Filter screen type permanent magnet submersible pump water inlet structure

Abstract

The application relates to the technical field of submersible pumps, and discloses a filter screen type permanent-magnet submersible pump water inlet structure which comprises a main body and a water inlet component at the output end of the main body, and the water inlet component comprises: end cover one and end cover two, the upper and lower axes of which coincide, and a supporting frame is arranged between the two; a filter layer, the upper and lower ends of which are respectively clamped with the end cover one and the end cover two, the filter layer is formed into a ring shape by being connected with a plurality of foldable sections, a group of the foldable sections are in a folded state by default, when one of the foldable sections is folded, the remaining sections are stretched into a fixed state, and particles at the folded section are extruded outwards. The slice one and the slice two are extruded and attached to each other, the filter holes of the two are misaligned, the filter holes form extrusion force from inside to outside, the particles are pushed out of the filter holes, the particles are prevented from entering the pump body, the filter holes are prevented from being forcibly extruded and enlarged, the pump body is prevented from being damaged by the particles, the service life of the submersible pump is prolonged, even if the particles are not completely extruded, the inner end of the filter hole after being folded is blocked, and manual cleaning is facilitated.

Description

Technical Field

[0001] This invention relates to the field of submersible pump technology, specifically to a filter-type permanent magnet submersible pump inlet structure. Background Technology

[0002] Submersible pumps typically require the installation of a filter screen at the water inlet. The filter screen plays a crucial role, primarily protecting the impeller and internal structure by filtering out impurities.

[0003] Submersible pumps operate in environments containing particulate matter, especially when pumping water from the bottom of wells, riverbeds, and ponds. Therefore, a filter acts as a barrier, preventing these particles from being drawn into the pump. Particles smaller than the filter can enter the pump, causing some wear, but this wear is not acute and does not pose a significant threat in the short term. However, large particles entering the pump can cause sudden damage. These particles can collide with the high-speed rotating impeller blades, potentially causing blade breakage, deformation, and loss of balance. Therefore, large particles need to be blocked by the filter. However, the size of particles is not uniform, and there is a possibility of filter clogging, leading to a sudden drop in flow rate and motor overheating and burnout.

[0004] Based on this, when particles with similar mesh size to the filter screen get stuck on the screen, they need to be cleaned regularly. However, currently, for convenience and speed, the particles stuck in the filter screen are often pushed inwards to move into the submersible pump. Due to their size, the particles pushed inwards cannot be poured out of the filter screen holes. The particles pushed inwards can damage the impeller blades during operation, especially since the amount of particles pushed inwards is relatively large. Therefore, an improvement to the water inlet structure is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a filter-type permanent magnet submersible pump inlet structure to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a filter-type permanent magnet submersible pump water inlet structure, comprising a main body and a water inlet component at the output end of the main body, the water inlet component comprising:

[0007] End cap one and end cap two are aligned on their upper and lower axes, and a support frame is installed between them;

[0008] The filter layer is secured to end cap one and end cap two at the top and bottom ends respectively. The filter layer is composed of multiple foldable sections connected to each other to form a ring shape. By default, one set is in a folded state. When one folded section is folded, the rest of the section is stretched into a fixed state, squeezing the particles at the folded section outward.

[0009] Furthermore, the upper end of the support frame is fixed to end cover one, and the lower end is fixed to end cover two, which is used to fix the positions of end cover one and end cover two, and the upper end of end cover one is fixed to the main body.

[0010] A support ring with its axis coinciding with that of the end cap is fixed inside the end cap. The outer side of the support ring is tangent to the stretched filter layer.

[0011] Furthermore, the filter layer includes multiple shafts and multiple sets of foldable sheets;

[0012] A circular groove is provided at the lower end of the end cap, and a circular groove is provided at the upper end of the end cap. Multiple shafts have blocks that extend into the circular grooves at their upper and lower ends respectively. Foldable pieces are connected between two adjacent shafts, and multiple sets of foldable pieces are distributed in a circumferential pattern with the multiple shafts at intervals. One set of foldable pieces is folded.

