Circuit Breaker Blocking Device for Welded Contact Indication

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Solution Overview

Problem

Circuit breakers face challenges in reliably indicating a switched-off position when main contacts are welded, which can lead to unsafe operation and potential fires due to continuous current flow.

Innovation Solution

A circuit breaker with a blocking device that includes a rotary locking latch and a locking lever, operatively connected to a drive shaft and a separate blocking mechanism, which prevents the switch from being locked in a switched-off position when the contacts are welded, ensuring a secure and reliable indication of the switch position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional switching mechanism is used without a separate blocking device, then the device complexity is low, but the reliability of switch position indication is compromised when contacts are welded

Engineering Contradiction:
Improveswitch position indication reliabilityVSAvoidswitching mechanism complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The switching mechanism is segmented into two independent parts: the main switching mechanism that operates the contacts, and a separate blocking device that independently monitors and blocks the switch position indicator. This segmentation allows the blocking function to operate autonomously without interfering with the main switching operation, ensuring reliable indication even when contacts are welded.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The blocking device acts as an intermediary mechanism between the switching mechanism and the switch position indicator. It includes a blocking lever with a blocking element that can prevent the indicator from showing a false switched-off position when contacts are welded, thus mediating the information flow between the actual switch state and the indicated state.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the switching mechanism operates without a blocking device, then the ease of operation is high, but the safety against welded contact operation is compromised

Engineering Contradiction:
Improveharmful effects of welded contactsVSAvoidswitch operation simplicity
Core Design Contradiction:
Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The blocking device implements preliminary anti-action by proactively preventing the switch position indicator from displaying a switched-off position when contacts are welded. The blocking lever is positioned and configured to automatically engage and block the indicator in the event of welded contacts, countering the harmful effect before it can lead to unsafe operation.

Inventive Principle:
Principle #9Preliminary anti-action

Solution Approach 2:

The blocking device is self-activating and does not require external control or complex operation. It automatically detects the welded contact condition through its mechanical linkage and activates the blocking function independently, maintaining ease of operation while enhancing safety.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3002772B1Circuit breaker with a blocking device for a reliable shift lever position indicator
Publication Date: 2017.07.19 SIEMENS AG
  • EP3002772B1 patent drawingFigure 1
  • EP3002772B1 patent drawingFigure 2~4
  • EP3002772B1 patent drawingFigure 5

AI summary

The invention relates to a switching device with a locking device for a reliable switching position indicator, comprising an actuating mechanism that includes an actuating element (1) and is operatively connected via a first transmission mechanism to a switching lock, which in turn operates a switching lever (13) via a second transmission mechanism, and a contact system (14) comprising a fixed switching element with contacts, which is arranged opposite a movable switching element (15) with contacts, which is guided in a contact slide (16), wherein the switching lever (13) is operatively connected to the movable switching element (15). The invention is characterized in that the first transmission mechanism has a drive shaft (3) which is coupled both to the switching lock and to a separate locking device, through which a switching position for a contact system (14) with welded contacts can be transmitted.