Limiting structure for permanent magnet coupler
By introducing shaft end and shoulder limiting components into the permanent magnet coupling, the axial raft and radial jump problems of traditional permanent magnet couplings during high-speed operation are solved, ensuring air gap uniformity and bolt stability, and improving transmission efficiency and reliability.
Patent Information
- Application Number
- CN202510654388.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-21
- Publication Date
- 2025-07-04
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Traditional permanent magnet couplings are prone to axial twitching and radial twitching due to axial forces or vibrations during high-speed operation, resulting in dislocation of the magnetic surface, affecting transmission efficiency, and the rotor fastening bolts may be loose, and the existing limiting structure cannot solve these problems at the same time.
The shaft end restriction assembly and the shoulder restriction assembly are used to limit the movement of the magnetic rotor from the axial and radial directions respectively. The fit between the tightening ring and the restriction bushing is achieved through the tapered restriction, ensuring the uniformity of the air gap, and the rotor tightening bolts are stuck through the shoulder restriction assembly to prevent them from loosening.
Effectively prevent the magnetic surface misalignment caused by vibration or axial force of the magnetic rotor, improve transmission stability and reliability, reduce the risk of bolt loosening, and improve structural stability and dynamic balance performance.
Smart Images
Figure CN120262842A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of permanent magnet couplings, and more particularly to a limiting structure for a permanent magnet coupling. Background Art
[0002] A coupling is a mechanical part used to connect two shafts (the driving shaft and the driven shaft) in different mechanisms to rotate together to transmit torque and rotational speed. In high-speed and heavy-duty power transmission, some couplings also have the functions of buffering, vibration damping, and improving the dynamic performance of the shafting. A permanent magnet coupling is a transmission device that realizes non-contact torque transmission by using the magnetic field generated by permanent magnets. It transfers power from the driving end to the driven end through magnetic coupling, without mechanical connection, thus avoiding the problems of wear, vibration, and lubrication of traditional couplings. In recent years, with the improvement of the performance of permanent magnet materials and the development of precision manufacturing technology, permanent magnet couplings have been increasingly widely used in the industrial field.
[0003] The magnetic rotor of a traditional permanent magnet coupling is prone to axial movement and radial runout due to axial force or vibration during high-speed operation, resulting in misalignment of the magnetic force surfaces, affecting the air gap uniformity, and reducing the transmission efficiency. In addition, the rotor fastening bolts may loosen in a long-term vibration environment, further increasing the risk of rotor displacement. In the prior art, a single limiting structure or bolt loosening prevention measures are usually adopted, but the problems of axial and radial displacement and bolt loosening cannot be solved simultaneously, resulting in insufficient reliability of the coupling. Summary of the Invention
[0004] The purpose of the present invention is to provide a limiting structure for a permanent magnet coupling to solve the technical problems raised in the background art.
[0005] To achieve the above object, the present invention provides the following technical solutions:
[0006] A limiting structure for a permanent magnet coupling, comprising a shaft end limiting component installed at the front end of a connecting shaft body and a shaft shoulder limiting component arranged at the shaft shoulder of the connecting shaft body. The magnetic rotor of the permanent magnet coupling has a rotor main body and a rotor sleeve. Among them, the rotor sleeve is installed on the connecting shaft body through a flat key, and the rotor main body is sleeved on the rotor sleeve and fastened together at the end close to the shaft shoulder through rotor fastening bolts; the rotor main body has a limiting bushing facing the front end of the connecting shaft body, and the inner wall of the limiting bushing is a conical surface, and the open end with a larger diameter faces the shaft end limiting component. The shaft end limiting component includes a front end disc, a bushing limiting part and a limiting pressing ring. The front end disc is fastened to the front end of the connecting shaft body through shaft end fastening bolts and is concentric with it. The bushing limiting part and the limiting pressing ring are both arranged on the end face of the front end disc facing the connecting shaft body. The bushing limiting part is sleeved on the front end of the connecting shaft body and abuts against the end of the rotor sleeve; the limiting pressing ring is a conical structure, and the limiting pressing ring is inserted into the limiting bushing and abuts against the inner wall of the limiting bushing; the shaft shoulder limiting component is located between the rotor sleeve and the shaft shoulder, and the rotor sleeve can be stuck at the end of the rotor fastening bolt to limit its rotation.
