Cold Metal Lock and Stitching Pin Repair for Crack-Stopping Castings
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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 adhesive bonding materials are not effective in withstanding high stress loads, and prior cold metal repair systems fail to securely draw casting portions together to prevent crack spreading.
Innovation Solution
A cold metal repair apparatus and method using elongate metal locks with overlapping circular lobes and stitching pins with a conical shoulder and variable pitch double hook thread pattern, which form a lock receiving recess and provide a strong, liquid-tight, gas-tight seal without heat, ensuring the casting portions are securely drawn together to prevent crack spreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding or brazing is used to repair cracked cast metal components, then the repair can withstand high stress loads, but the heat introduced 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 cold metal repair system. Metal locks with lobes and stitching pins with threaded shafts are inserted into drilled holes to mechanically secure cracked casting portions together without introducing heat, thereby avoiding thermal damage to the metal structure while maintaining repair strength
Solution Approach 2:
The patent introduces intermediary components (metal locks and stitching pins) that mediate between the cracked casting portions. These intermediaries mechanically connect the separated metal surfaces through friction and threading, providing a heat-free joining mechanism that preserves the original metal structure
2Object-affected harmful factors
If adhesive bonding materials are used for cold metal repair, then heat damage is avoided, but the repair cannot withstand high stress loads
Solution Approach 1:
The patent employs a composite repair system combining multiple materials and mechanisms: metal locks with friction-fit lobes, threaded stitching pins, and sealant compounds. This composite approach creates a mechanically robust repair capable of withstanding high stress loads while maintaining the cold repair advantage of avoiding heat damage
3Object-affected harmful factors
If conventional cold metal repair systems are used, then heat damage is avoided, but the casting portions are not securely drawn together to prevent crack spreading
Solution Approach 1:
The patent applies preliminary action by first inserting metal locks into drilled holes transverse to the crack, which draw the casting portions together before the crack can spread. The friction-fit lobes of the metal locks create immediate compressive force on the crack surfaces, securing the portions together in advance of final stitching pin installation
Solution Approach 2:
The patent utilizes spheroidality through the circular lobes on the metal locks and the spherical contact surfaces created by the stitching pins. These curved surfaces distribute stress evenly and create high-friction contact areas that securely hold the casting portions together, preventing crack spreading through optimized geometric contact
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 providing a secure, high-friction fit that prevents crack spreading and misalignment, achieving a stronger repair than prior systems by maximizing metal-to-metal contact and distributing stress evenly, thus enhancing the overall strength of the casting.
Implementation Method 1
The stitching pin has a conical shoulder and a variable pitch double hook thread pattern... providing a secure, high-friction fit that prevents crack spreading and misalignment
Implementation Method 2
A plurality of stitching pins are inserted into the cracked casting material... the threaded shaft facilitates threading the stitching pin into the correspondingly tapped bore
Implementation Method 3
The metal lock is formed of an elongated rigid member having a plurality of lobes formed from adjacent portions thereof... providing a secure, high-friction fit that prevents crack spreading and misalignment
Implementation Method 4
achieving a stronger repair than prior systems by maximizing metal-to-metal contact and distributing stress evenly
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.