# US 8,465,574 B2 · Filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,465,574 B2 - Document ID: US8465574B2 - Status: Granted - Kind: B2 - Application number: 12/837,262 - Filed: 2010-07-15 - Published: 2011-01-27 - Granted: 2013-06-18 - Earliest claimed: 2009-07-24 - Assignees: Dyson Technology Limited - Applicants: Lucas Horne - Inventors: Lucas Horne - Web page: https://patentgrep.com/patent/US8465574B2 ## CPC - A47L 9/10: Filters (in general B01D; cyclones B04C); Dust separators; Dust removal; Automatic exchange of filters {(for machines for cleaning floors A47L11/40)} - A47L 9/12: Dry filters - B03C 3/017: Combinations of electrostatic separation with other processes, not otherwise provided for - B03C 3/025: {Combinations of electrostatic separators, e.g. in parallel or in series, stacked separators or dry-wet separator combinations} - B03C 3/15: Centrifugal forces - B03C 3/155: Filtration - B03C 3/30: in which electrostatic charge is generated by passage of the gases, i.e. tribo-electricity - B03C 3/41: Ionising-electrodes - A47L: DOMESTIC WASHING OR CLEANING (brushes A46B; cleaning quantities of bottles or of other hollow articles of one kind B08B9/00; laundry D06F); SUCTION CLEANERS IN GENERAL (cleaning in general B08) - B03C: MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS (separating isotopes B01D59/00; combinations of magnetic or electrostatic separation with separation of solids by other means B03B, B07B) ## Abstract The present invention relates to an electrostatic filter. Particularly but not exclusively the invention relates to an electrostatic filter for removing dust particles, for example an electrostatic filter for use in a vacuum cleaner, fan or air conditioner. The electrostatic filter includes a filter medium located between a first and a second electrode, each at a different voltage during use, such that a potential difference is formed across the filter medium, the first and second electrodes being substantially non-porous. ## Claims ### Claim 1 An electrostatic filter comprising: a filter medium located between a first and a second electrode, each at a different voltage during use, such that a potential difference is formed across the filter medium, the first and second electrodes being substantially non-porous, wherein the electrostatic filter further comprises at least one corona discharge mechanism, wherein the corona discharge mechanism comprises at least one corona discharge electrode of high curvature and at least one electrode of low curvature. ### Claim 2 (depends on 1) An electrostatic filter according to claim 1, wherein the filter medium has a length and the first and second electrodes are non-porous along the length of the filter medium. ### Claim 3 (depends on 1) An electrostatic filter according to claim 1, wherein the first and second electrodes are non-porous along their entire length. ### Claim 4 (depends on 1) An electrostatic filter according to claim 1, wherein the filter medium is in contact with the first and/or the second electrode. ### Claim 5 (depends on 1) An electrostatic filter according to claim 1, wherein the filter medium is an electrically resistive filter medium. ### Claim 6 (depends on 1) An electrostatic filter according to claim 1, wherein the corona discharge mechanism is arranged upstream of the filter medium. ### Claim 7 (depends on 1) An electrostatic filter according to claim 1, wherein the corona discharge electrode is formed from a portion of the first or second electrode. ### Claim 8 (depends on 1) An electrostatic filter according to claim 1, wherein the corona discharge electrode is in the form of one or more points formed from, or on, an edge of the first or second electrode. ### Claim 9 (depends on 1) An electrostatic filter according to claim 1, wherein a lower edge or upper edge of the second electrode is serrated to form the corona discharge electrode. ### Claim 10 (depends on 1) An electrostatic filter according to claim 1, wherein the electrode of low curvature is formed from a portion of the first or second electrode. ### Claim 11 (depends on 1) An electrostatic filter according to claim 1, wherein the electrode of low curvature is arranged upstream of the filter medium. ### Claim 12 (depends on 1) An electrostatic filter according to claim 1, wherein the electrode of low curvature is located both upstream and downstream of the corona discharge electrode. ### Claim 13 (depends on 1) An electrostatic filter according to claim 1, wherein the corona discharge electrode is remote from the first and second electrodes. ### Claim 14 (depends on 13) An electrostatic filter according to claim 13, wherein the corona discharge electrode is in the form of one or more wires, needles, points or serrations. ### Claim 15 (depends on 1) An electrostatic filter according to claim 1, further comprising a third electrode. ### Claim 16 (depends on 15) An electrostatic filter according to claim 15, wherein the second electrode is located between the first and the third electrodes. ### Claim 17 (depends on 1) An electrostatic filter according to claim 1, wherein the electrodes are planar. ### Claim 18 (depends on 15) An electrostatic filter according to claim 15, wherein the electrodes are cylindrical. ### Claim 19 (depends on 15) An electrostatic filter according to claim 15, wherein the second electrode is concentrically located between the first and the third electrodes. ### Claim 20 (depends on 15) An electrostatic filter according to claim 15, wherein a further filter medium is located between the second and third electrodes, the second and third electrodes being at a different voltage during use such that a potential difference is formed across the further filter medium. ### Claim 21 (depends on 15) An electrostatic filter according to claim 15, wherein the first and the third electrodes are at the same voltage during use. ### Claim 22 (depends on 1) An electrostatic filter according to claim 1, wherein the second electrode is negatively charged. ### Claim 23 (depends on 1) An electrostatic filter according to claim 1, wherein the first and/or second electrode is formed from a conductive metal sheet or foil of from 0.1 mm, or 0.25 mm, or 0.5 mm, or 1 mm, or 1.5 mm, or 2 mm to 2.5 mm, or 3 mm, or 4 mm in thickness. ### Claim 24 (depends on 15) An electrostatic filter according to claim 15, wherein the third electrode is formed from a conductive metal sheet or foil of from 0.1 mm, or 0.25 mm, or 0.5 mm, or 1 mm, or 1.5 mm, or 2 mm to 2.5 mm, or 3 mm, or 4 mm in thickness. ### Claim 25 (depends on 1) An electrostatic filter according to claim 1, wherein the filter medium is an open cell reticulated polyurethane foam derived from a polyester. ### Claim 26 (depends on 1) An electrostatic filter according to claim 1, wherein the pore size of the filter medium varies along its length. ### Claim 27 (depends on 1) A vacuum cleaner comprising an electrostatic filter according to claim 1.