Long-life needle plate for ceramic fiber

Abstract

The utility model discloses a long-life needle plate for ceramic fiber, which belongs to the technical field of ceramic fiber processing equipment and comprises a needle pricking machine main body, the main body is provided with a main shaft, an eccentric wheel, a push rod, an upper needle plate, a stripping guide plate, a lower needle plate, a stress guide plate and the like, and the top of the upper needle plate is sequentially provided with an aluminum magnesium alloy base plate, high-temperature-resistant fluororubber and a nylon plate. The aluminum magnesium alloy base plate is used for enhancing strength, the high-temperature-resistant fluororubber and the nylon plate are used for improving abrasion resistance, the top of each pricking needle is of an L-shaped structure and is fixed through a countersunk bolt, the root of each pricking needle is matched with a through hole in each plate to guarantee installation precision, the needle plate grooves are formed in the outer sides of the needle plates, and installation stability is guaranteed through the clamping plates, the positioning grooves and the positioning pins; according to the ceramic fiber needle plate, the problems that a traditional needle plate is short in service life and prone to damage are solved, and the machining quality and efficiency of ceramic fibers are improved.

Description

Technical Field

[0001] This utility model belongs to the technical field of ceramic fiber processing, specifically relating to a long-life needle plate for ceramic fibers. Background Technology

[0002] Ceramic fiber blankets are made from natural high-quality calcined gemstones or synthetic alumina powder, silica, zircon sand, etc., through processes such as resistance melting, blowing or spinning, collecting, needle punching, and sintering. Needle punching is an essential process in the production of ceramic fiber blankets. The loose ceramic fiber cotton from the collecting box is woven into a blanket-like product with a certain thickness and strength by passing it through a needle plate that swings up and down.

[0003] However, existing needle plates tend to bend along their length after a period of use. The raised sections cannot be properly needled, affecting the number of needles on the cotton blanket's surface and resulting in poor appearance. This also reduces the tensile strength of the blanket. Since the fiber blanket contains crystalline particles, needle breakage easily occurs when the needles encounter these particles during their up-and-down movement. These broken needles are mostly mixed into the cotton blanket and can cause problems during subsequent processing or customer installation. Any remaining broken needles pose a safety hazard. As the needle plate's lifespan increases, polyurethane oxidation leads to a continuous decrease in the needle plate's holding power, resulting in more and more broken needles. Simultaneously, the needle plate's deformation becomes increasingly severe, ultimately ending its lifespan. Currently, domestically produced needle plates typically require replacement after about one year. The consumption of both needle plates and needles increases costs. Utility Model Content

[0004] The purpose of this invention is to provide a long-life needle plate for ceramic fibers, in order to solve the problems mentioned in the background art, such as insufficient strength of existing needle plates, easy needle breakage when the needle swings up and down and encounters crystalline particles, the need to add a needle breakage detection process after needle insertion, and increased cost due to the consumption of both needle plates and needles.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a long-life needle plate for ceramic fibers, comprising a needle punching machine body;

[0006] A main shaft is provided at the top of the main body of the needle piercing machine. An eccentric wheel is provided at the outer side of the main shaft. A push rod is provided at the bottom of the eccentric wheel. An upper needle plate is provided at the bottom of the push rod. A peeling guide plate is provided at the bottom of the upper needle plate. A lower needle plate is provided at the bottom of the main body of the needle piercing machine. A force-bearing guide plate is provided above the lower needle plate.

[0007] An aluminum-magnesium alloy substrate is provided at the top of the upper needle plate, a high-temperature resistant fluororubber is provided above the aluminum-magnesium alloy substrate, a nylon plate is provided above the high-temperature resistant fluororubber, and needles are provided inside the upper and lower needle plates.

[0008] Preferably, the aluminum-magnesium alloy substrate has an array of through holes inside, the high-temperature resistant fluororubber has an array of high-temperature resistant fluororubber through holes inside, and the nylon plate has an array of nylon plate through holes inside.

[0009] Preferably, the diameter of the through hole is the same as the diameter of the needle root, the high-temperature resistant fluororubber through hole is 0.1 mm smaller than the needle root, and the nylon plate is 0.1 mm smaller than the needle root.

