CN115673642A - A three-plate cross-shaped workpiece assembly welding fixture - Google Patents

Abstract

The invention discloses a three-plate cross-shaped workpiece assembly welding fixture, which comprises a fixture body, a mainboard groove is longitudinally opened on the fixture body, and the two ends of the groove top of the mainboard groove are respectively a first support part and a second support part; There are at least one pressing assembly at the bottom of the main board and at least one pressing assembly at the bottom of the main board, both of which extend into the groove of the main board; the upper side and the lateral side of the second supporting part are respectively provided with at least one rotating wing Plate pressing assembly and at least one wing plate transverse pressing assembly. The structural and functional design of two-way "⊥"-shaped two-way reference positioning and multi-degree-of-freedom measurement and adjustment ensures that the verticality, symmetry and flatness of the obtained three-plate cross-shaped workpiece meet the precision requirements required in the nuclear industry.

Description

A three-plate cross-shaped workpiece assembly welding fixture

technical field

The invention relates to the technical field of fixtures, in particular to a three-plate cross-shaped workpiece assembly welding fixture, which is used for the assembly of three-plate cross-shaped workpieces with precise thin walls and long dimensions.

Background technique

The precision thin-walled and long-sized three-plate cross-shaped workpiece is one of the commonly used structures in the fields of nuclear industry, aviation, aerospace, ordnance and ships. Especially in the nuclear industry, the cross-shaped structure is widely used by some core components of nuclear power plants. It needs to circulate in a narrow channel, and the safety, reliability, service life, technical performance and economy of nuclear power plant operation are closely related to the shape and dimension accuracy of the zirconium alloy thin-walled box. As shown in Figure 1, the three-plate cross-shaped workpiece consists of a wide plate (often called the main plate 1) and two narrow plates (often called the wing plate 2) to form a cross-shaped structure through laser welding, with a length of more than 1 meter and a wall thickness of only 5mm. Structural dimensional accuracy and geometric tolerance requirements are relatively strict. The symmetry and verticality of the four wings must be controlled within 0.2mm, and the flatness must be controlled within 0.15mm. The precision control of the external dimensions during the assembly and welding process directly affects the safe and reliable operation of the new nuclear power plant.

At present, there are few domestic and foreign research reports on tooling technology for similar parts, and the general tooling fixtures proposed by relevant research results can hardly meet the demanding manufacturing technical requirements of this part; in addition, the cross-shaped special-shaped parts themselves are not easy to design limit and positioning structures , verticality and symmetry are difficult to control. In order to simultaneously ensure the dimensional accuracy control and welding deformation control of the two vertical plates during the assembly process and improve the development efficiency, it is necessary to develop special tooling.

Contents of the invention

The purpose of the present invention is to provide a three-plate cross-shaped workpiece assembly welding fixture, which solves the problem that the assembly of three-plate cross-shaped workpieces with long dimensions and small thickness requires strict requirements on the symmetry, verticality and flatness of the four wings. The disclosed fixture device can not only obtain a three-plate cross-shaped workpiece that meets the requirements, but also realize one-time welding of two-side welds, thereby improving assembly efficiency.

The invention provides a three-plate cross-shaped workpiece assembly welding fixture, which includes a fixture body, a mainboard groove is longitudinally opened on the fixture body, and the two ends of the groove top of the mainboard groove are respectively a first support part and a second support part;

The clamp body is provided with a mainboard bottom tightening assembly and at least one mainboard pressing assembly, and the mainboard bottom pressing assembly and the mainboard pressing assembly both extend into the mainboard groove; the second support part The upper side and the lateral side are respectively provided with at least one rotary wing plate pressing assembly and at least one wing plate transverse pressing assembly.

In adopting the above technical scheme, the structure and function design of two-way "⊥"-shaped two-way reference positioning and multi-degree-of-freedom measurement and adjustment are adopted, specifically: the longitudinal position of the main board is adjusted by the pressing assembly at the bottom of the main board, and the lateral direction of the main board is adjusted by the pressing assembly of the main board The position, the rotary flap pressing assembly and the lateral pressing assembly of the flap adjust the lateral position and longitudinal position of the flap, so as to ensure that the verticality, symmetry and flatness of the obtained three-plate cross-shaped workpiece meet the requirements of the nuclear industry precision requirements.