[0013] Furthermore, the axes of the first and second circular grooves coincide and are the same in size and depth. The inner and outer surfaces of the block at the end of the shaft are both arc-shaped, fitting with the first and second circular grooves.

[0014] Furthermore, the block at the end of the shaft is made of metal with a smooth surface, and the inner walls of both the first and second circular grooves are also smooth.

[0015] Furthermore, the foldable sheet includes a first sheet and a second sheet, which are hinged to each other, and the outer sides of the first sheet and the second sheet are respectively hinged to the shafts on both sides.

[0016] Furthermore, both sheet one and sheet two have filter holes for filtration. When sheet one and sheet two are folded, they fit together and the filter holes on sheet one and sheet two are misaligned. When unfolded, they form a straight line.

[0017] Furthermore, both sheet one and sheet two are vertical metal sheets, with their upper and lower sides respectively contacting end cap one and end cap two.

[0018] Furthermore, each of the two sheets has a longitudinally extending connecting cavity on the side that is close to each other. The side that is close to each other of the two sheets forms an arc surface that fits together. The axis of the connecting cavity coincides with the axis of the arc surface. A double shaft bracket is inserted into the connecting cavity of the two sheets for connecting the two sheets.

[0019] Furthermore, both sides of the shaft are fixed with connecting shafts parallel to the shaft axis. The side of the first and second sheets that are far apart from each other is also an arc surface. The arc surface is in contact with the shafts on both sides. The connecting shafts of the two shafts that are opposite each other penetrate the first and second sheets longitudinally, and coincide with the axis of the arc surface on the side of the first and second sheets that are far apart from each other.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] 1. Multiple sets of foldable sheets are connected in a ring by shafts. By default, one set is in a folded state. When adjacent shafts are manually pinched, the target foldable sheet folds, and the remaining foldable sheets automatically unfold, maintaining a constant filtration area. The foldable sheets can only be folded outwards. When folding, sheet one and sheet two are pressed and adhered to each other, and their filter holes are misaligned. The filter holes form an inward-outward squeezing force, which pushes out stuck particles from the filter holes, preventing particles from entering the pump body and preventing forced squeezing to enlarge the filter holes. This also prevents particles from entering the pump body and damaging the impeller, thus extending the life of the submersible pump. Even if particles are not completely squeezed out, the inner end of the filter hole is blocked after folding, making it easy to manually remove them.

[0022] 2. Fold only one set of foldable plates at a time, while maintaining water filtration in the rest of the machine. No need to stop the machine. Fold each set of foldable plates in sequence to achieve a complete cleaning of the annular filter layer. Single-point cleaning can be completed by manually pinching the shaft. No tools are required. The entire filter layer can be covered by operating in the annular sequence.

[0023] 3. The support ring resists the negative pressure of the water flow, ensuring that the filter can only be folded outwards, maintaining operational reliability. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the water inlet component structure of the present invention;

[0027] Figure 3 This is a schematic diagram of the exploded structure of the water inlet component of the present invention;

[0028] Figure 4 This is a schematic diagram of the end cap structure of the present invention;

[0029] Figure 5 This is a schematic diagram of the end cap structure of the present invention;

[0030] Figure 6 This is a schematic diagram of the filter layer structure of the present invention;

[0031] Figure 7 This is a top view of the filter layer structure of the present invention;

[0032] Figure 8 This is a partial structural diagram of the filter layer of the present invention;

[0033] Figure 9This is an exploded structural diagram of the foldable sheet of the present invention;

[0034] Figure 10 This is a top view of the structure of the filter layer of the present invention installed on end cap 2.