[0007] On the basis of the above technical solutions, the present invention also provides the following alternative technical solutions:
[0008] In an alternative solution: the maximum outer diameter of the limiting pressing ring is greater than the inner diameter of the opening of the limiting bushing, and the minimum outer diameter of the limiting pressing ring is less than the inner diameter of the opening of the limiting bushing. The outer wall of the limiting pressing ring has a plurality of axially distributed circumferential cuts.
[0009] In an alternative solution: the axial length of the limiting pressing ring is greater than the axial length of the limiting bushing.
[0010] In an alternative solution: a plurality of circumferentially distributed elastic pressing members are arranged on the front end disc. The elastic pressing members include a limiting top rod and a limiting plate. The limiting top rod can slide through the front end disc. The end of the limiting top rod facing the connecting shaft body is fixedly connected to the limiting pressing ring. The limiting plate is arranged at the other end of the limiting top rod, and a moving spring is connected between the limiting plate and the end face of the front end disc.
[0011] In an alternative solution: the end face of the front end of the connecting shaft body has a plurality of screw hole parts, the front end disc is provided with a plurality of fastening holes respectively corresponding to the plurality of screw hole parts, and the shaft end fastening bolts pass through the fastening holes and are in threaded cooperation with the corresponding screw hole parts.
[0012] In an alternative solution: The shoulder limiting assembly includes a shoulder defining disc, an axial limiting sleeve, and a blocking ring. The shoulder defining disc is sleeved on the connecting shaft body and is located at the shoulder position. One side of the shoulder defining disc has an axial limiting sleeve sleeved on the shoulder, and the axial limiting sleeve is fastened to the outer wall of the shoulder through a connecting bolt portion. On the other side of the shoulder defining disc, a clamping groove portion is provided. When the rotor shaft sleeve is sleeved on the connecting shaft body, the clamping groove portion can abut against the connecting portion between the rotor shaft sleeve and the rotor body, and the rotor fastening bolt is snapped into the clamping groove portion.
[0013] In an alternative solution: The clamping groove portion includes a blocking ring and a plurality of arc-shaped relief grooves opened on the end face of the blocking ring. Inside each arc-shaped relief groove, two slidable limiting clamping blocks are provided. On the opposite sides of the two limiting clamping blocks, clamping springs are connected to the inner wall of the arc-shaped relief groove respectively. When the blocking ring abuts against the connecting portion between the rotor shaft sleeve and the rotor body, the end portion of the rotor fastening bolt is correspondingly inserted into the arc-shaped relief groove and is located between the two limiting clamping blocks.
[0014] Adopting the above technical solutions, the present invention has the following beneficial effects:
[0015] In the limiting structure for the permanent magnet coupling provided by the present invention, through the cooperation of the shaft end limiting assembly and the shoulder limiting assembly, the movement of the magnetic rotor is restricted axially and radially respectively, avoiding the misalignment of the magnetic force surfaces caused by vibration or axial force, and ensuring the uniformity of the air gap; the shoulder limiting assembly clamps the rotor fastening bolt to restrict its rotation, effectively reducing the risk of the bolt loosening due to vibration and improving the structural stability; the bushing limiting portion and the shoulder limiting assembly clamp the rotor shaft sleeve from both ends to prevent the axial movement of the rotor shaft sleeve and the rotor body, maintaining the transmission accuracy; the conical limiting abutting ring is closely fitted with the conical surface of the limiting bushing to restrict the radial runout of the rotor body, further optimizing the dynamic balance performance; each component is connected with high rigidity through bolt fastening and conical surface fitting, without additional complex mechanisms, being easy to assemble and having low maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0017] Figure 1 It is a schematic diagram of the overall structure of the limiting structure in an embodiment of the present invention.
