# US 10,122,228 B2 · Sleeve for an electrical machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,122,228 B2 - Document ID: US10122228B2 - Status: Granted - Kind: B2 - Application number: 15/047,094 - Filed: 2016-02-18 - Published: 2016-09-15 - Granted: 2018-11-06 - Earliest claimed: 2015-03-13 - Assignees: ROLLS-ROYCE plc - Applicants: ROLLS-ROYCE plc - Inventors: Ellis F H Chong; Martyn A. Jones; Geraint W. Jewell - Web page: https://patentgrep.com/patent/US10122228B2 ## CPC - H02K 1/274: the rotor consisting of two or more circumferentially positioned magnets - H02K 1/28: Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures - H02K 15/14: Casings; Enclosures; Supports - Y02E 10/72: Wind turbines with rotation axis in wind direction - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A sleeve for retaining magnets around a rotor of an electrical machine. The sleeve is cylindrical and hollow, having axial length and having radial thickness between its inner surface and outer surface. The sleeve defines a plurality of axially spaced, circumferentially extending grooves. Each groove has radial depth which is less than the radial thickness of the sleeve. ## Claims ### Claim 1 A sleeve for retaining magnets around a rotor of an electrical machine, the sleeve comprising: a body that is cylindrical and hollow, the body having an inner surface and an outer surface, the body having an axial length and a radial thickness between the inner surface and the outer surface; and a first plurality of axially spaced, circumferentially extending grooves formed in the inner surface of the body, each groove of the first plurality of grooves having a radial depth less than the radial thickness of the sleeve and extending circumferentially through less than 360°. ### Claim 2 (depends on 1) The sleeve as claimed in claim 1, wherein a radial bridge is a difference between the radial thickness of the sleeve and the radial depth of each groove of the first plurality of grooves, the radial bridge being greater than or equal to ⅓ of an electrical skin depth of the sleeve. ### Claim 3 (depends on 2) The sleeve as claimed in claim 2, wherein the radial depth of each radial bridge of each groove of the first plurality of grooves is equal to ⅓ of the radial thickness of the sleeve where the electrical skin depth is greater than the radial thickness of the sleeve. ### Claim 4 (depends on 1) The sleeve as claimed in claim 1, wherein the grooves of the first plurality of grooves have the same radial depth. ### Claim 5 (depends on 1) The sleeve as claimed in claim 1, wherein each groove of the first plurality of grooves extends circumferentially through at least 60°. ### Claim 6 (depends on 1) The sleeve as claimed in claim 1, wherein a circumferential bridge is defined between circumferential ends of one or two circumferentially aligned grooves of the first plurality of grooves, and axially adjacent circumferential bridges are circumferentially offset. ### Claim 7 (depends on 6) The sleeve as claimed in claim 6, wherein two or more circumferential bridges are axially aligned and circumferentially spaced. ### Claim 8 (depends on 7) The sleeve as claimed in claim 7, wherein the axially aligned grooves of the first plurality of grooves have equal circumferential extent. ### Claim 9 (depends on 1) The sleeve as claimed in claim 1, further comprising a second plurality of grooves extending around the outer surface of the sleeve. ### Claim 10 (depends on 9) The sleeve as claimed in claim 9, wherein at least one groove of the first plurality of grooves is radially aligned with at least one groove of the second plurality of grooves. ### Claim 11 (depends on 9) The sleeve as claimed in claim 9, wherein a combined radial depth including the radial depth of the first plurality of grooves and a radial depth of the second plurality of grooves is less than the radial thickness of the sleeve. ### Claim 12 (depends on 1) The sleeve as claimed in claim 1, wherein the sleeve is metal. ### Claim 13 (depends on 1) An electrical machine rotor comprising: a rotor shaft; a plurality of permanent magnets located in a circumferential array around a surface of the rotor shaft; and the sleeve as claimed in claim 1, the sleeve being affixed radially outside the plurality of permanent magnets to retain them to the rotor shaft. ### Claim 14 (depends on 1) An electrical machine rotor comprising: a rotor shaft; at least one electrical coil located on a surface of the rotor shaft; and the sleeve as claimed in claim 1, the sleeve being affixed radially outside the at least one electrical coil to retain the at least one electrical coil to the rotor shaft. ### Claim 15 (depends on 13) An electrical machine comprising the electrical machine rotor as claimed in claim 13. ### Claim 16 (depends on 1) A method of fabricating the sleeve as claimed in claim 1, the method comprising steps to: form the cylindrical sleeve; and cut the first plurality axially spaced, circumferentially extending grooves into the inner surface of the sleeve. ### Claim 17 (depends on 16) A method as claimed in claim 16, wherein the step to cut the grooves is performed by water jet machining.