A high pressure turbine outer ring block coating tooling and method of use thereof

Abstract

The present application belongs to a kind of coating tool and its using method, to solve the preparation coating process of spraying to single turbine outer ring block one by one, there is spraying difficulty, each turbine outer ring block spraying quality is not consistent, spraying efficiency is low, coating is adhered to tool when component is unloaded after coating spraying is finished Problem, provide a kind of high-pressure turbine outer ring block coating tool and its using method, by radial limit block, axial limit block, first boss, second boss and third boss, can be fixed to the turbine outer ring block being inverted in second boss simultaneously, using the coating tool of the application, multiple turbine outer ring blocks can be fixed simultaneously, a tool for coating spraying of small size outer shape component is proposed, the quality of turbine outer ring block coating and coating distribution uniformity can be guaranteed, effectively solve the problem that the number of turbine outer ring block is more, and the quality of coating preparation cannot be guaranteed, realize batch coating spraying of turbine outer ring block, improve the efficiency of coating preparation, reduce cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to a coating tool and its using method, and particularly relates to a high-pressure turbine outer ring block coating tool and its using method. BACKGROUND

[0002] The high-pressure turbine outer ring is one of the main structural components of the turbine stator, and its main function is to form a gas passage together with the rotor blades. With the continuous development of aero-engines, higher requirements for high-temperature resistance, long service life and light weight are put forward for the turbine outer ring component. CMC-SiC, as a new type of structural and functional integrated material with various advantages, is considered to be one of the most potential materials for developing high-temperature components of aero-engines. Studies have shown that the use of CMC-SiC in hot end components such as combustion chambers, turbines, afterburners and nozzles can increase the engine operating temperature by 300-500K, reduce the structure by 50-70%, and increase the thrust by 30-100%.

[0003] However, in the actual application of the hot end components such as the combustion chamber, the tail nozzle and the turbine of the aero-engine, the corrosive media such as high temperature, water vapor and molten salt impurities (Na, Mg, S, etc.) generated by fuel combustion will have a destructive effect on the SiO2 protective layer. Since the radial gap between the turbine outer ring and the casing will have a significant impact on the performance of the engine, an easy-to-abrade sealing structure or sealing material is generally used on the inner surface of the turbine outer ring to control the radial gap. The turbine outer ring is located at the outlet of the guide vane, and the inner surface temperature reaches 1250℃ or even higher. The outer surface is directly in contact with the gas, and faces more severe thermal oxidation and corrosion tests. At the same time, in order to improve the turbine efficiency and reduce the gap between the turbine outer ring and the rotor, a coating with high-temperature heat insulation performance and high-temperature abradable performance is generally prepared on the inner surface of the turbine outer ring. At present, the EBC coating is first prepared on the inner surface of the turbine outer ring, and then the abradable coating is prepared.

[0004] Since the overall coating preparation process of the turbine outer ring is complex and difficult to implement, the process implementation approach for preparing the coating is to spray each turbine outer ring block one by one. However, there are still the following problems: (1) The turbine outer ring block has the characteristics of small size and multiple large curvature bends, making spraying difficult; (2) The number of turbine outer ring blocks is large, and single spraying cannot guarantee the consistency of the turbine outer ring coating quality; (3) The surface temperature of the turbine outer ring block is too high during coating spraying, and the cooling time is long, which affects the spraying efficiency; (4) When the turbine outer ring block is prepared for coating, the thickness of the abradable coating is required to be between 1.0-1.5mm, which is relatively thicker than the EBC coating, causing the coating to adhere to the tool when the component is removed after coating spraying. SUMMARY

[0005] This invention addresses the technical problems of coating processes that involve spraying individual turbine outer ring blocks one by one, such as high spraying difficulty, inconsistent spraying quality among turbine outer ring blocks, low spraying efficiency, and adhesion of the coating to the tooling when the component is removed after spraying. The invention provides a high-pressure turbine outer ring block coating tooling and its usage method.

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

[0007] A high-pressure turbine outer ring block coating fixture is characterized by including a base, multiple radial limiting blocks and two axial limiting blocks;

[0008] The upper surface of the storage base is provided with two first protrusions, a groups of second protrusions, and a-1 groups of third protrusions; where a is an integer greater than or equal to 2.

