A circuit breaker moving contact assembly, welding device and welding method thereof

Abstract

A kind of circuit breaker movable contact assembly, welding device and welding method thereof, including movable support and movable contact of movable support end surface, the movable support is copper alloy material, the movable contact is high-strength silver alloy material, the bottom of the welding surface of the movable contact is provided with several convex ribs along width arrangement, the welding surface of the movable contact is sufficient for product welding Silver filling amount, without additional any solder when the movable contact assembly product welding, using the silver layer of contact welding surface and copper alloy support can complete the welding of product by resistance spot welding process, the weld area of movable contact and movable support is not obvious gap, movable contact has been embedded in the inside of support, so that both have silver copper alloy chemical action, and physical combination of larger plastic deformation, finally obtain higher quality joint strength.

Description

Technical Field

[0001] This invention relates to a circuit breaker moving contact assembly, a welding device, and a welding method thereof, belonging to the field of welded electrical contact assembly processing parts. Background Technology

[0002] Molded case circuit breakers (MCCBs) automatically disconnect current when the current exceeds the trip setting. The term "molded case" refers to the use of a plastic insulator as the outer shell of the device, used to isolate conductors from grounded metal parts. MCCBs typically contain a thermomagnetic trip unit, while larger MCCBs are equipped with solid-state trip sensors. Their trip units are divided into thermomagnetic trip and electronic trip units. Commonly used rated currents include 63, 80, 100, 125, 160, 200, 225, 250, 315, 350, 400, 500, and 630A. MCCBs provide leakage current, short-circuit, and overload time-delay protection. MCCBs can not only close, carry, and interrupt current in normal circuits, but also close circuits in cases of abnormal operation or overload of electrical appliances; if a short-circuit fault occurs, the MCCB will automatically disconnect the switch upon receiving a command, thus protecting the circuit. Molded case circuit breakers are equipped with highly accurate and sensitive leakage current protection devices, thus possessing superior leakage current protection capabilities.

[0003] As the core electrical contact component inside a molded case circuit breaker, the quality of the moving contact assembly largely determines the service life of the circuit breaker switch. Therefore, the welding quality of the moving contact assembly is particularly important. At present, domestic and foreign companies mainly use high-frequency induction brazing or resistance brazing processes when welding circuit breaker moving contact assemblies.

[0004] If high-frequency induction brazing is used, the welding time is long and the heat-affected zone is large. This will cause severe annealing of the bracket and a significant decrease in the material hardness. During the subsequent use of the molded case circuit breaker, the large contact impact force between the moving bracket and the stationary contact when they operate will cause large deformation at the end of the moving component bracket, resulting in poor contact or no contact between the moving and stationary contacts, ultimately affecting the performance of the product.

[0005] If traditional metal electrode resistance brazing is used, silver-based solder is usually required to complete the welding of the bracket and contacts. To ensure the weld strength of the product, there will be obvious solder overflow around the moving contacts after welding. In this case, the welding shear force of the moving components can generally reach 100 N / mm. 2However, especially for double-break molded case circuit breaker products, even with good weld strength in the moving contact assembly, it may not meet the stringent electrical life requirements or the breaking test requirements for ultra-high currents (such as 36kA and 72kA). The problem of contact detachment during the use or electrical performance testing of double-break moving contact assemblies in molded case circuit breakers has become a major pain point for many low-voltage electrical equipment manufacturers. How to resolve the mismatch between the weld strength of the moving contact assembly and the final performance of the molded case circuit breaker product is a critical technical issue that industry technicians urgently need to address.

[0006] Brazing (resistance brazing or induction brazing) involves melting filler metal to wet the contact and support welding surfaces, ultimately forming a ternary alloy structure in the weld area. Judging solely from the product's weld shear strength and metallographic strength indicators, brazing can meet the product's static performance requirements. However, during the electrical performance testing of molded case circuit breakers or high-current breaking tests, the problem of moving contact detachment frequently occurs. Morphological analysis of the contact and support weld area after contact detachment reveals that the filler metal reaches its melting point under the high temperature of the electric arc and then flows out of the weld area. The contact gradually floats above the support welding surface, and under the continuous high temperature of the electric arc, the serious failure problem of moving contact detachment eventually occurs. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a circuit breaker moving contact assembly and its welding method.

