A round power battery negative electrode top cover connecting piece welding anti-false welding tool

Abstract

The utility model relates to power battery manufacturing equipment technical field discloses a kind of circular power battery negative pole top cover connecting piece welding false welding tool, to solve the problem of not close, easy false welding when rivet welding of circular power battery negative pole busbar. The tool includes tool base plate, positioning assembly, elastic mechanism, pressing mechanism, accurate positioning is realized by positioning assembly, elastic mechanism and pressing mechanism form bidirectional stress, ensure that welding surface is closely attached. The utility model makes false welding rate to 0, welding qualified rate reaches more than 99.8%, and is suitable for large capacity lithium iron phosphate battery top cover manufacturing.

Description

Technical Field

[0001] This utility model relates to the field of power battery manufacturing equipment technology, and more specifically, to a welding fixture for preventing false welding of the connecting piece of the negative electrode top cover of a circular power battery. Background Technology

[0002] In the manufacturing process of circular power batteries, the welding quality of the busbar and rivets on the negative electrode top cover directly affects the structural stability, safety and service life of the battery.

[0003] Existing welding fixtures have significant drawbacks: firstly, low positioning accuracy, leading to easy misalignment between the negative electrode busbar and the rivet, resulting in welding deviations; secondly, poor fit, relying solely on pressure or gravity in one direction for contact during welding, easily creating gaps and resulting in a false weld rate as high as 15%; furthermore, low production efficiency, cumbersome manual positioning and welding operations, and long welding time per unit. These problems severely impact the production quality and efficiency of power batteries. Therefore, there is an urgent need to design a precise positioning, tight-fitting anti-false weld fixture to solve these issues. Utility Model Content

[0004] This invention aims to solve the problem of poor adhesion and easy incomplete welding when welding the negative electrode busbar of a circular power battery to the rivet.

[0005] To address the aforementioned issues, this utility model provides a welding fixture for preventing incomplete welds on the connecting piece of a circular power battery negative electrode top cover. This fixture is used for welding the negative electrode busbar and rivets. It includes a base plate and further comprises: a positioning component disposed on the upper surface of the base plate to define the position of the negative electrode busbar; an elastic mechanism equidistantly disposed within the base plate to support the rivets and provide an upward pushing force; and a pressing mechanism disposed above the base plate to press down on the negative electrode busbar, forming a bidirectional force with the elastic mechanism.

[0006] This utility model provides a welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery. Compared with the prior art, it has the following beneficial effects, but is not limited to: To address the issue of loose fit and prone to incomplete welds when welding the negative electrode current collector of a circular power battery to rivets, this fixture first uses bolts to horizontally fix the fixture base plate to the welding workbench, ensuring a gapless fit. The positioning component is installed on the upper surface of the fixture base plate according to the size of the negative electrode current collector. The elastic mechanism is precisely positioned according to the number and spacing of the rivets to be welded. The pressing mechanism is fixed directly above the fixture base plate by a metal bracket. The positioning component limits the horizontal displacement of the negative electrode current collector through physical restraint, preventing displacement during welding. When the elastic mechanism is in its naturally extended state, it pushes the rivets upwards, causing the rivet tip to initially contact the lower surface of the current collector. The pressing mechanism applies downward pressure, creating a bidirectional force that is opposite in direction and matched in magnitude to the upward force of the elastic mechanism, tightly pressing the rivet and current collector together. This provides a gapless fit for welding, allowing for laser welding. The bidirectional force system ensures a tight fit between the rivet and current collector welding surfaces, completely eliminating the root cause of incomplete welds and resulting in better performance.

[0007] Furthermore, the positioning component includes a positioning post, which is fixed to the upper surface of the tooling base plate, and the negative electrode busbar has a positioning hole adapted to the positioning post.

[0008] Furthermore, the top of the positioning post is semi-circular.

[0009] Furthermore, the elastic mechanism includes a baffle, a compression spring, and a limiting component; the bottom of the tooling base plate has an installation groove, the baffle is fixed in the installation groove, the upper surface has a groove, and the compression spring is placed in the groove; the limiting component is located on top of the compression spring and is used to support the rivet.

[0010] Furthermore, the limiting component includes an integrated movable block and a limiting seat; the top inner wall of the mounting groove is provided with a movable groove, and the movable block is movably disposed in the movable groove; the upper surface of the tooling base plate is provided with a movable hole communicating with the movable groove, the limiting seat is disposed in the movable hole, and the upper surface is provided with a placement groove for placing rivets.

