Split type shaft hoop for excavator
By using a split shaft clamp structure and a four-point locking design, the problem of easy detachment of the excavator linkage shaft is solved, achieving a more reliable connection and a longer service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-12
- Publication Date
- 2026-03-17
AI Technical Summary
The existing annular sleeve locking screw of the excavator's linkage shaft is prone to cracking or breaking, causing the linkage shaft to detach from the excavator. A more reliable connection method is needed.
It adopts a split shaft clamp structure, including a left shaft clamp flap and a right shaft clamp flap, which are connected by screws to form a four-point locking, increasing the contact area and stability. A positioning pin is used for further fixation, which can adapt to different installation spaces.
This improves the connection stability between the linkage shaft and the excavator, reduces the risk of detachment, and extends the service life of the linkage shaft.
Smart Images
Figure CN224002009U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the technical field of excavator boom and bucket connection device, specifically relating to a split shaft clamp for excavators. Background Technology
[0002] Excavators are important machines in engineering construction. The front end of existing excavators, such as... Figure 17 As shown, the main working part of an excavator is the bucket, which is equipped with bucket lugs. The bucket lugs are connected to the boom via rocker arms and connecting rods. The bucket lugs, boom, rocker arms, and connecting rods form a four-bar linkage mechanical motion pair.
[0003] The shafts of the excavator's boom, rocker arm, rocker arm, and connecting rod all use linkage shafts. Currently, the linkage shafts on excavators are secured at both ends with ring clamps to prevent them from detaching from the excavator. The ring clamps use a single-sided locking screw thread for fastening. However, the high-frequency use and vibration of excavators can cause the locking screws of the ring clamps to crack or break. In this case, the linkage shaft can easily detach from the excavator, causing damage to the linkage shaft. Therefore, a shaft clamp that facilitates the maintenance of the linkage shaft and provides a more reliable connection between the two ends of the linkage shaft is needed. Summary of the Invention
[0004] The purpose of this invention is to solve the above-mentioned problems and to provide a split-type shaft clamp for excavators.
[0005] A split-type shaft clamp for excavators includes: a left shaft clamp flap, a right shaft clamp flap, and a screw rod; both the left and right shaft clamp flaps are semi-circular annular components, with the arc of the left shaft clamp flap being greater than that of the right shaft clamp flap; both the left and right shaft clamp flaps have mating surfaces on both sides, and both mating surfaces are located on the normal line of the annular clamp axis; both sides of the left shaft clamp flap have threaded holes, and both sides of the right shaft clamp flap have countersunk holes for the screw rod; the axis of the countersunk hole of the screw rod can coincide with the axis of the threaded hole; the countersunk hole of the screw rod and the threaded hole are connected by the screw rod thread; the left and right shaft clamp flaps can be seamlessly connected and their inner diameter is circular; the left and right shaft clamp flaps are welded to the four-bar linkage motion component on the excavator boom, and the circular clamp rod is sleeved on the end of the linkage shaft.
[0006] The included angle between the mating surfaces of the left and right shaft clamping flaps is 164 degrees.
[0007] The mating surfaces of the left and right shaft clamps are provided with pin holes, and positioning pins are sleeved in the pin holes.
[0008] The mating surface can be any one of a planar mating surface, an interlaced mating surface, or a W-shaped mating tooth surface.
[0009] The left shaft clamp has a beveled angle on one side of its upper end.
[0010] The mating surfaces of the left and right shaft clamping lobes are both staggered mating surfaces. Each staggered mating surface on both sides is provided with a first mating end face and a second mating end face of the left lobe. The included angle between the first mating end face and the second mating end face of the left lobe on each side is 2 degrees.
[0011] The left shaft clamp has four threaded holes, and the right shaft clamp has four screw countersunk holes. There are four screws, and the four screws are respectively fitted into the four screw countersunk holes. The front end of the screw body is threaded and locked in the threaded hole. The axis of the four screws is parallel to the same normal line on the shaft clamp.
