A normally open thermal trip switch

Abstract

The normally open thermal trip switch of the present invention includes a housing, a first conductor, a second conductor, and a limiting member. The first and second conductors are respectively disposed within the housing. The limiting member, located within the housing, initially positions the elastic first conductor, thus insulating the first and second conductors. The portion of the limiting member that limits the first conductor is made of a low-melting-point material. When the temperature rises to a threshold range, the portion of the limiting member that contacts the first conductor softens or melts, releasing the limiting position of the first conductor. Under its own elastic force, one end of the first conductor located within the housing displaces and makes conductive contact with the second conductor, forming a conductive series circuit. When the normally open thermal trip switch is in operation, current flows through the series circuit formed by the direct conductive contact between the first and second conductors. The normally open thermal trip switch of the present invention has a simple structure and allows for quick integration of heat dissipation components into the circuit to protect power devices.

Description

Technical Field

[0001] This invention relates to the fields of power control and electric vehicles, and in particular to protective devices for power devices in the event of fault current. Background Technology

[0002] Power devices are a crucial component of modern power electronic systems. They primarily refer to electronic components designed to handle high voltage and high current, achieving power conversion and control, such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), IGBTs (Insulated-Gate Bipolar Transistors), and power diodes. These devices feature high efficiency, low loss, and excellent switching characteristics, and are widely used in motor control, solar photovoltaics, and new energy vehicles. However, in practical applications, these devices may face faults such as overcurrent, overvoltage, and short circuits, causing excessively high temperatures. This can lead to serious consequences such as performance degradation, reduced lifespan, or even damage. Therefore, the heat dissipation design of power devices is of paramount importance.

[0003] When the aforementioned faults occur, the heat dissipation requirements of power devices will be higher, necessitating more effective heat dissipation methods, such as using cooling fans, heat sinks, or cooling systems. While power devices themselves can dissipate heat sufficiently during normal operation, prolonged use of cooling fans, heat sinks, or cooling systems in the circuit can lead to unnecessary power loss. Therefore, to avoid power-consuming components like cooling fans, heat sinks, or cooling systems in the circuit during normal operation, the cooling fan, heat sink, or cooling system should be switched on promptly when the temperature reaches a certain threshold range.

[0004] However, the current single-switch function cannot achieve the above-mentioned temperature-based access function. It requires the control switch to be combined with temperature monitoring instruments and control circuits, resulting in a complex circuit structure and high space occupancy.

[0005] To address the aforementioned operating conditions, a novel thermal trip switch has been invented. This switch is a sealed, integrated device, directly connected in series or parallel to a branch near the power device. When a circuit fault occurs, the heat generated by the power device causes the liquid, gas, or solid with a high coefficient of thermal expansion in the enclosed capsule, which is in direct contact with one of the conductors, to rapidly expand. The expanding capsule pushes one conductor to make contact with the other conductor, thereby connecting the circuit. When a fault occurs in the operating circuit of the power device, the thermal trip switch promptly activates the heat dissipation branch of the power device, cooling it down. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to set a normally open thermal trip switch, which is connected in series with the branch where the cooling fan, heat sink or cooling system is located, and then connected in parallel with the circuit near the power device, so that the thermal trip switch is located close to the power device; when the temperature of the power device reaches the designed warning threshold range, the thermal trip switch closes, conducts the branch where the cooling fan, heat sink or cooling system is located, and the cooling fan, heat sink or cooling system works to provide heat dissipation protection for the power device.