[0035] In the diagram: 1. Main body; 2. Water inlet component; 21. End cap one; 211. Circular groove one; 22. End cap two; 221. Circular groove two; 23. Support frame; 24. Filter layer; 241. Shaft; 242. Foldable sheet; 243. Sheet one; 244. Sheet two; 245. Filter hole; 246. Connecting shaft; 247. Connecting cavity; 248. Double shaft frame; 3. Support ring. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Please see Figures 1-10 This invention provides a technical solution: When cleaning particles stuck on a filter screen, the existing method typically involves directly squeezing the particles inwards to allow them to enter the submersible pump. However, since the particles are already squeezed in, they are difficult to empty. Furthermore, if the particles stuck on the filter screen are hard, the impact of squeezing them inwards on the submersible pump is even greater. Hard particles can also enlarge the filter screen pores when squeezed inwards, affecting filtration and reducing the filter's lifespan. Based on this, a filter-type permanent magnet submersible pump inlet structure is proposed, such as... Figures 1-3 As shown, the system includes a main body 1 and a water inlet component 2 at the output end of the main body 1. The water inlet component 2 includes:

[0038] End cap 1 21 and end cap 22 are aligned on their upper and lower axes, and a support frame 23 is installed between them.

[0039] The filter layer 24 is engaged with end cap 21 and end cap 22 at its upper and lower ends, respectively. The filter layer 24 is formed by connecting multiple foldable sections to form a ring. By default, one set is in a folded state. When one folded section is folded, the remaining parts are stretched into a fixed state, squeezing the particles at the folded section outward.

[0040] Specifically, it includes a main body 1 and a water inlet component 2 at the output end of the main body 1. The main body 1 is a submersible pump, which is an existing submersible pump used in water. The water inlet component 2 is a filter component used to filter particulate matter. The water inlet component 2 includes an end cap 21 and an end cap 22 set at the top and bottom. The end cap 21 is fixed to the submersible pump. A support frame 23 is fixed between the end cap 22 and the end cap 21. The actual function of the support frame 23 is to support the end cap 22, so that the water inlet component 2 forms a solid cage. The outer side of the cage has a filter layer 24, which mainly filters the water entering the submersible pump. The filter layer 24 is circular and can be folded. Each folded part can be folded into a piece 242. In the initial state, there is a set of foldable pieces 242 that have been folded, and the rest of the foldable pieces 242 are in the unfolded state. When different sets of foldable pieces 242 are folded, the rest of the foldable pieces 242 will return to the unfolded state, ensuring continuous filtration and not affecting the smooth flow of water in other positions.

[0041] like Figures 4-6 As shown, the upper end of the support frame 23 is fixed to end cover 21 and the lower end is fixed to end cover 22, which is used to fix the position of end cover 21 and end cover 22. The upper end of end cover 21 is fixed to the main body 1.

[0042] A support ring 3 with its axis coinciding with that of the end cap 22 is fixed inside the end cap 22. The outer side of the support ring 3 is tangent to the stretched filter layer 24.

[0043] Specifically, the support frame 23 is a multi-axis structure that serves as a support, fixing end cap 1 21 and end cap 22. It should be noted that when a set of foldable pieces 242 are squeezed and folded, there are two directions of folding: inward and outward. When folding outward, the inner sides of the foldable pieces 242 come into contact with each other, so outward folding is required. The support ring 3 on end cap 22 acts as a barrier, blocking the inner side of the unfolded foldable pieces 242, so that when the foldable pieces 242 deform, they can only be folded outward. In addition, the submersible pump has a negative pressure effect when water enters, pushing the foldable sheet 242 from the outside in. The inner side of the foldable sheet 242 is blocked by the support ring 3, which can prevent all the foldable sheets 242 from undergoing inward partial folding deformation. This would require pulling all the foldable sheets 242 when folding a single set of foldable sheets 242. After each set of foldable sheets 242 undergoes inward partial deformation, each set of foldable sheets 242 needs to be pulled back to its original state to be fully folded. Each set of foldable sheets 242 has friction, which increases the difficulty of operation.

[0044] The filter layer 24 includes multiple shafts 241 and multiple sets of foldable sheets 242;

[0045] The lower end of end cap 21 is provided with a circular groove 211, and the upper end of end cap 22 is provided with a circular groove 221. Both the upper and lower ends of multiple shafts 241 are fixed with blocks that extend into the circular grooves 211 and 221 respectively. Foldable pieces 242 are connected between two adjacent shafts 241, and multiple sets of foldable pieces 242 and multiple shafts 241 are distributed in a circumferentially spaced manner, with one set of foldable pieces 242 being folded.