[0018] Figure 2 It is a schematic diagram of the axial sectional structure of the limiting structure in an embodiment of the present invention.
[0019] Figure 3 Schematic diagram of the magnetic rotor and the connecting shaft body structure in an embodiment of the present invention.
[0020] Figure 4 Schematic diagram of one perspective structure of the end limiting component in an embodiment of the present invention.
[0021] Figure 5 Schematic diagram of another perspective structure of the end limiting component in an embodiment of the present invention.
[0022] Figure 6 Schematic diagram of one perspective structure of the shoulder limiting component in an embodiment of the present invention.
[0023] Figure 7 Schematic diagram of another perspective structure of the shoulder limiting component in an embodiment of the present invention.
[0024] Annotation of reference numerals: connecting shaft body 100, shaft shoulder part 110, screw hole part 120, rotor main body 200, limiting bushing 210, shaft end limiting component 300, front end disc 310, bushing limiting part 320, limiting abutting ring 330, defining top rod member 350, defining plate 360, top moving spring 370, shoulder limiting component 400, shoulder defining disc 410, axial defining sleeve 420, connecting bolt part 430, blocking ring 440, arc-shaped avoidance groove 450, defining clamping block 460, clamping spring 470, rotor shaft sleeve 500, rotor fastening bolt 510, shaft end fastening bolt 600. Detailed implementation manners
[0025] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0026] The left, right, up, and down positions of each component shown in the drawings are just a layout method, and the specific positions are set according to specific needs.
[0027] In one embodiment, as Figures 1-5As shown in the figure, a limit structure for a permanent magnet coupling includes a shaft end limiting component 300 installed at the front end of the connecting shaft body 100 and a shaft shoulder limiting component 400 provided at the shaft shoulder 110 of the connecting shaft body 100. The magnetic rotor of the permanent magnet coupling has a rotor main body 200 and a rotor sleeve 500. Among them, the rotor sleeve 500 is installed on the connecting shaft body 100 through a flat key, and the rotor main body 200 is sleeved on the rotor sleeve 500 and fastened together at the end close to the shaft shoulder 110 through a rotor fastening bolt 510. The front end of the rotor main body 200 facing the connecting shaft body 100 has a limiting bushing 210, and the inner wall of the limiting bushing 210 is a conical surface, and the open end with a larger diameter faces the shaft end limiting component 300. The shaft end limiting component 300 includes a front end disc 310, a bushing limiting part 320 and a limiting abutting ring 330. The front end disc 310 is fastened to the front end of the connecting shaft body 100 through a shaft end fastening bolt 600 and is concentric with it. The bushing limiting part 320 and the limiting abutting ring 330 are both arranged on the end face of the front end disc 310 facing the connecting shaft body 100. The bushing limiting part 320 is sleeved on the front end of the connecting shaft body 100 and abuts against the end of the rotor sleeve 500. The limiting abutting ring 330 is a conical structure, and the limiting abutting ring 330 is inserted into the limiting bushing 210 and abuts against the inner wall of the limiting bushing 210. The shaft shoulder limiting component 400 is located between the rotor sleeve 500 and the shaft shoulder 110, and the rotor sleeve 500 can be stuck at the end of the rotor fastening bolt 510 to limit its rotation.
