An electric heater

Abstract

The present invention belongs to the technical field of electric heating, and particularly relates to an electric heater. It includes a metal outer tube, an electric heating wire is arranged inside the metal outer tube, the two ends of the electric heating wire are connected to lead-out rods, and an insulating and heat-conducting material is filled inside the metal outer tube; the bending position of the metal outer tube is partially pressed, and the change value of the cross-sectional area of the electric heating tube before pressing and after pressing in the pressed part is 8% - 25%, and a pressing transition section is used between the pressed position and the non-pressed position. The present invention reduces the cross-sectional area of the electric heating tube after pressing, improves the heat exchange rate of the internal insulating and heat-conducting material, improves the electrical properties such as the high-voltage resistance of the product, improves the safety performance of the product, and prolongs the service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric heating, and particularly relates to an electric heater. Background Art

[0002] At present, conventional electric heating tubes on the market have a circular cross-section and are processed through subsequent processes such as rolling to form the final straight tube heating tube; or are directly bent into the final electric heating tube product; or are bent and then wound into a spiral shape to form the final structure of the electric heating tube product. In order to improve the heat conduction ability of the internal insulating material and extend the service life, the prior art only performs pressing treatment on local bending positions. However, in the existing pressing treatment, the density of the insulating and heat-conducting material at the pressed position of the product after pressing is still not significantly improved, resulting in the heat generated by the internal electric heating wire not being able to be quickly transferred out, causing the internal electric heating wire to overheat and melt; at the same time, the pressing treatment is not in place, resulting in low high-voltage electrical performance at the pressed position of the product, and there are safety hazards such as large leakage current during operation of the product; at the same time, the pressing treatment is not appropriate, and the heat generated by the internal electric heating wire cannot be quickly transferred out. Once the product has an abnormal working condition, the resistance wire in the electric heating tube may melt earlier than the temperature control device (such as a thermostat, temperature fuse) outside or around the electric heating tube, or the temperature fuse takes a longer time to melt, resulting in the inability to quickly protect the product, the surface temperature of the product continues to rise, posing a safety hazard to the accessories around the product, and not meeting the product safety standard performance requirements.

[0003] In addition, due to the unreasonable pressing treatment in the prior art, there will also be an over-pressing phenomenon, resulting in serious damage and micro-cracks on the outer tube of the electric heating tube, affecting the safety performance of the product and generating a large number of scraps. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an electric heater in view of the problems existing in the prior art.

[0005] To solve the problems existing in the prior art, the present invention is realized through the following technical solutions:

[0006] Provide an electric heater, including a metal outer tube, an electric heating wire is arranged inside the metal outer tube, both ends of the electric heating wire are connected to lead-out rods, and the metal outer tube is filled with an insulating and heat-conducting material; the bending position of the metal outer tube is locally pressed, and the change value of the cross-sectional area of the electric heating tube before pressing and after pressing at the pressed part is 8% - 25%, and a pressing transition section is used between the pressed position and the non-pressed position.

[0007] As an improvement, each corner of the pressed cross-section is rounded to avoid cracking the metal outer tube and also avoid damaging the internal electric heating wire and affecting the service life of the electric heating wire.

[0008] As an improvement, the cross-sectional shape of the pressed part is an olive shape, a triangle, an arch shape or a trapezoid, etc.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] The present invention reduces the cross-sectional area of the electric heating tube after pressing, improves the heat exchange rate of the internal insulating and heat-conducting material, enhances the electrical properties such as the high-voltage resistance of the product, improves the safety performance of the product, and extends the service life. The density of the internal insulating and heat-conducting material of the electric heating tube is increased by 5% - 20%, the high-voltage resistance performance of the product is increased by 5% - 15%, and at the same time, excessive pressing is avoided, which may cause damage to the metal outer tube, and even result in defects such as cracks and fractures, improving the safety performance of the product or reducing scrap, and reducing the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of Embodiment 1 of the present invention;

[0012] Figure 2 is Figure 1 a schematic diagram in the J-J direction of

[0013] Figure 3 is a schematic diagram of Embodiment 2 of the present invention;

[0014] Figure 4 is Figure 3 a schematic diagram in the K-K direction of

[0015] Figure 5 is a schematic diagram of Embodiment 3 of the present invention;

[0016] Figure 6 is Figure 5 a schematic diagram in the L-L direction of

[0017] Figure 7 is a schematic diagram of Embodiment 4 of the present invention;

[0018] Figure 8 is Figure 7 a schematic diagram in the M-M direction of

[0019] Figure 9 is a schematic diagram of Embodiment 5 of the present invention;

[0020] Figure 10 is a schematic diagram of Embodiment 6 of the present invention;

[0021] Figure 11 is a schematic diagram of sampling in the test of the present invention.

[0022] In the figure: 1 - lead rod, 2 - metal outer tube, 3 - heating wire, 4 - insulating and heat-conducting material, 5 - pressing cross-section, 6 - pressing area, 7 - pressing transition area. DETAILED DESCRIPTION OF THE INVENTION

[0023] In conjunction with the accompanying drawings, the present invention will be described in detail below through specific implementation examples.

[0024] An electric heater includes a metal outer tube 2, an electric heating wire 3 is arranged inside the metal outer tube 2, both ends of the electric heating wire 3 are connected to lead-out rods 1, and an insulating heat-conducting material 4 is filled inside the metal outer tube 2; the bending position of the metal outer tube is locally pressed, and the change value of the cross-sectional area of the electric heating tube before pressing and after pressing in the pressed part is 8% - 25%, and a pressed transition section is used to process between the pressed position and the non-pressed position.