[0046] Specifically, the upper and lower ends of the multiple shafts 241 each have blocks, which are respectively engaged in the upper and lower circular grooves 211 and 221, keeping the shafts 241 vertical and allowing them to slide along the circular grooves 211 and 221. The foldable piece 242 can be unfolded and folded, or folded and unfolded.

[0047] like Figures 3-6 As shown, the axes of circular groove 1 211 and circular groove 221 coincide and are the same in size and depth. The inner and outer surfaces of the block at the end of the shaft 241 are both arc-shaped, which fits with circular groove 1 211 and circular groove 221.

[0048] The shape of the block matches the first circular groove 211 and the second circular groove 221. Under the action of the block, the shaft 241 is limited, so that it remains vertical even when moving. It should be noted that the block needs to slide along the first circular groove 211 or the second circular groove 221. Therefore, the inner and outer surfaces of the block are arc-shaped and need to fit against the inner walls of the first circular groove 211 or the second circular groove 221. This can prevent the block from rotating and also allow it to slide along the first circular groove 211 or the second circular groove 221.

[0049] The block at the end of the shaft 241 is made of metal with a smooth surface, and the inner walls of the first circular groove 211 and the second circular groove 221 are also smooth.

[0050] Specifically, the upper and lower blocks need to rub against the inner walls of the first circular groove 211 and the second circular groove 221. The metal material can greatly reduce wear and tear, and the smooth design can also minimize friction and extend service life.

[0051] like Figure 8 As shown, the foldable sheet 242 includes a first sheet 243 and a second sheet 244, which are hinged to each other. The outer sides of the first sheet 243 and the second sheet 244 are respectively hinged to the shafts 241 on both sides.

[0052] Specifically, when the two shafts 241 approach each other, the middle layer 243 and layer 244 are hinged on the outside and the connection points are also hinged, thus achieving the folding function. The remaining foldable pieces 242 can only move along the circular grooves 211 and 221 because the shafts 241 are restricted by the circular grooves 211 and 221. Therefore, when one set of foldable pieces 242 is folded, the rest are stretched and in the unfolded state.

[0053] Both sheet 243 and sheet 244 have filter holes 245 for filtration. When sheet 243 and sheet 244 are folded, they fit together and the filter holes 245 on sheet 243 and sheet 244 are misaligned. When unfolded, they form a straight line.

[0054] Specifically, both sheet 1 (243) and sheet 2 (244) have filter holes 245 of the same size. When sheets 1 (243) and 244 (244) are folded, the positions of the filter holes 245 are staggered, so that sheet 1 (243) blocks the filter holes 245 on sheet 2 (244), and sheet 2 (244) blocks the filter holes 245 on sheet 1 (243), thus preventing the filter holes 245 from communicating with each other. It should be noted that when processing particles stuck in the filter holes 245, since the particles do not penetrate the filter holes 245, they move directly outward from the direction of being stuck, thus preventing the filter holes 245 from being enlarged and affecting their ability to block particles.

[0055] Both sheet 243 and sheet 244 are vertical metal sheets, with their upper and lower sides in contact with end cap 21 and end cap 22, respectively.

[0056] Specifically, both sheet 243 and sheet 244 are metal sheets. The thickness of the metal sheets directly affects the depth of the filter hole 245. The particles stuck in the filter hole 245 have a small contact area with the inner wall of the filter hole 245, making it easier to pick out the particles in the filter hole 245. At the same time, the folding and mutual compression of sheet 243 and sheet 244 make it easier to compress the particles and push them outward.

[0057] like Figure 9 As shown, both sheet 1 243 and sheet 2 244 have longitudinally extending connecting cavities 247 on their adjacent sides. The adjacent sides of sheet 1 243 and sheet 2 244 form mutually fitting arc surfaces. The axis of the connecting cavity 247 coincides with the axis of the arc surface. A double shaft bracket 248 is inserted into the connecting cavity 247 of sheet 1 243 and sheet 2 244 for connecting sheet 1 243 and sheet 2 244.

