Substrate Transport Arm With Unequal Links for Extended Reach
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Solution Overview
Problem
Traditional robot arms with equal link lengths require additional motors to increase overall arm reach, leading to higher costs and reduced performance benefits, while existing solutions with variable non-linear mechanical transmissions are complex and costly.
Innovation Solution
A substrate transport arm with unequal link lengths and a mechanical transmission system using non-circular pulleys, where the wrist joint follows a curved path while the substrate center moves along a straight path, optimizing arm reach and reducing costs by minimizing the number of components and operational volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If additional motors are added to increase overall arm reach, then arm reach is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs unequal link lengths in the SCARA arm mechanism, where the first link has a different length than the second link. This asymmetric configuration allows the arm to achieve greater overall reach within the same containment volume without requiring additional motors, thereby resolving the contradiction between improved arm reach and reduced device complexity
Solution Approach 2:
The patent modifies the geometric parameters of the SCARA arm by changing the link length ratio from the traditional equal-length configuration to an unequal-length configuration. This parameter change optimizes the arm's reach capabilities while maintaining the same number of drive shafts and motors, thus improving performance without increasing complexity
2Manufacturing precision
If variable non-linear mechanical transmission is used, then wrist path control is improved, but device complexity and cost increase
Solution Approach 1:
The unequal link lengths create an asymmetric mechanical advantage ratio between the first and second links during rotation. This asymmetry naturally produces the desired non-linear wrist path without requiring complex variable transmission mechanisms, achieving precise wrist control through simple geometric design rather than complex mechanics
Solution Approach 2:
The patent extracts the complexity from the mechanical transmission system by eliminating variable non-linear transmissions entirely. Instead, the desired wrist path control is achieved through the unequal link length geometry alone, taking out the unnecessary complex transmission components while maintaining the required control precision
3Volume of stationary object
If containment volume is reduced, then space utilization is improved, but arm reach may be limited
Solution Approach 1:
The unequal link length configuration allows the SCARA arm to achieve greater effective reach within a reduced containment volume. By optimizing the ratio between the first and second link lengths, the arm can extend further in certain directions without increasing the overall footprint or containment volume, thus resolving the contradiction between compact size and reach capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution increases overall arm reach within a given containment volume, reduces the overall height of the dual arm linkage, and lowers manufacturing and operational costs by using fewer raw materials and smaller vacuum pumps, while maintaining performance benefits.
Implementation Method 1
a mechanical transmission comprising a pulley, where the mechanical transmission is connected to the third link to control rotation of the third link on the second link
Data Source
AI summary
A substrate transport arm including a first link, a second link, a third link, and a mechanical transmission including a pulley. The third link includes an end effector configured to support a substrate thereon. The mechanical transmission is configured to control rotation of the third link on the second link as a function of an angle between the first and second links such that, as the first and second links are rotated relative to each other, the wrist joint follows a wrist path which includes a curved portion. Rotation of the third link relative to the second link is completely mechanically dependent upon rotational location of the second link on the first link. The rotation of the third link about the second link is mechanically constrained and limited by mechanical dependence based upon the function of the angle between the first and second links.