Clamping device for optical measurement with vertical cavity length adjustment and disturbance isolation

Abstract

The application relates to a clamping device for optical measurement vertical cavity length adjustment and disturbance isolation, comprising a roller shutter structure, a measured mirror clamp, a support rod structure, a prism structure and a base structure. The application protects the light path of an interference measurement system by using the roller shutter structure, and the influence of external environmental factors such as stray light disturbance on the measurement light path is isolated when collecting an interference intensity diagram. When performing phase shift interference measurement in the vertical clamp, the measured mirror needs to be moved up and down to adjust the interference cavity length, and the interference cavity length can determine the corresponding harmonic frequency of each surface of the optical interference signal, which is extremely important for the measurement result. The application realizes free adjustment of the interference cavity length without affecting the measurement light path. By using electromagnetic principles, the measurement system environment is stabilized by a magnetic suspension module, mechanical errors are not introduced, direct contact is avoided, high-precision optical lenses are protected during the measurement process, and damage to the high-precision optical lenses is prevented.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, specifically to a clamping device for adjusting the vertical cavity length and isolating disturbances in optical measurements. Background Technology

[0002] High-end components require extremely high precision in their machined surfaces. Optical interferometry (such as phase-shifting interferometry) is one of the most accurate non-contact measurement methods currently available, achieving precision down to the nanometer level. Among these, the Fizeau interferometer is widely used due to its common-path structure and stable fringes, but its horizontal structure occupies a large amount of space. Vertical interferometers, by arranging the measurement optical path vertically, significantly save space and have become an important direction for development.

[0003] However, existing vertical interferometry systems still have the following key problems: Environmental sensitivity: Nanoscale measurements are extremely sensitive to external disturbances (vibration, stray light) and lack effective protection and isolation measures; Difficulty in cavity length adjustment: In a vertical structure, adjusting the interference cavity length affects the harmonic frequency and measurement accuracy, and it is difficult to adjust it freely without interfering with the optical path; Human and mechanical errors: Traditional movement methods rely on manual labor or rigid hardware, which can easily damage the mirror surface and introduce mechanical errors, affecting accuracy; Rigid contact vibration: Fixtures often use large-area pure rigid connections, which cannot effectively buffer vibration; Poor adaptability: Traditional clamps are only suitable for small diameter (such as about 20mm) or specific shaped components, and lack adaptive clamping capabilities.

[0004] Existing research has made progress in optical detection algorithms, distance reconstruction, and harmonic frequency estimation, but the practical problems of the above-mentioned vertical interferometry system in terms of disturbance resistance, cavity length adjustment, contactless / error-free movement, vibration reduction, and adaptive clamping have not yet been solved.

[0005] Among existing technologies and devices, the inventors of this patent, Chang Lin et al., have published invention patents titled "Interferometric Weighted Sampling Phase-Shifting Analysis Method and Measurement System Based on Pre-analysis for Arbitrary Cavity Length - CN202010227556.X", "Multi-Surface Shape Measurement Method Based on Frequency Blind Estimation - CN202010891522.X", and papers including "Lin Chang, Yingjie Yu. Wavelength-tuning phase-shifting interferometry of transparent plates using sub-signal frequency correction[J]. Measurement, 2022, 205: 112157" (SCI indexed) and "Lin Chang, Bing Li, Yulan Wei, Yingjie Yu. Wavelength-shifting interferometry using the frequency-modulated Chirp-Z transform and effective multi-harmonicsampling[J]. OPTICS AND LASERS IN ENGINEERING, 2023, 163: The innovative device and algorithm designed in patent 107476 (SCI indexed) achieves goals such as efficient optical detection algorithm design, accurate reconstruction of measurement distance in interferometric systems, and accurate estimation of interferometric harmonic frequencies, exhibiting good adaptability and high measurement accuracy. However, the innovative structures and algorithms in the aforementioned patents and papers cannot solve the following problems: first, the problem of resisting external disturbances in vertical interferometric systems; second, the problem of adjusting the interferometric cavity length of vertical fixtures; third, the problem of not being able to avoid introducing mechanical errors and preventing direct contact; fourth, the measurement vibration problem caused by large-area rigid contact; and fifth, the problem that the fixture cannot adaptively clamp various types of mirrors under test. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a clamping device for vertical cavity length adjustment and disturbance isolation for optical measurement, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a vertical cavity length adjustment and disturbance isolation clamping device for optical measurement, comprising: a roller shutter structure, a lens under test clamp, a support rod structure, a frustum structure, and a base structure; the roller shutter structure includes an interferometer base and a roller shutter rod transmission gear set mechanism; the lens under test clamp includes a clamping block mechanism and a magnetic levitation module; the base structure includes an upper base mechanism and a lower base mechanism.