[0011] Furthermore, the outer wall of the movable block is in close contact with the wall of the movable groove, and the outer wall of the limiting seat is in close contact with the wall of the movable hole.

[0012] Furthermore, the limiting component is made of brass.

[0013] Furthermore, the pressing mechanism includes a telescopic cylinder and a pressing plate; the telescopic end of the telescopic cylinder is fixedly connected to the pressing plate, and the bottom of the pressing plate is provided with abutment pieces that are evenly distributed and correspond one-to-one with the rivets.

[0014] Furthermore, the abutment piece is annular and aligned with the upper surface of the part where the negative busbar connects to the rivet.

[0015] Furthermore, the lower pressure plate has a welding hole on its lower surface, which is located at the center of the support piece; the upper surface of the lower pressure plate has a welding groove that communicates with the welding hole, and the cross-section of the welding groove is conical. Attached Figure Description

[0016] Figure 1 This is a first-view structural schematic diagram of a welding anti-fraud tooling for a circular power battery negative electrode top cover connecting piece according to an embodiment of the present invention. Figure 2 This is a second-view structural schematic diagram of a welding anti-fragmentation fixture for a circular power battery negative electrode top cover connecting piece according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the pressing mechanism in a welding anti-fragmentation fixture for the connecting piece of a circular power battery negative electrode top cover according to an embodiment of the present invention. Figure 4 This is a first-view structural diagram of the tooling base plate in a circular power battery negative electrode top cover connecting piece welding anti-false weld tooling according to an embodiment of the present utility model. Figure 5 This is a half-sectional view of the tooling base plate in a welding anti-fragmentation tooling for a circular power battery negative electrode top cover connecting piece according to an embodiment of the present utility model. Figure 6 for Figure 5 Enlarged structural diagram at point A in the diagram; Figure 7 This is a second-view structural diagram of the tooling base plate in a welding anti-fraud tooling for the connecting piece of a circular power battery negative electrode top cover according to an embodiment of this utility model.

[0017] Explanation of reference numerals in the attached figures: 1. Tooling base plate; 2. Negative electrode busbar; 3. Rivet; 4. Pressing mechanism; 41. Pressing plate; 42. Telescopic cylinder; 43. Welding groove; 44. Support plate; 45. Welding hole; 5. Elastic mechanism; 51. Baffle; 52. Compression spring; 53. Limiting assembly; 531. Movable block; 532. Limiting seat; 54. Mounting groove; 55. Movable groove; 6. Positioning post. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the description, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this utility model, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] Furthermore, in the attached diagram, the X-axis represents the horizontal direction, that is, the left and right position, and the positive direction of the X-axis (that is, the direction the arrow points to) represents the right, and the negative direction of the X-axis (that is, the direction opposite to the positive direction of the X-axis) represents the left; in the attached diagram, the Y-axis represents the vertical direction, that is, the front and back position, and the positive direction of the Y-axis (that is, the direction the arrow points to) represents the front, and the negative direction of the Y-axis (that is, the direction opposite to the positive direction of the Y-axis) represents the back; in the attached diagram, the Z-axis represents the vertical direction, that is, the up and down position, and the positive direction of the Z-axis (that is, the direction the arrow points to) represents the up, and the negative direction of the Z-axis (that is, the direction opposite to the positive direction of the Z-axis) represents the down.

[0022] It should also be noted that the aforementioned X-axis, Y-axis and Z-axis are only for the purpose of facilitating the description of this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, parts, or groups of features, integers, steps, or parts.

[0025] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0026] See Figures 1-7 This utility model discloses a welding anti-fraying fixture for connecting the negative electrode top cover of a circular power battery, used for welding operations between the negative electrode busbar 2 and the rivet 3. It includes a fixture base plate 1, and further includes: a positioning component disposed on the upper surface of the fixture base plate 1 to define the position of the negative electrode busbar 2; an elastic mechanism 5 equidistantly disposed in the fixture base plate 1 to support the rivet 3 and provide an upward pushing force; and a pressing mechanism 4 disposed above the fixture base plate 1 to press down against the negative electrode busbar 2, forming a bidirectional force with the elastic mechanism 5.

