A longitudinally-driven slotted ring underwater acoustic transducer

Abstract

The present invention relates to the technical field of underwater acoustic transducers, and particularly to a longitudinally-driven slotted ring underwater acoustic transducer, comprising: a slotted ring housing and a driving oscillator; the slotted ring housing is a ring-shaped cylinder, and a slit is provided along the longitudinal axis of its wall, and it is mirror-symmetrical along the section of the diameter where the slit is located, so that the slotted ring housing includes a mirror-symmetrical housing first arm and housing second arm; the slotted ring housing is provided with notches on its inner wall, the notches are mirror-symmetrical along the section of the diameter and are located at the connecting ends of the housing first arm and the housing second arm; the driving oscillator is installed in the notches and is used to drive the housing first arm and the housing second arm to perform expansion and contraction vibrations, so as to radiate acoustic energy into the medium. The present invention has extremely low stiffness, can design the resonance frequency in the ultra-low frequency band with a smaller size, has a wider applicable driving form, a faster response speed, and better linearity for high-power driving.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater acoustic transducers, and particularly to a longitudinally-driven slotted ring underwater acoustic transducer. Background Art

[0002] As is well known, the lower the acoustic wave frequency, the smaller the loss of its energy in the medium, and thus the farther the propagation distance in the ocean. In recent years, the demand for underwater acoustic wave emission in the ultra-low frequency band (20 Hz - 200 Hz) has gradually increased. The ultra-low frequency band is mainly applied to marine acoustics, including marine acoustic tomography, ocean temperature measurement, etc. At the same time, there are also special application requirements such as underwater transponders, underwater target interference, and platform active noise reduction.

[0003] At present, the sound sources in the ultra-low frequency band mainly include electromagnetic, electro-dynamic, moving-magnet transducers, as well as air guns, electric sparks, electromagnetic pulse sound sources, etc. Among them, air guns, electric sparks, and electromagnetic pulse sound sources belong to explosion sound sources. Their emitted sound waves are low-frequency broadband noises with high sound source levels, but the signals are not editable, and their application prospects are limited. Electromagnetic, electro-dynamic, and moving-magnet transducers belong to editable sound sources. They use electromagnetic force to drive the radiation surface to radiate sound waves into the medium. The advantages are that they can emit various forms of signals pre-edited in terms of function, have a low resonance frequency and a compact structure in terms of performance. However, the electromagnetic force-driven sound source has problems such as a long startup time, non-linearity of electromagnetic force, and unstable deep-water performance, which bring certain troubles to users.

[0004] For traditional underwater acoustic transducers such as flexural disk transducers, flextensional transducers, ring transducers, longitudinal vibration transducers and other resonant transducer technical approaches, it is difficult to achieve the emission ability in the ultra-low frequency band (20 Hz - 200 Hz) within a small size range. Since the intrinsic frequency of the resonant transducer is desired to reach the 20 Hz - 200 Hz frequency band range, its structural size will exceed the meter level, and for each reduction of a frequency doubling, the size will double, and the manufacturing difficulty will increase exponentially. Therefore, in the application of the ultra-low frequency band, it is extremely rare to use the traditional resonant transducer technical approach to achieve.

[0005] The slotted ring transducer is a resonant transducer that can be used in the ultra-low frequency range. Initially, the slotted ring transducer was formed by cutting an opening along the height direction on the ring wall of a conventional ring transducer. Researchers found that after the ring was cut, the structural stiffness was greatly reduced. Compared with other traditional transducers, at the same size scale, the resonant frequency could be reduced by 50-80%. Due to the limitations of the large-size ring ceramic firing process, as shown in the existing information at home and abroad (US8717849, US6678213, US5103130, CN 117460392 A), later slotted ring transducers almost all adopted the structural form of combining ceramic strips to inlay the ring with a slotted metal shell. This structural form of the slotted ring transducer cannot effectively apply prestress to the driving material, greatly reducing the high-power emission potential of the driving material. At the same time, it also limits the size and shape of the driving material to forms suitable for inlaying, such as long strips and square pieces. Summary of the Invention

[0006] The object of the present invention is to overcome the above-mentioned defects of the prior art, so as to provide a longitudinally-driven slotted ring underwater acoustic transducer. By using the longitudinal driving oscillator 2, the slotted ring shell is pushed to expand and contract through longitudinal telescopic vibration, so as to emit underwater sound waves that convert electrical energy into sound energy. The present invention realizes operation in the ultra-low frequency band with a small size, and has the capabilities of fast response and resonant emission.