[0010] Preferably, countersunk bolts are arranged in an array inside the upper and lower needle plates, and a needle tip is provided at the top of the needle, the needle tip having an L-shaped structure.

[0011] Preferably, the cumulative deviation of the through holes does not exceed ±0.5mm, the diameter tolerance of the through holes is ±0.005mm, and the through holes of the upper and lower needle plates are symmetrically distributed.

[0012] Preferably, an upper needle plate groove is provided at the outer side of the upper needle plate, a lower needle plate groove is provided at the outer side of the lower needle plate, and a retaining groove is provided at the inner edge of the upper needle plate groove and the lower needle plate groove.

[0013] Preferably, a retaining plate is provided at the left side of the upper needle plate groove, and a positioning groove is provided at the middle of the left side of the upper needle plate. The positioning groove and the retaining plate are engaged and connected. A positioning pin is provided at the right side of the upper needle plate groove, and a positioning hole corresponding to the positioning pin is provided at the right side of the upper needle plate groove. The same retaining plate and positioning hole are provided inside the lower needle plate groove.

[0014] Preferably, a handle is provided at the top right side of the upper needle plate and the lower needle plate, and the handle is fixedly connected to the upper needle plate and the lower needle plate by an internal hex bolt, and a washer is provided inside the internal hex bolt.

[0015] Compared with the prior art, this utility model provides a long-life needle plate for ceramic fibers, which has the following beneficial effects:

[0016] By incorporating an aluminum-magnesium alloy substrate, high-temperature resistant fluororubber, nylon plates, needles, through holes, and countersunk bolts, the needle plate's strength is enhanced through the aluminum-magnesium alloy substrate, enabling it to withstand the high-intensity operations during ceramic fiber processing and extending its service life. The high-temperature resistant fluororubber and nylon plates improve the needle plate's wear resistance, reducing damage caused by friction. Furthermore, these two materials possess excellent high-temperature resistance, adapting to the high-temperature environment of ceramic fiber processing. The through hole diameter matches the needle root diameter, ensuring the needle's stability. The accuracy and stability of the installation are ensured by using high-temperature fluororubber through holes and nylon plate through holes that are 0.1mm smaller than the root of the needle, which further enhances the fixing effect of the needle and prevents it from shaking during operation. Countersunk bolts are arranged in an array inside the upper and lower needle plates, making the installation of the needle more secure and reliable. The needle tip at the top of the needle has an L-shaped structure, which facilitates the insertion of ceramic fibers and improves processing efficiency. The cumulative deviation of the through holes does not exceed ±0.5mm, and the hole diameter tolerance is ±0.005mm. Moreover, the through holes of the upper and lower needle plates are symmetrically distributed, which ensures the accuracy of the needle installation and improves the processing quality of ceramic fibers.

[0017] With the design of upper and lower needle plate slots, a locking slot, a locking plate, a positioning slot, a positioning pin, and positioning holes, the upper and lower needle plate slots provide accurate installation positions for the upper and lower needle plates, ensuring the stability and accuracy of the needle plates within the needle-pressing machine body. The locking slot further restricts the movement of the needle plates, preventing them from shaking or shifting during operation and ensuring the precision of ceramic fiber processing. The locking plate on the left side inside the upper needle plate slot engages with the positioning slot in the middle of the left side of the upper needle plate. This connection method is simple, reliable, and easy to install and disassemble, while ensuring that the upper needle plate is fixed in position after installation and will not shift. The positioning pin on the right side inside the upper needle plate inserts into the corresponding positioning hole on the right side of the upper needle plate slot, further enhancing the stability and accuracy of the upper needle plate installation. Similarly, the lower needle plate slot has the same locking plate and positioning holes, ensuring the installation accuracy and stability of the lower needle plate. This dual positioning design greatly improves the installation accuracy and stability of the needle plates within the needle-pressing machine body, thereby improving the processing quality and efficiency of ceramic fibers. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of this utility model.

[0019] Figure 2 This is a schematic diagram of the structure of the needle plate in this utility model.

[0020] Figure 3 This is a schematic diagram of the cross-section of the needle plate in this utility model.

[0021] Figure 4This is a schematic diagram of the internal hexagon bolt in this utility model.

