediate electrode 35 at a different potential from the metal walls. In Figs. 4, 5 the radioactive material may be placed instead on the inner or intermediate electrode which may be positive or negative with respect to the outer wall. The potential differences can be derived from the precipitator source or from a separate source. The precipitator may comprise two sets of interleaved plates connected across a voltage source, Figs. 6, 7 (not shown) and mounted in an insulating ring. The plates may be of metal and the assembly may be strengthened by insulating spacers at their mid-points. Alternatively they may be of insulating material coated with metal on one or both sides. If the coating does not extend to the edges. a metal supporting ring may be used. In another form, Figs. 8, 9, a four-ply tape consisting of metal or metallized foils 43, 45 and auxiliary layers 44, 46 is wound into a planar spiral and the protruding edges of the foils 43, 45 (foils 43, 45 being wider than 44, 46) are fixed to insulating or metal supports 47, 48. The intermediate layers 44, 46 are then removed by a process similar to that by which they were aplied i.e. by heating, by chemical action, or by dissolving in water. The two metal foils are connected across a potential source so as to set up a transverse field. In another form a number of metal or metallized tubes are arranged concentrically and connected alternately to the positive and negative terminal of the voltage source. Insulating wedge-shaped spacers may be inserted between the tubes. or the electrodes may be diecast. In another form, Figs 10, 11 (not shown) a metal or metallized disc has a large number of holes through which metal rods extend. The rods are supported by horizontal metal bars from an insulating ring. In another form, Figs 12, 13, two sets of interpenetrating metal rods, 59, 60 are respectively mounted on metal bars 57, 58 and carried from metal terminal rings 55, 56 spaced by insulating tube 54. In another form, Figs 14, 15 (not shown) a number of closely-spaced fine wire meshes extend across the air stream and alternate and intermediate meshes are connected by side lugs and common connecting leads to opposite sides of a potential source. The meshes are spaced by insulating rings. Alternatively perforated metal foils may be used. To prevent short circuiting due to large dust particles, the meshes or perforations are made very fine or the spaces between the electrodes are filled with an insulating fibrous material such as glass wool or silk fluff. In another form, Fig. 16, the precipitator 18 which may be constructed in any of the ways set out above, provided it is built of heat-resisting materials, is mounted in the exhaust gas tube. The silencer 15 (which may be dispensed with if the precipitator has sufficient silencing effect), terminates in diaphragm 69 which guides the gases to distributer 71 before preionisation. The precipitator electrodes can be removed as a unit by opening semi-cylindrical cover 72. Two springs 75 provide a resilient shockproof mounting for the electrode system, and contacts 73, 74 of the system press against counter contacts connected to battery 32. The radioactive layer 25 may be on the inner wall of duct 70 which may be of circular or rectangular section; and inner or intermediate electrodes may be employed as in Figs 4 (not shown) and 5. A power source for the precipitators is described in detail with reference to Fig 18 (not shown.) A glow lamp may be used in the circuit, preferably connected across the electrodes, to indicate that the filter is operating. It is stated that prior art precipitators not employing radioactive preionisation produce ozone and nitrous gases from inflowing air. Specification 697,918 is referred to.