[0007] To solve the above technical problems, the longitudinally-driven slotted ring underwater acoustic transducer provided by the technical solution of the present invention includes: a slotted ring shell and a driving oscillator, wherein,

[0008] The slotted ring shell is a ring-shaped cylinder, and a slit is provided along the longitudinal axis direction of its wall and is mirror-symmetrical along the section of the diameter where the slit is located, so that the slotted ring shell includes a shell first arm and a shell second arm that are mirror-symmetrical;

[0009] The slotted ring shell is provided with notches on its inner wall, and the notches are mirror-symmetrical along the section of the diameter and are located at the connection ends of the shell first arm and the shell second arm;

[0010] The driving oscillator is installed in the notch and is used to drive the shell first arm and the shell second arm to expand and contract, so as to radiate sound energy into the medium.

[0011] As an improvement of the above underwater acoustic transducer, the notch includes a first notch and a second notch. The first notch is located on the inner wall of the shell first arm, and the second notch is located on the inner wall of the shell second arm. The first notch and the second notch are mirror-symmetrical along the section of the diameter and are in a V shape.

[0012] As an improvement to the above underwater acoustic transducer, the notch is mirror-symmetrical along the section of the diameter in a linear shape and is located at the opposite position of the slit.

[0013] As an improvement to the above underwater acoustic transducer, the thickness of the first arm of the housing and the thickness of the second arm of the housing gradually decrease from the joint end to the slit end respectively.

[0014] As an improvement to the above underwater acoustic transducer, the driving oscillator includes: two transition blocks and a driving material located between the two transition blocks. Among them, the cross-section of the transition block is in a D shape; both sides of the notch are respectively provided with arc-shaped contact surfaces matching the D shape, and the notch also has a flat contact surface in contact with the driving material.

[0015] As an improvement to the above underwater acoustic transducer, the driving material includes at least one magnetostrictive material wrapped in a cylindrical shape by a waterproof material; the axial direction of the magnetostrictive material is perpendicular to the longitudinal axis direction. When multiple magnetostrictive materials are included, the multiple magnetostrictive materials are arranged along the longitudinal axis direction; among them, the magnetostrictive material includes: rare earth giant magnetostrictive material or iron-gallium alloy giant magnetostrictive material.

[0016] As an improvement to the above underwater acoustic transducer, the driving material includes at least one piezoelectric material wrapped in a strip shape by a waterproof material. The center line of the piezoelectric material is perpendicular to the longitudinal axis direction. When multiple piezoelectric materials are included, the multiple piezoelectric materials are arranged along the longitudinal axis direction and stacked to form a piezoelectric crystal stack; among them, the piezoelectric material includes: piezoelectric ceramic or relaxor ferroelectric single crystal.

[0017] As an improvement to the above underwater acoustic transducer, the material of the slit ring housing includes: metal, carbon fiber or polymer.

[0018] As an improvement to the above underwater acoustic transducer, the underwater acoustic transducer further includes: an internal support member and a sound-absorbing material; the internal support member is cylindrical, and its axis overlaps with the axis of the slit ring housing; the internal support member is located inside the slit ring housing, and the sound-absorbing material wraps the internal support member inside the slit ring housing and does not contact the slit ring housing.

[0019] As an improvement to the above underwater acoustic transducer, the underwater acoustic transducer further includes two suspension mounting members and a positioning key; among them, both ends of the internal support member respectively extend out of the slit ring housing; on the two end faces of the slit ring housing, housing connection parts are respectively arranged at the opposite positions of the slit; the suspension mounting members are in a disc shape and are provided with a hollowed-out area; the two suspension mounting members are respectively connected to both ends of the internal support member and are respectively connected to the housing connection parts through the positioning key, so that the first arm and the second arm of the housing are in a suspended state.

