Robot Wrist Joint Structure with Annular Cable Routing
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Solution Overview
Problem
In vertically articulated robots, the exposure of cables from the base to the hand interface can obstruct operations, and as robots shrink, routing these cables becomes challenging due to fixed cable thickness, leading to increased interference and reduced durability from bending with small radii of curvature.
Innovation Solution
A robot joint structure with wrist supporting portions on both sides of the arm, where motors are positioned on the base side, and pulleys transmit rotation to separate wrist and hand driving mechanisms, allowing cables to route internally through a wrist housing with a cylindrical portion and annular gap, reducing curvature and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the wrist drive mechanism and hand drive mechanism are arranged on the same side, then the structure is simplified, but the interference prevention area increases significantly
Solution Approach 1:
The patent divides the drive mechanisms into two separate sides: the wrist drive mechanism is arranged on one side while the hand drive mechanism is arranged on the other side. This segmentation allows both mechanisms to be positioned symmetrically relative to the arm center, reducing the overall interference prevention area while maintaining functional independence of each drive system
Solution Approach 2:
The patent employs asymmetric arrangement by placing different drive mechanisms on opposite sides of the arm rather than clustering them on one side. This asymmetric distribution balances the spatial requirements and reduces the maximum distance from the arm center, thereby minimizing the interference prevention area
2Volume of moving object
If the robot size is reduced, then the robot becomes more compact, but the cable routing space in the wrist becomes insufficient
Solution Approach 1:
The patent utilizes the annular gap between the cylindrical portion and the wrist housing as a three-dimensional cable routing path. By employing this annular space rather than linear pathways, the cable can be routed efficiently within the limited wrist volume, accommodating compact robot design while maintaining adequate cable routing space
Solution Approach 2:
The cable is nested within the annular gap formed by the cylindrical portion and wrist housing. This nesting arrangement allows the cable to occupy the available space efficiently within the wrist assembly, enabling compact robot design without compromising cable routing requirements
3Length of stationary object
If the cable is bent with a small radius of curvature in the wrist, then the cable routing path is shortened, but the cable is easily broken and durability decreases
Solution Approach 1:
The patent employs an annular gap with a curved cross-section between the cylindrical portion and wrist housing for cable routing. This curved pathway allows the cable to follow a gentle arc rather than a sharp bend, maintaining adequate bending radius while keeping the cable routing path compact and efficient
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
This design minimizes the interference area around the arm, enhances cable durability, and allows for smaller robot designs by reducing the need for tight cable bends, thus improving the robot's operational space and longevity.
Implementation Method 1
a wrist driving pulley that is arranged in one of the pair of wrist supporting portions and to which rotation of the wrist driving motor is transmitted, and a hand driving pulley that is arranged in another of the pair of wrist supporting portions such that it is coaxial with the wrist driving pulley and to which rotation of the hand driving motor is transmitted
Data Source
AI summary
A wrist includes a wrist housing including a wrist driving structural portion to which rotation is transmitted from a wrist driving pulley, a cylindrical portion arranged coaxially with a rotational axis of the wrist driving structural portion and penetrated by a first hand driving shaft to which rotation is transmitted from a hand driving pulley, a cable introducing portion forming an annular gap with the cylindrical portion, and a hand-driving-shaft penetrating portion penetrated by a second hand driving shaft rotating a hand interface by rotation of the first hand driving shaft being transmitted thereto, and a cable, which comes out of a second arm from a wrist supporting portion, is drawn into the wrist housing from the annular gap and is routed to a hand interface supporting portion in a slackened state.