[0008] Preferably, the interferometer base is disc-shaped with a central rectangular hole and a circumferential guide rail on the edge of the roller shutter; the roller shutter protective sleeve is placed vertically, welded to the edge of the base at the top, and interference-fitted to the semi-circular hole of the upper base mechanism at the bottom, with the roller shutter inlet and outlet opening to the side.

[0009] Preferably, the roller blind rod drive gear mechanism is as follows: the roller blind is a rectangular PVC coated fabric, one end of which is glued to the roller blind rod, and the other end of the roller blind hook is placed on the upper guide rail of the roller blind; the roller blind rod base is interference-fitted with the roller blind rod, and the bottom protrusion is interference-fitted with the groove of the upper base; the knob is connected to the small input shaft through the threaded rod, and the small input shaft is clearance-fitted with the upper base; the input gear meshes with the output gear to drive the roller blind rod to rotate and control the extension and retraction of the roller blind.

[0010] Preferably, the clamping block mechanism includes: four circular guide rail grooves evenly distributed below the circular ring, with magnetic clamping blocks installed in the grooves; a slide table slides within the grooves, and a hemispherical rubber fixing head is provided at the clamping end; a sliding circular ring is built into the central circular through hole of the clamping block and connected by a compression spring; a limiting rod is inserted into a small blind hole on the outer wall of the sliding circular ring, slides along the limiting rod guide rail groove, and is limited by a circular protrusion at its end, with a rubber film covering the contact area; a slider on the inner wall of the sliding circular ring moves up and down along the groove on the outer wall of the upper support rod.

[0011] Preferably, the magnetic levitation module has: a through hole at the center of the platform, which is placed on the gear cover; a protective cover is placed on the platform, with a through hole at the center and a wire inlet / outlet hole on the side; an electromagnetic coil is placed inside the protective cover and surrounds the upper support rod; a total of four groups are evenly distributed circumferentially.

[0012] Preferably, the support rod structure includes: a limiting block threadedly connected to the top of the upper support rod; the upper support rod is hollow, with a circular base at the bottom placed on a platform, and four circumferential grooves on the inner and outer walls; four long protrusions on the outer wall of the lower support rod are interference-fitted with the grooves on the inner wall of the upper support rod; a wheel support frame is welded to the bottom of the lower support rod, and the wheels are connected by axles and can roll on the side of the frustum; a total of four sets are evenly distributed circumferentially.

[0013] Preferably, the frustum structure is as follows: the gear knob is connected to the small input shaft of the gear via a threaded rod C. The small input shaft drives the small gear via a small key, which in turn drives the three large gears and the large input shaft gear, causing the large input shaft to rotate. The external thread at the bottom of the large input shaft mates with the internal thread at the center of the frustum. Frustum limiting rods are provided at the four corners of the frustum, and the top is welded to the upper base. Rotating the gear knob causes the frustum to move up and down, causing the wheel to roll along the inclined surface of the frustum, thus changing the clamping radius.

[0014] Preferably, the upper base mechanism is as follows: the upper base is a hexahedral plate with rubber gaskets in the four corner threaded holes and bolted connections; a frustum gear is placed in the central groove of the upper surface, and a roller shutter gear set is placed in the edge groove; a roller shutter lower guide rail is provided at the edge of the central groove; the curtain cover is covered with the edge groove and has a curtain cover round hole and a roller shutter rod round hole; the gear cover is covered with the central groove and has four elongated holes for the lower support rod to pass through and move; a spring and pressure plate are provided near the edge of the elongated holes to tighten the lower support rod and provide centripetal preload; a platform is placed on the gear cover.

