Shape Memory Wire Actuator with Magnetic Decoupling
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Solution Overview
Problem
Shape memory wires used in actuators face limitations due to excessive stress when subjected to constant or increasing loads during contraction, limiting their application in certain fields.
Innovation Solution
An actuator design that incorporates shape memory wires with a magnetic force generator to reduce the load on the wires during contraction and at the end of their stroke, allowing for more efficient use of their properties by decoupling the valve stem from the wires and using magnetic forces to latch and move the valve stem independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If shape memory wires are used to actuate the valve stem, then the valve size, weight and cost are reduced, but the wires are subjected to excessive stress during contraction which limits their application
Solution Approach 1:
A magnetic field is introduced as an intermediary force between the shape memory wire and the valve stem. The magnetic field generator creates magnetic forces that assist the shape memory wire in moving the valve stem, thereby reducing the load and stress on the wire during actuation while maintaining the desired valve control functionality
Solution Approach 2:
The patent replaces part of the mechanical load-bearing system with a magnetic field-based actuation system. Instead of relying solely on the shape memory wire's mechanical contraction force, a magnetic field generator provides additional actuating force, substituting mechanical stress with electromagnetic interaction to reduce wire stress
2Force
If shape memory wires are subjected to constant or increasing loads during contraction, then the valve stem can be moved to the required position, but the wire size must be increased or stroke limited to prevent wire failure
Solution Approach 1:
The magnetic field acts as an intermediary that provides additional force during the wire's contraction stroke. This allows the wire to achieve the required actuation force without needing to be oversized or limited in stroke, as the magnetic field supplements the wire's mechanical force output throughout the movement
3Stress or pressure
If the valve stem is decoupled from the shape memory wire, then the load on the wire is reduced, but an additional force generator is required to move and seat the valve stem
Solution Approach 1:
The patent replaces the direct mechanical coupling system with a magnetic field-based actuation system. The magnetic field generator provides the necessary force to move and seat the valve stem without requiring direct mechanical coupling to the shape memory wire, reducing wire load while adding electromagnetic actuation 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 reduces stress on shape memory wires, enabling their use in applications where size, weight, and cost are critical, such as in valves, while maintaining their contraction properties, thus overcoming their inherent limitations.
Implementation Method 1
an actuator which selectively moves the valve stem in a direction of travel between the two positions for opening or closing the valve. The actuator includes a shape memory wire, which contracts when heated
Implementation Method 2
The actuator also includes a force generator, such as a magnetic field, which generates a magnetic force. The magnetic force acts on the valve stem and moves the valve stem in the direction of travel, and optionally independently of the shape memory wire, to the second position
Data Source
AI summary
An actuator for selectively moving a part relative to another part includes a shape memory wire, which contracts when heated. One portion of the shape memory wire is fixed to a first body, and another portion of the shape memory wire is coupled to a second body, which is movable relative to the first body. When heated the shape memory wire contracts and moves the second body in a direction of travel from a first position relative to the first body toward a second position. The actuator further includes a magnetic field for generating a magnetic force on the second body. The magnetic force acts on and moves the second body in the direction of travel to the second position after the shape memory wire initially contracts, and further decouples the second body from the shape memory wire when applying the magnetic force to the second body to thereby unload the load on the shape memory wire when the second body is moved to the second position.