A multi-stage mixing reaction kettle device

Abstract

The application discloses a multi-stage mixing reaction kettle device and relates to the technical field of reaction kettles.The device comprises a kettle body, a support, a stirring rod and two stirring structures.The support is fixed to the kettle body and is located at the top of the kettle body.The stirring rod is rotatably installed on the support and the kettle body, and the stirring rod is coaxially arranged with the kettle body.A driving assembly for enabling the stirring rod to rotate in opposite directions is arranged on the outer side of the support.Two stirring structures with different heights are arranged on the stirring rod.The stirring structure comprises a plurality of cross rods and a plurality of stirring cylinders corresponding to the cross rods one by one.The stirring cylinder has a whole "Guanyin bottle" shape.A connecting structure is connected to the outer side of the thick end of the stirring cylinder and one end of the corresponding cross rod.The other end of the cross rod is fixed to the stirring rod.The whole stirring structure is simple, which is convenient for maintenance and transportation in the later period, and the stirring structure can realize the cross stirring and improve the mixing efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reaction kettles, in particular to a multi-stage mixing reaction kettle device. BACKGROUND

[0002] As a core equipment in process industry, the function of reaction kettle is to realize the mixing, heat transfer and chemical reaction of materials. The performance of the equipment is directly related to the process efficiency and product quality, therefore, the structural design, especially the design of the stirring system, is crucial.

[0003] For example, the Chinese patent with publication number CN119368135B provides a stirring device with self-cleaning function, which realizes the composite functions of stirring and anti-adhesion through a multi-stage transmission mechanism. However, the complexity of this design also brings practical challenges such as high assembly precision requirement and increased maintenance points, which may affect the long-term operation stability and economy of the equipment.

[0004] On the contrary, the magnetic drive single-shaft stirring scheme adopted by the Chinese patent with authorization announcement number CN113144984B has relatively simple structure and good sealing performance. However, the single stirring flow field is often weak in dealing with harsh process conditions such as high viscosity, heterogeneous phase or strong shear and uniform mixing of the whole kettle, and has inherent defects such as many mixing dead angles and insufficient mass and heat transfer efficiency.

[0005] Therefore, the core contradiction in the current reaction kettle stirring technology field is how to significantly improve the uniformity and efficiency of mixing without excessively increasing the system complexity and maintenance difficulty. It is of great practical significance to develop a compact, reliable and durable stirring device with superior mixing performance. SUMMARY

[0006] The purpose of the present application is to provide a multi-stage mixing reaction kettle device to solve the problems raised in the background art.

[0007] The technical solution of the present application is a multi-stage mixing reaction kettle device, which comprises a kettle body, a support, a stirring rod and two stirring structures. The support is fixed with the kettle body, and the support is located at the top of the kettle body. The stirring rod is rotatably installed on the support and the kettle body, and the stirring rod is coaxially arranged with the kettle body.

[0008] The outer side of the support is provided with a driving assembly for forward and reverse rotation of the stirring rod.

[0009] Two stirring structures with different heights are arranged on the stirring rod, and the stirring structure comprises a plurality of cross rods and a plurality of stirring cylinders corresponding to the plurality of cross rods, the stirring cylinder as a whole is in the shape of an 'observation bottle', the outer side of the thick end of the stirring cylinder is connected with one end of the corresponding cross rod through a connecting structure, the other end of the cross rod is fixed with the stirring rod, the upper stirring cylinders are one-to-one corresponding to the lower stirring cylinders, and the thin end of the upper stirring cylinder is close to the thin end of the corresponding lower stirring cylinder.

[0010] Preferably, the driving assembly comprises a transmission gear, an incomplete gear and a rotating shaft, the transmission gear is coaxially fixed with the stirring rod, the rotating shaft is fixed with the incomplete gear, the central axis of the rotating shaft is coaxially arranged with the center of the incomplete gear, one end of the rotating shaft is rotatably arranged on the support, the transmission gear and the incomplete gear are engaged, and the driving assembly further comprises a reciprocating mechanism for enabling the incomplete gear to reciprocate.

