Smart contact lens and embedded module thereof

Abstract

A smart contact lens (100) and an embedded module (2) thereof. The embedded module (2) includes an annular carrier plate (21), an electronic chip (22), a plurality of metal lines (23) formed on the annular carrier plate (21), and an encapsulation body (24), wherein the annular carrier plate (21) has a C-shaped section (211), two buffer sections (212) respectively connected to two ends of the C-shaped section (211), and a die-bonding section (213) connected between the two buffer sections (212); a stress-blocking groove (211a) is formed in a recessed manner on the outer edge of the annular carrier plate (21) between the C-shaped section (211) and each buffer section (212); and the electronic chip (22) is mounted on the die-bonding section (213) and is embedded in the encapsulation body (24). In the cross section of the embedded module (2), the die-bonding section (213) is linear, each buffer section (212) is circular-arc-shaped and has a first radius (R1), and the C-shaped section (211) is circular-arc-shaped and has a second radius (R2) that is greater than the first radius (R1). Therefore, stress caused by the electronic chip (22) and the encapsulation body (24) on the die-bonding section (213) can be effectively released by means of the two buffer sections (212) and the two stress-blocking grooves (211a).

Description

Smart contact lens and embedded module thereof TECHNICAL FIELD

[0001] The present application relates to a contact lens, in particular to a smart contact lens and an embedded module thereof. BACKGROUND

[0002] The existing smart contact lens is in the early stage of research and development and has not yet reached the stage of popularization. Therefore, the research and development of the existing smart contact lens is mostly focused on how to expand or increase its functions, but many technical details in production and manufacturing (such as stress dissipation) have not been emphasized. Therefore, the present inventors believe that the above-mentioned defects can be improved, and after careful research and application of scientific principles, the present application is finally proposed, which is a smart contact lens with reasonable design and effective improvement of the above-mentioned defects.

[0003] SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a smart contact lens and an embedded module thereof, which can effectively improve the defects that may be caused by the existing smart contact lens.

[0005] The embodiments of the present application disclose a smart contact lens, which comprises: a lens body comprising an optical part and a ring-shaped wearing part surrounding the optical part; wherein the lens body defines a central axis passing through the center of the optical part; an embedded module embedded in the ring-shaped wearing part, and the embedded module comprises: a ring-shaped carrier plate, which has a truncated cone shape and comprises a C-shaped section, two buffer sections respectively connected to the two ends of the C-shaped section, and a die bonding section connected between the two buffer sections; wherein the outer edge of the ring-shaped carrier plate is recessed to form a stress blocking groove between the C-shaped section and each buffer section connected thereto; an electronic chip mounted on the die bonding section; a plurality of metal lines formed on the ring-shaped carrier plate, and at least part of the plurality of metal lines are electrically coupled to the electronic chip through the ring-shaped carrier plate; a packaging body formed on the die bonding section and embedding the electronic chip therein; wherein in the cross section of the smart contact lens perpendicular to the central axis and passing through the electronic chip, the die bonding section is in a straight line shape, each buffer section has a buffer angle of 20-45 degrees with respect to the central axis, and each buffer section is in a circular arc shape and has a first radius, and the center of each buffer section does not fall on the central axis, and the C-shaped section is in a circular arc shape and has a second radius greater than the first radius.

[0006] Optionally, in the top view of the smart contact lens along the central axis, the smart contact lens defines a longitudinal axis passing through the central axis and the electronic chip and a transverse axis perpendicular to the longitudinal axis, so that the top view can be divided into a first quadrant, a second quadrant, a third quadrant and a fourth quadrant by the longitudinal axis and the transverse axis, and the two stress blocking grooves are respectively located in the third quadrant and the fourth quadrant.

[0007] Optionally, the outer edge of the annular carrier plate is concavely formed with two stress adjustment grooves at the C-shaped segment; in a top view, the two stress adjustment grooves are respectively located in the first quadrant and the second quadrant.

[0008] Optionally, in a top view, each stress blocking groove has a first angle less than the buffer angle and between 10 degrees and 30 degrees with respect to the central axis, and each stress adjustment groove has a second angle between 10 degrees and 80 degrees with respect to the central axis.

[0009] Optionally, the annular carrier plate is formed with a plurality of circular arc holes, each of which falls between any two adjacent metal lines, and the center of each circular arc hole falls on the central axis.

