Lubricating oil filter

Abstract

The utility model provides a lubricating oil filter, which relates to filtering equipment and comprises a filter cartridge and a base, a center hole is formed in the base, and the filter cartridge extends into the center hole; a guide piece is arranged on the outer side wall of the filter cartridge and is used for sliding in a manner of being attached to the inner wall of the base; the side wall of the filter cartridge comprises a binding surface and a filter surface, and the binding surface and the filter surface are correspondingly arranged; the guide piece is arranged on the filtering surface; when the guiding piece is attached to the inner wall of the base, the attaching face is attached to the inner wall of the base. The guide piece is attached to the inner wall of the base to slide, deformation or damage caused by uneven stress of the filter cartridge is avoided, when the filter cartridge is subjected to pressure from lubricating oil or other external pressure, the pressure can be effectively dispersed to the whole attaching face, local stress is prevented from being too large, and the structural strength of the connecting position of the filter cartridge and the base is enhanced.

Description

Technical Field

[0001] The utility model relates to filtering equipment, in particular to a lubricating oil filter. Background Art

[0002] When manually installing the filter cartridge into the base, it is difficult to accurately control the direction and magnitude of the applied force, which can easily lead to uneven force on various parts. For example, one side may be over-tightened while the other side is not sufficiently tightened. When the rigidity of the filter cartridge structure is insufficient, the fixing bolts are tightened, and the stress in the deformed part is significantly increased, while the non-deformed part may be relatively loose, resulting in uneven stress. As the fixing bolts are gradually tightened, the preload force of each bolt will be different, causing the filter cartridge to be skewed or misaligned, and the fitting surface of the filter cartridge cannot completely fit the inner wall of the base, which not only aggravates the uneven stress, but also causes poor sealing at the joint, causing lubricating oil leakage. Utility Model Content

[0003] The utility model aims to provide a lubricating oil filter, and the technical problem to be solved is the uneven stress distribution during installation.

[0004] The utility model is realized by the following technical solutions:

[0005] A lubricating oil filter comprises a filter cartridge and a base;

[0006] The base is provided with a central hole, and the filter cartridge extends into the central hole;

[0007] The outer wall of the filter cartridge is provided with a guide member, which is used to slide against the inner wall of the base;

[0008] The side wall of the filter cartridge includes a fitting surface and a filtering surface, and the fitting surface is arranged corresponding to the filtering surface;

[0009] The guide member is arranged on the filter surface; when the guide member is in contact with the inner wall of the base, the contact surface is in contact with the inner wall of the base.

[0010] By providing a guide on the outer wall of the filter cartridge and enabling it to slide against the inner wall of the base, this design ensures that the filter cartridge can be accurately aligned and smoothly inserted into the center hole of the base during installation, thereby reducing installation difficulty and improving installation efficiency.

[0011] The side wall of the filter cartridge is provided with a fitting surface and a filtering surface, and the guide is located on the filtering surface. During the installation process, the fitting effect of the guide and the inner wall of the base enables the filter cartridge to move smoothly along a preset track during the insertion process, thereby avoiding deformation or damage caused by uneven force and ensuring the overall stability of the filter cartridge.

[0012] When the guide member fits against the inner wall of the base, the fitting surface is tightly fitted against the inner wall of the base, so when the filter cartridge is subjected to pressure from the lubricating oil or other external pressure, the pressure can be effectively dispersed to the entire fitting surface to prevent excessive local stress, further enhancing the structural strength of the connection between the filter cartridge and the base and extending the service life of the equipment. Due to the close fit between the filter cartridge and the base, the lubricating oil is prevented from flowing directly through the gap without being fully filtered, thereby ensuring the filtering effect and reducing the risk of lubricating oil leakage due to poor sealing.

[0013] In summary, the design of the lubricating oil filter not only achieves precise docking between the filter cartridge and the base, but also ensures uniform distribution of stress during installation and use, thereby improving the overall performance and service life of the equipment.

[0014] Furthermore, the fitting surface of the filter cartridge is provided with an oil inlet, and the base is provided with an oil inlet pipe;

[0015] The oil inlet is used to communicate with the oil inlet pipe;

[0016] A sealing member is arranged beside the oil inlet, and the sealing member is used to seal the connection gap when the oil inlet is connected with the oil inlet pipe.

