Large torque marine propulsion variable frequency motor

Abstract

The application discloses a large-torque marine propulsion variable-frequency motor and relates to the field of motor application. A base shell comprises an inner shell and an outer shell, a cooling channel is arranged between the inner shell and the outer shell, the cooling channel comprises multiple groups of annular cooling channels, the multiple groups of annular cooling channels are connected in series through a connecting assembly, the connecting assembly comprises a first branch pipe, the first branch pipe is used for connecting two adjacent groups of annular cooling channels in series, a chip removal pipe is arranged at the bottom of the first branch pipe, and a first plug is arranged at the bottom of the chip removal pipe. The cooling channel is composed of multiple groups of vertically distributed annular cooling channels arranged along the axial direction, the multiple groups of annular cooling channels are connected in series through the connecting assembly arranged at the bottom of the shell, the connecting assembly is provided with the chip removal pipe, in the horizontal motor, the impurities in the annular cooling channel vertically distributed on the ground are more likely to deposit at the bottom, then the impurities are concentrated in one place through the structure of the annular cooling channel, the chip removal pipe is opened for point cleaning, and the cooling channel can be better flushed.

Description

Technical Field

[0001] This invention relates to the field of electric motor applications, specifically to a high-torque marine propulsion variable frequency motor. Background Technology

[0002] High-torque marine propulsion motors are a type of special motor designed specifically for the main propulsion of ships, capable of continuously outputting extremely high torque at low speeds (typically ≤500 rpm). The mainstream type is permanent magnet synchronous, but some high-performance asynchronous motors are also included.

[0003] The motor mainly consists of a housing, front and rear end covers, stator, rotor, and cooling system. High-torque marine propulsion motors are large in size, have high current, high losses and heat generation, and poor heat dissipation in the sealed ship cabin. The cooling system is an integral part of the motor body. The cooling system usually includes cooling channels distributed inside the housing and a cooling medium circulation system. Common cooling channels include spiral winding type and axial folding type. The spiral winding type is formed by machining spiral grooves / welding spiral guide ribs between the inner and outer cylinders, and then fully welding and sealing the inner and outer cylinders around the circumference, thus forming a spiral winding cooling channel inside the housing (the unwelded areas inside rely on metal interference fit, which can prevent liquid leakage under the conventional cooling water pressure of 0.3-0.8Mpa, allowing the cooling water to circulate along the cooling channel). The axial folding type is formed by machining multiple sets of guide grooves on the end face of the housing, and then staggering and welding the outlets of the guide grooves on the end face of the housing to form a folding type cooling channel distributed in a circle along the outer circumference.

[0004] The coolant used in the cooling system is usually about 40% ethylene glycol + deionized water, with a flow rate of 1.2-2.5 m / s. The normal inlet water temperature is 30-40℃ and the normal outlet water temperature is 45-55℃. When a high-torque marine motor experiences local overload, the local hot spot of the motor can reach 110-135℃. The boiling point of the ethylene glycol aqueous solution at normal pressure is 108℃, which directly causes the coolant to vaporize and foam locally. The boiling of the coolant not only deteriorates the heat exchange, but also increases scaling and causes electrochemical corrosion. Rust and scale are produced and block the flow channels. Over time, this will eventually reduce the cooling efficiency. Therefore, in practical applications, the cooling channels of the motor will be maintained and flushed. Taking a horizontally mounted motor as an example, when the motor stops working, the coolant flow rate decreases or impurities are easily deposited when it is stationary. Conventional marine base hull cooling channels are all single-circuit single-inlet single-outlet structures, and very few use native multi-circuit parallel connection. This results in the cooling channel being difficult to flush out with the water flow due to the long overall travel of the cooling channel during high-pressure flushing.