As a possible preferred manner, a pressing plate is provided on the pressing side of the main board pressing assembly. It is used to disperse the force of the motherboard pressing component acting on the motherboard, further reducing the deformation of the motherboard during the assembly process.

As a possible preferred mode, each of the rotary wing pressing assemblies includes at least one pressing plate, at least one pressing screw and a fixing plate detachably connected to the clamp body, and the pressing screw It is threadedly connected with the fixing plate, and the pressing plate is sleeved outside the pressing screw and arranged between the fixing plate and the nail cap of the pressing screw. By screwing in and out of the fixing plate by the compression screw, the rotation of the compression plate can be realized to avoid it blocking the placement of the wing plate and to realize the pressing function of the wing plate.

As a possible preferred manner, the fixing plate is an L-shaped structure, the lateral portion of the L-shaped structure is detachably connected to the clamp body, and the pressing plate is arranged above the longitudinal portion of the L-shaped structure. The fixed plate is arranged in an L-shape to leave a certain gap between the lateral clamping assembly of the flange and the flange, which is convenient for the rotation of the lateral clamping assembly of the flange to achieve compression or the falling off of the three-plate cross-shaped workpiece after welding.

As a possible preferred manner, each of the wing plate transverse tightening components includes a transverse tightening screw with a transverse thread passing through the fixing plate, and a transverse tightening spacer is provided on the tightening side of the transverse tightening screw. The transverse clamping block is used to disperse the force acting on the end surface of the wing plate, further reducing the deformation of the end surface of the wing plate during the assembly process.

As a possible preferred manner, the bottom tightening assembly of the main board includes a bottom tightening screw of the main board, and the screw thread of the bottom tightening screw of the main board passes through the bottom of the clamp body and extends into the groove of the main board. It is used to support the bottom of the main board to avoid the deviation of the welding part caused by longitudinal movement during the welding process.

As a possible preferred manner, a bottom tightening washer is provided on the tightening side of the tightening screw at the bottom of the main board. Since the thickness of the main board is very thin, the gasket at the bottom is used to further disperse its own gravity to avoid local deformation.

As a possible preferred mode, the upper surface of the first supporting part is provided with a tight baffle, and the end of the tight baffle close to the second supporting part is provided with a rotary wing pressing plate; The flange pressing plate and the pressing baffle are connected by bolts, and the flange positioning groove is formed between the pressing baffle, the first supporting part and the second supporting part.

As a possible preferred mode, the longitudinal section of the fixture body is an isosceles triangle, the axis of the main board groove coincides with the axis of the base of the isosceles triangle, and the angle at the bottom of the isosceles triangle is 45° . Horizontal welding can be realized, and the operability is strong, thereby improving the welding quality.

As a possible preferred manner, a groove is formed on the side of the fixture, and one end of the main board pressing component protruding from the fixture body is arranged in the groove. It is convenient to achieve stable placement after being turned over, so as to realize one-time welding of two-sided welding seams and improve assembly efficiency.

As a possible preferred manner, the surface of the fixture body on which the groove is formed is provided with an overturn support seat. It can be placed stably after being turned over, which is conducive to qualified welding after turning over.

As a possible preferred manner, a turning handle is provided on the surface of the clamp body on which the groove of the main board is opened. It is convenient to turn over, and reduces the possibility of damage to the wing plate and the main board during the turnover process.

As a possible preferred manner, the bottom of the clamp body is recessed along its length to form a notch, and the main board bottom tightening assembly is arranged on a surface of the notch close to the main board groove. The main reason for setting the gap is to use general-purpose screws to tighten the bottom of the motherboard and to replace and reuse the screws in time after damage, avoiding the use of custom screws, thereby saving assembly costs.