[0027] In this embodiment, to address the problem of loose fit and easy incomplete welding when welding the circular power battery negative electrode busbar 2 to the rivet 3, the tooling is first horizontally fixed to the welding workbench with bolts to ensure a seamless fit. The positioning component is installed on the upper surface of the tooling base plate 1 according to the size of the negative electrode busbar 2. The elastic mechanism 5 is precisely arranged according to the number and spacing of the rivets 3 to be welded. The pressing mechanism 4 is fixed directly above the tooling base plate 1 by a metal bracket. The positioning component limits the negative electrode busbar through physical limiting. The horizontal displacement of plate 2 prevents the busbar from shifting during welding; when the elastic mechanism 5 is in its naturally extended state, it pushes the rivet 3 upward, so that the tip of the rivet 3 initially contacts the lower surface of the busbar; the pressing mechanism 4 applies downward pressure, which, together with the pushing force of the elastic mechanism 5, forms a bidirectional force that is opposite in direction and matches in magnitude, pressing the rivet 3 tightly against the busbar, providing a gapless fit for welding. At this point, laser welding is performed. The bidirectional force system ensures that the welding surface of the rivet 3 and the busbar is tightly fitted, completely eliminating the root cause of incomplete welding and resulting in better performance.

[0028] Optional, please refer to Figure 4 and Figure 7 The positioning component includes a positioning post 6, which is fixed to the upper surface of the tooling base plate 1, and the negative electrode busbar 2 has a positioning hole adapted to the positioning post 6.

[0029] In this embodiment, the positioning post 6 is made of stainless steel and is vertically welded to the preset position on the tooling base plate 1 by argon arc welding. After welding, the weld is ground to ensure that the axis of the positioning post 6 is perpendicular to the tooling base plate 1. According to the diameter of the positioning post 6, a positioning hole is opened on the surface of the negative electrode busbar 2 using laser drilling. The diameter of the positioning hole is 0.1mm larger than the diameter of the positioning post 6 to form a clearance fit, which ensures positioning accuracy and facilitates the quick insertion of the busbar. The negative electrode busbar 2 forms a nested fit with the positioning post 6 on the tooling base plate 1 through the positioning hole on its surface, ensuring that the welding target point on the busbar is accurately aligned with the rivet 3 supported below, providing basic positioning guarantee for subsequent welding.

[0030] Optional, please refer to Figure 4 and Figure 7 The top of the positioning post 6 is semi-circular.

[0031] In this embodiment, after the positioning post 6 is welded and fixed, its top end is machined using a CNC lathe to form a semi-circular structure. The radius of the semi-circle is consistent with the diameter of the positioning post 6, ensuring a smooth transition of the top surface without sharp edges or burrs. After machining, the top end is polished with sandpaper, and the surface roughness is controlled within Ra0.8μm. During the process of fitting the busbar into the positioning post 6, the curved surface structure of the semi-circular top end plays a guiding role, enabling the positioning hole to quickly align with the positioning post 6, while avoiding rigid friction between the traditional sharp tip and the edge of the busbar positioning hole.

[0032] Optional, please refer to Figure 4 , Figure 5 , Figure 6 and Figure 7 The elastic mechanism 5 includes a baffle 51, a compression spring 52, and a limiting component 53; the bottom of the tooling base plate 1 is provided with an installation groove 54, the baffle 51 is fixed in the installation groove 54, the upper surface is provided with a groove, and the compression spring 52 is placed in the groove; the limiting component 53 is provided on the top of the compression spring 52 and is used to support the rivet 3.

[0033] In this embodiment, a mounting groove 54 is milled at the bottom of the tooling base plate 1 using a milling machine. The baffle 51 is fixed in the mounting groove 54 by hexagonal socket bolts. A circular groove is drilled at the center of the upper surface of the baffle 51. After the compression spring 52 is placed in the groove, the limiting component 53 is placed on top of the compression spring 52. The baffle 51 provides bottom support and limits the compression spring 52, preventing the compression spring 52 from shifting laterally when under force. The groove constrains the radial displacement of the compression spring 52, ensuring that the elastic force of the compression spring 52 is always transmitted axially. The limiting component 53 directly supports the rivet 3. When the busbar is pressed by the pressing mechanism 4, the rivet 3 pushes the limiting component 53 downward, compressing the compression spring 52 and generating a reverse thrust. This thrust and the pressure of the pressing mechanism 4 form a bidirectional force, making the rivet 3 and the busbar fit tightly together.

