Zeolite molecular sieve safety detection device

Abstract

The utility model relates to the technical field of molecular sieve detection, in particular to a zeolite molecular sieve safety detection device which comprises a base, supporting frames are arranged at the positions, close to the left side and the right side, of the top of the base, a safety detector body is jointly supported by the tops of the two supporting frames, and a driving assembly and a taking and placing assembly are arranged at the top of the base. The taking and placing assembly comprises a movable base, four rectangular mounting grooves are formed in the top of the movable base, fans are arranged in the four rectangular mounting grooves, a cover plate is arranged on the front side of the movable base, three U-shaped supports which are arranged at equal intervals in the vertical direction are arranged on the rear side of the cover plate, L-shaped supporting plates are hung on the three U-shaped supports, and annular hollow boxes are arranged at the rear ends of the three L-shaped supporting plates. According to the safety detection device for the zeolite molecular sieve, an automatic taking and placing assembly is designed, and through cooperation of an L-shaped supporting plate and a U-shaped support, the disassembly and assembly process of an annular hollow box is simplified, and the operation safety is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of molecular sieve detection, in particular to a zeolite molecular sieve safety detection device. Background Art

[0002] Zeolite molecular sieves are crystalline porous materials composed of silicon, aluminum, oxygen, and other elements. Due to their unique, regular microporous structure, excellent adsorption properties, and ion exchange capacity, they are widely used in petrochemicals, environmental protection, gas separation, catalysis, and other fields. Their internal pore structure allows for the selective sieving of molecules, playing a vital role in adsorption, separation, and catalysis. Zeolite molecular sieves are particularly important in industrial processes such as petroleum refining, gas separation, and waste gas treatment, ensuring their stability and safety is crucial to production continuity and safety.

[0003] However, in practical applications, zeolite molecular sieves often operate under high temperatures, high pressures, or corrosive media. Long-term use can lead to degradation of their physical structure or chemical properties. For example, the pore structure of the molecular sieve may collapse due to high temperatures or pressures, or become ineffective due to chemical reactions caused by the adsorption of harmful gases. If these issues are not detected promptly, they will pose a significant safety risk to the entire production process. Therefore, real-time monitoring of the status of zeolite molecular sieves to ensure they operate within safe limits has become an urgent issue.

[0004] Currently, there are some safety detection devices for zeolite molecular sieves, which can monitor the temperature, pressure, gas adsorption and other parameters of the molecular sieve. However, the existing detection devices still have some significant shortcomings:

[0005] 1. Inconvenient handling: Existing devices often rely on manual handling of zeolite molecular sieves, which is inconvenient and poses safety risks, especially in high-temperature and high-pressure environments. Operators need to frequently touch the equipment, increasing the risk of personal safety.

[0006] 2. Poor dispersion: Existing devices often fail to fully disperse the zeolite molecular sieve during testing, resulting in zeolite accumulation and affecting the accuracy of test results. Because the pores and surface area of ​​zeolite molecular sieves are crucial to their performance, uneven distribution can lead to incomplete detection, frequent missed or false detections, and reduced test reliability.

[0007] Therefore, developing a safety detection device that can be easily operated under high temperature and high pressure environment and can well disperse zeolite molecular sieves can not only improve the detection accuracy, but also effectively improve the safety of operation, which is of great practical significance. In view of this, we propose a zeolite molecular sieve safety detection device. Utility Model Content

[0008] The purpose of the utility model is to provide a zeolite molecular sieve safety detection device to solve the problems raised in the above background technology.

[0009] To achieve the above objectives, the present invention provides the following technical solutions:

[0010] A zeolite molecular sieve safety detection device includes a base. Support frames are provided on the top of the base, near the left and right sides, to support the safety detector body and enhance the overall structural strength of the device. The tops of the two support frames jointly support the safety detector body, which is generally composed of a sensor module, a data processing unit, a display and control interface, an alarm system, and a power module.

