A passive knee and ankle assistive exoskeleton

Abstract

The present invention relates to the technical field of exoskeleton robots, and specifically to a passive knee-ankle joint power-assisting exoskeleton, comprising a bracket binding mechanism for binding and fixing human legs, a push rod mechanism for achieving strong axial support and easy lateral bending, a clutch trigger mechanism for adjusting the free restricted state of the joint, and a spring energy storage and release mechanism for power assistance; the spring energy storage and release mechanism comprises a spring bin, a second spring and a steel wire rope; the clutch trigger mechanism comprises an outer gear, an inner gear plate, a first spring and a positioning screw, the outer gear is an incomplete gear, the inner gear plate is provided with inner teeth, and the outer gear is meshed with the inner teeth inside the inner gear plate; the present invention provides a spring energy storage and release mechanism and a clutch trigger mechanism, so that the user can achieve motion assistance during the support period of the lower limbs by storing and releasing energy for the foot contact action and muscle work, and can also achieve joint freedom of the lower limbs during the swing period to avoid affecting the action.

Description

Technical Field

[0001] The present invention relates to the technical field of exoskeleton robots, and specifically to a passive knee and ankle assist exoskeleton. Background Art

[0002] Exoskeleton technology is one of the most advantageous methods to improve human motion efficiency at present. Among them, lower limb exoskeletons mainly have functions such as supporting body weight, enhancing the rotational ability of lower limb joints, and reducing joint injuries. Lower limb exoskeleton technology is mainly divided into two categories: active and passive. Compared with active exoskeletons, passive exoskeletons have the advantages of high reliability, stable output, low requirements for the working environment, and low cost, and are more suitable for applications in scenarios such as military reconnaissance, disaster relief, resource exploration, and special operations. At present, more and more domestic and foreign universities and institutions have begun to research passive lower limb assist exoskeletons for improving human motion ability. Typical multi-joint passive assist exoskeletons include types such as lower limb integral exoskeletons, flexible exoskeletons, and electric energy capture exoskeletons, and currently mainly used ones are all passive exoskeletons.

[0003] Traditional passive exoskeletons mainly achieve assistance by collecting and releasing the energy of the lower limb muscles doing work. The energy of muscle work is limited and is not enough to bring obvious assistance effects. In addition, the structure of multi-joint exoskeletons is complex, resulting in poor reliability and high cost. Summary of the Invention

[0004] The purpose of the present invention is to provide a passive knee and ankle assist exoskeleton, including a bracket binding mechanism for binding and fixing the human leg, a push rod mechanism for achieving strong axial support and easy lateral bending, a clutch trigger mechanism for regulating the free restricted state of the joint, and a spring energy storage and release mechanism for providing assistance; the spring energy storage and release mechanism includes a spring chamber, a second spring, and a steel wire rope. Two pipelines matching the second spring are opened inside the spring chamber. One end of the second spring is fixedly installed at one end of the pipeline. There are two second springs and two steel wire ropes. The two steel wire ropes are respectively fixedly connected to the bottoms of the two second springs; the clutch trigger mechanism includes an external gear, an internal gear disk, a first spring, and a positioning screw. The external gear is an incomplete gear. Internal teeth are provided inside the internal gear disk. The external gear meshes with the internal teeth inside the internal gear disk. The positioning screw is fixedly installed inside the internal gear disk. The first spring is fixedly installed between the external gear and the internal gear disk.

[0005] Optionally, the bracket binding mechanism includes a calf bracket, a thigh bracket, a foot fixator, a knee joint bearing, and an ankle joint bearing. First binding straps are arranged on both sides of the calf bracket. One end of the thigh bracket is connected to the calf bracket through the knee joint bearing, and second binding straps are arranged on both sides of the thigh bracket. The foot fixator is of a U-shaped structure. Chutes are arranged at the tops of both sides of the foot fixator. Third binding straps are arranged between both sides and at the rear of the foot fixator. The ankle joint bearing is fixedly connected to the top of one side of the foot fixator. The foot fixator is connected to the calf bracket through the ankle joint bearing. The knee joint bearing is located at the top of the calf bracket, and the ankle joint bearing is located at the bottom of the calf bracket.

