# US 7,611,228 B2 · Mist ejection head and image forming apparatus comprising same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,611,228 B2 - Document ID: US7611228B2 - Status: Granted - Kind: B2 - Application number: 11/717,671 - Filed: 2007-03-14 - Published: 2007-09-20 - Granted: 2009-11-03 - Earliest claimed: 2006-03-15 - Assignees: FUJIFILM Corporation - Inventors: Sho Onozawa - Web page: https://patentgrep.com/patent/US7611228B2 ## CPC - B41J 2/06: by electric or magnetic field - B41J 2/14008: {Structure of acoustic ink jet print heads} - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS ## Abstract The mist ejection head includes: a nozzle which ejects liquid; a nozzle plate which has electrical conductivity and in which the nozzle is formed; a liquid chamber connected to the nozzle; an ultrasonic wave generating element which generates an ultrasonic wave applied to the liquid in a vicinity of the nozzle; and an electrode which is provided on a wall of the liquid chamber other than the nozzle plate, wherein an electric field applied between the nozzle plate and the electrode is controlled. ## Claims ### Claim 1 A mist ejection head comprising: a nozzle which ejects liquid; a nozzle plate which has electrical conductivity and in which the nozzle is formed; a liquid chamber connected to the nozzle; an ultrasonic wave generating element which generates an ultrasonic wave applied to the liquid in a vicinity of the nozzle; and an electrode which is provided on a wall of the liquid chamber other than the nozzle plate, wherein an electric field applied between the nozzle plate and the electrode is controlled. ### Claim 2 (depends on 1) The mist ejection head as defined in claim 1, wherein the electric field applied between the nozzle plate and the electrode is an alternating electric field. ### Claim 3 (depends on 2) The mist ejection head as defined in claim 2, wherein a frequency of the alternating electric field is ½ of a frequency at which the ultrasonic wave generating element is driven. ### Claim 4 (depends on 1) The mist ejection head as defined in claim 1, wherein, when a meniscus surface of the liquid in the nozzle has a protrusion shape in which the meniscus surface projects from a surface of the nozzle plate in terms of a liquid ejection direction, the nozzle plate and the electrode are charged in such a manner that the nozzle plate and the electrode have opposite polarities. ### Claim 5 (depends on 1) The mist ejection head as defined in claim 1, wherein, when a meniscus surface of the liquid in the nozzle has a recess shape in which the meniscus surface retreats with respect to a surface of the nozzle plate in terms of a liquid ejection direction, the nozzle plate and the electrode are charged in such a manner that the nozzle plate and the electrode have a same polarity. ### Claim 6 (depends on 1) An image forming apparatus comprising the mist ejection head as defined in claim 1. ### Claim 7 A mist ejection head comprising: a nozzle which ejects liquid; a nozzle plate which has electrical conductivity and in which the nozzle is formed; a liquid chamber connected to the nozzle; an ultrasonic wave generating element which generates an ultrasonic wave applied to the liquid in a vicinity of the nozzle; and an electrode which is provided on a wall of the liquid chamber across the liquid in the liquid chamber from the nozzle plate, wherein an electric field applied between the nozzle plate and the electrode is controlled. ### Claim 8 (depends on 7) The mist ejection head as defined in claim 7, wherein the electric field applied between the nozzle plate and the electrode is an alternating electric field. ### Claim 9 (depends on 8) The mist ejection head as defined in claim 8, wherein a frequency of the alternating electric field is ½ of a frequency at which the ultrasonic wave generating element is driven. ### Claim 10 (depends on 7) The mist ejection head as defined in claim 7, wherein, when a meniscus surface of the liquid in the nozzle has a protrusion shape in which the meniscus surface projects from a surface of the nozzle plate in terms of a liquid ejection direction, the nozzle plate and the electrode are charged in such a manner that the nozzle plate and the electrode have opposite polarities. ### Claim 11 (depends on 7) The mist ejection head as defined in claim 7, wherein, when a meniscus surface of the liquid in the nozzle has a recess shape in which the meniscus surface retreats with respect to a surface of the nozzle plate in terms of a liquid ejection direction, the nozzle plate and the electrode are charged in such a manner that the nozzle plate and the electrode have a same polarity. ### Claim 12 (depends on 7) An image forming apparatus comprising the mist ejection head as defined in claim 7. ### Claim 13 A mist ejection head comprising: a nozzle which ejects liquid; a nozzle plate which has electrical conductivity and in which the nozzle is formed; a liquid chamber connected to the nozzle; an ultrasonic wave generating element which is disposed on a lateral wall of the liquid chamber that makes contact with the nozzle plate and which generates an ultrasonic wave applied to the liquid in the liquid chamber; a reflector which has electrical conductivity and has a reflecting surface which reflects the ultrasonic wave transmitted toward a center of the liquid chamber from the ultrasonic wave generating element so as to concentrate the ultrasonic wave at a focal point located in a vicinity of the nozzle, wherein an electric field applied between the nozzle plate and the reflector is controlled. ### Claim 14 (depends on 13) The mist ejection head as defined in claim 13, wherein a cross-sectional shape of the reflecting surface of the reflector is constituted by two parabolas having a confocal point which coincides with the focal point. ### Claim 15 (depends on 13) The mist ejection head as defined in claim 13, wherein, the liquid chamber has a cylindrical shape having an axis passing through the focal point; and the reflecting surface has a protrusion shape which is formed by rotating a parabola having a central axis perpendicular to the axis of the liquid chamber, around the axis of the liquid chamber. ### Claim 16 (depends on 13) The mist ejection head as defined in claim 13, wherein the electric field applied between the nozzle plate and the reflector is an alternating electric field. ### Claim 17 (depends on 16) The mist ejection head as defined in claim 16, wherein a frequency of the alternating electric field is ½ of a frequency at which the ultrasonic wave generating element is driven. ### Claim 18 (depends on 13) The mist ejection head as defined in claim 13, wherein, when a meniscus surface of the liquid in the nozzle has a protrusion shape in which the meniscus surface projects from a surface of the nozzle plate in terms of a liquid ejection direction, the nozzle plate and the reflector are charged in such a manner that the nozzle plate and the reflector have opposite polarities. ### Claim 19 (depends on 13) The mist ejection head as defined in claim 13, wherein, when a meniscus surface of the liquid in the nozzle has a recess shape in which the meniscus surface retreats with respect to a surface of the nozzle plate in terms of a liquid ejection direction, the nozzle plate and the reflector are charged in such a manner that the nozzle plate and the reflector have a same polarity. ### Claim 20 (depends on 13) An image forming apparatus comprising the mist ejection head as defined in claim 13.