Description of drawings

Figure 1 is a schematic diagram of a three-plate cross-shaped workpiece;

Fig. 2 is a schematic diagram of an angle of a three-plate cross-shaped workpiece assembly welding fixture;

Figure 3 is a schematic diagram of another angle of the three-plate cross-shaped workpiece assembly welding fixture;

Fig. 4 is a schematic cross-sectional view of A-A in Fig. 2 .

Among them, 1-main board; 2-wing plate; 3-fixture body; 4-main board groove; 5-first supporting part; 6-second supporting part; ;702-bottom top gasket; 8-main board compression component; 9-rotary wing plate compression component; 901-compression plate; 902-compression screw; Longitudinal part; 10-flange lateral tightening assembly; 1001-horizontal tightening screw; 1002-horizontal tightening pad; 11-pressure plate; 12-groove; 13-turning support seat; ; 16-top tight baffle; 17-screw; 18-rotary wing plate pressing plate; 19-bolt.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

It should be noted that when an element is referred to as being “fixed” or “disposed on” another element, it may be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. "Several" means one or more than one, unless otherwise clearly and specifically defined.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right" etc. are based on those shown in the accompanying drawings. Orientation or positional relationship is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connection, or integral connection; it may be mechanical connection or electrical connection; it may be direct connection or indirect connection through an intermediary, and it may be the internal communication of two elements or the interaction relationship between two elements. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

The inventors of the present invention have found that the three-plate cross-shaped workpieces used in the nuclear industry can be assembled using existing assembly welding fixtures for three-plate cross-shaped workpieces in other fields (there is a huge size difference between the length of the main board and the length of the main board is more than 1m but the wall thickness is only 5mm). ) during assembly, it is difficult to make the verticality, symmetry and flatness meet the corresponding requirements (the symmetry and verticality of the four wings need to be controlled within 0.2mm, and the flatness needs to be controlled within 0.15mm).

In order to solve the above-mentioned problems, the inventors of the present invention found that the structural and functional design of "⊥"-shaped bidirectional reference positioning and multi-degree-of-freedom measurement and adjustment can be assembled to meet the requirements of symmetry, verticality, flatness and welding deformation in the field of nuclear industry. The required three-plate cross-shaped workpiece.

Fig. 2 illustrates a schematic diagram of an angle of the three-plate cross-shaped workpiece assembly and welding fixture provided by the embodiment of the present invention; Fig. 3 illustrates another angle schematic diagram of the three-plate cross-shaped workpiece assembly and welding fixture provided by the embodiment of the present invention; Fig. 4 illustrates the diagram Schematic diagram of A-A section in 2. As shown in Figures 2-4, the three-plate cross-shaped workpiece assembly welding fixture provided by the embodiment of the present invention. This assembling welding jig comprises fixture body 3, and described fixture body 3 is longitudinally provided with main board groove 4, and the groove top two ends of described mainboard groove 4 are respectively first support part 5 and second support part 6; 3 is provided with a mainboard bottom tightening assembly 7 and a mainboard pressing assembly 8, and the mainboard bottom pressing assembly 7 and at least one mainboard pressing assembly 8 all extend into the mainboard groove 4; the second support The upper side and the lateral side of the portion 6 are respectively provided with at least one rotary flap pressing assembly 9 and at least one flap lateral pressing assembly 10 .

The main board slot 4, the first supporting part 5 and the second supporting part 6 form a "⊥" shape structure, the main board 1 is placed in the main board slot 4, and the fixing of the main board is realized by the main board bottom tightening assembly 7 and the main board pressing assembly 8. The two wing plates are placed on the first support part 5 and the second support part 6 respectively, and the two wing plates are fixed by the rotary wing plate pressing assembly 9 and the wing plate transverse pressing assembly 10 .

The upper surface of the first support part 5 is provided with a tight baffle 16, and one end of the tight baffle 16 near the second support part 6 is provided with a rotary wing pressing plate 18; The tightening plate 18 is connected to the tightening baffle 16 by bolts 19 , and a wing plate positioning slot is formed between the tightening baffle 16 , the first support portion 5 and the second support portion 6 . In an actual setting, the tightening baffle 16 can be fixed on the first supporting part 5 by screws 17 to realize the fixing of the pressing baffle 16 .

