Welding process of thermal protector shell

Abstract

The invention belongs to the field of thermal protectors, and provides a welding process of a thermal protector shell, the thermal protector comprises an upper shell, a lower shell and a temperature controller assembly, the process comprises the following steps: step (1), assembling the upper shell, the lower shell and the temperature controller assembly; and (2) the ultrasonic welding head continues for 1-2 s at the power of 4-6 KW and the frequency of 20-40 KHz, and the upper shell and the lower shell are pressed. The upper shell and the lower shell of the thermal protector are welded by controlling the ultrasonic welding parameters, so that the upper shell and the lower shell are stably welded together, and the welding quality is improved.

Description

Technical Field

[0001] The invention belongs to the field of thermal protectors, in particular to a welding process for a thermal protector shell. Background Art

[0002] PBT (Polybutylene Terephthalate) is a thermoplastic engineering plastic belonging to polyester materials. It is synthesized by polycondensation of terephthalic acid (PTA) and butanediol (BDO).

[0003] A thermal protector is an electrical device widely used in home appliances, industrial equipment and various electrical systems. It is designed to avoid failures or safety hazards caused by overheating. Its working principle is mainly to sense temperature changes inside or around the device. When the temperature reaches the set threshold, the thermal protector will quickly disconnect the power supply or take other protective measures to prevent the equipment from being damaged due to overheating or causing serious consequences such as fire.

[0004] CN202122111656.9 discloses a thermal protector housing, comprising an upper housing and a lower housing arranged relatively to each other, wherein a sealing thread is respectively provided on the same side wall of the upper housing and the lower housing, and the two sealing threads together form a sealing portion that is interference-fitted with the outer surface of the lead-out wire of the thermal protector; the upper housing and the lower housing are sealed and connected by ultrasonic welding. The housing is divided into an upper housing and a lower housing, and the wire lead-out portions of the two housings are both provided with sealing threads, which are convenient to cooperate with the lead-out wires and have good airtightness. In combination with the upper housing and the lower housing, ultrasonic welding is used to close the housing, which saves the costs of materials, manpower, curing time, etc. for epoxy sealing, thereby improving production efficiency.

[0005] In the above technical solution, the outer shell of the thermal protector includes an upper outer shell and a lower outer shell, and the upper outer shell and the lower outer shell are closed by ultrasonic welding. However, when closing the upper outer shell and the lower outer shell, the power, pressure and time of ultrasonic welding will affect the sealing effect. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems and provide a welding process for a thermal protector shell. The process uses ultrasonic welding to weld the upper shell and the lower shell of the thermal protector, thereby firmly welding the upper shell and the lower shell together and improving the welding quality.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A welding process for a thermal protector housing, the thermal protector comprising an upper housing, a lower housing and a temperature controller assembly, the process comprising the following steps:

[0009] Step (1): Assemble the upper shell, the lower shell and the thermostat assembly;

[0010] Step (2): The upper shell and the lower shell are pressed together by an ultrasonic welding head at a power of 4 to 6 kW and a frequency of 20 to 40 kHz for 1 to 2 seconds.

[0011] The power in step (2) can be 4KW, 5KW, or 6KW, but is not limited to the listed values. Other values ​​not listed within this numerical range are applicable.

[0012] The frequency in step (2) can be 20 KHz, 30 KHz, or 40 KHz, but is not limited to the listed values. Other values ​​not listed within this numerical range are applicable.

[0013] The time in step (2) can be 1 s, 1.5 s, or 2 s, but is not limited to the listed values. Other values ​​not listed within this numerical range are applicable.

[0014] In the above-mentioned welding process of the thermal protector shell, the step (1.1) is also included: the ultrasonic welding head presses the upper shell down onto the lower shell for at least 1 second, including but not limited to 1 second, 2 seconds, and 3 seconds.

[0015] In the above-mentioned welding process for the thermal protector housing, in step (2), the pressing pressure is 6 to 8 N, and the amplitude is 30 to 50 μm.

[0016] The pressure in step (2) can be 6N, 7N, or 8N, but is not limited to the listed values. Other values ​​not listed within this numerical range are applicable.

