Bimetal disc for external overload protector
By designing an elongated bimetal disc and installing arc-shaped reinforcement ribs on the front and rear sides of it, the problems of small flip force and large creep deformation displacement in the prior art are solved, which significantly improves the electrical life and reduces production costs.
Patent Information
- Application Number
- CN202422127525.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-06-27
- Estimated Expiration
- 2034-08-30
AI Technical Summary
The bimetal discs of existing external overload protectors have small flip force when jumping and flipping, and the creep deformation displacement is large, resulting in a short electrical service life.
A long bimetallic disc is designed with arc-shaped reinforcement ribs on the front and rear sides, and its arc-shaped direction is opposite to the arc-shaped or spherical direction of the bimetallic plate. By setting long hollow grooves and arc-shaped reinforcement ribs in the bimetal sheet, the creep deformation displacement of the bimetal sheet is reduced and the flip force is increased.
It effectively reduces the creep deformation displacement of the bimetal disc, improves the flip force and electrical life, and reduces production costs.
Smart Images
Figure CN223038852U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of an external overload protector, in particular to a bimetallic disc for an external overload protector. Background Technique
[0002] The existing external automatic reset overload protector mainly consists of a circular bimetallic disc 1, a first fixed contact 2, a nut 3, an adjusting screw 4, a second fixed contact 5, a housing 6 and a cover 7, as shown in Figure 1 Shown. The circular bimetallic disc 1 is fixedly connected to the bottom of the adjusting screw 4 through a first mounting hole 1-3, and is fixed in the inner cavity of the housing 6 through the adjusting screw 4 and the nut 3, so that the first moving contact 1-1 and the second moving contact 1-2 are respectively in close contact connection with the first fixed contact 2 and the second fixed contact 5. The bimetallic disc, as the driving component of the overload protector, is composed of metals with different thermal expansion coefficients and is formed into a spherical structure through a blanking forming process, so that it realizes a flipping deformation at a preset temperature. Since the bimetallic disc itself has resistance, heat energy will be generated when current passes through the bimetallic sheet, and its spherical height will start to slowly decrease; when the heat energy generated by the overload current increases and the bimetallic disc reaches the set operating temperature, it will suddenly jump in the reverse direction to realize the separation and disconnection of the moving contact and the fixed contact.
[0003] The above-mentioned circular bimetallic sheet 1-6 is formed into a spherical shape through a mold, as shown in Figure 2 、 Figure 3 Shown. The first wing portion 1-4 and the second wing portion 1-5 are respectively arranged on the left and right sides thereof, and the first moving contact 1-1 and the second moving contact 1-2 are respectively welded on the inner surfaces thereof.
[0004] When energized and heated, the process of the slow decrease of the spherical height of the bimetallic disc is also called the creep deformation process. In this process, the overload protector must remain in the conducting state; during the manufacturing process of the overload protector, the bimetallic disc 1 is riveted to the bottom of the adjusting screw 4, and by adjusting the relative height between the bottom of the adjusting screw 4 and the housing 6, a pulling force is applied to the bimetallic disc 1 to make its spherical height decrease, and this decrease distance must be greater than its creep deformation displacement amount to compensate for the ablation of the contact material caused by the continuous opening and closing of the moving and fixed contacts of the overload protector.
[0005] Taking the circular bimetallic disc used in a common external overload protector as an example, its model is P850R, the diameter of the spherical circular working area is φ16mm, the thickness of the disc is 0.15mm, and the volume is about 41.6mm³. The material of its high-expansion surface is 72% Mn, 18% Cu, 10% Ni, and the material of its low-expansion surface is 36% Ni, Bal Fe, which is composed of two materials. When electrified and heated, the bimetallic disc begins to creep and deform. When the current increases due to overload and the displacement of creep deformation reaches 0.31mm, it triggers a sudden jump and flip, which means that the displacement of creep deformation of the circular bimetallic disc in the free state is 0.31mm, and its flipping force F3 = 0.95N, which mainly depends on the elastic modulus of the bimetallic material itself.