[0017] The fitting surface of the above-mentioned filter cartridge is provided with an oil inlet and is designed to correspond to the oil inlet pipe on the base in order to achieve smooth introduction of the lubricating oil; when the filter cartridge is correctly installed in place, the oil inlet will be precisely docked and connected with the oil inlet pipe on the base, forming a channel for the lubricating oil to enter the interior of the filter cartridge for filtration.

[0018] It is particularly pointed out that a seal is arranged next to the oil inlet. When the oil inlet is connected to the oil inlet pipe, the seal can effectively fill the connection gap between the two, ensuring the airtightness and leak-proofness of the connection part, preventing the lubricating oil from leaking out of the connection gap without being filtered. This not only ensures the filtration efficiency, but also reduces the waste of resources, while avoiding the safety hazards caused by oil leakage. This design improves the working efficiency and reliability of the filter.

[0019] Furthermore, the guide member is arranged opposite to the oil inlet.

[0020] The above-mentioned guide member is mainly used to ensure the accurate docking and stable sliding between the filter cartridge and the base, and prevent offset and misalignment during installation; the oil inlet is responsible for the input of lubricating oil; the two are arranged back to back, that is, they are located on the opposite sides of the filter cartridge respectively. The guide member can not only play a guiding role, but also make the oil inlet close to the oil inlet pipe. On the one hand, the surrounding of the oil inlet (that is, the fitting surface) is tightly fitted with the inner wall of the base, further strengthening the sealing of the connection between the oil inlet pipe and the oil inlet; on the other hand, arranging the guide member and the oil inlet on the opposite sides of the filter cartridge not only meets their respective functional requirements, but also avoids mutual interference between functional components.

[0021] Furthermore, the guide member extends from the top end of the filter cartridge to the bottom end of the filter cartridge.

[0022] After the filter cartridge enters the center hole, the guide member completely covers the guide of the filter cartridge, and can play a good guiding role from top to bottom, so that the filter cartridge can always move smoothly in a straight line during the process of inserting or removing the filter cartridge from the center hole of the base, reducing the risk of jamming and deflection, and ensuring a smoother installation and disassembly process; the continuous existence of the guide member from top to bottom means that stable support can be provided throughout the contact surface between the filter cartridge and the base, which helps to distribute the axial pressure and shear force of the filter cartridge more evenly throughout the cartridge body, reduce local stress concentration, and enhance equipment durability and stability.

[0023] The guide member runs through the entire length of the filter cartridge, which helps to improve the sealing performance between the fitting surface and the inner wall of the base, prevents lubricating oil from leaking from the contact gap, and also enhances the stability of the filter cartridge in the working state, ensuring the filtering effect and safe operation of the equipment.

[0024] Furthermore, the sealing member is arranged on the fitting surface.

[0025] The seal between the filter cartridge and the base is made into an integrated structure, which simplifies the assembly steps, reduces additional sealing links and components, makes the overall structure more compact, and is conducive to the miniaturization and lightweight of the equipment.

[0026] Placing the seal on the fitting surface and close to the oil inlet can ensure sealing without affecting the normal flow of lubricating oil from the oil inlet into the filter cartridge, thereby ensuring efficient and orderly operation of the filter; directly arranging the above-mentioned seal on the fitting surface of the filter cartridge, when the filter cartridge is tightly fitted with the base, the seal can be tightly fitted with the corresponding part on the base to form an effective sealing barrier, thereby preventing lubricating oil from leaking from the connection part to the greatest extent, thereby ensuring the sealing and safety of the filtration system.

[0027] Furthermore, the sealing member is overlapped and arranged on the fitting surface;

[0028] When the guide member is in contact with the inner wall of the base, the sealing member is in contact with the inner wall of the base.

