| 摘要 |
756,610. Filters. PUROLATOR PRODUCTS, Inc. May 28, 1954 [June 26, 1953], No. 15823/54. Class 46. [Also in Group XXII] A metallic filter unit 10, Fig. 2, comprising a hollow open-ended cylinder and being one of three kinds-namely a ribbon having projections on one wide face, wound helically so that the wide faces are normal to the axis of the cylinder so formed and supported on a fluted drum; a ribbon similarly wound, coated with fusible material and subsequently heated and cooled to render the element self supporting and the fluted drum unnecessary; and a stack of rings or washers provided with raised portions-is mounted between end pieces and connected to a suction line 19, and sprayed (20) with a dispersion of metallic dust in a volatile or partially-volatile liquid dispersant. Metallic dust, ranging in size from 10 to 40 microns, is dispersed in a liquid dispersant such as alcohol, acetone or carbon tetrachloride. A powder of rock wool or glass may be mixed with the metal powder. As an alternative to spraying the unit may be dipped in, or brushed with, the dispersion. In all cases excess is wiped off, and the unit is allowed to stand for a time sufficient to allow the volatile portion of the dispersion to evaporate. It is then subjected in an oven to a sintering temperature so that the dust is sintered and attached to the unit. The extent of the ensuing reduction of filtering interstices 13b, Fig. 8, may be controlled by regulating the thickness of the coating, by varying the percentage of dust and by using dispersants of different viscosities. In a second method the dispersant comprises a lacquer consisting of a non-volatile resin such as lac and a volatile solvent such as methyl alcohol. On completion of the coating step the unit is heated in an oven to dry the coating by evaporation of the volatile portion. The unit is next transferred to an oven maintained at a higher temperature where the non-volatile portions of the lacquer are burned off, leaving charred skeletal remains, intermingled with the metallic dust, and voids. The unit is finally subjected to a sintering temperature. In a third method the percentage of metal in the dispersion is relatively high, and the dispersant is that used in the second method. After application of the dispersion to the unit the latter is subjected to electroplating in a bath of e.g. alkaline copper sulphate solution at a current density of e.g. 100 amps. sq. ft. for a time sufficient to effect a plating action equivalent to 2500 amp. minutes per square foot. After washing, the unit is heated at a temperature of from 300‹ to 400‹ F. There results a porous coating consisting of electroplated dust particles 21b, charred particles 23b of the lacquer component and voids 24b, Fig. 8. One form of stacked ring unit to which the invention may be applied is shown in Fig. 13. Specification 665,149 is referred to.
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