[0011] Preferably, the reciprocating mechanism comprises an extension plate, a shaft disc, a pushing column and a servo motor, the extension plate is an integral structure with the incomplete gear, one end of the extension plate is coaxially arranged with the center of the incomplete gear, a straight groove is formed in the surface of the extension plate, and the pushing column is slidably arranged in the straight groove, the servo motor is fixed with the support, the output shaft of the servo motor is coaxially fixed with the shaft body of the shaft disc, one end of the pushing column is fixed on the circular surface of the shaft disc, and the pushing column is located at a non-center position of the circular surface of the shaft disc.

[0012] Preferably, a plurality of scattering plates are arranged between the two stirring structures, one end of each of the plurality of scattering plates is fixed with the stirring rod, and the plurality of scattering plates are equidistantly and annularly distributed with the central axis of the stirring rod as the center.

[0013] Preferably, one end of each of two oppositely arranged scattering plates is fixed with a U-shaped plate, and the U-shaped plate has an upward U-shaped opening.

[0014] Preferably, the connecting structure comprises a rotating column, a fixed cylinder, an arc block and a limiting plate, one end of the rotating column is fixed with the stirring cylinder, the fixed cylinder is coaxially fixed with the cross rod, the rotating column is rotatably arranged in the fixed cylinder through a sealing bearing, the arc block is arranged in the fixed cylinder and coaxially fixed with the fixed cylinder, and the limiting plate is fixed with the rotating column.

[0015] Preferably, the outer side of the thin end of the stirring cylinder is fixed with a weight ring.

[0016] Preferably, the two ends of the arc block are both fixed with buffer rubber blocks.

[0017] The multi-stage mixing reaction kettle device is provided by improving the prior art, and has the following improvements and advantages compared with the prior art:

[0018] One: the stirring rod of the present application rotates unidirectionally, the fluid in the reaction kettle enters the stirring cylinder through the thick end of the stirring cylinder, diffuses in a turbulent manner after compression and release, improves the mixing efficiency, because the thin end of the upper stirring cylinder is close to the thin end of the lower stirring cylinder, the fluid collides by convection, thereby expanding the mixing degree, so the whole stirring structure is simple and not complex, facilitating the maintenance and transportation in the later stage, and the mixing efficiency is improved;

[0019] Secondly, the present application adopts forward and reverse stirring, which can break the "fixed flow field limitation" of single turning, change the stress direction and flow path of the material, and solve the problems of uneven mixing, material accumulation and low efficiency in single direction stirring, and the reaction material can quickly diffuse from the high concentration area to the low concentration area, the product can timely separate from the reaction interface, and local concentration imbalance is avoided.

[0020] Thirdly, in the environment of forward and reverse stirring, the thick end of the stirring cylinder can change the direction automatically, mainly by means of the weight ring of the thin end of the stirring cylinder, so that the stirring cylinder can automatically rotate according to the rotation direction of the stirring rod, and the stirring cylinder can realize diffusion mixing effect when the stirring rod rotates forward and reversely.

[0021] Fourthly, the upper stirring cylinder of the present application is provided with an inclined thick end inclined upward, and the lower stirring cylinder is provided with an inclined thick end inclined downward, and the stirring rod is provided with a plurality of scattering plates distributed in equidistant annular shape with the central shaft as the center between the two stirring structures, so that the upper and lower stirring cylinders concentrate the fluid at the top and bottom center area of the periphery, and then the fluid is diffused by the scattering plates, the stirring blind area range is reduced, and multi-stage stirring is realized, that is, the two-stage fluid concentration of the upper and lower stirring cylinders plus the third-stage dispersion of the scattering plates, forming a three-stage stirring system with complete spatial hierarchical coverage, clear function cooperation and stable flow field. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present application;

[0024] Figure 2 It is a schematic diagram of the internal structure of the kettle body of the present application;

[0025] Figure 3The three-dimensional structure schematic diagram of the driving assembly of the application is shown in the figure;

[0026] Figure 4 The three-dimensional structure schematic diagram of the stirring rod, stirring structure, scattering plate and U-shaped plate of the application is shown in the figure;

[0027] Figure 5 The three-dimensional structure schematic diagram of the stirring structure of the application is shown in the figure;

[0028] Figure 6 The installation schematic diagram of the stirring cylinder of the application is shown in the figure;

[0029] Figure 7 The working schematic diagram of the stirring cylinder of the application is shown in the figure;

[0030] Figure 8 The internal structure schematic diagram of the lower fixed cylinder of the application is shown in the figure;

[0031] Figure 9 The internal structure schematic diagram of the upper fixed cylinder of the application is shown in the figure;

[0032] Figure 10 The three-dimensional structure schematic diagram of the scattering plate and U-shaped plate of the application is shown in the figure.