[0006] The creep deformation of the bimetallic disc is one of the main reasons affecting the electrical life of the overload protector. Under the condition that the pulling force applied to the bimetallic disc by the adjusting screw is the same, the larger the displacement of creep deformation, the less the compensation amount for the ablation of the contact material, and the shorter the electrical life. In addition, if the flipping force of the bimetallic disc is smaller and the separation speed of the moving contact is slower, the arc time generated when the moving contact of the overload protector disconnects is longer, the ablation is more, and the electrical life of the overload protector is shorter.
[0007] The defects of the existing external overload protector are as follows: during operation, the displacement of creep deformation of the circular bimetallic disc is relatively large, and the sudden jump and flipping force is relatively small, which seriously shortens the electrical service life of the overload protector. Summary of the Invention
[0008] The technical problem to be solved by the present invention is to provide a bimetallic disc for an external overload protector and its preparation method, which can obtain a large flipping force during sudden jump and flip and has a relatively small displacement of creep deformation during the process from electrification and heating to sudden jump and flip, thereby greatly improving the electrical life of the bimetallic disc.
[0009] The technical solution proposed by the present utility model is as follows: A bimetallic disc for an external overload protector, comprising a first bimetallic disc, which includes a first bimetallic sheet, a third moving contact, and a fourth moving contact, and is fixed in the inner cavity of the housing by an adjusting screw. The third moving contact and the fourth moving contact are respectively in close contact connection with a first fixed contact and a second fixed contact. The first bimetallic sheet is in the shape of a long strip, with a third wing portion and a fourth wing portion provided on the left and right sides respectively, and the front and rear sides are respectively a first straight edge and a second straight edge that are parallel to each other. A long strip-shaped first empty groove parallel to the first straight edge is provided on the front side portion, and a long strip-shaped second empty groove parallel to the second straight edge is provided on the rear side portion. A second mounting hole is provided at the center of the first bimetallic sheet; a first arc-shaped reinforcing rib is formed between the first straight edge and the first empty groove, and a second arc-shaped reinforcing rib is formed between the second straight edge and the second empty groove. The first bimetallic sheet is in an arc surface or a spherical surface, and the arc surface directions of the first arc-shaped reinforcing rib and the second arc-shaped reinforcing rib are opposite to the arc surface or spherical surface direction of the first bimetallic sheet; the third moving contact and the fourth moving contact are respectively welded and fixedly connected to the inner surfaces of the third wing portion and the fourth wing portion.
[0010] The lengths of the first empty groove and the second empty groove are 0.5 to 0.6 times the length of the first bimetallic sheet; the distance between the first empty groove and the second empty groove is 4.5 to 5.3 times the widths of the first arc-shaped reinforcing rib and the second arc-shaped reinforcing rib.
[0011] Compared with the prior art, the present utility model has the following beneficial effects:
[0012] (1) The bimetallic disc for the external overload protector is formed by cutting off an arc-shaped surface on the front and rear sides of the existing circular bimetallic disc to form a long strip-shaped bimetallic sheet, and then a long strip-shaped empty groove is respectively opened on the front and rear sides of the middle part thereof to form strip-shaped arc-shaped reinforcing ribs located on its front and rear sides respectively, and the arc direction thereof is opposite to the arc surface or spherical surface direction of the long strip-shaped bimetallic sheet. Since arc-shaped reinforcing ribs are provided on the front and rear sides of the strip-shaped bimetallic disc, when overloaded and rapidly heated and deformed, the two arc-shaped reinforcing ribs will generate an inward pulling force, hindering the outward and downward extension of the left and right wing portions of the bimetallic sheet, thereby effectively reducing the downward creeping deformation displacement amount of the bimetallic sheet and greatly improving the electrical life of the external overload protector.
[0013] (2) Since arc-shaped reinforcing ribs with an arc direction opposite to the arc direction of the bimetallic sheet are provided on the front and rear sides of the strip-shaped bimetallic sheet, and the center of the bimetallic sheet is fixed and immovable, when electrified and heated, a downward turning force will be generated in both cases, and the superposition of the two will increase the turning force of the bimetallic sheet, thereby accelerating the turning and jumping speed of the bimetallic sheet, reducing the erosion of the arc on the contact surface of the contact, and greatly improving its electrical life.