[0006] Optionally, the calf bracket includes an upper calf bracket and a lower calf bracket. Tooth grooves are arranged inside both the upper calf bracket and the lower calf bracket. Corresponding through holes are arranged inside the upper calf bracket and the lower calf bracket. The upper calf bracket and the lower calf bracket are connected through the cooperation of the tooth grooves, and the upper calf bracket and the lower calf bracket are fastened by bolts passing through the internal through holes.

[0007] Optionally, there are two external gears, which are respectively fixed on the side walls of the calf bracket and the foot fixator. Shaft structures are arranged on both sides of the internal gear disk. There are two internal gear disks, and the two internal gear disks are respectively movably connected inside the ankle joint bearing and the knee joint bearing through the shaft structures on both sides. Communication holes matching the shaft structures on both sides of the internal gear disk are arranged inside the calf bracket and the foot fixator.

[0008] Optionally, the push rod mechanism includes a main push rod, a foot plate guide rod, a foot plate, and an elastic rod. The foot plate is of a U-shaped structure. The bottom end of the elastic rod is fixedly connected to one side of the foot plate. The foot plate guide rod is fixedly connected to the other side of the foot plate. The foot plate guide rod matches the chute. Tooth grooves are arranged inside the main push rod. The main push rod has upper and lower parts, and the two parts are connected through the cooperation of the internal tooth grooves. A groove with a slope at one end is arranged on one side of the main push rod. There are two such grooves, and the two grooves are adapted to the shaft structures on one side of the two internal gear disks.

[0009] Optionally, the elastic rod includes an elastic bracket and a T-shaped block. The elastic bracket is an S-shaped bracket. One end of the T-shaped block is fixedly installed inside the elastic bracket through a screw. The elastic bracket is fixedly installed between the main push rod and the foot plate through a screw.

[0010] Optionally, the spring energy storage and release mechanism further includes a wire rope tube and a wire rope tube fixator. There are two wire rope tubes, and the two wire rope tubes are respectively sleeved on the side walls of the two wire ropes. One end of each of the two wire rope tubes is fixedly connected inside the wire rope tube fixator, and the wire rope tube fixator is fixedly connected to the side wall of the calf bracket.

[0011] Optionally, one end of each of the two wire ropes is respectively connected to the inner gear disk inside the ankle joint bearing and the side wall of the inner gear disk inside the knee joint bearing.

[0012] Optionally, threaded holes are provided inside the spring chamber, and adjusting screws are fixedly installed inside the threaded holes. There are several threaded holes.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. By setting the spring energy storage and release mechanism and the clutch trigger mechanism, the user can not only realize the movement assistance during the lower limb support period through the energy storage and release of the foot touching the ground action and muscle work, but also realize the freedom of the joints of the lower limbs during the swing period and avoid affecting the movement.

[0015] 2. By providing threaded holes and adjusting screws inside the spring chamber, when it is necessary to change the stiffness of the second spring, by adjusting the screwing degree of the adjusting screw on the corresponding spring chamber, the fixed position of one end of the second spring is changed, thereby changing the stiffness of the second spring to meet the energy storage requirements of different movements.

[0016] 3. By providing the third binding belt, the foot of the human body can be bound and fixed. By providing through holes and bolts, the total length of the calf bracket can be adjusted by adjusting the position of the through holes fixed by the bolts.

[0017] 4. By providing the bracket binding mechanism, the push rod mechanism, the spring energy storage and release mechanism and the clutch trigger mechanism, the passive knee and ankle joint assistance exoskeleton of the present invention has a simple structure and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of the present invention;

[0019] Figure 2 is a schematic structural diagram of the bracket binding mechanism of the present invention;

[0020] Figure 3 is a schematic structural diagram of the calf bracket of the present invention;

[0021] Figure 4 is a schematic structural diagram of the push rod mechanism of the present invention;

[0022] Figure 5Schematic diagram of the elastic rod structure of the present invention;

[0023] Figure 6 Schematic diagram of the clutch trigger mechanism structure of the present invention;

[0024] Figure 7 Schematic diagram of the spring energy storage and release mechanism structure of the present invention;

[0025] Figure 8 Schematic diagram of an embodiment for assisting human walking and running exercises of the present invention, where the soleplate is shown as semi-transparent;

[0026] Figure 9 Schematic diagram of the clutch trigger action implementation of the present invention, where a partial position of the calf bracket is shown as semi-transparent;

[0027] Figure 10 Schematic diagram of the elastic rod's load-bearing and bending functions in the push rod mechanism of the present invention;

[0028] Figure 11 Schematic diagram of the spring stiffness adjustment of the present invention, where the spring chamber part is shown as semi-transparent.