[0009] Two first protrusions are respectively located on both sides of the width direction of the base; a groups of second protrusions are evenly distributed along the width direction of the base; a-1 groups of third protrusions are respectively located between two adjacent groups of second protrusions.

[0010] The second boss group includes a plurality of second bosses evenly distributed along the length of the base, each used to support the inverted turbine outer ring block; the third boss group includes a plurality of third bosses evenly distributed along the length of the base; the gap between two adjacent second bosses in a second boss group and the gap between two adjacent third bosses in a third boss group correspond one-to-one, forming a plurality of radial gaps.

[0011] Multiple radial limiting blocks are respectively installed in each radial gap, outside the outermost second boss in the length direction of the base, and two axial limiting blocks are respectively installed on the two first bosses. The inverted turbine outer ring blocks are fixed by two adjacent radial limiting blocks, axial limiting blocks and third bosses, or by two adjacent radial limiting blocks and two adjacent third bosses in the width direction of the base.

[0012] Furthermore, it also includes a base plate gasket, a rear cover plate, a cooling medium inlet, and a cooling medium outlet;

[0013] A cooling groove is provided on the lower surface of the base, corresponding to the position of the second protrusion;

[0014] The bottom plate sealing gasket is fitted and installed on the lower surface of the base to seal the cooling tank;

[0015] The rear cover is installed on the lower surface of the base and is located outside the bottom plate sealing gasket, for fixing the bottom plate sealing gasket;

[0016] The cooling medium inlet and cooling medium outlet are both located on the base and are connected to any one of the cooling tanks, which are interconnected.

[0017] Furthermore, the rear cover includes a rear cover sealing gasket and a gasket rear cover;

[0018] The rear cover sealing gasket is rectangular and is installed along the edge of the lower surface of the base.

[0019] The back cover of the pad is rectangular in shape, installed outside the back cover sealing gasket, and connected to the storage base.

[0020] Furthermore, the back cover of the pad is made of graphite material;

[0021] Both the bottom plate sealing gasket and the rear cover sealing gasket are made of polytetrafluoroethylene (PTFE).

[0022] Furthermore, a = 2;

[0023] A retaining edge is provided on the upper surface of the first boss near the second boss, which is used to cover the edge of the bottom plate of the turbine outer ring block when the turbine outer ring block is upside down on the second boss.

[0024] Furthermore, the base, radial limiting block, and axial limiting block are all made of graphite.

[0025] The present invention also provides a method for using the above-mentioned high-pressure turbine outer ring block coating tooling, which is characterized by including the following steps:

[0026] S1, install a radial limiting block on the outside of the second outermost boss at any end of the length direction of the base, and then invert the turbine outer ring block on the adjacent second boss;

[0027] S2, install radial limiting blocks in the radial gap along the length of the base towards the other end, and invert the turbine outer ring block on the second boss until the radial limiting block is installed on the outer side of the outermost second boss at the other end.

[0028] S3, axial limiting blocks are installed on the two first protrusions respectively, and the inverted turbine outer ring blocks are fixed by the two adjacent radial limiting blocks, the axial limiting blocks and the third protrusion, or the inverted turbine outer ring blocks are fixed by the two adjacent radial limiting blocks and the two adjacent third protrusions in the width direction of the base.

[0029] Furthermore, step S0, cleaning, is included before step S1;

[0030] The base, multiple radial limiting blocks, and two axial limiting blocks were placed in ethanol for ultrasonic cleaning and then dried.

[0031] Furthermore, step S0-1 is included between step S0 and step S1, in which a base sealing gasket, a rear cover sealing gasket, and a pad rear cover are sequentially installed on the lower surface of the base.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This invention proposes a coating fixture for a high-pressure turbine outer ring block. Through a radial limiting block, an axial limiting block, a first boss, a second boss, and a third boss, the turbine outer ring block, which is inverted and fastened to the second boss, can be fixed. Using this coating fixture, multiple turbine outer ring blocks can be fixed simultaneously. This invention provides a fixture for coating small-sized components, ensuring the coating quality and uniformity of the turbine outer ring block. It effectively solves the problem of inconsistent coating quality when there are many turbine outer ring blocks, enabling batch coating of turbine outer ring blocks, improving coating preparation efficiency, and reducing costs.