[0015] Preferably, the lower base mechanism is as follows: the upper base is connected to the lower base by bolts passing through the large rubber pad; the lower base is provided with threaded holes around its perimeter and its bottom is placed on the anti-vibration rubber pad; the bolts pass through the small rubber pad, the threaded holes at the bottom of the lower base and the holes of the anti-vibration rubber pad, and are connected to the threaded holes of the anti-vibration platform.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a roller shutter structure to protect the optical path of the interferometric measurement system, isolating stray light disturbances and other external environmental factors from affecting the measurement optical path during interferometric intensity map acquisition. In phase-shifting interferometric measurements using a vertical fixture, the measured mirror needs to be moved up and down to adjust the interference cavity length. The interference cavity length determines the corresponding harmonic frequencies of each surface of the optical interference signal, which is crucial for the measurement results. This invention allows for free adjustment of the interference cavity length without affecting the measurement optical path. Utilizing electromagnetic principles, a magnetic levitation module stabilizes the measurement system environment, preventing the introduction of mechanical errors and eliminating direct contact. This protects the high-precision optical lens during measurement and prevents damage, solving the problem of traditional fixtures where rigid contact between mechanical components prevents vibration filtering. It achieves the function of adaptive adjustment of the fixture to hold the measured mirror, greatly improving the convenience of optical measurement. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the interferometer base assembly; Figure 2 This is an assembly diagram of the roller shutter rod drive gear set mechanism; Figure 3 This is a schematic diagram of the roller shutter rod drive gear set mechanism parts; Figure 4 This is a schematic diagram of the clamping block mechanism assembly; Figure 5 This is a schematic diagram of the clamping block component; Figure 6 This is a schematic diagram of the magnetic levitation module; Figure 7 This is a schematic diagram showing the position of the electromagnetic coil of the magnetic levitation module; Figure 8 This is a schematic diagram of the magnetic levitation module components; Figure 9 This is a schematic diagram of the support rod structure; Figure 10 This is a schematic diagram of the support rod structure parts; Figure 11 This is a schematic diagram of a frustum structure; Figure 12 This is a detailed schematic diagram of the frustum structure; Figure 13 This is a schematic diagram of the upper base mechanism; Figure 14 This is a schematic diagram of the upper base mechanism parts; Figure 15 This is a schematic diagram of the lower base mechanism; Figure 16 This is a schematic diagram of the overall assembly of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A vertical cavity length adjustment and disturbance isolation clamping device for optical measurement includes a roller shutter structure 80, a lens under test clamp 81, a support rod structure 82, a truncated pyramid structure 83, and a base structure 84. The roller shutter structure 80 includes an interferometer base 90 and a roller shutter rod transmission gear set mechanism 91, which are connected by an interference fit and placed at the top of the device. The lens under test clamp 81 includes a clamping block mechanism 92 and a magnetic levitation module 93, which are arranged sequentially from top to bottom. The base structure 84 includes an upper base mechanism 94 and a lower base mechanism 95, which are connected by threads. The upper base mechanism 94 has an edge groove 78 and a center groove 77, which respectively place the roller shutter rod transmission gear set mechanism 91 and the gear set of the truncated pyramid structure 83. The magnetic levitation module 93 is placed on the upper surface of the upper base mechanism 94. The support rod structure 82 passes through the clamping block mechanism 92, the magnetic levitation module 93, and the upper base mechanism 94 from top to bottom. Its bottom wheel 44 contacts the truncated pyramid structure 83. During interferometry, the electromagnetic coil 35 is energized, causing the magnetic poles below the clamping block 17 to be opposite to those above the electromagnetic coil 35. The clamping block 17 is placed in the circular guide rail groove 16 via the slide table 18, and the spring 23 presses against the upper support rod 38. Adjusting the current of the electromagnetic coil changes the magnetic field strength, causing the clamping block 17 to rise and fall accordingly. The upper support rod 38 and the lower support rod 41 are interference-fitted, and the spring 45 inside the gear cover 61 presses the lower support rod 41 inward. Twisting the gear knob 47 causes the truncated pyramid 55 to move up and down via gear transmission, and the wheel 44 rolls along the side of the truncated pyramid, changing the clamping radius of the support rod structure 82. This causes the four clamping blocks 17 to move inward or outward, achieving adaptive adjustment of the clamping radius and non-contact adjustment of the interference cavity length.

