Spacer Grid Welding Fixture With Opposed Engagement Bars

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Solution Overview

Problem

Existing spacer grid welding fixtures for nuclear reactor cores are difficult to machine, prone to strap misalignment, and require high removal forces, which can damage the grid and lead to tooling wear.

Innovation Solution

A spacer grid welding fixture with a frame and grid engagement bars that secure the straps by nesting into slots, allowing for precise alignment and reduced forces during welding, featuring a method of securing the assembled spacer grid with grid engagement bars on opposite sides of the frame and retaining bars to facilitate easy removal after welding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If pins are used to hold straps in position during welding, then the straps are positioned accurately, but the fixture is difficult to machine and requires high removal forces

Engineering Contradiction:

Improvestrap positioning accuracyVSAvoidfixture machining difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The fixture is divided into a frame structure with multiple slots positioned at precise locations. Each slot independently positions a strap during welding, eliminating the need for complex machined pins while maintaining positioning accuracy through the slot geometry and frame rigidity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The positioning function is extracted from complex machined pin surfaces and simplified to slot geometries that provide adequate positioning through their basic shape, reducing machining complexity while maintaining the essential positioning capability

Inventive Principle:

Principle #2Taking out (Extraction)

2Stability of the object's composition

If the entire interlocking assembly is inserted as a unit into the fixture, then positioning is maintained, but strap misalignment is difficult to detect and the assembly is prone to damage

Engineering Contradiction:

Improveassembly positioning stabilityVSAvoidstrap misalignment detection difficulty

Core Design Contradiction:

Stability of the object's compositionVSDifficulty of detecting and measuring

Solution Approach 1:

The assembly insertion process is segmented into individual strap insertion steps rather than inserting the entire assembly as one unit. Each strap is inserted separately through its own slot, allowing visual inspection and alignment verification for each strap before welding, making misalignment easily detectable and correctable

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Straps are aligned and positioned in the slots before the welding operation begins. This preliminary positioning action allows inspection of each strap's alignment with its corresponding slot and with adjacent straps, ensuring correct positioning before the welding process locks the assembly in place

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If high removal forces are applied to overcome fixture locking, then the grid can be removed from the fixture, but damage to the grid and tooling wear occur

Engineering Contradiction:

Improvegrid removal capabilityVSAvoidgrid damage and tooling wear

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The removal process is segmented into sequential steps: first breaking the welds to release the locking force, then applying minimal removal force to extract the grid. This eliminates the need for high removal forces that cause damage, as the welding sequence is designed to create progressive release points rather than simultaneous locking

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The welding sequence is designed so that welds are broken in a controlled sequence that converts the potential harmful locking effect into a beneficial progressive release mechanism. By controlling which welds remain intact and which are broken first, the fixture naturally releases the grid with minimal force after the welding process completes

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Stability of the object's composition

If grid cell pitch shrinks during welding, then the grid assembly is locked into the fixture, but high removal forces are required and tooling wear increases

Engineering Contradiction:

Improvegrid assembly stability during weldingVSAvoidfixture removal force requirement

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The welding sequence is segmented to control when and how the pitch shrinkage occurs. By scheduling welds in a specific sequence, the pitch reduction happens progressively rather than all at once, preventing sudden locking that would require high removal forces. The segmented approach allows the fixture to accommodate gradual dimensional changes

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11338398B2Spacer grid welding fixture

Publication Date: 2022.05.24 BWXT MPOWER INC

AI summary

A spacer grid welding fixture comprises a frame sized to receive an assembled spacer grid comprising a first set of parallel straps and a second set of parallel straps oriented orthogonally to the first set of parallel straps, the first and second sets of parallel straps interlocked together by slots cut into the straps. A first set of grid engagement bars is placed on a first side of the spacer grid with each grid engagement bar arranged parallel with the straps of the first set of parallel straps and engaging the straps of the second set of parallel straps. A second set of grid engagement bars is placed on an opposite second side of the spacer grid with each grid engagement bar arranged parallel with the straps of the second set of parallel straps and engaging the straps of the first set of parallel straps.