[0012] This technical solution provides a split-type shaft clamp for excavators, comprising: a left shaft clamp flap, a right shaft clamp flap, and a screw rod; both the left and right shaft clamp flaps are semi-circular annular components, with the curvature of the left shaft clamp flap being greater than that of the right shaft clamp flap; both the left and right shaft clamp flaps have mating surfaces on both sides, and both mating surfaces are located on the normal line of the annular shaft clamp axis; both sides of the left shaft clamp flap have threaded holes, and both sides of the right shaft clamp flap have countersunk holes for the screw rod; the axis of the countersunk hole for the screw rod can coincide with the axis of the threaded hole; the countersunk hole for the screw rod and the threaded hole are connected by the screw rod thread; the left and right shaft clamp flaps can be seamlessly connected and their inner diameter is circular; the left and right shaft clamp flaps are welded to the four-bar linkage of the excavator, and the circular shaft clamp is sleeved on the end of the linkage shaft. This technical solution uses two shaft clamps to tighten the end of the linkage shaft. The four-point locking makes the shaft clamps fit more tightly with the outer end face of the linkage shaft, reducing the risk of the shaft clamps falling off and causing the linkage shaft to come off the excavator. Attached Figure Description
[0013] Figure 1 This is a schematic diagram of the assembly state of a shaft and shaft clamp with a flat mating end face according to the present invention;
[0014] Figure 2 This is a schematic diagram of a shaft and shaft clamp structure with a flat mating end face according to the present invention;
[0015] Figure 3 This is a partial sectional view of a shaft and shaft hoop with a flat mating end face according to this utility model;
[0016] Figure 4 This is a top view of a shaft and shaft hoop with a flat mating end face according to the present invention;
[0017] Figure 5 This is a schematic diagram of the assembly state of a shaft and shaft clamp with a positioning pin according to this utility model;
[0018] Figure 6 This is a schematic diagram of a shaft and shaft clamp structure with a positioning pin according to the present invention;
[0019] Figure 7 This is a rear axle side view of a shaft and shaft clamp structure with a positioning pin according to this utility model;
[0020] Figure 8 This is a schematic diagram of the assembly state of a shaft and shaft clamp with a beveled chamfer according to the present invention;
[0021] Figure 9 This is a side view of the shaft hoop structure with a beveled chamfer according to this utility model;
[0022] Figure 10 This is a schematic diagram of the assembly state of a shaft hoop with staggered mating surfaces according to this utility model;
[0023] Figure 11 This is a schematic diagram of a shaft hoop structure with staggered mating surfaces according to the present invention;
[0024] Figure 12 This is a partial sectional view of a shaft hoop with staggered mating surfaces according to this utility model;
[0025] Figure 13 This is a schematic diagram of the assembly state of the first type of shaft hoop with toothed mating surfaces according to this utility model;
[0026] Figure 14 This is a schematic diagram of the first type of shaft hoop structure with toothed mating surfaces according to this utility model;
[0027] Figure 15 This is a partial sectional view of the first type of shaft hoop with a toothed mating surface according to this utility model;
[0028] Figure 16 This is a schematic diagram of the installation state of a split-type shaft clamp for an excavator according to this utility model;
[0029] Figure 17 This is a schematic diagram of the connection between the boom and bucket of an existing excavator.
[0030] Reference numerals: 11. First left shaft clamping flap; 111. First left mating end face; 112. First threaded hole; 12. First right shaft clamping flap; 121. First right mating end face; 122. First screw countersunk hole; 13. First screw; 21. Second left shaft clamping flap; 211. Second left mating end face; 212. Second threaded hole; 213. Left pin hole; 22. Second right shaft clamping flap; 221. Second right mating end face; 222. Second screw countersunk hole; 223. Right pin hole; 23. Second screw; 24. Locating pin; 31. Third left shaft clamping flap; 311. Beveled chamfer; 32. Third right shaft clamping flap; 33. Third screw; 41. Fourth left shaft clamping flap; 4 11. First mating face of the left lobe; 412. Fourth threaded hole I; 413. Second mating face of the left lobe; 414. Fourth threaded hole II; 42. Fourth right shaft collar lobe; 421. First mating face of the right lobe; 422. Fourth screw countersunk hole; 423. Second mating face of the right lobe; 43. Fourth screw; 51. Fifth left shaft collar lobe; 511. Left lobe tooth mating face; 512. Fifth threaded hole; 52. Fifth right shaft collar lobe; 521. Right lobe tooth mating face; 522. Fifth screw countersunk hole; 53. Fifth screw; 71. Shaking arm; 72. Bucket; 73. Rocker arm; 74. Connecting rod; 75. Bucket ear connecting shaft; 76. Connecting rod frame shaft; 8. Annular collar. Detailed Implementation
[0031] The technical solution will be further described clearly and completely below with reference to the accompanying drawings. The described embodiments are only a part of the technical solution, not all of the embodiments. All other embodiments obtained by those skilled in the art based on this technical solution without creative effort are within the scope of protection of this utility model.
