Speed reducer, joint assembly and electric pendulum

A joint assembly, comprising:

• a speed reducer, comprising
• a housing,
• an internal gear rotatably and at least partially supported in the housing, the internal gear having a concentric internal gear hole having a peripheral surface with internal teeth arranged thereon and an internal gear through-hole,
• an external gear at least partially arranged in the concentric internal gear hole and having external teeth meshing with the internal teeth of the concentric internal gear hole to drive the internal gear to rotate, the external gear having an external gear through-hole,
• an eccentric wheel rotatably and at least partially arranged in the external gear through-hole, the eccentric wheel having an eccentric wheel hole extending through the eccentric wheel, wherein a rotation axis of the eccentric wheel is coaxial with a central axis of the internal gear, and the eccentric wheel is configured to drive the external gear to revolve around the rotation axis of the eccentric wheel,
• a limiting disc arranged in the housing, the limiting disc being engaged with the housing so that the limiting disc and the housing are limited to relative movement in a first direction, and the limiting disc being engaged with the external gear so that the limiting disc and the external gear are limited to relative movement in a second direction, wherein the first direction, the second direction, and an axial direction of the limiting disc are orthogonal to each other,
• a drive member connected to the eccentric wheel to drive the eccentric wheel to rotate, the drive member having a hole therethrough, and
• a positioning shaft connected to a wall of the housing and extending from the wall through the hole of the drive member, the eccentric wheel hole of the eccentric wheel, the external gear through-hole of the external gear, and the internal gear through-hole of the internal gear;
• and
• a motor configured to drive the drive member to rotate.

An electric pendulum, comprising:

• a joint assembly comprising a speed reducer and a motor;
• and
• a swing arm,
• wherein the speed reducer comprises:
• a housing,
• an internal gear rotatably and at least partially supported in the housing, the internal gear having a concentric internal gear hole having a peripheral surface with internal teeth arranged thereon and an internal gear through-hole,
• an external gear at least partially arranged in the concentric internal gear hole and having external teeth meshing with the internal teeth of the concentric internal gear hole to drive the internal gear to rotate, the external gear having an external gear through-hole,
• an eccentric wheel rotatably and at least partially arranged in the external gear through-hole, the eccentric wheel having an eccentric wheel hole extending through the eccentric wheel, wherein a rotation axis of the eccentric wheel is coaxial with a central axis of the internal gear, and the eccentric wheel is configured to drive the external gear to revolve around the rotation axis of the eccentric wheel,
• a limiting disc arranged in the housing, the limiting disc being engaged with the housing so that the limiting disc and the housing are limited to relative movement in a first direction, and the limiting disc being engaged with the external gear so that the limiting disc and the external gear are limited to relative movement in a second direction, wherein the first direction, the second direction, and an axial direction of the limiting disc are orthogonal to each other,
• a drive member connected to the eccentric wheel to drive the eccentric wheel to rotate, the drive member having a hole therethrough, and
• a positioning shaft connected to a wall of the housing and extending from the wall through the hole of the drive member, the eccentric wheel hole of the eccentric wheel, the external gear through-hole of the external gear, and the internal gear through-hole of the internal gear,
• wherein the motor is configured to drive the drive member to rotate, and the swing arm is connected to the internal gear to be driven to swing by the internal gear.