[0014] (3) Since this bimetallic strip adopts a long-strip design, under the same usage conditions, it reduces the consumption of bimetallic material by more than 15% compared with the existing circular bimetallic strip, thus reducing the production cost. Description of the Drawings
[0015] Figure 1 It is a front view schematic diagram of an existing circular bimetallic disc for an external overload protector.
[0016] Figure 2 is Figure 1 The top view schematic diagram of the shown circular bimetallic disc.
[0017] Figure 3 is equipped with Figure 1 The structural schematic diagram of an external overload protector equipped with the shown circular bimetallic disc.
[0018] Figure 4 It is a front view schematic diagram of the bimetallic disc of an external overload protector of the present utility model.
[0019] Figure 5 is Figure 4 The top view schematic diagram of the shown bimetallic disc.
[0020] Figure 6 is Figure 5 The three-dimensional schematic diagram of the shown bimetallic disc.
[0021] Figure 7 is equipped with Figure 5 The structural schematic diagram of an external overload protector equipped with the shown bimetallic disc, where the moving contact of the bimetallic disc is in a free state.
[0022] Figure 8 is Figure 7 The structural schematic diagram of an external overload protector when the moving contact of the shown bimetallic disc is in a compressed state.
[0023] Figure 9 is Figure 4 The mechanical analysis schematic diagram when the shown bimetallic disc is deformed by heat.
[0024] Description of reference numerals in the figure: 1. Circular bimetallic disc; 1-1. First moving contact; 1-2. Second moving contact; 1-3. First mounting hole; 1-4. First wing; 1-5. Second wing; 2. First fixed contact; 3. Nut; 4. Adjusting screw; 5. Second fixed contact; 6. Housing; 7. Cover; 8. First bimetallic disc; 8-1. Third moving contact; 8-2. Fourth moving contact; 8-3. Third wing; 8-4. Fourth wing; 8-5. First arc-shaped reinforcing rib; 8-6. Second arc-shaped reinforcing rib; 8-7. First empty groove; 8-8. Second empty groove; 8-9. Second mounting hole; 8-10. First bimetallic sheet; 8-11. First straight edge; 8-12. Second straight edge. Detailed implementation manners
[0025] The present utility model will be further elaborated in detail through the following embodiments.
[0026] See Figures 4 to 9 As shown, a bimetallic disc for an external overload protector includes a first bimetallic disc 8, which includes a first bimetallic sheet 8-10, a third moving contact 8-1, and a fourth moving contact 8-2, and is fixed in the inner cavity of the housing 6 through an adjusting screw 4. The third moving contact 8-1 and the fourth moving contact 8-2 are respectively in close contact connection with the first fixed contact 2 and the second fixed contact 5. The first bimetallic sheet 8-10 is in the shape of a long strip, and a third wing 8-3 and a fourth wing 8-4 are respectively provided on the left and right sides, and the front and rear sides are respectively the first straight edge 8-11 and the second straight edge 8-12 that are parallel to each other. A long strip-shaped first empty groove 8-8 parallel to the first straight edge 8-11 is provided on the front side, and a long strip-shaped second empty groove 8-7 parallel to the second straight edge 8-12 is provided on the rear side. A second mounting hole 8-9 is provided at the center of the first bimetallic sheet 8-10; a first arc-shaped reinforcing rib 8-6 is formed between the first straight edge 8-12 and the first empty groove 8-8, and a second arc-shaped reinforcing rib 8-5 is formed between the second straight edge 8-12 and the second empty groove 8-7. The first bimetallic sheet 8-10 is in an arc surface or a spherical surface, and the arc surface directions of the first arc-shaped reinforcing rib 8-6 and the second arc-shaped reinforcing rib 8-5 are opposite to the arc surface or spherical surface direction of the first bimetallic sheet 8-10; the third moving contact 8-1 and the fourth moving contact 8-2 are respectively welded and fixedly connected to the inner surfaces of the third wing 8-3 and the fourth wing 8-4.
