A kind of on-board glass cover plate flatness laser measuring device

Abstract

This invention relates to the field of flatness measurement devices, specifically to a laser measurement device for the flatness of a vehicle-mounted glass cover plate. The device includes a frame, a moving mechanism, and a laser scanning probe. The moving mechanism drives the laser scanning probe to move in three-dimensional space to scan and measure the glass cover plate placed on a support. It also includes a support and multiple adsorption units, each mounted on a honeycomb-shaped frame. Each adsorption unit includes a nozzle and a control component for controlling the opening and closing of the nozzle. By setting the multiple nozzles and air channels on the honeycomb-shaped frame supporting the glass cover plate to be independent, and utilizing the linkage control of a pressure switch and a micro-solenoid valve, each nozzle is only triggered when it is completely covered by the glass cover plate, thus opening the air channel to generate adsorption negative pressure. This solves the vacuum leakage problem caused by uncovered areas of the workpiece in traditional integral vacuum adsorption structures.

Description

Technical Field

[0001] This invention relates to the field of flatness measurement device technology, and in particular to a laser measurement device for the flatness of vehicle-mounted glass cover plates. Background Technology

[0002] With the development of automotive intelligence, in-vehicle displays are evolving towards larger sizes and multi-screen setups. As the outermost protective layer and interactive interface, the quality requirements for the in-vehicle glass cover are increasingly stringent. Among these requirements, the flatness of the glass cover is a key indicator determining the yield rate of full lamination with the underlying display module, touch reliability, and final appearance quality. To achieve online, efficient, and non-contact quality control, laser measuring devices are widely used for flatness inspection of such precision components.

[0003] In existing technologies, laser measuring devices for measuring the flatness of flat workpieces typically employ a gantry or cantilever motion structure to drive a laser probe to scan the workpiece surface. When positioning and fixing the workpiece, rigid clamps or uniformly controlled vacuum adsorption holes distributed on the worktable are often used to secure the entire workpiece. However, directly applying such devices to the inspection of automotive glass covers presents significant limitations. First, automotive glass covers are usually large, thin-walled components. Using rigid mechanical clamps easily introduces stress into the workpiece, causing micro-deformation and making the measurement results unable to reflect its true flatness in its free state. Second, if an integral vacuum adsorption system is used, for glass covers of different sizes and shapes, the adsorption holes not covered by the workpiece will be directly exposed to the air, causing significant leakage in the vacuum system. This not only affects adsorption stability but also easily draws dust, debris, and other impurities from the environment into the vacuum lines and valves, leading to pipe blockage or solenoid valve failure, reducing the reliability of the equipment in production line environments. Therefore, how to achieve low-stress, high-reliability adsorption and fixation of vehicle glass covers while avoiding system failures caused by size differences or foreign object inhalation is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The main objective of this invention is to provide a laser measurement device for the flatness of vehicle-mounted glass covers, in order to solve the problems raised in related technologies.

[0005] To achieve the above objectives, according to one aspect of the present invention, a laser measurement device for the flatness of a vehicle-mounted glass cover is provided, comprising a frame, a moving mechanism, and a laser scanning probe. The moving mechanism is disposed on the frame, and the laser scanning probe is disposed on the moving mechanism. The moving mechanism is used to drive the laser scanning probe to move in three-dimensional space to scan and measure a glass cover placed on the support. The device further comprises:

[0006] The support part is disposed on the frame and is used to place the glass cover plate to be tested. The support part includes a honeycomb skeleton, on which a plurality of honeycomb grooves are formed in an array.

[0007] Multiple adsorption units are provided, each adsorption unit being disposed on the honeycomb skeleton, and each adsorption unit includes a nozzle and a control component for controlling the opening and closing of the nozzle.

[0008] Furthermore, the control component includes:

[0009] A lifting unit is provided around the nozzle and is used to drive the nozzle to rise when the glass cover is pressed.

[0010] A pressure switch, which is disposed on the nozzle, is used to generate a trigger signal when the glass cover is pressed.

[0011] A miniature solenoid valve, electrically connected to the pressure switch, is used to control the on / off state of the nozzle and the external negative pressure source according to the trigger signal.

