Normally open type thermal trip switch

Abstract

The utility model discloses a normally-open type thermal trip switch which comprises a shell, a first conductor, a second conductor and a limiting piece. The first conductor and the second conductor are respectively arranged in the shell in a penetrating manner, and the limiting piece is positioned in the shell to limit the initial position of the elastic first conductor, so that the first conductor and the second conductor are arranged in an insulating manner; the limiting part for limiting the first conductor is made of a low-melting-point material, when the temperature rises to a threshold value range, the part, abutting against the first conductor, of the limiting part is softened or melted, limiting of the first conductor is relieved, and under the action of the elastic force of the limiting part, one end, located in the shell, of the first conductor moves to make conductive contact with the second conductor to form a conducted series circuit. When the normally-open thermal trip switch works, current flows through a series circuit formed by direct conductive contact of the first conductor and the second conductor. The normally-open type thermal trip switch is simple in structure, and the heat dissipation component can be quickly connected into a circuit to protect a power device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power control and electric vehicles, in particular to a device for protecting power devices in the event of a fault current. BACKGROUND

[0002] Power devices are an important component of modern power electronic systems, mainly referring to electronic components designed to handle high voltage and large current, achieve power conversion and control, such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), power diode, etc. They have high efficiency, low loss and good switching characteristics, and are widely used in motor control, solar photovoltaic, new energy vehicles, etc. However, these devices may face overcurrent, overvoltage and short circuit failures in actual application, causing the temperature of the power device to be too high, thereby causing performance degradation, reduced life and even damage, etc. Therefore, the heat dissipation design of the power device is crucial.

[0003] When the above faults occur, the heat dissipation requirement of the power device will be higher, and more effective heat dissipation methods are needed, such as using heat dissipation fans, heat sinks or cooling systems, etc. When the power device is working normally, its own heat dissipation is sufficient, and the heat dissipation fan, heat sink or cooling system is connected to the circuit for a long time, which will cause unnecessary power loss. Therefore, in order to avoid connecting the power loss components such as heat dissipation fan, heat sink or cooling system in the circuit when working normally, the heat dissipation fan, heat sink or cooling system needs to be connected in the circuit in time through the switch when the temperature reaches a certain threshold range.

[0004] However, the current single switch function cannot realize the above temperature access function, and needs to control the switch in combination with temperature monitoring instruments and control circuits to realize, resulting in complex circuit structure and high space occupancy.

[0005] In view of the above working conditions, a new type of thermal trip switch is invented. The switch is a closed integrated device, which is directly connected in series or parallel to the branch near the power device. When the circuit fails, the high thermal expansion coefficient liquid or gas or solid in the closed capsule directly contacted with one of the conductors expands rapidly due to the heat generated by the power device. The expanded closed capsule pushes one of the conductors to move and contact with the other conductor, thereby conducting the circuit. When the working circuit of the power device fails, the thermal trip switch operates in time to connect the heat dissipation branch of the power device, thereby cooling the power device. SUMMARY

[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 in the shell is in an arc-shaped structure protruding towards the second conductor.

[0012] Preferably, the limiting member makes the inner wall of the side of the shell where the first conductor is arranged in a stepped structure, and the end of the first conductor in the arc-shaped structure is above the highest step of the stepped structure.

[0013] Preferably, an indicator is arranged in the shell wall in front of the displacement path of the first conductor in the shell, one end of the indicator is in the shell wall and the other end is in the displacement path of the first conductor, when the first conductor is displaced to drive the indicator to displace, the end of the indicator protruding out of the shell wall towards the outside of the shell is in the outside of the shell.

[0014] Preferably, the indicator is in a T-shaped structure, and the end of the T-shaped structure with a transverse feature is in the inside of the shell.

[0015] Preferably, the outer periphery of the indicator is provided with a springy barb structure, and the barb structure is in interference fit with the shell wall.

[0016] Preferably, a heating resistor with current limiting effect is arranged in the inner wall of the side of the shell where the first conductor is arranged, the first conductor is arranged on the heating resistor, the limiting member is in contact with the heating resistor through the first conductor, and the two ends of the heating resistor are respectively in conductive connection with the first conductor and the second conductor to form a current limiting circuit.