[0034] 2. The coating fixture of the present invention has a cooling groove designed on the lower surface of the base, which can ensure rapid cooling of the surface temperature of the turbine outer ring block during coating spraying, shortening the cooling time and improving spraying efficiency. In addition, the cooling medium in the cooling groove can be sealed by the base plate sealing gasket, the rear cover sealing gasket, and the rear cover of the pad plate, ensuring the cooling effect.

[0035] 3. In this invention, the back cover of the pad, the base, the radial limiting block and the axial limiting block are all made of graphite, which can withstand high temperatures when coating is prepared using the tooling of this invention, and avoid damage and deformation of the tooling.

[0036] 4. In this invention, a retaining edge is provided on the first protrusion, so that this invention can be applied to turbine outer ring blocks with different coating preparation requirements. If a part of the bottom plate edge does not need to be coated, it can be covered by the retaining edge.

[0037] 5. The coating fixture of the present invention can solve the problem that the outer ring block of the turbine is difficult to remove after coating preparation due to its large thickness, and can effectively prevent the coating from sticking together. Attached Figure Description

[0038] Figure 1 This is an isometric view of the turbine outer ring block;

[0039] Figure 2 This is the front view of the turbine outer ring block;

[0040] Figure 3 for Figure 2 AA section view;

[0041] Figure 4 This is a schematic diagram of an embodiment of a turbine outer ring block coating tooling according to the present invention;

[0042] Figure 5 This is a schematic diagram of the lower surface of the base in an embodiment of the present invention;

[0043] Figure 6 This is a schematic diagram illustrating the installation sequence of the bottom plate sealing gasket, the rear cover sealing gasket, and the gasket rear cover in an embodiment of the present invention.

[0044] Figure 7 This is a schematic diagram of the radial limiting block and the axial limiting block in an embodiment of the present invention;

[0045] Wherein: 1-Placement base, 2-First boss, 3-Second boss, 4-Turbine outer ring block, 5-Third boss, 6-Radial clearance, 7-Radial limiting block, 8-Axial limiting block, 9-Base plate sealing gasket, 10-Rear cover sealing gasket, 11-Pad plate rear cover, 12-Base plate surface, 13-Mounting groove surface, 14-Connecting surface. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] To address the issues of inconsistent coating quality, uneven coating distribution, complex spraying process due to the large number of turbine outer ring blocks, excessively high surface temperature during spraying, and removal problems after spraying, this invention proposes a high-pressure turbine outer ring coating preparation tooling and its usage method.

[0048] like Figures 1 to 3 As shown, the turbine outer ring block includes a base plate surface 12, a mounting groove surface 13, and a connecting surface 14, wherein the base plate surface 12 is the surface to be coated. In some processing requirements, the entire base plate surface 12 needs to be coated; in other processing requirements, only a portion of the base plate surface 12 needs to be coated, such as... Figure 3 In this case, coating preparation is only required within the area covered by A; no coating preparation is required near the edge of the mounting groove 13.

[0049] A high-pressure turbine outer ring coating preparation fixture is a layered assembly fixture capable of preparing coatings for large-radius surfaces. It includes a base plate 4, a base plate sealing gasket 5, a back cover 6, a back cover sealing gasket 7, an axial limiting block 8, and a radial limiting block 9. Whether the base plate 4 has a radius of curvature, and the size of that radius, can be adapted to the radius of curvature of the workpiece to be coated.

