Circuit Breaker Contact Assembly Spring Pivot Mechanism
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Solution Overview
Problem
Circuit breakers face issues with maintaining suitable contact pressure and low friction operation, especially when electrical contacts erode, leading to increased difficulty in tripping due to high frictional forces.
Innovation Solution
An electrical contact assembly featuring a crossbar, pivot pin, contact arm, and a spring assembly with a clevis pin that extends through the spring and is received in a pivot recess, allowing for a force vector to cross over the pivot axis upon tripping, ensuring consistent contact pressure and low friction operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a cam-follower mechanism is used to maintain contact pressure, then contact pressure can be maintained, but frictional forces increase significantly making tripping difficult
Solution Approach 1:
The patent replaces the cam-follower mechanism with a direct spring compression system. The spring assembly compresses directly against the contact arm without requiring a cam-follower linkage, eliminating the high friction associated with the cam surface while maintaining contact pressure through direct spring force application.
Solution Approach 2:
The invention extracts and eliminates the cam-follower component from the system, using only the essential spring compression function. This removes the source of high friction while preserving the contact pressure maintenance capability through the spring alone.
2Force
If contact arms are designed with long springs, then contact pressure can be maintained, but spring buckling occurs reducing effectiveness
Solution Approach 1:
The patent introduces curvature by allowing the spring assembly to pivot through an arc rather than moving in a straight line. The spring follows a curved path defined by the pivot point, which provides lateral support and prevents buckling while maintaining the necessary compression force.
Solution Approach 2:
The spring assembly is separated into independent pivotable connections at both ends (one end to the contact arm, one end to the housing), allowing each segment to rotate independently. This segmentation enables the spring to follow a curved compression path that prevents buckling.
3Stability of the object's composition
If cam-follower mechanisms are used to hold contacts open, then open position can be maintained, but contact pressure decreases as contacts erode
Solution Approach 1:
The patent replaces the cam-follower mechanism with a direct spring compression system that maintains constant contact pressure through spring force. The spring's elastic properties ensure consistent pressure regardless of contact erosion, while the pivotable connection maintains stable open position through geometric constraints.
4Ease of operation
If pivotable spring assembly connections are used, then friction is reduced for smooth operation, but device complexity increases
Solution Approach 1:
The pivotable connection serves multiple functions simultaneously: it reduces friction during operation, prevents spring buckling through curved path constraints, and maintains stable open position through geometric positioning. This multi-functionality justifies the added complexity by resolving multiple problems with a single design feature.
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 contact closing pressure, low friction forces for unimpeded opening, and maintains the contact arm in an open configuration during interruption events, while allowing for the use of longer springs without buckling, enhancing linear contact engagement forces.
Implementation Method 1
a spring assembly including a spring and a clevis pin wherein an end of the pin extends through the spring and is received in a pivot recess in the crossbar
Data Source
AI summary
Embodiments provide an electrical contact assembly. The electrical contact assembly includes a crossbar, a pivot pin mounted in the crossbar, a contact arm pivotally mounted on the pivot pin and rotatable about a pivot axis, a moveable electrical contact spaced from the pivot axis in a first arm portion of the contact arm, and a spring assembly coupled between the crossbar and the contact arm, the spring assembly including a clevis pin and a spring received on the clevis pin wherein an end of the clevis pin extends through the spring and is received in a pivot recess in the crossbar. Electrical contact assemblies with offset rod ends and limit stops are also disclosed. Systems including the electrical contact assembly and methods of operating the electrical contact assembly are provided, as are other aspects.