A new high-frequency signal test structure

Abstract

The present invention discloses a novel high-frequency signal test structure, including a single-head probe and a companion side plate, wherein the single-head probe is fixedly embedded in the companion side plate, the single-head probe includes a fixing part and a probe part, the fixing part includes a connecting part, a first ring body and a second ring body, the connecting part includes a first semi-ring column and a second semi-ring column, and a connecting mechanism and an adjusting mechanism are arranged inside the connecting part. In the present invention, the fixing part of the single-head probe is embedded in the companion side plate, and the spacing between the first semi-ring column and the second semi-ring column is adjusted by the coordinated use of the connecting mechanism and the adjusting mechanism, so that the height of the fixing part is the same as the height of the companion test plate, and the piece to be tested is lowered and fitted on the companion side plate by a moving mechanism, so that impedance discontinuity is avoided, and the test accuracy is improved to a certain extent. When the piece to be tested is pressed down, the single-head probe will not be positionally offset, and the test accuracy is improved to a certain extent, thereby realizing the continuity of impedance and accurately ensuring the test accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of high-frequency test fixtures, and in particular to a novel high-frequency signal test structure. Background Art

[0002] Test fixtures belong to a category under fixtures. They are a kind of fixtures specially used to test and experiment the functions, power calibration, life, performance, etc. of products. Because they are mainly used to test various indicators of products on the production line, they are called test fixtures. The current high-frequency test fixtures are roughly divided into two categories. One is the coaxial test head, which requires a test socket to be reserved on the RF line of the device under test. For example, for mobile phone RF testing and debugging, the RF test line is inserted into the test head. The test socket will connect the test head and the back end and disconnect. The signal only goes through the test line. When testing, you only need to use the fixture to fix the device under test, and use a movable part to align the test line with the test socket to realize fast testing. The other is the probe test. There are roughly two types of probe tests. One is a pogo pin with a welding seat at the bottom. One end is welded on the board and the other end can be extended. retractable; fast testing is achieved by moving the DUT up and down; the first test solution with a test socket requires adding a test socket to the high-frequency transmission line when the DUT is designed; it takes up space and is not conducive to miniaturization design; the test socket and test line are consumable parts with high cost, high requirements for test fixtures, and high test accuracy; the biggest disadvantage of the second probe solution is impedance mismatch. During the high-frequency signal test, it is necessary to ensure that the impedance in the test link is continuous and matched. There is a protruding fixed part of the probe in the middle. Since there is no reference ground, the impedance is discontinuous, which makes the test fluctuate greatly, and the test results are inconsistent and unstable.

[0003] The existing high-frequency test fixture technology has the following shortcomings: the coaxial high-frequency test fixture is expensive to use, has high requirements for the test fixture, and requires very high test accuracy. In the probe high-frequency test fixture, the impedance is not matched, the test fluctuation is large, the test result consistency is poor, and it is unstable. At the same time, when the probe solution is adopted, due to different test work, different specifications and sizes of the test pieces are encountered, and the single-head probe and the accompanying side plate used have different specifications and sizes, so it is necessary to purchase or make test probes of various specifications, which increases the test cost.

[0004] Therefore, it is necessary to invent a new type of high-frequency signal testing structure. Summary of the invention

[0005] To this end, the present invention provides a novel high-frequency signal testing structure, which adjusts the size of the fixing part by the coordinated use of a connecting mechanism and an adjusting mechanism, and embeds the fixing part of the single-head probe in the interior of the accompanying side plate. During the test, the piece to be tested is lowered and fitted onto the accompanying side plate by a moving mechanism, so that the piece to be tested forms an effect similar to that of being welded on the surface of the accompanying side plate, and the single-head probe is stably installed on the accompanying side plate, so as to solve the problems that the existing high-frequency test fixture has high cost in use, high requirements for the test fixture, impedance mismatch, large test fluctuation, poor consistency and instability of test results, and when a probe scheme is adopted, due to different test work, pieces to be tested of different specifications and sizes are encountered, and the specifications and sizes of the single-head probe and the accompanying side plate used are different, so it is necessary to purchase or manufacture test probes of various specifications, which increases the test cost.

