Silicone Rubber Shield for Circuit Breaker PCBs
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Solution Overview
Problem
Existing shields for electrical components in molded case circuit breakers, such as thermoplastic clamshell-type casings, fail to adequately protect against flying debris and gas-carried carbon, leading to malfunctions and short circuits due to gaps and labor-intensive assembly processes.
Innovation Solution
A resilient sheet member made from flexible and elastic materials like silicon rubber, conforming to the shape of electrical components, provides effective shielding and protection by adhering to the components and resisting carbon accumulation, while being resistant to flame, abrasion, moisture, and outgassing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thermoplastic clamshell-type shield is used to protect electrical components, then some physical protection is provided, but the shield fails to adequately protect against flying debris and gas-carried carbon due to gaps in the structure
Solution Approach 1:
The patent applies a conformal coating made of flexible material (such as silicone rubber or thermoplastic elastomer) that conforms to the shape of the electrical component. This flexible film provides continuous coverage over the component surface, eliminating gaps present in rigid clamshell shields, and effectively blocking flying debris and gas-carried carbon while maintaining reliability.
Solution Approach 2:
The shield combines rigid thermoplastic clamshell structure with a flexible conformal coating material. The composite structure integrates the structural support of the rigid shell with the gap-free protective coverage of the flexible coating, achieving comprehensive protection against both physical impact and carbon accumulation.
2Object-affected harmful factors
If a conformal coating is applied to protect against arc byproducts, then protection against carbon accumulation is improved, but the coating may melt or drip under high temperature conditions
Solution Approach 1:
The patent selects conformal coating materials with specific temperature resistance parameters, such as silicone rubber or thermoplastic elastomer, which maintain structural integrity at high temperatures. These materials are chosen to have melting points significantly higher than the operating temperatures encountered during arc events, preventing melting and dripping while maintaining protective coverage.
Solution Approach 2:
The shield combines the thermoplastic clamshell structure with a high-temperature resistant conformal coating material. This composite approach integrates the structural protection of the rigid shell with the thermal stability and carbon resistance of the specialized flexible coating, achieving both protection goals simultaneously.
3Strength
If a rigid shield structure is used, then structural strength is maintained, but the assembly process becomes labor-intensive and time-consuming
Solution Approach 1:
The conformal coating is applied as a flexible film that can be pre-formed and then easily attached to the rigid clamshell shield or directly to the electrical component. This flexible coating layer adds minimal structural weight while providing the necessary protective coverage, and its flexibility allows for simpler assembly processes compared to fitting rigid protective components.
Solution Approach 2:
The conformal coating can be pre-formed to match the contours of the electrical component or shield surface before final assembly. This preliminary preparation allows the coating to be applied as a pre-fabricated element rather than requiring complex in-situ forming during assembly, thereby reducing labor intensity and assembly time while maintaining the structural integrity of the rigid shield.
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 resilient sheet member effectively shields electrical components from debris and carbon accumulation, reducing the risk of malfunctions and improving the reliability of electrical apparatus by conforming to component shapes and providing enhanced protection against high-temperature and chemical exposure.
Implementation Method 1
The resilient sheet member is structured to overly at least one of the electrical components coupled to the generally planar member
Implementation Method 2
resisting carbon accumulation, while being resistant to flame, abrasion, moisture, and outgassing
Implementation Method 3
A resilient sheet member made from flexible and elastic materials like silicon rubber
Data Source
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AI summary
A shield is provided for a circuit breaker including a printed circuit board (PCB). The PCB is a generally planar member with a plurality of electrical components each having a corresponding shape. The shield includes at least one resilient sheet member at least partially covering the generally planar member and at least one of the electrical components coupled thereto. The resilient sheet member generally conforms to the corresponding shape of the at least one of the electrical components in order to shield and protect it from debris and to resist accumulation of gas-carried carbon. The resilient sheet member is made from a material, such as silicon rubber, which is flexible and elastic within a temperature range of about -70 to about 450 degrees Fahrenheit, and it is flame-resistant, tear and abrasion-resistant, impervious to moisture and chemicals, fungus-resistant, and resistant to outgassing.