[0017] The amplitude in step (2) can be 30 μm, 40 μm, or 50 μm, but is not limited to the listed values. Other values ​​not listed within this numerical range are applicable.

[0018] In the above-mentioned welding process of the thermal protector shell, it also includes: step (2.1): after the pressing is completed, maintaining the pressure in step (2) and continuing to press down for at least 1 second, including but not limited to 1 second, 2 seconds, and 3 seconds.

[0019] In the above-mentioned welding process of the thermal protector housing, step (1) specifically includes assembling the upper shell, the lower shell and the thermostat assembly and placing them into a mold in an ultrasonic welding device for fixing. The ultrasonic welding device adopts a model of BRANSON920.

[0020] In the above-mentioned welding process for the thermal protector shell, the materials of the upper shell and the lower shell are both PBT materials.

[0021] In the above-mentioned welding process of the thermal protector shell, a first notch and a second notch are respectively provided on the same side wall of the upper shell and the lower shell. When the upper shell and the lower shell are fitted together, the first notch and the second notch cooperate to form a fixing part for fixing the lead wire of the thermostat assembly.

[0022] In the above-mentioned welding process for the thermal protector housing, the number of the fixing parts is two, and the two fixing parts are arranged at intervals.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In the present invention, an ultrasonic welding joint is used to weld the upper shell and the lower shell of the thermal protector, and a power of 4 to 6 kW and a frequency of 20 to 40 kHz are used to press the upper shell and the lower shell for 1 to 2 seconds, thereby firmly welding the upper shell and the lower shell together and improving the welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a structural schematic diagram of a welding process for a thermal protector housing in Example 1;

[0026] Among them, the reference numerals of the figures are:

[0027] 1. Upper shell; 11. First notch; 2. Lower shell; 21. Second notch. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] refer to Figure 1 The thermal protector of the present invention comprises an upper shell, a lower shell and a thermostat assembly (not shown in the figure), and a first notch and a second notch are respectively provided on the same side wall of the upper shell and the lower shell. When the upper shell is covered on the lower shell, the first notch and the second notch cooperate to form a fixing portion for fixing the lead wire of the thermal protector;

[0031] The number of the fixing parts is 2, and the two fixing parts are arranged at an interval.

[0032] The thermostat assembly has been disclosed in Chinese patent CN211320008U, so the structure of the thermostat assembly will not be described in detail in this embodiment.

[0033] Under this design, when assembling the thermal protector, first put the thermostat assembly into the lower shell, and then cover the upper shell on the lower shell to complete the assembly of the thermal protector. Since the first notch and the second notch are respectively provided on the same side wall of the upper shell and the lower shell, when the upper shell and the lower shell are assembled, the cooperation of the first notch and the second notch will constitute a fixing part for fixing the lead wire of the thermal protector, and there are usually two lead wires, so there are two fixing parts.

[0034] Example 2

[0035] A welding process for a thermal protector housing, in which the upper housing and the lower housing in Example 1 are welded, comprises the following steps:

[0036] Step (1): Assemble the upper shell, the lower shell and the temperature controller assembly and place them in a mold of an ultrasonic welding device to fix them.

[0037] Step (2): The upper shell and the lower shell are pressed together by an ultrasonic welding head at a power of 4 kW, a frequency of 20 kHz, an amplitude of 30 μm, a pressure of 6 N, and a duration of 1 s.

[0038] Example 3

[0039] It is basically the same as Example 2, except that it also includes step (1.1): the ultrasonic welding head presses the upper shell down onto the lower shell, and the pressing time is 1 second.

[0040] Example 4

[0041] The method is basically the same as Example 2, except that it further includes step (2.1): after the pressing is completed, the pressure in step (2) is maintained and pressed down for 1 second.

[0042] Example 5

[0043] The method is basically the same as Example 2, except that it further includes step (1.1), specifically: the ultrasonic welding head presses the upper shell down onto the lower shell for 1 second;

[0044] The method further includes step (2.2), specifically, after the pressing is completed, maintaining the pressure in step (2) for 1 second.

[0045] Example 6

[0046] It is basically the same as Example 5, except that in step (2), the upper shell and the lower shell are pressed together at a power of 5 KW, a frequency of 30 KHz, an amplitude of 40 μm, a pressure of 7 N, and a duration of 1.5 s.