[0006] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions: a novel high-frequency signal testing structure, comprising a single-head probe and a companion side plate, the single-head probe is fixedly embedded in the companion side plate, the single-head probe comprises a fixing part and a probe part, the top end of the fixing part is fixedly connected to the bottom end of the probe part, the fixing part comprises a connecting part, a first ring body and a second ring body, the first ring body and the second ring body are respectively arranged at both ends of the fixing part, and the first ring body and the second ring body are movably connected to the fixing part, the connecting part comprises a first semi-ring column and a second semi-ring column, and the first semi-ring column and the second semi-ring column are spliced ​​to form a connecting part of a complete annular hollow cylinder, a connecting mechanism and an adjusting mechanism are arranged inside the connecting part, the first semi-ring column and the second semi-ring column are movably connected through the connecting mechanism, and external threads are arranged on the outer surfaces of the first semi-ring column and the second semi-ring column.

[0007] Preferably, the first ring body and the second ring body match the connecting portion, the inner sides of the first half ring column and the second half ring column are respectively provided with external threads, the first ring body and the second ring body are respectively threadedly connected to the connecting portion, the first ring body and the second ring body are identically arranged, the first ring body includes the first half ring and the second half ring, and the first half ring and the second half ring are spliced ​​to form a completed first ring body, the first ring body and the second ring body are identically arranged, and the first ring body and the second ring body are rotated and adjusted along the direction of the connecting portion, and the first ring body and the second ring body are threadedly connected to the connecting portion to adjust the first ring body. The height positions of the first ring body and the second ring body on the connecting part make it possible for the complete fixing part composed of the first ring body, the second ring body and the connecting part on the single-head probe to be adjusted in height until the height of the fixing part is the same as the height of the accompanying test plate, and the fixing part of the single-head probe is embedded in the accompanying side plate. During the test, the piece to be tested is lowered and fitted onto the accompanying side plate through the moving mechanism, so that the piece to be tested forms an effect similar to that of being welded on the surface of the accompanying side plate, so that the single-head probe is stably installed on the accompanying side plate, and when the piece to be tested is pressed down, the single-head probe will not be shifted in position, thereby improving the test accuracy to a certain extent.

[0008] Preferably, two groups of connecting mechanisms are arranged inside the connecting part, and the two connecting mechanisms are symmetrically arranged, the connecting mechanism includes a first connecting block, a second connecting block and a first threaded rod, the first threaded rod is provided with two groups of threads in opposite directions, the first connecting block and the second connecting block are respectively threadedly connected to the first threaded rod, and the first connecting block and the second connecting block are respectively arranged on the two groups of threads in opposite directions on the first threaded rod, the first connecting block and the second connecting block are respectively matched with the first semi-ring column and the second semi-ring column, one side of the first connecting block is fixedly connected to the first semi-ring column, the second connecting block is fixedly connected to the second semi-ring column, the first threaded rod A gear is arranged at the upper center, and two groups of threads in opposite directions are arranged on the first threaded rod. When the first threaded rod rotates, the first connecting block and the second connecting block can move towards or away from each other. When the first connecting block and the second connecting block move away from each other, the first connecting block and the second connecting block provide power through the first threaded rod, and the first connecting block and the second connecting block push the first semi-ring column and the second semi-ring column to separate, so that the diameter of the fixing part increases. On the contrary, the first connecting block and the second connecting block approach each other, so that the diameter of the fixing part becomes smaller, and then the size specification of the fixing part can be adjusted so as to be suitable for single-head probes of different specifications and sizes required by different test pieces.

[0009] Preferably, the adjusting mechanism comprises an extending second threaded rod and an adjusting component, connecting columns are respectively provided at both ends of the second threaded rod, and the second threaded rod is fixedly connected to the connecting part through the adjusting component, and the adjusting component comprises a first telescopic rod and a second telescopic rod, one end of the first telescopic rod is fixedly connected to the inner side of the first semi-ring column, and the other end of the first telescopic rod is fixedly connected to the second threaded rod, one end of the second telescopic rod is fixedly connected to the inner side of the second semi-ring column, and the other end of the second telescopic rod is fixedly connected to the second threaded rod, and the second threaded rod in the adjusting mechanism can be rotated manually. Since the thread on the second threaded rod is in a meshing relationship with the gear on the first threaded rod, the first threaded rod can be rotated when the second threaded rod rotates, and the second threaded rod is fixedly connected to the fixing part through the adjusting component, and when the first semi-ring column and the second semi-ring column move away from each other, the first telescopic rod and the second telescopic rod in the adjusting mechanism extend, and when the first semi-ring column and the second semi-ring column approach each other, the first telescopic rod and the second telescopic rod show a tendency to reset, and then the second threaded rod is fixed to the inside of the fixing part through the first telescopic rod and the second telescopic rod.