[0005] In a spiral-wound type cold channel, multiple sets of annular single slots are mainly arranged along the axial direction. Therefore, in an annular single slot cold channel, impurities will be mostly distributed at the bottom of the motor housing due to gravity. In an axially folded-back type cold channel, multiple sets of straight slots parallel to the axis surround the housing. Therefore, impurities will be distributed in each set of straight slots. In other words, in a spiral-wound type cold channel, impurities usually accumulate in the cold channel at the bottom of the housing, while in an axially folded-back type cold channel, impurities usually accumulate in the entire cold channel. Within the same time limit, the blockage at the bottom of the spiral-wound type cold channel will be more severe. Summary of the Invention

[0006] Based on this, the purpose of this invention is to provide a high-torque marine propulsion variable frequency motor to solve the technical problem that impurities are difficult to flush out due to the long cold run.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a high-torque marine propulsion variable frequency motor, comprising a base housing and a stator, rotor, and drive shaft disposed therein. The base housing includes an inner housing and an outer housing, with a cooling channel provided between the inner housing and the outer housing. The cooling channel includes multiple sets of annular cooling channels, which are connected in series by a connecting assembly. The connecting assembly includes a first branch pipe for connecting two adjacent sets of annular cooling channels in series. A chip removal pipe is provided at the bottom of the first branch pipe, and a first plug is provided at the bottom of the chip removal pipe. One end of the cooling channel is provided with... It has a first water inlet and a first water outlet at the other end. The first water inlet and the first water outlet are connected to a cooling system. The annular cooling channel is composed of a first annular groove opened on the outer wall of the inner shell and a second annular groove opened on the inner wall of the outer shell. Multiple sets of through holes are opened on the top of the outer shell. The multiple sets of through holes extend into the multiple sets of annular cooling channels. The multiple sets of through holes are connected to a flushing assembly. The flushing assembly includes a main pipe. Multiple sets of branch pipes are provided at the bottom of the main pipe. A sealing ball is movably installed inside the branch pipe. The sealing ball and the inner wall of the main pipe are connected by a spring. The branch pipe is connected to the through hole by a second branch pipe.

[0008] By adopting the above technical solution, the cooling channel is composed of multiple sets of vertically distributed annular cooling channels arranged along the axial direction. The multiple sets of annular cooling channels are connected in series by a connecting component at the bottom of the housing. The connecting component is equipped with a chip removal pipe. In the horizontal motor, the annular cooling channels distributed vertically to the ground are more likely to accumulate impurities at the bottom. The structure of the annular cooling channels concentrates the impurities in one place. Then, the chip removal pipe is opened for targeted cleaning, which can better flush the cooling channel.

[0009] The invention is further configured such that the bottom of the inner housing is provided with a first mounting groove for accommodating multiple sets of connecting components, and the two ends of the inner housing are provided with fixing feet for mounting end caps, the top of the inner housing is provided with a control box, and the side of the control box is provided with a protective cover.

[0010] Preferably, a first mounting slot is provided to provide installation space for multiple sets of connecting components.

[0011] The present invention is further configured such that the outer shell and the inner shell are sealed and fixed by welding process, the outer shell is provided with multiple sets of heat dissipation fins, and the bottom of the outer shell is provided with connecting feet.

[0012] Preferably, heat dissipation fins can be provided to improve the heat dissipation effect of the base housing, and connecting feet are provided for fixing the motor inside the cabin.

[0013] The present invention is further configured such that multiple sets of the annular cooling channels are vertically distributed and the multiple sets of annular cooling channels are uniformly arranged along the axial direction of the base shell.

[0014] Preferably, by setting up vertically distributed annular cooling channels, impurities in the coolant within the annular cooling channels can be concentrated at the bottom by gravity, which facilitates subsequent cleaning.

[0015] The invention is further configured such that a second plug is provided at the top of the main pipe, the second plug being used to connect water for flushing.

[0016] Preferably, a second plug is provided to both seal the rinsing assembly and allow it to be opened to connect high-pressure distilled water to the rinsing assembly.

[0017] The invention is further configured such that the cooling channel can also be an annular folding groove formed on the outer wall of the inner shell and the inner wall of the outer shell, the bottom of the outer shell is provided with multiple sets of clips, and the bottom of the outer shell is provided with a second mounting groove, the bottom of the second mounting groove being installed with a bottom shell.

[0018] Preferably, by setting an annular folding groove to cooperate with the installation of the bottom shell to form a cooling channel, the disassembly of the bottom shell will be more convenient.

