# US 2018/0021960 A1 · Gear packaging for robotic joints > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0021960 A1 - Document ID: US20180021960A1 - Status: Published application - Kind: A1 - Application number: 15/655,310 - Filed: 2017-07-20 - Published: 2018-01-25 - Earliest claimed: 2016-07-22 - Assignees: Cambridge Medical Robotics Limited - Applicants: Cambridge Medical Robotics Limited - Inventors: James Oliver GRANT; Keith MARSHALL; Thomas Bates JACKSON - Web page: https://patentgrep.com/patent/US20180021960A1 ## CPC - B25J 17/0283: {Three-dimensional joints} - A61B 34/30: Surgical robots - B25J 9/102: {Gears specially adapted therefor, e.g. reduction gears (gearings in general F16H)} - A61B 2034/306: {Wrists with multiple vertebrae} - B25J: MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES ({manipulators specially adapted for use in surgery A61B34/70; manipulators used in cleaning hollow articles B08B9/04}; manipulators associated with rolling mills B21B39/20; manipulators associated with forging machines B21J13/10; {manipulators associated with picking-up and placing mechanisms B23P19/007}; means for holding wheels or parts thereof B60B30/00; {vehicles with ground-engaging propulsion means, e.g. walking members B62D57/02, B62D57/032; devices for picking-up and depositing articles or materials between conveyors B65G47/90, B65G47/91; manipulators with gripping or holding means for transferring packages B65H67/065}; cranes B66C; {manipulators used in the protection or supervision of pipe-line installations F17D5/00; walking equipment adapted for nuclear steam-generators F22B37/006}; manipulators specially adapted for, or associated with, nuclear reactors G21C; {apparatus used for handling wafers during manufacture or treatment of semiconductor H10P72/50}) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A robot arm comprising a first arm segment and a second arm segment coupled to each other by a first revolute joint having a first rotation axis and a second revolute joint having a second rotation axis non-parallel to the first rotation axis, and a joint mechanism for articulating the first arm segment relative to the second arm segment about the first and second rotation axes, the joint mechanism comprising: a first driven gear disposed about an axle coincident with the first rotation axis, the axle being fast with a first arm segment of the robot arm; a second driven gear disposed about the second rotation axis and fast with a second arm segment of the robot arm and fast with the first driven gear about the first rotation axis; a first drive gear configured to drive the first driven gear to rotate about the axle, the first drive gear being arranged to engage the first driven gear; a second drive gear for driving the second driven gear to rotate about the second rotation axis; and an intermediary gear arrangement arranged to engage the second drive gear and the second driven gear and being disposed about the first rotation axis, whereby rotation of the intermediary gear arrangement relative to the first arm segment about the first rotation axis can be driven. ## Claims ### Claim 1 A robot arm comprising a first arm segment and a second arm segment coupled to each other by a first revolute joint having a first rotation axis and a second revolute joint having a second rotation axis non-parallel to the first rotation axis, and a joint mechanism for articulating the first arm segment relative to the second arm segment about the first and second rotation axes, the joint mechanism comprising: a first driven gear disposed about an axle coincident with the first rotation axis, the axle being fast with a first arm segment of the robot arm; a second driven gear disposed about the second rotation axis and fast with a second arm segment of the robot arm and fast with the first driven gear about the first rotation axis; a first drive gear configured to drive the first driven gear to rotate about the axle, the first drive gear being arranged to engage the first driven gear; a second drive gear for driving the second driven gear to rotate about the second rotation axis; an intermediary gear arrangement arranged to engage the second drive gear and the second driven gear and being disposed about the first rotation axis, whereby rotation of the intermediary gear arrangement relative to the first arm segment about the first rotation axis can be driven, the intermediary gear arrangement comprising a first intermediate gear arranged to engage the second drive gear, and a second intermediate gear arranged to engage the second driven gear; and wherein at least one of the first driven gear and the first intermediate gear is a sector. ### Claim 2 (depends on 1) A robot arm as claimed in claim 1, wherein the first rotation axis is transverse to the second rotation axis. ### Claim 3 (depends on 1) A robot arm as claimed in claim 1, wherein the first rotation axis intersects the second rotation axis. ### Claim 4 (depends on 1) A robot arm as claimed in claim 1, wherein the first drive gear is attached to a first drive shaft extending along the first arm segment and/or the second drive gear is attached to a second drive shaft extending along the first arm segment. ### Claim 5 (depends on 1) A robot arm as claimed in claim 1, wherein the first drive gear is attached to a first drive shaft extending along the first arm segment and the second drive gear is attached to a second drive shaft extending along the first arm segment, and the first and second drive shafts lie on one side of a plane on which the axle lies. ### Claim 6 (depends on 1) A robot arm as claimed in claim 1, wherein the first driven gear is a ring gear. ### Claim 7 (depends on 6) A robot arm as claimed in claim 6, wherein the first driven gear is a hypoid gear. ### Claim 8 (depends on 1) A robot arm as claimed in claim 1, wherein the intermediary gear arrangement is mounted on the axle, the axle being mounted at each of its ends to the first arm segment. ### Claim 9 (depends on 1) A robot arm as claimed in claim 1, wherein the first intermediate gear is fast with the second intermediate gear. ### Claim 10 (depends on 1) A robot arm as claimed in claim 1, wherein only the first driven gear is a sector. ### Claim 11 (depends on 1) A robot arm as claimed in claim 1, wherein the operative arc of the sector is less than or equal to 50 degrees. ### Claim 12 (depends on 1) A robot arm as claimed in claim 1, wherein the first intermediate gear is a ring gear. ### Claim 13 (depends on 1) A robot arm as claimed in claim 1, wherein the first intermediate gear is a hypoid gear. ### Claim 14 (depends on 1) A robot arm as claimed in claim 1, wherein the first drive gear and first driven gear form a first hypoid gear set, and the second drive gear and first intermediate gear form a second hypoid gear set, the first and second hypoid gear sets having an equal skew offset. ### Claim 15 (depends on 1) A robot arm as claimed in claim 1, wherein the second intermediate gear and the second driven gear are bevel gears. ### Claim 16 (depends on 1) A robot arm as claimed in claim 1, wherein the joint mechanism further comprises a carrier attached to the first arm segment by the first revolute joint and attached to the second arm segment by the second revolute joint, the carrier being fast with the first driven gear. ### Claim 17 (depends on 1) A robot arm as claimed in claim 1, wherein the first and second revolute joints are wrist joints of the robotic arm. ### Claim 18 (depends on 1) A robot arm as claimed in claim 1, wherein the robot arm is a surgical robot arm, and the robot arm comprises a tool or tool attachment fast with the second arm segment about the first and second rotation axes. ### Claim 19 (depends on 18) A robot arm as claimed in claim 18, wherein the robot arm comprises a third arm segment adjacent the second arm segment and located on the opposite side of the second arm segment to the joint mechanism, and a third revolute joint that attaches the third arm segment to the second arm segment, wherein the third arm segment comprises a tool or a tool attachment. ### Claim 20 (depends on 1) A robot arm as claimed in claim 1, further comprising a control unit arranged to respond to command signals commanding motion of the robot arm by driving the first and second drive shafts to rotate, the control unit being configured to, when the robot arm is commanded to articulate about the first axis without articulating about the second axis, drive the first shaft to rotate to cause articulation about the first axis and also drive the second shaft to rotate in such a way as to negate parasitic articulation about the second axis.