[0010] Preferably, the first half ring and the second half ring are respectively provided with a first connecting groove and a second connecting groove at the connection point, and a first spring is arranged inside the first connecting groove, the first spring is fixedly connected to the first half ring, and a second spring is arranged inside the second connecting groove, the second spring is fixedly connected to the second half ring, the first spring and the second spring are respectively fixedly connected to the two ends of the arc rod, the first half ring and the second half ring are identically arranged, and when the spacing between the first half ring column and the second half ring column is adjusted, the first half ring and the second half ring are connected through the arc rod, the first spring and the second spring, and then the spacing between the first half ring and the second half ring can be manually stretched laterally, so that the first ring body and the second ring body are suitable for connecting parts with different diameters.

[0011] Preferably, two groups of adjustment components are provided on the second threaded rod, and the two groups of adjustment components are symmetrically arranged, so that the two groups of adjustment components can facilitate the connection of the threaded rod with the two groups of connection mechanisms to provide power therefor.

[0012] Preferably, the second threaded rod is meshedly connected to the gear, and the second threaded rod is connected to two sets of connecting mechanisms. The setting of the two sets of connecting mechanisms makes the connection between the first semi-ring column and the second semi-ring column more stable, improves the use effect during testing, and avoids testing errors or affecting the testing work.

[0013] Preferably, the accompanying side plate is fixedly connected above the test base, a piece to be tested and a moving mechanism are arranged on the accompanying side plate, the piece to be tested is fixedly connected to the adjustment mechanism, and the position of the piece to be tested corresponds to the position of the single-head probe on the accompanying side plate.

[0014] Preferably, curved portions are respectively provided on both sides of the first ring body, and a curved portion is provided on the bottom end of the second ring body. The curved portions provided on the first ring body and the second ring body facilitate fixing the fixing portion as a whole on the accompanying side panel to avoid scratches and damages to the accompanying side panel caused by the corners of the first ring body and the second ring body, while allowing the fixing portion as a whole to be smoothly embedded in the accompanying side panel.

[0015] The beneficial effects of the present invention are:

[0016] 1. In the present invention, the fixing part of the single-head probe is embedded in the accompanying side plate, and the first ring body and the second ring body are rotated and adjusted along the direction of the connecting part, so that the fixing part on the single-head probe can be adjusted in height. The height of the fixing part is the same as the height of the accompanying test plate. During the test, the piece to be tested is lowered and fitted on the accompanying side plate through the moving mechanism, so that the piece to be tested forms an effect similar to welding on the surface of the accompanying side plate, so that the single-head probe is stably installed on the accompanying side plate. When the piece to be tested is pressed down, the single-head probe will not be positionally shifted, which improves the test accuracy to a certain extent, and realizes that the use in the test process achieves the expected effect of the actual use process. At the same time, because the piece to be tested is fitted with the surface of the accompanying side plate, impedance discontinuity and large test fluctuations are avoided, thereby achieving impedance continuity and accurate test accuracy.

[0017] 2. In the present invention, the spacing between the first half-ring column and the second half-ring column is adjusted according to the size of the test piece actually used, that is, the size of the fixing part is adjusted by using the connecting mechanism and the adjusting mechanism in coordination, so as to adapt to the single-head probes of different specifications and sizes required by different test pieces, and the first ring body and the second ring body are stretched laterally until the first ring body and the second ring body meet the connection conditions with the fixing part, and then the first ring body and the second ring body are rotated so that the height of the fixing part on the single-head probe is equal to the height of the accompanying side plate, and the probe part to be used is selected, and the probe part is fixedly connected to the top of the second ring body, so that when encountering test pieces of different specifications and sizes, the single-head probe can meet the use requirements without the need to purchase or make again, thereby reducing the testing cost and improving the practicality, applicability and usability of the single-head probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the overall structure of a novel high-frequency signal testing structure provided by the present invention;