[0011] The sensor module includes a temperature sensor, a pressure sensor, a gas sensor, and a spectrum sensor. The temperature sensor is used to monitor the temperature of the zeolite molecular sieve in real time to ensure that it is within the safe operating range. The pressure sensor monitors the pressure changes inside the device to ensure that the equipment operates under a safe pressure. The gas sensor detects the gas components adsorbed by the zeolite molecular sieve and evaluates its adsorption performance and safety status. The spectrum sensor analyzes the changes in the crystal structure of the zeolite molecular sieve to determine whether its physical and chemical properties have degraded.

[0012] The data processing unit includes a processor and memory. The processor is responsible for receiving data from each sensor, analyzing and processing it, and the memory stores historical detection data and set safety thresholds for subsequent analysis and reference.

[0013] The display and control interface includes a display screen and a control panel. The display screen displays the test results, status information and alarm information in real time for the operator to observe. The control panel allows the operator to set parameters, view historical records and adjust the equipment working mode.

[0014] The alarm system includes sound and light signal emitters. When an abnormal situation is detected, the sound and light signal emitters will alert the operator through sound and light alarms to ensure timely measures are taken;

[0015] The power module provides stable power to each component of the safety detector to ensure normal operation;

[0016] The working principle of the safety detector body is to monitor the temperature, pressure and gas composition of the zeolite molecular sieve in real time through the sensor module. The sensor transmits the collected data to the data processing unit. The processor analyzes the data according to the preset algorithm and compares it with the safety threshold. The spectral sensor analyzes the crystal structure changes of the zeolite molecular sieve to determine whether its physical and chemical properties have degraded. The safety detector body is existing technology and will not be described in detail here.

[0017] A driving assembly is provided at the top of the base and near the left side to ensure smooth removal and placement of the zeolite molecular sieve. The driving assembly includes two first fixed vertical plates arranged symmetrically in front and back. A screw is rotatably connected between the two first fixed vertical plates and near the left end. The driving assembly is used to drive the screw to rotate, thereby realizing the movement of the entire removal and placement assembly.

[0018] A pick-and-place assembly is provided on the top of the base near the right side, and the pick-and-place assembly includes a movable seat. A connecting plate is provided on the left side of the movable seat near the rear end. The connecting plate is threadedly connected to the outer side of the screw rod. The screw rod drives the movement of the connecting plate by rotation, thereby controlling the forward and backward movement of the movable seat, so that the annular hollow box can overflow from the detection cavity of the safety detector body, thereby facilitating the staff to take out the zeolite molecular sieve after detection;

[0019] The top of the movable seat is provided with four rectangular mounting slots arranged in a circular array. Each of the four rectangular mounting slots is provided with a fan. The fan is connected to an external power supply to generate an upward airflow, thereby cooling the high-temperature zeolite molecular sieve in the annular hollow box, which is convenient for staff to remove the zeolite molecular sieve after testing.

[0020] The front side of the movable seat is provided with a cover plate, and the rear side of the cover plate is provided with three U-shaped brackets which are equidistantly arranged up and down. L-shaped support plates are hung on the three U-shaped brackets. The cooperation of the L-shaped support plates and the U-shaped brackets can facilitate the staff to disassemble and assemble the annular hollow box. The rear ends of the three L-shaped support plates are provided with annular hollow boxes. The three annular hollow boxes can effectively distribute the zeolite molecular sieves evenly, so that multiple zeolite molecular sieves are evenly distributed. An operating port for the annular hollow box to pass through is opened on the front side of the safety detector body and near the right side, and the cover plate can close the operating port.

[0021] Preferably, vertical electromagnets are embedded in the front side of the safety detector body and near the left and right sides of the operating port, and horizontal electromagnets are embedded in the front side of the safety detector body and near the upper and lower sides of the operating port, which are used to be adsorbed and connected with the frame-shaped iron sheet during the detection process, provide a stable fixing effect, and ensure the sealing of the operating port.

[0022] Preferably, a frame-shaped iron sheet is embedded in the rear side of the cover plate. When the vertical electromagnet and the horizontal electromagnet are energized, the vertical electromagnet and the horizontal electromagnet are both adsorbed and connected to the frame-shaped iron sheet.

