A method of machining contacts for a two-piece machined vacuum interrupter

Abstract

The application relates to a two-body machining vacuum arc-extinguishing chamber contact machining method, which comprises the following steps: S1: adopting a sheet milling cutter machining method to respectively cut two contact cups to obtain two contact cups with a 120-degree inclined groove rotation angle; S2: adopting a brazing machining method to braze the two contact cups with a 120-degree inclined groove rotation angle to obtain a combined contact cup; and S3: performing turning machining on the combined contact cup to obtain a 240-degree inclined groove rotation angle contact cup. The method can not only ensure the miniaturization of the contact cup, but also significantly improve the magnetic field strength of the cup-shaped contact cup and the breaking current capacity, and belongs to the technical field of vacuum arc-extinguishing chambers.

Description

Technical Field

[0001] This invention relates to the field of vacuum interrupter technology, and more specifically to a method for processing vacuum interrupter contacts using a two-body processing method. Background Technology

[0002] Typically, to ensure the breaking capacity of a vacuum interrupter, a cup-shaped longitudinal magnetic contact is used to control the arc. To meet the requirements of high breaking current and high rated current, the rotation angle of the cup-shaped contact structure needs to be increased to enhance the longitudinal magnetic field.

[0003] Currently, cup-shaped contact structures are all machined using end mills. However, due to limitations in current machining technology, the cup angle of cup-shaped contacts machined using end mills cannot exceed 120 degrees. This results in a relatively weak longitudinal magnetic field strength and limited arc control. The only way to improve their current-breaking capacity is to increase the size of the contact cup and the arc-erosion area.

[0004] Cup-shaped contacts machined with end mills can achieve large turning angles of 240 degrees and above. However, considering the cutting stress required by the end mill, the length-to-diameter ratio must be greater than 5:1, and the groove width must be at least 5mm. The corresponding contact cup wall thickness must be more than 25mm, resulting in a contact cup that is too large and too thick. This solution is not conducive to contact miniaturization. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the purpose of this invention is to provide a two-body processing method for vacuum interrupter contacts, which solves the problems of insufficient longitudinal magnetic field strength of existing contact cups, weak arc control capability, or excessively large and thick contact cup sizes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for machining the contacts of a vacuum interrupter using a two-body machining process includes the following steps: S1: machining the two contact cups separately using a milling cutter to obtain two contact cups with a 120-degree slant angle; S2: brazing the two contact cups with a 120-degree slant angle to obtain a combined contact cup; S3: turning the combined contact cup to obtain a contact cup with a 240-degree slant angle.

[0008] As a preferred embodiment, in step S1, the contact cup is a cylindrical longitudinal magnetic contact cup, which has a closed end and an open end. The open end is the mouth of the contact cup, and the closed end has a central hole that penetrates through the closed end.

[0009] As a preferred embodiment, in step S1, before the contact cup is machined, the following pretreatment steps are performed: a) the contact cup is secured to the bolt by passing a bolt through the center hole of the contact cup and locking it to the bolt with a nut; b) the cup opening of the contact cup is oriented towards the end mill, and the tilt angle of the contact cup relative to the end mill is adjusted to determine the feed direction of the end mill; c) a three-jaw chuck is mounted on the milling machine, and the bolt is fixed by the three-jaw chuck, thereby fixing the contact cup and determining the tilt angle of the groove of the contact cup; d) the milling machine is started, causing the end mill to rotate and machine the contact cup.

[0010] As a preferred option, the number of entry points for the contact cup is two, and the included angle between the two entry points is 90 degrees. After completing the pre-processing steps of the contact cup to be processed, the end mill machining method is as follows: d1: The end mill enters the contact cup from one entry point and cuts along the axial direction of the contact cup until it reaches the cutting endpoint, after which the end mill retracts in the opposite direction of the entry; d2: The contact cup is rotated 90 degrees, and the end mill enters from the other entry point and the machining process of step d1 is repeated to complete the cutting of the contact cup and obtain a contact cup with a 120-degree slant angle.

[0011] As a preferred embodiment, with the center of the contact cup as the center, the angle between each infeed point and its corresponding cutting endpoint in the vertical projection direction is 120 degrees.

[0012] As a preferred option, the brazing process in step S2 consists of the following steps: e: placing the two contact cups with their openings facing each other and in contact with each other, and placing a solder sheet between the openings of the two contact cups to complete the initial assembly; f: placing the two contact cups initially assembled in step e into a vacuum brazing furnace to melt the solder sheet and obtain the combined contact cups.