[0020] Example 2: Through the attached diagram Figure 1 , Figure 14 As can be seen, the interferometer base 90 is disc-shaped with a central rectangular hole 1 and an edge circumferential roller shutter upper guide rail 2; the roller shutter protective sleeve 3 is placed vertically, welded to the edge of the base at the top, and interference-fitted with the semi-circular hole 70 of the upper base mechanism 94 at the bottom, with a side-opening roller shutter inlet and outlet 4.

[0021] Through the attached diagram Figure 1 , Figure 2 , Figure 3 , Figure 13 As can be seen, in the roller blind rod drive gear mechanism 91: the roller blind 5 is a rectangular PVC coated fabric, one end of which is glued to the roller blind rod 7, and the other end of the roller blind hook 6 is placed in the upper guide rail 2 of the roller blind. The roller blind rod base 8 is interference-fitted with the roller blind rod 7, and the bottom protrusion is interference-fitted with the groove of the upper base. The knob 9 is connected to the small input shaft 10 through the threaded rod 71, and the small input shaft is clearance-fitted with the upper base. The roller blind rod base 8 is interference-fitted with the output gear 12 through the keyway of the small flat key 13, and the output gear meshes with the input gear 11. The input gear is connected to the small input shaft 10 through the flat key 14. Twisting the knob 9 drives the roller blind rod 7 to rotate, controlling the extension and retraction of the roller blind 5.

[0022] Through the attached diagram Figure 4 , Figure 5 , Figure 9 , Figure 10 As can be seen, the clamping block mechanism 92 consists of a clamping block 17 made of magnetic material and a fixing head 19 made of rubber. Four circular guide grooves 16 are evenly distributed circumferentially below the circular ring 15, each groove containing a clamping block 17, and a sliding table 18 at its rear can slide within the groove. A sliding ring 27 is housed within the central circular through hole 20 of the clamping block, connected to the inner wall of the through hole by two compression springs 23. A limit rod 26 is inserted into a small blind hole 22 on the outer wall of the sliding ring, sliding along the limit rod guide groove 24, with a circular protrusion 25 at the end for limiting, and a rubber film 29 covering the contact point. Four sliders 28 on the inner wall of the sliding ring are covered with a rubber film and move up and down along the groove on the outer wall of the upper support rod 38.

[0023] Through the attached diagram Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 13 , Figure 14 As can be seen, the magnetic levitation module 93 has a central lower through-hole 31 on the platform 30, which is placed on the gear cover 61. The protective cover 32 is placed on the platform, with a central upper through-hole 33 and a side opening for wire entry and exit holes 34. The electromagnetic coil 35 is placed inside the protective cover, surrounding the upper support rod 38. There are four sets of coils evenly distributed circumferentially.

[0024] Through the attached diagram Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 As can be seen, in support rod structure 82, the limiting block 36 is threadedly connected to the top of the upper support rod 38. The upper support rod is hollow, with a circular base 40 at the bottom placed on the platform 30, and four circumferential grooves on the inner and outer walls. The four long protrusions on the outer wall of the lower support rod 41 are interference-fitted with the grooves on the inner wall of the upper support rod. A wheel support frame 42 is welded to the bottom of the lower support rod, and the wheel 44 is connected by axle 43, allowing it to roll on the side of the frustum 55. There are four sets of wheels evenly distributed circumferentially.

[0025] Through the attached diagram Figure 11 , Figure 12 As can be seen, in the frustum structure 83: the gear knob 47 is connected to the small input shaft 48 via the threaded rod C 72. The small input shaft drives the small gear 52 via the small gear key 49, which in turn drives the three large gears 51 and the large input shaft gear 53, causing the large input shaft 54 ​​to rotate. The external thread at the bottom of the large input shaft mates with the internal thread at the center of the frustum 55. Frustum limiting rods 56 are provided at the four corners of the frustum, and the top is welded to the upper base 57. Rotating the gear knob causes the frustum to move up and down, and the wheel rolls along the inclined surface of the frustum, changing the clamping radius.