[0008] A circuit breaker moving contact assembly includes a moving bracket and a moving contact on the end face of the moving bracket. The moving bracket is made of copper alloy, and the moving contact is made of high-strength silver alloy. The bottom of the welding surface of the moving contact is provided with a plurality of raised ribs arranged along the width. The welding surface of the moving contact is infiltrated with sufficient silver filler for product welding.

[0009] Preferably, the raised ribs on the welding surface of the moving contact are semi-circular or grid-shaped, and the number of raised ribs is at least two.

[0010] A welding device for a circuit breaker moving contact assembly is provided. The welding device is used to weld the moving contact assembly. The welding device includes an upper electrode, a moving support base and two lower electrodes. The moving support base is used to support the moving support. The moving support base is provided with a support member for supporting the moving support. The end face of the support member is designed to fit against the moving support. The upper electrode presses the moving contact against the moving support.

[0011] Furthermore, it also includes an assembly alignment device, which includes a positioning clamp, a positioning clamp opening and closing cylinder, a positioning clamp moving cylinder, and a pressure rod cylinder for driving the upper electrode to rise and fall. When the positioning clamp closes, it forms a clamping cavity that matches the shape of the moving contact. The positioning clamp opening and closing cylinder drives the positioning clamp to open or close, and the positioning clamp moving cylinder drives the positioning clamp to move above and outside the moving support.

[0012] Furthermore, each of the lower electrodes is provided with an electrode holder for fixing the electrode, and one of the electrode holders is provided with an electrode cylinder that drives it to move closer to or away from the other electrode holder.

[0013] Furthermore, a support base is provided below the moving contact support for fixing the moving bracket support.

[0014] A welding method for a circuit breaker moving contact assembly, wherein the moving contact assembly is welded using any of the aforementioned welding devices, and no solder is required during the entire welding process. The welding method includes:

[0015] (1) Placement of the moving bracket: Place the moving bracket to be welded on the moving bracket support base, and the moving bracket, the moving bracket support base and the fixed electrode in the lower electrode group are in close contact with each other; the moving bracket is made of copper alloy.

[0016] (2) Place the moving contact, start the positioning clamp opening and closing cylinder and the positioning clamp moving cylinder. The width between the positioning clamps should be slightly larger than the width of the moving contact itself. Generally, the gap between the two is 0.3-0.5mm. At this time, the contact will fall on the bracket welding surface. The moving contact is made of high-strength silver alloy material, such as AgW, AgWC, etc. The contact specifications are designed according to the current level of the specific product. When designing the contact, its welding surface has several raised teeth. The raised teeth and number of the contact welding surface can be adjusted according to the specifications of the contact.

[0017] (3) Positioning of the moving bracket and contact point, restart the positioning clamp opening and closing cylinder, close the positioning clamp, clamp the moving contact and bracket so that the moving contact and moving bracket are completely positioned in the front, back and left and right directions; then start the pressure rod cylinder to move the upper electrode vertically downward until it is close to the moving contact point, restart the positioning clamp opening and closing cylinder to separate the positioning clamp.

[0018] (4) Single-head welding: After completing all the above steps, it means that all the preparatory work before welding has been completed. Turn on the power of the resistance welding equipment, and under the set welding current, welding time and welding pressure and other process parameters, heat the workpiece and complete the welding of a single moving contact of the moving contact assembly.

[0019] (5) When the product is discharged, start the pressure rod cylinder to move the upper electrode upward, start the electrode cylinder to move the lower electrode outward, and remove the semi-finished product from the driven bracket support.

[0020] (6) Finished product welding: Repeat steps (1)-(4) above to finally complete the welding of the finished product of the double-break moving contact assembly. Then repeat step (5) and take away the finished product. The above steps are for welding double-break moving contact assemblies. If it is a single-break moving contact assembly, completing steps (1)-(4) will complete the welding of the finished product.