[0012] Furthermore, the lifting unit includes a plurality of uprights radially distributed around the nozzle. Each upright is slidably mounted on the honeycomb frame, and the upper end of each upright is higher than the upper surface of the honeycomb frame. The lower end of each upright is connected to the nozzle through a linkage mechanism. When the glass cover presses down on all the uprights of the same lifting unit at the same time, the linkage mechanism drives the nozzle to rise.

[0013] Furthermore, the linkage mechanism includes a crossbar, one end of which is hinged to the lower end of the upright and the other end is hinged to the bottom of the nozzle. A rotating shaft is provided on the crossbar, which is rotatably connected to the honeycomb skeleton and is located close to the upright.

[0014] Furthermore, a reset torsion spring is fitted onto the rotating shaft. The reset torsion spring is used to maintain the crossbar in a horizontal state so that the upper surface of the nozzle is lower than the upper surface of the honeycomb skeleton.

[0015] Furthermore, the lifting unit includes three uprights, the projections of the three uprights on the horizontal plane forming a triangle, and the nozzle is located inside the triangle.

[0016] Furthermore, the supporting part also includes a support plate, the honeycomb skeleton is disposed on the support plate, and a plurality of support blocks are fixedly disposed at the bottom of the honeycomb skeleton, the bottom of each support block abutting against the support plate for supporting the honeycomb skeleton on the support plate.

[0017] Furthermore, the nozzle is positioned directly opposite the support block, and an air passage is provided inside the support block. One end of the air passage is connected to the nozzle, and the other end is used to connect to an external negative pressure source.

[0018] Furthermore, an elastic reset member is provided between the nozzle and the honeycomb skeleton, the elastic reset member being used to drive the nozzle to reset to a position lower than the upper surface of the honeycomb skeleton after the glass cover is removed.

[0019] Furthermore, the elastic reset component includes a spring, which is sleeved on the outside of the bellows. The upper end of the bellows is fixedly connected to the nozzle, and the lower end of the bellows is fixedly connected to the support block. The inner cavity of the bellows is connected to both the nozzle and the external negative pressure source.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] By setting multiple nozzles and air passages on the honeycomb skeleton used to support the glass cover plate to be independent of each other, and by using the linkage control of pressure switch and micro solenoid valve, each nozzle will only trigger the pressure switch and conduct air passage to generate adsorption negative pressure when it is completely covered by the glass cover plate. This solves the vacuum leakage problem caused by the uncovered area of ​​the workpiece in the traditional integral vacuum adsorption structure. Since the uncovered nozzle is always in the closed state, it effectively avoids dust, debris and other impurities in the external environment from being sucked into the air passage and solenoid valve, preventing pipeline blockage and valve failure, and ensuring the operational stability of the device under long-term and continuous production conditions. The independently controlled nozzles can adapt to glass covers of different shapes and sizes. In addition, the honeycomb skeleton combined with the multi-point support structure adopted by this device not only achieves overall lightweighting but also provides a stable support point for the nozzle, effectively offsetting the downward pull of the adsorption force on the glass cover plate. Together with the nozzle pad and skeleton pad with the same material on the upper and lower surfaces, it achieves flexible and uniform support for the glass cover plate, avoiding workpiece deformation or damage caused by stress concentration, thus providing a stable and reliable workpiece reference for flatness measurement. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall invention;

[0023] Figure 2 This is the structure of the supporting part of the present invention;

[0024] Figure 3 This is a bottom view of the bearing portion of the present invention;

[0025] Figure 4 This is a cross-sectional view of the bearing portion of the present invention;

[0026] Figure 5 This is a partially enlarged schematic diagram of the present invention;

[0027] Figure 6 This is a cross-sectional view of the lifting part of the present invention;

[0028] Figure 7 This is a horizontal projection view of the lifting part of the present invention.