[0028] In an embodiment of the present invention, before installing the magnetic rotor of the permanent magnet coupling at the end of the connecting shaft body 100, the shaft shoulder limiting component 400 is placed at the shaft shoulder portion 110 of the connecting shaft body 100. The rotor sleeve 500 is sleeved on the front end of the connecting shaft body 100 through a flat key. The end of the rotor sleeve 500 close to the shaft shoulder portion 110 abuts against the shaft shoulder limiting component 400. The rotor fastening bolt 510 connecting the rotor sleeve 500 and the rotor body 200 is stuck on the shaft shoulder limiting component 400. The shaft shoulder limiting component 400 can limit the rotation of the rotor fastening bolt 510, thereby reducing the loosening phenomenon of the rotor fastening bolt 510 caused by vibration. The shaft end limiting component 300 is installed at the front end of the connecting shaft body 100 through the shaft end fastening bolt 600. The bushing limiting portion 320 in the shaft end limiting component 300 abuts against the end of the rotor sleeve 500 away from the shaft shoulder limiting component 400. The bushing limiting portion 320 and the shaft shoulder limiting component 400 limit the rotor sleeve 500 from both ends to prevent the axial movement of the rotor sleeve 500 and limit the misalignment between the rotor sleeve 500 and the rotor body 200. The limiting abutting ring 330 in the shaft end limiting component 300 abuts against the inner wall of the limiting bushing 210 in a conical surface manner. The limiting abutting ring 330 can limit the radial runout of the rotor body 200 relative to the connecting shaft body 100 through the limiting bushing 210 to ensure the uniformity of the air gap. Therefore, overall, the rotor sleeve 500 and the shaft end limiting component 300 cooperate with each other to limit the axial movement and radial runout of the magnetic rotor, avoiding the misalignment of the magnetic force surface caused by vibration or axial force.
[0029] In one embodiment, as Figures 1-5 shown, the end face of the front end of the connecting shaft body 100 has a plurality of screw hole portions 120. A plurality of fastening holes corresponding to the plurality of screw hole portions 120 are provided on the front end disc 310. The shaft end fastening bolt 600 passes through the fastening hole and is in threaded fit with the corresponding screw hole portion 120. In the embodiment of the present invention, the plurality of shaft end fastening bolts 600 fasten the front end disc 310 to the front end of the connecting shaft body 100 in a circumferentially uniformly distributed manner, which can improve the coincidence degree of the axes of the bushing limiting portion 320 and the limiting abutting ring 330 with the axis of the connecting shaft body 100.
[0030] In one embodiment, as Figures 1-5As shown, the maximum outer diameter of the limiting tightening ring 330 is greater than the inner diameter at the opening of the limiting bushing 210, and the minimum outer diameter of the limiting tightening ring 330 is less than the inner diameter at the opening of the limiting bushing 210. The outer wall of the limiting tightening ring 330 has a plurality of axially distributed circumferential cuts. In the embodiment of the present invention, due to the existence of the axial cuts, the limiting tightening ring 330 can be tightened when pressed. Therefore, when the limiting tightening ring 330 is inserted into the interior of the limiting bushing 210, the front end portion of the limiting tightening ring 330 is close to the inner wall of the limiting bushing 210 and effectively limits the radial runout of the rotor body 200. The axial length of the limiting tightening ring 330 is greater than the axial length of the limiting bushing 210.
[0031] In one embodiment, as Figures 1-5 shown, a plurality of circumferentially distributed elastic pressing members are provided on the front end disk 310. The elastic pressing members include a defining top rod member 350 and a defining plate 360. The defining top rod member 350 can slide through the front end disk 310. The end of the defining top rod member 350 facing the connecting shaft body 100 is fixedly connected to the limiting tightening ring 330. The defining plate 360 is provided at the other end of the defining top rod member 350, and a top spring 370 is connected between the defining plate 360 and the end face of the front end disk 310. In the embodiment of the present invention, the front end disk 310 is fixed to the front end portion of the connecting shaft body 100. The limiting tightening ring 330 is inserted into the interior of the limiting bushing 210 and abuts against the inner wall of the limiting bushing 210. Since the top spring 370 is stretched, the elastic force for restoring its deformation always acts on the limiting tightening ring 330, so that the limiting tightening ring 330 always maintains abutment against the inner wall of the limiting bushing 210, effectively limiting the radial runout of the rotor body 200. Due to the stretching of the top spring 370, the limiting tightening ring 330 can adapt to limiting bushings 210 of different diameters.