[0050] The upper surface of the base plate 1 is provided with two first protrusions 2, a groups of second protrusions, and a-1 groups of third protrusions, where a is an integer greater than or equal to 2. The two first protrusions 2 are respectively located on both sides of the width direction of the base plate 1. The a groups of second protrusions are evenly distributed along the width direction of the base plate 1, and the a-1 groups of third protrusions are located between adjacent groups of second protrusions. Each group of second protrusions includes multiple second protrusions 3 evenly distributed along the length direction of the base plate 1, used to support each inverted turbine outer ring block 4. Each group of third protrusions includes multiple third protrusions 5 evenly distributed along the length direction of the base plate 1. The gap between two adjacent second protrusions 3 in a group of second protrusions and the gap between two adjacent third protrusions 5 in a group of third protrusions correspond one-to-one, forming multiple radial gaps 6. The first protrusions 2 are matched with the axial limiting block 8, the second protrusions 3 are adapted to the dimensions of the mounting groove surface 13 of the turbine outer ring block 4, and the third protrusions 5 are matched with the radial limiting block 7. Figure 5 A cooling groove 15 is provided on the lower surface of the base 1, corresponding to the position of the second protrusion 3, for cooling the outer ring block 4 of the turbine through gas or liquid cooling mechanisms. A base plate sealing gasket 9 is fitted onto the lower surface of the base 1 to seal the cooling groove 15. The rear cover plate includes a rear cover sealing gasket 10 and a pad rear cover 11. The rear cover sealing gasket 10 is rectangular and installed along the edge of the lower surface of the base 1. The pad rear cover 11 is rectangular and installed outside the rear cover sealing gasket 10, connected to the base 1. Both the cooling medium inlet and outlet are located on the base 1 and are connected to any one of the cooling grooves 15, with each cooling groove 15 interconnected. If the base 1 is arc-shaped, the base plate sealing gasket 9 is a rotary semi-circular structure, mainly used to seal between each cooling groove 15 and the pad rear cover 11 of the base 1, preventing leakage of the cooling medium and improving the sealing effect within the cooling groove 15. The rear cover sealing gasket 10 is placed on the back of the storage base 1. It has a rectangular edge with a hollow center and connection holes along the edge. The pad cover 11 covers the back of the storage base 1. It is the same size as the storage base 1 and also has connection holes along its edge. The axial limiting block 8 and the radial limiting block 7 are used to fix the turbine outer ring block 4 and are connected and fixed to the storage base 1 by bolts.

[0051] exist Figure 4 In the embodiment shown, a = 2. A retaining edge is provided on the side of the upper end face of the first boss 2 near the second boss 3, which is used to block the edge of the bottom plate surface 12 of the turbine outer ring block 4 when the turbine outer ring block 4 is upside down on the second boss 3, so that a part of the edge of the bottom plate surface 12 of the turbine outer ring block 4 is blocked.

[0052] In one embodiment of the present invention, the base 1, the back cover 11, the axial limiting block 8, and the radial limiting block 7 are all made of high-temperature resistant materials, such as high-purity fine graphite or electrode graphite, to fit the ceramic-based turbine outer ring block 4 and prevent mismatch and damage caused by the large difference in their thermal expansion coefficients. The base plate sealing gasket 9 and the back cover sealing gasket 10 are both made of corrosion-resistant and anti-aging materials, generally polytetrafluoroethylene gaskets.

[0053] The turbine outer ring block 4 is generally made of ceramic matrix composite material. The main body of the turbine outer ring block can be prepared by 2D or 2.5D composite fiber preform method. Its structural features include complex curved surface shape, densely packed blind holes or through hole array.

[0054] When preparing a coating using the coating tooling of the present invention, the coating preparation process can be thermal spraying, plasma spraying, electron beam physical vapor deposition spraying, or a combination of both processes.

[0055] The present invention also provides a method for using the above-mentioned turbine outer ring coating tooling, comprising the following steps:

[0056] Step 1, Tooling cleaning and drying:

[0057] The designed coating fixture was placed in a container filled with 75% ethanol and ultrasonically cleaned for 15 minutes. After cleaning, it was placed in an oven and dried completely at 80°C.

[0058] like Figure 6 Install the base plate sealing gasket 9, the rear cover sealing gasket 10, and the pad plate rear cover 11 sequentially on the lower surface of the base 1:

[0059] Step 2, Installation of base plate sealing gasket 9:

[0060] Place the bottom plate sealing gasket 9 outside the cooling cavity formed by the cooling groove 15 on the back of the base 1, according to the shape of the cooling groove 15 on the lower surface of the base 1. When placing it, ensure that the bottom plate sealing gasket 9 is flat and that there are no wrinkles or accumulations.