[0029] Illustration:

[0030] 1. Column; 2. Horizontal slide rail; 3. Longitudinal slide rail; 4. Main lead screw; 5. Main motor; 6. Slider; 7. Vertical slide rail; 8. Laser scanning probe; 9. Crossbeam; 10. Support plate; 11. Honeycomb skeleton; 12. Honeycomb groove; 13. Nozzle; 14. Support block; 15. Nozzle pad; 16. Skeleton pad; 17. Pressure switch; 18. Spray chamber; 19. Air passage; 20. Lifting part; 201. Upright pole; 202. Upright pole pad; 203. Crossbar; 204. Rotating shaft; 21. Miniature solenoid valve; 22. Bellows; 23. Spring; 24. Column groove; 25. Gap; 26. Container groove. Detailed Implementation

[0031] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0032] Please see Figure 1 This embodiment provides a laser measurement device for the flatness of a vehicle-mounted glass cover, comprising four columns 1, which are vertically arranged and parallel to each other, located at the four corners of a rectangle. Two transverse slide rails 2 are fixedly arranged above the two columns 1, and are parallel to each other. A longitudinal slide rail 3 is slidably mounted on the two transverse slide rails 2 at both ends, allowing the longitudinal slide rail 3 to slide back and forth along the length of the transverse slide rails 2. A main lead screw 4 is mounted on the longitudinal slide rail 3, extending along the length of the longitudinal slide rail 3, and one end of the main lead screw 4 is connected to a drive motor 5. A slider 6 is threadedly connected to the main lead screw 4 and slidably connected to the longitudinal slide rail 3. When the drive motor 5 drives the main lead screw 4 to rotate, it can drive the slider 6 to slide back and forth along the longitudinal slide rail 3. A vertical slide rail 7 is fixedly mounted on the slider 6, and a laser scanning probe 8 is slidably mounted on the vertical slide rail 7 and can slide up and down along the vertical slide rail 7.

[0033] The horizontal slide rail 2 and the vertical slide rail 7 are each driven by an independent servo drive system. This servo drive system typically consists of a servo motor, a ball screw pair, or a synchronous belt drive mechanism, allowing the vertical slide rail 3 to slide back and forth along the horizontal slide rail 2, and the laser scanning probe 8 to slide up and down along the vertical slide rail 7. Through the cooperation of the horizontal slide rail 2, the vertical slide rail 3, and the vertical slide rail 7, the laser scanning probe 8 can move in three-dimensional space, thereby scanning and measuring the glass cover plate.

[0034] The support section is used to hold the glass cover plate to be tested. For example... Figure 2 As shown, the supporting part includes two crossbeams 9, a support plate 10, and a honeycomb frame 11. The crossbeams 9 are fixedly installed below the column 1, and the two crossbeams 9 are parallel to each other. The support plate 10 is fixedly connected to the crossbeams 9, and a groove for accommodating the honeycomb frame 11 is opened on the top of the support plate 10. Multiple honeycomb slots 12 are formed inside the honeycomb frame 11, and the honeycomb slots 12 are distributed in an array. Gripping devices such as robotic arms can extend into the honeycomb slots 12, which facilitates the robotic arms to place the vehicle glass cover plate stably on the honeycomb frame 11.

[0035] Several support blocks 14 are fixedly installed at the bottom of the honeycomb skeleton 11. The bottom of the support blocks 14 abuts against the bottom of the support plate 10, thereby supporting the honeycomb skeleton 11 on the support plate 10. Each honeycomb groove 12 is supported by at least two support blocks 14. The independent support blocks 14 increase the support points of the honeycomb skeleton 11, which can effectively prevent the honeycomb skeleton 11 from deforming under pressure, thereby avoiding the impact of deformation of the bearing part on the measurement accuracy of the glass cover. Figure 3 and Figure 4 As shown, all support blocks 14 avoid the internal space of the honeycomb groove 12, so as not to hinder the movement of the robot arm, prevent the robot arm from colliding with the support blocks 14 and causing vibration, and avoid damaging the glass cover plate. The structural design of the honeycomb skeleton 11 effectively reduces the overall weight of the load-bearing part while ensuring sufficient support strength, which is conducive to achieving the lightweight of the device.