[0058] Specifically, the hinged joints of sheet 1 243 and sheet 2 244 are connected by a double-axis frame 248. Both sheet 1 243 and sheet 2 244 can rotate along the double-axis frame 248. At the same time, the arc surfaces of sheet 1 243 and sheet 2 244 are in contact with each other to avoid gaps, which could cause impurities to get stuck inside and affect the folding function.

[0059] The dual-axis frame 248 consists of two parallel rods connected at their ends, serving as a support and limiting element, and acting as the central axis for folding layer one 243 and layer two 244.

[0060] Both sides of the shaft 241 are fixed with connecting shafts 246 parallel to the axis of the shaft 241. The side of the first layer 243 and the second layer 244 that are far apart from each other is also an arc surface. The arc surface is in contact with the shafts 241 on both sides. The connecting shafts 246 on both sides of the shaft 241 longitudinally penetrate the first layer 243 and the second layer 244 respectively, and coincide with the axis of the arc surface on the side of the first layer 243 and the second layer 244 that are far apart from each other respectively.

[0061] Specifically, the sides of sheet 1 243 and sheet 2 244 that are far apart from each other are also arc-shaped. The shafts 241 on the outer sides of sheet 1 243 and sheet 2 244 each have connecting shafts 246. The connecting shafts 246 on both sides are inserted into sheet 1 243 and sheet 2 244, and the axes of the connecting shafts 246 on both sides coincide with the axes of the arc-shaped surfaces on the sides of sheet 1 243 and sheet 2 244 that are far apart from each other. That is, sheet 1 243 and sheet 2 244 are in contact with the outer shafts 241, and no gaps will be generated when rotating, so as to avoid impurities from getting stuck inside and affecting the rotation.

[0062] The working principle of this invention is as follows: the main body 1 is an existing submersible pump, and the water inlet component 2 is the filter component of the submersible pump. During the operation of the submersible pump, the water flows inward from the water inlet component 2 to filter the water.

[0063] In this process, water flows from the outside through filter layer 24 inwards. Tiny particles are unaffected by layers 243 and 244 and move inwards through filter holes 245. Larger particles are blocked on the outside by the filter holes 245, but medium-sized particles can become trapped inside the filter holes 245, causing blockage of the filter holes 245 in layers 243 and 244, thus affecting the water flow. Figures 6-8 As shown, a set of foldable pieces 242 are in a folded state. By manually pinching two adjacent shafts 241 together, they can form... Figure 8When the foldable sheet 242 is in the folded state, due to the limiting effect of the first circular groove 211 and the second circular groove 221, the other foldable sheet 242 will unfold, and only one folded state can exist. The filter holes 245 on the mutually attached sheet 243 and sheet 244 are misaligned, so that the inner side of the filter hole 245 on sheet 243 is squeezed against sheet 244, and the inner side of the filter hole 245 on sheet 244 is squeezed against sheet 243, realizing the effect of squeezing from the inside out, squeezing out the particles stuck in the filter hole 245, and preventing them from entering the interior of the submersible pump.

[0064] It should be noted that even if it is difficult to squeeze out the particles by stacking and pressing the first layer 243 and the second layer 244, the first layer 243 and the second layer 244 can block the inside of their respective filter holes 245. When the operator cleans, the particles can be squeezed and broken out by pressing the filter holes 245, and the particles can also be picked out without having to operate carefully.

[0065] By manually squeezing the adjacent shafts 241, the different foldable sheets 242 are folded and the remaining foldable sheets 242 are restored, completing one round of operation, cleaning the filter layer 24, and preventing particles from falling into the main body 1.

[0066] During the operation of the main body 1, it can also be operated. Only one set of foldable sheets 242 is in the folded state, while the rest are unfolded. When another set of foldable sheets 242 is folded, the foldable sheets 242 in that set will unfold, so that the filterable part of the filter layer 24 remains unchanged. Cleaning will not affect filtration, and it is almost the same as existing filter components.

[0067] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0068] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention 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 invention should be included within the protection scope of the present invention.