[0061] Step 3, Installation of the rear cover sealing gasket 10:

[0062] Place the back cover sealing gasket 10 according to the outline of the lower surface of the storage base 1. When placing it, make sure that the connecting hole on the back cover sealing gasket 10 is aligned with the connecting hole at the edge of the lower surface of the storage base 1. No wrinkles or accumulation are allowed.

[0063] Step 4, Installation of the back cover 11 of the pad:

[0064] After installing the base plate sealing gasket 9 and the rear cover sealing gasket 10, place the pad rear cover 11 on the rear cover sealing gasket 10. During placement, ensure that the connecting holes of the pad rear cover 11 are aligned with the connecting holes of the rear cover sealing gasket 10 and the storage base 1.

[0065] Step 5: Install the ceramic-based turbine outer ring block 4;

[0066] Place a radial limiting block 7 on one side of the outermost second protrusion 3 on the upper surface of the base 1 along its length, ensuring that the radial limiting block 7 is aligned with the corresponding connection hole on the upper surface of the base 1. Then, place the mounting groove surfaces 13 of the two turbine outer ring blocks 4 to be sprayed into the upper and lower second protrusions 3 on the right side of the radial limiting block. The sides of the turbine outer ring blocks 4 can be covered with graphite paper to ensure that the second protrusions 3 are aligned with the mounting groove surfaces 13 of the turbine outer ring blocks 4. Place the remaining turbine outer ring blocks 4 in the same order as above, from one end of the base 1 along its length to the other end, sequentially placing the radial limiting block 7 and the turbine outer ring blocks 4 until the last set of turbine outer ring blocks 4 is placed. Then, place the radial limiting block 7 on the right side of the last set of turbine outer ring blocks for fixation.

[0067] Step 6, Installation of the axial limiting block:

[0068] After the turbine outer ring block 4 is installed, place the two axial limiting blocks 8 of the upper and lower parts on the two first protrusions 2 on the upper surface of the base 1 respectively, and ensure that the axial limiting blocks 8 are aligned with the corresponding connecting holes on the base 1.

[0069] Step 7: Assembly of the tooling for the preparation of the turbine outer ring block 4:

[0070] Assemble the base 1, back cover 11, back cover sealing gasket 10, axial limiting block 8, and radial limiting block 7 using bolts to ensure that there is no looseness between the parts of the coating fixture and between the parts and the turbine outer ring block 4 after the connection is completed. In addition, it is necessary to ensure that the upper and lower end faces and inner surface interfaces of adjacent parts are flush, without obvious steps or gaps. Shaking around the turbine outer ring block 4 without any displacement is used as a criterion for judging whether the installation is successful.

[0071] Currently, the spraying process involves spraying individual turbine outer ring blocks 4. However, this method suffers from several drawbacks: the turbine outer ring blocks 4 have small dimensions and numerous large-curvature bends; the large number of turbine outer ring blocks in a single batch makes it difficult to guarantee the coating quality of each block; and the coating distribution is uneven. Furthermore, the wear-resistant coating thickness requirement of 1.0–1.5 mm, compared to the EBC coating, is relatively thick, leading to coating adhesion during removal after spraying. Therefore, this invention proposes a method to effectively solve the problem of inconsistent coating quality due to the large number of turbine outer ring blocks 4. This method enables batch spraying of the turbine outer ring blocks 4 coating. The cooling grooves designed on the back of the base 1 ensure rapid cooling of the turbine outer ring block 4 surface temperature during spraying, reducing cooling time and improving spraying efficiency. Additionally, it addresses the issue of the thick wear-resistant coating making removal difficult and causing coating adhesion.

