Anti-interference device of radar liquid level meter

Abstract

The invention relates to the technical field of radar liquid level meters, in particular to an anti-interference device of a radar liquid level meter, which comprises a transmitter, a flange mounted at the bottom of the transmitter, an antenna housing mounted on the lower surface of the flange, a conical barrel mounted at the lower end of the antenna housing, and a conical rubber sleeve sleeved on the conical barrel. A connecting pipe is installed on the outer surface of the conical barrel, an air cylinder communicated with the connecting pipe is installed at the end, away from the conical barrel, of the connecting pipe, a detachable barrel cover is installed at the open end of the air cylinder, a screw hole is formed in the middle of one face of the barrel cover, and a screw is in threaded connection with the interior of the screw hole. A piston is rotatably mounted at the end, located in the air cylinder, of the screw rod, a rotary knob head is mounted at the end, away from the piston, of the screw rod, and the air cylinder is connected with the flange through a connecting piece. And online cleaning of attachments interfering the measurement precision of the radar liquid level meter is realized.

Description

Technical Field

[0001] The present invention is an anti-interference device for a radar level gauge, belonging to the field of radar level gauges. Background Art

[0002] A radar level gauge is a general-purpose measuring instrument that uses the time-of-flight principle to measure the liquid level. Specifically, the radar waves emitted by the radar level gauge propagate at the speed of light. When these radar waves encounter the liquid surface, they are reflected back. By measuring the time difference between the emission and reception of the radar waves by electronic components, the height of the liquid level can be calculated. This time difference is converted into a corresponding level signal, thereby achieving accurate liquid level measurement. During use, the liquid is likely to splash onto the surface of the antenna of the radar level gauge, resulting in interference from the attachments on the antenna surface and affecting the overall measurement accuracy. Since the antenna part in the radar level gauge is inside the tank, it is time-consuming and laborious to deal with the attachments on the antenna part of the radar level gauge. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an anti-interference device for a radar level gauge to solve the problems proposed in the above background art.

[0004] To achieve the above purpose, the present invention is realized through the following technical solutions: An anti-interference device for a radar level gauge includes a transmitter. A flange is installed at the bottom of the transmitter. An antenna cover is installed on the lower surface of the flange. A conical cylinder with a narrow upper part and a wide lower part is installed at the lower end of the antenna cover. A conical rubber sleeve is sleeved on the conical cylinder. The upper end of the conical rubber sleeve is fixedly connected to the upper end of the conical cylinder. The lower end of the conical rubber sleeve is fixedly connected to an umbrella-shaped rubber sleeve. The upper end of the umbrella-shaped rubber sleeve is a tip and the umbrella-shaped rubber sleeve is arranged inside the conical cylinder. A connecting pipe is installed on the outer surface of the conical cylinder. One end of the connecting pipe away from the conical cylinder penetrates through the flange and extends to the upper side of the flange. A gas cylinder communicated with the connecting pipe is installed at the end of the connecting pipe away from the conical cylinder. The end of the gas cylinder away from the connecting pipe is open. A detachable cylinder cover is installed at the open end of the gas cylinder. A screw hole is opened in the middle position of one side of the cylinder cover. A screw rod is threadedly connected in the screw hole. A piston is rotatably installed at one end of the screw rod inside the gas cylinder. The piston is slidably installed inside the gas cylinder. A knob head is installed at the end of the screw rod away from the piston. The gas cylinder is connected to the flange through a connecting piece.

[0005] Specifically, the connecting piece includes a ring, a connecting ring which is connected and fixed to the gas cylinder is sleeved on the open end of the gas cylinder, a ring is arranged between the connecting ring and the cylinder cover, a plurality of middle holes are opened in a ring shape and equidistantly on one side of the ring, a plurality of first circular holes which are opened in a ring shape and equidistantly on one side of the connecting ring and are aligned with the middle holes, a plurality of second circular holes which are opened in a ring shape and equidistantly on one side of the cylinder cover and are aligned with the middle holes, a connecting screw is inserted in the channel formed by the second circular hole, the middle hole and the first circular hole, a nut is threadedly connected to one end of the connecting screw, the nut is arranged on the side of the first circular hole away from the middle hole, a support plate is installed at the lower position of the outer surface of the ring, a bottom plate is connected and fixed to the lower end of the support plate, and the bottom plate is connected to the flange by a plurality of positioning screws.