Claims

1. A filter-type permanent magnet submersible pump water inlet structure, comprising a main body (1) and a water inlet component (2) at the output end of the main body (1), characterized in that, The water inlet component (2) includes: End cap one (21) and end cap two (22) have their axes aligned, one above the other, and a support frame (23) is installed between them. The filter layer (24) is engaged with end cap one (21) and end cap two (22) at its upper and lower ends respectively. The filter layer (24) is formed by connecting multiple foldable parts to form a ring. By default, one set is in a folded state. When one folded part is folded, the rest of the parts are stretched into a fixed state, squeezing the particles at the folded part outward. A support ring (3) with its axis coinciding with that of the end cap (22) is fixed inside the end cap (22), and the outer side of the support ring (3) is tangent to the stretched filter layer (24); The filter layer (24) includes multiple shafts (241) and multiple sets of foldable sheets (242). The lower end of the end cap 1 (21) is provided with a circular groove 1 (211), and the upper end of the end cap 2 (22) is provided with a circular groove 2 (221). Both ends of the multiple shafts (241) are fixed with blocks that extend into the circular groove 1 (211) and the circular groove 2 (221) respectively. Foldable pieces (242) are connected between two adjacent shafts (241), and multiple sets of foldable pieces (242) and multiple shafts (241) are distributed in a circumferentially spaced manner. One set of foldable pieces (242) is folded. The foldable piece (242) includes a first piece (243) and a second piece (244), which are hinged to each other. The outer sides of the first piece (243) and the second piece (244) are respectively hinged to the shafts (241) on both sides. Both the first sheet (243) and the second sheet (244) have filter holes (245) for filtering. When the first sheet (243) and the second sheet (244) are folded, they fit together and the filter holes (245) on the first sheet (243) and the second sheet (244) are misaligned, forming a straight line when unfolded.

2. The filter-type permanent magnet submersible pump inlet structure according to claim 1, characterized in that: The upper end of the support frame (23) is fixed to end cap one (21), and the lower end is fixed to end cap two (22), which is used to fix the position of end cap one (21) and end cap two (22). The upper end of end cap one (21) is fixed to the main body (1).

3. The filter-type permanent magnet submersible pump inlet structure according to claim 1, characterized in that: The axes of the first circular groove (211) and the second circular groove (221) coincide and are the same in size and depth. The inner and outer surfaces of the block at the end of the shaft (241) are arc-shaped and fit with the first circular groove (211) and the second circular groove (221).

4. The filter-type permanent magnet submersible pump inlet structure according to claim 3, characterized in that: The block at the end of the shaft (241) is made of metal with a smooth surface, and the inner walls of the first circular groove (211) and the second circular groove (221) are also smooth.

5. The filter-type permanent magnet submersible pump inlet structure according to claim 1, characterized in that: Both sheet one (243) and sheet two (244) are vertical metal sheets, with their upper and lower sides in contact with end cap one (21) and end cap two (22) respectively.

6. The filter-type permanent magnet submersible pump inlet structure according to claim 1, characterized in that: The first layer (243) and the second layer (244) each have a longitudinally extending connecting cavity (247) on the side that is close to each other. The side that is close to each other of the first layer (243) and the second layer (244) forms an arc surface that fits together. The axis of the connecting cavity (247) coincides with the axis of the arc surface. A double shaft bracket (248) is inserted in the connecting cavity (247) of the first layer (243) and the second layer (244) for connecting the first layer (243) and the second layer (244).

7. The filter-type permanent magnet submersible pump inlet structure according to claim 1, characterized in that: Both sides of the shaft (241) are fixed with connecting shafts (246) parallel to the axis of the shaft (241). The side of the first layer (243) and the second layer (244) that are far apart from each other is also an arc surface. The arc surface is in contact with the shaft (241) on both sides. The connecting shafts (246) opposite to the shafts (241) on both sides penetrate the first layer (243) and the second layer (244) longitudinally, and coincide with the axis of the arc surface on the side of the first layer (243) and the second layer (244) that are far apart from each other.

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