[0036] like Figure 5As shown, a plurality of spray chambers 18 are fixedly disposed on the upper surface of the honeycomb skeleton 11, and each spray chamber 18 is provided with a nozzle 13. The nozzle 13 is funnel-shaped, wider at the top and narrower at the bottom. The larger opening of the nozzle 13 increases the contact area with the glass cover plate, reduces the pressure on the glass cover plate, and prevents the glass cover plate from deforming due to excessive local pressure. A column groove 24 is formed on the honeycomb skeleton 11 below the spray chamber 18, and a bellows 22 and a spring 23 are disposed in the column groove 24. The upper end of the bellows 22 is fixedly connected to the lower part of the nozzle 13, and the lower end is fixedly connected to the support block 14. The spring 23 is sleeved on the outside of the bellows 22, and the bottom end of the spring 23 is fixedly connected to the bottom of the column groove 24, and the top end is fixedly connected to the bottom of the nozzle 13. A gap 25 is left between the outer wall of the nozzle 13 and the side wall of the spray chamber 18, so that the nozzle 13 can swing to a certain extent within the gap 25.

[0037] When spring 23 is in its natural state, it supports nozzle 13 within spray chamber 18, with the upper surface of nozzle 13 lower than the top surface of spray chamber 18, preventing direct contact between nozzle 13 and the glass cover plate placed on it. Each support block 14 has an air passage 19 connected to the inner cavity of bellows 22. The air passage 19 is connected to an external vacuum pump via a flexible hose. When the vacuum pump is operating, negative pressure is generated within nozzle 13 through the air passage 19 and bellows 22.

[0038] like Figure 6 As shown, three lifting sections 20 are provided below each nozzle 13, arranged radially and evenly. Each lifting section 20 is located on the frame of the honeycomb skeleton 11 adjacent to the nozzle 13. The frame of the honeycomb skeleton 11 has a receiving groove 26 for accommodating the lifting section 20. Each lifting section 20 includes a vertical rod 201, the upper end of which is higher than the upper surface of the honeycomb skeleton 11. A vertical rod pad 202 is fixedly provided at the upper end of the vertical rod 201. The vertical rod pad 202 is made of a rubber-like elastic material, ensuring flexible contact between the vertical rod 201 and the glass cover plate, preventing scratches. The lower end of the vertical rod 201 extends into the receiving groove 26, and a crossbar 203 is hinged to its lower end. The outer end of the crossbar 203 is hinged to the bottom of the nozzle 13. A rotating shaft 204 is fixedly mounted on the crossbar 203. The rotating shaft 204 is located near one end of the upright 201, such that the distance between the upright 201 and the rotating shaft 204 is less than the distance between the rotating shaft 204 and the nozzle 13. This design allows the nozzle 13 to rise a greater distance when the upright 201 descends a smaller distance. A return torsion spring is fitted onto the rotating shaft 204. When no external force is applied, the return torsion spring keeps the crossbar 203 in a horizontal state. At this time, the upper surface of the nozzle 13 is lower than the opening of the spray chamber 18. The return torsion spring and the spring 23 work together to keep the nozzle 13 in a lower position.

[0039] A protrusion is fixedly provided on the outer side of the upright 201, and a corresponding groove is provided on the receiving groove 26. The protrusion can slide up and down in the groove, so that the upright 201 can only move up and down within the receiving groove 26, thereby lifting or pulling down the nozzle 13 through the lever action of the crossbar 203. Figure 7 As shown, the projections of the three uprights 201 on the horizontal plane form a triangle, which encloses the nozzle 13. When the glass cover simultaneously presses down on all three uprights 201, the uprights 201 move downwards, pressing down one end of the crossbar 203. The other end of the crossbar 203 tilts upwards around the pivot 204, thereby lifting the nozzle 13 upwards. At this time, the upper surface of the nozzle 13 is in contact with the lower surface of the glass cover, and the nozzle 13 is completely covered by the glass cover, preventing external debris from entering the nozzle 13 and causing blockage. When the glass cover only presses down on one or two uprights 201, the nozzle 13 tilts due to uneven force and cannot form a good fit with the lower surface of the glass cover. In this case, the nozzle 13 is not completely covered.