[0006] Specifically, a plurality of vertical holes are evenly formed on the upper surface of the base plate, a slot is formed on the annular side surface of the flange, a plurality of through holes aligned with the vertical holes are formed on the top of the slot, an insert block is inserted in the slot, an arc-shaped surface is processed on one end of the insert block, and the arc-shaped surface has the same curvature as the annular side surface of the flange, a plurality of threaded blind holes evenly formed on the upper surface of the insert block aligned with the through holes, and one end of the positioning screw passes through the vertical hole and the through hole in sequence and is threadedly connected in the threaded blind hole.

[0007] Specifically, a support plate is connected and fixed to the side of the piston facing the screw, a positioning sleeve is connected and fixed to the side of the support plate facing the screw, the end of the positioning sleeve close to the support plate is open, and a circular opening is formed on the side of the positioning sleeve facing away from the support plate, the end of the screw away from the knob head passes through the circular opening and is connected and fixed to a disc head, and the disc head is slidably installed in the space formed by the positioning sleeve and the support plate.

[0008] Specifically, the conical tube is sleeved with an upper ring connected and fixed to the conical tube, the upper end of the conical rubber sleeve is sleeved with a rubber ring connected and fixed to the conical rubber sleeve, the rubber ring fits with the upper ring, and the rubber ring is adhered to the upper ring by glue.

[0009] Specifically, a plurality of protrusions are evenly fixed on the upper surface of the rubber ring, the protrusions and the rubber ring are an integrally formed structure, a plurality of positioning holes are equidistantly opened in an annular shape on the upper surface of the upper ring, and the protrusions are glued into the positioning holes by glue.

[0010] Specifically, a top cover is provided at the upper end of the transmitter, two ears are connected and fixed to the outer surface of the top cover, a protrusion is provided at the lower side of the ear, the protrusion is fixed on the surface of the transmitter, and the ear is connected to the protrusion by screws.

[0011] Specifically, a through hole is provided on the upper surface of the flange, the connecting pipe passes through the through hole, the inner diameter of the through hole is the same as the outer diameter of the connecting pipe, and a plurality of fixing holes are provided in an annular shape and at equal intervals on the upper surface of the flange.

[0012] Beneficial effects of the present invention: 1. Use the knob head to turn the screw so that the screw drives the piston to slide in the air cylinder, so that the piston squeezes the air in the air cylinder through the connecting pipe into the space formed by the conical rubber sleeve, the umbrella-shaped rubber sleeve, the conical cylinder and the antenna cover. At this time, the umbrella-shaped rubber sleeve moves out of the conical cylinder, and the surface tension of the outer surface of the umbrella-shaped rubber sleeve increases, so that the attachments attached to the outer surface of the umbrella-shaped rubber sleeve fall off the umbrella-shaped rubber sleeve. There is no need to remove the antenna cover from the tank body and process it by disassembly, so as to realize online cleaning of attachments that interfere with the measurement accuracy of the radar level meter. Turn the screw in the opposite direction so that the air flows back into the air cylinder, and the umbrella-shaped rubber sleeve returns to its original position and is in the conical cylinder.

[0013] 2. When using connecting screws to install the cylinder cover and the gas cylinder, a ring is set between the cylinder cover and the connecting ring, and then the connecting screws are passed through the cylinder cover, the ring and the connecting ring in sequence and then the nuts are screwed on, so that the fasteners formed by the connecting screws and the nuts can limit the relative position of the ring and the gas cylinder while limiting the relative position of the cylinder cover and the gas cylinder. The base plate is installed on the flange using positioning screws, so that the base plate, the support plate and the ring jointly support the gas cylinder, which is conducive to using other connecting screws alone to limit the relative position of the ring and the gas cylinder, thereby reducing the use of fasteners.

[0014] 3. When installing the positioning screws, insert the plug with a threaded blind hole into the slot on the flange, and then pass the positioning screw through the vertical hole and the through hole and screw it into the threaded blind hole to complete the connection between the base plate and the flange. When the threaded blind hole is damaged, remove the plug from the slot and replace it separately without replacing the flange and other parts, thereby reducing the replacement cost of parts.

