# US 2025/0153484 A1 · Droplet discharge device and maintenance method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0153484 A1 - Document ID: US20250153484A1 - Status: Published application - Kind: A1 - Application number: 18/722,592 - Filed: 2022-12-23 - Published: 2025-05-15 - Earliest claimed: 2021-12-23 - Assignees: KYOCERA Corporation - Applicants: Kyocera Corporation - Inventors: Makoto TOGO; Daisuke HOZUMI - Web page: https://patentgrep.com/patent/US20250153484A1 ## CPC - B05B 15/50: Arrangements for cleaning; Arrangements for preventing deposits, drying-out or blockage; Arrangements for detecting improper discharge caused by the presence of foreign matter - B41J 2/01: Ink jet - B05B 12/006: {Pressure or flow rate sensors} - B05B 12/085: {responsive to flow or pressure of liquid or other fluent material to be discharged (B05B1/3006, B05B1/323 take precedence; spray pistols designed to control volume of flow with the controlling means being fluid actuated B05B7/1254)} - B05B 13/002: {Machines or plants for applying coating liquids or other fluent materials by inkjet} - B05B 13/0431: {with spray heads moved by robots or articulated arms, e.g. for applying liquid or other fluent material to three-dimensional [3D] surfaces} - B05B 15/58: preventing deposits, drying-out or blockage by recirculating the fluid to be sprayed from upstream of the discharge opening back to the supplying means {(B05B1/3093 takes precedence)} - B41J 2/165: Prevention {or detection} of nozzle clogging, e.g. cleaning, capping or moistening for nozzles - B41J 2/16526: {by applying pressure only} - B41J 2/17: characterised by ink handling {(cleaning by driving a fluid through the nozzles to the outside thereof B41J2/1652; for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing B41J11/0015)} - B41J 2/175: Ink supply systems {; Circuit parts therefor} - B41J 2/18: Ink recirculation systems - B41J 25/316: with tilting motion mechanisms relative to paper surface - B05B: SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES (spray-mixers with nozzles B01F25/72; processes for applying liquids or other fluent materials to surfaces by spraying B05D) - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS ## Abstract A droplet discharge device includes a droplet discharge head, a supply unit, and a controller. The droplet discharge head discharges droplets of a coloring liquid. The supply unit supplies the coloring liquid to the droplet discharge head. The controller controls each unit. During at least a part of a maintenance period after a discharge period in which droplets of the coloring liquid are discharged from the droplet discharge head, the controller controls the supply unit to supply the coloring liquid having a viscosity lower than that of the coloring liquid in the discharge period to the droplet discharge head. ## Claims ### Claim 1 A droplet discharge device, comprising: a droplet discharge head configured to discharge droplets of a coloring liquid; a supply unit configured to supply the coloring liquid to the droplet discharge head; and a controller configured to control each unit, wherein during at least a part of a maintenance period after a discharge period in which droplets of the coloring liquid are discharged from the droplet discharge head, the controller controls the supply unit to supply the coloring liquid having a lower viscosity than that of the coloring liquid in the discharge period to the droplet discharge head. ### Claim 2 (depends on 1) The droplet discharge device according to claim 1, wherein the coloring liquid is a pseudoplastic fluid whose viscosity decreases as a shear rate increases, the supply unit is a circulation mechanism configured to supply the coloring liquid to the droplet discharge head while controlling a circulation flow rate of the coloring liquid circulating between the supply unit and the droplet discharge head, and during at least a part of the maintenance period, the controller controls the circulation mechanism to increase the circulation flow rate of the coloring liquid to be higher than the circulation flow rate of the coloring liquid in the discharge period. ### Claim 3 (depends on 2) The droplet discharge device according to claim 2, wherein the controller controls the circulation mechanism to change the circulation flow rate of the coloring liquid between a first period and a second period subsequent to the first period, the first period and the second period being included in the maintenance period. ### Claim 4 (depends on 3) The droplet discharge device according to claim 3, wherein the controller controls the circulation mechanism to set the circulation flow rate of the coloring liquid to a first flow rate in the first period and to a second flow rate lower than the first flow rate in the second period. ### Claim 5 (depends on 3) The droplet discharge device according to claim 3, wherein the controller controls the circulation mechanism to set the circulation flow rate of the coloring liquid to a first flow rate in the first period and