[0022] Figure 5 This is a schematic diagram of the through hole in this utility model.

[0023] Figure 6 This is a schematic diagram of the positioning pin in this utility model.

[0024] Figure 7 This is a schematic diagram of the structure of the needle in this utility model.

[0025] Figure 8 This is a schematic diagram of the needle plate groove in this utility model.

[0026] In the diagram: 1. Main body of the needle piercing machine; 2. Main shaft; 3. Eccentric wheel; 4. Upper needle plate groove; 5. Upper needle plate; 6. Needle; 7. Peeling guide plate; 8. Force-bearing guide plate; 9. Lower needle plate; 10. Lower needle plate groove; 11. Countersunk bolt; 12. Handle; 13. Through hole; 14. Positioning groove; 15. Positioning pin; 16. Aluminum-magnesium alloy substrate; 17. High-temperature resistant fluororubber; 18. Nylon plate; 19. Hex socket head cap screw; 20. Washer; 21. High-temperature resistant fluororubber through hole; 22. Nylon plate through hole; 23. Needle; 24. Clamping plate; 25. Positioning hole; 26. Clamping groove. Detailed Implementation

[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0028] This utility model provides, for example Figure 1-8 The ceramic fiber long-life needle plate shown includes a needle punch machine body 1;

[0029] A main shaft 2 is provided at the top of the main body 1 of the needle piercing machine. An eccentric wheel 3 is provided at the outer side of the main shaft 2. A push rod is provided at the bottom of the eccentric wheel 3. An upper needle plate 5 is provided at the bottom of the push rod. A peeling guide plate 7 is provided at the bottom of the upper needle plate 5. A lower needle plate 9 is provided at the bottom of the main body 1 of the needle piercing machine. A force-bearing guide plate 8 is provided above the lower needle plate 9.

[0030] An aluminum-magnesium alloy substrate 16 is provided at the top of the upper needle plate 5, a high-temperature resistant fluororubber 17 is provided above the aluminum-magnesium alloy substrate 16, a nylon plate 18 is provided above the high-temperature resistant fluororubber 17, and needles 6 are provided inside the upper needle plate 5 and the lower needle plate 9.

[0031] The aluminum-magnesium alloy substrate 16 has through holes 13 arranged in an array inside, the high-temperature resistant fluororubber 17 has through holes 21 arranged in an array inside, and the nylon plate 18 has through holes 22 arranged in an array inside.

[0032] The diameter of the through hole 13 is the same as the diameter of the root of the needle 6. The high-temperature resistant fluororubber through hole 21 is 0.1 mm smaller than the root of the needle 6. The nylon plate 18 is 0.1 mm smaller than the root of the needle 6.

[0033] Countersunk bolts 11 are arranged in an array inside the upper needle plate 5 and the lower needle plate 9. A needle head 23 is provided at the top of the needle 6. The needle head 23 has an L-shaped structure.

[0034] The cumulative deviation of through hole 13 does not exceed ±0.5mm, and the diameter tolerance of through hole 13 is ±0.005mm. Through holes 13 are symmetrically distributed on the upper needle plate 5 and the lower needle plate 9.

[0035] An upper needle plate groove 4 is provided on the outer side of the upper needle plate 5, and a lower needle plate groove 10 is provided on the outer side of the lower needle plate 9. A retaining groove 26 is provided at the inner edge of the upper needle plate groove 4 and the lower needle plate groove 10.

[0036] A retaining plate 24 is provided on the left side of the upper needle plate groove 4, and a positioning groove 14 is provided on the middle left side of the upper needle plate 5. The positioning groove 14 and the retaining plate 24 are connected by a retaining plate. A positioning pin 15 is provided on the right side of the upper needle plate 5, and a positioning hole 25 corresponding to the positioning pin 15 is provided on the right side of the upper needle plate groove 4. The same retaining plate 24 and positioning hole 25 are provided inside the lower needle plate groove 10.

[0037] A handle 12 is provided at the top right side of the upper needle plate 5 and the lower needle plate 9. The handle 12 is fixedly connected to the upper needle plate 5 and the lower needle plate 9 by a hexagon socket head cap screw 19. A washer 20 is provided inside the hexagon socket head cap screw 19.