[0020] Compared with the prior art, the advantages of the present invention are as follows. A longitudinally-driven slotted ring underwater acoustic transducer of the present invention uses a magnetostrictive or electrostrictive material to longitudinally drive an oscillator to provide a driving force, and the slotted ring structure housing is forced to vibrate and radiate sound waves into the medium. The stiffness of the slotted ring housing is extremely low, and the resonant frequency can be designed in the ultra-low frequency band with a smaller size. Compared with traditional resonant transducers, it can work with a smaller size and lower frequency; the longitudinally-driven oscillator using magnetostrictive or electrostrictive materials has a shorter startup time, faster response speed, and more linear response signal compared with transducers driven by electromagnetic force; the longitudinally-driven oscillator driving the slotted ring structure has many advantages such as more diverse driving oscillator forms, simpler large-size assembly process, and easier application of prestress to the driving material compared with traditional piezoelectric ceramic segmented slotted rings. Description of the Drawings

[0021] Figure 1(a) is a schematic diagram of the main structure of a V-shaped driven slotted ring transducer;

[0022] Figure 1(b) is a schematic diagram of the main structure of a straight-shaped driven slotted ring transducer;

[0023] Figure 2(a) is a detailed diagram of the main vibration structure of the slotted ring transducer;

[0024] Figure 2(b) is a main diagram of the slotted ring transducer including internal components;

[0025] Figure 3(a) is an isometric side view of the whole transducer;

[0026] Figure 3(b) is a side view of the whole transducer.

[0027] Reference Signs in the Drawings

[0028] 1. Slotted ring housing 2. Driving oscillator 3. Transition block

[0029] 4. Driving material 5. Sound-absorbing material 6. Internal support member

[0030] 7. Housing connection part 8. Suspension mounting member 9. Positioning key Detailed Embodiments

[0031] The following further illustrates the technical solutions provided by the present invention in conjunction with embodiments.

[0032] The longitudinally-driven slotted ring underwater acoustic transducer provided in this embodiment has a main body part including a slotted ring housing 1 and a driving oscillator 2. In addition to the main body part, its auxiliary components include a piece of sound-absorbing material 5, an internal support member 6, two suspension mounting members 8, and two positioning keys 9. When the underwater acoustic transducer is working, an electrical signal is applied to the driving oscillator 2, driving the two arms of the slotted ring housing 1 to perform expansion and contraction vibrations, and radiating sound energy into the medium. This structure has the advantages of operating in the ultra-low frequency band, small size, simple process, high reliability, etc. It is especially suitable for being carried on a small platform for low-frequency noise simulation, and can also be installed in a space-limited position for active noise reduction of the platform.

[0033] The slotted ring housing 1 has an outer shape of an annular cylinder. When viewed from the end face, it is an annular structure with a cut slot somewhere along the circumference, and the whole housing is symmetric about the cut plane. The "V"-shaped slotted ring housing 1 has a cut notch at each of its left and right arms, and the midline of the notch of the "-"-shaped slotted ring housing 1 coincides with the symmetry plane. The processed notch is used to place the driving oscillator 2.

[0034] The driving oscillator 2 is composed of a driving material 4 and a transition block 3. The driving material can be divided into two categories. One category is magnetostrictive material, which is cylindrical in shape itself, and multiple cylindrical rods are arranged along the height direction of the housing. The other category is electrostrictive material, also called piezoelectric material. The piezoelectric material can be in the shape of a rectangular bar, and multiple pieces are stacked to form a piezoelectric crystal stack. The cross-section of the transition block 3 is similar to a "D" shape. The contact surface with the notch of the slotted ring housing 1 is an arc surface, and the contact surface with the active driving material 4 is a plane, which plays a role in transmitting the vibration force and vibration velocity excited by the active driving material 4 to the slotted ring housing 1.

[0035] The shape of the sound-absorbing material 5 is made into a special-shaped structure according to the inner contour line of the slotted ring housing 1, filling the inside as much as possible, but there should be a certain gap between the edge and the inner wall of the slotted ring to avoid affecting the vibration of the housing.

[0036] The internal support member 6 is cylindrical, with a height slightly greater than that of the slotted ring housing 1. After being wrapped with the sound-absorbing material 5 on the outside, it is inserted into the slotted ring housing 1, and threaded holes are provided at both ends for connecting the suspension mounting members 8.

[0037] The suspension mounting member 8 has an outer shape of a disc, with an outer diameter equivalent to that of the slotted ring housing 1. The inside is hollowed out for rapid inward water intake, and a certain thickness is designed to ensure stiffness and avoid bending under force.

