Discharge Lamp Cathode With Sintered Compact Emitter Reservoir
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Solution Overview
Problem
Discharge lamps using rare earth elements as alternatives to thorium face issues with early emitter depletion due to excessive vaporization, leading to unstable lighting and shortened lamp life, especially in high-input applications.
Innovation Solution
A cathode structure with a high melting point metal main body and front end, containing a sintered compact with a higher emitter concentration than the front end, buried in a hermetically sealed space, and a pressing member to ensure contact and prevent gap formation, allowing for stable emitter diffusion and prolonged electron emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If rare earth oxide is used as an emitter alternative to thorium oxide, then radioactivity concerns are eliminated and handling restrictions are removed, but the emitter vaporizes excessively leading to early depletion and unstable lighting
Solution Approach 1:
The patent applies preliminary action by pre-forming a sintered compact containing the rare earth oxide emitter at a concentrated form before cathode operation. This sintered compact is positioned in advance within the cathode structure, creating a reservoir of emitter material that will gradually supply the front end during operation, preventing excessive vaporization from the start.
Solution Approach 2:
The patent implements nesting by placing the sintered compact containing rare earth oxide emitter inside the cathode structure. The sintered compact is nested within the cathode body, creating a hierarchical structure where the emitter reservoir is contained within the electrode assembly, allowing controlled release of emitter material.
2Ease of operation
If the emitter is concentrated at the front end of the cathode for immediate electron emission, then starting performance is improved, but the emitter depletes rapidly causing flickers and shortened lamp life
Solution Approach 1:
The sintered compact is prepared in advance with high emitter concentration and positioned within the cathode structure before operation. This preliminary preparation creates a staged release mechanism where the emitter is gradually transported from the sintered compact to the front end, ensuring both good starting performance and sustained operation.
Solution Approach 2:
The patent segments the cathode structure into distinct functional zones: a front end portion for electron emission and a sintered compact region for emitter storage. This segmentation allows the emitter to be distributed between these zones, with the front end providing immediate emission capability and the sintered compact serving as a long-term reservoir.
3Reliability
If the emitter is transported rapidly from the rear portion to the front end of the cathode, then electron emission is maintained at the front end, but the emitter depletes too quickly causing early exhaustion
Solution Approach 1:
The patent creates a dynamic emitter supply system where the sintered compact gradually releases emitter material to the front end during cathode operation. The emitter concentration and transport rate are dynamically adjusted through the sintering process and thermal gradients, ensuring reliable electron emission while controlling depletion rate.
Solution Approach 2:
The patent utilizes parameter changes in the sintering process, particularly temperature gradients and emitter concentration distribution, to control the rate of emitter transport. By optimizing the sintering temperature and compact density, the emitter release rate is adjusted to match the consumption rate at the front end, preventing both depletion and accumulation.
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 ensures stable and prolonged electron emission, preventing early emitter depletion and maintaining satisfactory lighting properties for a longer period, while avoiding excessive vaporization and crack formation in the sintered compact.
Implementation Method 1
the emitter is not depleted at the front end part and satisfactory lighting is stably maintained for a long period of time since the emitter is diffused toward the front end part from the sintered compact containing high concentration of emitter in the cathode
Implementation Method 2
a pressing member is arranged on a rear end of the sintered compact in the hermetically sealed space such that the pressing member may press the sintered compact toward the front end part
Implementation Method 3
the rare earth oxide may be excessively vaporized by the lighting lamp, and a situation of early depletion may arise
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A discharge lamp includes an emitter other than thorium, which is added to a cathode in a luminous tube. Early depletion of the emitter due to excessive vaporization of the emitter from the cathode is prevented, while achieving stable lighting even at the start-up of the lighting. A main body part (31) of the cathode (3) is made from a high-melting-point metal material that contains no thorium, and a front end part (32) thereof is made from a high-melting-point metal material that contains an emitter (other than thorium). A sintered compact (34), which contains an emitter (other than thorium) at a concentration higher than the emitter contained in the front end part (32), is buried in a sealed space (33) that is formed within the main body part (31) and/or the front end part (32). The sintered compact (34) abuts against the front end part (32).