[0034] Optional, please refer to Figure 6 and Figure 7 The limiting component 53 includes an integrated movable block 531 and a limiting seat 532; the top inner wall of the mounting groove 54 is provided with a movable groove 55, and the movable block 531 is movably disposed in the movable groove 55; the upper surface of the tooling base plate 1 is provided with a movable hole communicating with the movable groove 55, the limiting seat 532 is disposed in the movable hole, and the upper surface is provided with a placement groove for placing rivets 3.

[0035] In this embodiment, the movable block 531 and the limiting seat 532 are integrally machined. A movable groove 55 matching the size of the movable block 531 is milled on the top inner wall of the mounting groove 54. The depth of the movable groove 55 is greater than the height of the movable block 531, allowing the movable block 531 to move up and down within it. A movable hole communicating with the movable groove 55 is machined on the upper surface of the tooling base plate 1. The diameter of the movable hole matches the diameter of the limiting seat 532. The integrated limiting component 53 is inserted into the movable groove 55, causing the limiting seat 532 to embed and extend through the movable hole onto the upper surface of the tooling base plate 1. A circular placement groove adapted to the bottom of the rivet 3 is machined on the upper surface of the limiting seat 532. When the compression spring 52 extends or retracts, the movable block 531 slides axially within the movable groove 55, causing the limiting seat 532 to rise and fall synchronously, ensuring that the rivet 3 always moves vertically and maintains surface contact with the busbar.

[0036] Optional, please refer to Figure 6 and Figure 7 The outer wall of the movable block 531 is in close contact with the wall of the movable groove 55, the outer wall of the limiting seat 532 is in close contact with the wall of the movable hole, and the inner diameter of the movable groove 55 is larger than the inner diameter of the movable hole.

[0037] In this embodiment, the tight fit not only restricts the lateral displacement of the limiting component 53, but also provides sufficient space for its axial lifting and lowering, avoiding positioning deviations caused by excessive gaps, and preventing lifting and lowering jams caused by insufficient gaps. The large contact area between the movable block 531 and the movable groove 55 also serves as a guide, ensuring that the limiting component 53 always moves axially, further improving the positioning accuracy of the rivet 3.

[0038] Optionally, the limiting component 53 is made of brass.

[0039] In this embodiment, the limiting component 53 is made of brass, which has excellent thermal conductivity and machinability. After processing, the limiting component 53 undergoes surface passivation treatment to enhance its corrosion resistance and prevent rust caused by sweat, oil, etc., during use, which would affect the smoothness of the component's lifting and lowering. The high temperature generated during laser welding is transferred to the limiting component 53 through the rivet 3. The high thermal conductivity of brass allows the heat to be quickly transferred from the limiting component 53 to the tooling base plate 1, and then dissipated into the air by the tooling base plate 1, avoiding high temperature accumulation that could cause the compression spring 52 to fail due to heat. At the same time, the excellent machinability of brass ensures that the limiting component 53 can meet the high-precision fitting requirements.

[0040] Optional, please refer to Figure 1 , Figure 2 and Figure 3 The pressing mechanism 4 includes a telescopic cylinder 42 and a pressing plate 41. The telescopic end of the telescopic cylinder 42 is fixedly connected to the pressing plate 41. The bottom of the pressing plate 41 is provided with abutment pieces 44 that are evenly distributed and correspond one-to-one with the rivets 3. The abutment pieces 44 are in the shape of a ring and are aligned with the upper surface of the part where the negative electrode busbar 2 and the rivet 3 meet.

[0041] In this embodiment, the telescopic cylinder 42 is fixed to the metal bracket via a flange. The lower pressure plate 41 is fixedly connected to the telescopic end of the telescopic cylinder 42 with bolts, ensuring a firm and secure connection. The abutment pieces 44 are made of stainless steel and are welded to the bottom of the lower pressure plate 41 according to the distribution spacing of the rivets 3. The position of each abutment piece 44 corresponds one-to-one with the elastic mechanism 5 below. When the tooling receives a welding signal, the pneumatic control system drives the telescopic end of the telescopic cylinder 42 to extend downward, causing the lower pressure plate 41 to move downward synchronously until the abutment piece 44 contacts the upper surface of the manifold and applies pressure. After welding is completed, the telescopic end of the telescopic cylinder 42 returns to its original position, causing the lower pressure plate 41 to move away from the manifold, facilitating the removal of the welded product. The one-to-one correspondence design of the abutment pieces 44 ensures that each rivet 3 is subjected to uniform downward pressure.