[0007] To solve the above-mentioned technical problems, the present invention provides a normally open thermal trip switch, comprising a housing with a cavity, a first conductor and a second conductor that are insulated from each other, and a limiting member; the first conductor and the second conductor are respectively inserted into the housing, and one end of the first conductor and the second conductor outside the housing respectively serves as the connection end of the normally open thermal trip switch; the first conductor located inside the housing is elastic, and the limiting member located inside the housing defines the initial position of the first conductor, so that the first conductor and the second conductor are insulated; the limiting member portion defining the first conductor is made of a low-melting-point material with a melting point lower than that of the housing material; when the temperature of the first conductor reaches the melting point of the low-melting-point material, the portion of the limiting member that contacts the first conductor softens or melts, releasing the limiting position of the first conductor; under its own elastic force, one end of the first conductor located inside the housing moves toward the second conductor and makes conductive contact with the second conductor to form a conductive series circuit; when the normally open thermal trip switch is working, current flows through the series circuit formed by the direct conductive contact of the first conductor and the second conductor.

[0008] Preferably, the limiting member includes a fixed base and a limiting rod connected to each other, the limiting rod is made of a low melting point material, the fixed base is fixed in the housing, and the limiting rod limits the initial position of the first conductor.

[0009] Preferably, a limiting protrusion is provided on the outer periphery of the limiting rod, and the end of the limiting rod away from the fixed seat is inserted into the first conductor. The limiting protrusion abuts against the first conductor to restrict its initial position. When the temperature rises to a threshold range, the limiting protrusion softens or melts, or the limiting rod softens or melts.

[0010] Preferably, the first conductor located in the housing is bent into an elastic cantilever structure. The limiting member allows the first conductor with the cantilever structure to rest on the inner wall of one side of the housing. One end of the second conductor is located above the inner wall of the opposite side of the housing. When the limiting member is released, one end of the first conductor is displaced from one side of the housing to the opposite side and makes conductive contact with one end of the second conductor.

[0011] Preferably, one end of the first conductor inside the housing has an arc-shaped structure that protrudes toward the second conductor.

[0012] Preferably, the limiting member causes the inner wall of the housing side where the first conductor is disposed to have a stepped structure, and the arc-shaped end of the first conductor is located above the highest step of the stepped structure.

[0013] Preferably, an indicator is provided in the shell wall in front of the displacement path of the first conductor inside the shell. One end of the indicator is located in the shell wall, and the other end is located on the displacement path of the first conductor. When the first conductor is displaced, it drives the indicator to displace, so that the end of the indicator facing the outside of the shell extends out of the shell wall and is located outside the shell.

[0014] Preferably, the indicator has a T-shaped structure, with one end of the T-shaped structure having a lateral feature located inside the housing.

[0015] Preferably, the outer periphery of the indicator is provided with a resilient barb structure, and the barb structure is interference-fitted with the shell wall of the housing.

[0016] Preferably, a heating resistor with current-limiting function is provided on the inner wall of one side of the housing constructed by the first conductor, the first conductor is disposed on the heating resistor, the limiting member passes through the first conductor and contacts the heating resistor, and the two ends of the heating resistor are electrically connected to the first conductor and the second conductor respectively to form a current-limiting circuit.

[0017] Preferably, one end of the first and second conductors located outside the housing is provided outside the housing as a connection end of a thermal trip switch in a patch, bent-out flat-out, or straight-out quick-connect manner.

[0018] Preferably, the housing includes a cover and a base, the base being located at the open end of the cover and closing the open end, and the cover and the base being connected and fixed by a snap-fit ​​mechanism.

[0019] The normally open thermal trip switch of this invention uses a low-melting-point material limiting member to restrict a cantilevered, elastic first conductor, thus insulating the first and second conductors. When the temperature of the first conductor inside the housing reaches the melting point of the low-melting-point material of the limiting member, the limiting member softens or melts, losing its positional constraint on the first conductor. The first conductor then displaces under its own elastic force and makes conductive contact with the second conductor. The structure is simple, the response is rapid, and as a simple single device, the normally open thermal trip switch is easily integrated into the circuit containing a cooling fan, radiator, or cooling system without requiring additional complex control circuitry. When the thermal trip switch is placed near a power device, its operation is directly related to changes in the power device's temperature and the current changes in the circuit containing the power device. Therefore, when used for power device protection, the thermal trip switch is connected in series in the circuit containing the cooling fan, radiator, or cooling system, and then the circuit containing the cooling fan, radiator, or cooling system connected in series with the thermal trip switch is connected in parallel in the circuit containing the power device. This proximity of the thermal trip switch to the power device achieves power device protection.

