Pellet Thermal Fuse Contact Structure for Stable Cutoff
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Solution Overview
Problem
Conventional temperature-sensitive pellet type thermal fuses fail to perform a stable fuse cutoff operation due to uneven melting of the pellet, leading to potential malfunction when the internal or ambient temperature exceeds the rated service temperature.
Innovation Solution
A temperature-sensitive pellet type thermal fuse design featuring a movable terminal with a spring-biased movable contact plate that maintains contact with the inner wall of a fixed terminal's through hole, allowing for stable sliding contact and preventing interference with the case's inner wall, even when the pellet melts unevenly, ensuring reliable disconnection above the cutoff temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the movable terminal is designed with contact segments that contact the case inner wall, then the device complexity is reduced, but the manufacturing precision requirements increase due to tilting issues
Solution Approach 1:
The guide post acts as an intermediary that provides precise guidance for the movable terminal. Instead of relying on the movable terminal to maintain precise alignment with the case inner wall, the guide post's precisely positioned sliding surface ensures proper alignment, reducing the manufacturing precision requirements for the movable terminal itself.
2Reliability
If the movable contact plate is made larger to ensure stable contact, then the contact stability is improved, but the device complexity increases due to potential interference with the case inner wall
Solution Approach 1:
The guide post serves as an intermediary that constrains the movable contact plate's movement path. The contact plate can be made larger to ensure stable contact with the guide post's sliding surface, while the guide post prevents the contact plate from interfering with the case inner wall by providing a defined sliding path.
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 design ensures a stable and reliable fuse cutoff operation, reducing defect rates and allowing for a wider allowable range of dimensional sizes in key components, thereby minimizing assembly and manufacturing defects.
Implementation Method 1
a temperature sensitive pellet installed in the case in such a manner that the pellet maintains a predetermined height below a fuse cutoff operation temperature and melts above the fuse cutoff operation temperature
Implementation Method 2
a first spring biasing the movable terminal so as to render the movable terminal in contact with the second lead wire below the fuse cutoff operation temperature
Implementation Method 3
a second spring pressing the movable terminal in the direction to separate the movable terminal from the second lead wire
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A temperature-sensitive pellet type thermal fuse is disclosed. The thermal fuse comprises: a metal case (10); a first lead wire (L1) fixedly installed on an open end of the case (10) to be insulated from the case (10) by an insulating bushing (20); a second lead wire (L2) electrically connected to the bottom wall (12) of the case (10); a temperature-sensitive pellet (12) installed inside the case (10); a movable terminal (60) being in contact with the fixed contact point (L2a) of the second lead wire (L2) and with the fixed terminal (40) below a fuse cutoff operation temperature, and being in contact with the case (10) but separated from the fixed contact point (L2a) of the second lead wire (L2) above the fuse cutoff operation temperature; a fixed terminal (40) having a through hole (41) with an inner wall, and being fixed on an inner wall (11) of the case; and the movable terminal (60) having a movable contact element (50) slidably contacting with the inner wall of the through hole (41) of the fixed terminal (40) to electrically connect to the fixed terminal (40).