In actual operation, the main board 1 is first placed in the main board slot 4, the main board pressing assembly 8 is pre-adjusted, then the main board bottom pressing assembly 7 is adjusted so that it reaches a predetermined position, and the main board pressing assembly 8 is finally tightened to realize the main board pressing assembly. fixed. Stick one of the flaps on the predetermined positions of the first support part 5 and the second support part 6 respectively, rotate the rotary flap pressing assembly 9 above the flap and pre-adjust to limit the movement of the flap along the inclined plane , and then adjust the lateral flap pressing assembly 10 to a predetermined position, and finally fasten the rotary flap pressing assembly 9 to realize the fixing of the flap. The other wing plate is placed in the wing plate placement groove formed by the rotary wing plate pressing assembly 9, the main board 1 and the first support part 5, and then the rotating rotary wing plate pressing assembly 9 is fixed, and after the fixing is completed, the corresponding Just solder.

Because the depth of the main board groove 4 determines the welding position and the stability of the welding process to a certain extent, and then determines the welding deformation, therefore, the depth of the main board groove 4 must be greater than the height of the welding position on the main board and greater than the One-half the height of the board. As shown in Figure 4, the depth of the mainboard groove 4 is substantially close to two-thirds of the height of the mainboard, which not only facilitates the tightening operation of the top tightening assembly 7 at the bottom of the mainboard, but also facilitates the pressing assembly 8 of the mainboard. The pressing operation can reduce welding deformation as much as possible.

The width of the main board groove 4 not only needs to be greater than the thickness of the main board but also needs a certain operating space, which is convenient for the placement and removal of the main board and the pressing operation of the main board pressing assembly 8 . Generally, the width of the main board groove 4 is 2-3 times of the thickness of the main board.

As shown in FIG. 4 , the main board slot 4 , the first support portion 5 and the second support portion 6 have no special requirements on the shape of the clamp body 3 under the condition that they can form a “⊥”-shaped structure, but their It is necessary to meet the requirement that the surface where the notch of the slot 4 of the main board is located is a plane, that is, the first support portion 5 and the second support portion 6 are both planes.

Since the main board groove 4 is opened on the clamp body 3 , the material of the clamp body 3 must have a certain hardness, and no deformation will occur after the main board pressing assembly 8 is pressed.

The quantity of the rotary wing plate pressing assembly 9 and the number of the wing plate transverse pressing assembly 10 are set correspondingly according to the length of the wing plate. The distance between two adjacent rotary blade pressing assemblies 9 is set according to actual needs. The distance between two adjacent wing plate transverse tightening assemblies 10 is set according to actual needs. For example, as shown in FIGS. 2-3 , the number of the rotary blade pressing assemblies 9 is four. The number of said wing plate transverse tightening assemblies 10 is four. That is, each of the rotary flap pressing assemblies 9 is correspondingly provided with one of the flap lateral pressing assemblies 10 .

The quantity of the mainboard pressing assembly 8 is determined according to the height of the mainboard deep into the mainboard slot 4 . For example, when the height of the main board deep into the main board slot 4 is shown in Fig. 2-3, the number of the main board pressing assembly 8 is one.

In one example, as shown in FIG. 4 , a pressing plate 11 can be arranged on the pressing side of the main board pressing assembly 8, and the pressing plate 11 is arranged in the main board groove 4, and the pressing plate 11 is closely attached to the main board during use. combined, can disperse the force of the main board pressing assembly 8 acting on the main board, avoid local deformation of the main board, and affect its flatness.

There is no obvious difference between the height of the pressing plate 11 and the height of the part of the main board that penetrates into the groove 4 of the main board, and there is no obvious difference between the width of the pressing plate 11 and the length of the main board.

The material of the pressing plate 11 needs to have a certain hardness, and no deformation occurs when the main board pressing assembly 8 is pressed.

