A small thermal protector for DC motor

Abstract

This utility model relates to the field of thermal protector technology, specifically to a small thermal protector for DC motors. It includes a housing with stationary contacts welded inside. A base plate is located below the housing, and a bimetallic strip is welded to the base plate. Iron nails and moving contacts are welded to both ends of the bimetallic strip. Insulating paper is installed between the base plate and the housing, forming insulation between them. A positive temperature coefficient thermistor is covered on the upper part of the housing. When the protector contacts are normally closed, current flows through the contacts to form a closed circuit. When the thermal protector operates under heat, the thermistor conducts at the instant the contacts open, forming a circuit. Due to the current shunting in the thermistor circuit, the arcing between the contacts is reduced when the protector opens, thus improving the protector's service life. This achieves low-arc disconnection for DC motor thermal protectors. After the circuit is formed, the thermistor continues to heat up, and its resistance value increases significantly, causing the thermistor circuit to be in an open state.

Description

Technical Field

[0001] This utility model relates to the field of thermal protector technology, and in particular to a small thermal protector for DC motors. Background Technology

[0002] In the field of motor protection, thermal protectors play a crucial role. Currently, various types of thermal protectors exist on the market, among which bimetallic strip thermal protectors are widely used. These protectors use a bimetallic strip at a constant temperature as the sensitive reacting element. When the temperature increases, heat is transferred to the bimetallic strip. When the predetermined temperature value is reached, the bimetallic strip quickly activates, causing the contacts to open and cutting off the circuit. When the temperature drops to the predetermined reset value, the bimetallic strip quickly recovers, causing the contacts to close and connecting the circuit, thus achieving the effect of protecting the circuit. This type of thermal protector has been successfully applied to AC motors. Because AC current has a natural current zero-crossing point, the arc is easily extinguished temporarily each time it crosses zero, requiring re-establishment. This limits the continuous accumulation of arc energy, allowing the thermal protector to effectively protect AC motors to a certain extent, preventing damage due to overheating, ensuring stable operation of the AC motor, and extending its service life. However, existing thermal protectors have many problems when applied to DC motors. Unlike AC current, DC current does not have a zero-crossing point. Once an arc forms, it continues to burn until the current is forcibly cut off, resulting in even greater arc energy.

[0003] When bimetallic strip thermal protectors are used on DC motors, severe arcing often causes the internal contacts to melt and stick together. This not only shortens the product's lifespan but also easily leads to the thermal protector's failure, preventing timely overheat protection of the DC motor. This poses a significant safety hazard to the normal operation of the DC motor, increases equipment maintenance costs and downtime, and impacts production efficiency.

[0004] Currently, there are some power failure protection devices applied to DC motors, such as vacuum arc extinguishing, inert gas arc extinguishing, arc blowing devices, arc extinguishing grooves, and increasing the thickness of the silver layer between contacts. However, these methods have problems such as low production efficiency, complex structure, and high production cost, making it difficult to promote and apply them on a large scale. Utility Model Content

[0005] The purpose of this invention is to provide a small thermal protector for DC motors, aiming to solve the technical problems of low production efficiency, complex structure and high production cost in the existing technology, which makes it difficult to promote and apply on a large scale.

[0006] To achieve the above objectives, this utility model employs a small thermal protector for DC motors, comprising a metal clip, a thermistor, a housing, a bimetallic strip, and a base plate. A stationary contact is provided on the inner top of the housing, and a moving contact is provided at one end of the bimetallic strip. The metal clip is slidably connected to the base plate and abuts against the lower end face of the base plate. The thermistor is disposed between the metal clip and the housing, and the bimetallic strip is disposed on the base plate. The housing is disposed on the base plate and covers the bimetallic strip.

[0007] The other end of the bimetallic strip is provided with an iron nail, the base plate is provided with a boss, and the bimetallic strip is set on the boss by the iron nail, and the moving contact is located below the stationary contact.

[0008] The outer shell has a first wire riveting groove at one end, and the bottom plate has a second wire riveting groove at one end, with both the first and second wire riveting grooves extending out of one end of the metal buckle.

[0009] The small thermal protector for DC motors also includes insulating paper with a through hole in the middle. The insulating paper is disposed on the contact surface between the housing and the base plate, and the bimetallic strip is located at the through hole.

[0010] The base plate has multiple positioning semicircular blocks symmetrically arranged below it. The metal buckle has guide grooves on both inner sides. Each guide groove has multiple positioning semicircular slots. The multiple positioning semicircular blocks are respectively held in place by the corresponding positioning semicircular slots through the corresponding guide grooves.