[0038] In this embodiment, the specific implementation steps of a long-life needle plate for ceramic fibers are as follows: The upper needle plate 5 is placed into the upper needle plate groove 4 at the corresponding position of the needle-sticking machine body 1. The upper needle plate 5 is engaged with the positioning groove 14 at the middle left position of the upper needle plate 5 via the retaining plate 24 inside the upper needle plate groove 4. Simultaneously, the positioning pin 15 inside the upper needle plate 5 is inserted into the corresponding positioning hole 25 at the right side position of the upper needle plate groove 4 to ensure accurate and stable installation of the upper needle plate 5. The lower needle plate 9 is then installed into the lower needle plate at the bottom position of the needle-sticking machine body 1 using the same method. In the slot 10, the needle 6 is passed sequentially through the countersunk bolts 11 inside the upper needle plate 5 and the lower needle plate 9, ensuring that the needle tip 23 at the top of the needle 6 faces upward and has an L-shaped structure. The position of the needle 6 is adjusted so that its root corresponds to the through hole 13 inside the aluminum-magnesium alloy substrate 16, the high-temperature fluororubber through hole 21 inside the high-temperature fluororubber 17, and the nylon plate through hole 22 inside the nylon plate 18. The diameter of the through hole 13 is the same as the diameter of the root of the needle 6, the high-temperature fluororubber through hole 21 is slightly smaller than the root of the needle 6 by 0.1 mm, and the nylon plate 18 is slightly smaller than the root of the needle 6 by 0.1 mm. The root of the needle 6 is slightly smaller by 0.1mm to ensure the installation accuracy and stability of the needle 6. When the main body 1 of the needle-piercing machine is started, the main shaft 2 drives the eccentric wheel 3 to rotate. The eccentric wheel 3 pushes the upper needle plate 5 downwards via a push rod, causing the needle 6 to pierce the ceramic fiber for processing. The peeling guide plate 7 at the bottom of the upper needle plate 5 and the force-bearing guide plate 8 above the lower needle plate 9 play a guiding and supporting role during processing. When maintenance of the needle plate or replacement of the needle 6 is required, it can be disassembled through the handle 12 located at the top right side of the upper needle plate 5 and the lower needle plate 9. The upper needle plate 5 and lower needle plate 9 are fixedly connected by hex bolts 19. When disassembling, first unscrew the hex bolts 19. The washer 20 inside the hex bolts 19 can prevent the bolts from loosening. When disassembling the lower needle plate 9, follow the reverse order of installation. First, pull out the positioning pin 15, and then separate the retaining plate 24 from the positioning groove 14. The lower needle plate 9 can then be taken out from the lower needle plate groove 10. Similarly, the upper needle plate 5 can be disassembled. The disassembled needle plate and needle 6 can be inspected, cleaned or replaced, and then reinstalled and used according to the installation procedure.

[0039] like Figure 1-6As shown, an aluminum-magnesium alloy substrate 16 is disposed at the top of the upper needle plate 5, a high-temperature resistant fluororubber 17 is disposed above the aluminum-magnesium alloy substrate 16, a nylon plate 18 is disposed above the high-temperature resistant fluororubber 17, and needles 6 are disposed inside the upper needle plate 5 and the lower needle plate 9. Through holes 13 are arranged in an array inside the aluminum-magnesium alloy substrate 16, high-temperature resistant fluororubber through holes 21 are arranged in an array inside the high-temperature resistant fluororubber 17, and nylon plate through holes 22 are arranged in an array inside the nylon plate 18. 2. The diameter of the through hole 13 is the same as the diameter of the root of the needle 6. The high-temperature resistant fluororubber through hole 21 is 0.1 mm smaller than the root of the needle 6. The nylon plate 18 is 0.1 mm smaller than the root of the needle 6. Countersunk bolts 11 are arranged in an array inside the upper needle plate 5 and the lower needle plate 9. A needle head 23 is provided at the top of the needle 6. The needle head 23 has an L-shaped structure. The cumulative deviation of the through hole 13 does not exceed ±0.5 mm. The diameter tolerance of the through hole 13 is ±0.005 mm. The through holes 13 of the upper needle plate 5 and the lower needle plate 9 are symmetrically distributed.