[0020] The normally open thermal trip switch of the present invention is low in cost and can effectively protect power devices and improve their service life. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a normally open thermal trip switch in its initial state.

[0022] Figure 2 yes Figure 1 A side view structural diagram.

[0023] Figure 3 yes Figure 1 A schematic diagram of the structure after the action.

[0024] Figure 4 yes Figure 1 A schematic diagram of the structure after the action, showing the melting of the limiting protrusion.

[0025] Figure 5 yes Figure 1 A schematic diagram showing the structure after the action, in which the limit rod is completely melted.

[0026] Figure 6 This is a structural diagram of the snap-fit ​​structure between the cover and the base.

[0027] Figure 7 This is a structural diagram of the initial state with indicators set.

[0028] Figure 8 This is a structural diagram showing the action after the indicator is set.

[0029] Figure 9 yes Figure 1 A schematic diagram of a structure with a heating resistor added on top of the basic structure.

[0030] Figure 10 yes Figure 7 A schematic diagram of a structure with a heating resistor added on top of the basic structure.

[0031] Figure 11 This is a schematic diagram of a thermal trip switch with a bent, flat-out connection.

[0032] Figure 12 This is a schematic diagram of a thermal trip switch with a direct-out quick-connect structure.

[0033] Figure label:

[0034] 1. Cover body, 11. Snap-in hole, 2. Base, 21. Snap-in hole, 22. First conductor, 3. One end of the first conductor located outside the housing, 31. One end of the first conductor located inside the housing, 32. Second conductor, 4. One end of the second conductor located outside the housing, 41. One end of the second conductor located inside the housing, 42. Fixing seat of the limiting member, 51. Limiting rod of the limiting member, 52. Limiting protrusion, 521. Indicator, 6. Heating resistor, 7. Detailed Implementation

[0035] The normally open thermal trip switch of the present invention includes a housing with a cavity, a first conductor and a second conductor that are insulated from each other, and a limiting member. The first conductor and the second conductor are respectively disposed in the housing. One end of the first conductor and the second conductor outside the housing serves as the connection end of the normally open thermal trip switch. The first conductor located inside the housing is elastic. The limiting member located inside the housing defines the initial position of the first conductor, so that the first conductor and the second conductor are insulated from each other. The limiting member portion defining the first conductor is made of a low-melting-point material with a melting point lower than that of the housing material. When the temperature of the first conductor reaches the melting point of the low-melting-point material, the portion of the limiting member that contacts the first conductor softens or melts, releasing the limiting position of the first conductor. Under its own elastic force, one end of the first conductor located inside the housing moves toward the second conductor and makes conductive contact with the second conductor to form a conductive series circuit. When the normally open thermal trip switch is working, the current flows through the series circuit formed by the direct conductive contact between the first conductor and the second conductor.

[0036] The following describes preferred embodiments in detail with reference to the accompanying drawings. The directional terms used are for reference only and do not constitute a limitation on the technical solutions of this invention.

