Cradle Stop Assembly Planar Plate Circuit Breaker
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Solution Overview
Problem
Cradle stop pins in electrical switching apparatus, such as circuit breakers, can cause damage and poor performance due to contact with the movable contact arm during operation, and existing solutions like notching reduce strength and increase manufacturing complexity.
Innovation Solution
A cradle stop assembly with a planar stop plate and resilient bumper that resists cradle member interference and pivotable contact arm over-rotation, featuring apertures and protrusions for secure coupling and a barrier member for electrical insulation, to absorb impact and prevent arcing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cradle stop pin is used, then the structure is simple and manufacturing is easy, but the movable contact arm strikes the pin causing bending and breaking, and arcing occurs with poor circuit breaker performance
Solution Approach 1:
The cradle stop assembly is divided into separate functional components: a cradle member with aperture, a stop plate with protrusions, and a barrier member. This segmentation allows each component to perform its specific function (support, positioning, insulation) without interfering with others, eliminating the striking and arcing problems while maintaining manufacturing simplicity
Solution Approach 2:
The barrier member acts as an intermediary between the movable contact arm and the cradle stop pin, providing electrical insulation and preventing arcing. The stop plate serves as an intermediary structure that positions the cradle member correctly to prevent the contact arm from striking the pin, thereby improving reliability without significantly increasing complexity
2Ease of operation
If the cradle stop pin is notched with a cut-out, then clearance is provided for the movable contact arm, but the strength of the cradle stop pin is reduced and manufacturing becomes more difficult and costly
Solution Approach 1:
Instead of notching the pin (which weakens it), the clearance function is separated into a distinct stop plate component with protrusions that engage with the cradle member aperture. This segmentation maintains the full strength of both the pin and stop plate while providing the necessary clearance through proper geometric arrangement
Solution Approach 2:
The clearance-providing function is extracted from the cradle stop pin itself and implemented through a separate stop plate assembly. This extraction allows the pin to remain solid and strong while the stop plate geometry provides the necessary clearance space for the movable contact arm during operation
3Ease of operation
If the cradle stop pin is notched with a cut-out, then clearance is provided for the movable contact arm, but manufacturing becomes much more difficult and costly
Solution Approach 1:
The assembly is segmented into standard components (pin, stop plate, barrier member) that can be manufactured using conventional processes without complex notching or cutting operations. Each component has simple geometry suitable for standard manufacturing methods, reducing cost and difficulty
Solution Approach 2:
The complex clearance-providing geometry is extracted from the pin manufacturing process and implemented through the stop plate assembly geometry. This allows the pin to be manufactured as a simple solid component, while the clearance function is achieved through the arrangement and shape of the stop plate and barrier member, simplifying manufacturing
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
Enhances the interruption performance of circuit breakers by preventing damage and arcing, maintaining contact integrity, and reducing manufacturing complexity while maintaining strength.
Implementation Method 1
a stop plate extending between the first member and the second member, such stop plate being generally planar and including a first stop portion and a second stop portion disposed generally opposite the first stop portion, wherein the first stop portion of the stop plate is structured to resist movement of the cradle member beyond a first predetermined position... and wherein the second stop portion of the stop plate is structured to resist the pivotable movable contact arm of the operating mechanism from undesirably pivoting beyond a second predetermined position
Data Source
AI summary
A cradle stop assembly is provided for a circuit breaker including an operating mechanism. The operating mechanism includes a pivotable movable contact arm and a cradle member which is movable between a latched position corresponding to separable contacts of the circuit breaker being closeable and an unlatched position corresponding to the separable contacts being tripped open. The cradle stop assembly includes a first member coupled to a portion of the operating mechanism, a second member disposed opposite the first member, and a generally planar stop plate extending between the first and second members. A first stop portion of the stop plate resists movement of the cradle member beyond a first predetermined position to avoid the cradle member undesirably interfering with the pivotable movable contact arm. A second stop portion resists the pivotable movable contact arm from undesirably pivoting beyond a second predetermined position.