Gear packaging for robotic arms

A robot arm comprising a joint mechanism configured to articulate one limb of the arm relative to another limb of the arm about two non-parallel rotation axes, the mechanism comprising:

• an intermediate carrier attached to a first one of the limbs by a first revolute joint having a first rotation axis and to a second one of the limbs by a second revolute joint having a second rotation axis;
• a first drive gear disposed about the first rotation axis and fast with the carrier, whereby rotation of the carrier relative to the first limb about the first rotation axis can be driven;
• and
• a second drive gear disposed about the second rotation axis and fast with the second one of the limbs, whereby rotation of the second one of the limbs about the second rotation axis relative to the carrier can be driven;
• wherein at least one of the first and second drive gears is a sector gear, and
• wherein the sector gear is a bevel gear.