Circuit Breaker Interlock Prevents Premature Auxiliary Latch Reset

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Solution Overview

Problem

Existing circuit breaker mechanisms lack a secure feature to prevent premature resetting of the auxiliary latch after tripping, leading to potential accidental reengagement of the trip bar latch and failure to reset the breaker.

Innovation Solution

An interlock mechanism using complementary interfering parts on the auxiliary latch and cradle, such as tabs, to physically prevent the auxiliary latch from pivoting back into the closed state until the cradle is properly reset, ensuring the auxiliary latch remains in an open state until the cradle is reengaged.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If heavy springs and dampers are used to prevent auxiliary latch from resetting prematurely, then the reliability of preventing premature reset is improved, but the device complexity and cost increase

Engineering Contradiction:

Improveprevention of premature auxiliary latch resetVSAvoidmechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The auxiliary latch is segmented into two functional parts: a movable auxiliary latch body and a separate cradle component with interfering tabs. This segmentation allows the cradle to independently control the auxiliary latch's movement without requiring additional springs or dampers, resolving the contradiction between reliability and complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cradle acts as an intermediary component between the auxiliary latch and the trip bar latch. The cradle's interfering tab physically blocks the auxiliary latch from resetting prematurely, providing the needed reliability control without adding complex spring-damper mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If a push to trip button is used to trip the mechanism again, then the ability to retrip the breaker is improved, but the device complexity increases

Engineering Contradiction:

Improveability to rettrip breakerVSAvoidmechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The cradle serves multiple functions: it engages with the auxiliary latch during normal operation, prevents premature resetting through its interfering tab, and enables ret tripping when the operator manually moves it. This multi-functionality provides versatility without adding separate components, resolving the contradiction between adaptability and complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If the auxiliary latch is allowed to reset freely, then the ease of operation is improved, but the reliability of preventing accidental trip bar reset deteriorates

Engineering Contradiction:

Improveauxiliary latch movement freedomVSAvoidprevention of accidental trip bar latch reengagement

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The cradle's interfering tab is positioned to preemptively block the auxiliary latch's path toward the trip bar latch before accidental reengagement can occur. This preliminary anti-action prevents the harmful effect while allowing the auxiliary latch to move freely within the permitted open state range, resolving the contradiction between ease of operation and reliability.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS8120452B2Mechanical interlock for circuit breaker to prevent relatching of the breaker

Publication Date: 2012.02.21 SIEMENS INDUSTRY INC

AI summary

An apparatus and method for restricting auxiliary latch movement within a tripped circuit breaker. An auxiliary latch is held in a closed state and is biased into an open state. When the trip bar is activated in response to an overload condition, it releases the auxiliary latch which pivots to the open state. The cradle is released and pivots to disengage the breaker contact. Tabs on the cradle and auxiliary latch cooperatively interlock to limit auxiliary latch movement until the latch is properly reset.