Safe Robotic Tool Changer With Detent Mechanism
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Solution Overview
Problem
Current robotic tool changers face safety challenges, particularly in preventing inadvertent decoupling of tools from robot arms, which can lead to dangerous failures, and require complex redundant interlock circuits and monitoring systems to meet stringent safety standards like ISO 13849 PLD.
Innovation Solution
A robotic tool changer design where the coupling mechanism requires a first source of power to move to a coupled state and a separate second source of power to move to a decoupled state, ensuring the tool can only be decoupled when returned to its tool stand, eliminating the need for redundant interlock circuits and monitoring systems by using a detent mechanism to maintain the decoupled state when not in use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant interlock circuits and monitoring systems are used to prevent inadvertent decoupling, then safety is improved, but device complexity increases
Solution Approach 1:
The patent extracts the safety function from complex electronic interlock circuits and monitoring systems, replacing it with a simple mechanical detent mechanism that passively maintains the coupled state. This removes the need for redundant electronic safety systems while achieving the same safety outcome through mechanical means.
Solution Approach 2:
The detent mechanism provides self-service safety by automatically maintaining the coupled state through its mechanical design. The spring-loaded detent ball engages with the detent surface to lock the coupling mechanism in place, providing inherent safety without requiring external monitoring or control systems.
2Device complexity
If a single power source is used for both coupling and decoupling, then device complexity is reduced, but safety is compromised due to risk of inadvertent decoupling
Solution Approach 1:
The patent segments the power sources into two distinct functions: a first power source (spring mechanism) for coupling and a second power source (pneumatic or hydraulic actuator) for decoupling. This segmentation ensures that decoupling cannot occur inadvertently since it requires a separate, controlled power source that is only activated when the tool is properly positioned in the tool stand.
Solution Approach 2:
The coupling mechanism acts as an intermediary between the two power sources, requiring both the mechanical bias from the spring and the controlled activation from the pneumatic or hydraulic actuator to achieve decoupling. This intermediary function ensures that decoupling only occurs under controlled conditions when the tool is safely positioned.
3Reliability
If complex monitoring systems are implemented to detect tool position, then safety is improved, but ease of operation deteriorates
Solution Approach 1:
The system provides self-service position detection through the mechanical interaction between the tool and tool stand. When the tool is properly positioned, the tool stand mechanically enables the second power source to actuate the coupling mechanism for decoupling. This eliminates the need for separate sensors or monitoring systems while maintaining safety.
Solution Approach 2:
The patent extracts the position detection function from electronic sensors and monitoring systems, replacing it with a purely mechanical enablement mechanism. The tool stand's mechanical structure itself serves as the position detector, enabling or disabling decoupling based on physical tool placement without requiring electronic detection.
Data Source
AI summary
In an inherently safe robotic tool changer, a master unit couples to a tool unit via a first power source, and decouples from the tool unit using a separate, second power source. The second power source is only available when an attached tool is safely disposed in a tool stand. In embodiments where the first power source is not selectively applied, such as the constant bias provided by a spring, a detent mechanism maintains the master unit in a decoupled state when the master unit is removed from the tool unit. The detent mechanism allows the master unit to couple to a different tool unit upon physically abutting the new tool unit.