Hexagonal Pole Shaft Assembly for Circuit Breaker Positioning
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Solution Overview
Problem
Existing electrical switching apparatus, such as circuit breakers, face challenges in achieving precise positioning of pole shaft throws due to potential shifting or warping, which affects the forces applied and the overall operation of the mechanism.
Innovation Solution
A pole shaft assembly with a hexagonal cross-sectional shaft and correspondingly shaped throw assemblies, secured by blind rivets and collars, ensures precise and accurate positioning of throw assemblies, allowing for self-orientation and maintenance of desired positions, thereby enhancing the operation of circuit breakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If throws are welded to the shaft, then the assembly is structurally strong, but positioning precision deteriorates due to shifting or warping
Solution Approach 1:
The throw assembly is divided into separate components: the throw body and the positioning features, which are then assembled to the shaft using fasteners rather than welding. This segmentation allows each component to be manufactured independently with precise tolerances and then joined without causing warping or shifting.
Solution Approach 2:
Collars are introduced as intermediary components between the throw assemblies and the shaft. These collars provide precise positioning features (such as hexagonal cross-sections) that mate with corresponding features on the shaft, ensuring accurate positioning while the fasteners provide the structural connection without causing warping.
2Strength
If welding is used to attach throws to shaft, then connection is strong, but complexity increases due to precision requirements
Solution Approach 1:
The assembly is segmented into modular components (shaft, collars, throw assemblies, fasteners) that can be manufactured independently and assembled in a standardized sequence. This reduces the complexity of the manufacturing process compared to precision welding while maintaining connection strength.
Solution Approach 2:
The connection method changes from welding (thermal process requiring precise control) to mechanical fastening (cold process with standardized tolerances). This parameter change in the joining process reduces assembly complexity while maintaining structural integrity through the collar-fastener system.
3Ease of manufacture
If traditional positioning methods are used, then assembly is simple, but manufacturing precision deteriorates due to shifting
Solution Approach 1:
The shaft and collar features use asymmetric geometric shapes (such as hexagonal cross-sections) that provide inherent positioning and prevent rotation or shifting. This asymmetric design ensures precise positioning while maintaining relatively simple assembly procedures through form-fit connections.
Solution Approach 2:
Collars serve as intermediary positioning elements that translate simple fastener installation into precise positioning. The collars' geometric features (hexagonal cross-sections) mate with corresponding features on the shaft, providing accurate positioning without requiring complex assembly procedures.
Data Source
AI summary
A pole shaft assembly is for an electrical switching apparatus. The electrical switching apparatus includes a housing, separable contacts enclosed by the housing, and an operating mechanism structured to open and close the separable contacts. The pole shaft assembly includes a shaft structured to cooperate with the operating mechanism and to be pivotably coupled to the housing. A number of throw assemblies are disposed on the shaft, and are secured with respect to the shaft with fasteners. The shaft includes first and second opposing ends and an elongated body portion extending therebetween. The elongated body portion of the shaft has a cross-sectional shape comprising a number of orienting features.