[0023] Preferably, a positioning rod is provided between the two first fixed vertical plates and near the right end, and the connecting plate is slidably connected to the outer side of the positioning rod to improve the stability of the connecting plate.

[0024] Preferably, the drive assembly also includes a second fixed vertical plate, which is located near the left side of the first fixed vertical plate at the rear. A servo motor is provided on the left side of the second fixed vertical plate, and the servo motor works with an external power supply. The output shaft of the servo motor passes through the left side of the second fixed vertical plate and is coaxially connected to the active bevel gear, and the active bevel gear is driven to rotate by the servo motor.

[0025] Preferably, a driven bevel gear is provided on the outer wall of the screw rod near the rear end, and the driven bevel gear is meshed with the driving bevel gear for transmission. The driving bevel gear drives the driven bevel gear to rotate, thereby causing the driven bevel gear to drive the screw rod to rotate.

[0026] Preferably, a U-shaped plate is provided at the bottom of the movable seat and near the left and right sides. A plurality of rollers equidistantly arranged front to back are rotatably connected between the left and right sides of the inner wall of the U-shaped plate. The outer walls of the rollers abut against the top of the base, which is conducive to the forward and backward movement of the movable seat.

[0027] Preferably, a circular vent is provided at the bottom of the inner wall of the rectangular mounting groove to ensure that the fan can generate airflow, and a dustproof net is provided at the bottom inside the circular vent to prevent dust in the air from being sucked into the fan, thereby increasing the service life of the fan.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The zeolite molecular sieve safety detection device is designed with automated pick-up and placement components, which reduces manual operation, especially in high temperature and high pressure environments, thereby reducing the safety risks of operators and ensuring the safety of operations.

[0030] 2. The zeolite molecular sieve safety detection device, through the design of an annular hollow box, can effectively disperse the zeolite molecular sieve and make it evenly distributed, avoiding incomplete detection or missed detection or false detection caused by accumulation, thereby improving the accuracy and reliability of detection.

[0031] 3. The zeolite molecular sieve safety detection device is designed with a convenient operation port and a detachable annular hollow box. The cooperation of the L-shaped support plate and the U-shaped bracket simplifies the disassembly and assembly process of the annular hollow box, improving the convenience of operation and the maintenance efficiency of the equipment.

[0032] 4. The zeolite molecular sieve safety detection device has a fan on the top of the movable seat, which can effectively dissipate heat and reduce the temperature of the zeolite molecular sieve, ensuring the safe removal of the zeolite molecular sieve after detection and avoiding safety hazards caused by high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0034] Figure 2 This is a schematic diagram of the overall structure of the utility model in use state;

[0035] Figure 3 This is a schematic diagram of the structure of the safety detector body in the present utility model;

[0036] Figure 4 It is a partial structural diagram of the utility model;

[0037] Figure 5 For this utility model Figure 4 A schematic diagram of the structure at point A in the middle;

[0038] Figure 6 This is one of the partial structural diagrams of the pick-and-place assembly in the present utility model;

[0039] Figure 7 This is the second partial structural diagram of the pick-and-place assembly in the present utility model;

[0040] Figure 8 This is a schematic diagram of the assembly structure of the movable seat and the dustproof net in the utility model;

[0041] In the figure: 1. Base; 2. Support frame; 3. Safety detector body; 30. Operation port; 4. Drive assembly; 40. First fixed vertical plate; 41. Screw; 42. Driven bevel gear; 43. Second fixed vertical plate; 44. Servo motor; 45. Driving bevel gear; 46. Positioning rod; 5. Pick-and-place assembly; 50. Movable seat; 500. Rectangular mounting groove; 501. Circular vent; 51. Connecting plate; 52. Cover plate; 520. Frame-shaped iron sheet; 53. U-shaped bracket; 54. L-shaped support plate; 55. Annular hollow box; 56. Fan; 57. U-shaped plate; 58. Roller; 59. Dust screen; 6. Vertical electromagnet; 7. Horizontal electromagnet. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0044] See also Figures 1-8 , the utility model provides a technical solution:

[0045] A zeolite molecular sieve safety detection device includes a base 1. Support frames 2 are provided on the top and near the left and right sides of the base 1 to support the safety detector body 3 and enhance the overall structural strength of the device. The tops of the two support frames 2 jointly support the safety detector body 3. The safety detector body 3 generally consists of a sensor module, a data processing unit, a display and control interface, an alarm system, and a power module.