[0037] See Figures 1 to 3A normally open thermal trip switch mainly includes a housing, a first conductor, a second conductor, and a limiting component. The housing is made of insulating material and includes a cover 1 and a base 2. The cover 1 is a cap-like structure with one open end and one closed end. The base 2 is positioned at the open end of the cover 1 and closes the open end, forming a relatively sealed housing with a cavity inside. The base 2 is a stepped structure with a certain thickness. The thicker end of the base 2 extends and fully fits the inner wall of the cover 1, while the thinner end facing the inside of the housing is arc-shaped. The base 2 has a stepped structure facing the inner surface of the cover 1. A borrow hole 21 is provided on the inner surface of the base 2. The side walls of the base 2 and the cover 1 are provided with a snap-fit ​​structure. The base 2 is connected and fixed to the cover 1 by snap-fit, for example: see... Figure 6 A protruding snap-fit ​​protrusion 22 is provided on the side wall of the base 2 that mates with the cover 1, and a snap-fit ​​hole 11 is provided on the corresponding side wall of the cover 1. During assembly, the snap-fit ​​protrusion 22 of the base 2 snaps into the snap-fit ​​hole 11 of the cover 1, forming a fixed connection. The cover 1 and the base 2 can also be connected and fixed by bolts, rivets, laser welding or adhesive bonding.

[0038] The first conductor 3 passes between the thinner end of the cover 1 and the base 2. One end 31 of the first conductor 3, located outside the housing, is mounted on the outer surface of the base 2 as one of the connection terminals of a normally open thermal trip switch. The portion of the first conductor 3 inside the housing is bent along the arc-shaped end of the base 2, forming a cantilever structure with a certain degree of elasticity. One end 32 of the cantilevered first conductor 3 can contact the top of the cover 1 without external force or its own elasticity. The end 32 of the first conductor 3 inside the housing is bent into an arc-shaped structure protruding towards the top of the cover 1. Under the limiting action of the limiting member 5, the portion of the first conductor 3 inside the housing is fitted against the inner surface of the base 2, so that one end 32 of the first conductor is above the highest step surface of the base 2, and the first conductor 3 and the second conductor 4 are insulated from each other. When the limiting member 5 is removed, the cantilevered end 32 of the first conductor 3 makes conductive contact with one end of the second conductor 4 under its own elasticity. The advantage of setting one end 32 of the first conductor 3 as a convex arc-shaped structure is that it shortens the contact stroke between the first conductor and the second conductor, thereby shortening the contact time and improving contact reliability. A limiting hole is opened at the position of the first conductor 3 corresponding to the borrow hole 21 of the base 2.

[0039] The second conductor 4 passes between the base 2 (opposite to the first conductor 3) and the inner wall of the cover 1, allowing one end of the second conductor 4 inside the housing to be bent and fixed to the top inner surface of the cover 1. The other end 41 of the second conductor 4 outside the housing is attached to the outer surface of the base 2 as another connection point for a normally open thermal trip switch. When the first conductor 3 inside the housing loses the restraint of the limiting member 5, one end 32 of the first conductor 3 moves towards the top of the cover 1 under elastic force, making conductive contact with one end 42 of the second conductor 4.

[0040] A limiting member 5 is disposed on the top side of the cover 1 inside the housing, opposite to the second conductor 4. The limiting member 5 includes a fixing seat 51 and a limiting rod 52. The fixing seat 51 is fixed to the cover 1 by means of adhesive, bolts, etc. The limiting rod 52 is disposed perpendicular to the top of the cover 1. A limiting protrusion 521 is provided on the outer peripheral surface of the limiting rod 52 near the free end. The limiting rod 52 passes through the limiting hole on the first conductor 3 and is located in the borrow hole of the base 2. The limiting protrusion on the limiting rod 52 presses against the outer periphery of the limiting hole of the first conductor 3, pressing the first conductor 3 tightly against the inner surface of the base 2.

[0041] The limiting rod 52 is made of a low-melting-point material. Here, "low-melting-point" refers to a material with a lower melting point than the materials of the shell structure. Specifically, the melting point of the limiting rod 52 is lower than that of the cover 1 and base 2. This ensures that the shell structure maintains its original structure and strength even when the limiting rod 52 softens or melts. For example, the limiting rod may be made of low-melting-point plastic, such as PP (polypropylene), with a melting point of approximately 190 degrees Celsius. The shell (cover and base) may be made of nylon, with a melting point of approximately 280 degrees Celsius. Even when the limiting rod melts, the shell will still maintain its original structure and strength. When the temperature of the first conductor 3 increases, the melting point of the limiting rod 52 will be affected. (See [reference needed]). Figure 4 The limiting protrusion 521 melts, and the limiting rod 52 softens, partially melts, or completely melts. See below. Figure 5 When the limiting rod 52 is completely melted, it loses its pressure on the first conductor. Under the action of the elastic force, the first conductor 3 moves towards the top of the cover 1 and makes conductive contact with the second conductor 4, causing the normally open thermal trip switch to close. When the limiting rod 52 softens or melts, the cover 1 and the base 2 remain unchanged and will not soften or melt.