to a second flow rate higher than the first flow rate in the second period. ### Claim 6 (depends on 2) The droplet discharge device according to claim 2, wherein the controller controls the circulation mechanism in the maintenance period to stop circulation of the coloring liquid for a predetermined time and then increase the circulation flow rate of the coloring liquid. ### Claim 7 (depends on 2) The droplet discharge device according to claim 2, further comprising: a robotic arm on which the droplet discharge head is mounted such that a posture of the droplet discharge head is changeable, wherein during at least a part of the maintenance period, the controller controls the circulation mechanism to increase the circulation flow rate of the coloring liquid and controls the robotic arm to change the posture of the droplet discharge head. ### Claim 8 (depends on 7) The droplet discharge device according to claim 7, wherein the controller changes the posture of the droplet discharge head at a timing when the circulation flow rate of the coloring liquid is increased. ### Claim 9 (depends on 7) The droplet discharge device according to claim 7, wherein the droplet discharge head comprises: a supply port for supplying the coloring liquid to the inside of the droplet discharge head; and a recovery port for recovering the coloring liquid from the inside of the droplet discharge head, and the controller changes the posture of the droplet discharge head to a posture in which one of the supply port and the recovery port is located higher than the other. ### Claim 10 (depends on 9) The droplet discharge device according to claim 9, wherein the controller changes the posture of the droplet discharge head between a posture in which one of the supply port and the recovery port is located higher than the other and a posture in which the other of the supply port and the recovery port is located higher than the one. ### Claim 11 (depends on 2) The droplet discharge device according to claim 2, wherein the droplet discharge head comprises: a discharge unit comprising a nozzle, a pressurizing chamber connected to the nozzle, and a pressurizing unit configured to apply pressure to the pressurizing chamber to discharge droplets of the coloring liquid from the nozzle; a supply manifold connected to the pressurizing chamber and configured to supply the coloring liquid to the pressurizing chamber; and a recovery manifold connected to the pressurizing chamber and configured to recover the coloring liquid from the pressurizing chamber, and during at least a part of the maintenance period, the controller controls the circulation mechanism to cause the pressurizing unit to apply pressure to the pressurizing chamber while increasing the circulation flow rate of the coloring liquid. ### Claim 12 (depends on 1) The droplet discharge device according to claim 1, wherein the coloring liquid is a pseudoplastic fluid whose viscosity decreases as a shear rate increases, the supply unit is a circulation mechanism configured to supply the coloring liquid to the droplet discharge head while controlling a circulation flow rate of the coloring liquid circulating between the supply unit and the droplet discharge head, the droplet discharge head comprises: a discharge unit comprising a nozzle, a pressurizing chamber connected to the nozzle, and a pressurizing unit configured to apply pressure to the pressurizing chamber to discharge droplets of the coloring liquid from the nozzle; a supply manifold connected to the pressurizing chamber and configured to supply, to the pressurizing chamber, the coloring liquid supplied from a supply port side of the droplet discharge head; and a recovery manifold connected to the pressurizing chamber and configured to recover the coloring liquid from the pressurizing chamber and send out the coloring liquid to a recovery port side of the droplet discharge head, the pressurizing chamber and the supply manifold are connected to each other via a separate supply channel, the pressurizing chamber and the recovery manifold are connected to each other via a separate recovery channel, a channel resistance of the separate recovery channel is smaller than a channel resistance of the separate supply channel, and during at least a part of the maintenance period, the controller controls the circulation mechanism to circulate the coloring liquid from the recovery port toward the supply port. ### Claim 13 A maintenance method for a droplet discharge device comprising: a droplet discharge head configured to discharge droplets of a coloring liquid; and a supply mechanism configured to supply the coloring liquid to the droplet discharge head, the maintenance method comprising: during at least a part of a maintenance period after a discharge period in which droplets of the coloring liquid are discharged from the droplet discharge head, controlling the supply mechanism to supply the coloring liquid having a lower viscosity than that of the coloring liquid in the discharge period to the droplet discharge head.