[0010] Optionally, the annular carrier plate is formed with a plurality of circular holes, and the width of each circular arc hole is not less than the diameter of any one of the circular holes; wherein the plurality of circular arc holes are arranged in a ring shape around the central axis, and at least one circular hole is arranged between any two circular arc holes arranged in a ring shape and adjacent to each other.

[0011] Optionally, the plurality of metal lines include: an antenna in a C shape and arranged along the inner edge of the annular carrier plate, and two end portions of the antenna are connected to the electronic chip at the die bonding segment; a plurality of sensing lines arranged outside the antenna and electrically coupled to the electronic chip.

[0012] Optionally, the antenna has a main body segment and two wing segments connected to the two ends of the main body segment, and the width of the main body segment is less than the width of any one of the wing segments, and the two wing segments each have two end portions; the annular carrier plate is formed with: two circular arc holes spaced apart from each other and arranged outside the main body segment in a ring shape; a plurality of circular holes between the two circular arc holes, and the width of each circular arc hole is not less than the diameter of any one of the circular holes.

[0013] Optionally, the plurality of metal lines include a plurality of structure reinforcement lines arranged outside the two circular arc holes in a ring shape and spaced apart from each other, and each structure reinforcement line does not have any electrical function.

[0014] The inner-embedded module of the smart contact lens comprises a ring-shaped carrier plate with a truncated cone-shaped outer contour and defining a central axis, the ring-shaped carrier plate having a C-shaped section, two buffer sections respectively connected to two ends of the C-shaped section, and a die bonding section connected between the two buffer sections; wherein a stress blocking groove is concavely formed between the C-shaped section and each buffer section connected thereto on the outer edge of the ring-shaped carrier plate; an electronic chip is mounted on the die bonding section; a plurality of metal lines are formed on the ring-shaped carrier plate, and at least part of the plurality of metal lines are electrically coupled to the electronic chip through the ring-shaped carrier plate; a packaging body is formed on the die bonding section and embeds the electronic chip therein; wherein in the cross section of the inner-embedded module perpendicular to the central axis and passing through the electronic chip, the die bonding section is linear, each buffer section has a buffer angle of 20-45 degrees with respect to the central axis, and each buffer section is circular arc-shaped and its center is not on the central axis, and each buffer section has a first radius, and the C-shaped section is circular arc-shaped and has a second radius greater than the first radius.

[0015] In summary, the smart contact lens and the inner-embedded module thereof disclosed in the embodiments of the present application can gradually disperse the stress concentration caused by the electronic chip and the packaging body to the die bonding section through the structural matching between the ring-shaped carrier plate and other components, and then release the stress through the two stress blocking grooves, thereby avoiding affecting the area where the plurality of metal lines are mainly distributed (such as the C-shaped section), so as to effectively improve the production yield and operation efficiency of the smart contact lens.

[0016] For a more complete understanding of the features and technical content of the present application, please refer to the following detailed description and drawings of the present application. However, these descriptions and drawings are only used to illustrate the present application, and do not limit the scope of protection of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 is a perspective view of a smart contact lens according to an embodiment of the present application.

[0018] Fig. 2 is a top view of the smart contact lens of Fig. 1, with the lens body omitted.

[0019] Fig. 3 is a cross-sectional view of Fig. 2 perpendicular to the central axis.

[0020] Fig. 4 is a cross-sectional view of Fig. 1 along the section line IV-IV.

[0021] Fig. 5 is a perspective view of another embodiment of the smart contact lens according to the present application.

[0022] Fig. 6 is a top view of the smart contact lens of Fig. 5, with the lens body omitted.

[0023] Fig. 7 is a cross-sectional view of Fig. 6 perpendicular to the central axis.

[0024] Fig. 8 is a perspective view of another embodiment of the smart contact lens of the present application.

[0025] Fig. 9 is a top view of the smart contact lens of Fig. 8, with the lens body omitted.

[0026] Fig. 10 is a cross-sectional view along the vertical central axis of Fig. 9. DETAILED DESCRIPTION

[0027] The following detailed description is presented to understand the disclosed embodiments of the present application, which are related to "smart contact lenses and modules embedded therein". The advantages and features of the present application can be understood from the following description. The present application can be implemented or applied in other different embodiments, and the details in the present description can be modified and changed based on different viewpoints and applications, without departing from the concept of the present application. In addition, the drawings of the present application are only simple schematic illustrations, and are not drawn according to the actual size, which is declared in advance. The following embodiments will further illustrate the related technical content of the present application, but the disclosed content is not intended to limit the protection scope of the present application.