[0032] In one embodiment, as Figures 1-7 shown, the shoulder limiting assembly 400 includes a shoulder defining disk 410, an axial defining sleeve 420, and a blocking ring 440. The shoulder defining disk 410 is sleeved on the connecting shaft body 100 and is in the position of the shoulder portion 110. One side of the shoulder defining disk 410 has an axial defining sleeve 420 sleeved on the shoulder portion 110, and the axial defining sleeve 420 is fastened to the outer wall of the shoulder portion 110 through a connecting bolt portion 430. A slot portion is provided on the other side of the shoulder defining disk 410. When the rotor shaft sleeve 500 is sleeved on the connecting shaft body 100, the slot portion can abut against the connecting portion of the rotor shaft sleeve 500 and the rotor body 200, and the rotor fastening bolt 510 is caught in the slot portion. In the embodiment of the present invention, the slot portion abuts against the rotor shaft sleeve 500 to limit the axial movement of the rotor shaft sleeve 500 relative to the connecting shaft body 100, and the rotor fastening bolt 510 is caught in the slot portion. The slot portion can limit the rotation of the rotor fastening bolt 510 to ensure the firmness of the rotor shaft sleeve 500 and the rotor body 200, and avoid the loosening of the rotor fastening bolt 510 due to vibration and impact.
[0033] In one embodiment, as Figures 1-7 shown, the card slot portion includes a blocking ring 440 and a plurality of arc-shaped relief grooves 450 formed on the end face of the blocking ring 440. Two slidable limiting clamping blocks 460 are arranged inside each arc-shaped relief groove 450. On the opposite sides of the two limiting clamping blocks 460, they are connected to the inner wall of the arc-shaped relief groove 450 through clamping springs 470. When the blocking ring 440 abuts against the connecting portion between the rotor shaft sleeve 500 and the rotor body 200, the end of the rotor fastening bolt 510 is correspondingly inserted into the arc-shaped relief groove 450 and is located between the two limiting clamping blocks 460. In the embodiment of the present invention, with the end of the rotor fastening bolt 510 located between the two limiting clamping blocks 460, under the elastic force of the clamping spring 470, the end face of the limiting clamping block 460 away from the clamping spring 470 abuts against the end of the rotor fastening bolt 510 to limit the rotation of the end of the rotor fastening bolt 510, thereby ensuring that the rotor fastening bolt 510 tightly connects the rotor shaft sleeve 500 and the rotor body 200.
[0034] The above-mentioned invention embodiment discloses a limiting structure for a permanent magnet coupling. Among them, the shoulder limiting component 400 is placed at the shaft shoulder 110 of the connecting shaft body 100. The rotor shaft sleeve 500 is sleeved on the front end of the connecting shaft body 100 through a flat key. The end of the rotor shaft sleeve 500 close to the shaft shoulder 110 abuts against the shoulder limiting component 400. The rotor fastening bolt 510 connecting the rotor shaft sleeve 500 and the rotor body 200 is stuck on the shoulder limiting component 400. The shoulder limiting component 400 can limit the rotation of the rotor fastening bolt 510, thereby reducing the loosening phenomenon of the rotor fastening bolt 510 caused by vibration. The shaft end limiting component 300 is installed at the front end of the connecting shaft body 100 through a shaft end fastening bolt 600. The bushing limiting portion 320 in the shaft end limiting component 300 abuts against the end of the rotor shaft sleeve 500 away from the shoulder limiting component 400. The bushing limiting portion 320 and the shoulder limiting component 400 limit the rotor shaft sleeve 500 from both ends to prevent the rotor shaft sleeve 500 from axially moving and limit the misalignment between the rotor shaft sleeve 500 and the rotor body 200. The limiting abutting ring 330 in the shaft end limiting component 300 abuts against the inner wall of the limiting bushing 210 in a conical surface manner. The limiting abutting ring 330 can limit the radial runout of the rotor body 200 relative to the connecting shaft body 100 through the limiting bushing 210 to ensure uniform air gap. Therefore, overall, the rotor shaft sleeve 500 and the shaft end limiting component 300 cooperate with each other to limit the axial movement and radial runout of the magnetic rotor, and avoid the misalignment of the magnetic force surface caused by vibration or axial force.
[0035] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.