[0017] Preferably, one end of the first conductor and the second conductor outside the shell is arranged outside the shell as a connection end of a thermal trip switch in a patch type, a bent flat type or a straight out quick plug type.

[0018] Preferably, the shell comprises a cover and a base, the base is located at and closes the open end of the cover, and the cover and the base are connected and fixed in a snap-fit manner.

[0019] The low-melting material limiting piece limits the first conductor with elasticity in a cantilever structure, so that the first conductor and the second conductor are insulated, when the temperature of the first conductor in the shell reaches the melting point of the low-melting material of the limiting piece, the low-melting material limiting piece softens or melts, loses the position limitation to the first conductor, and the first conductor is displaced under the action of its own elasticity and is in conductive contact with the second conductor. The structure is simple, the response is rapid, and the normally open thermal trip switch is a simple single device, which is very convenient to be connected into the circuit where the heat dissipation fan, radiator or cooling system is located, and a complex control circuit does not need to be additionally designed, when the thermal trip switch is arranged near the power device, the action of the thermal trip switch is directly related to the temperature change of the power device and the current change of the circuit where the power device is located. Therefore, when used for power device protection, the thermal trip switch is connected in series in the circuit where the heat dissipation fan, radiator or cooling system is located, then the circuit where the heat dissipation fan, radiator or cooling system connected in series with the thermal trip switch is connected in parallel in the circuit where the power device is located, so that the thermal trip switch is close to the power device, and the power device protection is realized.

[0020] The normally open thermal trip switch has low cost and can effectively protect the power device and prolong the service life of the power device. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a sectional view of the normally open thermal trip switch in an initial state.

[0022] Figure 2 is Figure 1 a side view of the normally open thermal trip switch.

[0023] Figure 3 is Figure 1 a structure schematic diagram after action.

[0024] Figure 4 is Figure 1 a structure schematic diagram after action, and the limiting protrusion is melted.

[0025] Figure 5 is Figure 1 a structure schematic diagram after action, and the limiting rod is completely melted.

[0026] Figure 6 is a structure schematic diagram of the buckle structure of the cover body and the base.

[0027] Figure 7 is a structure schematic diagram of the initial state of the normally open thermal trip switch provided with an indicator.

[0028] Figure 8 is a structure schematic diagram of the normally open thermal trip switch provided with an indicator after action.

[0029] Figure 9 isFigure 1 Structure diagram of the structure of setting heating resistor on the base.

[0030] Figure 10 Figure 7 Structure diagram of the structure of setting heating resistor on the base.

[0031] Figure 11 Structure diagram of the structure of the connecting end of the thermal release switch being the structure of bending and flat out.

[0032] Figure 12 Structure diagram of the structure of the connecting end of the thermal release switch being the structure of straight out and quick plug.

[0033] Reference signs:

[0034] Cover body 1, buckle hole 11, base 2, position hole 21, buckle protrusion 22, first conductor 3, one end 31 of the first conductor located outside the shell, one end 32 of the first conductor located inside the shell, second conductor 4, one end 41 of the second conductor located outside the shell, one end 42 of the second conductor located inside the shell, fixing seat 51 of the limiting piece, limiting rod 52 of the limiting piece, limiting protrusion 521, indicator 6, heating resistor 7. DETAILED DESCRIPTION

[0035] The normally open thermal release switch of the application comprises a shell with a cavity, a first conductor and a second conductor which are insulated from each other, and a limiting piece; the first conductor and the second conductor are respectively arranged in the shell, one end of the first conductor and one end of the second conductor outside the shell are respectively used as the connecting end of the normally open thermal release switch, the first conductor inside the shell is elastic, the limiting piece inside the shell limits the initial position of the first conductor, and the first conductor and the second conductor are arranged in an insulating manner; the limiting piece limiting the first conductor is made of a low-melting-point material whose melting point is lower than that of the shell; when the temperature of the first conductor reaches the melting point of the low-melting-point material, the part of the limiting piece in contact with the first conductor softens or melts, the limiting of the first conductor is released, and under the action of its own elastic force, one end of the first conductor inside the shell is displaced towards the second conductor to form a conductive contact with the second conductor to form a series circuit in conduction; when the normally open thermal release switch works, the current flows through the series circuit formed by the conductive contact between the first conductor and the second conductor.

