# US 9,873,204 B2 · Shaving head with doming control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,873,204 B2 - Document ID: US9873204B2 - Status: Granted - Kind: B2 - Application number: 14/363,674 - Filed: 2012-12-12 - Published: 2014-12-04 - Granted: 2018-01-23 - Earliest claimed: 2011-12-19 - Assignees: Koninklijke Philips N.V. - Applicants: Koninklijke Philips N.V. - Inventors: Jasper Zuider; Robert Godlieb; Onno Hoitinga - Web page: https://patentgrep.com/patent/US9873204B2 ## CPC - B26B 19/141: {Details of inner cutters having their axes of rotation perpendicular to the cutting surface} - B26B 19/14: of the rotary-cutter type; Cutting heads therefor; Cutters therefor (B26B19/04 takes precedence) - B26B 19/143: {Details of outer cutters} - B26B: HAND-HELD CUTTING TOOLS NOT OTHERWISE PROVIDED FOR (for harvesting A01D; for horticulture, for forestry A01G; for butchering or meat treatment A22; for manufactering or repairing footwear A43D; nail clippers or cutters A45D29/02; kitchen equipment A47J; {vegetable slicers, julienne cutters and similar devices and holders therefor, B26D3/28}; for surgical purposes A61B; for metal B23D; cutting by abrasive fluid jets B24C5/02; plier-like tools with cutting edges B25B7/22; pincers B25C11/02; handles for hand implements, in general B25G; guillotine-type cutters B26D; {perforating by non-mechanical means, e.g. by fluid jet, B26F1/26}; for erasing B43L19/00; for textile materials D06H) ## Abstract A cutter unit (1) for a rotary shaver is formed by an outer cutting element or cap (2) which interacts with a rotating inner cutting element or cutter (4) to trap and cut hairs. The cap has an annular shaving track (8) of domed cross-section having slots (30) through which the hairs may protrude. The cutter has a convex upper face (22) to engage the shaving track and a concave forward face (26). ## Claims ### Claim 1 A rotary shaver, comprising: a cap comprising one or more annular shaving tracks, the one or more annular shaving tracks comprising a plurality of slots, each slot oriented at an angle (β) to a radial direction with respect to the axis of rotation, each track having a domed shaped upper surface and a curved shaped lower surface, a cutter unit, comprising a support member having an axis of rotation and carrying a plurality of cutting elements each cutting element comprising: a leg portion, and a distal portion adjacent the leg portion, wherein the distal portion comprises: an upper face that is convex having a partial circular cylindrical shape and partially flat in a circumferential direction in a plane perpendicular to a direction of movement, said upper face terminating in a cutting edge lying in a radial plane and wherein said upper face and said cutting edge have a first radius of curvature R, a forward face, having a slightly concave shape angled at a cutter angle (α) with respect to a direction of movement of the leg portion relative to the axis of rotation of the support member, wherein the cutter angle (α) is between 40° and 50°, said forward face having a second radius of curvature r, wherein said upper face intersects the forward face in said cutting edge forming a straight line when viewed in a vertical direction at least over a portion intended to contact the shaving track formed in the cap, thus allowing a constant shearing angle β over over the radial extent of the cutter by ensuring that R=r·cos(α), wherein the second radius of curvature r depends on the cutter angle (α) such that R=r cos(α) such that the cutting edge will be located at an intersection of the forward face and the upper face. ### Claim 2 (depends on 1) The rotary shaver of claim 1, wherein the curved lower surface has a different profile to the upper surface. ### Claim 3 (depends on 1) The rotary shaver of claim 1, wherein the cutting edge and a cutting surface of at least one of the slots are angled with respect to each other at a shearing angle (β) and the shearing angle is constant over a radial extent of said at least one of the slots. ### Claim 4 (depends on 1) The rotary shaver according to claim 1, comprising at least two cutter units, each of said at least two cutter units comprising a drive unit to cause rotation of the cutter(s) of the at least two cutter units. ### Claim 5 (depends on 1) The rotary shaver according to claim 1, comprising three cutter units arranged at the vertices of an equilateral triangle. ### Claim 6 A cutter unit, comprising: a support member having an axis of rotation and carrying a plurality of cutting elements each cutting element comprising: a leg portion, and a distal portion adjacent the leg portion, wherein the distal portion comprises: an upper face that is convex having a partial circular cylindrical shape and partially flat in a circumferential direction in a plane perpendicular to a direction of movement, said upper face terminating in a cutting edge lying in a radial plane and wherein said upper face and said cutting edge have a first radius of curvature R, a forward face, having a slightly concave shape angled at a cutter angle (α) with respect to a direction of movement of the leg portion relative to the axis of rotation of the support member, wherein the cutter angle (α) is between 40° and 50°, said forward face having a second radius of curvature r, wherein said upper face intersects the forward face in said cutting edge forming a straight line when viewed in a vertical direction at least over a portion intended to contact the shaving track formed in the cap, thus allowing a constant shearing angle β over over the radial extent of the cutter by ensuring that R=r·cos(α), wherein the second radius of curvature r depends on the cutter angle (α) such that R=r cos(α) such that the cutting edge will be located at an intersection of the forward face and the upper face. ### Claim 7 (depends on 6) The cutter unit according to claim 6, wherein the cutting edge and a cutting surface of at least one of the slots are angled with respect to each other at a shearing angle (β) and the shearing angle is constant over a radial extent of said at least one of a plurality of slots of a cap having one or more annular shaving tracks comprising a plurality of slots.