Claims
1. A limiting structure for a permanent magnet coupling, comprising a shaft end limiting component installed at the front end of a connecting shaft body and a shaft shoulder limiting component provided at the shaft shoulder of the connecting shaft body. The magnetic rotor of the permanent magnet coupling has a rotor main body and a rotor shaft sleeve, wherein, The rotor shaft sleeve is installed on the connecting shaft body through a flat key, and the rotor main body is sleeved on the rotor shaft sleeve and fastened together at the end near the shaft shoulder through rotor fastening bolts. It is characterized in that the front end of the rotor main body facing the connecting shaft body has a limiting bushing, and the inner wall of the limiting bushing is a conical surface, and the open end with a larger diameter faces the shaft end limiting component; The shaft end limiting component includes a front end disk, a bushing limiting part and a limiting abutting ring. The front end disk is fastened to the front end of the connecting shaft body through shaft end fastening bolts and is concentric with it. The bushing limiting part and the limiting abutting ring are both arranged on the end face of the front end disk facing the connecting shaft body. The bushing limiting part is sleeved on the front end of the connecting shaft body and abuts against the end of the rotor shaft sleeve; The limiting abutting ring is of a conical structure. The limiting abutting ring is inserted into the limiting bushing and abuts against the inner wall of the limiting bushing. The shaft shoulder limiting component is located between the rotor shaft sleeve and the shaft shoulder. The rotor shaft sleeve can be stuck at the end of the rotor fastening bolt to limit its rotation.
2. The limiting structure for a permanent magnet coupling according to claim 1, wherein The maximum outer diameter of the limiting abutting ring is greater than the inner diameter of the opening of the limiting bushing, and the minimum outer diameter of the limiting abutting ring is less than the inner diameter of the opening of the limiting bushing. The outer wall of the limiting abutting ring has a plurality of axially distributed axial cuts.
3. The limit structure for a permanent magnet coupling according to claim 2, characterized in that, The axial length of the limiting abutting ring is greater than the axial length of the limiting bushing.
4. The limiting structure for a permanent magnet coupling according to claim 2, characterized in that, A plurality of circumferentially distributed elastic pressing members are arranged on the front end disk. The elastic pressing members include a defining top rod and a defining plate; The defining top rod can slide through the front end disk. The end of the defining top rod facing the connecting shaft body is fixedly connected to the limiting abutting ring. The defining plate is arranged at the other end of the defining top rod, and a pressing spring is connected between the defining plate and the end face of the front end disk.
5. The limiting structure for a permanent magnet coupling according to claim 1, characterized in that, There are a plurality of screw hole parts on the end face of the front end of the connecting shaft body. A plurality of fastening holes corresponding to the plurality of screw hole parts are arranged on the front end disk. The shaft end fastening bolts pass through the fastening holes and are in threaded cooperation with the corresponding screw hole parts.
6. The limiting structure for a permanent magnet coupling according to any one of claims 1-5, characterized in that, The shaft shoulder limiting component includes a shaft shoulder defining disk, an axial defining sleeve and a blocking ring; The shaft shoulder defining disk is sleeved on the connecting shaft body and is in the position of the shaft shoulder. One side of the shaft shoulder defining disk has an axial defining sleeve sleeved on the shaft shoulder, and the axial defining sleeve is fastened to the outer wall of the shaft shoulder through a connecting bolt part; A clamping groove part is arranged on the other side of the shaft shoulder defining disk. When the rotor shaft sleeve is sleeved on the connecting shaft body, the clamping groove part can abut against the connecting part of the rotor shaft sleeve and the rotor main body, and the rotor fastening bolt is clamped into the clamping groove part.
7. The limit structure for a permanent magnet coupling according to claim 6, characterized in that, The clamping groove part includes a blocking ring and a plurality of arc-shaped avoidance grooves opened on the end face of the blocking ring. Two slidable defining clamping blocks are arranged inside each arc-shaped avoidance groove; One side of the two defining clamping blocks facing away from each other is connected to the inner wall of the arc-shaped avoidance groove through a clamping spring; When the blocking ring abuts against the connecting part of the rotor shaft sleeve and the rotor main body, the end of the rotor fastening bolt is correspondingly inserted into the arc-shaped avoidance groove and is located between the two defining clamping blocks.