[0029] The overlapping seals increase the depth of contact with the inner wall of the base, enhance the tightness and firmness of the seal, thereby greatly improving the overall sealing effect and effectively preventing the occurrence of minor leakage of lubricating oil under high pressure or after long-term use; to a certain extent, they have better elastic compensation ability, and can maintain good sealing performance through their own deformation even under conditions such as temperature changes, pressure fluctuations or long-term wear;

[0030] When the guide member fits against the inner wall of the base, since the seal is overlapped on the fitting surface and fits against the inner wall of the base, after the filter cartridge is installed in the corresponding position, it can not only ensure a tight seal between the filter cartridge and the base, but also through the double constraints of the seal and the inner wall of the base, the position of the filter cartridge in the working state can be more stable, reducing loosening or displacement caused by vibration and other factors.

[0031] Furthermore, the end face of the sealing element is an inclined face, and the angle between the inclined face and the side wall of the filter cartridge is an acute angle.

[0032] Compared with the vertical surface, the acute angle inclined surface can reduce the friction resistance when inserting and removing the filter cartridge, which is convenient for the installation and disassembly of the equipment, while reducing unnecessary wear and extending the service life of the seal.

[0033] Furthermore, the filter also includes a fixing member, and the fixing member is connected to the filter cartridge;

[0034] The fixing member is detachably connected to the base;

[0035] The filter cartridge is fixed in the center hole by the fixing member.

[0036] Through the above-mentioned fixings, the user can easily install the filter cartridge into the center hole of the base, or remove it when the filter cartridge needs to be replaced, which greatly facilitates daily maintenance and parts replacement operations.

[0037] The fixing member fixes the filter cartridge in the center hole, ensuring the stability of the filter cartridge in the working state and avoiding shaking or displacement of the filter cartridge in the center hole due to the pressure of the lubricating fluid or other factors, thereby ensuring the stability of the filtering effect and the safety of the equipment operation.

[0038] Compared with the prior art, the utility model has the following advantages and beneficial effects:

[0039] By providing a guide on the outer wall of the filter cartridge and enabling it to slide against the inner wall of the base, this design ensures that the filter cartridge can be accurately aligned and smoothly inserted into the center hole of the base during installation, thereby reducing installation difficulty and improving installation efficiency.

[0040] The side wall of the filter cartridge is provided with a fitting surface and a filtering surface, and the guide is located on the filtering surface. During the installation process, the fitting effect of the guide and the inner wall of the base enables the filter cartridge to move smoothly along a preset track during the insertion process, thereby avoiding deformation or damage caused by uneven force and ensuring the overall stability of the filter cartridge.

[0041] When the guide member fits against the inner wall of the base, the fitting surface is tightly fitted against the inner wall of the base, so when the filter cartridge is subjected to pressure from the lubricating oil or other external pressure, the pressure can be effectively dispersed to the entire fitting surface to prevent excessive local stress, further enhancing the structural strength of the connection between the filter cartridge and the base and extending the service life of the equipment. Due to the close fit between the filter cartridge and the base, the lubricating oil is prevented from flowing directly through the gap without being fully filtered, thereby ensuring the filtering effect and reducing the risk of lubricating oil leakage due to poor sealing.

[0042] In summary, the design of the lubricating oil filter not only achieves precise docking between the filter cartridge and the base, but also ensures uniform distribution of stress during installation and use, thereby improving the overall performance and service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present utility model, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present utility model, and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0044] Figure 1 It is a schematic diagram of the overall structure of the lubricating oil filter;

[0045] Figure 2 It is a half-section view of the lubricating oil filter;

[0046] Figure 3 It is a half-section view of the base;

[0047] Figure 4 It is a structural schematic diagram of the filter cartridge;

[0048] Figure 5 It is a schematic diagram of the structure after the filter cartridge, the guide member and the seal member are connected;

[0049] Figure 6for Figure 5 Top view of the .

[0050] Marks and corresponding parts names in the attached drawings:

[0051] 10. Base; 11. Oil inlet pipe; 12. Center hole; 20. Filter cartridge; 21. Filter surface; 22. Fitting surface; 23. Oil inlet; 30. Guide piece; 40. Sealing piece; 50. Fixing piece. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments and drawings. The schematic implementation manner of the utility model and its description are only used to explain the utility model and are not intended to limit the utility model.

