Solenoidal Magnet Outer Coil Support via Strap Elements
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Solution Overview
Problem
Conventional solenoidal magnet arrangements with shield coils face significant axial and radial forces due to magnetic interactions, leading to strain on support structures, potential coil deformation, and quenching issues, requiring large and heavy, expensive, and hard-to-manage support systems.
Innovation Solution
The use of strap elements extending around the radially inner, outer, and axially outer surfaces of outer coils, linked by tensile members to maintain concentric alignment and counteract axial forces, with flexible or rigid mounting pieces and filler materials to manage thermal and mechanical stresses, allowing for a lightweight and cost-effective support structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If large and heavy support structures are used to resist forces on outer coils, then structural stability is improved, but device complexity and cost increase
Solution Approach 1:
The support structure is segmented into multiple discrete components: journals at each end of the magnet, webs connecting journals to the former, and strap elements wrapping around the outer coils. This segmentation allows each component to be optimized independently and simplifies manufacturing and assembly compared to a monolithic heavy support structure.
Solution Approach 2:
Strap elements wrap around the outer coils like flexible bands, providing mechanical support and force distribution without requiring rigid heavy structures. The strap elements flex with coil deformation while maintaining support, reducing overall structural complexity.
2Reliability
If accurately-machined metal journals are used to support outer coils, then coil retention is improved, but manufacturing cost and supplier limitations increase
Solution Approach 1:
The journals serve multiple functions: they provide mechanical support for the outer coils, act as mounting points for strap elements, and serve as structural connection points to the former. This multi-functionality reduces the need for specialized components and simplifies manufacturing.
Solution Approach 2:
Instead of requiring uniquely machined journals from limited suppliers, the design uses standardized journal geometries that can be manufactured by multiple suppliers. The critical retention function is achieved through the strap element mechanism rather than precise journal machining, allowing greater manufacturing flexibility.
3Power
If shield coils are subjected to large magnetic forces, then magnetic field generation is improved, but coil deformation and quenching risk increase
Solution Approach 1:
The strap elements are pre-installed around the outer coils before the magnet operates under full magnetic load. These straps provide pre-positioned mechanical support that cushions the coils against the large body forces and hoop stresses that will develop during operation, preventing deformation and quenching.
Solution Approach 2:
The strap elements act as intermediary components between the outer coils and the rigid support structure (journals and webs). They mediate the force transmission, distributing magnetic forces evenly around the coil circumference and preventing localized stress concentrations that could cause deformation.
4Force
If reaction forces are borne by limited surface area at radially inner edge, then force resistance is concentrated, but coil deformation increases
Solution Approach 1:
The strap elements provide localized support at multiple circumferential positions around the outer coils, rather than concentrating support at the radially inner edge only. This distributed local support prevents deformation while maintaining effective force resistance.
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
This arrangement effectively retains shield coils in precise alignment, reduces the risk of deformation and quenching, and provides a lightweight, cost-effective, and easily sourced support system that maintains magnetic field homogeneity and accessibility for cooling, while minimizing structural loads on the magnet.
Implementation Method 1
Some of these forces, for example the force known as the body force, act axially. The body force typically urges the shield coils away from a center of the magnet
Implementation Method 2
Other forces, for example the so-called hoop stress, act radially, tending to expand the coil to a larger diameter
Implementation Method 3
The coils may be impregnated with a thermosetting resin, either by wet-winding, in which a wire is passed through a bath of resin before being wound onto the former, or the coils may be wound dry, with the completed coils and former later being impregnated in a bath of resin. The resin is then cured, and a solid coil embedded in resin is produced.
Data Source
AI summary
In a solenoidal electromagnet arrangement for a magnetic resonance imaging system, annular inner coils and annular end coils are provided, all concentrically aligned about an axis, the end coils being placed at axial extremities, axially outside of the inner coils. A pair of annular outer coils are provided concentrically aligned about the axis. An arrangement is provided retaining the pair of outer coils against an axial force urging the outer coils away from one another. The arrangement comprises strap elements which extend around a radially inner surface, a radially outer surface and an axially outer surface of each outer coil in certain circumferential locations. Each strap element on one of the outer coils is linked to a corresponding strap element on the other outer coil of the pair by a tensile member.