[0040] Preferably, an aluminum-magnesium alloy substrate 16 is used to enhance the strength of the needle plate, enabling it to withstand the high-intensity operations during ceramic fiber processing and extending its service life. The inclusion of high-temperature resistant fluororubber 17 and nylon plates 18 improves the wear resistance of the needle plate and reduces damage caused by friction. Simultaneously, these two materials have excellent high-temperature resistance, adapting to the high-temperature environment during ceramic fiber processing. The diameter of the through-hole 13 is consistent with the diameter of the root of the needle 6, ensuring the accuracy and stability of needle installation. The high-temperature resistant fluororubber through-hole 21 and the nylon plate through-hole... The needle 22 is 0.1mm smaller than the root of the needle, which further enhances the fixing effect of the needle and prevents the needle from shaking during operation. Countersunk bolts 11 are arranged in an array inside the upper needle plate 5 and the lower needle plate 9 to make the installation of the needle 6 more secure and reliable. The needle tip 23 at the top of the needle 6 has an L-shaped structure, which facilitates the insertion of ceramic fibers and improves processing efficiency. The cumulative deviation of the through hole 13 does not exceed ±0.5mm, and the hole diameter tolerance is ±0.005mm. Moreover, the through holes 13 of the upper needle plate 5 and the lower needle plate 9 are symmetrically distributed, which ensures the accuracy of the needle installation and improves the processing quality of ceramic fibers.

[0041] like Figure 1 and Figure 8 As shown, an upper needle plate groove 4 is provided on the outer side of the upper needle plate 5, and a lower needle plate groove 10 is provided on the outer side of the lower needle plate 9. A retaining groove 26 is provided at the inner edge of the upper needle plate groove 4 and the lower needle plate groove 10. A retaining plate 24 is provided on the left side of the upper needle plate groove 4. A positioning groove 14 is provided at the middle left side of the upper needle plate 5. The positioning groove 14 and the retaining plate 24 are engaged and connected. A positioning pin 15 is provided on the right side of the upper needle plate 5. A positioning hole 25 corresponding to the positioning pin 15 is provided on the right side of the upper needle plate groove 4. The same retaining plate 24 and positioning hole 25 are provided inside the lower needle plate groove 10.

[0042] Preferably, the upper needle plate groove 4 and the lower needle plate groove 10 provide accurate installation positions for the upper needle plate 5 and the lower needle plate 9, ensuring the stability and accuracy of the needle plate installation in the needle punching machine body. The presence of the retaining groove 26 can further restrict the movement of the needle plate, preventing the needle plate from shaking or shifting during operation, and ensuring the precision of ceramic fiber processing. The retaining plate 24 on the left side inside the upper needle plate groove 4 is engaged with the positioning groove 14 at the middle position on the left side of the upper needle plate 5. This connection method is simple and reliable, easy to install and disassemble, and can ensure that the upper needle plate 5 is fixed in position after installation and will not shift. The positioning pin 15 on the right side inside the upper needle plate 5 is inserted into the corresponding positioning hole 25 at the right side position of the upper needle plate groove 4, further enhancing the stability and accuracy of the installation of the upper needle plate 5. Similarly, the lower needle plate groove 10 is provided with the same retaining plate 24 and positioning hole 25, ensuring the installation accuracy and stability of the lower needle plate 9. This dual positioning design greatly improves the installation accuracy and stability of the needle plate in the needle punching machine body, thereby improving the processing quality and efficiency of ceramic fibers.

[0043] like Figure 1-8 As shown, a handle 12 is provided at the top right side of the upper needle plate 5 and the lower needle plate 9. The handle 12 is fixedly connected to the upper needle plate 5 and the lower needle plate 9 by an internal hex bolt 19. A washer 20 is provided inside the internal hex bolt 19.

