Torsion test equipment for adjusting comfort degree and service life of VR (virtual reality) glasses headband

Abstract

The utility model relates to a testing device, and especially relates to a VR glasses headband comfort level adjusting and service life torsion testing device comprising a frame body, a test bench, a driving mechanism, a clamp, a pressure sensor, a torsion sensor and a placement seat; the placement seat and the frame body are arranged on the upper surface of the test board, and the placement seat is used for placing a headband to be tested; the pressure sensor is arranged on the placement seat and is used for sensing the pressure of the to-be-measured headband on the placement seat; the driving mechanism is movably connected with the frame body along a first direction, the clamp is connected to an output end of the driving mechanism, and the clamp is used for clamping an adjusting knob on the to-be-tested headband; when the clamp clamps an adjusting knob on the to-be-tested headband, the driving mechanism can provide torque for the clamp, so that the clamp drives the adjusting knob to rotate; the torsion sensor is used for measuring the torque borne by the clamp when the clamp clamps the adjusting knob. According to the utility model, the torsion performance of the to-be-tested head band can be tested.

Description

A torque testing device for adjusting the comfort and lifespan of VR glasses headbands Technical Field

[0001] This utility model belongs to the field of testing equipment, and in particular relates to a torque testing device for adjusting the comfort and service life of VR glasses headbands. Background Technology

[0002] Comfort is a key factor affecting user experience in virtual reality (VR) headsets. As the primary contact component between the headset and the human body, the headband needs to be designed to provide stability while ensuring a reasonable distribution of pressure on the head, preventing fatigue or discomfort from prolonged wear. Currently, VR headbands commonly employ elastic compression structures (such as elastic fabrics, adjustable elastic bands, or mechanical buckles) to quickly adapt to different head shapes.

[0003] The headband needs to apply sufficient pressure to secure the headset and prevent it from slipping, but excessive local pressure (such as on the forehead, temples, or occiput) can cause pressure pain for the user. Existing headbands are often designed based on empirical parameters, lacking detailed analysis of different head shapes and pressure-sensitive areas, and lacking testing equipment for the torsional performance of headbands in design prototypes. Summary of the Invention

[0004] The technical problem to be solved by this utility model is that existing headbands often rely on empirical parameters in their design, lack detailed analysis of different head shapes and pressure-sensitive areas, and lack testing equipment for the performance of headbands of designed samples. This utility model provides a torque testing device for the comfort adjustment and service life of VR glasses headbands.

[0005] To address the aforementioned issues, this utility model provides a torque testing device for adjusting the comfort and lifespan of VR glasses headbands, comprising a frame, a test platform, a drive mechanism, a clamp, a pressure sensor, a torque sensor, and a mounting base.

[0006] The mounting base and the frame are disposed on the upper surface of the test bench, and the mounting base is used to place the headband to be tested;

[0007] The pressure sensor is disposed on the mounting base and is used to sense the pressure of the headband under test on the mounting base;

[0008] The drive mechanism is movably connected to the frame in a first direction, and the clamp is connected to the output end of the drive mechanism. The clamp is used to hold the adjustment knob on the headband to be tested. When the clamp holds the adjustment knob on the headband to be tested, the drive mechanism can provide torque to the clamp so that the clamp drives the adjustment knob to rotate.

[0009] The torque sensor is used to measure the torque that the clamp experiences when holding the adjustment knob.

[0010] Optionally, the mounting base includes a base and a floating element, the base is disposed on the test bench, the floating element and the base are spaced apart, and the surface of the floating element away from the base is adapted to contact the headband to be tested;

[0011] The pressure sensor is disposed between the substrate and the floating component to sense the pressure exerted by the headband under test on the floating component.