[0047] Example 7

[0048] It is basically the same as Example 5, except that in step (2), the upper shell and the lower shell are pressed together at a power of 6 kW, a frequency of 40 kHz, an amplitude of 50 μm, a pressure of 8 N, and a duration of 2 s.

[0049] Example 8

[0050] It is basically the same as Example 5, except that in step (1.1), the pressing time is 3s.

[0051] Example 9

[0052] It is basically the same as Example 5, except that in step (2.1), the pressing time after welding is completed is 3 seconds.

[0053] Example 10

[0054] It is basically the same as Example 5, except that in step (2), the pressing pressure of the ultrasonic welding head is 2N.

[0055] Embodiment 11

[0056] It is basically the same as Example 5, except that in step (2), the pressing pressure of the ultrasonic welding head is 12N.

[0057] Example 12

[0058] It is basically the same as Example 5, except that in step (2), the amplitude of the ultrasonic welding head is 20 μm.

[0059] Embodiment 13

[0060] It is basically the same as Example 5, except that in step (2), the amplitude of the ultrasonic welding head is 60 μm.

[0061] Comparative Example 1

[0062] Basically the same as Example 5, except that in step (2), the power is 1KW.

[0063] Comparative Example 2

[0064] Basically the same as Example 5, except that in step (2), the power is 9KW.

[0065] Comparative Example 3

[0066] It is basically the same as Example 5, except that in step (2), the frequency is 10KHz.

[0067] Comparative Example 4

[0068] It is basically the same as Example 5, except that in step (2), the frequency is 50KHz.

[0069] Comparative Example 5

[0070] It is basically the same as Example 5, except that in step (2), the pressing time is 3s.

[0071] Comparative Example 6

[0072] It is basically the same as Example 5, except that the materials of the upper shell and the lower shell are both ABS material.

[0073] Table 1 Welding results of upper shell and lower shell

[0074]

[0075]

[0076] Table 2 Tensile test results

[0077] Tension / N Example 2 25 Example 3 30 Example 4 32 Example 5 50 Example 6 46 Example 7 43 Example 8 49 Example 9 48 Example 10 23 Embodiment 11 40 Example 12 28 Example 13 24 Comparative Example 1 17 Comparative Example 2 44 Comparative Example 3 19 Comparative Example 4 42 Comparative Example 5 45 Comparative Example 6 22

[0078] Result analysis:

[0079] 1. From the results of Examples 2 and 3, it can be seen that Example 3 requires a greater pulling force to separate the upper shell and the lower shell, and its welding effect is better. The upper shell and the lower shell are pre-pressed to allow the upper shell and the lower shell to gradually fit together, avoiding direct pressure that causes uneven contact between the upper shell and the lower shell.

[0080] 2. From the results of Examples 2 and 4, it can be seen that Example 4 requires a greater pulling force to separate the upper shell and the lower shell. When the ultrasonic welding head is working, the upper shell and the lower shell will generate high temperature through friction and then melt and combine. However, the weld between the upper shell and the lower shell is in a molten state before it is cooled and formed. By continuously applying pressure to the upper shell and the lower shell, the weld is shaped, and the degree of deformation of the weld during the cooling process is suppressed, thereby improving the welding effect.

[0081] 3. From the analysis of the results of Example 2, Example 3, Example 4 and Example 5, a positive effect can be achieved in the tensile test results of the upper shell and the lower shell by adding step (1.1) or step (2.1), and after combining step (1.1) and step (2.1) and welding them, it is found that in the tensile test, a very large tensile force is required to separate the upper shell and the lower shell, and an excellent test result is obtained. It can be seen that the combination of step (1.1) and step (2.1) can play a synergistic role.

[0082] 4. It can be seen from the results of Examples 5, 6 and 7 that when the power, frequency, amplitude, pressing pressure and continuous pressing pressure of the ultrasonic welding head are all increasing, the required pulling force gradually decreases and the welding effect gradually decreases.

[0083] 5. According to the results of Example 10 and Example 11, when the pressing pressure exceeds or is lower than the range of 6 to 8N, the test results of the tensile force are all low. When the pressing pressure is too low, the friction at the weld between the two shells is insufficient, and a large part of the energy is used for surface sliding. When the pressure is too high, the upper shell or the lower shell will be displaced, making the welding effect unsightly.