[0033] Reference signs:

[0034] 1, kettle body; 2, support; 3, stirring rod; 4, transmission gear; 5, incomplete gear; 6, extension plate; 7, rotating shaft; 8, push column; 9, servo motor; 10, shaft disc; 11, straight groove; 12, scattering plate; 13, U-shaped plate; 14, stirring cylinder; 15, cross rod; 16, rotating column; 17, fixed cylinder; 18, arc block; 19, limiting plate; 20, sealing bearing; 21, buffer rubber block; 22, weight ring. DETAILED DESCRIPTION

[0035] The application will be described in detail below, and the technical solutions in the embodiments of the application will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0036] The application provides a multi-stage mixing reaction kettle device by improvement, and the technical solutions of the application are as follows:

[0037] As Figures 1 to 10As shown, the embodiment of the present application provides a multi-stage mixing reaction kettle device, which comprises a kettle body 1, a support 2, a stirring rod 3 and two stirring structures, the support 2 is fixed with the kettle body 1, and the support 2 is located at the top of the kettle body 1, the stirring rod 3 is rotatably installed on the support 2 and the kettle body 1, and the stirring rod 3 is coaxially arranged with the kettle body 1;

[0038] The outer side of the support 2 is provided with a driving assembly for enabling the stirring rod 3 to perform forward and reverse rotation;

[0039] The stirring rod 3 is provided with two stirring structures with different heights, the stirring structure comprises a plurality of cross rods 15 and a plurality of stirring barrels 14 corresponding to the plurality of cross rods 15, the stirring barrel 14 has a shape of a Guanyin bottle, the outer side of the thick end of the stirring barrel 14 is connected with one end of the corresponding cross rod 15 through a connecting structure, the other end of the cross rod 15 is fixed with the stirring rod 3, the upper stirring barrels 14 are correspondingly arranged with the lower stirring barrels 14, and the thin end of the upper stirring barrel 14 is close to the thin end of the corresponding lower stirring barrel 14.

[0040] It should be noted that the stirring barrel 14 has a shape of a Guanyin bottle, and the stirring barrel 14 has a neck, the diameter of the neck is smaller than the diameter of the thin end, the fluid enters the neck from the thick end of the stirring barrel 14, is compressed, and then flows out from the thin end, so that the pressure is released and the fluid is diffused outward, according to Bernoulli effect, the fluid is in a turbulent flow state at the thin end, and the fluid in the turbulent flow state can improve the mixing degree, the essence of the turbulent flow is that the fluid particles are in irregular and random turbulent motion, which can quickly break the concentration gradient, temperature gradient or phase interface of the material through the intensification of particle diffusion, shear effect and flow field disturbance, thereby greatly improving the mixing uniformity and efficiency.

[0041] It should be further noted that the specific model and specification of the kettle body 1 are determined according to the actual specifications of the device, and the specific selection calculation method adopts the existing technology in the art, so it will not be described in detail.

[0042] It should be further noted that when the rod body rotates unidirectionally, the fluid in the reaction kettle enters the stirring barrel 14 through the thick end of the stirring barrel 14, is compressed and released, so that the fluid is diffused in a turbulent flow state, and the mixing efficiency is improved, because the thin end of the upper stirring barrel 14 is close to the thin end of the lower stirring barrel 14, the fluid will collide and flow, thereby expanding the mixing degree.