[0042] Working principle:

[0043] Under normal operating conditions, the first conductor 3 and the second conductor are insulated, and the thermal trip switch is normally open.

[0044] When the temperature at the first conductor of the thermal trip switch reaches the melting point of the material of the limit rod, the limiting protrusion of the limit rod melts, the limit rod softens or melts, the first conductor 3 is released from the limit, and the first conductor 3 is displaced under the action of elastic force to make conductive contact with the second conductor 4, so that the thermal trip switch is closed.

[0045] In use, the normally open thermal trip switch is connected in series in the circuit where the cooling fan, radiator, or cooling system is located. The normally open thermal trip switch is positioned close to the power device. When a fault current occurs in the circuit where the power device is located, the temperature of the thermal trip switch rises, the limiting protrusion of the limiting member melts, and the limiting rod softens or melts, releasing the limiting of the first conductor 3. The first conductor 3 is displaced under the action of elastic force and makes conductive contact with one end of the second conductor 4 inside the housing, causing the thermal trip switch to close. This connects the circuit where the cooling fan, radiator, or cooling system is located, and the cooling fan, radiator, or cooling system starts to work, dissipating heat for the power device and protecting the power device.

[0046] In other embodiments, an indicator 6 may also be provided to indicate to the operator that the thermal trip switch has been activated. Figure 1 Based on this, an indicator 6 is installed on one side of the top of the cover 1 where the second conductor 4 is located, see [reference]. Figures 7 to 8 A mounting hole is provided at the top of the cover 1, through which the second conductor 4 passes. The indicator 6 is mounted in the mounting hole, with one end fixed in the mounting hole at the top of the cover 1 and the other end located in the cavity of the housing. One end of the indicator 6 located in the housing contacts one end 32 of the first conductor 3 and the sidewall of the base 2, respectively. To further define the initial position of the indicator 6, a resilient barb structure (not shown) is provided on the outer periphery of the end of the indicator 6 located in the mounting hole, and the resilient barb structure is interference-fitted with the mounting hole. The indicator 6 is configured as an inverted "T" shape, with the wider end of the inverted "T" shape located in the housing. When the indicator 6 is displaced towards the outside of the housing, the wider end is engaged with the inner wall of the housing, preventing it from completely detaching from the housing. In some embodiments, a retaining spring is provided on the indicator 6.

[0047] When the first conductor 3 moves toward one end of the second conductor 4 at the top of the cover 1, the indicator 6 moves toward the outside of the housing. The indicator 6 overcomes the constraint of the barbed structure and extends out of the outer surface of the housing wall, indicating to the operator that the normally open thermal trip switch has been activated and that a fault has occurred in the circuit containing the power device. After the indicator 6 is activated, the elastic barbed structure moves to the outside of the housing, forming a termination position and preventing the indicator 6 from re-entering the housing.