[0040] A nozzle pad 15 is fixedly disposed on the top of the nozzle 13, and a frame pad 16 is fixedly disposed on the top of the honeycomb frame 11. The nozzle pad 15 and the frame pad 16 are made of the same material, namely rubber-like elastic material. When the glass cover is placed on the honeycomb frame 11, the glass cover is in flexible contact with both the frame pad 16 and the raised nozzle pad 15, preventing the glass cover from deforming or even breaking.

[0041] Each nozzle pad 15 is equipped with a pressure switch 17, and each air passage 19 is equipped with a miniature solenoid valve 21. The pressure switch 17 is electrically connected to the corresponding miniature solenoid valve 21, and the pressure switch 17 is used to control the opening and closing of the miniature solenoid valve 21. An external vacuum pump is connected to all air passages 19 through hoses, so that each air passage 19 has negative pressure when the vacuum pump is working. However, due to the opening and closing control of the miniature solenoid valve 21, the negative pressure can be selectively transmitted to the corresponding nozzle 13.

[0042] Before testing, the external vacuum pump is turned on to evacuate all air passages 19. At this time, since the nozzles 13 are not yet covered by the glass cover, the pressure switch 17 is not pressurized, and the micro solenoid valves 21 remain closed. Therefore, no negative pressure is generated in the nozzles 13, and no objects are attracted, thus not affecting the placement of the glass cover by the robotic arm. Subsequently, the robotic arm picks up the glass cover and places it stably on the honeycomb skeleton 11. After the glass cover is in place, it simultaneously presses down on the corresponding skeleton pad 16 and the upright pad 202. For the nozzles 13 in the area covered by the glass cover, the glass cover also presses down on the three uprights 201 around the nozzle 13. The uprights 201 descend and lift the nozzles 13 upwards through the crossbar 203, so that the nozzles 13 are in contact with the lower surface of the glass cover. At the same time, the glass cover presses down on the pressure switch 17 in the nozzle pad 15, triggering the pressure switch 17. Pressure switch 17 controls the corresponding miniature solenoid valve 21 to open, allowing nozzle 13 to connect to an external vacuum pump via bellows 22 and air passage 19. This generates negative pressure within nozzle 13, thereby adsorbing and fixing the glass cover at that location. For nozzles 13 in areas not covered by the glass cover, since the glass cover does not simultaneously press down on the three outer posts 201, nozzle 13 is not smoothly lifted and cannot adhere to the glass cover. Pressure switch 17 is not triggered, and the miniature solenoid valve 21 remains closed. No negative pressure is generated within nozzle 13, therefore no foreign matter is sucked in.

[0043] In this way, the independently controlled nozzle 13 only generates negative pressure in the area supporting the glass cover plate. This adapts to glass cover plates of different shapes and prevents incompletely covered nozzles 13 from opening and drawing debris into the air passage 19, causing blockage and ensuring the long-term stable operation of the adsorption system. When the nozzle 13 adsorbs the glass cover plate, the glass cover plate exerts downward pressure on the nozzle 13. Since the nozzle 13 is positioned directly opposite the support block 14, this downward pressure is transmitted to the support block 14 through the honeycomb skeleton 11. The support block 14 rests against the bottom of the support plate 10, providing upward support for the glass cover plate. This effectively counteracts the downward deformation of the glass cover plate caused by the adsorption force, ensuring the flatness stability of the glass cover plate during the measurement process.

[0044] After the glass cover is adsorbed and fixed, the servo drive system controls the longitudinal slide rail 3 to slide along the transverse slide rail 2, the slider 6 to slide along the longitudinal slide rail 3, and the laser scanning probe 8 to slide along the vertical slide rail 7, so that the laser scanning probe 8 moves in three-dimensional space to scan and measure the glass cover. After the test is completed, the external vacuum pump is turned off, the negative pressure in the air channel 19 and the nozzle 13 disappears, the nozzle 13 no longer adsorbs the glass cover, and the glass cover can be removed from the honeycomb skeleton 11.

