Pneumatic Valve Leaf Spring Actuation for SMA Service Life
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Solution Overview
Problem
Pneumatic valves using shape memory alloy (SMA) elements face limitations in achieving a long service life due to the need for significant contraction during actuation, which can lead to mechanical stress and reduced lifespan, and existing solutions do not effectively convert the SMA wire contraction into a larger valve stroke without compromising reliability and compactness.
Innovation Solution
The pneumatic valve incorporates a leaf spring mechanism that is rotationally fixed to the valve housing, converting the SMA element's deformation into a larger valve flap stroke through elastic bending, allowing for a compact design and increased service life by requiring smaller deformations of the SMA element, with a lever arrangement that diverts the stroke angle between 50° and 130°, particularly 90°, and optional features like a separate resetting spring or conductive portions for end position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If SMA element contraction is increased to achieve larger valve stroke, then valve actuation capability is improved, but SMA element service life deteriorates due to mechanical stress
Solution Approach 1:
A leaf spring is introduced as an intermediary mechanism between the SMA element and the valve flap. The leaf spring converts the small contraction of the SMA element into a larger stroke of the valve flap through elastic bending, thereby achieving the desired valve actuation without subjecting the SMA element to excessive mechanical stress
Solution Approach 2:
The system changes the physical state of the leaf spring from a rigid structure to an elastic bending structure. By utilizing the elastic properties of the leaf spring, the system transforms the small displacement of the SMA element into a larger displacement of the valve flap, resolving the contradiction between stroke size and SMA element stress
2Device complexity
If hinge connections are used to convert SMA wire stroke into valve flap movement, then actuation mechanism is simplified, but reliability deteriorates due to play and wear
Solution Approach 1:
The hinge connection is completely removed from the actuation mechanism. Instead of using a hinge to connect the valve flap to the actuating element, the patent employs a leaf spring that is directly fastened to the valve housing, eliminating the source of play and wear while maintaining mechanism simplicity
Solution Approach 2:
The functions of the hinge connection and the stroke conversion mechanism are merged into a single integrated leaf spring structure. The leaf spring serves both as the mounting connection and as the stroke conversion element, eliminating the need for separate hinge components and reducing potential failure points
3Reliability
If valve flap is firmly attached to valve seat for sealing, then sealing performance is improved, but actuation reliability deteriorates due to adhesion
Solution Approach 1:
The rapid elastic bending of the leaf spring during actuation creates a dynamic peeling motion that generates sufficient force to overcome adhesion between the valve flap and seat. This mechanical vibration effect ensures reliable detachment while maintaining sealing contact during the closed position
Solution Approach 2:
The system transitions from a static attachment model to a dynamic peeling model. The leaf spring's elastic bending creates a dynamic peeling motion that effectively detaches the valve flap from the seat during actuation, overcoming adhesion forces that would prevent reliable opening
4Ease of manufacture
If leaf spring is fastened with hinge to valve housing, then installation is simplified, but actuation reliability deteriorates due to play
Solution Approach 1:
The hinge connection in the leaf spring mounting system is removed entirely. The leaf spring is directly fastened to the valve housing using alternative mounting methods such as adhesive bonding, rivets, or integral formation, eliminating the play and wear associated with hinge connections while maintaining ease of installation through simplified assembly steps
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 solution enhances the service life of SMA elements by reducing the required deformation, ensures reliable actuation with a peeling movement to detach the valve flap from the seat, and maintains a compact construction while protecting sensitive components from air and moisture.
Implementation Method 1
The SMA element deforms as a result of a supply of an electrical heating current
Implementation Method 2
the SMA element deforms as a result of a supply of an electrical heating current, whereby a predefined movement of the valve flap is effected
Implementation Method 3
The valve flap with the leaf spring interacts with the SMA element such that a stroke of the SMA element caused by the deformation thereof is converted into a stroke of the valve flap by means of elastic bending of the spring leaf of the leaf spring
Data Source
AI summary
A pneumatic valve, including a valve housing with an air chamber with one or more air ports. A respective air port of at least one of the air ports can be opened and closed by a movable valve flap which is mechanically coupled to a shape memory alloy. The SMA element deforms as a result of supplying electrical heating current and effects a predefined movement of the valve flap for opening or closing the respective air port. The deformation of the SMA element is reversed when the supply of the electrical heating current ends. The valve flap has a leaf spring. The leaf spring is held rotationally fixedly relative to the valve housing. The leaf spring interacts with the SMA element such that a stroke of the SMA element caused by the deformation is converted into a stroke of the valve flap by elastic bending of the leaf spring.