# US 2021/0276027 A1 · Rotary atomizer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0276027 A1 - Document ID: US20210276027A1 - Status: Published application - Kind: A1 - Application number: 17/295,357 - Filed: 2019-11-05 - Published: 2021-09-09 - Earliest claimed: 2018-11-27 - Assignees: Dürr Systems AG - Applicants: Dürr Systems AG - Inventors: Hans-Jürgen Nolte; Andreas Fischer - Web page: https://patentgrep.com/patent/US20210276027A1 ## CPC - B05B 3/1014: {with a spraying edge, e.g. like a cup or a bell} - B05B 3/1042: {Means for connecting, e.g. reversibly, the rotating spray member to its driving shaft} - B05B 3/1064: {the liquid or other fluent material to be sprayed being axially supplied to the rotating member through a hollow rotating shaft} - B05B 3/1092: {Means for supplying shaping gas} - 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 - B05B 15/555: discharged by cleaning nozzles - 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) ## Abstract The disclosure relates to a rotary atomizer for applying a spray jet of a coating agent (e.g. paint) to a component (e.g. motor vehicle body component). The disclosure provides that the construction dimensions of the rotary atomizer are coordinated in such a way that the air pressure at the outlet opening of the paint nozzle during operation is lower than the air pressure in the nozzle chamber of the bell cup and in the external rinsing channels in order to prevent a backflow of the coating agent from the outlet opening of the paint nozzle backwards in the direction of the nozzle chamber due to the pressure difference. ## Claims ### Claim at position 1 1-14. (canceled) ### Claim 15 Rotary atomizer for applying a spray jet of a coating agent to a component, comprising: a) a shaping air ring to discharge shaping air to form the spray jet of the coating agent, b) a hollow bell cup shaft rotating during operation, c) a paint tube arranged substantially coaxially in the hollow bell cup shaft, wherein the bell cup shaft and the internal paint tube enclose an annular gap with a certain gap width in radial direction, d) a paint nozzle which is arranged substantially coaxially in the paint tube and discharges the coating agent to be applied substantially in the axial direction through an outlet opening, e) a bell cup mounted on the bell cup shaft and rotating during operation with e1) a gap between the front side of the shaping air ring and the rear side of the bell cup with a certain gap width in axial direction, e2) a central bore for axial feed-through of the paint nozzle with an annular gap between the bell cup and the paint nozzle with a certain gap width in radial direction, e3) an annular spray edge for spraying the coating agent, e4) an outer circumferential surface, e5) an exterior rinsing chamber on the rear side of the bell cup for rinsing the outer circumferential surface with a rinsing agent, the exterior rinsing chamber forming an annular gap on the outside of the bell cup shaft with a specific gap width in the radial direction, e6) several exterior rinsing channels in the bell cup between the paint nozzle and the exterior rinsing chamber for feeding rinsing agent from the paint nozzle onto the outer circumferential surface of the bell cup for exterior rinsing of the bell cup, e7) a nozzle chamber on the rear side of the bell cup for receiving the paint nozzle with an annular gap between the paint nozzle and the inner wall of the nozzle chamber with a certain gap width in radial direction, e8) an overflow surface at the front face, wherein the coating agent to be applied, coming from the outlet opening of the paint nozzle, flows in operation outwards over the overflow surface to the spray edge of the bell cup, and e9) a distributor disc for distributing the coating agent emerging from the outlet opening of the paint nozzle, wherein the distributor disc is arranged in the bell cup at the front side, directs the coating agent coming from the paint nozzle partly radially outwards onto the overflow surface of the bell cup and partly axially through a central bore in the distributor disc onto the end face of the distributor disc, wherein the distributor disc encloses with the overflow surface of the bell cup a gap with a certain gap width, e10) a distributor disc holder which is arranged in the bell cup and has a central bore with a specific diameter, the distributor disc being mounted on the distributor disc holder, f) wherein the rotary atomizer is designed in such a way that the air pressure at the outlet opening of the paint nozzle during operation is lower than the air pressure in the nozzle chamber of the bell cup and in the outer rinsing channels, in order to prevent a backflow of the coating agent from the outlet opening of the paint nozzle backwards in the direction of the nozzle chamber as a result of the pressure difference. ### Claim 16 (depends on 15) Rotary atomizer according to claim 15, wherein the following design dimensions of the rotary atomizer are matched to one another in such a way that the air pressure at the outlet opening of the paint nozzle during operation is lower than the air pressure in the nozzle chamber of the bell cup and in the outer rinsing channels: a) the diameter of the central bore in the distributor disc holder of the bell cup, b) the gap width of the gap between the distributor disc and the overflow surface of the bell cup, c) the gap width of the annular gap between the bell cup and the paint nozzle, d) the gap width of the annular gap between the paint nozzle and the inner wall of the nozzle chamber, e) the gap width of the annular gap between the bell cup shaft and the internal paint tube, f) the gap width of the annular gap of the exterior rinsing chamber on the outside of the bell cup shaft, and g) the gap width of the gap between the front side of the shaping air ring and the rear side of the bell cup. ### Claim 17 (depends on 15) Rotary atomizer