Cold Metal Lock and Pin Repair for Leak-Tight Crack Sealing
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Solution Overview
Problem
Existing methods for repairing damaged cast metal components, such as welding and brazing, introduce heat that alters the metal structure and weakens the casting, while cold metal repair techniques like stitching pins and lacing plugs often fail to provide a strong, leak-tight seal and can spread the crack, limiting the repair's effectiveness.
Innovation Solution
A cold metal repair apparatus featuring elongate metal locks with overlapping circular lobes and stitching pins with a conical shoulder and variable pitch double hook thread pattern, which are inserted into lock receiving recesses and threaded bores to provide a strong, interference fit that prevents crack spreading and creates a liquid-tight/gas-tight seal without heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding or brazing is used to repair cracked castings, then the repair can withstand high stress loads, but the heat alters the metal structure and creates discontinuities that weaken the casting strength
Solution Approach 1:
The patent replaces thermal joining processes (welding/brazing) with a mechanical fastening system consisting of metal locks and stitching pins. The metal locks are inserted into drilled holes transverse to the crack, and stitching pins are threaded along the crack, using mechanical interlocking and friction rather than heat to achieve repair strength.
Solution Approach 2:
The patent introduces intermediary components (metal locks and stitching pins) between the cracked casting portions. These intermediaries mechanically bridge the crack by being inserted into the metal and tightened, distributing stress and preventing crack propagation without directly heating the base metal.
2Object-affected harmful factors
If conventional stitching pins or lacing plugs are used for cold metal repair, then heat damage is avoided, but the repair often fails to provide a strong, leak-tight seal and can spread the crack
Solution Approach 1:
The patent applies local quality by creating lock receiving recesses with specific geometric features (narrowest width, widest width, intermediate width portions) that correspond to different portions of the metal lock. This varying geometry creates localized interference fits at different positions, enhancing the mechanical interlocking and preventing crack spreading while maintaining leak-tight seals.
Solution Approach 2:
The patent employs curved and rounded geometric features including circular lobes on the metal lock, arc-shaped friction surfaces, and rounded transitions in the lock receiving recess. These curved features distribute stress more evenly and create better contact surfaces for mechanical interlocking compared to sharp or flat geometries.
3Ease of manufacture
If metal locks with simple geometry are used, then manufacturing is easier, but the interference fit and stress distribution are insufficient to prevent crack spreading
Solution Approach 1:
The metal lock features locally varied geometry with circular lobes of different sizes positioned at specific locations. The larger circular lobes provide primary interference fit in certain regions while smaller lobes provide secondary anchoring in other regions, creating differentiated local qualities that optimize both manufacturing feasibility and mechanical performance.
Solution Approach 2:
The metal lock can be formed from composite materials or multi-phase metal structures that combine different material properties in different regions. This allows optimization of local areas for different functions such as interference fit, stress distribution, and fracture resistance while maintaining overall structural integrity.
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 strengthens the repair by drawing the casting portions together, preventing crack spreading and misalignment, and achieving a robust, leak-tight seal, enhancing the overall strength and durability of the repair.
Implementation Method 1
The stitching pin has a conical shoulder and variable pitch double hook thread pattern, which are inserted into lock receiving recesses and threaded bores to provide a strong, interference fit
Implementation Method 2
The variable pitch double hook thread pattern creates mechanical interlocking with the threaded bore to prevent crack spreading and provide a leak-tight seal
Implementation Method 3
elongate metal locks with overlapping circular lobes... inserted into lock receiving recesses... to provide a strong, interference fit that prevents crack spreading
Data Source
AI summary
A lock and pin for the structural and fluid tight repair of cracks not amenable to high temperature repairs or synthetic material patches. Fluid tight pins and locks seal the crack while one or more locks prevent the crack from growing. These repairs need to endure the remaining life cycle of the machinery part while withstanding all the strain, pressure, heat and expansion and contraction of the part before the crack(s) were formed. Often these cracks evolved due to engineering design flaws that will require even greater strength from these areas than when new.