[0044] Optionally, a handle 12 is provided at the top right side of the upper needle plate 5 and the lower needle plate 9 to facilitate the installation and removal of the needle plates. Operators can easily insert or remove the needle plates into or from the main body of the needle injection machine by holding the handle 12, which improves work efficiency. The handle 12 is fixedly connected to the upper needle plate 5 and the lower needle plate 9 by a hexagon socket head cap screw 19. The hexagon socket head cap screw 19 has the advantages of strong fastening force and is not easy to loosen, which can ensure the stability and reliability of the handle 12 during use. A washer 20 is provided inside the hexagon socket head cap screw 19. The washer 20 can increase friction and prevent the bolt from loosening. At the same time, it can also protect the surface of the needle plate from being scratched by the bolt, thus extending the service life of the needle plate.

[0045] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A long-life needle plate for ceramic fibers, comprising a needle looper main body (1); A main shaft (2) is arranged at the top of the needle looper main body (1), an eccentric wheel (3) is arranged at the outer side of the main shaft (2), a push rod is arranged at the bottom of the eccentric wheel (3), an upper needle plate (5) is arranged at the bottom of the push rod, a stripping guide plate (7) is arranged at the bottom of the upper needle plate (5), a lower needle plate (9) is arranged at the bottom of the needle looper main body (1), and a force guide plate (8) is arranged above the lower needle plate (9); characterized in that An aluminum-magnesium alloy base plate (16) is arranged at the top of the upper needle plate (5), a high-temperature-resistant fluororubber (17) is arranged above the aluminum-magnesium alloy base plate (16), a nylon plate (18) is arranged above the high-temperature-resistant fluororubber (17), and a spike needle (6) is arranged inside the upper needle plate (5) and the lower needle plate (9).

2. The long-life needle plate for ceramic fiber according to claim 1, characterized by: Arrayed through holes (13) are arranged inside the aluminum-magnesium alloy base plate (16), arrayed high-temperature-resistant fluororubber through holes (21) are arranged inside the high-temperature-resistant fluororubber (17), and arrayed nylon plate through holes (22) are arranged inside the nylon plate (18).

3. A long-life needle plate for ceramic fiber according to claim 2, characterized in that: The diameter of the through holes (13) is consistent with the diameter of the root of the spike needle (6), the high-temperature-resistant fluororubber through holes (21) are slightly smaller than the root of the spike needle (6) by 0.1 mm, and the nylon plate (18) is slightly smaller than the root of the spike needle (6) by 0.1 mm.

4. A long-life needle plate for ceramic fiber according to claim 3, characterized in that: Arrayed counterbores (11) are arranged inside the upper needle plate (5) and the lower needle plate (9), a needle head (23) is arranged at the top of the spike needle (6), and the needle head (23) has an L-shaped structure.

5. A long-life needle plate for ceramic fiber according to claim 4, characterized in that: The cumulative deviation of the through holes (13) is not more than ±0.5 mm, the aperture tolerance of the through holes (13) is ±0.005 mm, and the through holes (13) of the upper needle plate (5) and the lower needle plate (9) are symmetrically distributed.

6. A long-life needle plate for ceramic fiber according to claim 1, characterized in that: An upper needle plate groove (4) is arranged at the outer side of the upper needle plate (5), a lower needle plate groove (10) is arranged at the outer side of the lower needle plate (9), and a clamping groove (26) is arranged at the inner edge of the upper needle plate groove (4) and the lower needle plate groove (10).

7. A long-life needle plate for ceramic fiber according to claim 6, characterized in that: A clamping plate (24) is arranged at the left side of the inner side of the upper needle plate groove (4), a positioning groove (14) is arranged at the left side of the middle of the upper needle plate (5), the positioning groove (14) and the clamping plate (24) are connected in a clamping manner, a positioning pin (15) is arranged at the right side of the inner side of the upper needle plate (5), a positioning hole (25) corresponding to the positioning pin (15) is arranged at the right side of the upper needle plate groove (4), and the same clamping plate (24) and positioning hole (25) are arranged inside the lower needle plate groove (10).

8. The long-life needle plate for ceramic fiber according to claim 1, characterized by: A handle (12) is arranged at the top of the right side of the upper needle plate (5) and the lower needle plate (9), the handle (12) is fixedly connected with the upper needle plate (5) and the lower needle plate (9) through an inner hexagonal bolt (19), and a gasket (20) is arranged at the inner side of the inner hexagonal bolt (19).

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