EPB Shield Machine Independent Cutting Member Rotation
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Solution Overview
Problem
Existing earth pressure balance shield machines with disc cutter arrangements have low cutting efficiency due to low linear velocity of cutting members and uneven wear rates, leading to inefficient operation and frequent replacements, and face challenges in controlling direction and adapting to non-circular tunnel cross-sections.
Innovation Solution
An earth pressure balance shield machine without a disc cutter arrangement, featuring independently rotating cutting members, a power transmission unit with a transfer case, reducer, and driving motor, and a matrix arrangement for cutting units, allowing for balanced rotation and adaptable cutting paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a disc cutter arrangement is used in the cutting system, then the shield machine can perform cutting operations, but the linear velocity of cutting members is very low which limits cutting efficiency
Solution Approach 1:
The cutting members are designed to perform active rotation in addition to moving with the cutterhead, transforming the static cutting system into a dynamic one. This active rotation significantly increases the linear velocity of cutting members, thereby improving cutting efficiency while maintaining the ability to perform effective cutting operations
Solution Approach 2:
The cutting system is segmented into multiple independently rotatable cutting members rather than relying on a single disc cutter. Each cutting member can rotate actively, allowing for optimized cutting velocity and efficiency. This segmentation also enables different cutting members to have optimized positions for specific cutting requirements
2Adaptability or versatility
If different cutting members are positioned at varied locations on the cutterhead, then cutting coverage is improved, but the linear velocity of cutting varies greatly leading to uneven operating life
Solution Approach 1:
Each cutting member is equipped with active rotation capability, allowing them to dynamically adjust their cutting velocity. This dynamic rotation compensates for position variations on the cutterhead, ensuring that all cutting members operate at optimized velocities regardless of their location, thereby achieving uniform operating life across all cutting members
Solution Approach 2:
The rotation speed parameter of each cutting member can be independently controlled and optimized based on its position and cutting requirements. By adjusting this parameter, the system achieves both comprehensive cutting coverage and uniform operating life, resolving the contradiction between adaptability and durability
3Productivity
If the cutterhead rotates at very low speed, then earth pressure balance is maintained, but the cutting efficiency is limited
Solution Approach 1:
The system introduces active rotation of cutting members independent of the cutterhead rotation. This allows the cutterhead to maintain low rotation speed for earth pressure balance while the cutting members themselves rotate at higher speeds to achieve efficient cutting, effectively decoupling these two speed requirements
Solution Approach 2:
The cutting function is segmented from the cutterhead rotation function. Multiple independently rotatable cutting members perform the actual cutting at high linear velocity, while the cutterhead maintains slow rotation to preserve earth pressure balance. This functional segmentation resolves the contradiction between productivity and speed control
Data Source
AI summary
An EPB shield machine without disc cutter, which includes a partition unit formed by a moveable partition member (30) and a stationary partition member (31), a front shield unit (13) including a cutting unit (1) with cutting head (11) and cutting teeth (12), a shaft member (2) connected to the cutting head (11) and a power transmission unit formed by a transfer case (5), a reducer (6) and a driving motor (7). In the power transmission unit at an upper portion of the machine, the transfer case (5) is fixedly to the moveable partition member (30), a sliding arrangement supports the reducer (6) and the driving motor (7), which are connected to the transfer case (5, and a telescopic cylinder (26) is connected to the sliding arrangement. The machine has advantages of high cutting efficiency, balanced service life, high directional construability and high adaptability to tunnel cross section.