Double Pole-Double Throw Proximity Switch Sealing for Seismic Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing double pole-double throw proximity switches for nuclear reactors face challenges such as low performance at low currents, complex internal moving parts, contamination risks, short service life, and failure to maintain contact continuity during severe seismic testing.
Innovation Solution
A hermetically sealed proximity switch design featuring a magnetic proximity switch assembly within a body tube, a crush ring compression device, and a potting system that seals the assembly to withstand harsh environments and seismic accelerations, eliminating the need for serviceable parts and ensuring continuous contact under extreme conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high amp rated mechanical switch is used, then reliability under seismic conditions is improved, but performance at low current deteriorates due to resistance problems
Solution Approach 1:
The switch is divided into two independent poles, each handling separate circuits. This segmentation allows each pole to be optimized for its specific current requirements, with contact configurations that minimize resistance for low current applications while maintaining seismic reliability.
Solution Approach 2:
Instead of using a single high-amp switch for all circuits, the invention inverts the approach by using two lower-current switches in a double-pole configuration. This inversion allows each switch to operate in its optimal current range, improving low-current performance while maintaining overall system reliability.
2Measurement precision
If a lever arm connecting to the target is used, then detection capability is improved, but device complexity increases due to complicated internal moving parts
Solution Approach 1:
The invention extracts and eliminates the lever arm and associated complex internal moving parts from the switch mechanism. Detection is achieved through a simpler direct-acting mechanism that responds to target approach without requiring mechanical leverage or cam systems.
Solution Approach 2:
The complex mechanical lever arm system is replaced with a simpler mechanical direct-acting system. The switch uses a streamlined mechanism that converts target proximity directly into contact actuation, eliminating the need for intermediate leverage mechanisms and reducing overall device complexity.
3Adaptability or versatility
If multiple points of potential contamination ingress are present, then adaptability to mounting configurations is improved, but reliability deteriorates due to contamination risks
Solution Approach 1:
The invention merges multiple potential ingress points into a single integrated sealed housing. The hermetic seal encompasses the entire switch assembly, combining what would otherwise be separate sealing locations into one continuous barrier against contamination, while still accommodating various mounting orientations.
Solution Approach 2:
The sealed housing design provides universal protection against contamination while accommodating multiple mounting configurations. The hermetic seal serves the dual function of preventing ingress and allowing operational flexibility in different orientations, eliminating the trade-off between adaptability and contamination resistance.
4Ease of operation
If internal moving components are used, then switch functionality is improved, but service life decreases due to wear of moving parts
Solution Approach 1:
The switch is designed with minimized moving components that require no maintenance or service. The hermetic seal protects the internal mechanism from environmental degradation, and the simplified construction eliminates parts that would otherwise require periodic replacement, enabling the switch to service itself throughout its operational life.
Solution Approach 2:
The invention discards the traditional approach of using multiple wear-prone moving components. By eliminating springs, cams, and other parts subject to fatigue and wear, the switch achieves a maintenance-free operational life without sacrificing switching functionality, effectively recovering the full service life potential of the device.
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 provides reliable operation in harsh environments, maintains contact pressure during 10 g seismic testing without discontinuity, and extends service life, while being adaptable to various current ranges and temperature conditions.
Implementation Method 1
a hermetic seal covering the blind bore between the magnetic proximity switch assembly and the open end
Implementation Method 2
a crush ring compression device having a threaded plug body that screws into the open end of the blind bore and sealingly engages the crush ring
Implementation Method 3
The proximity or limit switch may use magnetic attraction to complete various electronic circuits based on the proximity of a target
Data Source
AI summary
Proximity switches include a hermetically sealed unit that can be used in harsh environments and under significant pressures, such as underwater and in nuclear power facilities, without having any parts that would require replacement or periodic maintenance. The proximity switches are preferably switches actuated by physical movement of a contact in response to changing magnetic forces. The switches are preferably disposed in a body tube optionally including a hermetic seal assembly to seal an open end of the body tube and/or a ferrule that prevents electrical wires attached to the switch inside the body tube from being pulled away from the switch. Further, the switches preferably maintain a contact pressure between electrical contacts sufficient to withstand acceleration seismic testing of 10 g with no contact discontinuity.