Circuit Breaker Locking Device Prevents False Off Position
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Solution Overview
Problem
Existing circuit breakers with locking devices fail to prevent the rocker arm from being locked in a false off position due to welded main contacts, posing a safety risk as it can lead to incorrect assumptions about the circuit being de-energized, and existing solutions are either complex and expensive or require design modifications that are not feasible.
Innovation Solution
A cost-effective locking device design where the rocker arm cannot be locked when main contacts are welded, utilizing a head screw and U-lock mechanism that ensures alignment only in the normal off position, preventing unauthorized locking and ensuring the locking device is tamper-proof and easy to attach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking device is added to the circuit breaker, then the safety of the circuit breaker is improved, but the device complexity increases
Solution Approach 1:
The locking device is integrated into the circuit breaker housing, with the locking lever nested within the housing structure. The U-lock passes through openings in the housing to engage the lever, creating a compact nested arrangement that adds safety without significantly increasing overall device complexity
Solution Approach 2:
The locking mechanism uses the existing structural elements of the circuit breaker (housing, rocker arm positions) to provide the locking function. The feeling element utilizes the natural movement of the rocker arm to detect intermediate positions, and the expansion element uses spring force to automatically position the locking lever, reducing the need for additional active components
2Reliability
If a locking device with feeling element is implemented, then the reliability of position detection is improved, but the device complexity increases
Solution Approach 1:
The feeling element serves multiple functions: it detects intermediate positions of the rocker arm, prevents locking in those positions, and works together with the expansion element to ensure proper locking only in the off position. This multi-functionality reduces the need for separate detection and prevention mechanisms
Solution Approach 2:
The feeling element acts as an intermediary between the rocker arm position and the locking mechanism. It translates the physical position of the rocker arm into a mechanical constraint that either allows or prevents the locking lever from engaging, providing reliable position detection through simple mechanical interaction
3Ease of operation
If the locking device allows overtravel positioning, then the ease of operation is improved, but the reliability decreases when contacts are welded
Solution Approach 1:
The feeling element is positioned to detect intermediate positions before the rocker arm can complete its movement to a false off position. By preventing locking engagement at these intermediate positions, the system proactively blocks the harmful condition of locking with welded contacts, while still allowing normal overtravel operation when contacts are not welded
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a circuit breaker (1) with a locking device (13) for enclosing the rocker arm (3) in its off position by means of a cover (15). The problem to be solved is a cost-effective locking device that prevents locking when the main contacts are welded together. For this purpose, the switching cam (9) of the switching mechanism (41) has a threaded bore (11) and the locking device (13) has a through bore (17) through which a cap screw (21), serving to fasten the locking device (13) to the switch housing (5), extends to the switching cam (9).The distance between the threaded bore (11) and the rocker arm (3) on the one hand, and between the through-hole (17) and a first inner wall (45) of the cover (15) located close to the rocker arm (3) on the other, are dimensioned such that only in the off position is the rocker arm (3) enclosed by the cover (15) and the through-hole (17) aligned with the threaded bore (11). A padlock (37) that can be inserted into the locking opening (27) of the locking device (13) prevents further access to the head screw (21).