[0028] It should be understood that although the terms "first", "second", "third", etc. can be used herein to describe various components or features, these components or features should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one feature from another feature. In addition, the term "or" used herein can include a combination of any one or more of the associated listed items, as appropriate.

[0029] Referring to Figs. 1 to 10, an embodiment of the present application is shown. As shown in Figs. 1 to 4, the present embodiment discloses a smart contact lens 100, which can be worn on the eye of a user or embedded in the eye (not shown in the drawings) according to design requirements, which is not limited by the present application.

[0030] Further, the smart contact lens 100 can have a function of correcting refractive error in the present embodiment, and the refractive error includes hyperopia, myopia, astigmatism, presbyopia, or astigmatism-presbyopia; or the smart contact lens 100 can be a makeup lens without correction function.

[0031] The smart contact lens 100 in the present embodiment includes a lens body 1 and an embedded module 2 embedded in the lens body 1. That is, the embedded module 2 is connected to the lens body 1 without a gap and is not exposed outside the lens body 1, so any hole formed by the embedded module 2 is also filled by the lens body 1.

[0032] In the present embodiment, the lens body 1 is formed by curing a hydrogel or a silicone hydrogel, and the hydrogel is, for example, p-HEMA, but is not limited thereto. The lens body 1 includes an optical part 11 and an annular wearing part 12 surrounding the optical part 11, and the optical part 11 can be designed to have or not have the function of correcting refractive errors.

[0033] Further, the lens body 1 defines a central axis L passing through the center of the optical part 11, that is, the center of the optical part 11 and the center of the annular wearing part 12 are located on the central axis L. The annular wearing part 12 is connected to the outer edge of the optical part 11 and is generally annular, and the embedded module 2 is embedded inside the annular wearing part 12. In addition, the production method of embedding the embedded module 2 in the annular wearing part 12 (or the manufacturing method of the smart contact lens 100) can be adjusted according to design requirements, which is not limited in the present application.

[0034] It should be additionally noted that the smart contact lens 100 in the present embodiment is described by the lens body 1 in combination with the embedded module 2, but the present application is not limited thereto. For example, in other embodiments not shown in the present application, the embedded module 2 can be used alone (such as sold) or in combination with other components according to actual needs.

[0035] In the present embodiment, the embedded module 2 includes an annular carrier plate 21, an electronic chip 22 mounted on the annular carrier plate 21, a plurality of metal lines 23 formed on the annular carrier plate 21, and a package 24 covering the electronic chip 22. In the present embodiment, the annular carrier plate 21 is described by a flexible printed circuit board (FPCB), and the thickness of the annular carrier plate 21 can be selected to be between 10 microns and 150 microns, and the high polymer material of the annular carrier plate 21 can include polyimide (PI) or liquid crystal polymer (LCP), but the present application is not limited thereto.

[0036] Further, the outer contour of the ring-shaped carrier plate 21 is in the shape of a truncated cone, and the ring-shaped carrier plate 21 has a C-shaped section 211, two buffer sections 212 respectively connected to two ends of the C-shaped section 211, and a die-bonding section 213 connected between the two buffer sections 212. In addition, the electronic chip 22 is mounted on the die-bonding section 213, and the package 24 is formed on the die-bonding section 213 and embeds the electronic chip 22 therein. A plurality of the metal lines 23 are formed on the ring-shaped carrier plate 21, and at least part of the plurality of the metal lines 23 are electrically coupled to the electronic chip 22 through the ring-shaped carrier plate 21.

[0037] It should be noted that, since the electronic chip 22 cannot be deformed, the package 24 is used to ensure that the electronic chip 22 can maintain its original configuration, but this will cause stress concentration on the ring-shaped carrier plate 21, thereby affecting the operation performance of the embedded module 2. Therefore, the ring-shaped carrier plate 21 can be optionally formed with at least part of the following features to facilitate reducing the stress concentration problem of the ring-shaped carrier plate 21.