according to claim 15, wherein the number of external rinsing channels in the bell cup is less than 65 to achieve the pressure ratio to prevent the backflow. ### Claim 18 (depends on 15) Rotary atomizer according to claim 15, wherein the external rinsing channels together have a total cross-sectional area smaller than 20 mm2 to achieve the pressure ratio to prevent the backflow. ### Claim 19 (depends on 15) Rotary atomizer according to claim 15, wherein the external rinsing channels each have an internal diameter of 1 mm-2 mm in order to achieve the pressure ratio to prevent the backflow. ### Claim 20 (depends on 15) Rotary atomizer according to claim 15, wherein the external rinsing channels each have a total length of 5 mm-15 mm. ### Claim 21 (depends on 15) Rotary atomizer according to claim 15, wherein a) the external rinsing channels each consist of several straight tap bores which merge into one another and are angled towards one another, and b) the tap holes opening into the exterior rinsing chamber of the bell cup are shorter than the tap holes on the paint nozzle side. ### Claim 22 (depends on 21) Rotary atomizer according to claim 21, wherein the shorter tap holes opening into the exterior rinsing chamber of the bell cup each have a length of 0.5 mm-2 mm. ### Claim 23 (depends on 22) Rotary atomizer according to claim 22, wherein the longer tap bores on the paint nozzle side each have a length of 5 mm-10 mm. ### Claim 24 (depends on 15) Rotary atomizer according to claim 15, wherein the exterior rinsing chamber in the bell cup has an external diameter of more than 30.5 mm in order to achieve the pressure ratio to avoid the backflow. ### Claim 25 (depends on 15) Rotary atomizer according to claim 15, wherein the gap width of the gap between the overflow surface of the bell cup and the distributor disc is in the range of 0.1 mm-0.25 mm. ### Claim 26 (depends on 15) Rotary atomizer according to claim 15, wherein the gap between the overflow surface of the bell cup and the distributor disc has a gap length in the flow direction which is in the range of 3 mm-10 mm. ### Claim 27 (depends on 15) Rotary atomizer according to claim 15, wherein the nozzle chamber in the bell cup has an external diameter of more than 11 mm, in order to increase the radial gap width between the paint nozzle and the inner wall of the nozzle chamber and thereby to achieve the pressure ratio to reduce the backflow. ### Claim 28 (depends on 15) Rotary atomizer according to claim 15, wherein a) the axial gap between the shaping air ring and the rear side of the bell cup has an axial gap width which is greater than 3.0 mm, in order to achieve the pressure ratio to prevent the backflow, and b) the bell cup shaft is exposed in the axial gap between the shaping air ring and the rear side of the bell cup without an external cover in order to achieve the pressure ratio to prevent the backflow. ### Claim 29 (depends on 15) Rotary atomizer according to claim 15, wherein the paint nozzle has an outer diameter of less than 4 mm at its free end. ### Claim 30 (depends on 15) Rotary atomizer according to claim 15, wherein the central bore in the distributor disc holder has a diameter of substantially 3.2 mm or 3.8 mm. ### Claim 31 (depends on 30) Rotary atomizer according to claim 30, wherein the annular gap between the inner paint nozzle and the outer distributor disc holder has a radial gap width of 0.2 mm-0.6 mm. ### Claim 32 (depends on 30) Rotary atomizer according to claim 30, wherein the annular gap between the inner paint nozzle and the outer distributor disc holder has an axial gap length of 4.5 mm-8.5 mm. ### Claim 33 (depends on 30) Rotary atomizer according to claim 30, wherein the annular gap between the inner paint nozzle and the outer distributor disc holder has a cross-sectional area of 2 mm2-7 mm2 in an axial cross section. ### Claim 34 Operating method for a rotary atomizer in accordance with one of the preceding claims, wherein the air pressure at the outlet opening of the paint nozzle is lower than the air pressure in the nozzle chamber of the bell cup and in the outer rinsing channels in order to prevent a backflow of the coating agent from the outlet opening of the paint nozzle backwards in the direction of the nozzle chamber due to the pressure difference. ### Claim 35 (depends on 34) Operating method according to claim 34, wherein a) the bell cup shaft rotates at a certain speed, b) the paint nozzle discharges the coating agent with a certain flow rate, c) the shaping air ring discharges the shaping air with a certain flow rate, and d) the following design dimensions and operating parameters are matched to one another in such a way that the air pressure at the outlet opening of the paint nozzle is lower than the air pressure in the nozzle chamber of the bell cup and in the outer rinsing channels, in order to prevent a backflow of the coating agent from the outlet opening of the paint nozzle backwards in the direction of the nozzle chamber as a result of the pressure difference: d1) the diameter of the central bore in the distributor disc holder of the bell cup, d2) the gap width of the gap between the distributor disc and the overflow surface of the bell cup, d3) the gap width of the annular gap between the bell cup and the paint nozzle, d4) the gap width of the annular gap between the paint nozzle and the inner wall of the nozzle chamber, d5) the gap width of the annular gap between the bell cup shaft and the internal paint tube, d6) the gap width of the annular gap of the exterior rinsing chamber on the outside of the bell cup shaft, and d7) the gap width of the gap between the front side of the shaping air ring and the rear side of the bell cup, d8) the speed of the bell cup shaft, d9) the flow rate of the coating agent, and d10) the flow rate of the shaping air. ### Claim 36 (depends on 15) Coating robot with several movable axes and a rotary atomizer according to claim 15.