[0053] Example 1

[0054] Combination Figures 1 to 6 , this embodiment 1 provides a lubricating oil filter, characterized in that it includes a filter cartridge 20 and a base 10;

[0055] The base 10 is provided with a central hole 12, and the filter cartridge 20 extends into the central hole 12;

[0056] The outer wall of the filter cartridge 20 is provided with a guide member 30, and the guide member 30 is used to slide against the inner wall of the base 10;

[0057] The side wall of the filter cartridge 20 includes a fitting surface 22 and a filtering surface 21, and the fitting surface 22 and the filtering surface 21 are arranged correspondingly;

[0058] The guide member 30 is disposed on the filter surface 21 ; when the guide member 30 is in contact with the inner wall of the base 10 , the contact surface 22 is in contact with the inner wall of the base 10 .

[0059] By providing a guide member 30 on the outer wall of the filter cartridge 20 and enabling it to slide against the inner wall of the base 10, this design ensures that the filter cartridge 20 can be accurately aligned and smoothly inserted into the center hole 12 of the base 10 during installation, thereby reducing installation difficulty and improving installation efficiency.

[0060] The side wall of the filter cartridge 20 is provided with a fitting surface 22 and a filtering surface 21, and the guide member 30 is located on the filtering surface 21. During the installation process, the fitting effect of the guide member 30 and the inner wall of the base 10 enables the filter cartridge 20 to move smoothly along a preset track during the insertion process, thereby avoiding deformation or damage caused by uneven force and ensuring the overall stability of the filter cartridge 20.

[0061] When the guide member 30 is attached to the inner wall of the base 10, the attachment surface 22 is in close contact with the inner wall of the base 10, so that when the filter cartridge 20 is subjected to pressure from the lubricating oil or other external pressure, the pressure can be effectively dispersed to the entire attachment surface 22 to prevent excessive local stress, thereby further enhancing the structural strength of the connection between the filter cartridge 20 and the base 10 and extending the service life of the equipment. Due to the close fit between the filter cartridge 20 and the base 10, the lubricating oil is prevented from flowing directly through the gap without being fully filtered, thereby ensuring the filtering effect and reducing the risk of lubricating oil leakage due to poor sealing.

[0062] In summary, the design of the lubricating oil filter not only achieves precise docking between the filter cartridge 20 and the base 10, but also ensures uniform distribution of stress during installation and use, thereby improving the overall performance and service life of the equipment.

[0063] In a specific embodiment, the fitting surface 22 of the filter cartridge 20 is provided with an oil inlet 23, and the base 10 is provided with an oil inlet pipe 11;

[0064] The oil inlet 23 is used to communicate with the oil inlet pipe 11;

[0065] A sealing member 40 is disposed beside the oil inlet 23 , and the sealing member 40 is used to seal a connection gap between the oil inlet 23 and the oil inlet pipe 11 .

[0066] The fitting surface 22 of the filter cartridge 20 is provided with an oil inlet 23, and the oil inlet 23 is designed to correspond to the oil inlet pipe 11 on the base 10 in order to achieve smooth introduction of lubricating oil; when the filter cartridge 20 is correctly installed in place, the oil inlet 23 will be precisely docked and connected with the oil inlet pipe 11 on the base 10, forming a channel for the lubricating oil to enter the interior of the filter cartridge 20 for filtration.

[0067] It is particularly pointed out that a seal 40 is arranged beside the oil inlet 23. When the oil inlet 23 is connected to the oil inlet pipe 11, the seal 40 can effectively fill the connection gap between the two, ensuring the air tightness and leak-proofness of the connection part, and preventing the lubricating oil from leaking out of the connection gap without being filtered. This not only ensures the filtering efficiency, but also reduces the waste of resources, and avoids the safety hazards caused by oil leakage. This design improves the working efficiency and reliability of the filter.

[0068] Example 2

[0069] On the basis of Example 1, when multiple guide members 30 are provided, the guide members 30 are longitudinally arranged at equal intervals on the filter surface 21. The function of the multiple guide members 30 after cooperating with the base 10 is to evenly disperse the stress on the fitting surface 22 so that the fitting surface 22 is closely fitted to the inner wall of the base 10.