[0029] Explanation of the reference numerals in the drawings:

[0030] 1. Bracket binding mechanism; 2. Push rod mechanism; 3. Clutch trigger mechanism; 4. Spring energy storage and release mechanism; 11. Calf bracket; 12. Thigh bracket; 13. Foot fixator; 14. Knee joint bearing; 15. Ankle joint bearing; 101. First binding strap; 121. Second binding strap; 131. Slide groove; 132. Third binding strap; 111. Upper calf bracket; 112. Lower calf bracket; 113. Teeth; 114. Through hole; 21. Main push rod; 22. Soleplate guide rod; 23. Soleplate; 24. Elastic rod; 211. Groove; 241. Elastic bracket; 242. T-shaped block; 31. External gear; 32. Internal gear disk; 33. First spring; 34. Positioning screw; 41. Spring chamber; 42. Second spring; 43. Adjusting screw; 44. Steel wire rope; 45. Steel wire rope tube; 46. Steel wire rope tube fixator; 411. Pipe; 412. Threaded hole.

[0031] The realization, functional features, and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0033] Please refer to Figures 1 - 11 , the present invention provides a passive knee and ankle assist exoskeleton, including a bracket binding mechanism 1 for binding and fixing the human leg, a push rod mechanism 2 for achieving strong axial support and easy lateral bending, a clutch trigger mechanism 3 for regulating the free and restricted state of the joint, and a spring energy storage and release mechanism 4 for providing assistance; the spring energy storage and release mechanism 4 includes a spring chamber 41, a second spring 42, and a steel wire rope 44. Two pipes 411 matching the second spring 42 are provided inside the spring chamber 41. One end of the second spring 42 is fixedly installed at one end of the pipe 411. There are two second springs 42 and two steel wire ropes 44. The two steel wire ropes 44 are respectively fixedly connected to the bottoms of the two second springs 42; the clutch trigger mechanism 3 includes an external gear 31, an internal gear disk 32, a first spring 33, and a positioning screw 34. The external gear 31 is an incomplete gear. Internal teeth are provided inside the internal gear disk 32. The external gear 31 meshes with the internal teeth inside the internal gear disk 32. The positioning screw 34 is fixedly installed inside the internal gear disk 32. The first spring 33 is fixedly installed between the external gear 31 and the internal gear disk 32; by setting the spring energy storage and release mechanism 4 and the clutch trigger mechanism 3, the user can not only achieve the movement assistance during the lower limb support period by storing and releasing the energy of the foot touchdown action and muscle work, but also achieve the freedom of the joint during the swing period of the lower limb and avoid affecting the movement. Moreover, the overall structure is simple and the cost is low.