[0084] 6. According to the tensile test results of Example 12 and Example 13, firstly, under the condition of low amplitude, the moving speed of the upper shell and the lower shell is too small, and the friction generated is not enough to generate enough energy, resulting in low welding strength at the welding point and reduced tensile test results; while in the case of high amplitude, the upper shell and the lower shell will cause local excessive deformation, affecting the welding effect.

[0085] 6. From the results of Comparative Examples 1 and 2, it can be seen that when the power is low, the welding point between the upper shell and the lower shell cannot reach the melting point, resulting in incomplete welding. When the power is high, although the upper shell and the lower shell can be connected, it will cause excessive melting of the upper shell and the lower shell, reducing the welding effect.

[0086] 7. From the results of Comparative Examples 3 and 4, it can be seen that the tensile test effect will deteriorate when the frequency is lower or higher than the range of 20 to 40 kHz. When the frequency is low, the heat generated is insufficient and good welding cannot be achieved, resulting in low strength of the weld formed between the upper shell and the lower shell. When the frequency is too high, the weld will be over-melted and the weld will be unsightly.

[0087] 8. According to the results of Example 5 and Comparative Example 5, when a longer pressing time is used, the welding point between the upper shell and the lower shell will be excessively melted under the long pressing time, so the welding point formed after cooling is not beautiful and of poor quality.

[0088] 9. It can be seen from the results of Example 5 and Comparative Example 6 that when the process parameters are used to weld the upper shell and the lower shell made of ABS material, the welding effect is significantly reduced, which further proves that an excellent welding effect can be achieved by using this process in combination with the upper shell and the lower shell made of PBT material.

[0089] In summary, the present invention controls the power, frequency, amplitude, pressing pressure and pressing time of the ultrasonic welding head. Through analysis of experimental results, it is concluded that the ultrasonic welding head presses the upper shell and the lower shell for 1s under the parameters of 4KW power, 20KHz frequency, 30μm amplitude and 6N pressing pressure, and by increasing the pre-pressing and the steps of continuous pressure after the welding is completed, it is surprisingly found that when welding the upper shell and the lower shell made of PBT, the connection effect between the upper shell and the lower shell is very good.

[0090] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements or modifications can be made without departing from the principles of the present invention. These improvements or modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A welding process for a thermal protector housing, wherein the thermal protector comprises an upper housing, a lower housing and a thermostat assembly, characterized in that: The process comprises the following steps: Step (1): Assemble the upper shell, the lower shell and the thermostat assembly; Step (2): The upper shell and the lower shell are pressed together by an ultrasonic welding head at a power of 4 to 6 kW and a frequency of 20 to 40 kHz for 1 to 2 seconds.

2. A welding process for a thermal protector housing according to claim 1, characterized in that: The method also includes step (1.1): the ultrasonic welding head presses the upper shell down onto the lower shell for at least 1 second.

3. A welding process for a thermal protector housing according to claim 2, characterized in that: In the step (2), the pressing pressure is 6 to 8 N, and the amplitude is 30 to 50 μm.

4. A welding process for a thermal protector housing according to claim 3, characterized in that: It also includes: step (2.1): after the pressing is completed, maintaining the pressure in step (2) and continuing to press down for at least 1 second.

5. A welding process for a thermal protector housing according to claim 1, characterized in that: Specifically, the step (1) includes assembling the upper shell, the lower shell and the temperature controller assembly and placing them into a mold in an ultrasonic welding device for fixing.

6. A welding process for a thermal protector housing according to claim 1, characterized in that: The upper shell and the lower shell are both made of PBT material.

7. A welding process for a thermal protector housing according to claim 1, characterized in that: A first notch and a second notch are respectively provided on the same side wall of the upper shell and the lower shell. When the upper shell and the lower shell are fitted together, the first notch cooperates with the second notch to form a fixing portion for fixing the lead wire of the thermostat assembly.

8. A welding process for a thermal protector housing according to claim 7, characterized in that: The number of the fixing parts is 2, and the two fixing parts are arranged at an interval.

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