Set Back Toothed Cutter Disc for TBM
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Solution Overview
Problem
Tunnel boring machines (TBMs) face issues with cutter assembly loss due to insufficient frictional contact in soft ground conditions, leading to costly and dangerous repairs, as conventional cutter rings may stop rotating or wear preferentially, resulting in operational inefficiencies and downtime.
Innovation Solution
The development of a cutter disc with set back annular toothed portions and integral hub portions, formed from tool steel, which provides enhanced structural support and traction, ensuring continuous rotation and improved wear uniformity across varied geological conditions, including soft soils and hard rocks, by utilizing a thermal interference fit and split locking mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cutter rings are used in soft ground conditions, then the TBM can maintain structural integrity, but the cutter assemblies stop rotating or wear preferentially, causing assembly loss and operational inefficiency
Solution Approach 1:
The cutter disc is divided into multiple functional segments: a central hub portion for mounting, annular toothed portions for engagement with the ground, and a continuous cutter edge portion for cutting. This segmentation allows each part to perform its specific function optimally while maintaining overall structural integrity and rotational stability in soft ground conditions
Solution Approach 2:
Different portions of the cutter disc have different structural characteristics tailored to their specific functions. The toothed portions are designed with specific geometry for engagement, the cutter edge portion has optimized dimensions for cutting, and the hub portion provides rotational support. This local differentiation prevents preferential wear and ensures uniform performance across varied geological conditions
2Stress or pressure
If the cutter disc uses a narrow continuous cutter edge portion to increase stress concentration, then rock fracturing improves, but structural strength under extreme load conditions decreases
Solution Approach 1:
The cutter disc structure is segmented into the continuous cutter edge portion and the annular toothed portions, which act as structural reinforcements. This segmentation allows the thin cutter edge to concentrate stress effectively while the toothed portions provide structural support to prevent failure under extreme loads
Solution Approach 2:
The cutter disc is formed from tool steel, a material selected for its combination of hardness and strength. This material choice allows the design to achieve both high stress concentration capability through the narrow cutter edge and sufficient structural integrity through the reinforced toothed portions and hub
3Productivity
If the cutter disc rotates using frictional contact with the ground, then cutting action is maintained, but insufficient friction in soft ground causes the disc to stop rotating or wear preferentially
Solution Approach 1:
The cutter disc incorporates multiple engagement features: the continuous cutter edge portion for cutting and the annular toothed portions for providing traction. This segmentation ensures that even if one feature is less effective in certain ground conditions, the other can compensate, maintaining continuous rotation and preventing preferential wear
Solution Approach 2:
The cutter disc is designed to adapt dynamically to varying ground conditions. The toothed portions can engage with soft ground to provide necessary friction for rotation, while the continuous cutter edge maintains cutting action. This dynamic adaptation ensures rotational stability across diverse geological conditions without requiring preferential wear of any single feature
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 improved cutter disc design enhances rotational stability and structural integrity, reducing the likelihood of assembly loss and wear imbalances, thereby increasing operational efficiency and reducing maintenance costs by maintaining consistent performance across diverse ground conditions.
Implementation Method 1
The improved cutter disc design enhances rotational stability and structural integrity, reducing the likelihood of assembly loss and wear imbalances
Data Source
AI summary
A cutter disc for a tunnel boring machine includes a middle disc portion defining a radially outer surface or edge for engaging a surface, a left toothed portion defining a first set of teeth set back from the outer edge, and a right toothed portion defining a second set of teeth set back from the outer edge. In an embodiment, a central bore through the cutter disc is configured to attach the cutter disc to a hub for rotatably mounting the cutter disc on a shaft. In an embodiment, the hub is formed integrally with the cutter disc. The left and right toothed portions provide structural support to the middle portion and facilitate rotation of the cutter disc when boring in soft or mixed conditions, but do not interfere with boring in hard rock conditions.