[0034] Refer to Figure 1 , Figure 3 , Figure 4 , Figure 5, the push rod mechanism 2 includes a main push rod 21, a foot plate guide rod 22, a foot plate 23 and an elastic rod 24. The foot plate 23 is of a U-shaped structure. The bottom end of the elastic rod 24 is fixedly connected to one side of the foot plate 23. The foot plate guide rod 22 is fixedly connected to the other side of the foot plate 23. The foot plate guide rod 22 matches the chute 131. The main push rod 21 is internally provided with teeth 113. The main push rod 21 has upper and lower parts, and the two parts are connected through the cooperation of the internal teeth 113. One side of the main push rod 21 is provided with a groove 211 with a slope at one end. There are two grooves 211, and the two grooves 211 are adapted to the shaft structures on one side of the two internal gear disks 32. The bracket binding mechanism 1 includes a calf bracket 11, a thigh bracket 12, a foot fixator 13, a knee joint bearing 14 and an ankle joint bearing 15. First binding straps 101 are provided on both sides of the calf bracket 11. One end of the thigh bracket 12 is connected to the calf bracket 11 through the knee joint bearing 14, and second binding straps 121 are provided on both sides of the thigh bracket 12. The foot fixator 13 is of a U-shaped structure. Chutes 131 are provided at the tops of both sides of the foot fixator 13. Third binding straps 132 are provided between both sides and at the rear of the foot fixator 13. The ankle joint bearing 15 is fixedly connected to the top of one side of the foot fixator 13. The foot fixator 13 is connected to the calf bracket 11 through the ankle joint bearing 15. The knee joint bearing 14 is located at the top of the calf bracket 11, and the ankle joint bearing 15 is located at the bottom of the calf bracket 11. The calf bracket 11 includes an upper calf bracket 111 and a lower calf bracket 112. Teeth 113 are provided inside both the upper calf bracket 111 and the lower calf bracket 112. Corresponding through holes 114 are provided inside the upper calf bracket 111 and the lower calf bracket 112. The upper calf bracket 111 and the lower calf bracket 112 are connected through the cooperation of the teeth 113, and the upper calf bracket 111 and the lower calf bracket 112 are fastened by bolts passing through the internal through holes 114; the calf of the human body can be bound and fixed through the first binding straps 101, the thigh of the human body can be bound and fixed through the second binding straps 121, the foot of the human body can be bound and fixed by setting the third binding straps 132, and by setting the through holes 114 and bolts, the total length of the calf bracket 11 can be adjusted by adjusting the positions of the through holes 114 fixed by the bolts.

[0035] See Figure 6 , Figure 7 , Figure 11, there are two external gears 31, which are respectively fixed on the side walls of the calf bracket 11 and the foot fixator 13. Both sides of the internal gear disk 32 are provided with shaft structures. There are two internal gear disks 32, and the two internal gear disks 32 are respectively movably connected inside the ankle joint bearing 15 and the knee joint bearing 14 through the shaft structures on both sides. Communication holes matching the shaft structures on both sides of the internal gear disk 32 are opened inside the calf bracket 11 and the foot fixator 13. The spring energy storage and release mechanism 4 further includes a wire rope tube 45 and a wire rope tube fixator 46. There are two wire rope tubes 45, and the two wire rope tubes 45 are respectively sleeved on the side walls of the two wire ropes 44. One end of each of the two wire rope tubes 45 is fixedly connected inside the wire rope tube fixator 46, and the wire rope tube fixator 46 is fixedly connected to the side wall of the calf bracket 11. Threaded holes 412 are opened inside the spring chamber 41, and adjusting screws 43 are fixedly installed inside the threaded holes 412. There are several threaded holes 412. One end of each of the two wire ropes 44 is respectively connected to the side wall of the internal gear disk 32 inside the ankle joint bearing 15 and the internal gear disk 32 inside the knee joint bearing 14; by providing the threaded holes 412 and the adjusting screws 43 inside the spring chamber 41, when it is necessary to change the stiffness of the second spring 42, by adjusting the screwing degree of the adjusting screw 43 on the corresponding spring chamber 41, the fixed position of one end of the second spring 42 is changed, so as to change the stiffness of the second spring 42 to meet the energy storage requirements of different movements.

[0036] Refer to Figure 9 , the process of the passive knee-ankle exoskeleton realizing the clutch trigger action is as follows: when the foot leaves the ground, one side shaft of the internal gear disk 32 contacts the groove 211, and at this time, the internal and external gears in the clutch trigger mechanism 3 are in a separated state, and the joints where the clutch mechanism is located can rotate freely (such as Figure 9 (a)); when the foot touches the ground, the foot plate 23 moves upward to contact the lower surface of the foot fixator 13, and the main push rod 21 moves upward along the calf bracket 11 at the same time. At this time, one side shaft of the internal gear disk 32 moves from the communication hole of the calf bracket 11 to the outside of the groove 211, and the internal gear disk 32 moves along its axial direction, so that the internal and external gears in the clutch trigger system are engaged, and the rotation of the joints where the clutch system is located will drive the second spring 42 to store or release energy (such as Figure 9 (b)).