[0011] This utility model discloses a small thermal protector for DC motors, comprising a housing with stationary contacts welded inside. A base plate is located below the housing, and a bimetallic strip is welded to the base plate. A nail and a moving contact are welded to each end of the bimetallic strip, which is then welded to the base plate via the nail. Insulating paper is installed between the base plate and the housing, providing insulation. A positive temperature coefficient thermistor is covered on the upper part of the housing and fixed to the housing by metal clips. When the protector contacts are normally closed, current flows through the contacts to form a closed circuit. When the thermal protector operates under heat, the thermistor conducts at the instant the contacts open, forming a circuit. Due to the current shunting in the thermistor circuit, the arcing between the contacts is reduced when the protector opens, thus improving the protector's service life. This achieves low-arc disconnection for DC motor thermal protectors. After the circuit is formed, the thermistor continues to heat up, and its resistance increases significantly, causing the thermistor circuit to be in an open state. By connecting a temperature-dependent thermistor in parallel outside the protector housing, the thermal protector is applied to DC motors. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is an exploded view of the structure of a small thermal protector for DC motors according to this utility model.

[0014] Figure 2 This is a side cross-sectional view of the bimetallic strip in the closed state of the small thermal protector for DC motors according to this utility model.

[0015] Figure 3 This is a side cross-sectional view of the bimetallic strip in the open state of the small thermal protector for DC motors according to this utility model.

[0016] Figure 4 This is a schematic diagram of the outer casing of a small thermal protector for DC motors according to this utility model.

[0017] Figure 5 This is a schematic diagram of the base plate of a small thermal protector for DC motors according to this utility model.

[0018] Figure 6 This is a front view of the small thermal protector of the present invention applied to DC motors.

[0019] Figure 7 This is the utility model Figure 6 A cross-sectional view along line AA in the middle.

[0020] Figure 8 This is the utility model Figure 7 A magnified view of a section at point B.

[0021] 1-Outer shell, 11-First wire riveting groove, 2-Bimetallic strip, 3-Base plate, 31-Boss, 32-Second wire riveting groove, 4-Insulating paper, 5-Thermistor, 6-Metal buckle, 7-Moving contact, 8-Static contact, 9-Iron nail, 10-Positioning semicircular block, 11-Guide groove, 12-Positioning semicircular groove. Detailed Implementation

[0022] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0023] Please see Figures 1 to 8 This utility model provides a small thermal protector for DC motors, including a metal clip 6, a thermistor 5, a housing 1, a bimetallic strip 2, and a base plate 3. The inner top of the housing 1 is provided with a stationary contact 8, and one end of the bimetallic strip 2 is provided with a moving contact 7. The metal clip 6 is slidably connected to the base plate 3 and abuts against the lower end face of the base plate 3. The thermistor 5 is disposed between the metal clip 6 and the housing 1. The bimetallic strip 2 is disposed on the base plate 3, and the housing 1 is disposed on the base plate 3 and covers the bimetallic strip 2.

[0024] In this embodiment, a thermistor 5, which is positively correlated with temperature, is connected in parallel on the thermal protector housing 1. When the protector contacts are normally closed, current flows through the contacts to form a closed circuit. When the thermal protector is heated and operates, the thermistor 5 conducts and forms a circuit at the instant the contacts open. Due to the current shunting in the thermistor 5 circuit, the amount of arcing between the contacts when the protector is disconnected is reduced, thus improving the service life of the protector. After the circuit is formed, the thermistor 5 continues to heat up, and the resistance value increases significantly, causing the thermistor 5 circuit to be in an open state, thereby achieving low-arc disconnection of the DC motor thermal protector.

[0025] Furthermore, the other end of the bimetallic strip 2 is provided with an iron nail 9, the base plate 3 is provided with a boss 31, and the bimetallic strip 2 is provided on the boss 31 by the iron nail 9, and the moving contact 7 is provided below the stationary contact 8.

[0026] In this embodiment, the position of the nail 9 is calibrated by the boss 31 to adjust the contact pressure of the bimetallic strip 2 on the outer shell 1, thereby obtaining the required operating temperature, and the stationary contact 8 is a silver-copper composite metal.

[0027] Furthermore, one end of the outer shell 1 is provided with a first wire riveting groove 11, and one end of the base plate 3 is provided with a second wire riveting groove 32, and both the first wire riveting groove 11 and the second wire riveting groove 32 extend out of one end of the metal buckle 6.

[0028] In this embodiment, this design avoids interference from wire bending with the internal structure, while exposing the riveting points to the outside of the protector, facilitating rapid crimping by automated equipment.