[0045] The vehicle-mounted glass cover flatness laser measuring device provided in this embodiment achieves reliable adsorption and fixation of glass covers of different shapes through the honeycomb skeleton 11 and the independently controlled lifting nozzle 13 structure, while effectively preventing nozzle clogging and ensuring measurement accuracy and long-term stable operation of the device.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A laser measurement device for the flatness of a vehicle-mounted glass cover, comprising a frame, a moving mechanism, and a laser scanning probe (8), characterized in that, The moving mechanism is mounted on the frame, and the laser scanning probe (8) is mounted on the moving mechanism. The moving mechanism is used to drive the laser scanning probe (8) to move in three-dimensional space to scan and measure the glass cover plate placed on the support. It also includes: The support part is disposed on the frame and is used to place the glass cover plate to be tested. The support part includes a honeycomb skeleton (11) on which a plurality of honeycomb grooves (12) are formed in an array. Multiple adsorption units are provided on the honeycomb skeleton (11). Each adsorption unit includes a nozzle (13) and a control component for controlling the opening and closing of the nozzle (13).

2. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 1, characterized in that, The control component includes: A lifting part (20) is provided on the periphery of the nozzle (13) for driving the nozzle (13) to rise under the pressure of the glass cover. Pressure switch (17), which is disposed on the nozzle (13) and is used to generate a trigger signal when the glass cover is pressed; A miniature solenoid valve (21) is electrically connected to the pressure switch (17) and is used to control the opening and closing of the nozzle (13) and the external negative pressure source according to the trigger signal.

3. The laser measurement device for the flatness of vehicle-mounted glass cover plates according to claim 2, characterized in that, The lifting part (20) includes a plurality of uprights (201) arranged radially around the nozzle (13). Each upright (201) is slidably disposed on the honeycomb frame (11), and the upper end of each upright (201) is higher than the upper surface of the honeycomb frame (11). The lower end of each upright (201) is connected to the nozzle (13) through a linkage mechanism. When the glass cover presses all the uprights (201) of the same lifting part (20) at the same time, the linkage mechanism drives the nozzle (13) to rise.

4. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 3, characterized in that, The linkage mechanism includes a crossbar (203), one end of which is hinged to the lower end of the upright (201), and the other end is hinged to the bottom of the nozzle (13). A rotating shaft (204) is provided on the crossbar (203), and the rotating shaft (204) is rotatably connected to the honeycomb skeleton (11), and the rotating shaft (204) is located close to the upright (201).

5. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 3, characterized in that, A reset torsion spring is fitted on the rotating shaft (204). The reset torsion spring is used to keep the crossbar (203) in a horizontal state so that the upper surface of the nozzle (13) is lower than the upper surface of the honeycomb skeleton (11).

6. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 3, characterized in that, The lifting unit (20) includes three uprights (201), the projections of the three uprights (201) on the horizontal plane form a triangle, and the nozzle (13) is located inside the triangle.

7. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 1, characterized in that, The supporting part also includes a tray (10), the honeycomb skeleton (11) is disposed on the tray (10), and a plurality of support blocks (14) are fixedly disposed at the bottom of the honeycomb skeleton (11). The bottom of each support block (14) abuts against the tray (10) to support the honeycomb skeleton (11) on the tray (10).

8. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 7, characterized in that, The nozzle (13) is positioned opposite the support block (14), and an air passage (19) is provided inside the support block (14). One end of the air passage (19) is connected to the nozzle (13), and the other end is used to connect to an external negative pressure source.

9. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 1, characterized in that, An elastic reset member is provided between the nozzle (13) and the honeycomb skeleton (11). The elastic reset member is used to drive the nozzle (13) to reset to a position lower than the upper surface of the honeycomb skeleton (11) after the glass cover is removed.

10. The laser measurement device for the flatness of vehicle-mounted glass cover plate according to claim 9, characterized in that, The elastic reset component includes a spring (23), which is sleeved on the outside of the bellows (22). The upper end of the bellows (22) is fixedly connected to the nozzle (13), and the lower end of the bellows (22) is fixedly connected to the support block (14). The inner cavity of the bellows (22) is connected to the nozzle (13) and the external negative pressure source.

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