[0043] Specifically, the embodiment of the present application is described in combination with the accompanying drawings. Figures 1-3As shown, the driving assembly comprises a transmission gear 4, an incomplete gear 5 and a rotating shaft 7, the transmission gear 4 is coaxially fixed with the stirring rod 3, the rotating shaft 7 is fixed with the incomplete gear 5, the center axis of the rotating shaft 7 is coaxially arranged with the center of the incomplete gear 5, one end of the rotating shaft 7 is rotatably installed on the support 2, the transmission gear 4 and the incomplete gear 5 are engaged, the driving assembly further comprises a reciprocating mechanism for reciprocating the incomplete gear 5; the reciprocating mechanism comprises an extension plate 6, a shaft disc 10, a poking column 8 and a servo motor 9, the extension plate 6 is an integral structure with the incomplete gear 5, one end of the extension plate 6 is coaxially arranged with the center of the incomplete gear 5, a straight groove 11 is formed on the surface of the extension plate 6, and the poking column 8 is slidably arranged in the straight groove 11, the servo motor 9 is fixed with the support 2, the output shaft of the servo motor 9 is coaxially fixed with the shaft body of the shaft disc 10, one end of the poking column 8 is fixed on the circular surface of the shaft disc 10, and the poking column 8 is located at a non-center position of the circular surface of the shaft disc 10;

[0044] It should be noted that the specific model and specification of the servo motor 9 need to be determined according to the actual specifications of the device, and the specific selection calculation method adopts the existing technology in the art, so it will not be described in detail; the power supply and principle of the servo motor 9 are clear to those skilled in the art, and will not be described in detail here;

[0045] It should be further noted that the transmission ratio between the transmission gear 4 and the incomplete gear 5 is determined according to the actual specifications of the device, and the specific selection calculation method adopts the existing technology in the art, so it will not be described in detail;

[0046] It should be further noted that the servo motor 9 rotates the shaft disc 10 through the transmission shaft, the shaft disc 10 makes the poking column 8 at the non-center position reciprocate along the straight groove 11 of the extension plate 6, so that one end of the extension plate 6 reciprocates around one end of the rotating shaft 7, since the extension plate 6 is fixed with the incomplete gear 5, and since the center of the incomplete gear 5 is coaxially arranged with the center of the rotating shaft 7, the incomplete gear 5 reciprocates, the incomplete gear 5 makes the transmission gear 4 engaged with it reciprocate, and the transmission gear 4 drives the stirring rod 3 fixed therewith to reciprocate.

[0047] Specifically, a plurality of scattering plates 12 are arranged between the two stirring structures, one end of each of the plurality of scattering plates 12 is fixed with the stirring rod 3, and the plurality of scattering plates 12 are distributed in an equidistant ring shape with the center axis of the stirring rod 3 as the center;

[0048] It needs to be explained that the upper stirring barrel 14 is arranged obliquely upward, and the lower stirring barrel 14 is arranged obliquely downward, and the stirring rod 3 is provided with a plurality of scattering plates 12 which are equidistantly and annularly distributed with the central shaft as the center in the middle of the two stirring structures, so that the upper and lower stirring barrels 14 can concentrate the fluid at the top and the bottom center area of the periphery, and then the fluid is diffused by the scattering plates 12, the stirring blind area range is reduced, and multi-stage stirring is realized, that is, two-stage fluid concentration of the upper and lower stirring barrels 14 plus three-stage dispersion of the scattering plates 12, forming a three-stage stirring system which has complete spatial level coverage, clear function cooperation and stable flow field continuity.

[0049] Specifically, combined with the accompanying drawings, Figure 10 As shown in the figure, one end of the two opposite scattering plates 12 is fixed with a U-shaped plate 13, and the U-shaped plate 13 has an upward U-shaped opening.

[0050] It needs to be explained that the U-shaped plate 13 is arranged to stir the fluid at the periphery and the bottom, and to expand the stirring range.

[0051] Specifically, combined with the accompanying drawings, Figures 5-9 As shown in the figure, the connecting structure includes a rotating column 16, a fixed cylinder 17, a circular block 18 and a limiting plate 19, one end of the rotating column 16 is fixed with the stirring barrel 14, the fixed cylinder 17 is coaxially fixed with the horizontal rod 15, the rotating column 16 is rotatably installed in the fixed cylinder 17 through a sealing bearing 20, the circular block 18 is located in the fixed cylinder 17, and the circular block 18 is coaxially fixed with the fixed cylinder 17, the limiting plate 19 is fixed with the rotating column 16, the thin end of the stirring barrel 14 is fixed with a weight ring 22, and both ends of the circular block 18 are fixed with a buffer rubber block 21.