[0037] Refer to Figure 10 , the process of the elastic rod 24 of the passive knee-ankle exoskeleton realizing load bearing and bending is as follows: when the foot touches the ground, the foot plate 23 and the connected main push rod 21 move upward. At this time, the elastic rod 24 in the push rod mechanism 2 is subjected to a compressive load and plays a load-bearing role without bending deformation (such as Figure 10(a)); When the foot touches the ground and the ankle joint undergoes dorsiflexion movement, the angle between the foot sole plate 23 and its main push rod 21 becomes smaller. At this time, the T-shaped block 242 at the lower end and the elastic bracket 241 are separated, and the elastic rod 24 bends forward (as shown in Figure 10 (b)); When the foot touches the ground and the ankle joint undergoes plantar flexion movement, the angle between the foot sole plate 23 and its main push rod 21 becomes larger. At this time, the T-shaped block 242 at the upper end and the elastic bracket 241 are separated, and the elastic rod 24 bends backward (as shown in Figure 10 (c)).

[0038] The working process and principle of the present invention: First, the human body fixes the calf bracket 11, the thigh bracket 12 and the foot fixator 13 of the exoskeleton on the calf, thigh and foot segments of the human body respectively through the binding straps provided in the exoskeleton. When the foot touches the ground, the lower limb enters the support phase. The foot sole plate 23 moves upward to contact the lower surface of the foot fixator 13, and the main push rod 21 connected to the foot sole plate 23 moves upward along the calf bracket 11. The shaft on one side of the internal gear disk 32 in contact with it moves through the slope at one end of the groove 211 to the outside of the groove 211, so that the internal and external gears in the clutch trigger mechanism 3 are engaged. At the same time, the upward movement of the main push rod 21 directly drives the spring chamber 41 connected to it to move upward, and pulls the internal gear disk 32 at the knee joint and the ankle joint through the steel wire rope 44. Since the internal gear disk 32 cannot rotate forward under the action of its positioning screw 34, at this time, the two second springs 42 in the spring chamber 41 are simultaneously stretched and deformed to store strain energy (as shown in Figure 8 (a)). When the foot is fully in contact with the ground: the knee joint and the ankle joint respectively start to undergo flexion and dorsiflexion movements. By stretching the connected steel wire rope 44 through the engaged internal and external gears, the corresponding second spring 42 is further stretched to store strain energy (as shown in Figure 8 (b)). When the knee joint and the ankle joint respectively start to undergo extension and plantar flexion movements: the strain energy stored in the second spring 42 is released to assist in the completion of related actions. At this time, the elastic rod 24 at the ankle joint can be bent and deformed to keep the foot sole plate 23 in close contact with the foot fixator 13 (as shown in Figure 8 (c)). Subsequently, the foot starts to leave the ground. The main push rod 21 moves downward under the action of spring energy storage. The spherical end of the shaft of the internal gear disk 32 moves into the groove 211 on the main push rod 21 under the action of the first spring 33 between the internal and external gear parts 31, and the internal and external gears are separated. When the foot is completely off the ground, the lower limb is in the swing phase, and the internal and external gears are completely separated. At this time, the exoskeleton has no freedom of rotation in the flexion and extension directions at the knee joint and the ankle joint, avoiding interference with normal joint movements (as shown in Figure 8 (d)).

[0039] The above content is a further detailed description of the present invention in combination with specific embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as falling within the protection scope determined by the claims submitted for the present invention.

