# US 2018/0320709 A1 · Fan with impeller based on an audio spread-spectrum > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0320709 A1 - Document ID: US20180320709A1 - Status: Published application - Kind: A1 - Application number: 15/589,066 - Filed: 2017-05-08 - Published: 2018-11-08 - Earliest claimed: 2017-05-08 - Assignees: Microsoft Technology Licensing, LLC - Applicants: Microsoft Technology Licensing, LLC - Inventors: Gregory M. DALY - Web page: https://patentgrep.com/patent/US20180320709A1 ## CPC - F04D 29/666: {by means of rotor construction or layout, e.g. unequal distribution of blades or vanes} - F04D 25/08: the working fluid being air, e.g. for ventilation - F04D 29/281: {for fans or blowers} - F04D 29/328: {with unequal distribution of blades around the hub} - F04D 29/662: {Balancing of rotors (compensating imbalance G01M1/36)} - F04D 29/663: {Sound attenuation} - G05B 15/02: electric - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) ## Abstract A fan for cooling an electronic device is described, wherein the fan can include an enclosure and a motor secured within the enclosure. The fan can also include an impeller to be turned by the motor, the impeller having a plurality of blades, wherein an angular spacing of the blades results in an audio spread-spectrum within a range of audio frequencies. In some examples, an arrangement of the blades has a center of mass below a threshold, and the angular spacing of the blades and a blade pass frequency (BPF) results in sound that is distributed in the range of audio frequencies. ## Claims ### Claim 1 A fan for cooling an electronic device, the fan comprising: an enclosure; a motor secured within the enclosure; and an impeller to be turned by the motor, the impeller having a plurality of blades, wherein an angular spacing of the blades results in an audio spread-spectrum within a range of audio frequencies, and wherein an arrangement of the blades has a center of mass below a threshold, and wherein the angular spacing of the blades and a blade pass frequency (BPF) results in sound that is distributed in the range of audio frequencies. ### Claim 2 (depends on 1) The fan recited in claim 1, wherein the arrangement of the blades is determined by calculating the center of mass of the impeller based on a cardinal direction, an X-axis coordinate, a Y-axis coordinate, and an angle for each of the blades. ### Claim 3 (depends on 2) The fan recited in claim 2, wherein the arrangement of the blades is determined by calculating a modified center of mass based on sorting the blades by grouping a blade with a smallest angle with a blade with a largest angle; removing the grouped blades; and grouping additional blades in response to detecting ungrouped blades. ### Claim 4 (depends on 3) The fan recited in claim 3, wherein the arrangement of the blades is determined by detecting a blade corresponding to an angle nearest the center of mass and a blade corresponding to an angle furthest from the center of mass; and revising the modified center of mass based on swapping the blade corresponding to the angle nearest the center of mass and the blade corresponding to the angle furthest from the center of mass with the blade with the smallest angle and the blade with the largest angle. ### Claim 5 (depends on 3) The fan recited in claim 3, wherein the arrangement of blades is determined by detecting a predetermined number of blades adjacent to an angle equal to plus or minus ninety degrees in relation to the modified center of mass; identifying a plurality of blade permutations based on swapping the predetermined number of blades; and revising the modified center of mass based on a blade permutation with a lowest center of mass value. ### Claim 6 (depends on 3) The fan recited in claim 3, wherein the arrangement of blades is determined by detecting a blade corresponding to a predetermined angular offset in relation to the modified center of mass; and revising the modified center of mass based on swapping the blade corresponding to the predetermined angular offset with a predetermined number of blades corresponding to angles with an absolute value difference that is below a threshold value. ### Claim 7 (depends on 3) The fan recited in claim 3, wherein the arrangement of blades is determined using a first iterative swap technique to select a blade and swap the selected blade with a predetermined number of blades corresponding to angles with an absolute value difference that is below a threshold value; and to revise the modified center of mass in response to repeating the first iterative swap technique for each of the blades. ### Claim 8 (depends on 7) The fan recited in claim 7, wherein the arrangement of the blades is determined using a second iterative swap technique to select a blade and revise the modified center of mass based on swapping the selected blade with a predetermined number of blades corresponding to angles with an absolute value difference that is below a threshold value; and to repeat the second iterative swap technique for each of the blades; and to revise the center of mass based on swapping a plurality of pairs of blades corresponding to a target angle and an offset angle. ### Claim 9 A method of operating a fan, comprising: driving a fan with a motor, the fan having an impeller with a plurality of blades, the blades being angularly spaced around a hub to