[0026] Through the attached diagram Figure 13 , Figure 14 As can be seen, the upper base mechanism 94 consists of an upper base 57 that is a hexahedral plate with rubber gaskets 64 installed in the four corner threaded holes 76 and connected by bolts 68. A frustum gear set is placed in the central groove 77 on the upper surface, and a roller shutter gear set is placed in the edge groove 78; a lower roller shutter guide rail 63 is located at the edge of the central groove. The curtain cover 58 covers the edge groove and has a curtain cover circular hole 59 and a roller shutter rod circular hole 60. The gear cover 61 covers the central groove and has four elongated holes 62 for the lower support rod 41 to pass through and move; a spring 45 and a pressure plate 46 are located near the edge of the elongated holes to tighten the lower support rod and provide centripetal preload. A platform 30 is placed on the gear cover.

[0027] Through the attached diagram Figure 15 As can be seen, in the lower base mechanism 95: the upper base 57 is connected to the lower base 65 by bolts 68 passing through the large rubber pad 66. The lower base has threaded holes 75 around its perimeter, and its bottom rests on the anti-vibration rubber pad 69. Bolts pass through the small rubber pad 67, the threaded holes 75 at the bottom of the lower base, and the holes in the anti-vibration rubber pad, and are connected to the threaded holes 75 in the anti-vibration platform.

[0028] When using: The principle of this invention is as follows: In a vertical interferometric measurement system, the interferometer is located at the top and placed in an interferometer base. A roller shutter is installed below the interferometer base to isolate the measurement optical path system from the external environment, thereby providing measurement protection. A fixture for the object under test is installed below the interferometer base. The fixture contains four clamping blocks that can clamp the edge of the object under test. Each clamping block is made of magnets, and an electromagnetic coil is installed below each clamping block. The electromagnetic coils are powered by a DC power supply. By changing the direction of the current, the magnetic poles below the clamping blocks and the magnetic poles above the electromagnetic coils repel each other. Then, by adjusting the magnitude of the current flowing through the electromagnetic coil to control the strength of the magnetic field, the length of the interference cavity can be adjusted quickly and stably without introducing mechanical errors. A through hole is left in the center of the clamping block, and a support rod is placed in the through hole. The support rod can move horizontally through a combination of springs and frustum structures, thereby driving the clamping block to clamp the mirror under test. It has the ability to clamp mirrors of different sizes over a wide range. Since there are springs supporting the clamping block and the support rod, and the limiting rod is wrapped with a rubber film, this mechanism also enables the mirror under test fixture to have the ability to buffer and absorb vibrations.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A clamping device for vertical cavity length adjustment and disturbance isolation in optical measurement, characterized in that, include: Roller blind structure (80), mirror clamp (81), support rod structure (82), truncated pyramid structure (83) and base structure (84); The roller shutter structure (80) includes an interferometer base (90) and a roller shutter rod drive gear mechanism (91). The test mirror fixture (81) includes a clamping block mechanism (92) and a magnetic levitation module (93). The base structure (84) includes an upper base mechanism (94) and a lower base mechanism (95). Interferometer base (90): It is disc-shaped with a rectangular hole (1) in the center and a roller shutter upper guide rail (2) along the circumference near the edge; the roller shutter protective sleeve (3) is a vertical cylinder, which is welded to the edge of the interferometer base (90) at the top and is clamped to the semi-circular hole (70) in the upper base mechanism (94) at the bottom by interference fit, and has roller shutter inlet and outlet (4) on its side wall. Roller blind rod drive gear mechanism (91): One end of the roller blind (5) is glued to the roller blind rod (7), and the other end is provided with a roller blind hook (6) and placed in the upper guide rail (2) of the roller blind; the knob (9) drives the input gear (11) through the small input shaft (10), and drives the roller blind rod base (8) and roller blind rod (7) to rotate through the output gear (12), thereby controlling the extension and retraction of the roller blind (5).