[0038] This embodiment includes a set of longitudinally-driven oscillators 2 made of magnetostrictive or electrostrictive materials with faster response speed to provide driving force; it also includes a low-stiffness slotted-ring housing 1, which inlays the driving oscillator 2 in a reserved groove in a "V" shape or a "one" shape to form a slotted-ring main vibration structure with a resonant frequency in the ultra-low frequency band. It also includes auxiliary components such as a suspension mounting member 8, an internal support member 6, and an acoustic absorption material 5 to realize a transducer device with a suspension mounting function.

[0039] The longitudinally-driven oscillator 2 made of magnetostrictive or electrostrictive materials can be a single-rod or multi-rod longitudinal vibration-driven oscillator 2 composed of rare-earth giant magnetostrictive materials or iron-gallium alloy giant magnetostrictive materials, or it can also be a driving crystal stack formed by bonding electrostrictive materials such as piezoelectric ceramics and relaxor ferroelectric single crystals.

[0040] The low-stiffness slotted-ring housing 1 is an annular structure with a break in the middle. Its material can be metal, or non-metallic materials such as carbon fiber and polymer. Modern processing means are used to machine grooves in the ring body that can inlay the driving oscillator 2 to inlay the above-mentioned driving oscillator 2.

[0041] The low-stiffness slotted-ring housing 1 can be expanded by applying pressure to both arms of the housing, so that the length of the groove is extended. After inlaying the driving oscillator 2, the pressure on both arms is released, and the resilience of the housing is used to squeeze the driving oscillator 2 to provide prestress for it. Compared with the traditional ceramic structure slotted ring, this structure can more conveniently provide controllable prestress for the driving material, making the linear driving range of the transducer larger.

[0042] For the low-stiffness slotted-ring housing 1, the middle line position of both arms is the vibration node position. The displacement at this position is small under the vibration state of the housing, and the anti-external interference ability is strong, which can be used to install auxiliary components.

[0043] The suspension mounting members 8 are each set at the upper and lower end faces of the main vibration structure and are connected to the vibration node positions of the low-stiffness slotted-ring housing 1 by bolts. When designing the installation, a certain scale of gap should be reserved between the suspension mounting member 8 and the end face of the low-stiffness slotted-ring housing 1. This gap provides free mechanical boundary conditions for both arms of the low-stiffness slotted-ring housing 1 to avoid negative effects such as performance degradation and frequency deviation caused by changes in boundary conditions of the slotted-ring main vibration structure.

[0044] The internal support member 6 is placed inside the ring body and is connected between the two suspension mounting members 8 by bolts. Since the suspension mounting member 8 can only be installed at a single point at the node position of the housing and maintains a certain gap with the housing, a cantilever beam structure is formed, and the stiffness is relatively low. The internal support member 6 connects the two suspension mounting members 8 to form a four-point connection, improving the rigidity of the entire auxiliary mounting member and being beneficial to the overall installation and hoisting of the transducer.

[0045] The sound-absorbing material 5 can be a porous sound-absorbing material 5 or a resonant sound-absorbing material 5. Wrapping the material around the internal support member 6 and filling the inside of the ring body can achieve the effect of absorbing the in-ward sound energy of the slotted ring, thereby reducing the phenomenon of "acoustic short circuit" of the slotted ring and achieving the effect of improving the sound radiation ability of the slotted ring transducer.

[0046] This embodiment overcomes the problems of difficult prestress application and complex process of the traditional piezoelectric ceramic slotted ring, simplifies the prestress application method, and improves the process reliability.

[0047] This embodiment overcomes the problem of single driving element of the traditional piezoelectric ceramic slotted ring, provides a new structural form of applying the "longitudinal oscillator" to the slotted ring transducer, and expands the technical approach of applying more excellent driving elements such as rare earth giant magnetostrictive materials and relaxor ferroelectric single crystals to this structure.

[0048] This embodiment can be used to carry out low-frequency noise simulation on a small platform, or can be installed in a space-limited position for platform active noise reduction.

[0049] The following further describes this embodiment with reference to the accompanying drawings.