[0021] The beneficial effects of this invention are as follows: By setting the bottom of the moving contact in the shape of a raised rib and increasing the amount of silver filling on the contact welding surface, no additional solder is needed when welding the moving contact assembly. The product can be welded by resistance spot welding using the silver layer on the contact welding surface and the copper alloy moving bracket. There is no obvious gap in the weld area where the moving contact and the moving bracket are joined. The moving contact is embedded in the interior of the moving bracket. In this way, the two have both the chemical effect of silver-copper alloying and the physical combination of large plastic deformation, ultimately obtaining a high-quality joint strength. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0023] Figure 1 This is a structural diagram of the main moving contact assembly of the present invention;

[0024] Figure 2 This is a structural diagram of the moving contact in this invention;

[0025] Figure 3 This is a structural diagram of the welding device in this invention;

[0026] Figure 4 for Figure 3 Enlarged view of the structure at point C;

[0027] Figure 5 A simplified diagram showing the positioning of the movable support;

[0028] Figure 6 This is a structural diagram of the main assembly alignment device in this invention;

[0029] In the diagram, 1. Moving bracket; 2. Moving contact; 21. Protruding rib; 3. Upper electrode; 4. Moving bracket support seat; 41. Support component; 42. Support component end face; 5. Lower electrode; 6. Assembly alignment device; 61. Positioning clamp; 62. Positioning clamp moving cylinder; 63. Positioning clamp opening and closing cylinder; 7. Pressure rod cylinder; 8. Clamping cavity; 9. Electrode seat; 10. Electrode cylinder; 11. Support base. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0032] The directional and positional terms used in this invention, such as "up," "down," "front," "back," "left," "right," "inner," "outer," "top," "bottom," and "side," are merely for reference to the accompanying drawings. Therefore, the directional and positional terms used are for illustrating and understanding this invention, and not for limiting the scope of protection of this invention.

[0033] As shown in Figures 1-6, this is an embodiment of a circuit breaker moving contact assembly according to the present invention, including a moving bracket 1 and a moving contact 2 on the end face of the moving bracket 1. The moving bracket 1 is made of copper alloy, and the moving contact 2 is made of high-strength silver alloy (such as AgW, AgWC, etc.). The bottom of the welding surface of the moving contact 2 is provided with several raised ribs 21 arranged along the width. The welding surface of the moving contact 2 has sufficient silver infiltration for product welding. By setting the bottom of the moving contact 2 into the shape of raised ribs 21 and increasing the silver infiltration of the contact welding surface, no additional solder is needed when welding this moving contact assembly. The product can be welded to the copper alloy moving bracket 1 using a resistance spot welding process using the silver layer of the contact welding surface. There is no obvious gap in the weld area where the moving contact 2 and the moving bracket 1 are joined. The moving contact 2 is embedded inside the moving bracket 1. In this way, the two have both the chemical effect of silver-copper alloying and the physical combination of large plastic deformation, ultimately achieving a high-quality joint strength.

[0034] A welding device for a circuit breaker moving contact assembly is disclosed. The welding device includes an upper electrode 3, a moving support base 4, and two lower electrodes 5. The moving support base 4 supports a moving support 1 and has a support member 41 for supporting the moving support. The end face 42 of the support member is designed to fit snugly against the moving support 1. The upper electrode 3 presses the moving contact 2 against the moving support 1. The electrode structure adopts a traditional vertical conductive method with the upper electrode 3 and lower electrodes 5. The design consists of an upper electrode 3 and two symmetrically arranged lower electrodes 5 that abut against the moving support 1, enabling resistance spot welding. During welding, the moving support 1 and moving contact 2 are assembled sequentially. Welding of the moving contact assembly can be completed without adding any solder. After welding, the melt overflow around the moving contact 2 is uniform, and the weld bonding rate, metallographic properties, and shear strength performance indicators are good. The welding quality is consistent, the welding efficiency is high, and large-scale stable production of the product can be achieved.

[0035] This welding apparatus also includes an assembly alignment device 6, which includes a positioning clamp 61, a positioning clamp 61 opening / closing cylinder, a positioning clamp 61 moving cylinder, and a pressure rod cylinder 7 for driving the upper electrode 3 to rise and fall. When the positioning clamp 61 is closed, it forms a clamping cavity 8 that matches the shape of the moving contact 2. The positioning clamp 61 opening / closing cylinder drives the positioning clamp 61 to open or close, and the positioning clamp 61 moving cylinder drives the positioning clamp 61 to move above and outside the moving support 1. The assembly alignment device 6 is used to accurately place the moving contact 2 on the moving support 1. Before the positioning clamp 61 is opened, the moving contact 2 is pressed by the upper electrode 3, and the shape of the clamping cavity 8 can meet the welding requirements of moving contact assemblies of different specifications.