[0038] In the embodiment, the outer edge 21a of the ring-shaped carrier plate 21 is recessed to form a stress blocking groove 211a between the C-shaped section 211 and each of the buffer sections 212 connected thereto. That is, the die-bonding section 213 and the two buffer sections 212 are located between the two stress blocking grooves 211a; or each of the stress blocking grooves 211a can also be regarded as a partial structure corresponding to the buffer section 212. In the embodiment, the two stress blocking grooves 211a have the same shape, and the two stress blocking grooves 211a are spaced apart from the die-bonding section 213 by the same distance, but the present application is not limited thereto.

[0039] Further, in the cross section of the smart contact lens 100 perpendicular to the central axis L and passing through the electronic chip 22 (as shown in FIG. 3), the die-bonding section 213 is in a straight line shape, each of the buffer sections 212 has a buffer angle σ212 of 20 degrees to 45 degrees with respect to the central axis L, and each of the buffer sections 212 is in a circular arc shape and has a first radius R1, and the center of each of the buffer sections 212 does not fall on the central axis L. The C-shaped section 211 is in a circular arc shape and has a second radius R2 greater than the first radius R1.

[0040] Therefore, the smart contact lens 100 in the present embodiment can gradually disperse the stress concentration caused by the electronic chip 22 and the package 24 to the solid crystal segment 213 through the structural matching between the annular carrier plate and other components, and then release the stress concentration by the two stress blocking grooves 211a, thereby avoiding affecting the area where a plurality of metal lines 23 are mainly distributed (such as the C-shaped segment 211). Furthermore, the opposite sides of the solid crystal segment 213 are respectively provided with two buffer segments 212 with a specific angle value, so as to more stably release the stress generated by the solid crystal segment 213.

[0041] From another angle, in the top view of the smart contact lens 100 along the central axis L (such as FIG. 2), the smart contact lens 100 defines a longitudinal axis Y passing through the central axis L and the electronic chip 22, and a transverse axis X perpendicular to the longitudinal axis Y, so that the top view can be divided into a first quadrant Q1, a second quadrant Q2, a third quadrant Q3 and a fourth quadrant Q4 by the longitudinal axis Y and the transverse axis X, and the two stress blocking grooves 211a are respectively located in the third quadrant Q3 and the fourth quadrant Q4.

[0042] Furthermore, the outer edge 21a of the annular carrier plate 21 is recessed to form two stress adjustment grooves 212a in the C-shaped segment 211, and the groove wall of each stress adjustment groove 212a can serve as a stress release path to effectively adjust the stress concentration generated by the pressure forming of the annular carrier plate 21 into a truncated cone shape and / or further release the force stress concentration generated by the formation of a plurality of metal lines 23 in the C-shaped segment 211.

[0043] In the top view, the two stress adjustment grooves 212a are respectively located in the first quadrant Q1 and the second quadrant Q2, each stress blocking groove 211a corresponds to the central axis L and has a first angle σ1 less than the buffer angle σ212 and between 10 degrees and 30 degrees, and each stress adjustment groove 212a corresponds to the central axis L and has a second angle σ2 between 10 degrees and 80 degrees, but the present application is not limited to the above.

[0044] The above is the stress release design of the annular carrier plate 21 on the outer edge 21a thereof, and the following describes other stress release designs of the annular carrier plate 21. Among them, the annular carrier plate 21 (such as the C-shaped segment 211) is formed with a plurality of through circular arc holes 214 and a plurality of circular holes 215, and a plurality of the circular arc holes 214 and a plurality of the circular holes 215 can be selected to fall between any two adjacent metal lines 23, so as to release the force stress concentration generated by the formation of a plurality of metal lines 23 in the C-shaped segment 211.

[0045] More specifically, the center of each of the arcuate holes 214 falls on the central axis L, and the plurality of arcuate holes 214 are arranged in a ring shape with the central axis L as the center. Among them, the width of each of the arcuate holes 214 is not less than the diameter of any one of the round holes 215, and each of the arcuate holes 214 has a central angle σ214 (such as 10 degrees to 80 degrees) of not more than 90 degrees with respect to the central axis L, and at least one of the round holes 215 is arranged between any two of the arcuate holes 214 arranged in a ring shape and adjacent to each other, but the present application is not limited thereto.