[0050] Referring to FIG. 1, the main structure of the slotted ring transducer can be "V"-shaped ( Figure 1a ) or "-"-shaped ( Figure 1b ), and its main structure is composed of a low-stiffness slotted ring housing 1 and a driving oscillator 2. Among them, the low-stiffness slotted ring housing 1 is circular in shape when viewed from the end face, and is designed as an open structure at a certain place along the circle. The whole housing is symmetric left and right, so that the slotted ring housing 1 includes a mirror-symmetric housing first arm and housing second arm.

[0051] The slotted ring housing 1 is provided with a notch on its inner wall. The notch is mirror-symmetric along the section of the diameter and is located at the connecting end of the housing first arm and the housing second arm; the driving oscillator 2 is installed in the notch for driving the housing first arm and the housing second arm to perform expansion and contraction vibration, so as to radiate sound energy into the medium.

[0052] The thicknesses of the housing first arm and the housing second arm gradually decrease from their connecting ends to the slotted ends. This design can reduce the co-vibration mass of the thicknesses of the housing first arm and the second arm, and further reduce the mechanical Q value, that is, the quality factor, thereby improving the bandwidth.

[0053] In one embodiment, the notch includes a first notch and a second notch. The first notch is located on the inner wall of the housing first arm, and the second notch is located on the inner wall of the housing second arm. The first notch and the second notch are mirror-symmetric along the section of the diameter and are in a "V" shape. The "V"-shaped slotted ring housing 1 is as Figure 1aAs shown. In another embodiment, the notch is symmetrically mirror-imaged along the section of the diameter in a straight line shape and is located at the opposite position of the slit. The "one"-shaped slit ring housing 1 is as Figure 1b shown.

[0054] The "V"-shaped slit ring housing 1 ( Figure 1a ) has a cutting notch at each of the left and right sides, and the center line of the notch of the "one"-shaped slit ring housing 1 ( Figure 1b ) coincides with the symmetry plane. The processed notch is used to place the driving oscillator 2.

[0055] Viewed from the end face direction, the driving oscillator 2 has a long strip shape. Its outer surface is coated with a watertight material, and the inside is an active driving material 4. The length of the driving oscillator 2 should be slightly longer than the notch length. By applying an outward pulling force to the two arms of the slit ring housing 1, the notch length can be increased. After inserting the driving oscillator 2 into the notch, release the pulling force of the two arms, and rely on the resilience of the material of the slit ring housing 1 to clamp the driving oscillator 2.

[0056] Referring to FIG. 2, FIG. 2(a) is a detailed view of the main vibration structure. The driving oscillator 2 is composed of two end transition blocks 3 and an internal active driving material 4. The contact surface between the transition block 3 and the notch of the slit ring housing 1 is an arc surface, and the contact surface with the internal active driving material 4 is a plane, which serves to transmit the vibration force and vibration velocity excited by the internal active driving material 4 to the slit ring housing 1; the internal active driving material 4 can be arranged in multiple groups in a cylindrical shape or can be a cuboid, and is designed according to the characteristics of the active material.

[0057] Referring to FIG. 2, FIG. 2(b) is the main body part including internal components, including a slit ring housing 1, a driving oscillator 2, a sound-absorbing material 5, an internal support member 6, and a housing connection part 7. Among them, the internal support member 6 is located at the center position of the main vibration structure of the slit ring transducer. The height of the internal support member 6 in the axial direction is higher than that of the slit ring housing 1 by a certain dimension; the sound-absorbing material 5 is made into a special-shaped structure along the inner shape of the slit ring housing 1, covers the outside of the internal support member 6, and keeps a certain distance from the inner wall of the slit ring housing 1 to avoid affecting the vibration of the housing; the housing connection part 7 is actually a keyway and is provided with two threaded holes for connecting and hanging the installation member 8.

[0058] Referring to FIG3 , the transducer as a whole includes a suspension mounting component 8 and a positioning key 9 in addition to the main structure. The suspension mounting component 8 is a fulcrum for external installation and hanging. It is positioned and connected through the positioning key 9 and the shell connection part 7 on the slit ring shell 1; the two suspension mounting components 8 on the two end surfaces are connected through the internal support component 6. The internal support component 6 is a certain size higher than the slit ring shell 1 in the axial direction, so that the two arms of the slit ring shell 1 are in a suspended state. In this way, when the slit ring transducer is working, the two arms of the slit ring shell 1 expand and contract under the telescopic drive of the driving vibrator 2, radiating sound energy outward, and the sound absorbing material 5 plays a role in absorbing the inward sound energy. The auxiliary structures such as the internal support component 6, the suspension mounting component 8, the positioning key 9 and the shell connection part 7 hardly vibrate, and play a role in external installation, hanging, and protecting the main structure.