[0019] The invention is further configured such that the bottom shell includes a sealing plate, the top of the sealing plate has multiple sets of semi-arc grooves, the multiple sets of semi-arc grooves and the annular folding grooves are matched and are part of the cooling channel, and the top of the sealing plate is provided with a second water inlet and a second water outlet, the second water inlet and the second water outlet are connected to the cooling system.

[0020] Preferably, by setting the bottom shell and the annular folding groove to form a cooling channel, the disassembly efficiency can be improved, the dead corners of the bottom shell are reduced, and the rinsing efficiency is high.

[0021] The invention is further configured such that the top of the sealing plate is provided with a fitting groove at the location of multiple sets of semi-circular grooves, the second inlet and the second outlet, and the fitting groove matches the slip.

[0022] Preferably, by setting the fitting groove and the slip assembly, a special-shaped sealing gasket and sealing sheet can also be set on the top of the bottom shell to improve the sealing performance of the bottom shell.

[0023] In summary, the present invention has the following main beneficial effects: The cooling channel in this invention is composed of multiple sets of vertically distributed annular cooling channels arranged along the axial direction. The multiple sets of annular cooling channels are connected in series by a connecting component at the bottom of the housing. The connecting component is equipped with a chip removal pipe. In a horizontally mounted motor, the annular cooling channels that are vertically distributed to the ground are more likely to accumulate impurities at the bottom. The structure of the annular cooling channels concentrates the impurities in one place. Then, the chip removal pipe is opened for targeted cleaning, which can better flush the cooling channel.

[0024] This invention enables more efficient flushing of cooling channels by setting up a flushing assembly. The flushing assembly is distributed at the top of the housing, with two or more annular cooling channels forming a whole. A branch pipe is connected to the flushing assembly, and a unidirectionally moving sealing ball is installed inside the branch pipe. When the flushing assembly is not working, the sealing ball blocks the flow of coolant, ensuring normal flow and preventing it from entering the flushing assembly. When the flushing assembly is working, the main pipe of the flushing assembly is connected to high-pressure water, which flows into each annular cooling channel. At this time, the chip removal pipe is opened, allowing each annular cooling channel to be flushed individually. Compared with the traditional flushing scheme of flushing a single-loop cooling channel as a whole, the flushing is more thorough.

[0025] This invention, by setting up an integrally disassembled bottom shell, makes the cold channel flushing work more convenient and faster. Multiple sets of annular cold channels connected in series will use multiple sets of connecting components. During the flushing work, it takes a certain amount of time to open the chip discharge pipes of multiple sets of connecting components. However, the overall sealing bottom shell is easier to disassemble. Moreover, the bottom shell sealing is simpler in structure than the connecting components, with fewer dead corners, and it is also easier to flush the impurities attached to the surface of the bottom shell. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention; Figure 2 This is an exploded view of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram showing the distribution of the inner shell, outer shell, connecting components, and flushing components according to Embodiment 1 of the present invention; Figure 4 This is a schematic diagram showing the distribution of the inner shell, the first annular groove, and the first mounting groove in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram showing the distribution of the outer shell, the second annular groove, and the through holes in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the cooling channel structure according to Embodiment 1 of the present invention; Figure 7This is a schematic diagram of the connection component structure according to Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the internal structure of the rinsing assembly according to Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the flushing assembly and annular cooling channel distribution according to Embodiment 1 of the present invention; Figure 10 This is a schematic diagram of the overall structure of Embodiment 2 of the present invention; Figure 11 This is a schematic diagram showing the distribution of the inner shell and the annular folding groove in Embodiment 2 of the present invention; Figure 12 This is a schematic diagram showing the distribution of the outer shell, the latch, and the second mounting groove in Embodiment 2 of the present invention; Figure 13 This is a schematic diagram showing the distribution of the inner shell, outer shell, and annular folding groove in Embodiment 2 of the present invention; Figure 14 This is a schematic diagram of the bottom shell structure of Embodiment 2 of the present invention. Explanation of reference numerals in the attached figures: 1. Inner shell; 2. First mounting groove; 3. First annular groove; 4. Fixing foot; 5. Outer shell; 6. Second annular groove; 7. Through hole; 8. Heat dissipation fins; 9. Annular cooling channel; 10. Connecting assembly; 1001. First branch pipe; 1002. Chip removal pipe; 1003. First plug; 11. First water inlet; 12. First water outlet; 13. Flushing assembly; 1301. Main pipe; 1302. Second plug; 130 3. Branch pipe; 1304. Sealing ball; 1305. Spring; 1306. Second branch pipe; 14. Drive shaft; 15. End cap; 16. Protective cover; 17. Control box; 18. Connecting foot; 19. Annular folding groove; 20. Slipper; 21. Second mounting groove; 22. Bottom shell; 2201. Sealing plate; 2202. Semi-arc groove; 2203. Second inlet; 2204. Second outlet; 2205. Fitting groove. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0028] The embodiments of the present invention will now be described.