[0070] When a guide member 30 is provided, the guide member 30 is disposed opposite to the oil inlet 23 (eg Figure 5 As shown), the guide member 30 cooperates with the base 10 to function as follows:

[0071] The above-mentioned guide member 30 is mainly used to ensure the accurate docking and stable sliding between the filter cartridge 20 and the base 10, and prevent deviation and misalignment during the installation process; the oil inlet 23 is responsible for the input of lubricating oil; the two are arranged back to back, that is, they are respectively located on the opposite sides of the filter cartridge 20. On the one hand, the guide member 30 is used for guidance; on the other hand, under the action of the guide member 30, the oil inlet 23 is pushed toward the inner wall of the base 10, so that the surrounding of the oil inlet 23 (that is, the fitting surface 22) is tightly fitted with the inner wall of the base 10, further strengthening the sealing of the connection between the oil inlet pipe 11 and the oil inlet 23; arranging the guide member 30 and the oil inlet 23 on the opposite sides of the filter cartridge 20 not only meets their respective functional requirements, but also avoids mutual interference between functional components.

[0072] Example 3

[0073] Based on Example 2, the guide member 30 extends from the top end of the filter cartridge 20 to the bottom end of the filter cartridge 20. Figure 5 shown.

[0074] After the filter cartridge 20 enters the center hole 12, the guide member 30 completely covers the guide of the filter cartridge 20, and can play a good guiding role from top to bottom, so that the filter cartridge 20 can always move smoothly in a straight line during the process of inserting or removing the filter cartridge 20 from the center hole 12 of the base 10, reducing the risk of jamming and deflection, and ensuring a smoother installation and disassembly process; the continuous existence of the guide member 30 from top to bottom means that it can provide stable support throughout the contact surface between the filter cartridge 20 and the base 10, which helps to distribute the axial pressure and shear force on the filter cartridge 20 more evenly throughout the cylinder body, reduce local stress concentration, and enhance the durability and stability of the equipment.

[0075] The guide member 30 runs through the entire length of the filter cartridge 20, which helps to improve the sealing performance between the fitting surface 22 and the inner wall of the base 10, prevents the lubricating oil from leaking from the contact gap, and also enhances the stability of the filter cartridge 20 in the working state, ensuring the filtering effect and the safe operation of the equipment.

[0076] Example 4

[0077] Combination Figure 5 and Figure 6 Based on any of the above embodiments, the sealing member 40 is disposed on the fitting surface 22 .

[0078] The seal between the filter cartridge 20 and the base 10 becomes an integrated structure, which simplifies the assembly steps, reduces additional sealing links and components, makes the overall structure more compact, and is conducive to the miniaturization and lightweight of the equipment.

[0079] Placing the seal 40 on the fitting surface 22 and close to the oil inlet 23 can ensure sealing without affecting the normal flow of lubricating oil from the oil inlet 23 into the filter cartridge 20, thereby ensuring efficient and orderly operation of the filter; directly setting the above-mentioned seal 40 on the fitting surface 22 of the filter cartridge 20, when the filter cartridge 20 is tightly fitted with the base 10, the seal 40 can be tightly fitted with the corresponding part on the base 10 to form an effective sealing barrier, thereby preventing lubricating oil from leaking from the connection part to the greatest extent, thereby ensuring the sealing and safety of the filtration system.

[0080] In a specific embodiment, the sealing member 40 is overlapped and disposed on the fitting surface 22 by welding or the like. The sealing member 40 of this embodiment covers all areas of the fitting surface 22. Of course, the sealing member 40 may also only cover the area of ​​the fitting surface 22 near the oil inlet 23.

[0081] When the guide member 30 is in contact with the inner wall of the base 10 , the seal member 40 is in contact with the inner wall of the base 10 .

[0082] The overlapping seals 40 increase the depth of contact with the inner wall of the base 10, enhance the tightness and firmness of the seal, thereby greatly improving the overall sealing effect, effectively preventing the occurrence of minor leakage of lubricating oil under high pressure or after long-term use; to a certain extent, they have better elastic compensation ability, and can maintain good sealing performance through their own deformation even under conditions such as temperature changes, pressure fluctuations or long-term wear;

[0083] When the guide member 30 is in contact with the inner wall of the base 10, the seal 40 is overlapped on the contact surface 22 and in contact with the inner wall of the base 10. Therefore, after the filter cartridge 20 is installed in place, it can not only ensure a tight seal between the filter cartridge 20 and the base 10, but also, through the double constraints of the seal 40 and the inner wall of the base 10, the position of the filter cartridge 20 in the working state can be more stable, thereby reducing loosening or displacement caused by vibration and other factors.