[0012] Optionally, the mounting base further includes a first locking plate and a second locking plate. The first locking plate is disposed on one side of the base in a first direction. A first magnetic suction element is disposed on the first locking plate, and a first ferromagnetic element is disposed on the base. The first magnetic suction element and the first ferromagnetic element are magnetically attracted to each other. When the first magnetic suction element and the first ferromagnetic element are magnetically attracted to each other, the first locking plate and the base clamp the top end of the headband to be tested.

[0013] The second locking plate is disposed on the other side of the first direction of the substrate. The second locking plate is provided with a second magnetic suction element, and the substrate is provided with a second ferromagnetic element. The second magnetic suction element and the second ferromagnetic element are magnetically attracted to each other. When the second magnetic suction element and the second ferromagnetic element are magnetically attracted to each other, the second locking plate and the substrate clamp the bottom end of the headband to be tested.

[0014] Optionally, the first locking plate is provided with at least two mutually spaced first guide rods, and the base is provided with at least two first guide holes, the first guide holes and the first guide rods are one-to-one, and the first guide rods can be inserted into the corresponding first guide holes;

[0015] The second locking plate is provided with at least two mutually spaced second guide rods, and the base is provided with at least two second guide holes. The second guide rods and the second guide holes correspond one-to-one, and the second guide rods can be inserted into their corresponding second guide holes.

[0016] Optionally, a first protrusion is provided on the side of the first locking plate near the base, and the first protrusion is used to insert into the through hole at the top end of the headband to be tested;

[0017] A second protrusion is provided on the side of the second locking plate near the base, and the second protrusion is used to insert into the through hole at the bottom end of the headband to be tested.

[0018] Optionally, the mounting base further includes a support and a two-dimensional moving platform, one end of the support is connected to the two-dimensional moving platform, and the other end of the support is connected to the base;

[0019] The two-dimensional mobile platform is disposed on the test platform, and the two-dimensional mobile platform is capable of driving the support to move relative to the test platform along the second direction and the third direction.

[0020] Wherein, the first direction, the second direction, and the third direction are perpendicular to each other.

[0021] Optionally, it also includes a lifting mechanism, through which the drive mechanism is movably connected to the frame.

[0022] Optionally, the drive mechanism includes a mounting frame, a motor, a first synchronous pulley, a second synchronous pulley, a synchronous belt, and a transmission rod. The mounting frame is connected to the lifting mechanism, the motor is connected to the mounting frame, the first synchronous pulley is connected to the output end of the motor, the transmission rod is rotatably assembled with the mounting frame, the second synchronous pulley is connected to the transmission rod, the synchronous belt is wound around the first and second synchronous pulleys, and the torque sensor is connected between the transmission rod and the clamp.

[0023] Optionally, the clamp includes a pneumatic finger, a first clamp, and a second clamp. The pneumatic finger is connected to the pressure sensor, and the first clamp and the second clamp are respectively connected to the pneumatic finger, so that the pneumatic finger can drive the first clamp and the second clamp to move closer to or further away from each other.

[0024] Optionally, the first clamp is provided with a plurality of mutually spaced first grooves, the first grooves being used for the protrusions of the adjustment knob to be inserted;

[0025] The second clamp is provided with a plurality of mutually spaced second grooves, which are used for the protrusions of the adjustment knob to be inserted.

[0026] This utility model provides a torque testing device for adjusting the comfort and lifespan of VR glasses headbands. The headband to be tested is installed on a mounting base. Then, a drive mechanism and its clamp are moved downwards, causing the clamp to grip the adjustment knob of the headband. The drive mechanism is activated, applying torque to the clamp to rotate it. This, in turn, causes the adjustment knob to rotate. The direction of rotation (counterclockwise or clockwise) determines whether the headband is tightened or loosened. As the headband changes tension, it applies pressure to a pressure sensor on the mounting base, thus measuring the relationship between torque and pressure. This allows researchers to improve the headband based on this relationship. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 is an overall schematic diagram of the torque testing device for adjusting the comfort and service life of VR glasses headbands provided in one embodiment of the present invention.