[0029] Example 1: Please refer to Figures 1-9A high-torque marine propulsion variable frequency motor includes a base housing and a stator, rotor, and drive shaft 14 disposed inside it. The base housing includes an inner housing 1 and an outer housing 5. A cooling channel is provided between the inner housing 1 and the outer housing 5. A cooling medium of ethylene glycol + deionized water flows in the cooling channel. The cooling channel includes multiple sets of annular cooling channels 9, which are connected in series by a connecting assembly 10. The connecting assembly 10 includes a first branch pipe 1001, which is used to connect two adjacent sets of annular cooling channels 9 in series. A chip removal pipe 1002 is provided at the bottom of the first branch pipe 1001, and a first plug 1003 is provided at the bottom of the chip removal pipe 1002. A first water inlet 11 is provided at one end of the cooling channel, and a first water outlet 12 is provided at the other end. The first water inlet 11 and the first water outlet 12 are connected together. A cooling system is connected to the outer casing 1. The cooling system is used to cool and transport the cooling medium. The annular cooling channel 9 is composed of a first annular groove 3 opened on the outer wall of the inner casing 1 and a second annular groove 6 opened on the inner wall of the outer casing 5. The first annular groove 3 and the second annular groove 6 can be assembled by turning and sheet welding. The top of the outer casing 5 has multiple sets of through holes 7, which extend into the multiple sets of annular cooling channels 9. The multiple sets of through holes 7 are connected to a flushing assembly 13. The flushing assembly 13 includes a main pipe 1301. The bottom of the main pipe 1301 is provided with multiple sets of branch pipes 1303. A sealing ball 1304 is movably installed inside the branch pipe 1303. The sealing ball 1304 and the inner wall of the main pipe 1301 are connected by a spring 1305. The branch pipe 1303 is connected to the through holes 7 by a second branch pipe 1306.

[0030] Please refer to the above embodiments for further details. Figure 4 The bottom of the inner housing 1 is provided with a first mounting groove 2 for accommodating multiple sets of connecting components 10, and the two ends of the inner housing 1 are provided with fixing feet 4 for mounting end caps 15. The top of the inner housing 1 is provided with a control box 17, and the side of the control box 17 is provided with a protective cover 16. The first mounting groove 2 provides installation space for the multiple sets of connecting components 10.

[0031] Please refer to the above embodiments for further details. Figure 5 The outer shell 5 and the inner shell 1 are sealed and fixed by welding. The outer shell 5 is provided with multiple sets of heat dissipation fins 8, and the bottom of the outer shell 5 is provided with connecting feet 18. The heat dissipation effect of the base shell can be improved by setting heat dissipation fins 8, and the connecting feet 18 are used to fix the motor in the cabin.

[0032] Please refer to the above embodiments for further details. Figure 6 Multiple sets of annular cooling channels 9 are vertically distributed and evenly arranged along the axial direction of the base shell. By setting up vertically distributed annular cooling channels 9, when impurities appear in the annular cooling channels 9, they can be concentrated at the bottom by gravity and deposited, which facilitates subsequent cleaning.

[0033] Please refer to the above embodiments for further details. Figure 8 The top of the main pipe 1301 is provided with a second plug 1302. The second plug 1302 is used to connect the rinsing water. By setting the second plug 1302, it can be used to seal the rinsing assembly 13, or it can be opened to connect the rinsing assembly 13 with high-pressure distilled water.