[0036] The preferred embodiments are specifically described below in combination with the drawings. The orientation words involved only refer to the orientation shown in the drawings and do not constitute a limitation on the technical scheme of the application.

[0037] Reference Figures 1 to 3 ​The utility model relates to a normally open thermal trip switch, which mainly comprises a shell, a first conductor, a second conductor and a limiting piece. The shell is made of insulating material and comprises a cover and a base. The cover is a cap-shaped structure with one end open and the other end closed. The base is arranged at the open end of the cover and closes the open end of the cover to form a relatively sealed shell with a cavity. The base is a stepped structure with a certain thickness. The end of the base with a relatively large thickness extends to completely match the inner wall of the cover. The end of the base with a relatively small thickness is arranged in an arc shape towards the inside of the shell. The inner surface of the base is arranged in a stepped structure towards the cover. A limiting hole is arranged on the inner surface of the base. The side wall of the base and the cover is arranged with a buckle structure. The base is connected and fixed to the cover in a buckle manner, for example, referring to Figure 6 A protruding buckle block is arranged on the side wall of the base matched with the cover. A buckle hole is arranged on the corresponding side wall of the cover. When assembled, the buckle block of the base is buckled in the buckle hole of the cover to form a fixed connection. The cover and the base can also be connected and fixed by means of bolts, rivets, laser welding or glue.

[0038] The first conductor is arranged between the cover and the base with a relatively small thickness. One end of the first conductor outside the shell is arranged on the outer surface of the base in a patch type structure as one of the connection ends of the normally open thermal trip switch. The part of the first conductor inside the shell is arranged in a cantilever type structure with a certain elasticity after being bent along the arc-shaped end of the base inside the shell. One end of the first conductor arranged in the cantilever type structure can contact the top of the cover without external force limitation and under the action of its own elasticity. One end of the first conductor inside the shell is bent to form an arc-shaped structure protruding towards the top of the cover. Under the limiting action of the limiting piece, the part of the first conductor inside the shell is arranged to fit the inner surface of the base. One end of the first conductor is arranged above the highest step surface of the base to make the first conductor and the second conductor arranged in an insulating manner. When the limiting piece loses the action, one end of the first conductor arranged in the cantilever type structure is in conductive contact with one end of the second conductor under the action of its own elasticity. The first conductor arranged in the arc-shaped structure has the advantages of shortening the contact stroke of the first conductor and the second conductor, thereby shortening the contact time and improving the contact reliability. A limiting hole is arranged at the position of the limiting hole of the base corresponding to the first conductor.

[0039] Second conductor 4, from the other side of the base 2 with the first conductor 3 with the complete cooperation of the inner wall of the cover 1 and the inner wall of the cover 1 between the end and the inner wall of the cover 1, the end of the second conductor 4 located in the shell can be bent to the top of the inner surface of the cover 1 and fixed, the end 41 of the second conductor 4 located outside the shell is arranged on the outer surface of the base 2 as another connecting end of the normally open thermal trip switch in the form of a patch. When the first conductor 3 in the shell loses the limit of the limiting part 5, the end 32 of the first conductor 3 is displaced under the action of the elastic force towards the top of the cover 1, and the end 32 of the first conductor 3 is in conductive contact with the end 42 of the second conductor 4.

[0040] Limiting part 5, arranged on the top of the cover 1 in the shell opposite to one side of the second conductor 4. The limiting part 5 includes a fixed seat 51 and a limiting rod 52, and the fixed seat 51 is fixed on the cover 1 by means of adhesion, bolt or the like. The limiting rod 52 is arranged vertically on the top of the cover 1, and a limiting protrusion 521 is arranged on the outer circumferential surface of the limiting rod 52 near the free end position. The limiting rod 52 passes through the limiting hole on the first conductor 3 and is located in the limiting hole of the base 2, and the limiting protrusion on the limiting rod 52 is pressed on the outer circumference of the limiting hole of the first conductor 3 to press the first conductor 3 tightly on the inner surface of the base 2.

