Two-Piece Handle for Miniature Circuit Breakers
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Solution Overview
Problem
Miniature circuit breakers face design restrictions due to size constraints, leading to wear and inefficiency in single-piece handles and partially coiled tension springs, which are costly and inefficient.
Innovation Solution
A two-piece handle assembly with a non-conductive handle section and a metallic link section, featuring a pin joint connection and clearance gaps, allowing for greater design flexibility and reduced mechanical interference, and enabling the use of softer materials for the handle section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single piece handle is used to interface with the movable blade, then the handle assembly can be simple in structure, but the handle is subject to greater wear from constant tension spring force and operational cycling
Solution Approach 1:
The handle assembly is divided into two separate pieces: a handle section and a link section. The link section is pivotally connected to the movable blade and absorbs the constant tension spring force, while the handle section is pivotally connected to the link section and is operated by the user. This segmentation isolates the handle section from the harmful forces, significantly reducing wear on the user-operated portion while maintaining structural simplicity.
2Strength
If the handle is made thick using rigid material to provide sufficient strength, then the handle has adequate durability, but the thickness impacts the design of the trip lever and other components in the interference area
Solution Approach 1:
By separating the handle into a handle section and a link section, the link section can be designed as a thin metallic component that provides the necessary structural strength and rigidity. The handle section can be optimized for user operation without requiring excessive thickness, thereby reducing interference with the trip lever and other components in the limited space of the MCB.
Solution Approach 2:
The handle assembly combines different materials: the link section is made of metallic material (such as steel) to provide strength and rigidity, while the handle section can be made of non-conductive material. This composite approach allows each section to be optimized for its specific function without compromising overall performance.
3Volume of moving object
If a partially coiled tension spring is used to avoid entanglement with the handle, then the spring can fit in the limited space, but the coils must be designed to provide greater force and the design is costly and inefficient
Solution Approach 1:
The separation of the handle into two sections allows the use of a fully coiled tension spring in the link section area, where it can operate efficiently without entanglement issues. The link section acts as an intermediary that isolates the spring from the handle section, enabling optimal spring design while maintaining compact dimensions suitable for MCB applications.
Data Source
AI summary
A miniature circuit breaker 10 having a handle assembly 100 formed of two separate pieces, namely a handle section 110 and a link section 150 with a first end 152 and a second end 154. The link section 150 is pivotally connected at the first end 152 to the handle section 110, and at the second end 154 to a movable blade 30 carrying the movable contact 32 of the circuit breaker. The handle section 110 can be formed of a plastic, and the link section 150 can be formed of a metallic material. A metallic link section can be thinner than an equivalent plastic part, and can provide a robust metal-to-metal interface with the blade 30 carrying the movable contact 32. The handle assembly 100 can also have one or more clearance gaps 132 and 134 designed between the handle section 110 and link section 150 to provide for a range of independent motion by the handle section 110 in relation to the link section 150.