Trip Unit Captive Bar Tolerance Buildup
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Solution Overview
Problem
The existing design of circuit breaker trip units suffers from alignment and tolerance errors, leading to issues such as a loose trip bar causing inconsistent latch loading and premature tripping, due to multiple tolerances required in the housing assembly.
Innovation Solution
A captivation assembly is integrated into the housing assembly on a single sidewall to securely hold the trip bar, reducing tolerance buildup and ensuring the trip bar is maintained within a defined space, thereby eliminating the need for multiple tolerances and preventing misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the trip bar is disposed in a saddle extending from one housing assembly sidewall with the other housing assembly sidewall coupled to the first housing assembly sidewall, then the housing assembly defines an enclosed space for internal components, but multiple tolerances built into separate housing assembly sidewalls allow the trip bar to be loose or misaligned, causing rattle and inconsistent latch loading
Solution Approach 1:
The patent merges the trip bar support function into a single housing assembly sidewall by providing a saddle that extends from one sidewall and a captivation assembly on the same sidewall. This eliminates the need for multiple sidewalls to define the trip bar position, thereby reducing tolerance buildup and ensuring consistent latch loading.
2Ease of operation
If multiple tolerances are built into separate housing assembly sidewalls, then the housing assembly can enclose internal components, but the trip bar has too much space and becomes loose, promoting premature tripping or requiring excessive force
Solution Approach 1:
The patent applies local quality by concentrating the trip bar support and captivation functions in a specific location on one housing assembly sidewall. The saddle and captivation assembly are positioned to provide precise local support, ensuring consistent trip force without the accumulation of tolerances that would occur with distributed support across multiple sidewalls.
3Manufacturing precision
If the trip bar is captured by a captivation assembly on a single sidewall, then tolerance buildup is reduced and alignment is improved, but the housing assembly structure must be modified
Solution Approach 1:
The captivation assembly performs multiple functions: it supports the trip bar, maintains precise alignment, reduces tolerance buildup, and provides a mounting structure for the trip detection circuit. By consolidating these functions into a single assembly on one sidewall, the overall housing assembly structure is simplified despite the added complexity of the captivation assembly itself.
Data Source
AI summary
A trip unit wherein one sidewall of a trip unit housing assembly captivates a trip bar is provided. A captivation assembly is coupled, or directly coupled, to a trip unit housing assembly, thereby limiting tolerance buildup. The captivation assembly includes a trip bar bearing cap having a stop feature, thereby limiting tolerance buildup. The trip bar includes a radial stop paddle having hemispherical protrusions structured to contact the trip unit housing, thereby limiting tolerance buildup. The captivation assembly elements are incorporated into the trip unit housing assembly and captivates the trip bar in all but one axis, thereby limiting tolerance buildup and improving repeatability.