[0013] As a preferred option, the solder sheet is a silver-copper 28 solder sheet.

[0014] As a preferred option, in step S3, the closed end of the combined contact cup is machined by a lathe. The lathe machine is machined along the radial direction of the combined contact cup until the cross section at the cutting endpoint is reached, thus obtaining a 240-degree inclined groove corner contact cup.

[0015] As a preferred option, the wall thickness of the 240-degree inclined groove corner contact cup shall not exceed 10 mm, and the width of the inclined groove shall not exceed 3 mm.

[0016] As a preferred option, the thickness of the end mill should not exceed 3mm.

[0017] In summary, the present invention has the following advantages:

[0018] 1. The method of this invention solves the difficulty of increasing the rotation angle of the contact cup in end mill machining. Through three methods—end mill machining, brazing, and turning—a 240-degree rotation angle effect previously only achievable with end mill machining is achieved. This effectively increases the longitudinal magnetic field strength of the contact cup (from...). Figure 4 It can be seen that at the peak current, the longitudinal magnetic field strength of the four-slot cup increases with the rotation angle α, where the rotation angle α is the angle of the inclined slot; the larger the inclined slot rotation angle of the contact cup, the longer the current path and the greater the longitudinal magnetic field strength.

[0019] 2. The method of this invention solves the size problem of the contact cup. By using end mills, brazing, and turning, it cleverly avoids the length-to-diameter ratio greater than 5:1 required by end mills due to cutting stress. The width of the inclined groove of the contact cup can be the same as that of the end mill (2-3mm), and the wall thickness of the contact cup can be 10mm or even less. Unlike end mills, which require a 5mm wide inclined groove and a wall thickness of more than 25mm, this invention effectively reduces the size of the contact cup while meeting the breaking capacity requirement. Attached Figure Description

[0020] Figure 1 This is a 3D view of a 240-degree inclined groove corner contact cup.

[0021] Figure 2 This is the front view of the assembled contact cup.

[0022] Figure 3 This is a top view of the contact cup.

[0023] Figure 4 This is a curve showing the longitudinal magnetic field strength corresponding to the angle of the inclined slot rotation.

[0024] Figure 5 This is a top view of a contact cup machined by a milling cutter in the prior art.

[0025] Figure 6 This is a perspective view of a contact cup machined by a vertical milling cutter in the prior art.

[0026] Wherein, 1 is the contact cup, 2 is the mouth of the contact cup, 3 is the closed end of the contact cup, 4 is the inclined groove, 5 is the center hole, A is the cutting endpoint, and B is the entry point. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to specific embodiments.

[0028] A method for machining the contacts of a vacuum interrupter using a two-body machining process includes the following steps: S1: machining the two contact cups separately using a milling cutter to obtain two contact cups with a 120-degree slant angle; S2: brazing the two contact cups with a 120-degree slant angle to obtain a combined contact cup; S3: turning the combined contact cup to obtain a contact cup with a 240-degree slant angle.

[0029] In step S1, the contact cup is a cylindrical longitudinal magnetic contact cup. The contact cup has a closed end and an open end. The open end is the mouth of the contact cup, and the closed end has a central hole that passes through the closed end.

[0030] In step S1, before the contact cup is machined, the following pretreatment steps are performed: a: The contact cup is secured to the bolt by passing a bolt through the center hole of the contact cup and using a nut; b: The cup opening of the contact cup is oriented towards the end mill, and the tilt angle of the contact cup relative to the end mill is adjusted to determine the feed direction of the end mill; c: A three-jaw chuck is mounted on the milling machine, and the bolt is fixed by the three-jaw chuck, thereby fixing the contact cup and determining the tilt angle of the groove of the contact cup; d: The milling machine is started, and the end mill rotates to machine the contact cup.

[0031] There are two entry points for the contact cup, and the included angle between the two entry points is 90 degrees. After completing the pre-processing steps of the contact cup to be machined, the end mill machining method is as follows: d1: The end mill enters the contact cup from one entry point B at R / 2, and moves along... Figure 3 The cutting process begins with the end mill feeding along the Y-axis of the contact cup. The end mill is inclined relative to the contact cup, and the cutting depth is R. The cutting continues until the cutting endpoint A is reached, at which point the angle of the slant groove is exactly 120 degrees. The end mill then retracts in the opposite direction of the feed. d2: The contact cup is rotated 90 degrees. This 90-degree rotation is relative to the fixed position of the contact cup in step c above. The cutting process begins from another feed point, and the machining process of step d1 is repeated. This process completes the cutting of the contact cup, resulting in a contact cup with a 120-degree slant groove.