[0015] 4. In the process of bonding the rubber ring and the upper circular ring, the convex head is glued in the positioning hole by glue, which increases the connection range between the rubber ring and the upper circular ring. The rubber ring and the upper circular ring cooperate with each other to increase the connection area between the conical rubber sleeve and the conical cylinder, that is, to improve the stability of the installation of the conical rubber sleeve. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a structural schematic diagram of an anti-interference device of a radar level gauge of the present invention; Figure 2 for Figure 1 Enlarged view of point A in the middle; Figure 3 A perspective stereogram of an anti-interference device of a radar level gauge according to the present invention; Figure 4Another perspective three-dimensional view of the anti-interference device for a radar level gauge of the present invention; Figure 5 Assembly schematic diagram of the conical rubber sleeve, radome, transmitter and flange in the anti-interference device for a radar level gauge of the present invention; Figure 6 Assembly schematic diagram of the support plate, screw rod and air cylinder in the anti-interference device for a radar level gauge of the present invention; Figure 7 Cross-sectional assembly schematic diagram of the piston, screw rod and air cylinder in the anti-interference device for a radar level gauge of the present invention; Figure 8 Assembly schematic diagram of the knob head, disc head and screw rod in the anti-interference device for a radar level gauge of the present invention; Figure 9 Assembly schematic diagram of the bottom plate, support plate and ring in the anti-interference device for a radar level gauge of the present invention; Figure 10 Three-dimensional view of the insert block in the anti-interference device for a radar level gauge of the present invention; In the figure: 1. Transmitter, 2. Top cover, 3. Screw, 4. Support ear, 5. Convex block, 6. Flange, 7. Radome, 8. Conical cylinder, 9. Upper ring, 10. Rubber ring, 11. Conical rubber sleeve, 12. Connecting pipe, 13. Air cylinder, 14. Nut, 15. Connecting ring, 16. Cylinder cover, 17. Screw rod, 18. Knob head, 19. Connecting screw, 20. Ring, 21. Positioning screw, 22. Bottom plate, 23. Support plate, 24. Insert block, 25. Umbrella-shaped rubber sleeve, 26. Slot, 27. Support plate, 28. Positioning sleeve, 29. Piston, 30. Disc head, 31. Vertical hole, 32. Arc surface, 33. Threaded blind hole. Detailed implementation manners

[0017] To make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific implementation manners.

[0018] Please refer to Figure 1 , the present invention provides a technical solution: an anti-interference device for a radar level gauge, including a transmitter 1, a flange 6 is installed at the bottom of the transmitter 1, a plurality of fixing holes are equidistantly arranged in a ring shape on the upper surface of the flange 6, and the flange 6 is installed on the top of the tank body by using the fixing holes, thus completing the installation of the transmitter 1 on the top of the tank body. A top cover 2 is provided at the upper end of the transmitter 1, two support ears 4 are fixedly connected to the outer surface of the top cover 2, a convex block 5 is provided below the support ear 4, and the convex block 5 is fixed on the surface of the transmitter 1, so that the support ear 4 is connected to the convex block 5 through a screw 3, completing the assembly of the top cover 2 and the transmitter 1.

[0019] Refer to Figure 1 , Figures 3 - 5, an antenna cover 7 is installed on the lower surface of the flange 6, a conical cylinder 8 with a narrow upper end and a wide lower end is installed at the lower end of the antenna cover 7, a conical rubber sleeve 11 is sleeved on the conical cylinder 8, the upper end of the conical rubber sleeve 11 is fixedly connected to the upper end of the conical cylinder 8, an upper ring 9 fixedly connected to the conical cylinder 8 is sleeved on the conical cylinder 8, a rubber ring 10 fixedly connected to the conical rubber sleeve 11 is sleeved on the upper end of the conical rubber sleeve 11, the rubber ring 10 is in fit with the upper ring 9, the rubber ring 10 is adhesively connected to the upper ring 9 by glue, a plurality of convex heads are uniformly fixed on the upper surface of the rubber ring 10, the convex heads and the rubber ring 10 are of an integrally formed structure, a plurality of positioning holes are formed in the upper surface of the upper ring 9 at equal intervals in a circular shape, the convex heads are adhesively pasted in the positioning holes, when the rubber ring 10 and the upper ring 9 are adhesively connected to each other, the convex heads are adhesively pasted in the positioning holes, increasing the connection range between the rubber ring 10 and the upper ring 9, the rubber ring 10 and the upper ring 9 cooperate with each other, increasing the connection area between the conical rubber sleeve 11 and the conical cylinder 8, that is, improving the installation stability of the conical rubber sleeve 11.