[0046] The sensor module includes a temperature sensor, a pressure sensor, a gas sensor, and a spectrum sensor. The temperature sensor is used to monitor the temperature of the zeolite molecular sieve in real time to ensure that it is within the safe operating range. The pressure sensor monitors the pressure changes inside the device to ensure that the equipment operates under a safe pressure. The gas sensor detects the gas components adsorbed by the zeolite molecular sieve and evaluates its adsorption performance and safety status. The spectrum sensor analyzes the changes in the crystal structure of the zeolite molecular sieve to determine whether its physical and chemical properties have degraded.

[0047] The data processing unit includes a processor and memory. The processor is responsible for receiving data from each sensor, analyzing and processing it, and the memory stores historical detection data and set safety thresholds for subsequent analysis and reference.

[0048] The display and control interface includes a display screen and a control panel. The display screen displays the test results, status information and alarm information in real time for the operator to observe. The control panel allows the operator to set parameters, view historical records and adjust the equipment working mode.

[0049] The alarm system includes sound and light signal emitters. When an abnormal situation is detected, the sound and light signal emitters will alert the operator through sound and light alarms to ensure timely measures are taken;

[0050] The power supply module provides stable power to each component of the safety detector body 3 to ensure normal operation;

[0051] The working principle of the safety detector body 3 is to monitor the temperature, pressure and gas composition of the zeolite molecular sieve in real time through the sensor module. The sensor transmits the collected data to the data processing unit. The processor analyzes the data according to the preset algorithm and compares it with the safety threshold. The spectral sensor analyzes the crystal structure changes of the zeolite molecular sieve to determine whether its physical and chemical properties have degraded. The safety detector body 3 is existing technology and will not be described in detail here.

[0052] A drive assembly 4 is provided at the top and near the left side of the base 1 to ensure smooth handling of the zeolite molecular sieve. The drive assembly 4 includes two first fixed vertical plates 40 symmetrically arranged front to back. A screw rod 41 is rotatably connected between the two first fixed vertical plates 40 and near the left end. The drive assembly 4 is used to drive the screw rod 41 to rotate, thereby realizing the movement of the entire handling assembly 5.

[0053] A pick-and-place assembly 5 is provided at the top and near the right side of the base 1. The pick-and-place assembly 5 includes a movable seat 50. A connecting plate 51 is provided on the left side and near the rear end of the movable seat 50. The connecting plate 51 is threadedly connected to the outer side of the screw rod 41. The screw rod 41 drives the movement of the connecting plate 51 by rotation, thereby controlling the forward and backward movement of the movable seat 50, so that the annular hollow box 55 can overflow from the detection cavity of the safety detector body 3, thereby facilitating the staff to remove the zeolite molecular sieve after detection;

[0054] The top of the movable seat 50 is provided with four rectangular mounting grooves 500 arranged in a circular array. Each of the four rectangular mounting grooves 500 is provided with a fan 56. The fan 56 is connected to an external power source to generate an upward airflow, thereby cooling the high-temperature zeolite molecular sieve in the annular hollow box 55, making it easier for staff to remove the zeolite molecular sieve after testing.

[0055] A cover plate 52 is provided on the front side of the movable seat 50, and three U-shaped brackets 53 are arranged equidistantly up and down on the rear side of the cover plate 52. L-shaped support plates 54 are hung on the three U-shaped brackets 53. The cooperation of the L-shaped support plates 54 and the U-shaped brackets 53 can facilitate the staff to disassemble and assemble the annular hollow box 55. The rear ends of the three L-shaped support plates 54 are provided with annular hollow boxes 55. The three annular hollow boxes 55 can effectively distribute the zeolite molecular sieves evenly, so that multiple zeolite molecular sieves are evenly distributed. An operating port 30 for the annular hollow box 55 to pass through is opened on the front side of the safety detector body 3 and near the right side, and the cover plate 52 can close the operating port 30.