As shown in Figures 2-4, each of the above-mentioned rotary wing plate pressing assemblies 9 includes at least one pressing plate 901, at least one pressing screw 902 and a fixing plate 903 detachably connected with the clamp body 3, the pressing The tightening screw 902 is threadedly connected with the fixing plate 903 , and the pressing plate 901 is sheathed outside the pressing screw 902 and arranged between the fixing plate 903 and the nail cap of the pressing screw 902 . Rotating the compression screw 902 can realize the distance between the compression plate 901 and the wing plate, that is, realize the compression and loosening of the wing plate. The quantity of the pressing plate 901 is set according to the firmness of pressing. The quantity of the compression screws 902 is set according to the length of each compression plate 901 . As shown in FIG. 2 , each pressing plate 901 is matched with a pressing screw 902 . The length of the fixing plate 903 is set according to the distance between the two pressing plates 901 and the width of the pressing plate 901 , it is advisable to realize the fixing of the pressing plate 901 .

In a possible implementation manner, the fixing plate 903 is detachably connected to the fixture body 3 through screws.

As shown in Figures 2-4, the fixing plate 903 is an L-shaped structure, the lateral portion 9031 of the L-shaped structure is detachably connected to the clamp body 3, and the pressing plate 901 is arranged in the longitudinal direction of the L-shaped structure. Above the portion 9032, the compression screw 902 is screwed to the longitudinal portion 9032 of the L-shaped structure. Setting the L-shaped structure is beneficial to the existence of a certain gap between the longitudinal part 9032 of the L-shaped structure and the wing plate, which facilitates the installation and removal of the wing plate, and facilitates the tightening operation of the wing plate transverse tightening assembly 10 . The compression plate 901 and the longitudinal portion 9032 of the L-shaped structure are not directly connected together, but are connected by compression screws 902, so after placement or welding is completed, as long as the compression screws 902 are not connected to the compression plate 901 close contact can rotate pressing plate 901 so that it is not in the square of wing plate.

As shown in Figures 2-4, each of the wing plate transverse tightening assemblies 10 includes a transverse tightening screw 1001 with transverse threads passing through the fixing plate 903, and the tightening side of the transverse tightening screw 1001 is provided with a transverse jacking Tight spacer 1002. The lateral clamping block 1002 is used to disperse the force acting on the wing plate and reduce the deformation of the wing plate.

As shown in FIGS. 2-4 , the motherboard bottom tightening assembly 7 includes a motherboard bottom tightening screw 701 , and the motherboard bottom tightening screw 701 is threaded through the bottom of the clamp body 3 and extends into the motherboard placement groove. In order to realize the supporting effect on the bottom of the motherboard.

As shown in FIGS. 2-4 , a bottom tightening washer 702 is provided on the tightening side of the tightening screw 701 at the bottom of the motherboard. It is used to disperse the force acting on the side of the wing and reduce the deformation of the wing. The size of the bottom pressing gasket 702 is set accordingly according to the actual deformation control needs.

In one example, in order to improve the welding quality of the weld seam and the convenience of the welding operation, as shown in Figure 2-4, this embodiment sets the fixture body 3 as an isosceles triangular prism, and its transverse section is an isosceles triangle, The axis of the main board placement groove coincides with the axis of the bottom of the isosceles triangle, and the angle between the bottom of the isosceles triangle is 45°. When set to 45°, the weld is just level.

In one example, in order to achieve one-time welding of both sides of the weld, as shown in Figure 2-4, a groove 12 is opened on the side of the fixture book in this embodiment, and the main board pressing assembly 8 protrudes One end of the clamp body 3 is disposed in the groove 12 . Avoid the protrusion of the main board pressing assembly 8 from affecting the turning and fixing.

As shown in Figures 2-4, the main board pressing assembly 8 includes a main board pressing screw, the thread of which passes through the clamp main body and extends into the clamp main body. In actual application, the main board pressing screw presses against the pressing plate 11, and the pressing plate 11 is closely attached to the main board.