[0041] The material of the limiting rod 52 is a low melting point material. Here, the low melting point material is relative to the melting point of the material of the shell structure, that is, the melting point of the material of the limiting rod 52 is lower than the melting point of the material of the cover 1 and the base 2, which ensures that when the limiting rod 52 softens or melts, the shell structure remains unchanged in original structure and strength. For example, the limiting rod is made of low melting point plastic, such as PP (polypropylene) material, with a melting point of about 190 degrees, and the shell (cover and base) is made of nylon material, with a melting point of about 280 degrees. When the limiting rod melts, the shell remains unchanged in original structure and strength. When the temperature of the first conductor 3 rises to the melting point of the limiting rod 52, the limiting protrusion 521 melts, the limiting rod 52 softens, partially melts or completely melts, the limiting rod 52 completely melts, loses the pressing of the first conductor, the first conductor 3 is displaced under the action of the elastic force towards the top of the cover 1, and is in conductive contact with the second conductor 4, so that the normally open thermal trip switch is closed. When the limiting rod 52 softens or melts, the cover 1 and the base 2 remain unchanged and will not soften or melt. Figure 4 Figure 5 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] In normal working state, 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. The resilient barb structure is interference-fitted with the mounting hole. The indicator 6 is configured as an inverted "T" shape. The wider end of the inverted "T" shape is 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 driving 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 at one end, 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 7On the basis of the above, a heating resistor 7 is arranged on the base 2 corresponding to the limiting rod 52, which is used to accelerate heat accumulation, and the heating resistor 7 also serves as a current-limiting component. The heating resistor can be a finished chip resistor or a resistor in other packaging forms. Referring to Figures 9 to 10 The heating resistor 7 is arranged on the base 2, the first conductor 3 in the shell is arranged above the heating resistor 7, and the end of the limiting rod 52 passes through the first conductor 3 above the heating resistor 7. The two ends of the heating resistor 7 are respectively conductively connected with the first conductor and the second conductor, and the connection mode can be connected by welding, conductive contact or other conductive connection modes. The heating resistor 7 is conductively connected between the first conductor 3 and the second conductor 4 to form a current-limiting circuit. Since the resistance of the heating resistor 7 is much larger than the resistance of the first conductor and the second conductor, the current flowing through the heating resistor is very small, and the small current flowing through the heating resistor cannot make the heat dissipation fan, radiator or cooling system work. In normal working condition, the circuit in which the heat dissipation fan, radiator or cooling system is located is not conductive. By arranging the heating resistor, the limiting rod 52 can be heated, and the heat energy generated by the power device combined with the heating of the heating resistor can quickly melt the limiting protrusion, and the limiting rod is softened or melted, thereby shortening 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 arranged in the circuit of the heat dissipation fan, radiator or cooling system, the circuit of the heat dissipation fan, radiator or cooling system with the thermal trip switch in series is connected in parallel with the circuit of the power device, and the thermal trip switch is arranged close to the power device.

[0051] In normal working condition, since the resistance of the heating resistor is very large, the current of the current-limiting circuit in which the heating resistor of the thermal trip switch is located is very small, and the temperature generated thereby is not enough to soften the limiting protrusion of the limiting rod. The first conductor and the second conductor are not directly conductively contacted, and the very small current cannot make the heat dissipation fan, radiator or cooling system work.

[0052] When the circuit where the power device is located fails, the current through the thermal trip switch increases, the temperature of the heating resistor rises rapidly, and the temperature of the power device also rises, causing the limiting protrusion of the limiting rod to melt rapidly. The first conductor 3 is in conductive contact with the second conductor 4 under the action of the elastic force, the thermal trip switch is closed, the circuit where the heat dissipation fan, radiator or cooling system is located is turned on, the current almost entirely flows through the first conductor 3 and the second conductor 4, and the heat dissipation fan, radiator or cooling system works normally to dissipate heat for the power device, thereby achieving heat dissipation protection of the power device. Alternatively, when the current of the circuit where the power device is located is normal, but the temperature of the power device rises to a threshold range, the limiting protrusion of the limiting rod melts, the thermal trip switch is closed, the circuit where the heat dissipation fan, radiator or cooling system is located is turned on, and the heat dissipation fan, radiator or cooling system works normally to dissipate heat for the power device, thereby achieving heat dissipation protection of the power device.

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

[0054] Figure 1 The first conductor and the second conductor are in a patch structure as one end of the connection end of the thermal trip switch, and in other embodiments, can be in a bent flat structure, refer to Figure 11 , and can be in a straight out quick plug structure, refer to Figure 12 . According to different use environments, corresponding design is performed, so that the thermal trip switch can adapt to more occasions.