[0048] In other embodiments, to improve the response speed of the normally open thermal trip switch, in Figure 1 and Figure 7Based on this, a heating resistor 7 is provided on the base 2 corresponding to the limiting rod 52 to accelerate heat accumulation. Simultaneously, the heating resistor 7 serves as a current-limiting component. The heating resistor can be a finished surface-mount resistor or a resistor in other package forms. See [link / reference] Figures 9 to 10 A heating resistor 7 is installed on the base 2. The first conductor 3, located in the housing, is positioned on the heating resistor 7. The end of the limiting rod 52 passes through the first conductor 3 and is positioned on the heating resistor 7. The two ends of the heating resistor 7 are electrically connected to the first conductor and the second conductor, respectively. The connection can be made by welding, conductive contact, or other conductive connection methods. The heating resistor 7 forms a current-limiting circuit by conductively connecting the first conductor 3 and the second conductor 4. Because the resistance of the heating resistor 7 is much greater than the resistance of the first conductor and the second conductor, the current flowing through the heating resistor is very small. The small current flowing through the heating resistor cannot make the cooling fan, radiator, or cooling system work. In other words, under normal operating conditions, the circuit containing the cooling fan, radiator, or cooling system is not conductive. By setting the heating resistor, the limiting rod 52 can be heated. The heat energy generated by the power device, combined with the heating of the heating resistor, can quickly melt the limiting protrusion, soften or melt the limiting rod, and shorten the response time of the conductive contact between the first conductor and the second conductor.

[0049] Figures 9 to 10 Working principle:

[0050] The thermal trip switch is connected in series in the circuit containing the cooling fan, radiator, or cooling system. The circuit containing the cooling fan, radiator, or cooling system with the thermal trip switch connected in series is connected in parallel in the circuit containing the power device. The thermal trip switch is placed close to the power device.

[0051] During normal operation, due to the high resistance of the heating resistor, the current in the current limiting circuit where the heating resistor of the thermal trip switch is located is very small. The temperature generated is insufficient to soften the limit protrusion of the limit rod. The first conductor and the second conductor do not have direct conductive contact, and the very small current cannot make the cooling fan, radiator or cooling system work.

[0052] When a fault current occurs in the circuit containing the power device, the current through the thermal trip switch increases, causing the temperature of the heating resistor to rise rapidly. Simultaneously, the temperature generated by the power device also rises, causing the limiting protrusion of the limit rod to melt quickly. Under the action of the elastic force, the first conductor 3 makes conductive contact with the second conductor 4, closing the thermal trip switch. This connects the circuit containing the cooling fan, radiator, or cooling system, allowing almost all the current to flow through the first conductor 3 and the second conductor 4. The cooling fan, radiator, or cooling system then operates normally, dissipating heat for the power device, thus achieving thermal protection. Alternatively, when the current in the circuit containing the power device is normal, but the temperature of the power device rises to a threshold range, the limiting protrusion of the limit rod melts, closing the thermal trip switch. This connects the circuit containing the cooling fan, radiator, or cooling system, allowing the cooling fan, radiator, or cooling system to operate normally, dissipating heat for the power device, thus achieving thermal protection.

[0053] Connecting a heating resistor can improve the response speed of the thermal trip switch and shorten the response time.

[0054] Figure 1 One end of the first and second conductors, serving as the connection terminals of the thermal trip switch, is a surface-mount structure. In other embodiments, it can also be a bent, flat-out structure. See [link / reference needed]. Figure 11 It can also be a direct-output quick-connect structure, see [link / reference] Figure 12 The thermal trip switch is designed to adapt to different usage environments, making it suitable for a wider range of applications.

[0055] The advantage of the normally open thermal trip switch of the present invention is that it is a single device with a simple structure. It is only connected to a cooling fan, heat sink or cooling system when the device power cannot be dissipated normally by itself during fault circuit current, thereby reducing power loss.

Claims

1. A normally open thermal trip switch, characterized in that, The device includes a housing with a cavity, a first conductor and a second conductor that are insulated from each other, and a limiting member. The first conductor and the second conductor are respectively inserted into the housing. One end of the first conductor and the second conductor outside the housing serves as the connection end of the normally open thermal trip switch. The first conductor inside the housing is elastic. The limiting member inside the housing defines the initial position of the first conductor, making the first conductor and the second conductor insulated from each other. The limiting member defining the first conductor is made of a low-melting-point material with a melting point lower than that of the housing material. When the temperature of the first conductor reaches the melting point of the low-melting-point material, the portion of the limiting member that contacts the first conductor softens or melts, releasing the limiting position of the first conductor. Under its own elastic force, one end of the first conductor inside the housing moves toward the second conductor and makes conductive contact with the second conductor, forming a conductive series circuit. When the normally open thermal trip switch is working, current flows through the series circuit formed by the direct conductive contact between the first conductor and the second conductor.

