Holding Fixture with Cam Assemblies for Nuclear Fuel Rod Grid Assembly
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Solution Overview
Problem
The assembly of conventional support grids for nuclear fuel rods is labor intensive, error prone, and costly due to the tight tolerances of the corresponding slots in the upper and lower straps, making it difficult to properly align and mate the straps, especially when trying to automate the process.
Innovation Solution
A holding fixture pair is introduced, comprising upper and lower holding fixtures with cam assemblies that deflect every other tab of the straps, allowing for alignment and mating even with some misalignment, and are adjustable to facilitate assembly and disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional assembly methods are used for support grids, then the structure maintains high manufacturing precision through tight tolerances, but the assembly process becomes labor intensive and difficult to automate
Solution Approach 1:
The patent introduces holding fixtures as intermediary devices that temporarily hold straps in the correct position during assembly. These fixtures include alignment features and positioning mechanisms that guide the straps into proper alignment, eliminating the need for highly precise manual alignment while maintaining the required manufacturing precision of the final assembly.
Solution Approach 2:
The holding fixtures perform preliminary alignment and positioning actions before the final assembly is complete. By pre-positioning the straps using the fixture's alignment features, the system prepares the components in advance, making the actual assembly process faster and easier to automate without compromising the tight tolerance requirements.
2Manufacturing precision
If tight tolerances are maintained for slot alignment, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The holding fixtures serve as intermediary devices that absorb the complexity of achieving tight tolerances. Instead of requiring the straps and slots themselves to be extremely precise, the fixtures provide the necessary alignment and positioning, thereby reducing the manufacturing complexity while maintaining the required precision in the final assembly.
Solution Approach 2:
The assembly system is segmented into two functional parts: the holding fixtures that handle alignment and positioning, and the support grid components that focus on structural function. This segmentation allows each part to be optimized independently, reducing overall device complexity while maintaining manufacturing precision where needed.
3Manufacturing precision
If manual assembly is used to achieve proper alignment, then manufacturing precision is maintained, but labor costs and error rates increase
Solution Approach 1:
The holding fixtures act as intermediaries that guide and constrain the straps during assembly, ensuring proper alignment without requiring skilled manual manipulation. The fixtures incorporate alignment features that automatically position the straps correctly, reducing labor intensity and minimizing human error while maintaining the precision required for proper strap mating.
Solution Approach 2:
The holding fixtures are designed to self-align and self-position the straps through built-in alignment features and positioning mechanisms. This self-service capability reduces the need for complex manual operations and skilled labor, making the assembly process easier to perform and more consistent, thereby reducing both labor costs and error rates.
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 holding fixtures enable simultaneous mating of multiple straps, reducing labor, costs, and errors associated with assembling support grids for nuclear fuel rods by accommodating misalignment and providing a more efficient assembly process.
Implementation Method 1
a plurality of cam assemblies (22) structured to move to deflect every other tab (7) of the straps (2, 4) received in the plurality of receiving members (38)
Data Source
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AI summary
A holding fixture for assisting in assembly of a support grid for nuclear fuel rods and including a plurality of straps each having a plurality of slots extending approximately half a height of the straps and tabs formed beside or between the slots. The holding fixture includes an actuation plate, a support plate having a plurality of receiving members structured to receive therein straps of the support grid and having a plurality of cells, and a plurality of cam assemblies structured to move to deflect every other tab of the straps received in the plurality of receiving members. The cam assemblies are disposed in every other cell of the support plate.