[0084] Example 5

[0085] Combination Figure 5 and Figure 6 Based on any of the above embodiments, the end face of the seal 40 (the end face is the thickness face of the seal 40) is an inclined face, and the angle between the inclined face and the side wall of the filter cartridge 20 is an acute angle.

[0086] Compared with a vertical surface, the acute angle inclined surface can reduce friction resistance when inserting and removing the filter cartridge 20, which facilitates installation and removal of the equipment, while reducing unnecessary wear and tear and extending the service life of the seal 40.

[0087] Example 6

[0088] Combination Figure 1 and Figure 2 , based on any of the above embodiments, the filter further comprises a fixing member 50, and the fixing member 50 is connected to the filter cartridge 20;

[0089] The fixing member 50 is detachably connected to the base 10 by bolts;

[0090] The filter cartridge 20 is fixed in the central hole 12 by the fixing member 50 .

[0091] Through the fixing member 50 , the user can easily install the filter cartridge 20 into the central hole 12 of the base 10 , or remove the filter cartridge 20 when it is necessary to replace it, which greatly facilitates daily maintenance and parts replacement operations.

[0092] The fixing member 50 fixes the filter cartridge 20 in the center hole 12, ensuring the stability of the filter cartridge 20 in the working state and avoiding shaking or displacement of the filter cartridge 20 in the center hole 12 due to the pressure of the lubricating fluid or other factors, thereby ensuring the stability of the filtering effect and the safety of the equipment operation.

[0093] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the utility model in detail. It should be understood that the above description is only the specific implementation method of the utility model and is not used to limit the protection scope of the utility model. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the utility model should be included in the protection scope of the utility model.

Claims

1. A lubricating oil filter, characterized in that: It comprises a filter cartridge (20) and a base (10); The base (10) is provided with a central hole (12), and the filter cartridge (20) extends into the central hole (12); The outer wall of the filter cartridge (20) is provided with a guide member (30), and the guide member (30) is used to slide against the inner wall of the base (10); The side wall of the filter cartridge (20) comprises a fitting surface (22) and a filtering surface (21), and the fitting surface (22) and the filtering surface (21) are arranged correspondingly; The guide member (30) is arranged on the filtering surface (21); when the guide member (30) is in contact with the inner wall of the base (10), the contact surface (22) is in contact with the inner wall of the base (10).

2. A lubricating oil filter according to claim 1, characterized in that: The fitting surface (22) of the filter cartridge (20) is provided with an oil inlet (23), and the base (10) is provided with an oil inlet pipe (11); The oil inlet (23) is used to communicate with the oil inlet pipe (11); A sealing member (40) is provided on the side of the oil inlet (23), and the sealing member (40) is used to seal the connection gap when the oil inlet (23) is connected to the oil inlet pipe (11).

3. A lubricating oil filter according to claim 2, characterized in that: The guide member (30) is arranged opposite to the oil inlet (23).

4. A lubricating oil filter according to claim 3, characterized in that: The guide member (30) extends from the top end of the filter cartridge (20) to the bottom end of the filter cartridge (20).

5. The lubricating oil filter according to claim 2, characterized in that: The sealing member (40) is arranged on the fitting surface (22).

6. A lubricating oil filter according to claim 5, characterized in that: The sealing member (40) is overlapped and arranged on the fitting surface (22); When the guide member (30) is in contact with the inner wall of the base (10), the sealing member (40) is in contact with the inner wall of the base (10).

7. A lubricating oil filter according to claim 6, characterized in that: The end face of the sealing member (40) is an inclined face, and the angle between the inclined face and the side wall of the filter cartridge (20) is an acute angle.

8. The lubricating oil filter according to claim 1, characterized in that: The filter further comprises a fixing member (50), wherein the fixing member (50) is connected to the filter cartridge (20); The fixing member (50) is detachably connected to the base (10); The filter cartridge (20) is fixed in the central hole (12) by means of the fixing member (50).

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