Expandable Locking Assembly for Thermal Mismatch Joints
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Solution Overview
Problem
Current attachment methods for components made of different materials, such as carbide and metal, face issues like unintended separation due to differential thermal expansion, limited temperature ranges, and structural weaknesses, leading to potential failure and inefficiencies in applications like valves.
Innovation Solution
An attachment assembly with a locking device assembly that includes a biasing element and locking elements, allowing the assembly to expand or compress to accommodate dimensional changes, ensuring secure coupling even with different coefficients of thermal expansion, using a circular biasing element and arcuate segments forming an expandable ring, and optionally canted coil springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shrink-fit attachment is used to attach carbide to metal, then the carbide component is held securely under compression, but the assembly has limited temperature range due to differential thermal expansion
Solution Approach 1:
The attachment assembly is segmented into multiple functional components: an expandable ring with multiple arcuate segments, biasing elements, and locking elements. This segmentation allows each component to perform a specific function while collectively accommodating thermal expansion differences between carbide and metal materials across a wide temperature range.
Solution Approach 2:
The attachment assembly transitions from a static interference fit to a dynamic system with movable locking elements and biasing elements. The locking elements can move radially to maintain engagement during thermal expansion and contraction, enabling the assembly to operate securely across extended temperature ranges while maintaining attachment strength.
2Ease of manufacture
If epoxy attachment is used to attach carbide to metal, then the components are bonded together, but the glue joint fails during temperature changes due to different coefficients of thermal expansion
Solution Approach 1:
The attachment assembly introduces mechanical intermediaries (locking elements, biasing elements, and the expandable ring structure) between the carbide and metal components. These intermediaries mechanically accommodate differential thermal expansion through controlled movement and deformation, replacing the chemical bonding of epoxy with a mechanical system designed to handle thermal stress, thereby improving joint reliability under temperature changes.
3Strength
If threaded collar or draw-bolt attachment is used, then the carbide component is secured to the metal shaft, but the assembly creates a bulky joint that is too large for available space
Solution Approach 1:
The attachment assembly employs a nested structure where the expandable ring with arcuate segments fits within the existing interface between carbide and metal components. The locking elements and biasing elements are nested within the ring structure, allowing the entire attachment mechanism to occupy minimal space while maintaining secure attachment, thus reducing joint size compared to external threaded collars or draw-bolts.
4Stability of the object's composition
If ball-bearing locking or garter spring latching is used, then the components are locked together, but the assembly relies on soft seals that cannot handle pressure requirements
Solution Approach 1:
The attachment assembly replaces soft seal-based locking mechanisms with a hardened mechanical locking system. The locking elements are designed with precise geometric features that replicate and enhance the locking function of ball-bearing or garter spring systems, while being made from pressure-resistant materials capable of withstanding high service pressures without relying on soft seals.
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 effectively prevents unintended separation and accommodates non-linear dimensional changes, ensuring reliable and secure attachment across varying temperatures, reducing the risk of failure and improving operational parameters.
Implementation Method 1
The attachment of components made from two different materials will involve a differing (e.g., without limitation, non-linear) change of dimensions of the two components over a range of temperatures due to differential coefficients of thermal expansion between the different materials.
Implementation Method 2
a locking device assembly structured to move between an unlocked position corresponding to the second component being attachable to, and removable from, the first component and a locked position corresponding to the second component being securely coupled to the first component
Data Source
AI summary
An attachment assembly includes a first component, a second component, and a locking device assembly. The locking device assembly is structured to move between an unlocked position corresponding to the second component being attachable to, and removable from, the first component and a locked position corresponding to the second component being securely coupled to the first component.