[0029] Figure 2 is a schematic diagram showing the positions of the mounting base and drive mechanism of the torque testing device for VR glasses headband comfort adjustment and service life provided in one embodiment of the present invention.

[0030] Figure 3 is an exploded view of the mounting base of the torque testing device for adjusting the comfort and service life of VR glasses headbands provided in one embodiment of the present invention.

[0031] Figure 4 is a schematic diagram of the fixture of the torque testing device for VR glasses headband comfort adjustment and service life provided in one embodiment of the present invention.

[0032] The reference numerals in the accompanying drawings are as follows:

[0033] 1. Test stand; 2. Mounting base; 21. Base; 211. First guide hole; 212. First ferromagnetic component; 22. Floating component; 23. First locking plate; 24. Second locking plate; 25. Two-dimensional moving platform; 26. Bracket; 27. Second magnetic suction component; 28. Second guide rod; 29. ​​Second protrusion; 3. Drive mechanism; 31. Mounting bracket; 32. Motor; 33. First synchronous pulley; 34. Second synchronous pulley; 36. Transmission rod; 4. Pressure sensor; 5. Clamp; 51. Pneumatic finger; 51. First chuck; 52. Second chuck; 53. First groove; 6. Torque sensor; 7. Frame; 8. Lifting mechanism; 9. Headband to be tested; 91. Adjustment knob; 92. Belt body; 93. Through hole. Detailed Implementation

[0034] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0035] In the description of this utility model, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0037] As shown in Figures 1 to 4, an embodiment of this utility model provides a torque testing device for adjusting the comfort and lifespan of a VR glasses headband. Referring specifically to Figures 1 and 2, the device includes a frame 7, a test platform 1, a drive mechanism 3, a clamp 5, a pressure sensor 4, a torque sensor 6, and a mounting base 2. The mounting base 2 and the frame 7 are disposed on the upper surface of the test platform 1. The mounting base 2 is used to place the headband 9 to be tested. The pressure sensor 4 is disposed on the mounting base 2 and is used to sense the pressure exerted by the headband 9 on the mounting base 2. The drive mechanism 3 is movably connected to the frame 7 along a first direction. The clamp 5 is connected to the output end of the drive mechanism 3 and is used to clamp the adjustment knob 91 on the headband 9. When the clamp 5 clamps the adjustment knob 91 on the headband 9, the drive mechanism 3 can provide torque to the clamp 5 to drive the adjustment knob 91 to rotate. The torque sensor 6 is used to measure the torque borne by the clamp 5 when it clamps the adjustment knob 91. In this embodiment, the first direction is the up-down direction.

[0038] In this embodiment, the headband 9 to be tested is installed on the mounting base 2. Then, the drive mechanism 3 and its clamp 5 are moved downwards, so that the clamp 5 clamps the adjustment knob 91 of the headband 9. The drive mechanism 3 is activated, and the drive mechanism 3 applies torque to the clamp 5 to drive the clamp 5 to rotate. In turn, the clamp 5 drives the adjustment knob 91 to rotate. The direction of rotation of the clamp 5 (counterclockwise or clockwise) determines whether the headband 9 is tightened or loosened. When the headband 9 changes its tightness, it applies pressure to the pressure sensor 4 on the mounting base 2, thereby measuring the relationship between torque and pressure. This allows the experimenter to improve the headband 9 based on the relationship between torque and pressure, thereby improving the comfort adjustment effect of the headband.

[0039] Referring to Figure 3, in one embodiment, the mounting base 2 includes a base 21 and a floating element 22. The base 21 is disposed on the test platform 1, and the floating element 22 and the base 21 are spaced apart. The surface of the floating element 22 away from the base 21 is adapted to contact the headband 9 to be tested. The pressure sensor 4 is disposed between the base 21 and the floating element 22 to sense the pressure exerted by the headband 9 on the floating element 22. In this embodiment, the shape of the floating element 22 is modeled after a human head, so that the headband 9 to be tested fits the outer surface of the floating element 22, thus making the test results closer to reality. Since the headband 9 to be tested in this embodiment includes two bands 92, two floating elements 22 are also provided in this embodiment, and two pressure sensors 4 are also provided, with one pressure sensor 4 installed between each floating element 22 and the base 21.