[0042] Optional, please refer to Figure 1 , Figure 2 and Figure 3 The lower pressure plate 41 has a welding hole 45 on its lower surface, which is located at the center of the support piece 44; the upper surface of the lower pressure plate 41 has a welding groove 43 that communicates with the welding hole 45, and the cross-section of the welding groove 43 is conical.

[0043] In this embodiment, a 5mm diameter welding hole 45 is drilled on the lower surface of the lower pressure plate 41 at the center of the supporting piece 44, and the welding hole 45 penetrates the lower pressure plate 41. On the upper surface corresponding to the welding hole 45, a conical welding groove 43 is machined using a tapered milling cutter. The large end of the welding groove 43 has a diameter of 10mm, the small end has the same diameter as the welding hole 45, and the depth is 5mm, ensuring smooth communication between the welding groove 43 and the welding hole 45. During laser welding, the laser beam enters from the large end of the welding groove 43, and the conical groove wall acts as a guide, allowing the laser beam to be precisely focused on the mating surface between the rivet 3 and the busbar through the welding hole 45. During the welding process, the bidirectional force system is continuously maintained. The combined structure of the welding hole 45 and the welding groove 43 does not affect pressure transmission and provides an unobstructed transmission channel for the laser beam, resulting in better performance.

[0044] Although the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A welding fixture for preventing false welds on the connecting piece of the negative electrode top cover of a circular power battery, used for welding operations between the negative electrode busbar (2) and the rivet (3), comprising a fixture base plate (1), characterized in that, Also includes: A positioning component is provided on the upper surface of the tooling base plate (1) to define the position of the negative electrode busbar (2); The elastic mechanism (5) is equidistantly arranged in the tooling base plate (1) to bear the rivets (3) and provide an upward pushing force; The pressing mechanism (4) is located above the tooling base plate (1) and is used to press down against the negative electrode busbar (2), forming a bidirectional force with the elastic mechanism (5).

2. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 1, characterized in that, The positioning component includes a positioning post (6), which is fixed to the upper surface of the tooling base plate (1), and the negative electrode busbar (2) has a positioning hole adapted to the positioning post (6).

3. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 2, characterized in that, The top of the positioning post (6) is semi-circular.

4. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 1, characterized in that, The elastic mechanism (5) includes a baffle (51), a compression spring (52) and a limiting component (53); the bottom of the tooling base plate (1) is provided with an installation groove (54), the baffle (51) is fixed in the installation groove (54), the upper surface is provided with a groove, and the compression spring (52) is placed in the groove; the limiting component (53) is located on the top of the compression spring (52) and is used to support the rivet (3).

5. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 4, characterized in that, The limiting component (53) includes an integrated movable block (531) and a limiting seat (532); the top inner wall of the mounting groove (54) is provided with a movable groove (55), and the movable block (531) is movably disposed in the movable groove (55); the upper surface of the tooling base plate (1) is provided with a movable hole communicating with the movable groove (55), the limiting seat (532) is disposed in the movable hole, and the upper surface is provided with a placement groove for placing rivets (3).

6. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 5, characterized in that, The outer wall of the movable block (531) is in close contact with the wall of the movable groove (55), and the outer wall of the limiting seat (532) is in close contact with the wall of the movable hole.

7. The welding anti-fraud fixture for the connecting piece of the negative electrode top cover of a circular power battery according to claim 6, characterized in that, The limiting component (53) is made of brass.

8. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 1, characterized in that, The pressing mechanism (4) includes a telescopic cylinder (42) and a pressing plate (41); the telescopic end of the telescopic cylinder (42) is fixedly connected to the pressing plate (41), and the bottom of the pressing plate (41) is provided with abutment pieces (44) that are evenly distributed and correspond one-to-one with the rivets (3).

9. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 8, characterized in that, The abutment piece (44) is annular and is aligned with the upper surface of the part where the negative electrode busbar (2) and the rivet (3) meet.

10. The welding fixture for preventing incomplete welding of the connecting piece of the negative electrode top cover of a circular power battery according to claim 9, characterized in that, The lower pressure plate (41) has a welding hole (45) on its lower surface, which is located at the center of the support piece (44); the upper surface of the lower pressure plate (41) has a welding groove (43) that communicates with the welding hole (45), and the cross section of the welding groove (43) is conical.

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