2. The apparatus according to claim 1, characterized in that, The structure of the clamping block mechanism (92) and the magnetic levitation module (93) is as follows: Clamping block mechanism (92): Four circular guide rail grooves (16) are evenly distributed along the circumference below the circular ring (15), and clamping blocks (17) are provided in each groove; the slide table (18) at the rear of the clamping block (17) can slide in the guide rail groove, and the clamping end is provided with a hemispherical rubber fixing head (19); a sliding ring (27) is provided in the circular through hole (20) in the center of the clamping block (17), and is connected to the inner wall of the through hole by a compression spring (23); a limiting rod (26) is provided on the outer wall of the sliding ring (27), which slides along the limiting rod guide rail groove (24) and is limited by the circular protrusion (25) at the end, and the contact point is covered with a rubber film (29); the slider (28) on the inner wall of the sliding ring (27) moves up and down along the groove on the outer wall of the upper support rod (38); Magnetic levitation module (93): The platform (30) and the protective cover (32) are arranged in four groups along the circumference. The protective cover (32) is equipped with an electromagnetic coil (35) surrounding the upper support rod (38). The protective cover (32) is equipped with wire inlet and outlet holes (34) on the side.

3. The apparatus according to claim 1, characterized in that, The structures of the support rod structure (82) and the frustum structure (83) are as follows: Support rod structure (82): The limiting block (36) is threaded to the top of the upper support rod (38); the upper support rod (38) is hollow, and the bottom circular base (40) is placed on the platform (30), with four grooves machined along the circumference on both the inner and outer walls; the four long protrusions on the outer wall of the lower support rod (41) are interference-fitted with the grooves on the inner wall of the upper support rod (38); the bottom of the lower support rod (41) is fitted with wheels (44) through the wheel support frame (42); a total of four sets are evenly distributed along the circumference; Frustum structure (83): The gear knob (47) drives the small gear (52) through the small gear input shaft (48), which in turn drives the three large gears (51) and the large input shaft gear (53) to rotate the large input shaft (54); the external thread below the large input shaft (54) is engaged with the internal thread in the center of the frustum (55); the four corners of the frustum (55) are provided with vertical limit rods (56), and the top is welded to the lower surface of the upper base (57); rotating the gear knob (47) can make the frustum (55) move up and down, driving the wheel (44) to roll along the inclined surface of the frustum and change the clamping radius.

4. The apparatus according to claim 1, characterized in that, The structure of the upper base mechanism (94) is as follows: The upper base (57) is a hexahedral plate with threaded holes (76) at the four corners and rubber gaskets (64) placed thereon, and is connected by bolts (68); The upper base (57) has a central groove (77) on its upper surface where a frustum structure gear is placed, and an edge groove (78) where a roller shutter rod drive gear set is placed; the edge of the central groove is provided with a roller shutter lower guide rail (63). The curtain cover (58) covers the edge groove and has a round hole for the small input shaft (10) and the roller shutter rod (7) to pass through; the gear cover (61) covers the center groove and has four elongated holes (62) for the lower support rod (41) to pass through and move; a spring (45) and a pressure plate (46) are provided on the side of the elongated hole near the edge to press the lower support rod (41) and provide centripetal preload; a platform (30) for placing the magnetic levitation module is placed on the gear cover (61).

5. The apparatus according to claim 1, characterized in that, The structure of the lower base mechanism (95) is as follows: The upper base (57) is connected to the lower base (65) by a bolt (68) passing through a large rubber pad (66); the lower base (65) has threaded holes (75) around its perimeter and is placed on an anti-vibration rubber pad (69) at its bottom; the bolt (68) passes through the small rubber pad (67), the threaded holes (75) at the bottom of the lower base and the holes on the anti-vibration rubber pad (69) and is connected to the threaded holes (75) on the anti-vibration platform.

6. The apparatus according to any one of claims 1 to 5, characterized in that: The clamping block (17) is made of magnetic material; the roller shutter (5) is made of PVC coated cloth material; the rubber pad (64), the large rubber pad (66), the small rubber pad (67), the anti-vibration rubber pad (69) and the rubber film (29) are all made of rubber material and are used for buffering and vibration absorption.

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