[0040] When the floating element 22 is subjected to pressure from the headband 9 to be tested, it moves closer to the base 21, thereby squeezing the pressure sensor 4 located between the base 21 and the floating element 22. The pressure sensor 4 measures the pressure of the floating element 22.

[0041] In one embodiment, the mounting base 2 further includes a first locking plate 23 and a second locking plate 24. The first locking plate 23 is disposed on one side of the base 21 in a first direction. A first magnetic attracting element is disposed on the first locking plate 23, and a first ferromagnetic element 212 is disposed on the base 21. The first magnetic attracting element and the first ferromagnetic element 212 are magnetically attracted. When the first magnetic attracting element and the first ferromagnetic element 212 are magnetically attracted, the first locking plate 23 and the base 21 clamp the top end of the headband 9 to be tested.

[0042] The second locking plate 24 is disposed on the other side of the base 21 in the first direction. The second locking plate 24 is provided with a second magnetic suction member 27, and the base 21 is provided with a second ferromagnetic member. The second magnetic suction member 27 and the second ferromagnetic member are magnetically attracted. When the second magnetic suction member 27 and the second ferromagnetic member are magnetically attracted, the second locking plate 24 and the base 21 clamp the bottom end of the headband 9 to be tested.

[0043] In this embodiment, the first locking plate 23 and the second locking plate 24 are detachably connected to the base 21 by magnetic attraction. Before installing the headband 9 to be tested, the first locking plate 23 and the second locking plate 24 are separated from the base 21, the headband 9 to be tested is installed on the base 21, and then the first locking plate 23 and the second locking plate 24 are connected to the base 21 in sequence, so that the first locking plate 23 and the base 21 clamp the top end of the headband, and the second locking plate 24 and the base 21 clamp the bottom end of the headband, thus completing the fixation of the headband 9 to be tested.

[0044] In one embodiment, the first locking plate 23 is provided with at least two mutually spaced first guide rods, and the base 21 is provided with at least two first guide holes 211, the first guide holes 211 and the first guide rods are one-to-one, and the first guide rods can be inserted into their corresponding first guide holes 211; the second locking plate 24 is provided with at least two mutually spaced second guide rods 28, and the base 21 is provided with at least two second guide holes, the second guide rods 28 and the second guide holes are one-to-one, and the second guide rods 28 can be inserted into their corresponding second guide holes.

[0045] In this embodiment, the cooperation between the first guide rod and the first guide hole 211 restricts the arbitrary movement of the first locking plate 23, which has clamped the headband 9 to be tested, thus ensuring that the first locking plate 23 stably clamps the headband 9 to be tested. Similarly, the cooperation between the first guide rod and the first guide hole 211 restricts the arbitrary movement of the second locking plate 24, which will not be elaborated further.

[0046] In one embodiment, a first protrusion is provided on the side of the first locking plate 23 near the base 21, and the first protrusion is used to insert into the through hole 93 at the top end of the headband 9 to be tested; a second protrusion 29 is provided on the side of the second locking plate 24 near the base 21, and the second protrusion 29 is used to insert into the through hole 93 at the bottom end of the headband 9 to be tested. As can be seen from the accompanying drawings, the top and bottom ends of the headband 9 to be tested in this embodiment are respectively provided with through holes 93. Therefore, when the first locking plate 23 presses the headband 9 to be tested, the headband 9 to be tested is fixed a second time by inserting the first protrusion and the second protrusion 29 into their respective through holes 93, thereby reducing the occurrence of displacement of the headband 9 to be tested during testing.