[0027] The lengths of the first empty groove 8-8 and the second empty groove 8-7 are 0.5 to 0.6 times the length of the first bimetallic sheet 8-10; the distance between the first empty groove 8-8 and the second empty groove 8-7 is 4.5 to 5.3 times the width of the first arc-shaped reinforcing rib 8-6 and the second arc-shaped reinforcing rib 8-5.
[0028] The working principle and working process of the first bimetallic sheet 8-10 are as follows:
[0029] When powered and heated, the first bimetallic strip 8-10 begins to generate a deformation force F1 that is radial and downward with respect to its arc surface. This deformation force F1 can be decomposed into an outward horizontal component force F 1-2 and a downward vertical component force F 1-1 . As the temperature gradually rises, the first bimetallic strip 8-10 begins to creep and deform, and its arc height a will slowly decrease accordingly. At the same time, the first and second arc-shaped reinforcing ribs 8-5 and 8-6 also generate a deformation force F2 that is radial and downward with respect to their arc surfaces. This deformation force F2 can be decomposed into an inward horizontal component force F 2-2 and a downward vertical component force F 2-1 ; the horizontal component force F 2-2 acts on the corresponding wing, hindering its outward extension, thereby slowing down the downward creep deformation of the third wing 8-3 and the fourth wing 8-4 of the first bimetallic strip 8-10. In addition, the downward vertical component force F 1-1 of the first bimetallic strip 8-10 is in the same direction as the downward vertical component forces F 2-1 of the first arc-shaped reinforcing rib 8-5 and the second arc-shaped reinforcing rib 8-6, and is in the same direction as the flipping direction of the first bimetallic strip 8-10. In this way, the two forces (F 1-1 +2×F 2-1 ) are superimposed on each other, increasing the flipping force of the first bimetallic strip 8-10 and making its flipping action more rapid.
[0030] Before leaving the factory, the first bimetallic disc 8 is fixed inside the inner cavity of the housing 6 through the second mounting hole 8-9, the adjusting screw 4, and the nut 3. By adjusting the adjusting screw 4, the third moving contact 8-1 and the fourth moving contact 8-2 apply a pressure to the first fixed contact 2 and the second fixed contact 5 respectively. At this time, the outer edges of the two wings of the first bimetallic strip 8-10 are displaced downward by a distance A. The arc height of the first bimetallic strip 8-10 when in a free state is A1, and the arc height of the first bimetallic strip 8-10 when in a compressed state is A2. Therefore, A = A1 - A2.
[0031] This preset displacement amount A must be greater than the downward creep deformation displacement value of the disc to ensure that the moving and fixed contacts remain in a conducting state during the heating process (when the design temperature is not reached) of the overload protector.
[0032] When the moving and fixed contacts are ablated by the arc during long-term operation, the moving contacts on both sides of the first bimetallic disc 8 will move upward due to the thinning of their thickness, the arc height of the first bimetallic strip 8-10 gradually increases, and the preset displacement amount A gradually decreases; when the preset displacement amount A of the bimetallic disc < the actual creep deformation displacement value of the disc, the overload protector will exhibit a vicious cycle of actions where the moving and fixed contacts are disconnected in advance and then quickly closed. The frequent opening and closing of the moving and fixed contacts cause the moving and fixed contacts to be more likely to adhere, and the ablation loss of the moving and fixed contacts is more serious.
[0033] Generally speaking, the first bimetallic disc 8 has the following advantages: the first bimetallic disc 8 has a large flipping force, a short flipping time, a short arc generated by the moving and fixed contacts, and less ablation of the moving contact, thus greatly improving its electrical life; the creep deformation displacement of the first bimetallic disc 8 is small. Under the condition of applying the same preset displacement amount to the disc, the ablation compensation amount of the moving contact is large, thus greatly improving its electrical life.