[0019] Figure 2 A schematic structural diagram of a connecting portion provided by the present invention;

[0020] Figure 3 A front view of the connecting portion provided by the present invention;

[0021] Figure 4 A schematic diagram of the internal structure of the connecting portion provided by the present invention;

[0022] Figure 5 A schematic diagram of the connection structure of the first half ring and the second half ring provided by the present invention;

[0023] Figure 6 The present invention provides Figure 4 The enlarged view of point A in the middle;

[0024] Figure 7A schematic diagram of the connection structure between the single-head probe and the accompanying side plate provided by the present invention;

[0025] In the figure: 1, accompanying side plate; 2, fixing part; 3, probe part; 4, connecting part; 5, first ring body; 6, second ring body; 7, first semi-ring column; 8, second semi-ring column; 9, external thread; 10, first semi-ring; 11, first connecting block; 12, second connecting block; 13, first threaded rod; 14, gear; 15, second threaded rod; 16, connecting column; 17, first telescopic rod; 18, second telescopic rod; 19, first connecting notch; 20, second connecting notch; 21, first spring; 22, second spring; 23, arc rod; 24, test base; 25, piece to be tested; 26, moving mechanism; 27, arc part; 28, second semi-ring. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] Example 1, refer to the attached Figure 1-2 A novel high-frequency signal test structure provided by the present invention comprises a single-head probe and a companion side plate 1, wherein the single-head probe is fixedly embedded in the companion side plate 1, the single-head probe comprises a fixing portion 2 and a probe portion 3, the top of the fixing portion 2 is fixedly connected to the bottom of the probe portion 3, the fixing portion 2 comprises a connecting portion 4, a first ring body 5 and a second ring body 6, the first ring body 5 and the second ring body 6 are respectively provided at both ends of the fixing portion 2, and the first ring body 5 and the second ring body 6 are movably connected to the fixing portion 2, the connecting portion 4 comprises a first semi-ring column 7 and a second semi-ring column 8, and the first semi-ring column 7 and the second semi-ring column 8 are spliced ​​to form a connecting portion 4 of a complete annular hollow cylinder, a connecting mechanism and an adjusting mechanism are arranged inside the connecting portion 4, the first semi-ring column 7 and the second semi-ring column 8 are movably connected through the connecting mechanism, and external threads 9 are arranged on the outer surfaces of the first semi-ring column 7 and the second semi-ring column 8.

[0028] Further, the first ring body 5 and the second ring body 6 match the connecting portion 4, the first half ring column 7 and the second half ring column 8 are respectively provided with external threads 9 on their inner sides, the first ring body 5 and the second ring body 6 are respectively threadedly connected to the connecting portion 4, the first ring body 5 and the second ring body 6 are identically arranged, the first ring body 5 includes a first half ring 10 and a second half ring 28, and the first half ring 10 and the second half ring 28 are spliced ​​to form a completed first ring body 5;

[0029] Furthermore, the first ring body 5 is provided with arc portions 27 on both sides, and the second ring body 6 is provided with an arc portion 27 at the bottom end;

[0030] See attached Figure 3-4, further, two groups of connecting mechanisms are arranged inside the connecting portion 4, and the two connecting mechanisms are symmetrically arranged, the connecting mechanism includes a first connecting block 11, a second connecting block 12 and a first threaded rod 13, the first threaded rod 13 is provided with two groups of threads in opposite directions, the first connecting block 11 and the second connecting block 12 are respectively threadedly connected to the first threaded rod 13, and the first connecting block 11 and the second connecting block 12 are respectively arranged on the two groups of threads in opposite directions on the first threaded rod 13, the first connecting block 11 and the second connecting block 12 are respectively matched with the first semi-ring column 7 and the second semi-ring column 8, one side of the first connecting block 11 is fixedly connected to the first semi-ring column 7, the second connecting block 12 is fixedly connected to the second semi-ring column 8, and a gear 14 is arranged at the center of the first threaded rod 13;