[0032] See Figures 1 to 4 As shown, a shaft clamp with a flat mating end face includes: a first left shaft clamp 11, a first right shaft clamp 12, and a first screw 13;
[0033] The first left shaft clamp 11 and the first right shaft clamp 12 are both semi-circular ring-shaped components; the first left shaft clamp 11 has a first left mating end face 111 on both sides, and the first left mating end face 111 on both sides is located on the normal line of the axis of the first left shaft clamp 11; the first right shaft clamp 12 has a first right mating end face 121 on both sides, and the first right mating end face 121 on both sides is located on the normal line of the axis of the first right shaft clamp 12.
[0034] Two first threaded holes 112 are provided on each side of the first left mating end face 111; two first screw countersunk holes 122 are provided on each side of the first right mating end face 121; the two first screw countersunk holes 122 on the first right shaft clamping flap 12 correspond to the two first threaded holes 112 on the two sides of the first left mating end face 111 respectively, and the axis of the first threaded hole 112 coincides with the axis of the first screw countersunk hole 122;
[0035] The first screw 13 is provided in four parts, and the four first screws 13 are respectively sleeved in the four first screw countersunk holes 122, and the front ends of the four first screws 13 are respectively threaded and locked in the four first threaded holes 112.
[0036] The first left mating end face 111 and the first right mating end face 121 are both planar mating surfaces; the first left mating end faces 111 on both sides can fit tightly with the first right mating end faces 121 on both sides; the first left shaft clamp 11 and the first right shaft clamp 12 are locked and fixedly connected by the first screw 13.
[0037] The curvature of the first left shaft clamp 11 is greater than that of the first right shaft clamp 12; the first left shaft clamp 11 and the first right shaft clamp 12 are seamlessly connected to form a first type of linkage shaft sleeve, and the end of the linkage shaft is fastened to the center of the first type of linkage shaft sleeve.
[0038] In this embodiment, the two mating end faces of the first shaft hoop are provided with a certain included angle α. The included angle α of the two mating end faces is 160 degrees, and the included angle α can also be 164 degrees.
[0039] The mating end faces on both sides of the first shaft clamp are provided with a certain included angle, which increases the axial length of the threaded hole and increases the contact area of the thread teeth between the internal threaded rod and the threaded hole. The first screw 13 can connect the first left shaft clamp 11 and the first right shaft clamp 12 more tightly and reliably.
[0040] See Figures 5 to 7 As shown, a shaft clamp with a locating pin includes: a second left shaft clamp flap 21, a second right shaft clamp flap 22, a second screw 23, and a locating pin 24;
[0041] The second left shaft clamp 21 has the same structure as the first left shaft clamp 11 described in Embodiment 1; the second right shaft clamp 22 has the same structure as the first right shaft clamp 12 described in Embodiment 1; the second screw 23 has the same structure as the first screw 13 described in Embodiment 1.
[0042] The second left shaft clamp 21 and the second right shaft clamp 22 are both semi-circular ring-shaped components; the second left shaft clamp 21 and the second right shaft clamp 22 are fixedly connected by the second screw 23, and the second left shaft clamp 21 and the second right shaft clamp 22 are assembled into a second type of linkage shaft sleeve, the end of the linkage shaft can be fitted into the inner diameter of the second type of linkage shaft sleeve; the second left shaft clamp 21 has a second left mating end face 211 on both sides, and the second right shaft clamp 22 has a second right mating end face 221 on both sides; the second left mating end face 211 and the second right mating end face 221 are both located on the normal line of the axis of the second type of linkage shaft sleeve; the second left mating end face 211 and the second right mating end face 221 are both planar mating surfaces; the second left mating end face 211 and the second right mating end face 221 can fit together seamlessly and tightly.
