Helical X-ray Cathode Filament Assembly with Precision Fixture
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Solution Overview
Problem
The existing assembly methods for X-ray tube cathodes lack precision and accuracy, leading to potential misalignment and changes in the focal spot of the X-ray beam during operation.
Innovation Solution
A cathode design featuring a helical filament with a support structure and a filament frame structure for electron-optical focusing, which includes positioning devices and a metallic coating on a ceramic cathode cup, facilitating precise alignment and assembly by holding the filament in place and allowing for external recrystallization to reduce deformation and thermal drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual adjustment is used for filament positioning during cathode assembly, then the assembly process is simple, but the positioning precision and alignment accuracy are insufficient
Solution Approach 1:
The patent applies preliminary action by providing a fixture with a mandril that pre-positions the filament in the correct orientation and location before final assembly. The mandril is inserted into the cathode cup and the filament is mounted onto it, ensuring correct positioning is established beforehand. This preliminary positioning action eliminates the need for complex adjustment mechanisms during final assembly, resolving the contradiction between positioning precision and device complexity.
Solution Approach 2:
The patent uses an intermediary approach by introducing a fixture as a mediating device between the filament and the cathode cup. The fixture includes a mandril that acts as an intermediate tool to transfer the filament from the mounting tool to the cathode cup in the correct position. This intermediary fixture simplifies the overall assembly process while ensuring high positioning precision, without requiring complex alignment mechanisms.
2Manufacturing precision
If the filament is secured in the cathode cup cavities, then the filament is fixed, but the final position alignment in the electron emitting direction may still be imprecise
Solution Approach 1:
The patent replaces the traditional mechanical alignment system with a precision fixture system. Instead of relying on manual mechanical adjustment of the filament position in the cathode cup, the invention uses a specially designed fixture with a mandril that mechanically guides and positions the filament with high precision during assembly. This substitution of the alignment mechanism resolves the contradiction by providing precise alignment through the fixture's built-in geometry rather than through ease-of-operation manual adjustment.
3Reliability
If the filament operates at high temperature, then electron emission is sufficient, but thermal drift causes focal spot changes
Solution Approach 1:
The patent applies parameter changes by modifying the physical and chemical properties of the filament through controlled heat treatment processes. The filament undergoes recrystallization and aging treatments that change its microstructure and thermal expansion characteristics. These parameter changes in the filament's material properties reduce thermal drift at operating temperatures, thereby stabilizing the focal spot position while maintaining the necessary high temperature for electron emission.
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 design enhances the precision and stability of the X-ray tube assembly, reducing the need for manual adjustments and minimizing thermal drift, resulting in improved focal spot stability and extended filament lifetime.
Implementation Method 1
a filament (12) provided to emit electrons towards an anode in an electron emitting direction
Implementation Method 2
The filament frame structure (18) is provided for electron-optical focusing of the emitted electrons
Implementation Method 3
the filament may be exposed to externally applied heat, e.g. in an oven or furnace. As an example for applying heat, an enclosing of the filament is provided, which structure is heated up by induction
Data Source
AI summary
A cathode for an X-ray tube, an X-ray tube, a system for X-ray imaging, and a method for an assembly of a cathode for an X-ray tube include a filament, a support structure, a body structure, and a filament frame structure. The filament is provided to emit electrons towards an anode in an electron emitting direction, and the filament at least partially includes a helical structure. Further, the filament is held by the support structure which is fixedly connected to the body structure. The filament frame structure is provided for electron-optical focusing of the emitted electrons, and the filament frame structure is provided adjacent to the outer boundaries of the filament. The filament frame structure includes frame surface portions arranged transverse to the emitting direction, and the filament frame structure is held by the support structure.