[0031] Further, the adjustment mechanism includes a second threaded rod 15 and an adjustment assembly, the two ends of the second threaded rod 15 are respectively provided with connecting columns 16, the second threaded rod 15 is fixedly connected to the connecting portion 4 through the adjustment assembly, and the adjustment assembly includes a first telescopic rod 17 and a second telescopic rod 18, one end of the first telescopic rod 17 is fixedly connected to the inner side of the first semi-ring column 7, the other end of the first telescopic rod 17 is fixedly connected to the second threaded rod 15, one end of the second telescopic rod 18 is fixedly connected to the inner side of the second semi-ring column 8, and the other end of the second telescopic rod 18 is fixedly connected to the second threaded rod 15;

[0032] See attached Figure 5 , further, the first half ring 10 and the second half ring 28 are respectively provided with a first connection slot 19 and a second connection slot 20, and the first connection slot 19 is provided with a first spring 21, the first spring 21 is fixedly connected to the first half ring 10, the second connection slot 20 is provided with a second spring 22, the second spring 22 is fixedly connected to the second half ring 28, and the first spring 21 and the second spring 22 are respectively fixedly connected to both ends of the arc rod 23;

[0033] Furthermore, two groups of adjustment components are arranged on the second threaded rod 15, and the two groups of adjustment components are symmetrically arranged;

[0034] See attached Figure 6 Furthermore, the second threaded rod 15 is meshedly connected with the gear 14, and the second threaded rod 15 is connected with two sets of connection mechanisms;

[0035] See attached Figure 7 Furthermore, the accompanying side plate 1 is fixedly connected above the test base 24, and a piece to be tested 25 and a moving mechanism 26 are provided on the accompanying side plate 1. The piece to be tested 25 is fixedly connected to the adjustment mechanism, and the position of the piece to be tested 25 corresponds to the position of the single-head probe on the accompanying side plate 1.

[0036] The use process of the present invention is as follows: when using the present invention, according to the size of the actual test piece 25, by rotating the second threaded rod 15, due to the meshing relationship between the second threaded rod 15 and the gear 14, when the second threaded rod 15 rotates, the first threaded rod 13 is driven to rotate, and the first threaded rod 13 rotates, and the first connecting block 11 and the second connecting block 12 are adjusted to move towards each other or away from each other, and the first connecting block 11 and the second connecting block 12 move away from each other to push the first half-ring column 7 and the second half-ring column 8 to separate, so that the size specification of the fixing part 2 can be adjusted to be suitable for single-head probes of different sizes required by different test pieces 25, and the first ring body 5 and the second ring body 6 are stretched laterally until the first ring body 5 and the second ring body 6 meet the connection conditions with the fixing part 2, and the first ring body 5 and the second ring body 6 are rotated and adjusted along the direction of the connecting portion 4, so that the fixing portion 2 on the single-head probe can be adjusted in height. The height of the fixing portion 2 is the same as the height of the accompanying test plate. The probe portion 3 to be used is selected, and the probe portion 3 is fixedly connected to the top of the second ring body 6. During the test, the piece to be tested 25 is lowered and fitted on the accompanying side plate 1 through the moving mechanism 26, so that the piece to be tested 25 forms an effect similar to welding on the surface of the accompanying side plate 1, so that the single-head probe is stably installed on the accompanying side plate 1. When the piece to be tested 25 is pressed down, the single-head probe will not be shifted in position, which improves the test accuracy to a certain extent. At the same time, since the piece to be tested 25 is fitted with the surface of the accompanying side plate 1, impedance discontinuity and large test fluctuations are avoided, thereby achieving impedance continuity and accurate test accuracy.

[0037] The above is only a preferred embodiment of the present invention. Any person skilled in the art may modify the present invention by using the above technical solution or modify it into an equivalent technical solution. Therefore, any simple modification or equivalent replacement made according to the technical solution of the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A high-frequency signal test structure, comprising a single-head probe and a side plate (1), characterized in that: The single-head probe is fixedly embedded in the side plate (1), and comprises a fixing part (2) and a probe part (3). The top end of the fixing part (2) is fixedly connected to the bottom end of the probe part (3). The fixing part (2) comprises a connecting part (4), a first ring body (5) and a second ring body (6). The first ring body (5) and the second ring body (6) are respectively arranged at two ends of the fixing part (2), and the first ring body (5) and the second ring body (6) are movably connected to the fixing part (2). The connecting part (4) comprises a first semi-ring column (7) and a second semi-ring column (8), and the first semi-ring column (7) and the second semi-ring column (8) are spliced ​​to form a connecting part (4) of a complete annular hollow cylinder. A connecting mechanism and an adjusting mechanism are arranged inside the connecting part (4). The first semi-ring column (7) and the second semi-ring column (8) are movably connected through the connecting mechanism, and external threads (9) are arranged on the outer surfaces of the first semi-ring column (7) and the second semi-ring column (8).