[0052] It needs to be explained that the specific type and specification of the sealing bearing 20 need to be determined according to the actual specification of the device, and the specific selection calculation method adopts the existing technology in the art, so it will not be described in detail;

[0053] It needs to be further explained that the buffer rubber block 21 is arc-shaped and coaxially arranged with the circular block 18, and the fan angle of the circular arc composed of the circular block 18 and the buffer rubber blocks 21 at both ends is greater than two hundred degrees.

[0054] It needs to be further explained that when the stirring rod 3 reciprocating rotates, the thin end of the stirring cylinder 14 changes position by means of the eccentric weight ring 22. For example, when the stirring rod 3 rotates forward (the clockwise direction can be set as positive), the eccentric weight ring 22 will pull the stirring cylinder 14 due to inertia, so that the stirring cylinder 14 rotates, enabling the flow to enter from the thick end of the stirring cylinder 14. Therefore, in the forward and reverse stirring environment, the thick end of the stirring cylinder 14 can complete self-adaptive direction change, mainly by means of the eccentric weight ring 22 of the thin end of the stirring cylinder 14. When the stirring cylinder 14 can automatically rotate according to the rotation direction of the stirring rod 3, ensuring that the stirring cylinder 14 can rotate forward and backward with the stirring rod 3, the stirring cylinder 14 can realize diffusion mixing effect.

[0055] Working principle: the servo motor 9 drives the shafted disc 10 to rotate through the transmission shaft, the shafted disc 10 drives the push column 8 at the non-circular center to reciprocating slide along the straight groove 11 of the extension plate 6, so that one end of the extension plate 6 reciprocating swings around one end of the rotating shaft 7. Since the extension plate 6 is fixed with the incomplete gear 5, and the center of the incomplete gear 5 is coaxially arranged with the center of the rotating shaft 7, the incomplete gear 5 swings, and the incomplete gear 5 drives the transmission gear 4 engaged therewith to reciprocating rotate, and the transmission gear 4 drives the stirring rod 3 fixed therewith to reciprocating rotate.

[0056] When the stirring rod 3 reciprocating rotates, the thin end of the stirring cylinder 14 changes position by means of the eccentric weight ring 22. For example, when the stirring rod 3 rotates forward (the clockwise direction can be set as positive), the eccentric weight ring 22 will pull the stirring cylinder 14 due to inertia, so that the stirring cylinder 14 rotates, enabling the flow to enter from the thick end of the stirring cylinder 14. Therefore, in the forward and reverse stirring environment, the thick end of the stirring cylinder 14 can complete self-adaptive direction change, mainly by means of the eccentric weight ring 22 of the thin end of the stirring cylinder 14. When the stirring cylinder 14 can automatically rotate according to the rotation direction of the stirring rod 3, ensuring that the stirring cylinder 14 can rotate forward and backward with the stirring rod 3, the stirring cylinder 14 can realize diffusion mixing effect.

[0057] When the rod body rotates unidirectionally, the fluid in the reaction kettle enters the stirring cylinder 14 through the thick end of the stirring cylinder 14, and is diffused in a turbulent flow state after compression and release, thereby improving the mixing efficiency. Because the thin end of the upper stirring cylinder 14 is close to the thin end of the lower stirring cylinder 14, the fluid will collide and flow, thereby expanding the mixing degree.

[0058] The upper stirring barrel 14 is inclined upward at the thick end, and the lower stirring barrel 14 is inclined downward at the thick end, and the stirring rod 3 is provided with a plurality of scattering plates 12 which are equidistantly distributed in a ring shape with the central shaft as the center between the two stirring structures, so that the upper and lower stirring barrels 14 can concentrate the fluid at the top and the bottom center area of the periphery, and then the fluid is diffused by the scattering plates 12, the stirring blind area range is reduced, and multi-stage stirring is realized, that is, two-stage fluid concentration of the upper and lower stirring barrels 14 plus three-stage dispersion of the scattering plates 12, forming a three-stage stirring system with complete spatial level coverage, clear function cooperation and stable flow field continuity; the U-shaped plate 13 is arranged to stir the fluid at the periphery and the bottom and expand the stirring range.