[0020] Refer to Figure 1 , Figures 3 - 5 , the lower end of the conical rubber sleeve 11 is fixedly connected to an umbrella-shaped rubber sleeve 25, the upper end of the umbrella-shaped rubber sleeve 25 is a tip and the umbrella-shaped rubber sleeve 25 is arranged inside the conical cylinder 8, a connecting pipe 12 is installed on the outer surface of the conical cylinder 8, one end of the connecting pipe 12 away from the conical cylinder 8 penetrates through the flange 6 and extends to the upper side of the flange 6, wherein a through hole is formed in the upper surface of the flange 6, the connecting pipe 12 penetrates through the through hole, the inner diameter of the through hole is the same as the outer diameter of the connecting pipe 12, and the through hole provides space for the installation of the connecting pipe 12.

[0021] Refer to Figures 1 - 8, at one end of the connecting pipe 12 far from the conical cylinder 8, an air cylinder 13 communicated with the connecting pipe 12 is installed. One end of the air cylinder 13 far from the connecting pipe 12 is open. A detachable cylinder cover 16 is installed at the open end of the air cylinder 13. A screw hole is opened in the middle position of one side of the cylinder cover 16. A screw rod 17 is threadedly connected in the screw hole. One end of the screw rod 17 located inside the air cylinder 13 is rotatably installed with a piston 29. Wherein, on the side of the piston 29 facing the screw rod 17, a support disc 27 is fixedly connected. On the side of the support disc 27 facing the screw rod 17, a positioning sleeve 28 is fixedly connected. One end of the positioning sleeve 28 close to the support disc 27 is open. On the side of the positioning sleeve 28 facing away from the support disc 27, a round hole is opened. One end of the screw rod 17 far from the knob head 18 penetrates through the round hole and is fixedly connected with a disc head 30. The disc head 30 is slidably installed in the space formed by the positioning sleeve 28 and the support disc 27. When the screw rod 17 is rotated, the screw rod 17 drives the disc head 30 to rotate in the space formed by the positioning sleeve 28 and the support disc 27. The piston 29 is slidably installed in the air cylinder 13. One end of the screw rod 17 far from the piston 29 is installed with a knob head 18. By using the knob head 18 to rotate the screw rod 17, the screw rod 17 drives the piston 29 to slide in the air cylinder 13. Thus, the piston 29 squeezes the air in the air cylinder 13 through the connecting pipe 12 into the space formed by the conical rubber sleeve 11, the umbrella-shaped rubber sleeve 25, the conical cylinder 8 and the radome 7. At this time, the umbrella-shaped rubber sleeve 25 moves out of the conical cylinder 8. Furthermore, the surface tension on the outer surface of the umbrella-shaped rubber sleeve 25 increases, so that the attachments adhering to the outer surface of the umbrella-shaped rubber sleeve 25 fall off from the umbrella-shaped rubber sleeve 25. There is no need to take out the radome 7 from the tank body and process it by disassembling. It realizes the on-line cleaning of the attachments interfering with the measurement accuracy of the radar level gauge. By reversely screwing the screw rod 17, the air flows back into the air cylinder 13, and the umbrella-shaped rubber sleeve 25 returns to its original position and is inside the conical cylinder 8.