[0056] In this embodiment, vertical electromagnets 6 are embedded in the front side of the safety detector body 3 and near the left and right sides of the operating port 30, and horizontal electromagnets 7 are embedded in the front side of the safety detector body 3 and near the upper and lower sides of the operating port 30, which are used to be adsorbed and connected with the frame-shaped iron sheet 520 during the detection process, provide a stable fixing effect, and ensure the sealing of the operating port 30.

[0057] Specifically, a frame-shaped iron sheet 520 is embedded in the rear side of the cover plate 52 . When the vertical electromagnet 6 and the horizontal electromagnet 7 are energized, the vertical electromagnet 6 and the horizontal electromagnet 7 are both adsorbed and connected to the frame-shaped iron sheet 520 .

[0058] Furthermore, a positioning rod 46 is provided between the two first fixed vertical plates 40 and near the right end, and the connecting plate 51 is slidably connected to the outer side of the positioning rod 46 to improve the stability of the connecting plate 51.

[0059] Furthermore, the drive assembly 4 also includes a second fixed vertical plate 43, which is located near the left side of the first fixed vertical plate 40 at the rear. A servo motor 44 is provided on the left side of the second fixed vertical plate 43, and the servo motor 44 works with an external power supply. The fan 56 and the controller of the servo motor 44 are located on the front side of the safety detector body 3. The output shaft of the servo motor 44 passes through the left side of the second fixed vertical plate 43 and is coaxially connected to the active bevel gear 45, and the active bevel gear 45 is driven to rotate by the servo motor 44.

[0060] Furthermore, a driven bevel gear 42 is provided on the outer wall of the screw rod 41 near the rear end. The driven bevel gear 42 is meshed with the driving bevel gear 45 for transmission. The driving bevel gear 45 drives the driven bevel gear 42 to rotate, thereby causing the driven bevel gear 42 to drive the screw rod 41 to rotate.

[0061] Furthermore, a U-shaped plate 57 is provided at the bottom of the movable seat 50 and near the left and right sides. A plurality of rollers 58 arranged equidistantly front to back are rotatably connected between the left and right sides of the inner wall of the U-shaped plate 57. The outer wall of the roller 58 abuts against the top of the base 1, which is conducive to the forward and backward movement of the movable seat 50.

[0062] Furthermore, a circular vent 501 is provided at the bottom of the inner wall of the rectangular mounting groove 500 to ensure that the fan 56 can generate airflow. A dustproof net 59 is provided at the bottom inside the circular vent 501 to prevent dust in the air from being sucked into the fan 56, thereby improving the service life of the fan 56.

[0063] When the zeolite molecular sieve safety detection device of this embodiment is in use, the servo motor 44 is controlled to rotate forward, so that the servo motor 44 drives the screw rod 41 to rotate, and the screw rod 41 drives the connecting plate 51 to move forward, and the connecting plate 51 drives the movable seat 50 to move forward, so that the multiple annular hollow boxes 55 are removed from the safety detector body 3, and then the staff evenly distributes the zeolite molecular sieves to be detected in the annular hollow boxes 55 to ensure that the multiple zeolite molecular sieves are evenly distributed to avoid accumulation, and then the annular hollow boxes 55 loaded with molecular sieves are moved into the detector cavity through the pick-and-place assembly 5. Specifically, the servo motor 44 is reversed, and the screw rod 41 drives the connecting plate 51 to move backward, And make multiple annular hollow boxes 55 pass through the operation port 30 into the detector cavity of the safety detector body 3. After the detection is completed, start the servo motor 44 to rotate forward, and move the annular hollow box 55 out of the safety detector body 3. The fan 56 will automatically work to generate an upward airflow to cool the high-temperature molecular sieve, ensuring that the molecular sieve is cooled to a safe range. Finally, the cooled zeolite molecular sieve can be safely taken out. The operator can analyze the status of the molecular sieve according to the test results and perform subsequent processing. Use the U-shaped bracket 53 and the L-shaped support plate 54 to disassemble the annular hollow box 55 so that the staff can take out the zeolite molecular sieve, effectively avoiding burns to the staff's hands.