[0043] The curvature of the second left-axis clamping flap 21 is greater than the curvature of the second right-axis clamping flap 22;
[0044] The second left mating end face 211 is provided with a second threaded hole 212 and a left pin hole 213. Each side of the second left mating end face 211 is provided with two second threaded holes 212 and one left pin hole 213, with one left pin hole 213 located between the two second threaded holes 212. The second right mating end face 221 is provided with a second screw countersunk hole 222 and a right pin hole 223. Each side of the second right mating end face 221 is provided with two second screw countersunk holes 222 and one right pin hole 223, with one right pin hole 223 located between the two second screw countersunk holes 222.
[0045] The second threaded hole 212 corresponds to the second screw countersunk hole 222 and their centerlines coincide; the left pin hole 213 corresponds to the right pin hole 223 and their centerlines coincide.
[0046] The left pin hole 213 and the right pin hole 223 form a pin sleeve, and the positioning pin 24 is sleeved in the pin sleeve;
[0047] One side of the positioning pin 24 is interference-fitted with the left pin hole 213 or the right pin hole 223;
[0048] In this embodiment, the second left docking end face 211 and the second right docking end face 221 are provided with an included angle of 164 degrees.
[0049] Positioning pins are provided on the second left shaft clamp flap 21 and the second right shaft clamp flap 22, which can better connect and make shaft clamp connection more convenient.
[0050] See Figures 8 to 9 As shown, a shaft clamp with a beveled angle includes: a third left shaft clamp 31, a third right shaft clamp 32, and a third screw 33;
[0051] The third right-axis clamp 32 has the same structure as the first right-axis clamp 12 described in Embodiment 1; the third screw 33 has the same structure as the first screw 13 described in Embodiment 1.
[0052] The third left shaft clamp 31 and the third right shaft clamp 32 are both semi-circular ring-shaped components; the third left shaft clamp 31 and the third right shaft clamp 32 are locked together by the third screw 33 to form a third type of linkage shaft sleeve;
[0053] The difference between the third left-axis clamp flap 31 and the first left-axis clamp flap 11 is that the outer end face of the third left-axis clamp flap 31 is provided with a beveled chamfer 311;
[0054] Near the bucket lug of some excavators, the installation space for the shaft hoop is small. In this embodiment, the shaft hoop with the oblique chamfer 311 corresponds to the connection between the bucket lug and the bucket. The shaft hoop with the oblique chamfer in this embodiment is also used in other places where the space is narrow and it is not conducive to fixing the shaft hoop.
[0055] See Figures 10 to 12 As shown, a shaft clamp with staggered mating surfaces includes: a fourth left shaft clamp 41, a fourth right shaft clamp 42, and a fourth screw 43;
[0056] The fourth left-axis collar 41 and the fourth right-axis collar 42 are both semi-circular ring-shaped components; the fourth left-axis collar 41 has a first docking end face 411 and a second docking end face 413 on both sides, and the first docking end face 411 and the second docking end face 413 on both sides are located on the normal line of the axis of the fourth left-axis collar 41; the included angle between the first docking end face 411 and the second docking end face 413 on both sides is 160 degrees, and the included angle between the first docking end face 411 and the second docking end face 413 on each side is 2 degrees.
[0057] The fourth right-axis collar 42 has a right-lobe first docking end face 421 and a right-lobe second docking end face 423 on both sides. The right-lobe first docking end face 421 and the right-lobe second docking end face 423 on both sides are located on the normal line of the axis of the fourth right-axis collar 42. The included angle between the right-lobe first docking end face 421 and the right-lobe second docking end face 423 on both sides is 160 degrees, and the included angle between the right-lobe first docking end face 421 and the right-lobe second docking end face 423 on each side is 2 degrees.
[0058] Each left lobe has a fourth threaded hole I 412 on its first mating end face 411 and a fourth threaded hole II 414 on its second mating end face 413; the center lines of the fourth threaded hole I 412 and the fourth threaded hole II 414 are parallel to each other.