Claims

1. A passive knee and ankle assistive exoskeleton, characterized in that: it includes a bracket binding mechanism (1) for binding and fixing the human leg, a push rod mechanism (2) for achieving strong axial support and easy lateral bending, a clutch trigger mechanism (3) for regulating the free and restricted state of the joint, and a spring energy storage and release mechanism (4) for providing assistance; The spring energy storage and release mechanism (4) includes a spring chamber (41), a second spring (42) and a steel wire rope (44). Two pipes (411) matching the second spring (42) are provided inside the spring chamber (41). One end of the second spring (42) is fixedly installed at one end of the pipe (411). There are two second springs (42), and two steel wire ropes (44) are provided. The two steel wire ropes (44) are respectively fixedly connected to the bottoms of the two second springs (42); The clutch trigger mechanism (3) includes an external gear (31), an internal gear disk (32), a first spring (33) and a positioning screw (34). The external gear (31) is an incomplete gear. Internal teeth are provided inside the internal gear disk (32). The external gear (31) meshes with the internal teeth inside the internal gear disk (32). The positioning screw (34) is fixedly installed inside the internal gear disk (32). The first spring (33) is fixedly installed between the external gear (31) and the internal gear disk (32); The bracket binding mechanism (1) includes a calf bracket (11), a thigh bracket (12), a foot fixator (13), a knee joint bearing (14) and an ankle joint bearing (15). First binding straps (101) are provided on both sides of the calf bracket (11). One end of the thigh bracket (12) is connected to the calf bracket (11) through the knee joint bearing (14), and second binding straps (121) are provided on both sides of the thigh bracket (12). The foot fixator (13) is of a U-shaped structure. Chutes (131) are provided at the tops of both sides of the foot fixator (13). Third binding straps (132) are provided between both sides and at the rear of the foot fixator (13). The ankle joint bearing (15) is fixedly connected to the top of one side of the foot fixator (13). The foot fixator (13) is connected to the calf bracket (11) through the ankle joint bearing (15). The knee joint bearing (14) is located at the top of the calf bracket (11), and the ankle joint bearing (15) is located at the bottom of the calf bracket (11); The calf bracket (11) includes an upper calf bracket (111) and a lower calf bracket (112). Tooth teeth (113) are provided inside both the upper calf bracket (111) and the lower calf bracket (112). Corresponding through holes (114) are provided inside the upper calf bracket (111) and the lower calf bracket (112). The upper calf bracket (111) and the lower calf bracket (112) are connected by the cooperation of the tooth teeth (113), and the upper calf bracket (111) and the lower calf bracket (112) are fastened by bolts passing through the internal through holes (114). Two external gears (31) are provided. The two external gears (31) are respectively fixed on the side walls of the calf bracket (11) and the foot fixator (13). Shaft structures are provided on both sides of the internal gear disk (32). Two internal gear disks (32) are provided. The two internal gear disks (32) are respectively movably connected inside the ankle joint bearing (15) and the knee joint bearing (14) through the shaft structures on both sides. Communication holes matching the shaft structures on both sides of the internal gear disk (32) are provided inside the calf bracket (11) and the foot fixator (13). The push rod mechanism (2) includes a main push rod (21), a foot plate guide rod (22), a foot plate (23) and an elastic rod (24). The foot plate (23) is of a U-shaped structure. The bottom end of the elastic rod (24) is fixedly connected to one side of the foot plate (23). The foot plate guide rod (22) is fixedly connected to the other side of the foot plate (23). The foot plate guide rod (22) matches the sliding groove (131). Tooth teeth (113) are provided inside the main push rod (21). The main push rod (21) has upper and lower parts, and the two parts are connected by the cooperation of the internal tooth teeth (113). A groove (211) with a slope at one end is provided on one side of the main push rod (21). Two grooves (211) are provided, and the two grooves (211) are adapted to the shaft structures on one side of the two internal gear disks (32).

2. A passive knee and ankle joint assistive exoskeleton according to claim 1, characterized in that: The elastic rod (24) includes an elastic bracket (241) and a T-shaped block (242). The elastic bracket (241) is an S-shaped bracket. One end of the T-shaped block (242) is fixedly installed inside the elastic bracket (241) by screws. The elastic bracket (241) is fixedly installed between the main push rod (21) and the foot plate (23) by screws.

3. A passive knee and ankle joint assistive exoskeleton according to claim 1, characterized in that: One ends of the two steel wire ropes (44) are respectively connected to the side walls of the internal gear disks (32) inside the ankle joint bearing (15) and the internal gear disks (32) inside the knee joint bearing (14).

4. A passive knee and ankle joint assistive exoskeleton according to claim 1, characterized in that: The inside of the spring bin (41) is provided with threaded holes (412), and an adjusting screw (43) is fixedly installed inside the threaded holes (412), and a plurality of the threaded holes (412) are provided.

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