[0036] Each lower electrode 5 is equipped with an electrode holder 9 for a fixed electrode. One electrode holder 9 is equipped with an electrode cylinder 10 that drives it to move closer to or away from the other electrode holder 9. One lower electrode 5 serves as a stationary electrode, while the other lower electrode 5 moves as a movable electrode, simplifying the drive structure. Sufficient assembly space is provided for the movable support 1 before welding, facilitating rapid assembly by manual or machine assembly. A support base 11 is provided below the movable support support 4 for fixing the movable support support 4.

[0037] A welding method for a moving contact assembly of a circuit breaker, wherein the moving contact assembly is welded using any of the above-mentioned welding devices, and the welding method includes: for molded case circuit breakers, a single-break product has 1 moving contact 2, and a double-break product has 2 moving contacts 2; for frame circuit breakers, the number of moving contacts 2 is 1.

[0038] (1) Placement of moving bracket 1: Place the moving bracket 1 to be welded on the moving bracket support 4. The moving bracket 1, the moving bracket support 4, and the fixed electrode in the lower electrode group 5 are in close contact with each other; the material of the moving bracket 1 is copper alloy.

[0039] (2) Place the moving contact 2, start the opening and closing cylinder of the positioning clamp 61 and the moving cylinder of the positioning clamp 61. The width between the positioning clamps 61 should be slightly larger than the width of the moving contact 2 itself. Generally, the gap between the two is 0.3-0.5mm. At this time, the contact also falls on the welding surface of the bracket. The moving contact 2 is made of high-strength silver alloy material, such as AgW, AgWC, etc. The contact specifications are designed according to the required size based on the specific product current level. When designing the contact, its welding surface has several raised teeth. The tooth shape and number of the raised ribs 21 on the welding surface of the contact can be adjusted according to the specifications of the contact.

[0040] (3) Position the moving bracket 1 and the contact point, start the positioning clamp 61 opening and closing cylinder again, close the positioning clamp 61, clamp the moving contact 2 and the bracket so that the moving contact 2 and the moving bracket 1 are completely positioned in the front, back and left and right directions; then start the pressure rod cylinder 7 to move the upper electrode 3 vertically downward until it is close to the moving contact 2, start the positioning clamp 61 opening and closing cylinder again to separate the positioning clamp 61.

[0041] (4) Single-head welding: After completing all the above steps, it means that all the preparatory work before welding has been completed. Turn on the power of the resistance welding equipment, and heat the workpiece under the set welding current, welding time and welding pressure and other process parameters to complete the welding of a single moving contact 2 of the moving contact assembly.

[0042] (5) When the product is discharged, start the pressure rod cylinder 7 to move the upper electrode 3 upward, start the electrode cylinder 10 to move the lower electrode 5 outward, and take the semi-finished product off the driven bracket support 4.

[0043] (6) Finished product welding: Repeat steps (1)-(4) above to finally complete the welding of the finished product of the double-break moving contact assembly. Then repeat step (5) and take away the finished product. The above steps are for welding double-break moving contact assemblies. If it is a single-break moving contact assembly, completing steps (1)-(4) will complete the welding of the finished product.

[0044] Through the above technical solution, the welding method of this invention adopts resistance spot welding, which can achieve high-quality welding with the moving bracket 1 without adding any solder. After welding, the melt around the moving contact 2 is uniformly infiltrated, and the contact is deeply embedded in the bracket, forming a good physical and chemical bond. The welding performance indicators such as shear force and metallographic properties of the contact assembly are excellent, and it can well meet the various performance indicators of circuit breaker switch products. It solves the problem of contact detachment during the use of moving contact assemblies. The device and method of this invention can be used for large-scale stable production. It is easy to operate, low in cost, has high welding efficiency, and good welding quality consistency. Products mass-produced using the welding method of this invention have been fully verified by customers and can meet the stringent electrical life and high current breaking test performance requirements of high-end customers for high-current circuit breaker switch products.