[0034] Example 2: Please refer to Figures 10-14 The cooling channel can also be an annular folding groove 19 opened on the outer wall of the inner shell 1 and the inner wall of the outer shell 5. The bottom of the outer shell 5 is provided with multiple sets of clips 20, and the bottom of the outer shell 5 is provided with a second mounting groove 21. The bottom of the second mounting groove 21 is installed with a bottom shell 22. By setting the annular folding groove 19 and installing the bottom shell 22, a cooling channel is formed, and the bottom shell 22 is more convenient to disassemble.

[0035] Please refer to the above embodiments for further details. Figure 14 The bottom shell 22 includes a sealing plate 2201. The top of the sealing plate 2201 has multiple sets of semi-arc grooves 2202, which match the annular folding groove 19 and are part of the cooling channel. The top of the sealing plate 2201 is provided with a second water inlet 2203 and a second water outlet 2204. The second water inlet 2203 and the second water outlet 2204 are connected to the cooling system. By setting the bottom shell 22 and the annular folding groove 19 to form a cooling channel, the disassembly efficiency can be improved, and the sealing plate 2201 has fewer dead corners and higher flushing efficiency.

[0036] Please refer to the above embodiments for further details. Figures 12-14 The top of the sealing plate 2201 is provided with a fitting groove 2205 at the location of multiple semi-arc grooves 2202, the second inlet 2203 and the second outlet 2204. The fitting groove 2205 matches the slip 20. By setting the fitting groove 2205 and the slip 20 for assembly, a special-shaped sealing gasket and sealing sheet can also be set on the top of the bottom shell 22 to improve the sealing performance of the bottom shell 22.

[0037] In specific operation, taking Embodiment 1 as an example: when the motor in this application is working normally, the cooling system works, delivering coolant to the first inlet 11, and then the coolant flows in the cooling channel and is discharged from the first outlet 12 back into the cooling system, thus cycling to remove the heat from the base housing. When the cooling channel needs to be flushed, it should be done when the motor is stopped. Sufficient installation and maintenance space should be reserved at the bottom of the motor. The staff first opens the first cover 1003 of the multiple sets of connecting components 10 and flushes them together. Then, the second cover 1302 is opened and high-pressure water (which can be high-pressure distilled water) is connected. The high-pressure distilled water enters the main pipe 1301 and pushes the sealing ball 1304 downward, causing the spring 1305 to be further stretched. Then, the high-pressure distilled water enters the corresponding second branch pipe 1306 through the multiple sets of branch pipes 1303 and enters the annular cooling channel 9 through the through hole 7 at the top of the outer casing 5. Two or more sets of annular cooling channels 9 are connected as a whole to the sealing ball 1304 through the second branch pipe 1306. At this time, since the multiple sets of first cover 1003 are in the open state, the high-pressure distilled water is diverted to flush each set of annular cooling channels 9 simultaneously and individually. The waste liquid after flushing will also be discharged from the chip discharge pipe 1002. After cleaning, the system can be restored.

[0038] Taking Example 2 as an example, when the cooling channel needs to be flushed, it is also done when the motor is stopped. The staff disassembles the bottom shell 22 at the bottom of the base housing, and then uses high-pressure distilled water to flush the dead corners of the bottom shell 22 surface, such as the semi-arc groove 2202, the second water inlet 2203, the second water outlet 2204, and the fitting groove 2205. Then, the second plug 1302 is opened and high-pressure distilled water is connected. The high-pressure distilled water enters the main pipe 1301 and pushes the sealing ball 1304 down, causing the spring 1305 to be further stretched. Then, the high-pressure distilled water enters the corresponding second branch pipe 1306 through multiple branch pipes 1303, and then enters the annular cooling channel 9 through the through hole 7 at the top of the outer shell 5. Two or more annular cooling channels 9 are connected as a whole through the second branch pipe 1306 to the sealing ball 1304. Then, the high-pressure distilled water is diverted to flush each annular cooling channel 9 synchronously and individually. The waste liquid after flushing will also be discharged from the end of the annular return groove 19. After cleaning, it can be restored.

