Bimetal Strip Mounting for Constant Thermal Stroke
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Solution Overview
Problem
Existing bimetallic thermal trip units in current breaking devices face challenges in handling higher currents while maintaining the same device size, as the reduced section of the bimetallic strip results in high power generation for low currents but is penalizing for high currents.
Innovation Solution
The bimetallic strip is mounted to be fixed at different locations along its support, allowing for a variable useful surface length, which can be adjusted based on the device caliber to maintain constant thermal travel, and the fixing is done by welding, separating current conduction and embedding functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the bimetallic strip uses a reduced section for embedding in the support, then the device size can be kept compact, but the power generated increases excessively for high current applications
Solution Approach 1:
The bimetallic strip is divided into two functional parts: a first part with reduced section for embedding in the support (providing mechanical anchoring), and a second part with larger section extending through the support (providing current conduction path). This segmentation allows each part to optimize its function independently, reducing power generation in the embedding region while maintaining adequate current carrying capacity through the extended portion.
Solution Approach 2:
Different sections of the bimetallic strip are given different cross-sectional areas according to their specific functional requirements. The embedding section has reduced area for compact mounting, while the current conduction section has increased area to reduce resistive heating and power generation. This local quality variation resolves the contradiction between compact size and low power generation.
2Device complexity
If the bimetallic strip is fixed at a single fixed position on the support, then the assembly is simple, but the useful surface length cannot be adjusted for different device calibers
Solution Approach 1:
The fixing position of the bimetallic strip on the support is made variable rather than fixed. The support structure allows the bimetallic strip to be positioned at different locations along its length, enabling adjustment of the useful surface length according to different device calibers and application requirements, while maintaining a relatively simple assembly process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for increased operating current without changing the device size, enabling a constant thermal and mechanical stroke across the current range, reducing power generation and enabling the manufacture of protective devices with larger calibers at a constant volume.
Implementation Method 1
The bimetallic strip can be heated either directly by passing current through the bimetallic strip
Implementation Method 2
the heating of the bimetallic strip being representative of the heating of the device or protected electrical installation, so as to trigger the cut-off device when this temperature rise exceeds a predetermined threshold
Implementation Method 3
indirectly by passing current through an insulated electric heater in thermal contact with the bimetallic strip
Implementation Method 4
an insulated electric heater in thermal contact with the bimetallic strip
Implementation Method 5
the fixing of the bimetallic strip on the support is carried out by welding
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present invention relates to a device for assembling a bimetallic strip (1) and a piece serving as a support (5) for this bimetallic strip in a current cutting device, said bimetallic strip (1) being electrically connected by a first end (1 a) called free end to a first connection range (3) called input, and by another end by which this bimetallic strip is fixed to the aforementioned support (5), to a second connection range called output (4).This device is characterized in that this bimetallic strip (1) is mounted through the aforementioned support (5) so as to be able to be fixed at different places along the length of this bimetallic strip, said bimetallic strip thus having a first (1c) and a second part (1d) located respectively on one side and the other of the aforementioned support (5), the first part located on the side of the free end (1a) of the bimetallic strip (1), corresponding to the so-called useful surface (1b) of this bimetallic strip, the length of this useful surface being variable according to the embedment length I of this bimetallic strip in the support (5), this embedment length being determined according to the size of the device in order to obtain a constant thermal stroke, whatever the size, as well as an electrical protection device including it.