[0059] The fourth right shaft clamping lobe 42 is provided with two fourth screw countersunk holes 422 on both sides; the four fourth screw countersunk holes 422 respectively penetrate to the end faces of the first mating end face 421 and the second mating end face 423 of the right lobe; each fourth screw countersunk hole 422 can coincide with the center line of a fourth threaded hole;
[0060] The fourth screw 43 is provided in four parts, and the four fourth screws 43 are respectively sleeved in the four fourth screw countersunk holes 422, and the front end of the fourth screw 43 is respectively threaded and locked in the fourth threaded hole 412;
[0061] The first mating end face 411 and the second mating end face 413 of the left lobe form a staggered mating surface of the left lobe, and the first mating end face 421 and the second mating end face 423 of the right lobe form a staggered mating surface of the right lobe; the staggered mating surface of the left lobe can fit seamlessly and tightly with the staggered mating surface of the right lobe; the fourth left shaft clamping lobe 41 and the fourth right shaft clamping lobe 42 are threadedly locked together by the fourth screw 43;
[0062] The curvature of the fourth left shaft clamp 41 is greater than that of the fourth right shaft clamp 42; the fourth left shaft clamp 41 and the fourth right shaft clamp 42 are seamlessly connected to form a fourth type of linkage shaft sleeve, and the end of the linkage shaft can be fastened to the center of the fourth type of linkage shaft sleeve.
[0063] See Figures 13 to 15 As shown, a shaft clamp with a toothed mating surface includes: a fifth left shaft clamp 51, a fifth right shaft clamp 52, and a fifth screw 53;
[0064] Both the fifth left-axis clamp flap 51 and the fifth right-axis clamp flap 52 are semi-circular ring-shaped components;
[0065] The fifth left-axis collar 51 has left-leaf tooth mating surfaces 511 on both sides. The left-leaf tooth mating surfaces 511 on both sides are W-shaped mating surfaces. The left-leaf tooth mating surfaces 511 on both sides are located on the normal line of the axis of the fifth left-axis collar 51. The fifth right-axis collar 52 has right-leaf tooth mating surfaces 521 on both sides. The right-leaf tooth mating surfaces 521 on both sides are located on the normal line of the axis of the fifth right-axis collar 52.
[0066] The included angle between the left leaf tooth mating surfaces 511 on both sides and the included angle between the right leaf tooth mating surfaces 521 on both sides is 164 degrees.
[0067] Each side of the left leaf tooth mating surface 511 is provided with two fifth threaded holes 512; each side of the right leaf tooth mating surface 521 is provided with two fifth screw countersunk holes 522; each fifth threaded hole 512 can coincide with the axis of a fifth screw countersunk hole 522.
[0068] There are four fifth screws 53, and the four fifth screws 53 are respectively sleeved in the four fifth screw countersunk holes 522. The front end of the fifth screw 53 is respectively threaded and locked in the fifth threaded hole 512.
[0069] The left leaf tooth mating surface 511 on both sides can be W-shaped mating tooth surfaces with the right leaf tooth mating surfaces 521 on both sides. The left leaf tooth mating surface 511 can be seamlessly and tightly fitted with the right leaf tooth mating surfaces 521 on both sides. The fifth left shaft clamping surface 51 and the fifth right shaft clamping surface 52 are connected by a fifth screw 53.
[0070] The curvature of the fifth left shaft clamp 51 is greater than that of the fifth right shaft clamp 52; the fifth left shaft clamp 51 and the fifth right shaft clamp 52 are seamlessly connected to form the fifth type of linkage shaft sleeve, and the end of the linkage shaft 75 can be fastened to the center of the fifth type of linkage shaft sleeve.
[0071] How to use
[0072] See appendix Figure 17 As shown, the existing excavator is equipped with a boom 71, a bucket 72, a rocker arm 73, and a connecting rod 74; the bucket 72 is equipped with a lug 721, and the lug 721, boom 71, rocker arm 73, and connecting rod 74 form a four-bar linkage mechanical kinematic pair.
[0073] The four-bar linkage mechanical kinematic pair is provided with a linkage shaft between the four linkage kinematic components. The linkage shaft is divided into a bucket ear connecting shaft 75 and a connecting rod frame shaft 76.
[0074] The bucket 72 has two shovel lugs 721, which are identical in structure and have shaft connection holes at both ends. The two shovel lugs are connected to the lower end of the connecting rod 74 and the lower end of the shovel arm 71 respectively through two shovel lug connecting shafts 75. The upper end of the connecting rod 74 and the upper end of the shovel arm 71 are provided with connecting rod connecting frame shafts 76. The two ends of the connecting rod 74 are connected to the two connecting rod connecting frame shafts 76 respectively, and the two ends of the connecting rod 74 are connected to the upper end of the connecting rod 74 and the upper end of the shovel arm 71 respectively.