[0025] Each corner of the pressed cross-section 5 is rounded to avoid cracking the metal outer tube and also avoid damaging the internal electric heating wire 3, which affects the service life of the electric heating wire 3. For the metal outer tube 2 made of stainless steel material, due to the mechanical properties of the stainless steel material itself and its high compressive strength, when the electric heating tube made of it is pressed, the change value of the cross-sectional area of the electric heating tube before pressing and after pressing is controlled between 8% - 15%. For the metal outer tube made of aluminum or aluminum alloy, due to its mechanical properties, its compressive strength is relatively lower than that of stainless steel, its elongation rate is high, and its ductility is good. When the electric heating tube made of it is pressed, the change value of the cross-sectional area of the electric heating tube before pressing and after pressing is controlled between 13% - 25%. For the metal outer tube made of copper and copper alloy, its compressive strength is relatively lower than that of stainless steel, its elongation rate is high, and its ductility is good. When it is pressed, the change value of the cross-sectional area of the electric heating tube before pressing and after pressing is controlled between 8% - 20%.

[0026] Based on the change values of the cross-sectional areas before and after pressing described above, different cross-sectional shapes can be used to achieve the pressing of the electric heating tube. For example Figure 2 、 4 、6 and 8, the cross-sectional shape of the pressed part is an olive shape, a triangle, an arch or a trapezoid, etc.

[0027] Example 1

[0028] For example Figure 1 For the straight tube shown, pressing can be carried out at different positions of the heating tube. The whole straight tube is pressed, and the lead-out rod 1 is a non-heating section and can not be pressed.

[0029] Example 2

[0030] As shown in Fig. 3, the heating tube is formed by bending both ends of a straight tube. After bending, the whole is pressed. In order to ensure a smooth transition between the pressed part and the non-pressed part, a pressed transition area 7 needs to be used for processing.

[0031] Example 3

[0032] For example Figure 5 For the spiral heating tube applied in a cup-type or tank-type heater shown, it is a straight tube that is bent after being roll-pressed. After the whole is pressed, it is then wound.

[0033] Example 4

[0034] As Figure 7 shown, based on Embodiment 3, in order to further improve the performance of the heating tube at the bending part, it is necessary to perform secondary pressing on it.

[0035] Embodiment 5

[0036] As Figure 9 shown, the heating tube is formed by bending the middle part of the straight tube after roll pressing. After bending, the bent part is pressed.

[0037] Embodiment 6

[0038] As Figure 10 shown, the heating tube, as Figure 2 shown, is formed by bending both ends of the straight tube. Pressing is performed on specific positions. In order to ensure a smooth transition between the pressed part and the unpressed part, it is necessary to adopt a pressed transition section treatment.

[0039] The technical effects of the present invention will be described below by taking the following three tests as examples.

[0040] Test 1: For the stainless - steel heating tube, fill it with the insulating and heat - conducting material 4, and put the straight - tube heating tube after roll pressing into the pressing die with a specific cavity for pressing treatment to obtain a heating tube that meets the cross - sectional area change range. As Figure 11 shown, take 5 samples, first test and record the ultimate withstand voltage values of the products respectively, and then in the pressing area range, take another 5 small sections each from the upper, middle, and lower segments to measure the density of the insulating and heat - conducting material 4 after pressing.

[0041]

[0042] Test 2: For the heating tube before pressing, as Figure 11 shown, take 5 samples, first test and record the ultimate withstand voltage values of the products respectively, and then in the pressing area range, take another 5 small sections each from the upper, middle, and lower segments to measure the density of the insulating and heat - conducting material after pressing.

[0043]

[0044]

[0045] Test 3: For the heating tube with a cross - sectional area change less than 8% after pressing, as Figure 11 shown, take 5 samples, first test and record the ultimate withstand voltage values of the products respectively, and then in the pressing area range, take another 5 small sections each from the upper, middle, and lower segments to measure the density of the insulating and heat - conducting material 4 after pressing.

[0046]

[0047] One set of data from each of the tests 1 and 2 was selected to compare the withstand voltage value and the density of the insulating thermal conductive material 4. The results are shown in the following table:

[0048]

[0049] One set of data from each of the tests 3 and 2 was selected to compare the withstand voltage value and the density of the insulating thermal conductive material 4. The results are shown in the following table:

[0050]

[0051] Finally, it should be noted that the above examples are only specific examples of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art from the present invention should be considered as the protection scope of the present invention.

Claims

1. An electric heater, comprising a metal outer tube, an electric heating wire is arranged inside the metal outer tube, the two ends of the electric heating wire are connected to lead-out rods, and an insulating heat-conducting material is filled inside the metal outer tube; It is characterized in that the metal outer tube is partially pressed, and the change value of the cross-sectional area of the electric heating tube before pressing and after pressing in the pressed part is 8% - 25%, and a pressed transition section is used between the pressed position and the non-pressed position.

2. An electric heater according to claim 1, It is characterized in that each corner of the pressed cross-section is rounded to avoid cracking the metal outer tube and also avoid damaging the internal electric heating wire, which affects the service life of the electric heating wire.

3. An electric heater according to claim 1, It is characterized in that the cross-sectional shape of the pressed part is olive-shaped, triangular, arched or trapezoidal.

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