[0055] The advantage of the normally open thermal trip switch of the application lies in that it is a single device and has a simple structure. Only when the fault circuit current is failed and the power of the device cannot rely on normal heat dissipation by itself, the heat dissipation fan, radiator or cooling system is accessed through the thermal trip switch, thereby reducing the power loss.

Claims

1. A normally open thermal trip switch, characterized by, The utility model provides a kind of constant-open thermal release switch, including the shell with cavity, mutually insulated first conductor and second conductor, limiting piece;The first conductor and second conductor are respectively threaded in the shell, and one end of the first conductor and second conductor outside the shell is respectively used as the connecting end of the constant-open thermal release switch, the first conductor in the shell has elasticity, and the limiting piece is located in the shell and forms the initial position limit of the first conductor, so that the first conductor and the second conductor are insulated;The part of the limiting piece that limits the first conductor is low-melting point material with melting point lower than the melting point of the shell material;When the temperature of the first conductor reaches the melting point of the low-melting point material, the part of the limiting piece that is in contact with the first conductor softens or melts, removes the limiting of the first conductor, and under the action of its own elastic force, the end of the first conductor in the shell is displaced towards the second conductor to form a conductive contact with the second conductor to form a series circuit, and when the constant-open thermal release switch works, the current flows through the series circuit formed by the direct conductive contact of the first conductor and the second conductor.

2. The normally open thermal trip switch of claim 1, wherein, The limiting piece includes a fixed seat and a limiting rod connected to each other, the limiting rod is made of low-melting point material, the fixed seat is fixed in the shell, and the limiting rod limits the initial position of the first conductor.

3. The normally open thermal trip switch of claim 2, wherein, A limiting protrusion is arranged on the outer periphery of the limiting rod, one end of the limiting rod away from the fixed seat is inserted into the first conductor, the limiting protrusion is in contact with the first conductor to limit the initial position thereof, and 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 of claim 3, wherein, The first conductor in the shell is bent to have a cantilever structure with elasticity, the limiting piece makes the first conductor in the cantilever structure rest on the inner wall of one side of the shell, and one end of the second conductor is located above the inner wall of the opposite side of the shell; when the limiting of the limiting piece is removed, one end of the first conductor is displaced from one side of the shell to the opposite side to conductively contact with one end of the second conductor.

5. The normally open thermal trip switch of claim 4, wherein, One end of the first conductor in the shell has an arc structure protruding towards the second conductor.

6. The normally open thermal trip switch of claim 5, wherein, The limiting piece makes the inner wall of one side of the shell where the first conductor is arranged have a stepped structure, and one end of the first conductor having the arc structure 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 arranged in the shell wall in front of the displacement path of the first conductor in 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 to drive the indicator to be displaced, the end of the indicator extending out of the shell wall towards the outside of the shell is located outside the shell.

8. The normally open thermal trip switch of claim 7, wherein, The indicator has a T-shaped structure, and one end of the T-shaped structure having a horizontal feature is located inside the shell.

9. The normally open thermal trip switch of claim 7, wherein, An elastic barb structure is arranged on the outer periphery of the indicator, and the barb structure is in interference fit with the shell wall.

10. The normally open thermal trip switch according to any one of claims 1 to 6, wherein The first conductor is arranged on a heating resistor with current-limiting effect arranged on the inner wall of one side of the shell, the limiting member passes through the first conductor and contacts the heating resistor, and the two ends of the heating resistor are respectively connected with the first conductor and the second conductor to form a current-limiting circuit.

11. The normally open thermal trip switch of claim 7, wherein, The first conductor is arranged on a heating resistor with current-limiting effect arranged on the inner wall of one side of the shell, the limiting member passes through the first conductor and contacts the heating resistor, and the two ends of the heating resistor are respectively connected with the first conductor and the second conductor to form a current-limiting circuit.

12. The normally open thermal trip switch of claim 1, wherein, One end of the first conductor and the second conductor located outside the shell is arranged outside the shell as a connection end of the thermal trip switch in a patch type, a bent flat type or a straight out quick plug type.

13. The normally open thermal trip switch of claim 1, wherein, The shell comprises a cover and a base, the base is located at and closes the open end of the cover, and the cover and the base are fixedly connected in a buckle mode.

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