provide an audio spread-spectrum within a range of audio frequencies, and wherein an arrangement of the blades has a center of mass below a threshold, and wherein the angular spacing of the blades and a blade pass frequency (BPF) results in sound that is distributed in the range of audio frequencies. ### Claim 10 (depends on 9) The method of claim 9, wherein the arrangement of the blades is determined by calculating the center of mass of the impeller based on a cardinal direction, an X-axis coordinate, a Y-axis coordinate, and an angle for each of the blades. ### Claim 11 (depends on 10) The method of claim 10, wherein the arrangement of the blades is determined by calculating a modified center of mass based on sorting the blades by grouping a blade with a smallest angle with a blade with a largest angle; removing the grouped blades; and grouping additional blades in response to detecting ungrouped blades. ### Claim 12 (depends on 11) The method of claim 11, wherein the arrangement of the blades is determined by detecting a blade corresponding to an angle nearest the center of mass and a blade corresponding to an angle furthest from the center of mass; and revising the modified center of mass based on swapping the blade corresponding to the angle nearest the center of mass and the blade corresponding to the angle furthest from the center of mass with the blade with the smallest angle and the blade with the largest angle. ### Claim 13 (depends on 12) The method of claim 12, wherein the arrangement of blades is determined by detecting a predetermined number of blades adjacent to an angle equal to plus or minus ninety degrees in relation to the modified center of mass; identifying a plurality of blade permutations based on swapping the predetermined number of blades; and revising the modified center of mass based on a blade permutation with a lowest center of mass value. ### Claim 14 (depends on 11) The method of claim 11, wherein the arrangement of blades is determined by detecting a blade corresponding to a predetermined angular offset in relation to the modified center of mass; and revising the modified center of mass based on swapping the blade corresponding to the predetermined angular offset with a predetermined number of blades corresponding to angles with an absolute value difference that is below a threshold value. ### Claim 15 (depends on 11) The method of claim 11, wherein the arrangement of blades is determined using a first iterative swap technique to select a blade and swap the selected blade with a predetermined number of blades corresponding to angles with an absolute value difference that is below a threshold value; and to revise the modified center of mass in response to repeating the first iterative swap technique for each of the blades. ### Claim 16 (depends on 11) The method of claim 11, wherein the arrangement of the blades is determined using a second iterative swap technique to select a blade and revise the modified center of mass based on swapping the selected blade with a predetermined number of blades corresponding to angles with an absolute value difference that is below a threshold value; and to repeat the second iterative swap technique for each of the blades; and to revise the center of mass based on swapping a plurality of pairs of blades corresponding to a target angle and an offset angle. ### Claim 17 A method for designing impellers, comprising: detecting a number of blades to be included in an impeller design and a mechanical tolerance of the blades; detecting a plurality of algorithms corresponding to the impeller design, wherein the plurality of algorithms identify an angular spacing of the blades that results in an audio spread-spectrum within a range of audio frequencies; generating the impeller design based on the plurality of algorithms, wherein the impeller design comprises an arrangement of the plurality of blades with a center of mass below a threshold, and wherein the angular spacing of the blades and a blade pass frequency (BPF) results in sound that is distributed in the range of audio frequencies; and transmitting instructions to a fabrication device to manufacture an impeller based on the impeller design. ### Claim 18 (depends on 17) The method of claim 17, wherein a first algorithm of the plurality of algorithms comprises calculating the center of mass of the impeller design based on a cardinal direction, an X-axis coordinate, a Y-axis coordinate, and an angle for each of the blades. ### Claim 19 (depends on 18) The method of claim 18, wherein a second algorithm of the plurality of algorithms comprises calculating a modified center of mass based on sorting the blades by grouping a blade with a smallest angle with a blade with a largest angle; removing the grouped blades; and grouping additional blades in response to detecting ungrouped blades. ### Claim 20 (depends on 19) The method of claim 19, wherein a third algorithm of the plurality of algorithms comprises detecting a blade corresponding to an angle nearest the center of mass and a blade corresponding to an angle furthest from the center of mass; and revising the modified center of mass based on swapping the blade corresponding to the angle nearest the center of mass and the blade corresponding to the angle furthest from the center of mass with the blade with the smallest angle and the blade with the largest angle.