[0075] Referring to Examples 1-5, there are five types of linkage shaft bushings, namely, shaft bushings with flat mating end faces, shaft bushings with positioning pins, shaft bushings with beveled chamfers, shaft bushings with staggered mating surfaces, and shaft bushings with toothed mating surfaces.
[0076] The five types of linkage shaft bushings are all limiting clamps for bucket ear connecting shaft 75 or connecting rod connecting frame shaft 76; the mating surfaces of the left shaft clamp and the right shaft clamp are provided with planar mating surfaces, staggered mating surfaces, and toothed mating surfaces. The staggered mating surfaces and toothed mating surfaces can increase the mating contact area and reduce the axial force applied by the shaft to the single-sided clamp.
[0077] The left and right shaft clamps are a split shaft clamp with a circular inner diameter after being joined together; the left and right shaft clamps are fastened together by four screws, and the axis of the four screws is parallel to the same normal line on the shaft clamp; the four screws constitute a four-point locking component.
[0078] The split shaft clamps are available in different sizes to meet different installation requirements. The split shaft clamps can replace the ear 721. When replacing the ear, the shaft clamp with a beveled angle as described in embodiment 3 is preferred. The third left shaft clamp 31 is welded to the outer wall of the bucket 72, and the third right shaft clamp 32 is threaded to the third left shaft clamp 31. The end of the bucket ear connecting shaft 75 is sleeved in the inner diameter formed by the third left shaft clamp 31 and the third right shaft clamp 32.
[0079] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.
Claims
1. A split collar for excavators, comprising: The utility model discloses a left axis hoop petal, right axis hoop petal, screw rod, its characterized in that: left axis hoop petal and right axis hoop petal are all half circular ring components, and the arc of left axis hoop petal is greater than the arc of right axis hoop petal, and both sides of left axis hoop petal and right axis hoop petal are equipped with butt joint surfaces, and both sides butt joint surfaces are arranged on the normal of annular axis hoop axis center line, both sides of left axis hoop petal are equipped with threaded hole, and both sides of right axis hoop petal are equipped with screw rod counterbore, the axis center line of screw rod counterbore can coincide with the axis center line of threaded hole, and screw rod counterbore and threaded hole are connected through screw rod thread, left axis hoop petal and right axis hoop petal can be butt jointed seamlessly, and the inner diameter thereof is circular hoop, left axis hoop petal and right axis hoop petal are welded on four-bar linkage motion component on excavator arm, and circular hoop is sleeved on linkage shaft end.
2. The split collar for excavators according to claim 1, characterized in that: The included angle of the butt joint surfaces of the left axis hoop petal and the right axis hoop petal is 164 degrees.
3. The split collar for excavators according to claim 2, characterized in that: Pin shaft holes are arranged on the butt joint surfaces of the left axis hoop petal and the right axis hoop petal, and a positioning pin rod is sleeved in the pin shaft holes.
4. The split collar for excavators according to claim 2, characterized in that: The butt joint surfaces are any one of a planar butt joint surface, a staggered butt joint surface and a W-shaped butt joint surface.
5. The split collar for excavators according to claim 2, characterized in that: An oblique cutting corner is arranged on one side of the upper end of the left axis hoop petal.
6. The split collar for excavators according to claim 4, characterized in that: The butt joint surfaces of the left axis hoop petal and the right axis hoop petal are staggered butt joint surfaces, and a left petal first butt joint end surface and a left petal second butt joint end surface are arranged on the two sides of the staggered butt joint surfaces, and the included angle of the left petal first butt joint end surface and the left petal second butt joint end surface on each side is 2 degrees.
7. The split collar for excavators as set forth in any one of claims 1 to 6, characterized in that: Four threaded holes are arranged on the left axis hoop petal, four screw rod counterbores are arranged on the right axis hoop petal, four screw rods are arranged, the four screw rods are sleeved in the four screw rod counterbores respectively, and the front end of the rod body of the screw rod is screwed and locked in the threaded hole; the axis center lines of the four screw rods are parallel to the same normal on the axis hoop.