[0059] Finally, it should be noted that the above examples are only used to illustrate the technical solutions 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 embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A longitudinally driven slotted annular underwater acoustic transducer, comprising: A slotted ring housing and a driving oscillator, wherein, The slotted ring housing is an annular cylinder, with a slot provided along the longitudinal axis of its wall and mirror-symmetrical about the plane of the diameter where the slot is located, so that the slotted ring housing includes a first housing arm and a second housing arm that are mirror-symmetrical; The slotted ring housing is provided with notches on its inner wall, the notches are mirror-symmetrical about the plane of the diameter and are located at the connecting ends of the first housing arm and the second housing arm; The driving oscillator is installed in the notches and is used to drive the first housing arm and the second housing arm to perform expansion and contraction vibrations, thereby radiating sound energy into the medium.

2. The longitudinally-driven slotted ring underwater acoustic transducer according to claim 1, wherein The notches include a first notch and a second notch, the first notch is located on the inner wall of the first housing arm, the second notch is located on the inner wall of the second housing arm, and the first notch and the second notch are mirror-symmetrical about the plane of the diameter and are in a V shape.

3. The longitudinally driven slotted ring underwater acoustic transducer according to claim 1, characterized in that, The notches are mirror-symmetrical about the plane of the diameter and are in a straight shape, and are located at positions opposite to the slot.

4. The longitudinally driven slotted ring underwater acoustic transducer according to claim 1, wherein The thicknesses of the first housing arm and the second housing arm gradually decrease from their connecting ends to the slot ends respectively.

5. The longitudinally-driven slotted ring underwater acoustic transducer according to claim 1, characterized in that, The driving oscillator includes: two transition blocks and a driving material located between the two transition blocks, wherein the cross-section of the transition block is in a D shape; Both sides of the notch respectively have arc-shaped contact surfaces matching the D shape, and the notch also has a flat contact surface in contact with the driving material.

6. The longitudinally driven slotted ring underwater acoustic transducer according to claim 5, characterized in that, The driving material includes at least one magnetostrictive material wrapped in a watertight material and in a cylindrical shape; the axial direction of the magnetostrictive material is perpendicular to the longitudinal axis direction. When there are multiple magnetostrictive materials, the multiple magnetostrictive materials are arranged along the longitudinal axis direction; wherein, The magnetostrictive material includes: rare earth giant magnetostrictive material or iron-gallium alloy giant magnetostrictive material.

7. The longitudinally driven slotted ring underwater acoustic transducer according to claim 5, wherein, The driving material includes at least one piezoelectric material wrapped in a watertight material and in a strip shape, the center line of the piezoelectric material is perpendicular to the longitudinal axis direction. When there are multiple piezoelectric materials, the multiple piezoelectric materials are arranged along the longitudinal axis direction and are stacked to form a piezoelectric crystal stack; wherein, The piezoelectric material includes: piezoelectric ceramic or relaxor ferroelectric single crystal.

8. The longitudinally-driven slotted ring underwater acoustic transducer according to claim 1, wherein The material of the slotted ring housing includes: metal, carbon fiber or polymer.

9. The longitudinally driven slotted ring underwater acoustic transducer according to claim 1, characterized in that, It further includes: An internal support member and an acoustic absorption material; the internal support member is in a cylindrical shape, and its axis overlaps with the axis of the slotted ring housing; The internal support member is located inside the slotted ring housing, the acoustic absorption material wraps the internal support member inside the slotted ring housing, and the acoustic absorption material does not contact the slotted ring housing.

10. The longitudinally driven slotted ring underwater acoustic transducer according to claim 9, characterized in that, It further includes two suspension mounting members and a positioning key; wherein, Both ends of the internal support member respectively extend out of the slotted ring housing; On the two end faces of the slotted ring housing, housing connection parts are respectively provided at positions opposite to the slot; The suspension mounting members are in a disc shape and are provided with hollowed-out areas; The two suspension mounting members are respectively connected to both ends of the internal support member and are respectively connected to the housing connection parts through the positioning key, so that the first housing arm and the second housing arm are in a suspended state.

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