[0059] The above description enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Accordingly, the present application is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-stage mixing reactor device, comprising a reactor body (1), a support (2), a stirring rod (3), and two stirring structures, characterized in that: The bracket (2) is fixed to the vessel body (1) and the bracket (2) is located at the top of the vessel body (1). The stirring rod (3) is rotatably mounted on the bracket (2) and the vessel body (1). The stirring rod (3) is coaxially arranged with the vessel body (1). A drive assembly for the stirring rod (3) to rotate forward and backward is provided on the outside of the bracket (2). Two stirring structures with different heights are provided on the stirring rod (3). The stirring structure includes multiple crossbars (15) and multiple stirring cylinders (14) corresponding to the multiple crossbars (15). The stirring cylinder (14) is shaped like a "Guanyin bottle". The outer side of the thick end of the stirring cylinder (14) is connected to one end of the corresponding crossbar (15) by a connecting structure. The other end of the crossbar (15) is fixed to the stirring rod (3). The multiple stirring cylinders (14) located above correspond to the multiple stirring cylinders (14) located below. The thin end of the upper stirring cylinder (14) is close to the thin end of its corresponding lower stirring cylinder (14). The connection structure includes a rotating column (16), a fixed cylinder (17), an arc block (18), and a limiting plate (19). One end of the rotating column (16) is fixed to the stirring cylinder (14). The fixed cylinder (17) is coaxially fixed to the crossbar (15). The rotating column (16) is rotatably installed inside the fixed cylinder (17) through a sealed bearing (20). The arc block (18) is located inside the fixed cylinder (17) and is coaxially fixed to the fixed cylinder (17). The limiting plate (19) is fixed to the rotating column (16). A weighted ring (22) is fixed to the outer side of the narrow end of the stirring cylinder (14); buffer rubber blocks (21) are fixed to both ends of the arc block (18).

2. The multi-stage mixing reactor apparatus according to claim 1, characterized in that: The drive assembly includes a transmission gear (4), an incomplete gear (5), and a rotating shaft (7). The transmission gear (4) is coaxially fixed with the stirring rod (3). The rotating shaft (7) is fixed with the incomplete gear (5). The central axis of the rotating shaft (7) is coaxially set with the center of the incomplete gear (5). One end of the rotating shaft (7) is rotatably mounted on the bracket (2). The transmission gear (4) and the incomplete gear (5) mesh with each other. The drive assembly also includes a reciprocating mechanism that causes the incomplete gear (5) to reciprocate.

3. The multi-stage mixing reactor apparatus according to claim 2, characterized in that: The reciprocating mechanism includes an extension plate (6), a shafted disc (10), a toggle post (8), and a servo motor (9). The extension plate (6) and the incomplete gear (5) are an integral structure. One end of the extension plate (6) is coaxially arranged with the center of the incomplete gear (5). A straight groove (11) is opened on the surface of the extension plate (6), and the toggle post (8) is slidably arranged in the straight groove (11). The servo motor (9) is fixed to the bracket (2). The output shaft of the servo motor (9) is coaxially fixed with the shaft of the shafted disc (10). One end of the toggle post (8) is fixed on the circular surface of the shafted disc (10), and the toggle post (8) is located at a non-center position on the circular surface of the shafted disc (10).

4. The multi-stage mixing reactor apparatus according to claim 1, characterized in that: Multiple dispersing plates (12) are provided between the two stirring structures. One end of each of the multiple dispersing plates (12) is fixed to the stirring rod (3), and the multiple dispersing plates (12) are distributed in a ring at equal distances with the central axis of the stirring rod (3) as the center.

5. The multi-stage mixing reactor apparatus according to claim 4, characterized in that: One end of each of the two opposing dispersing plates (12) is fixed with a U-shaped plate (13), with the U-shaped opening of the U-shaped plate (13) facing upwards.

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