2. A high frequency signal testing structure according to claim 1, characterized in that: The first ring body (5) and the second ring body (6) match the connecting portion (4); the inner sides of the first half ring column (7) and the second half ring column (8) are respectively provided with external threads (9); the first ring body (5) and the second ring body (6) are respectively threadedly connected to the connecting portion (4); the first ring body (5) and the second ring body (6) are identically arranged; the first ring body (5) comprises a first half ring (10) and a second half ring (28); and a completed first ring body (5) is formed by splicing the first half ring (10) and the second half ring (28).

3. The high-frequency signal testing structure according to claim 1, characterized in that: Two groups of connection mechanisms are arranged inside the connection part (4), and the two connection mechanisms are symmetrically arranged. The connection mechanisms include a first connection block (11), a second connection block (12) and a first threaded rod (13). The first threaded rod (13) is provided with two groups of threads in opposite directions. The first connection block (11) and the second connection block (12) are respectively threadedly connected to the first threaded rod (13), and the first connection block (11) and the second connection block (12) are respectively arranged on the two groups of threads in opposite directions on the first threaded rod (13). The first connection block (11) and the second connection block (12) are respectively matched with the first semi-ring column (7) and the second semi-ring column (8). One side of the first connection block (11) is fixedly connected to the first semi-ring column (7), and the second connection block (12) is fixedly connected to the second semi-ring column (8). A gear (14) is arranged at the center of the first threaded rod (13).

4. The high-frequency signal testing structure according to claim 1, characterized in that: The adjustment mechanism comprises a second threaded rod (15) and an adjustment assembly, wherein two ends of the second threaded rod (15) are respectively provided with connecting columns (16), and the second threaded rod (15) is fixedly connected to the connecting portion (4) through the adjustment assembly, and the adjustment assembly comprises a first telescopic rod (17) and a second telescopic rod (18), wherein one end of the first telescopic rod (17) is fixedly connected to the inner side of the first semi-ring column (7), and the other end of the first telescopic rod (17) is fixedly connected to the second threaded rod (15), one end of the second telescopic rod (18) is fixedly connected to the inner side of the second semi-ring column (8), and the other end of the second telescopic rod (18) is fixedly connected to the second threaded rod (15).

5. The high-frequency signal testing structure according to claim 2, characterized in that: A first connection slot (19) and a second connection slot (20) are respectively provided at the connection point between the first half ring (10) and the second half ring (28), and a first spring (21) is arranged inside the first connection slot (19), the first spring (21) is fixedly connected to the first half ring (10), a second spring (22) is arranged inside the second connection slot (20), the second spring (22) is fixedly connected to the second half ring (28), and the first spring (21) and the second spring (22) are respectively fixedly connected to two ends of the arc rod (23).

6. A high frequency signal testing structure according to claim 4, characterized in that: The second threaded rod (15) is provided with two groups of adjustment components, and the two groups of adjustment components are symmetrically arranged.

7. A high frequency signal testing structure according to claim 4, characterized in that: The second threaded rod (15) is meshedly connected with the gear (14), and the second threaded rod (15) is connected to two sets of connection mechanisms.

8. The high-frequency signal testing structure according to claim 1, characterized in that: The accompanying side plate (1) is fixedly connected above the test base (24); a test piece (25) and a moving mechanism (26) are arranged on the accompanying side plate (1); the test piece (25) is fixedly connected to the adjustment mechanism, and the position of the test piece (25) corresponds to the position of the single-head probe on the accompanying side plate (1).

9. The high-frequency signal testing structure according to claim 1, characterized in that: The first ring body (5) is provided with curved portions (27) on both sides respectively, and the second ring body (6) is provided with a curved portion (27) at the bottom end.

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