In one example, for the convenience of turning over, as shown in Fig. 2-4, a turning handle 14 is provided on the surface of the clamp body 3 provided with the main board slot 4, and the arrangement here may be a fixed connection or a detachable connection realized by screws.

In one example, in order not to use custom-made screws, as shown in Figure 2-4, the bottom of the fixture body 3 is recessed along its length direction to form a notch 15, and the surface of the notch 15 close to the main board slot 4 is provided with a main board bottom tightening assembly 7.

In each of the above examples, the compression ends of various screws can be provided with corresponding washers to achieve a tight fit.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. The three-plate type cross-shaped workpiece assembling and welding clamp is characterized by comprising a clamp body, wherein a main plate groove is longitudinally formed in the clamp body, and a first supporting part and a second supporting part are respectively arranged at two ends of the groove top of the main plate groove;

the clamp body is provided with a main board bottom jacking assembly and at least one main board pressing assembly, and the main board bottom jacking assembly and the main board pressing assembly both extend into the main board groove; the upper side and the transverse side of the second supporting part are respectively provided with at least one rotary wing plate pressing assembly and at least one wing plate transverse jacking assembly.

2. The three-plate cross-shaped workpiece assembling and welding fixture as claimed in claim 1, wherein a pressing plate is arranged on the pressing side of the main plate pressing assembly.

3. The three-plate cross-shaped workpiece assembling and welding fixture according to claim 1, wherein each rotary wing plate compression assembly comprises at least one compression plate, at least one compression screw and a fixing plate detachably connected with the fixture body, the compression screw is in threaded connection with the fixing plate, and the compression plate is sleeved outside the compression screw and is arranged between the fixing plate and a screw cap of the compression screw.

4. The three-plate cross-shaped workpiece assembling and welding fixture according to claim 3, wherein the fixing plate is of an L-shaped structure, a transverse part of the L-shaped structure is detachably connected with the fixture body, and the pressing plate is arranged above a longitudinal part of the L-shaped structure.

5. The three-plate cross-shaped workpiece assembling and welding clamp according to claim 3 or 4, wherein each wing plate transverse jacking component comprises a transverse jacking screw which penetrates through the fixing plate in a transverse threaded mode, and a transverse jacking cushion block is arranged on a jacking side of the transverse jacking screw.

6. The three-plate cross-shaped workpiece assembling and welding clamp according to claim 1 or 2, wherein the main plate bottom tightening component comprises a main plate bottom tightening screw, and the main plate bottom tightening screw penetrates through the bottom of the clamp body and extends into the main plate groove.

7. The three-plate type cross-shaped workpiece assembling and welding fixture according to claim 6, wherein a bottom tightening gasket is arranged on the tightening side of the tightening screw at the bottom of the main plate.

8. The three-plate cross-shaped workpiece assembling and welding clamp according to claim 1, wherein a jacking baffle is arranged on the upper surface of the first supporting part, and a rotary wing plate pressing plate is arranged at one end, close to the second supporting part, of the jacking baffle; the rotation type pterygoid lamina pressure strip with through bolted connection between the tight baffle in top, the tight baffle in top first supporting part and form the pterygoid lamina constant head tank between the second supporting part.

9. The three-plate type cross workpiece assembling and welding clamp according to claim 1, wherein the longitudinal section of the clamp body is in the shape of an isosceles triangle, the axis of the main plate groove is overlapped with the axis of the bottom side of the isosceles triangle, and the included angle of the bottom of the isosceles triangle is 45 degrees;

preferably, a groove is formed in the side face of the clamp body, and one end, protruding out of the clamp body, of the main board pressing assembly is arranged in the groove.

10. The three-plate cross-shaped workpiece assembling and welding fixture according to claim 9, wherein the face of the fixture body, on which the groove is formed, is provided with an overturning support seat; preferably, a turning handle is arranged on the surface of the clamp body, which is provided with the main plate groove;

preferably, the bottom of the clamp body is recessed along the length direction to form a notch, and the surface of the notch, which is close to the main board groove, is provided with the main board bottom jacking assembly.

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