[0032] With the center of the contact cup as the center, the angle between each infeed point and its corresponding cutting endpoint in the vertical projection direction is 120 degrees.

[0033] In step S2, the brazing process involves the following steps: e: The cup openings of two contact cups with a 120-degree angled groove are positioned facing each other and in contact with each other (keeping the grooves aligned at the cup openings without misalignment, i.e., the grooves of the two contact cups are interconnected). A piece of solder is placed between the cup openings of the two contact cups with a 120-degree angled groove to complete the initial assembly; f: The two contact cups initially assembled in step e are placed in a vacuum brazing furnace to melt the solder piece, resulting in a combined contact cup.

[0034] The solder sheet is a silver-copper 28 solder sheet.

[0035] The principle of brazing: Because vacuum furnace brazing is sensitive to impurities below the melting temperature of the solder, surface treatment of the parts is required. Its polishing technology is based on plasma chemistry and electrochemistry, and this process is a leading plasma processing method integrating polishing, degreasing, and oxide scale removal. It can effectively reduce the surface roughness of metal parts, improve surface brightness, and enhance the corrosion resistance of the parts. In a macroscopic sense: At the beginning of polishing, as the polishing slurry comes into contact with the workpiece surface, the polishing slurry is first electrolyzed. The anodic reaction is as follows:

[0036] 4OH-→2H2O+O2+4e-;

[0037] The generated oxygen adheres to the workpiece surface, isolating the workpiece from the polishing fluid. A high voltage is formed at both ends of the gas layer. In the presence of plasma, an electron beam is generated, which strikes the convex and concave parts of the anode workpiece, giving the part a mirror-like surface. After surface treatment, two contact cups with a 120-degree angled groove are assembled. A piece of silver-copper 28 solder is placed at the contact point between the two contact cups. This solder melts at high temperature and forms a strong metallographic structure after brazing with copper, thus completing the vacuum welding. After assembly, the parts are sent to a vacuum brazing furnace. The vacuum furnace heats the parts to the point where the silver-copper 28 solder melts, causing the upper and lower contact cup ends to be brazed together, forming a combined contact cup.

[0038] In step S3, the closed end of the combined contact cup is machined by a lathe. The lathe machine is machined along the radial direction of the combined contact cup until the cross section at the cutting endpoint is reached, resulting in a 240-degree inclined groove corner contact cup.

[0039] The wall thickness of the 240-degree inclined groove corner contact cup shall not exceed 10mm, and the width of the inclined groove shall not exceed 3mm.

[0040] The thickness of the end mill should not exceed 3mm.

[0041] In this embodiment, as Figures 1-4 As shown, the specific process of the method is as follows:

[0042] 1. For example Figure 3 The end mill enters from point B (R / 2) on a single contact cup (entry point), along the contact Y-axis ( Figure 3 (dashed line) direction, parallel inward feed (e.g.) Figure 3Cutting is performed as shown by the arrow. During the feed, the contact cup remains stationary, and the end mill only moves along the Y-axis, with zero velocity in other directions. The feed amount is radius R. After the end mill reaches point A (the cutting endpoint) along the Y-axis, it retracts in the opposite direction of the feed. The angle formed by points A and B with the center of the circle is 120 degrees, which is also called the 120-degree slant angle of the contact cup. After completing the above process, the contact cup is rotated 90 degrees, and the process is repeated. This process produces a contact cup with a 120-degree slant angle.

[0043] 2. After completing the machining of the first contact cup, repeat the machining process in step 1 with the same blank to finally achieve the machining of two completely identical contact cups with a limit skew angle of 120 degrees using a disc milling cutter.

[0044] 3. After the end mill is completed, the two parts mentioned above are as follows: Figure 2 As shown in the diagram, a piece of silver-copper 28 solder needs to be placed at the contact point between the two contact cups. This solder melts at high temperatures and brazes with copper to form a strong metallographic structure, thus completing the vacuum welding. After assembly, the parts are placed in a vacuum brazing furnace. The vacuum furnace heats the parts to the point where the silver-copper 28 solder melts, causing the end faces of the upper and lower contact cups to be brazed together, forming a single, integrated contact cup. The silver-copper 28 solder refers to a size 28 silver-copper solder sheet.