2. The normally open thermal trip switch according to claim 1, characterized in that, The limiting component includes a fixed base and a limiting rod connected to each other. The limiting rod is made of a low melting point material. The fixed base is fixed in the housing. The limiting rod limits the initial position of the first conductor.

3. The normally open thermal trip switch according to claim 2, characterized in that, A limiting protrusion is provided on the outer periphery of the limiting rod. The end of the limiting rod away from the fixed seat is inserted into the first conductor. The limiting protrusion abuts against the first conductor to limit its initial position. When the temperature rises to a threshold range, the limiting protrusion softens or melts, or the limiting rod softens or melts.

4. The normally open thermal trip switch according to claim 3, characterized in that, The first conductor located in the housing is bent into an elastic cantilever structure. The limiting member allows the first conductor, which has a cantilever structure, to rest on the inner wall of one side of the housing. One end of the second conductor is located above the inner wall of the opposite side of the housing. When the limiting member is released, one end of the first conductor is displaced from one side of the housing to the opposite side and makes conductive contact with one end of the second conductor.

5. The normally open thermal trip switch according to claim 4, characterized in that, One end of the first conductor inside the housing has an arc-shaped structure that protrudes toward the second conductor.

6. The normally open thermal trip switch according to claim 5, characterized in that, The limiting member causes the inner wall of the housing on one side of the first conductor to have a stepped structure, and the arc-shaped end of the first conductor is located above the highest step of the stepped structure.

7. The normally open thermal trip switch according to any one of claims 1 to 6, characterized in that, An indicator is provided in the shell wall in front of the displacement path of the first conductor inside the shell. One end of the indicator is located in the shell wall, and the other end is located on the displacement path of the first conductor. When the first conductor is displaced, it drives the indicator to displace, so that the end of the indicator facing the outside of the shell extends out of the shell wall and is located outside the shell.

8. The normally open thermal trip switch according to claim 7, characterized in that, The indicator has a T-shaped structure, with one end of the T-shaped structure having a lateral feature located inside the housing.

9. The normally open thermal trip switch according to claim 7, characterized in that, The indicator is provided with a flexible barb structure on its outer periphery, and the barb structure is interference-fitted with the shell wall of the housing.

10. The normally open thermal trip switch according to any one of claims 1 to 6, characterized in that, A heating resistor with current-limiting function is provided on the inner wall of one side of the housing constructed by the first conductor. The first conductor is disposed on the heating resistor. The limiting member passes through the first conductor and contacts the heating resistor. The two ends of the heating resistor are electrically connected to the first conductor and the second conductor respectively to form a current-limiting circuit.

11. The normally open thermal trip switch according to any one of claims 7, characterized in that, A heating resistor with current-limiting function is provided on the inner wall of one side of the housing constructed by the first conductor. The first conductor is disposed on the heating resistor. The limiting member passes through the first conductor and contacts the heating resistor. The two ends of the heating resistor are electrically connected to the first conductor and the second conductor respectively to form a current-limiting circuit.

12. The normally open thermal trip switch according to claim 1, characterized in that, One end of the first and second conductors located outside the housing is provided outside the housing as a connection terminal of the thermal trip switch in a patch type, a bent flat type, or a straight quick-connect type.

13. The normally open thermal trip switch according to claim 1, characterized in that, The housing includes a cover and a base. The base is located at the open end of the cover and closes the open end. The cover and the base are connected and fixed by a snap-fit ​​mechanism.

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