[0064] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A zeolite molecular sieve safety detection device, comprising a base (1), characterized in that: A support frame (2) is provided at the top of the base (1) and near the left and right sides. The tops of the two support frames (2) jointly support the safety detector body (3). A driving assembly (4) is provided at the top of the base (1) and near the left side. The driving assembly (4) includes two first fixed vertical plates (40) arranged symmetrically in front and back. A screw rod (41) is rotatably connected between the two first fixed vertical plates (40) and near the left end. A pick-and-place assembly (5) is provided at the top of the base (1) and near the right side. The pick-and-place assembly (5) includes a movable seat (50). A connecting plate (51) is provided on the left side of the movable seat (50) and near the rear end. The plate (51) is threadedly connected to the outer side of the screw rod (41), and four rectangular mounting grooves (500) arranged in a circular array are provided on the top of the movable seat (50), and fans (56) are provided in the four rectangular mounting grooves (500). The front side of the movable seat (50) is provided with a cover plate (52), and the rear side of the cover plate (52) is provided with three U-shaped brackets (53) arranged equidistantly in the upper and lower directions. L-shaped support plates (54) are hung on the three U-shaped brackets (53), and the rear ends of the three L-shaped support plates (54) are provided with an annular hollow box (55). An operating port (30) for the annular hollow box (55) to pass through is provided on the front side of the safety detector body (3) and near the right side.

2. The zeolite molecular sieve safety detection device according to claim 1, characterized in that: Vertical electromagnets (6) are embedded in the front side of the safety detector body (3) and at positions close to the left and right sides of the operating port (30), and horizontal electromagnets (7) are embedded in the front side of the safety detector body (3) and at positions close to the upper and lower sides of the operating port (30).

3. The zeolite molecular sieve safety detection device according to claim 2, characterized in that: A frame-shaped iron sheet (520) is embedded in the rear side of the cover plate (52). When the vertical electromagnet (6) and the horizontal electromagnet (7) are energized, the vertical electromagnet (6) and the horizontal electromagnet (7) are adsorbed and connected to the frame-shaped iron sheet (520).

4. The zeolite molecular sieve safety detection device according to claim 1, characterized in that: A positioning rod (46) is provided between the two first fixed vertical plates (40) and near the right end, and the connecting plate (51) is slidably connected to the outside of the positioning rod (46).

5. The zeolite molecular sieve safety detection device according to claim 1, characterized in that: The drive assembly (4) further comprises a second fixed vertical plate (43), the second fixed vertical plate (43) being located near the left side of the rear first fixed vertical plate (40), a servo motor (44) being provided on the left side of the second fixed vertical plate (43), an output shaft of the servo motor (44) passing through the left side of the second fixed vertical plate (43) and being coaxially connected to a driving bevel gear (45).

6. The zeolite molecular sieve safety detection device according to claim 5, characterized in that: A driven bevel gear (42) is provided on the outer wall of the screw rod (41) near the rear end, and the driven bevel gear (42) is meshed with the driving bevel gear (45) for transmission.

7. The zeolite molecular sieve safety detection device according to claim 1, characterized in that: A U-shaped plate (57) is provided at the bottom of the movable seat (50) and near the left and right sides. A plurality of rollers (58) arranged equidistantly in front and back are rotatably connected between the left and right sides of the inner wall of the U-shaped plate (57).

8. The zeolite molecular sieve safety detection device according to claim 1, characterized in that: A circular vent (501) is provided at the bottom of the inner wall of the rectangular mounting groove (500), and a dustproof net (59) is provided at the bottom inside the circular vent (501).

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