Magnetic rotational hardstop for robot

摘要

Rotational hardstop assemblies that provide greater than 360 degrees of non-continuous rotation for rotating mechanisms are provided. In certain embodiments, an assembly is used to provide 630 or more degrees of rotation for the shoulder axis of a robot, such as a wafer transfer robot. The rotational hardstop assemblies include opposing magnets as springs. According to various embodiments, the opposing magnets provide non-contact engagement and produce no contact noise nor have any wear over time. The rotational hardstop assemblies provide the ability to location from either direction of rotation of a robot cylindrical coordinate system.

主权项

1. An apparatus for limiting rotation in a mechanism having θ-rotational motion about a Z-axis, the apparatus comprising:
a first member including a first magnet assembly with a first magnetic pole and a second magnetic pole; a second member including a first stop portion; a rotatable stop member including a second stop portion and a second magnet assembly with a third magnetic pole and a fourth magnetic pole; and a bearing that mounts the rotatable stop member to the second member, the bearing having a rotational drag resistance, wherein:
the rotatable stop member and the second member are configured for relative rotational movement about the Z-axis with respect to one another,the first stop portion and the second stop portion are configured to engage each other to prevent the rotatable stop member and the second member from rotating more than 360° with respect to one another,the first member and the second member are configured for relative rotational movement about the Z-axis with respect to one another, andthe first magnet assembly and the second magnet assembly are configured:
such that the first magnetic pole and the third magnetic pole have the same polarity and generate a first repulsive force when brought into non-contacting, close proximity to one another through relative rotation between the first member and the rotatable stop member about the Z-axis in a first rotational direction,such that the second magnetic pole and the fourth magnetic pole have the same polarity and generate a second repulsive force when brought into non-contacting, close proximity to one another through relative rotation between the first member and the rotatable stop member about the Z-axis in a second rotational direction opposite the first rotational direction, andthe first repulsive force and the second repulsive force are each greater than the rotational drag resistance and cause the rotatable stop member to rotate with respect to the second member without contact between the first magnet assembly and the second magnet assembly under normal operating conditions for the mechanism and absent engagement of the first stop portion and the second stop portion, wherein the rotatable stop member rotates together as a unit with the second member due to the rotational drag resistance under normal operating conditions for the mechanism and when the repulsive force between the first magnet assembly and the second magnet assembly is less than the first repulsive force or the second repulsive force.