[0034] The following are the specific dimensional parameters of the first bimetallic sheet 8-10 of this embodiment: the sheet length is 20.6 mm, the sheet width is 12 mm, the sheet thickness is 0.15 mm, the center distance between the first empty groove 8-7 and the second empty groove 8-8 is 8.6 mm, the empty groove length is 11.2 mm, the empty groove width is 0.8 mm, the widths of the first and second arc-shaped reinforcing ribs 8-5 and 8-6 are 1.3 mm, the arc length is 9.1 mm, the height difference B between the centers of the arcs of the first and second arc-shaped reinforcing ribs 8-5 and 8-6 and the first bimetallic sheet 8-10 is 0.7 mm, and the volume of the first bimetallic sheet 8-10 is 34.9 mm³. The arc height A1 of the first bimetallic sheet 8-10 in the free state is 1 mm, the arc height A2 in the compressed state is 0.6 mm, and the deformation displacement value A of the first bimetallic sheet 8-10 after installation = A1 - A2 = 1 - 0.6 = 0.4 (mm). After actual measurement, the creep deformation displacement value of the first bimetallic sheet 8-10 in the free state is 0.22 mm, and its flipping force (F 1-1 +F 2-1 ) is 2 N. Therefore, due to arc ablation, when the ablation thickness of the moving contact reaches 0.4 - 0.22 = 0.18 mm, the moving and fixed contacts begin to perform frequent opening and closing actions until the moving and fixed contacts adhere, and the electrical life ends.
[0035] Under the same working conditions, the thicker the thickness of the moving contact after being ablated by the arc, the longer the time required and the more times the moving and fixed contacts open and close; therefore, when the creep deformation displacement of the bimetallic disc is smaller and the flipping force is larger, its electrical life is longer.
[0036] The first bimetallic sheet 8-10 can adopt an arc surface design or a spherical surface design because when energized and heated, the flipping forces generated by both are basically the same; since the arc surface height or spherical surface height of the first bimetallic sheet 8-10 in the free state is only 1 mm, which is relatively flat, and the sheet thickness is only 0.15 mm, the moving contact can be welded tightly and firmly inside the spherical third wing 8-3 and fourth wing 8-4.
Claims
1. A bimetallic disc for an external overload protector, comprising a first bimetallic disc (8), the first bimetallic disc (8) comprising a first bimetallic sheet (8-10) and a third moving contact (8-1), and a fourth moving contact (8-2), fixed in an inner cavity of a housing (6) by an adjusting screw (4), the third moving contact (8-1) and the fourth moving contact (8-2) being closely contacted and connected with the first fixed contact (2) and the second fixed contact (5), respectively, characterized in that: The first bimetallic sheet (8-10) is in the shape of a long strip, and is provided with a third wing (8-3) and a fourth wing (8-4) on the left and right sides respectively, and the front and rear sides are respectively a first straight side (8-11) and a second straight side (8-12) parallel to each other, the front side is provided with a long strip-shaped first empty slot (8-8) parallel to the first straight side (8-11), and the rear side is provided with a long strip-shaped second empty slot (8-7) parallel to the second straight side (8-12), and the center of the first bimetallic sheet (8-10) is provided with a second mounting hole (8-9); the first straight side (8-11) and the first empty slot (8-12) are connected to each other by a plurality of holes. A first arc-shaped reinforcing rib (8-6) is formed between the second straight edge (8-12) and the second empty slot (8-7), a second arc-shaped reinforcing rib (8-5) is formed between the first straight edge (8-12) and the second empty slot (8-7), the first bimetallic strip (8-10) is an arc surface or a spherical surface, and the arc surface direction of the first arc-shaped reinforcing rib (8-6) and the second arc-shaped reinforcing rib (8-5) is opposite to the arc surface or spherical surface direction of the first bimetallic strip (8-10); the third moving contact (8-1) and the fourth moving contact (8-2) are respectively welded and fixedly connected to the inner surfaces of the third wing (8-3) and the fourth wing (8-4).
2. The bimetallic disc for an external overload protector according to claim 1, characterized in that: The lengths of the first empty slot (8-8) and the second empty slot (8-7) are 0.5 to 0.6 times the length of the first bimetallic strip (8-10); the distance between the first empty slot (8-8) and the second empty slot (8-7) is 4.5 to 5.3 times the width of the first arc-shaped reinforcing rib (8-6) and the second arc-shaped reinforcing rib (8-5).