[0022] Refer to Figure 1 , Figure 2 , Figures 5 - 9, a connecting ring 15 is sleeved on the open end of the air cylinder 13 and is fixedly connected to the air cylinder 13. A ring 20 is provided between the connecting ring 15 and the cylinder cover 16. A plurality of intermediate holes are arranged at equal intervals in a ring shape on one side of the ring 20. A plurality of first round holes aligned with the intermediate holes are arranged at equal intervals in a ring shape on one side of the connecting ring 15. A plurality of second round holes aligned with the intermediate holes are arranged at equal intervals in a ring shape on one side of the cylinder cover 16. A connecting screw 19 is inserted into the channel formed by the second round hole, the intermediate hole and the first round hole. One end of the connecting screw 19 is threadedly connected with a nut 14. The nut 14 is arranged on the side of the first round hole away from the intermediate hole. A support plate 23 is installed at the lower position of the outer surface of the ring 20. The lower end of the support plate 23 is fixedly connected with a bottom plate 22. The bottom plate 22 is connected to the flange 6 through a plurality of positioning screws 21. When installing the cylinder cover 16 and the air cylinder 13 by using the connecting screw 19, the ring 20 is arranged between the cylinder cover 16 and the connecting ring 15, and then the connecting screw 19 is sequentially passed through the cylinder cover 16, the ring 20 and the connecting ring 15 and then the nut 14 is screwed on, so as to realize that the fastener formed by the connecting screw 19 and the nut 14 restricts the relative position of the ring 20 and the air cylinder 13 while restricting the relative position of the cylinder cover 16 and the air cylinder 13. The bottom plate 22 is installed on the flange 6 by using the positioning screws 21. Thus, the bottom plate 22, the support plate 23 and the ring 20 jointly realize the support of the air cylinder 13, which is beneficial to separately use other connecting screws 19 to restrict the relative position of the ring 20 and the air cylinder 13 and reduce the usage amount of fasteners.

[0023] Refer to Figures 1 - 5 , Figures 9 - 10 , a plurality of vertical holes 31 are uniformly opened on the upper surface of the bottom plate 22. A slot 26 is opened on the annular side surface of the flange 6. A plurality of through holes aligned with the vertical holes 31 are opened at the top in the slot 26. A plug 24 is inserted into the slot 26. An arc surface 32 is processed at one end of the plug 24. The arc surface 32 has the same radian as the annular side surface of the flange 6. A plurality of threaded blind holes 33 aligned with the through holes are uniformly opened on the upper surface of the plug 24. One end of the positioning screw 21 sequentially passes through the vertical hole 31 and the through hole and is threadedly connected in the threaded blind hole 33. When installing the positioning screw 21, the plug 24 processed with the threaded blind hole 33 is inserted into the slot 26 on the flange 6, and then the positioning screw 21 passes through the vertical hole 31 and the through hole and is screwed into the threaded blind hole 33 to complete the connection between the bottom plate 22 and the flange 6. When the threaded blind hole 33 is damaged, the plug 24 can be taken out of the slot 26 and replaced separately without replacing components such as the flange 6, reducing the replacement cost of parts.

[0024] Although this specification is described according to the embodiments, not each embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An anti-interference device for a radar level meter, comprising a transmitter (1), characterized in that: The transmitter (1) has a flange (6) installed at the bottom, an antenna cover (7) installed on the lower surface of the flange (6), a tapered tube (8) narrow at the top and wide at the bottom installed at the lower end of the antenna cover (7), a tapered rubber sleeve (11) sleeved on the tapered tube (8), the upper end of the tapered rubber sleeve (11) is connected and fixed to the upper end of the tapered tube (8), an umbrella-shaped rubber sleeve (25) is connected and fixed to the lower end of the tapered rubber sleeve (11), the upper end of the umbrella-shaped rubber sleeve (25) is pointed and the umbrella-shaped rubber sleeve (25) is arranged in the tapered tube (8), a connecting pipe (12) is installed on the outer surface of the tapered tube (8), and the end of the connecting pipe (12) away from the tapered tube (8) passes through the flange (6) and extends to the flange (6) On the side, an air cylinder (13) connected to the connecting pipe (12) is installed at one end of the connecting pipe (12) away from the conical cylinder (8); the end of the air cylinder (13) away from the connecting pipe (12) is open; a detachable cylinder cover (16) is installed at the open end of the air cylinder (13); a screw hole is opened at the middle position of one side of the cylinder cover (16); a screw rod (17) is threadedly connected in the screw hole; a piston (29) is rotatably installed at one end of the screw rod (17) in the air cylinder (13); the piston (29) is slidably installed in the air cylinder (13); a knob head (18) is installed at one end of the screw rod (17) away from the piston (29); and the air cylinder (13) is connected to the flange (6) via a connecting piece.

