Shape-Memory Wire Brake Assembly for Stable Emergency Actuation
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Solution Overview
Problem
Existing emergency brake assemblies for motor-driven tools using shape memory alloy actuators are unstable under compressive loading and lack a robust design for reliable, multiple-use operation.
Innovation Solution
A brake assembly design featuring a wire-shaped actuating element with a shape memory alloy, a holding structure, and a brake element, where the actuating element is drivenly coupled to the brake element, allowing for reliable movement between release and brake positions, and includes insulating elements, intermediate components, and a spring-loaded mechanism for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a wire-shaped actuating element comprising a shape memory alloy is used, then the emergency brake assembly achieves a simple and robust configuration, but the actuating element becomes unstable when subjected to compressive loading
Solution Approach 1:
The patent inverts the force direction by using a tensile-loaded wire-shaped actuator instead of a compressive-loaded rod. The shape memory alloy wire is tensioned between the brake element and holding structure, so that actuation occurs through tensile force application rather than compression, thereby achieving stability while maintaining simplicity.
Solution Approach 2:
The patent changes the mechanical parameter (force type) from compression to tension by reconfiguring the actuator assembly. The wire-shaped actuating element is pre-tensioned and arranged to apply tensile forces during braking, transforming the unstable compressive loading scenario into a stable tensile loading scenario.
2Device complexity
If the actuating element is designed to be wire-shaped for simplicity, then the configuration becomes more robust, but the element is very much longer than it is wide which may increase space requirements
Solution Approach 1:
The patent nests the wire-shaped actuating element within the existing brake assembly structure, routing it through the holding structure and around the brake element. This nesting approach allows the long wire to be accommodated within the compact brake assembly volume, reducing the overall space requirements despite the inherent length of the wire-shaped actuator.
3Device complexity
If a wire-shaped actuating element is used that can only transfer tensile forces, then the structure is simplified, but the element becomes unstable under compressive loading during operation
Solution Approach 1:
The patent inverts the force direction by using a tensile-loaded wire-shaped actuator instead of a compressive-loaded rod. The shape memory alloy wire is tensioned between the brake element and holding structure, so that actuation occurs through tensile force application rather than compression, thereby achieving stability while maintaining simplicity.
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 design ensures reliable, compact, and robust operation of the emergency brake, preventing damage and ensuring high reliability and longevity by managing tensile and compressive forces, and adapting movement for precise braking.
Implementation Method 1
actuators having actuating elements comprising a shape memory alloy can be used. The function of such actuators is based on a heat-activated lattice conversion of the shape memory alloy, which results in the length of the actuating element changing.
Data Source
AI summary
An emergency braking assembly for a motor-driven tool has a holding structure, a braking element movably mounted on the holding structure, and a wire-like actuation element, which has a shape-memory alloy. A first end of the actuation element is attached to the holding structure. A second end of the actuation element is drivingly coupled to the braking element. A method operates the emergency braking assembly. The braking element is set in motion by the actuation element and then a motion coupling between actuation element and braking element is cancelled or terminated.