Pressure-Compensated Cutter Assembly for Tunnel Boring Machines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Tunnel boring machines (TBMs) face challenges in preventing the incursion of dirt and foreign matter into cutter assemblies under high hydrostatic pressures, leading to potential seizure and maintenance issues.
Innovation Solution
A pressure-compensated cutter assembly with a shaft, cutter ring assembly, and end retainers featuring a movable piston portion and rotary seal groups, where the lubricant pressure is increased to minimize the pressure differential between external hydrostatic pressure and internal lubricant pressure, using duo-cone seals and pressure ports to maintain effective sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cutter assemblies with fixed bearings are used, then the structure is simple, but the cutter head cannot maintain constant contact with the tunnel wall under varying ground conditions, reducing manufacturing precision and reliability
Solution Approach 1:
The patent applies dynamics by replacing fixed bearings with a dynamic support system where cutters are mounted on movable arms that can adjust their position. The arms are supported by bearings allowing rotational movement, enabling the cutter head to dynamically adapt to varying ground conditions while maintaining constant contact with the tunnel wall. This dynamic configuration resolves the contradiction between reliability and device complexity.
Solution Approach 2:
The patent implements parameter changes by allowing the radial position of cutters to vary through the movable arm mechanism. The bearing-supported arms enable changes in the radial parameter of cutter position, allowing adaptation to different ground conditions and tunnel wall distances. This parameter variability maintains reliable contact while managing structural complexity through controlled movement degrees.
2Manufacturing precision
If cutters are fixed rigidly to the cutter head, then the structure is simple, but the cutters cannot adapt to varying radial distances from the tunnel axis, reducing manufacturing precision
Solution Approach 1:
The patent applies dynamics by replacing fixed rigid mounting with a dynamic movable arm mechanism. Each cutter is mounted on an arm that can rotate about a bearing, enabling the cutter's radial position to change dynamically. This allows precise adaptation to varying distances from the tunnel axis, improving manufacturing precision of the tunnel cross-section while managing complexity through standardized bearing-supported joints.
Solution Approach 2:
The patent applies segmentation by dividing the cutter head into modular components: individual movable arms, each supporting a cutter, with bearings at joint locations. This segmentation allows independent adjustment of each cutter's radial position, enabling precise control of the tunnel cross-section shape. The modular bearing-supported arms reduce overall system complexity through standardized, replaceable components.
3Reliability
If conventional non-pressure-compensated lubrication is used, then the system is simple, but high contact pressures cause lubricant leakage and reduced reliability
Solution Approach 1:
The patent applies pneumatics and hydraulics by implementing a pressure-compensated lubrication system that uses fluid pressure to maintain proper lubricant flow under high contact pressures. The bearing assembly includes pressure compensation mechanisms that utilize hydraulic or pneumatic principles to counterbalance the high pressures generated during tunneling operations, preventing lubricant leakage and maintaining reliable lubrication without excessive system complexity.
4Adaptability or versatility
If cutters are allowed to move freely to adapt to ground conditions, then adaptability is improved, but control over cutter position and tunnel shape becomes difficult, reducing manufacturing precision
Solution Approach 1:
The patent applies parameter changes by enabling controlled variation of the radial position parameter of cutters through the movable arm mechanism. The bearings allow the radial distance parameter to change in response to ground conditions, providing adaptability. Simultaneously, the controlled nature of this parameter change through the mechanical arm structure maintains manufacturing precision of the tunnel cross-section, resolving the contradiction between adaptability and precision.
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 prevents foreign matter incursion into the bearing assemblies, reducing the risk of cutter assembly failure and extending maintenance intervals by maintaining a small pressure differential and ensuring reliable operation under high hydrostatic conditions.
Implementation Method 1
a bearing between the arm and the cutter head, wherein the bearing is configured to compensate for radial displacements of the cutter
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A pressure-compensated cutter assembly for a tunnel boring machine includes a shaft a cutter ring assembly rotatably mounted on the shaft, and first and second end retainers non-rotatably attached to the shaft. Rotary seal groups, immersed in lubricant, provide a moving seal between the rotating cutter ring assembly and the end retainers. A movable piston member is exposed to ambient pressures, and contacts the lubricant, such that increasing ambient pressure will increase the lubricant pressure, thereby keeping the pressure differential across the seal small. In one embodiment, the piston is a floating retainer portion. In another embodiment, the piston is an annular piston, and in another embodiment, the piston is a plurality of smaller pistons disposed in the first retainer.