[0039] Although embodiments of the present invention have been shown and described, these specific embodiments are merely explanations of the invention and are not intended to limit it. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions, and variations to the embodiments as needed without departing from the principles and spirit of the invention, but such modifications, substitutions, and variations are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A high-torque marine propulsion variable frequency motor, comprising a base housing and a stator, rotor, and drive shaft (14) disposed therein, characterized in that: The base housing includes an inner housing (1) and an outer housing (5). A cooling channel is provided between the inner housing (1) and the outer housing (5). The cooling channel includes multiple sets of annular cooling channels (9), and the multiple sets of annular cooling channels (9) are connected in series by a connecting component (10). The connecting component (10) includes a first branch pipe (1001), which is used to connect two adjacent sets of annular cooling channels (9) in series. A chip removal pipe (1002) is provided at the bottom of the first branch pipe (1001), and a first plug (1003) is provided at the bottom of the chip removal pipe (1002). A first water inlet (11) is provided at one end of the cooling channel, and a first water outlet (12) is provided at the other end. The first water inlet (11) and the first water outlet (12) are connected to a cooling system. The annular cooling channel (9) is composed of a first annular groove (3) opened on the outer wall of the inner shell (1) and a second annular groove (6) opened on the inner wall of the outer shell (5). Multiple sets of through holes (7) are opened on the top of the outer shell (5). The multiple sets of through holes (7) extend into the multiple sets of annular cooling channels (9). The multiple sets of through holes (7) are connected to a flushing assembly (13). The flushing assembly (13) includes a main pipe (1301). Multiple sets of branch pipes (1303) are provided at the bottom of the main pipe (1301). A sealing ball (1304) is movably installed inside the branch pipe (1303). The sealing ball (1304) and the inner wall of the main pipe (1301) are connected by a spring (1305). The branch pipe (1303) is connected by a second branch pipe (1306) and a through hole (7).

2. The high-torque marine propulsion variable frequency motor according to claim 1, characterized in that: The bottom of the inner housing (1) is provided with a first mounting groove (2) for accommodating multiple sets of connecting components (10), and the two ends of the inner housing (1) are provided with fixing feet (4) for mounting end caps (15). The top of the inner housing (1) is provided with a control box (17), and the side of the control box (17) is provided with a protective cover (16).

3. The high-torque marine propulsion variable frequency motor according to claim 2, characterized in that: The outer shell (5) and the inner shell (1) are sealed and fixed by welding. The outer shell (5) is provided with multiple sets of heat dissipation fins (8), and the bottom of the outer shell (5) is provided with connecting feet (18).

4. The high-torque marine propulsion variable frequency motor according to claim 3, characterized in that: The multiple sets of annular cooling channels (9) are vertically distributed and are evenly arranged along the axial direction of the base shell.

5. The high-torque marine propulsion variable frequency motor according to claim 4, characterized in that: The top of the main pipe (1301) is provided with a second plug (1302), which is used to connect the flushing water.

6. The high-torque marine propulsion variable frequency motor according to claim 5, characterized in that: The cooling channel is an annular folding groove (19) opened on the outer wall of the inner shell (1) and the inner wall of the outer shell (5). Multiple sets of clips (20) are provided at the bottom of the outer shell (5), and a second mounting groove (21) is opened at the bottom of the outer shell (5). A bottom shell (22) is installed at the bottom of the second mounting groove (21).

7. The high-torque marine propulsion variable frequency motor according to claim 6, characterized in that: The bottom shell (22) includes a sealing plate (2201). The top of the sealing plate (2201) has multiple sets of semi-arc grooves (2202). The multiple sets of semi-arc grooves (2202) and the annular folding groove (19) are matched and are part of the cooling channel. The top of the sealing plate (2201) is provided with a second water inlet (2203) and a second water outlet (2204). The second water inlet (2203) and the second water outlet (2204) are connected to the cooling system.

8. The high-torque marine propulsion variable frequency motor according to claim 7, characterized in that: The top of the sealing plate (2201) is provided with a fitting groove (2205) at the location of multiple semi-arc grooves (2202), the second inlet (2203) and the second outlet (2204), and the fitting groove (2205) matches the card (20).

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