2. The anti-interference device of a radar level gauge according to claim 1, characterized in that: The connecting member comprises a ring (20), the open end of the gas cylinder (13) is sleeved with a connecting ring (15) connected and fixed to the gas cylinder (13), the ring (20) is arranged between the connecting ring (15) and the cylinder cover (16), one side of the ring (20) is provided with a plurality of middle holes in a circular shape and equidistantly, one side of the connecting ring (15) is provided with a plurality of first circular holes in a circular shape and equidistantly aligned with the middle holes, one side of the cylinder cover (16) is provided with a plurality of second circular holes in a circular shape and equidistantly aligned with the middle holes, a connecting screw (19) is inserted into a channel formed by the second circular holes, the middle holes and the first circular holes, one end of the connecting screw (19) is threadedly connected with a nut (14), the nut (14) is arranged on a side of the first circular hole away from the middle hole, a support plate (23) is installed at a lower position of the outer surface of the ring (20), the lower end of the support plate (23) is connected and fixed with a bottom plate (22), and the bottom plate (22) is connected to the flange (6) via a plurality of positioning screws (21).

3. The anti-interference device of a radar level gauge according to claim 2, characterized in that: A plurality of vertical holes (31) are evenly formed on the upper surface of the bottom plate (22); a slot (26) is formed on the annular side surface of the flange (6); a plurality of through holes aligned with the vertical holes (31) are formed on the top of the slot (26); an insert block (24) is inserted in the slot (26); an arcuate surface (32) is machined on one end of the insert block (24); the arcuate surface (32) has the same arc as the annular side surface of the flange (6); a plurality of threaded blind holes (33) are evenly formed on the upper surface of the insert block (24) aligned with the through holes; one end of the positioning screw (21) passes through the vertical hole (31) and the through hole in sequence and is then threadedly connected to the threaded blind hole (33).

4. The anti-interference device of a radar level gauge according to claim 1, characterized in that: A support plate (27) is connected and fixed to a side of the piston (29) facing the screw rod (17); a positioning sleeve (28) is connected and fixed to a side of the support plate (27) facing the screw rod (17); an end of the positioning sleeve (28) close to the support plate (27) is open; a side of the positioning sleeve (28) facing away from the support plate (27) is provided with a circular opening; an end of the screw rod (17) away from the knob head (18) passes through the circular opening and is connected and fixed to a disc head (30); the disc head (30) is slidably mounted in a space formed by the positioning sleeve (28) and the support plate (27).

5. The anti-interference device of a radar level gauge according to claim 1, characterized in that: The conical cylinder (8) is sleeved with an upper circular ring (9) connected and fixed to the conical cylinder (8); the upper end of the conical rubber sleeve (11) is sleeved with a rubber ring (10) connected and fixed to the conical rubber sleeve (11); the rubber ring (10) is fitted with the upper circular ring (9); and the rubber ring (10) is adhered to the upper circular ring (9) by glue.

6. The anti-interference device of a radar level gauge according to claim 5, characterized in that: A plurality of protrusions are evenly fixed on the upper surface of the rubber ring (10), the protrusions and the rubber ring (10) are an integrally formed structure, a plurality of positioning holes are equidistantly formed in an annular shape on the upper surface of the upper circular ring (9), and the protrusions are glued into the positioning holes by glue.

7. The anti-interference device of a radar level gauge according to claim 1, characterized in that: The transmitter (1) is provided with a top cover (2) at the upper end, and two ears (4) are connected and fixed to the outer surface of the top cover (2). A protrusion (5) is provided on the lower side of the ear (4), and the protrusion (5) is fixed on the surface of the transmitter (1). The ear (4) is connected to the protrusion (5) by means of screws (3).

8. The anti-interference device of a radar level gauge according to claim 1, characterized in that: The upper surface of the flange (6) is provided with a through hole, the connecting pipe (12) passes through the through hole, the inner diameter of the through hole is the same as the outer diameter of the connecting pipe (12), and the upper surface of the flange (6) is provided with a plurality of fixing holes at equal intervals in a circular shape.

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