Surface-Mount Protective Device with Coplanar Electrodes
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Solution Overview
Problem
Conventional protection devices for electrical apparatuses require separate connection of terminals and arms, necessitating a space for connecting, which complicates the electrical connection and mounting process.
Innovation Solution
A protection device design featuring a resin base with exposed first and second terminals forming electrodes on the bottom surface, allowing for surface mountability, where the bimetal component activates to disconnect the arm from the first terminal and connect to the PTC component, ensuring current interruption and maintaining the open state through Joule heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the terminal and arm are separately connected in conventional protection devices, then the electrical connection can be established, but the device requires additional space for connecting and the mounting process becomes complicated
Solution Approach 1:
The patent merges the terminal and arm into a single integrated structure where the terminal extends to form the electrode directly. This eliminates the need for separate connection of terminal and arm, reducing both the space required and the complexity of the mounting process while maintaining electrical connectivity
2Reliability
If the bimetal component is disposed in series to interrupt current, then current interruption is achieved, but the activated state cannot be maintained without additional PTC component
Solution Approach 1:
The patent introduces a PTC component as an intermediary element that works in conjunction with the bimetal component. The PTC component maintains the activated state by providing thermal feedback, ensuring reliable current interruption while the bimetal component provides the primary switching action. This combination achieves reliable protection without requiring overly complex additional mechanisms
3Strength
If the protection device is designed for through-hole mounting, then secure connection is achieved, but surface mounting capability is lost
Solution Approach 1:
The patent transitions the mounting approach from through-hole (vertical dimension) to surface mounting (horizontal dimension). The terminal extends to form an electrode on the bottom surface, enabling lateral electrical connection suitable for surface-mount technology while maintaining secure electrical connection through the extended terminal structure
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
The design enables a compact, surface-mountable protection device that effectively interrupts excessive current and maintains the open state, enhancing safety and ease of integration into electrical systems.
Implementation Method 1
The bimetal component comprises a sheet member of a bimetal metal. The bimetal component is configured to be activated (i.e. deformed) so as to interrupt a current flowing through the bimetal component when the bimetal component itself reaches a higher temperature in excess of a predetermined temperature
Implementation Method 2
the PTC component generates a Joule heat by the current and this heat is transmitted to the bimetal component so that the activated state of the bimetal component can be ensured
Data Source
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AI summary
Provided is a surface-mountable protective device formed comprising a bimetal element and a PTC element. This protective device is characterized by comprising a resin base, a first terminal, a second terminal, a PTC element, a bimetal element, an arm, an upper plate and a resin cover, and in that a portion of the first terminal configures the first electrode, a portion of the second terminal configures a second electrode, the exposed surface of the first electrode and that of the second electrode are coplanar. Under normal conditions, the protective device is in a state in which the first terminal, the arm and the second terminal are electrically connected in series, and under abnormal conditions in which the bimetal element is actuated, the protective device assumes a state in which the first terminal and the arm are electrically disconnected, and meanwhile assumes a state in which the first terminal, the PTC element, the bimetal element, the arm and the second terminal are electrically connected in series in that order.