Passive Robotic Arm Joint Locking With Mechanical Friction Braking
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Solution Overview
Problem
Existing joint locking mechanisms for medical robots, such as hydraulic, pneumatic, and electromagnetic systems, pose contamination risks and limited locking force, making them unsuitable for clinical use, while purely mechanical solutions are desired for their simplicity and safety.
Innovation Solution
A purely mechanical joint locking mechanism utilizing a frictional locking system with a threaded shaft, sleeve, rotary disk, end cap, and scroll spring, where the scroll spring applies rotational force to press a threaded sleeve against a friction disk for braking, and a pin limits the sleeve's movement along a guide slot to ensure reliable locking and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If hydraulic or pneumatic joint locking mechanisms are used, then locking force can be provided, but contamination is brought to the operating room
Solution Approach 1:
The patent replaces hydraulic and pneumatic systems with a purely mechanical friction-based locking mechanism. The mechanical structure uses a friction disk, brake shoe, and spring assembly to provide locking force without fluids, thereby eliminating contamination risks in the operating room environment.
Solution Approach 2:
The invention extracts and eliminates the hydraulic or pneumatic fluid systems from the joint locking mechanism, retaining only the essential mechanical components (friction disk, brake shoe, spring) needed to provide locking force, thus removing the source of contamination.
2Device complexity
If electromagnetic locking mechanisms are used, then structure is simplified, but locking force is limited
Solution Approach 1:
The patent employs a friction disk with a curved or spherical contact surface that works with a corresponding brake shoe. This curved geometry allows for increased contact area and more effective force transmission, enabling the simple mechanical structure to generate sufficient locking force without electromagnetic components.
Solution Approach 2:
The invention changes the physical parameters of the mechanical components, specifically using a spring-loaded brake shoe that applies variable friction force against the friction disk. By adjusting spring tension and friction surface properties, adequate locking force is achieved with a simple mechanical structure.
3Ease of operation
If a mechanical joint locking mechanism is designed, then simplicity and operability are improved, but reliability of locking must be ensured
Solution Approach 1:
The patent incorporates a spring-loaded brake shoe that maintains constant friction contact with the friction disk, providing continuous locking force before any load is applied. This pre-loaded mechanical spring ensures the joint remains securely locked during surgical operations without requiring active control.
Solution Approach 2:
The mechanical friction-based locking mechanism is self-actuating through the spring force applied to the brake shoe. The system automatically maintains locking force without requiring external power sources, control systems, or manual intervention during surgery, thereby ensuring both simplicity and reliability.
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 mechanical joint locking mechanism provides a safe, contamination-free, and reliable braking system for medical robots, reducing psychological pressure on surgeons and enabling effective joint locking during surgeries without the need for external power sources.
Implementation Method 1
a scroll spring generating a rotational force on the threaded shaft. The scroll spring has one end connected fixedly to the end cap and the other end connected to the rotary disk or the threaded shaft
Implementation Method 2
the threaded sleeve is pressed tightly on the friction disk, whereupon the friction disk under pressure causes the joint output shaft to be braked
Data Source
AI summary
A joint locking mechanism of a passive robotic arm includes: an output assembly, including a joint output shaft, and a friction disk fixed to the joint output shaft; a braking assembly, including a threaded shaft arranged coaxially with the joint output shaft, a threaded sleeve threaded to the threaded shaft, a rotary disk connected fixedly to the threaded shaft, an end cap rotatable relative to the rotary disk, and a scroll spring generating a rotational force on the threaded shaft. The scroll spring has one end connected fixedly to the end cap and the other end connected to the rotary disk or the threaded shaft. The threaded sleeve is abutted tightly against the friction disk.