[0046] It should be additionally noted that the number and position of the plurality of arcuate holes 214 and the plurality of round holes 215 can be adjusted according to design requirements, thereby effectively improving the phenomenon of stress concentration. Furthermore, the plurality of arcuate holes 214 and the plurality of round holes 215 can also improve the oxygen permeability of the smart contact lens 100 to provide users with optional use experience.

[0047] In addition, the plurality of metal lines 23 in the present embodiment includes an antenna 231, a plurality of sensing lines 232 located outside the antenna 231, and a plurality of structure reinforcement lines 233 located outside the antenna 231, but the present application is not limited thereto. For example, in other embodiments not shown in the present application, the plurality of structure reinforcement lines 233 can also be omitted or replaced by other components according to design requirements.

[0048] The antenna 231 is in a C shape and is arranged along the inner edge 21b of the ring-shaped carrier plate 21, and the two end portions 2313 of the antenna 231 are located in the die bonding section 213 and connected to the electronic chip 22. In the present embodiment, the antenna 231 has a main body section 2311 and two wing sections 2312 connected to both ends of the main body section 2311, and the length of the main body section 2311 is greater than the length of any one of the wing sections 2312, the width of the main body section 2311 is less than the width of any one of the wing sections 2312, and the two wing sections 2312 each have two end portions 2313.

[0049] The plurality of sensing lines 232 is located outside the two wing sections 2312 of the antenna 231 and is electrically coupled to the electronic chip 22, and in Figures 1 to 4 of the present embodiment, the plurality of sensing lines 232 is mainly illustrated as being distributed in the third quadrant Q3 and the fourth quadrant Q4, but the specific structure and distribution of the plurality of sensing lines 232 can also be adjusted according to design requirements, and are not limited to Figures 1 to 4.

[0050] For example, as shown in FIGS. 5-10, each of the sensing lines 232 can also be distributed in a ring shape in the first quadrant Q1, the second quadrant Q2, the third quadrant Q3, and the fourth quadrant Q4, and the plurality of metal lines 23 omit the structural reinforcement lines 233, and as the distribution area of the plurality of sensing lines 232 increases, the ring-shaped carrier plate 21 can further add the arc-shaped holes 214 and the circular holes 215 according to design requirements.

[0051] In addition, as shown in FIGS. 1-4, the plurality of structural reinforcement lines 233 are located on the outside of the main body segment 2311 and arranged in a ring shape at intervals from each other, and each of the structural reinforcement lines 233 is only used for structural reinforcement in the embodiment but does not have any electrical function. Further, the plurality of structural reinforcement lines 233 are located on the outside of the two arc-shaped holes 214 at intervals from each other, and the two arc-shaped holes 214 are located on the outside of the main body segment 2311 at intervals from each other and arranged in a ring shape. That is, the plurality of structural reinforcement lines 233 and the main body segment 2311 are configured with two arc-shaped holes 214 (and a plurality of circular holes 215 located therebetween).

[0052] [Technical effects of the embodiment of the present application]

[0053] In summary, the smart contact lens and the embedded module thereof disclosed in the embodiment of the present application can be matched in structure between the ring-shaped carrier plate and other components, so that the stress concentration caused by the electronic chip and the package body to the die bonding segment can be gradually dispersed by the two buffer segments and then released by the two stress blocking grooves, thereby avoiding affecting the area where the plurality of metal lines are mainly distributed (such as the C-shaped segment), so as to effectively improve the production yield and operation efficiency of the smart contact lens.

[0054] The above disclosed content is only an optional and feasible embodiment of the present application, and does not limit the patent scope of the present application, so that any equivalent technical changes made according to the content of the specification and drawings of the present application are included in the patent scope of the present application.