[0047] In one embodiment, the mounting base 2 further includes a support 26 and a two-dimensional moving platform 25. One end of the support 26 is connected to the two-dimensional moving platform 25, and the other end of the support 26 is connected to the base 21. The two-dimensional moving platform 25 is disposed on the test bench 1 and can drive the support 26 to move relative to the test bench 1 along a second direction and a third direction. The first direction, the second direction, and the third direction are perpendicular to each other. In this embodiment, the two-dimensional moving platform 25 is used to displace the base 21 before testing, so that the base 21 is located directly below the clamp 5.

[0048] In one embodiment, the torque testing device for adjusting the comfort and lifespan of VR glasses headbands further includes a lifting mechanism 8, and the drive mechanism 3 is movably connected to the frame 7 via the lifting mechanism 8. The lifting mechanism 8 is a slide table.

[0049] Referring to Figure 2, in one embodiment, the drive mechanism 3 includes a mounting frame 31, a motor 32, a first synchronous pulley 33, a second synchronous pulley 34, a synchronous belt, and a transmission rod 36. The mounting frame 31 is connected to the lifting mechanism 8, the motor 32 is connected to the mounting frame 31, the first synchronous pulley 33 is connected to the output end of the motor 32, the transmission rod 36 is rotatably assembled with the mounting frame 31, the second synchronous pulley 34 is connected to the transmission rod 36, the synchronous belt is wound around the first synchronous pulley 33 and the second synchronous pulley 34, and the torque sensor 6 is connected between the transmission rod 36 and the clamp 5. In this embodiment, the first synchronous pulley 33, the second synchronous pulley 34, and the synchronous belt constitute a synchronous belt mechanism. The synchronous belt mechanism has a better transmission effect and is less prone to slippage compared to a belt drive mechanism. The motor 32 drives the transmission rod 36 to rotate through the synchronous belt mechanism, and the transmission rod 36 drives the torque sensor 6 and the clamp 5 to rotate.

[0050] Referring to Figures 2 and 4, in one embodiment, the clamp 5 includes a pneumatic finger 51, a first clamp 51, and a second clamp 52. The pneumatic finger 51 is connected to the pressure sensor 4. The first clamp 51 and the second clamp 52 are respectively connected to the pneumatic finger 51, so that the pneumatic finger 51 can drive the first clamp 51 and the second clamp 52 to move closer to or further away from each other. The first clamp 51 is provided with a plurality of mutually spaced first grooves 53 for the protrusions of the adjustment knob 91 to be inserted. The second clamp 52 is provided with a plurality of mutually spaced second grooves for the protrusions of the adjustment knob 91 to be inserted.

[0051] In this embodiment, the adjustment knob 91 is generally cylindrical, and its surface is integrally formed with multiple spaced protrusions. These protrusions prevent the knob from slipping when rotated. Therefore, the first clamp 51 in this embodiment is provided with a first groove 53 to engage with the protrusions of the adjustment knob 91 to avoid slippage. Similarly, the second groove on the second clamp 52 is described in detail.

[0052] The torque testing device for adjusting the comfort and lifespan of VR glasses headbands described in this embodiment can also be used in lifespan testing experiments. By repeatedly contracting and relaxing the headband until it reaches its fatigue limit, the fatigue life of the headband can be determined based on the number of repeated experiments.

[0053] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. A torque testing device for adjusting the comfort and lifespan of VR glasses headbands, characterized in that, The device includes a frame, a test bench, a drive mechanism, a clamp, a pressure sensor, a torque sensor, and a mounting base. The mounting base and the frame are disposed on the upper surface of the test bench. The mounting base is used to hold the headband to be tested. The pressure sensor is disposed on the mounting base and is used to sense the pressure of the headband to be tested on the mounting base. The drive mechanism is movably connected to the frame along a first direction. The clamp is connected to the output end of the drive mechanism and is used to hold the adjustment knob on the headband to be tested. When the clamp holds the adjustment knob on the headband to be tested, the drive mechanism can provide torque to the clamp so that the clamp drives the adjustment knob to rotate; the torque sensor is used to measure the torque that the clamp bears when it holds the adjustment knob.

2. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 1, characterized in that, The mounting base includes a base and a floating element. The base is disposed on the test bench, and the floating element and the base are spaced apart. The surface of the floating element away from the base is adapted to contact the headband to be tested. The pressure sensor is disposed between the base and the floating element to sense the pressure applied by the headband to be tested to the floating element.

3. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 2, characterized in that, The mounting base further includes a first locking plate and a second locking plate. The first locking plate is disposed on one side of the base in a first direction. A first magnetic element is disposed on the first locking plate, and a first ferromagnetic element is disposed on the base. The first magnetic element and the first ferromagnetic element are magnetically attracted to each other. When the first magnetic element and the first ferromagnetic element are magnetically attracted to each other, the first locking plate and the base clamp the top end of the headband to be tested. The second locking plate is disposed on the other side of the base in the first direction. A second magnetic element is disposed on the second locking plate, and a second ferromagnetic element is disposed on the base. The second magnetic element and the second ferromagnetic element are magnetically attracted to each other. When the second magnetic element and the second ferromagnetic element are magnetically attracted to each other, the second locking plate and the base clamp the bottom end of the headband to be tested.

4. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 3, characterized in that, The first locking plate is provided with at least two mutually spaced first guide rods, and the base is provided with at least two first guide holes, the first guide holes and the first guide rods are one-to-one corresponding, and the first guide rods can be inserted into their corresponding first guide holes; the second locking plate is provided with at least two mutually spaced second guide rods, and the base is provided with at least two second guide holes, the second guide rods and the second guide holes are one-to-one corresponding, and the second guide rods can be inserted into their corresponding second guide holes.

5. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 3, characterized in that, The first locking plate has a first protrusion on the side near the base, which is used to insert into the through hole at the top end of the headband to be tested; the second locking plate has a second protrusion on the side near the base, which is used to insert into the through hole at the bottom end of the headband to be tested.

6. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 4, characterized in that, The mounting base also includes a support and a two-dimensional moving platform. One end of the support is connected to the two-dimensional moving platform, and the other end of the support is connected to the base. The two-dimensional moving platform is disposed on the test platform and can drive the support to move relative to the test platform along a second direction and a third direction. The first direction, the second direction, and the third direction are perpendicular to each other.

7. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 1, characterized in that, It also includes a lifting mechanism, and the drive mechanism is movably connected to the frame through the lifting mechanism.

8. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 7, characterized in that, The drive mechanism includes a mounting frame, a motor, a first synchronous pulley, a second synchronous pulley, a synchronous belt, and a transmission rod. The mounting frame is connected to the lifting mechanism, the motor is connected to the mounting frame, the first synchronous pulley is connected to the output end of the motor, the transmission rod is rotatably assembled with the mounting frame, the second synchronous pulley is connected to the transmission rod, the synchronous belt is wound around the first and second synchronous pulleys, and the torque sensor is connected between the transmission rod and the clamp.

9. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 1, characterized in that, The clamp includes a pneumatic finger, a first clamp, and a second clamp. The pneumatic finger is connected to the pressure sensor, and the first clamp and the second clamp are respectively connected to the pneumatic finger, so that the pneumatic finger can drive the first clamp and the second clamp to move closer to each other or further away from each other.

10. The torque testing device for adjusting the comfort and service life of VR glasses headbands according to claim 9, characterized in that, The first clamp is provided with a plurality of mutually spaced first grooves, which are used for the protrusion of the adjustment knob to be inserted; the second clamp is provided with a plurality of mutually spaced second grooves, which are used for the protrusion of the adjustment knob to be inserted.

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