[0045] 4. After brazing is completed, the parts are machined using turning technology along... Figure 2 Along the central axis, the upper half is machined to create a new flat surface for the contact cup, while simultaneously meeting the requirement of a 240° rotation angle. The overall 240° rotation angle contact cup after machining is shown in the image. Figure 1 ).

[0046] Depend on Figure 4 It can be seen that at the peak current moment, the longitudinal magnetic field strength of the four-slot cup increases with the rotation angle α, where the rotation angle α is the angle of the inclined slot. The larger the rotation angle of the inclined slot of the contact cup, the longer the current path and the greater the longitudinal magnetic field strength.

[0047] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method of machining contacts for a two-piece machined vacuum interrupter, characterized by, The method includes the following steps: S1: The two contact cups are machined by using a milling cutter to obtain two contact cups with a 120-degree slant angle. S2: The two inclined slots with a rotation angle of 120 degrees are brazed to obtain a combined contact cup; S3: The combined contact cup is machined by turning to obtain a 240-degree inclined groove corner contact cup.

2. The method for machining vacuum interrupter contacts using a two-body machining process according to claim 1, characterized in that: In step S1, the contact cup is a cylindrical longitudinal magnetic contact cup. The contact cup has a closed end and an open end. The open end is the mouth of the contact cup, and the closed end has a central hole that passes through the closed end.

3. A method of machining two-piece vacuum interrupter contact pieces according to claim 2, characterized in that: In step S1, before the contact cup undergoes machining, the following pretreatment steps are performed. a: Pass the bolt through the center hole of the contact cup and tighten the contact cup onto the bolt with a nut; b: Position the contact cup with the end mill facing the end mill, and adjust the tilt angle of the contact cup relative to the end mill to determine the feed direction of the end mill; c: The three-jaw chuck is installed on the milling machine, and the bolts are fixed by the three-jaw chuck, thereby fixing the contact cup and determining the inclination angle of the contact cup's groove; d: Start the milling machine to make the end mill rotate and cut the contact cup.

4. A method of machining two-piece vacuum interrupter contact pieces according to claim 3, characterized in that: The contact cup has two entry points, with an included angle of 90 degrees. After completing the pre-processing steps for the contact cup, the end mill machining method is as follows: d1: The end mill enters the contact cup from one of the infeed points and cuts along the axis of the contact cup until it reaches the cutting endpoint. Then the end mill retracts in the opposite direction of the infeed. d2: Rotate the contact cup 90 degrees, enter the tool from another entry point, and repeat the machining process of step d1 to complete the cutting of the contact cup and obtain a contact cup with a 120-degree slant angle.

5. A method of machining two-piece vacuum interrupter contacts as defined in claim 4 wherein: With the center of the contact cup as the center, the angle between each infeed point and its corresponding cutting endpoint in the vertical projection direction is 120 degrees.

6. A method for machining a vacuum interrupter contact using a two-body machining process according to claim 5, characterized in that: In step S2, the brazing process involves the following steps: e: Position the two contact cups with their openings facing each other and make contact with each other. Place a solder sheet between the openings of the two contact cups to complete the initial assembly. f: Place the two contact cups that were initially assembled in step e into a vacuum brazing furnace to melt the solder sheet and obtain the combined contact cups.

7. A method of machining two-piece vacuum interrupter contacts as defined in claim 6 wherein: The solder sheet is a silver-copper 28 solder sheet.

8. A method for machining vacuum interrupter contacts using a two-body machining process according to claim 6, characterized in that: In step S3, the closed end of the combined contact cup is machined by a lathe. The lathe machine is machined along the radial direction of the combined contact cup until the cross section at the cutting endpoint is reached, resulting in a 240-degree inclined groove corner contact cup.

9. A method of machining two-piece vacuum interrupter contacts as defined in claim 8 wherein: The wall thickness of the 240-degree inclined groove corner contact cup shall not exceed 10mm, and the width of the inclined groove shall not exceed 3mm.

10. A method of machining two-piece vacuum interrupter contacts as defined in claim 5 wherein: The thickness of the end mill should not exceed 3mm.

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