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-pressure turbine outer ring block coating tooling, characterized in that: It includes a storage base (1), multiple radial limiting blocks (7) and two axial limiting blocks (8); The upper surface of the storage base (1) is provided with two first protrusions (2), a groups of second protrusions and a-1 groups of third protrusions; where a is an integer greater than or equal to 2; Two first protrusions (2) are respectively set on both sides of the width direction of the storage base (1); a groups of second protrusions are evenly distributed along the width direction of the storage base (1); a-1 groups of third protrusions are respectively located between two adjacent groups of second protrusions; The second boss group includes a plurality of second bosses (3) evenly distributed along the length of the base (1), which are used to support each inverted turbine outer ring block (4); the third boss group includes a plurality of third bosses (5) evenly distributed along the length of the base (1); the gap between two adjacent second bosses (3) in a second boss group and the gap between two adjacent third bosses (5) in a third boss group correspond one-to-one, forming a plurality of radial gaps (6). Multiple radial limiting blocks (7) are respectively installed in each radial gap (6) and outside the outermost second boss (3) in the length direction of the storage base (1). Two axial limiting blocks (8) are respectively installed on two first bosses (2). Each inverted turbine outer ring block (4) is fixed by two adjacent radial limiting blocks (7), axial limiting blocks (8) and third bosses (5), or by two adjacent radial limiting blocks (7) and two adjacent third bosses (5) in the width direction of the storage base (1).

2. The high-pressure turbine outer ring block coating tooling according to claim 1, characterized in that: It also includes a base plate gasket (9), a rear cover plate, a cooling medium inlet, and a cooling medium outlet; A cooling groove (15) is provided on the lower surface of the storage base (1) at the position corresponding to the second boss (3). The bottom plate sealing gasket (9) is fitted onto the lower surface of the base (1) to seal the cooling groove (15). The rear cover is installed on the lower surface of the storage base (1), located outside the bottom plate sealing gasket (9), and is used to fix the bottom plate sealing gasket (9). The cooling medium inlet and cooling medium outlet are both located on the base (1) and are connected to any cooling tank (15), and the cooling tanks (15) are interconnected.

3. The high-pressure turbine outer ring block coating tooling according to claim 2, characterized in that: The rear cover includes a rear cover sealing gasket (10) and a gasket rear cover (11). The rear cover sealing gasket (10) is rectangular and is installed along the lower surface edge of the base (1); The back cover (11) of the pad is rectangular and is installed outside the back cover sealing gasket (10) and connected to the storage base (1).

4. The high-pressure turbine outer ring block coating tooling according to claim 3, characterized in that: The back cover (11) of the pad is made of graphite. Both the bottom plate sealing gasket (9) and the rear cover sealing gasket (10) are made of polytetrafluoroethylene gaskets.

5. A high-pressure turbine outer ring block coating fixture according to any one of claims 1 to 4, characterized in that: a=2； A retaining edge is provided on the side of the upper end face of the first boss (2) near the second boss (3) to cover the edge of the bottom plate surface (12) of the turbine outer ring block (4) when the turbine outer ring block (4) is upside down on the second boss (3).

6. The high-pressure turbine outer ring block coating fixture according to claim 5, characterized in that: The base (1), radial limiting block (7) and axial limiting block (8) are all made of graphite.

7. A method of using the high-pressure turbine outer ring block coating tooling according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1, install a radial limiting block (7) on the outside of the second outermost boss (3) at any end of the length direction of the storage base (1), and then fasten the turbine outer ring block (4) on the adjacent second boss (3). S2, install radial limiting blocks (7) in the radial gap (6) along the length direction of the base (1) to the other end, and invert the turbine outer ring block (4) on the second boss (3) until the radial limiting block (7) is installed on the outer side of the outermost second boss (3) at the other end. S3, install axial limiting blocks (8) on the two first bosses (2) respectively, and fix each inverted turbine outer ring block (4) by two adjacent radial limiting blocks (7), axial limiting blocks (8) and third bosses (5), or fix each inverted turbine outer ring block (4) by two adjacent radial limiting blocks (7) and two adjacent third bosses (5) in the width direction of the storage base (1).

8. The method of using the high-pressure turbine outer ring block coating tooling according to claim 7, characterized in that: Step S0, cleaning, is included before step S1; Place the base (1), multiple radial limiting blocks (7) and two axial limiting blocks (8) into ethanol for ultrasonic cleaning and drying.

9. The method of using the high-pressure turbine outer ring block coating tooling according to claim 8, characterized in that: The step between step S0 and step S1 also includes step S0-1, in which the bottom plate sealing gasket (9), the rear cover sealing gasket (10) and the pad plate rear cover (11) are installed sequentially on the lower surface of the storage base (1).

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