[0029] Furthermore, the small thermal protector applied to the DC motor also includes insulating paper 4, which has a through hole in the middle. The insulating paper 4 is disposed on the contact surface between the housing 1 and the base plate 3, and the bimetallic strip 2 is located at the through hole.

[0030] In this embodiment, since the moving contact 7 and the stationary contact 8 are disconnected at the upper part of the housing 1, away from the end of the insulating paper 4, the heat generated by the arcing of the disconnecting contact when the protector is working is not easily transferred to the insulating paper 4, which is less likely to cause the insulating paper 4 to break down due to arcing and can also improve the life of the protector.

[0031] Furthermore, a plurality of positioning semicircular blocks 10 are symmetrically arranged below the base plate 3, and the two inner sides of the metal buckle 6 have guide grooves 11. Each guide groove 11 has a plurality of positioning semicircular grooves 12, and the plurality of positioning semicircular blocks 10 are respectively held in the corresponding positioning semicircular grooves 12 through the corresponding guide grooves 11.

[0032] In this embodiment, the positioning semicircular block 10 slides along the guide groove 11 to the positioning semicircular groove 12, thereby achieving precise alignment between the metal buckle 6 of the protector and the base plate 3.

[0033] In this invention, the first wire riveting groove 11 of the outer shell 1 and the second wire riveting groove 32 of the base plate 3 are respectively connected to the power input line and load output line of the DC motor, forming a conductive path through riveting fixation; when the bimetallic strip 2 bends due to motor overheating, its end moving contact 7 separates from the stationary contact 8 at the top of the inner shell 1, cutting off the circuit. At the same time, the thermistor 5 connected in parallel on the upper part of the outer shell 1 conducts and shunts the current due to the contact breaking, reducing the arc energy; at this time, the bimetallic strip 2 action area exposed by the through hole of the insulating paper 4 ensures no interference from insulating material, while the outer insulating paper 4 prevents the arc from being conducted to the bottom; during assembly, the positioning semicircular block 10 of the base plate 3 slides into the guide groove 11 of the metal buckle 6 to achieve quick positioning, ensuring that the thermistor 5 is tightly attached to the outer shell 1 for heating, and finally, the overall structure achieves low arc and fast current interruption protection when the DC motor is overloaded.

[0034] In this invention, when the protector contacts are normally closed, current flows through the contacts to form a closed circuit. When the thermal protector is heated, the thermistor 5 conducts and forms a circuit at the instant the contacts open. Due to the current shunting in the thermistor 5 circuit, the arcing between the contacts is reduced when the protector is disconnected, thus improving the lifespan of the protector. This achieves low-arc disconnection of the DC motor thermal protector. After the circuit is formed, the thermistor 5 continues to heat up, and its resistance value increases significantly, causing the thermistor 5 circuit to be in an open state. By connecting a temperature-dependent thermistor 5 in parallel outside the protector housing 1, the application of the thermal protector in DC motors is realized.

[0035] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Those skilled in the art can understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present utility model are still within the scope of the utility model.

Claims

1. A small thermal protector for DC motors, characterized in that, The device includes a metal clip, a thermistor, a housing, a bimetallic strip, and a base plate. The housing has a stationary contact at its inner top, and the bimetallic strip has a moving contact at one end. The metal clip is slidably connected to the base plate and abuts against the lower end face of the base plate. The thermistor is disposed between the metal clip and the housing. The bimetallic strip is disposed on the base plate, and the housing is disposed on the base plate and covers the bimetallic strip.

2. The miniature thermal protector for DC motors as described in claim 1, characterized in that, The other end of the bimetallic strip is provided with an iron nail, the base plate is provided with a boss, and the bimetallic strip is set on the boss by the iron nail, and the moving contact is located below the stationary contact.

3. The miniature thermal protector for DC motors as described in claim 2, characterized in that, One end of the outer casing is provided with a first wire riveting groove, and one end of the base plate is provided with a second wire riveting groove, and both the first wire riveting groove and the second wire riveting groove extend out of one end of the metal buckle.

4. The miniature thermal protector for DC motors as described in claim 3, characterized in that, The small thermal protector for DC motors also includes insulating paper with a through hole in the middle. The insulating paper is disposed on the contact surface between the housing and the base plate, and the bimetallic strip is located at the through hole.

5. The miniature thermal protector for DC motors as described in claim 4, characterized in that, Multiple positioning semicircular blocks are symmetrically arranged below the base plate. The two inner sides of the metal buckle have guide grooves, and each guide groove has multiple positioning semicircular slots. The multiple positioning semicircular blocks are respectively held in the corresponding positioning semicircular slots through the corresponding guide grooves.

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