[0045] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

[0046] While the invention has been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A circuit breaker moving contact assembly characterized by: The moving contact head assembly includes a moving bracket and a moving contact head, the moving bracket is made of copper alloy material, the moving contact head is made of high-strength silver alloy material, the bottom of the welding surface of the moving contact head is provided with a plurality of convex ribs arranged along the width, and the welding surface of the moving contact head is filled with sufficient silver filler for product welding; the convex ribs on the welding surface of the moving contact head are semicircular or grid-shaped, and the number of the convex ribs is at least two.

2. A welding apparatus for a circuit breaker moving contact assembly, characterized by: The welding device is used for welding the moving contact head assembly in the above claim 1, and the welding device includes an upper electrode, a moving bracket support seat and two lower electrodes, the moving bracket support seat is used for supporting the moving bracket, the moving bracket support seat is provided with a support for supporting the moving bracket, the end surface of the support is designed to be attached to the moving bracket, and the upper electrode is used for pressing the moving contact head against the moving bracket.

3. The circuit breaker moving contact assembly welding apparatus of claim 2, wherein: The assembly alignment device includes a positioning clamp, a positioning clamp opening and closing cylinder, a positioning clamp moving cylinder, and a pressure rod cylinder for driving the upper electrode to move up and down, the positioning clamp is designed to be closed to form a clamping cavity with a shape suitable for the moving contact head, the positioning clamp opening and closing cylinder is used for driving the positioning clamp to open or close, and the positioning clamp moving cylinder is used for driving the positioning clamp to move above the moving bracket and outside the moving bracket.

4. The circuit breaker moving contact assembly welding apparatus of claim 2 wherein: The lower electrodes are respectively provided with electrode seats for fixing the electrodes, and one of the electrode seats is provided with an electrode cylinder for driving the electrode to move close to or away from the other electrode seat.

5. The circuit breaker moving contact assembly welding apparatus of claim 2 wherein: The moving bracket support seat is provided below the support base for fixing the moving bracket support seat.

6. A method of welding a circuit breaker moving contact assembly, characterized by: The moving contact head assembly is welded by using the welding device in any one of the above claims 2-5, no solder is needed during the whole welding process of the product, and the welding method includes the following steps: (1) Step one: placing the moving bracket, placing the moving bracket to be welded on the moving bracket support seat, and the moving bracket is attached to the moving bracket support seat and the fixed electrodes in the lower electrode group; the material of the moving bracket is copper alloy; (2) Step two: placing the moving contact head, starting the positioning clamp opening and closing cylinder and the positioning clamp moving cylinder, the width of the positioning clamp is slightly larger than the width of the moving contact head, and the gap between them is generally 0.3-0.5mm, at this time the contact head is just on the welding surface of the bracket; the material of the moving contact head is high-strength silver alloy material, such as AgW or AgWC, the size of the contact head is designed according to the current level of the specific product, and the welding surface of the contact head has a plurality of convex teeth, and the convex rib teeth shape and number of the contact head welding surface can be adjusted according to the size of the contact head; (3) Step three: positioning the moving bracket and the contact head, starting the positioning clamp opening and closing cylinder again, closing the positioning clamp, clamping the moving contact head and the bracket to completely position the moving contact head and the moving bracket in the front, back, left and right directions; then start the pressure rod cylinder to move the upper electrode vertically downward until it is attached to the moving contact head, and start the positioning clamp opening and closing cylinder again to separate the positioning clamp; (4) Step four: single-head welding, after the above steps are completed, it means that all the preparation work before welding is completed, the power supply of the resistance welding device is started, the workpiece is heated under the set process parameters such as welding current, welding time and welding pressure, and the welding of the single moving contact head of the moving contact head assembly is completed. (5) Step five: product discharge, start the pressure rod cylinder, make the upper electrode move upward, start the electrode cylinder, make the lower electrode move outward, take away the semi-finished product from the driven support support seat; (6) Step six: finished product welding, repeat the above steps (1)-(4), finally complete the welding of the double-break moving contact assembly finished product, and then repeat step (5) to take away the finished product. The above steps are for the welding of the double-break moving contact assembly. If it is a single-break moving contact assembly, steps (1)-(4) can be completed to complete the welding of the finished product.

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