Claims

1. An intelligent contact lens, characterized by, The smart contact lens comprises: a lens body comprising an optical portion and a ring-shaped wearing portion surrounding the optical portion; wherein the lens body defines a central axis passing through the center of the optical portion; and an embedded module embedded in the ring-shaped wearing portion, and the embedded module comprises: a ring-shaped carrier plate with a truncated cone-shaped outer contour and having a C-shaped segment, two buffer segments respectively connected to the two ends of the C-shaped segment, and a die bonding segment connected between the two buffer segments; wherein the outer edge of the ring-shaped carrier plate is recessed to form a stress blocking groove between the C-shaped segment and each of the buffer segments connected thereto; an electronic chip mounted on the die bonding segment; a plurality of metal lines formed on the ring-shaped carrier plate, and at least part of the plurality of metal lines are electrically coupled to the electronic chip through the ring-shaped carrier plate; and a package formed on the die bonding segment and embedding the electronic chip therein; wherein in the cross section of the smart contact lens perpendicular to the central axis and passing through the electronic chip, the die bonding segment is linear, each of the buffer segments corresponds to the central axis and has a buffer angle of 20-45 degrees, each of the buffer segments is circular arc-shaped and has a first radius, and the center of each of the buffer segments does not fall on the central axis, the C-shaped segment is circular arc-shaped and has a second radius greater than the first radius.

2. The smart contact lens of claim 1, wherein, In the top view of the smart contact lens along the central axis, the smart contact lens defines a longitudinal axis passing through the central axis and the electronic chip and a transverse axis perpendicular to the longitudinal axis, so that the top view can be divided into a first quadrant, a second quadrant, a third quadrant and a fourth quadrant by the longitudinal axis and the transverse axis, and the two stress blocking grooves are respectively located in the third quadrant and the fourth quadrant.

3. The smart contact lens of claim 2, wherein, The outer edge of the ring-shaped carrier plate is recessed to form two stress adjusting grooves in the C-shaped segment; in the top view, the two stress adjusting grooves are respectively located in the first quadrant and the second quadrant.

4. The smart contact lens of claim 3, wherein, In the top view, each of the stress blocking grooves corresponds to the central axis and has a first angle less than the buffer angle and between 10-30 degrees, and each of the stress adjusting grooves corresponds to the central axis and has a second angle between 10-80 degrees.

5. The smart contact lens of claim 1, wherein, The ring-shaped carrier plate is formed with a plurality of circular arc holes, each of the circular arc holes falls between any two adjacent metal lines, and the center of each of the circular arc holes falls on the central axis.

6. The smart contact lens of claim 5, wherein, The ring-shaped carrier plate is formed with a plurality of circular holes, and the width of each of the circular arc holes is not less than the diameter of any one of the circular holes; wherein the plurality of circular arc holes are arranged in a ring shape around the central axis, and at least one circular hole is arranged between any two circular arc holes arranged in a ring shape and adjacent to each other.

7. The smart contact lens of claim 1, wherein, The plurality of metal lines comprises: an antenna in a C shape and arranged along the inner edge of the ring-shaped carrier plate, and the two end portions of the antenna are located in the die bonding segment and connected to the electronic chip; and ​ A plurality of sensing lines are located outside the antenna and electrically coupled to the electronic chip.

8. The smart contact lens of claim 7, wherein, The antenna has a main body section and two wing sections connected to both ends of the main body section, and the width of the main body section is smaller than the width of any of the wing sections, and the two wing sections each have two end portions; the annular carrier plate is formed with: Two circular arc holes are located outside the main body section and arranged in a ring shape; and A plurality of circular holes are located between the two circular arc holes, and the width of each circular arc hole is not less than the diameter of any of the circular holes.

9. The smart contact lens of claim 8, wherein, The plurality of metal lines include a plurality of structural reinforcement lines located outside the two circular arc holes and arranged in a ring shape, and each structural reinforcement line does not have any electrical function.

10. An embedded module for smart contact lenses, characterized in that, The embedded module of the smart contact lens includes: An annular carrier plate has a truncated cone shape and defines an axis, the annular carrier plate has a C-shaped section, two buffer sections connected to the two ends of the C-shaped section, and a die bonding section connected between the two buffer sections; wherein the outer edge of the annular carrier plate is recessed to form a stress blocking groove between the C-shaped section and each buffer section connected thereto; An electronic chip is mounted on the die bonding section; A plurality of metal lines are formed on the annular carrier plate, and at least part of the plurality of metal lines are electrically coupled to the electronic chip through the annular carrier plate; and A package is formed on the die bonding section and embeds the electronic chip therein; In the cross section of the embedded module perpendicular to the axis and passing through the electronic chip, the die bonding section is linear, each buffer section has a buffer angle of 20-45 degrees with respect to the axis, and each buffer section is circular arc-shaped and its center does not fall on the axis, and each buffer section has a first radius, the C-shaped section is circular arc-shaped and has a second radius greater than the first radius.

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